Modelling and Simulation: For Engineering project

Modelling and Simulation Model: A system of postulates, data and interfaces presented as a mathematical description of an entity or proceedings or state of affair. (Development of equations, constraints and logic rules) Simulation: Exercising the model and obtaining results. (Implementation of the model) Simulation has emerged as the Third methodology of exploring the truth. It would complement the theory and experimental methodology. Simulation will never replace them. Simulations are applicable in the following situations: 1. When operating conditions change e.g. temperature, pressure, etc 2. When non-controllable factors change e.g. weather, earthquake 3. Dependence of variation of critical factors e.g. fatigue, resonance may be destructive. 4. How sensitive is one factor to the changes in another? 5. Other benefits: a) Useful in design b) Study effects of constraints c) Increase understanding 6. Pitfalls: An assumption, which the owner can’t model or verbalise; so when two independent models clash, contradictory results arise Advantages of simulation Saves manpower, material Useful even if not possible by other means Saves money with fast, consistent answers Could be used for education after establishing Increased flexibility, accuracy, range of operation New results not available before Improved results due to standardization Increased understanding Explicitly stated assumptions and constraint Requirements/ skill required Computer Skill/Expertise Time for implementation Drawbacks: Modelling errors at different levels – Scientific model of reality – Mathematical model – Discrete numerical model – Application program model – Computational model Input errors: Out of range inputs can give spurious results Precision errors: Limits in the precision Phases of development of simulation model Real system to mathematical model Algorithm to solve mathematical model Implementation on a computer Validation – User with I/O – Model – Evaluations Simulation

Cryptography: An Introduction

The art of protecting information by transforming it (encrypting it) into an unreadable format, called cipher text. Only those who possess a secret key can decipher (or decrypt) the message intoplain text. Encrypted messages can sometimes be broken by cryptanalysis, also called codebreaking, although modern cryptography techniques are virtually unbreakable. As the Internet and other forms of electronic communication become more prevalent, electronic security is becoming increasingly important. Cryptography is used to protect e-mailmessages, credit card information, and corporate data. One of the most popular cryptography systems used on the Internet is Pretty Good Privacybecause it's effective and free. Cryptography systems can be broadly classified into symmetric-key systems that use a single key that both the sender and recipient have, and public-keysystems that use two keys, a public key known to everyone and a private key that only the recipient of messages uses. Cryptography is the science of writing in secret code and is an ancient art; the first documented use of cryptography in writing dates back to circa 1900 B.C. when an Egyptian scribe used non-standard hieroglyphs in an inscription. Some experts argue that cryptography appeared spontaneously sometime after writing was invented, with applications ranging from diplomatic missives to war-time battle plans. It is no surprise, then, that new forms of cryptography came soon after the widespread development of computer communications. In data and telecommunications, cryptography is necessary when communicating over any untrusted medium, which includes just about any network, particularly the Internet. Within the context of any application-to-application communication, there are some specific security requirements, including: • Authentication: The process of proving one's identity. (The primary forms of host-to-host authentication on the Internet today are name-based or address-based, both of which are notoriously weak.) • Privacy/confidentiality: Ensuring that no one can read the message except the intended receiver. • Integrity: Assuring the receiver that the received message has not been altered in any way from the original. • Non-repudiation: A mechanism to prove that the sender really sent this message. Cryptography, then, not only protects data from theft or alteration, but can also be used for user authentication. There are, in general, three types of cryptographic schemes typically used to accomplish these goals: secret key (or symmetric) cryptography, public-key (or asymmetric) cryptography, and hash functions, each of which is described below. In all cases, the initial unencrypted data is referred to as plaintext. It is encrypted into ciphertext, which will in turn (usually) be decrypted into usable plaintext. In many of the descriptions below, two communicating parties will be referred to as Alice and Bob; this is the common nomenclature in the crypto field and literature to make it easier to identify the communicating parties. If there is a third or fourth party to the communication, they will be referred to as Carol and Dave. Mallory is a malicious party, Eve is an eavesdropper, and Trent is a trusted third party. There are several ways of classifying cryptographic algorithms. For purposes of this paper, they will be categorized based on the number of keys that are employed for encryption and decryption, and further defined by their application and use. The three types of algorithms that will be discussed are (Figure 1): • Secret Key Cryptography (SKC): Uses a single key for both encryption and decryption • Public Key Cryptography (PKC): Uses one key for encryption and another for decryption • Hash Functions: Uses a mathematical transformation to irreversibly "encrypt" information • So, why are there so many different types of cryptographic schemes? Why can't we do everything we need with just one? • The answer is that each scheme is optimized for some specific application(s). Hash functions, for example, are well-suited for ensuring data integrity because any change made to the contents of a message will result in the receiver calculating a different hash value than the one placed in the transmission by the sender. Since it is highly unlikely that two different messages will yield the same hash value, data integrity is ensured to a high degree of confidence. • Secret key cryptography, on the other hand, is ideally suited to encrypting messages, thus providing privacy and confidentiality. The sender can generate a session key on a per-message basis to encrypt the message; the receiver, of course, needs the same session key to decrypt the message. • Key exchange, of course, is a key application of public-key cryptography (no pun intended). Asymmetric schemes can also be used for non-repudiation and user authentication; if the receiver can obtain the session key encrypted with the sender's private key, then only this sender could have sent the message. Public-key cryptography could, theoretically, also be used to encrypt messages although this is rarely done because secret-key cryptography operates about 1000 times faster than public-key cryptography.

AC voltage controllers performance and applications

A voltage controller, also called an AC voltage controller or AC regulator is an electronic module based on either thyristors, TRIACs,SCRs or IGBTs, which converts a fixed voltage, fixed frequency alternating current (AC) electrical input supply to obtain variable voltage in output delivered to a resistive load. This varied voltage output is used for dimming street lights, varying heating temperatures in homes or industry, speed control of fans and winding machines and many other applications, in a similar fashion to an autotransformer. AC voltage controllers (ac line voltage controllers) are employed to vary the RMS value of the alternating voltage applied to a load circuit by introducing Thyristors between the load and a constant voltage ac source. The RMS value of alternating voltage applied to a load circuit is controlled by controlling the triggering angle of the Thyristors in the ac voltage controller circuits. In brief, an ac voltage controller is a type of thyristor power converter which is used to convert a fixed voltage, fixed frequency ac input supply to obtain a variable voltage ac output. The RMS value of the ac output voltage and the ac power flow to the load is controlled by varying (adjusting) the trigger angle ‘’ The ac voltage controllers are classified into two types based on the type of input ac supply applied to the circuit.  Single Phase AC Controllers.  Three Phase AC Controllers. Single phase ac controllers operate with single phase ac supply voltage of 230V RMS at 50Hz in our country. Three phase ac controllers operate with 3 phase ac supply of 400V RMS at 50Hz supply frequency. Each type of controller may be sub divided into  Uni-directional or half wave ac controller.  Bi-directional or full wave ac controller. In brief different types of ac voltage controllers are  Single phase half wave ac voltage controller (uni-directional controller).  Single phase full wave ac voltage controller (bi-directional controller).  Three phase half wave ac voltage controller (uni-directional controller).  Three phase full wave ac voltage controller (bi-directional controller). APPLICATIONS OF AC VOLTAGE CONTROLLERS  Lighting / Illumination control in ac power circuits.  Induction heating.  Industrial heating & Domestic heating.  Transformers tap changing (on load transformer tap changing).  Speed control of induction motors (single phase and poly phase ac induction motor control).  AC magnet controls. 4. AC VOLTAGE CONTROL TECHNIQUES There are two different types of thyristor control used in practice to control the ac power flow  Phase control  On-Off control These are the two ac output voltage control techniques. In On-Off control technique Thyristors are used as switches to connect the load circuit to the ac supply (source) for a few cycles of the input ac supply and then to disconnect it for few input cycles. The Thyristors thus act as a high speed contactor (or high speed ac switch). 4.1 PHASE CONTROL TECHNIQUE In phase control the Thyristors are used as switches to connect the load circuit to the input ac supply, for a part of every input cycle. That is the ac supply voltage is chopped using Thyristors during a part of each input cycle. The thyristor switch is turned on for a part of every half cycle, so that input supply voltage appears across the load and then turned off during the remaining part of input half cycle to disconnect the ac supply from the load. By controlling the phase angle or the trigger angle ‘’ (delay angle), the output RMS voltage across the load can be controlled. The trigger delay angle ‘’ is defined as the phase angle (the value of t) at which the thyristor turns on and the load current begins to flow. Thyristor ac voltage controllers use ac line commutation or ac phase commutation. Thyristors in ac voltage controllers are line commutated (phase commutated) since the input supply is ac. When the input ac voltage reverses and becomes negative during the negative half cycle the current flowing through the conducting thyristor decreases and falls to zero. Thus the ON thyristor naturally turns off, when the device current falls to zero. Phase control Thyristors which are relatively inexpensive, converter grade Thyristors which are slower than fast switching inverter grade Thyristors are normally used. For applications up to 400Hz, if Triacs are available to meet the voltage and current ratings of a particular application, Triacs are more commonly used. Due to ac line commutation or natural commutation, there is no need of extra commutation circuitry or components and the circuits for ac voltage controllers are very simple. Due to the nature of the output waveforms, the analysis, derivations of expressions for performance parameters are not simple, especially for the phase controlled ac voltage controllers with RL load. But however most of the practical loads are of the RL type and hence RL load should be considered in the analysis and design of ac voltage controller circuits. PRINCIPLE OF ON-OFF CONTROL TECHNIQUE (INTEGRAL CYCLE CONTROL) The basic principle of on-off control technique is explained with reference to a single phase full wave ac voltage controller circuit shown below. The thyristor switches and are turned on by applying appropriate gate trigger pulses to connect the input ac supply to the load for ‘n’ number of input cycles during the time interval . The thyristor switches and are turned off by blocking the gate trigger pulses for ‘m’ number of input cycles during the time interval . The ac controller ON time usually consists of an integral number of input cycles. Referring to the waveforms of ON-OFF control technique in the above diagram, Two input cycles. Thyristors are turned ON during for two input cycles. One input cycle. Thyristors are turned OFF during for one input cycle Thyristors are turned ON precisely at the zero voltage crossings of the input supply. The thyristor is turned on at the beginning of each positive half cycle by applying the gate trigger pulses to as shown, during the ON time . The load current flows in the positive direction, which is the downward direction as shown in the circuit diagram when conducts. The thyristor is turned on at the beginning of each negative half cycle, by applying gating signal to the gate of , during . The load current flows in the reverse direction, which is the upward direction when conducts. Thus we obtain a bi-directional load current flow (alternating load current flow) in a ac voltage controller circuit, by triggering the thyristors alternately. This type of control is used in applications which have high mechanical inertia and high thermal time constant (Industrial heating and speed control of ac motors). Due to zero voltage and zero current switching of Thyristors, the harmonics generated by switching actions are reduced.

Engineering projects: Research and consultancy for programming, Physical modelling and simulation, Report publishing

MATLAB® is a high-performance technical computing language. It has an incredibly rich variety of functions and is often referred to as the Bible due to its vast programming capabilities. In MATLAB, computation, visualization, and programming are integrated such that the data can be expressed in a familiar mathematical notation. Evolved over many years with constant inputs from various users, it is now being widely used as a programming language for scientific and technical computation. One can perform powerful operations in MATLAB by using simple commands. Hence, writing programs in MATLAB is easier compared to other high-level languages such as FORTRAN or C. Users can even build their own set of functions for a particular application. It is an interactive system in which the basic data element is an array. MATLAB is used as a standard tool in various introductory and advanced courses of almost all streams of engineering. It is used as a tool for analysis, modeling and simulation, and for high productive research and development activities. It can be used for various functions such as mathematical computation, algorithm development, data acquisition, modeling, simulation, prototyping, data analysis, exploration, visualization, and engineering graphics development as well as building graphical user interface. SIMULINK is a software package for modeling, simulating, and analysing dynamic systems. MATLAB and SIMULINK are integrated and one can simulate, analyse, or revise the models in either environment. MATLAB also features a family of add-on application-specific features called toolboxes in SIMULINK. These toolboxes can be used for modeling and simulation of specialized technology in a real-time environment. This book attempts to train engineering students of different streams to use the functions and toolboxes of MATLAB and SIMULINK for the study, design, and analysis of different electrical circuits and systems. All these toolboxes can be used to build a real-time prototype of the system. Here you will directly speak to the expert, find a solution to your need or problem and save your valuable time and effort for future end-overs. Genuine advice and consultancy regarding an engineering project is provided here on reasonable consultant charges. The expert himself has vast experience of 15 years and has executed more than 500+ projects at various international universities as a professional.Also for some selected projects report can also be provided on reasonable charges on request.

Geothermal Energy: A brief Overview

Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma. Almost everywhere, the shallow ground or upper 10 feet of the Earth's surface maintains a nearly constant temperature between 50° and 60°F (10° and 16°C). Geothermal heat pumps can tap into this resource to heat and cool buildings. A geothermal heat pump system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow ground near the building. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger. The heat removed from the indoor air during the summer can also be used to provide a free source of hot water. In the United States, most geothermal reservoirs of hot water are located in the western states, Alaska, and Hawaii. Wells can be drilled into underground reservoirs for the generation of electricity. Some geothermal power plants use the steam from a reservoir to power a turbine/generator, while others use the hot water to boil a working fluid that vaporizes and then turns a turbine. Hot water near the surface of Earth can be used directly for heat. Direct-use applications include heating buildings, growing plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes such as pasteurizing milk. Hot dry rock resources occur at depths of 3 to 5 miles everywhere beneath the Earth's surface and at lesser depths in certain areas. Access to these resources involves injecting cold water down one well, circulating it through hot fractured rock, and drawing off the heated water from another well. Currently, there are no commercial applications of this technology. Existing technology also does not yet allow recovery of heat directly from magma, the very deep and most powerful resource of geothermal energy. Most power plants need steam to generate electricity. The steam rotates a turbine that activates a generator, which produces electricity. Many power plants still use fossil fuels to boil water for steam. Geothermal power plants, however, use steam produced from reservoirs of hot water found a couple of miles or more below the Earth's surface. There are three types of geothermal power plants:dry steam, flash steam, and binary cycle. Dry steam power plants draw from underground resources of steam. The steam is piped directly from underground wells to the power plant, where it is directed into a turbine/generator unit. There are only two known underground resources of steam in the United States: The Geysers in northern California and Yellowstone National Park in Wyoming, where there's a well-known geyser called Old Faithful. Since Yellowstone is protected from development, the only dry steam plants in the country are at The Geysers. Flash steam power plants are the most common. They use geothermal reservoirs of water with temperatures greater than 360°F (182°C). This very hot water flows up through wells in the ground under its own pressure. As it flows upward, the pressure decreases and some of the hot water boils into steam. The steam is then separated from the water and used to power a turbine/generator. Any leftover water and condensed steam are injected back into the reservoir, making this a sustainable resource. Binary cycle power plants operate on water at lower temperatures of about 225°-360°F (107°-182°C). These plants use the heat from the hot water to boil a working fluid, usually an organic compound with a low boiling point. The working fluid is vaporized in a heat exchanger and used to turn a turbine. The water is then injected back into the ground to be reheated. The water and the working fluid are kept separated during the whole process, so there are little or no air emissions. Small-scale geothermal power plants (under 5 megawatts) have the potential for widespread application in rural areas, possibly even as distributed energy resources. Distributed energy resources refer to a variety of small, modular power-generating technologies that can be combined to improve the operation of the electricity delivery system. When a person takes a hot bath, the heat from the water will usually warm up the entire bathroom. Geothermal reservoirs of hot water, which are found a couple of miles or more beneath the Earth's surface, can also be used to provide heat directly. This is called the direct use of geothermal energy. Geothermal direct use dates back thousands of years, when people began using hot springs for bathing, cooking food, and loosening feathers and skin from game. Today, hot springs are still used as spas. But there are now more sophisticated ways of using this geothermal resource. In modern direct-use systems, a well is drilled into a geothermal reservoir to provide a steady stream of hot water. The water is brought up through the well, and a mechanical system - piping, a heat exchanger, and controls - delivers the heat directly for its intended use. A disposal system then either injects the cooled water underground or disposes of it on the surface. Geothermal hot water can be used for many applications that require heat. Its current uses include heating buildings (either individually or whole towns), raising plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes, such as pasteurizing milk. With some applications, researchers are exploring ways to effectively use the geothermal fluid for generating electricity as well. The shallow ground, the upper 10 feet of the Earth, maintains a nearly constant temperature between 50° and 60°F (10°-16°C). Like a cave, this ground temperature is warmer than the air above it in the winter and cooler than the air in the summer. Geothermal heat pumps take advantage of this resource to heat and cool buildings. Geothermal heat pump systems consist of basically three parts: the ground heat exchanger, the heat pump unit, and the air delivery system (ductwork). The heat exchanger is basically a system of pipes called a loop, which is buried in the shallow ground near the building. A fluid (usually water or a mixture of water and antifreeze) circulates through the pipes to absorb or relinquish heat within the ground. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger. The heat removed from the indoor air during the summer can also be used to heat water, providing a free source of hot water. Geothermal heat pumps use much less energy than conventional heating systems, since they draw heat from the ground. They are also more efficient when cooling your home. Not only does this save energy and money, it reduces air pollution.

Design of Three phase to DC zener regulated supply for DC battery charging

Description The Zener diode block modeled in this example presents a practical implementation that uses parameters commonly provided on datasheets. These parameters are (1) Zener Voltage Vz (2) Dynamic Impedance Zzt (3) Knee Impedance Zzk (4) Max Continuous Current Izm (5) Forward Voltage Drop Vf (6) On Resistance Ron This block can effectively model three regions of operation of the zener diode I-V characteristics - forward-biased, reverse-biased before breakdown and reverse-biased after breakdown. Beyond the maximum reverse continuous current Izm, the zener is assumed to burn up and is treated as an open circuit. The implementation of the zener diode can be seen by looking under the mask of the block. Zener diodes are commonly employed in applications as voltage regulators. The circuit shows an AC source fed to a step-down transformer. The output of the transformer is then rectified using a diode bridge and smoothened using a capacitive filter. The zener diode then acts to regulate the output voltage to the zener voltage 10V. The input current into the zener is limited by the resistor Rlimit to permissible values. The programmable voltage source is setup to increase its output voltage at 0.1s. As the source output increases, so does the voltage applied at the input of the zener. However, the zener can regulate the output only as long as its input current is below the maximum specified value. This current increases as we increase the source voltage and the zener ultimately fails at about 0.112s. With the zener acting as an open-circuit at fault, voltage regulation is lost and the output of the capacitive filter gets applied to the load. Result:

Modelling of Electrical components in Simpower system

Advantages of MATLAB modelling: • Libraries of application-specific models, including models of common AC and DC electric drives, flexible AC transmission systems (FACTS), and renewable energy systems • Discretization and phasor simulation modes for faster model execution • Ideal switching algorithm for accelerated simulation of power electronic devices • Analysis methods for obtaining state-space representations of circuits and computing load flow for machines • Basic models for developing key electrical technologies • Ability to extend component libraries using the Simscape language • Support for C-code generation SimPowerSystems model (left) of an asynchronous motor and diesel-generator uninterruptible power supply (UPS). The Simulink scope (right) shows stator currents and speed of the asynchronous machine.

SimPowerSystems supports the development of complex, self-contained power systems, such as those in automobiles, aircraft, manufacturing plants, and power utility applications. The models you create support your entire development process, including hardware-in-the-loop simulations. Modeling Electrical Power Systems SimPowerSystems provides libraries for modeling electric machines, transformers, and power converters. You can connect components, such as generators, transmission lines, breakers, and motors, to model electrical power systems. Application-specific libraries are also provided, enabling you to model electric drives, aircraft power networks, and renewable energy systems. Connecting these systems with control systems modeled in Simulink lets you test integrated electrical power systems in a single environment. In addition to the traditional input-output or signal flow connections used in Simulink, SimPowerSystems uses physical connections that permit the flow of power in any direction. Models of electrical power systems built using physical connections (or acausal models) closely resemble the network they represent, and are easy to understand and share. You can define your three-phase connections using individual connections for each phase, enabling you to perform tests such as injecting a single-line-to-ground fault. You can also create single-line diagrams, where the three phases are represented by a single line, making the diagram easy to read. SimPowerSystems components are parameterized using the per-unit system, which is widely used in the power system industry and simplifies the parameterization and analysis of your system.

SimPowerSystems model (left) of a permanent magnet synchronous motor and inverter sized for use in a typical hybrid vehicle. The model includes the electrical connections (single-phase and three-phase) and signal flow connections, and the scope (right) shows the stator currents in the PMSM. Creating Custom Components You can add components from other physical modeling products to your SimPowerSystems model. The Foundation libraries in Simscape contain blocks in hydraulic, thermal, magnetic, and other physical domains. Integrating these domains into your SimPowerSystems model using physical connections helps you model other aspects of your system in a single environment. The Simscape language is an object-oriented language based on MATLAB that enables you to create your own physical modeling components and libraries. You can define custom components complete with parameterization, physical connections, and equations represented as acausal implicit differential algebraic equations (DAEs). Within your component’s Simscape language file, you can use MATLAB to analyze parameter values, perform preliminary computations, and initialize system variables. The Simulink block and dialog box for your custom component are automatically created from the file.

Using the Simscape language, you can control exactly which effects are captured in the models of your physical components. This approach enables you to balance the tradeoff between model fidelity and simulation speed. Custom Simscape implementation of a permanent magnet synchronous motor, used as a generator. The MATLAB editor shows Simscape language source code of the electrical and mechanical equations, and the scope shows the three-phase AC currents and DC current at the load. Simulating Models You can simulate your SimPowerSystems models using any of three solution methods for your power system network, as well as an ideal switching algorithm that improves simulation performance for systems with high-frequency switching. Selecting SimPowerSystems Simulation Mode Choose simulation mode (continuous, discrete, or phasor) using SimPowerSystems™. Analyze transient effects and magnitudes of circuit voltages. Continuous methods perform highly accurate simulations of power system models, varying the step size to capture the dynamics of your system. Discrete methods enable you to control the precision of your simulation by selecting the size of the time step. Phasor simulation replaces the differential equations representing the network with a set of algebraic equations at a fixed frequency, making it possible to do transient stability studies of systems with multiple machines. The ideal switching algorithm in SimPowerSystems enables fast and accurate simulation of systems containing power electronic devices. This algorithm uses an improved method of calculating the state-space representation of the system instead of relying on current sources with high-impedance snubbers to model power electronic devices. This method gives you greater flexibility in selecting a solver and results in shorter simulation times. SimPowerSystems interface for selecting simulation options. Continuous, discrete, and phasor simulation modes are supported, with the option of enabling an ideal switching algorithm for faster simulation. Analyzing Models SimPowerSystems provides tools for analyzing models, visualizing simulation results, and calculating advanced block parameters, enabling you to: • Display steady-state voltage and currents • Display and modify initial state values • Perform load flows and machine initialization • Perform harmonic analysis • Display impedance vs. frequency measurements The load flow computational engine computes initial currents of synchronous and asynchronous machines. You specify the desired steady-state machine conditions in your circuit, and SimPowerSystems computes the load flow. The resulting rotor position, initial currents, and internal fluxes are automatically entered into the parameters for the machines. SimPowerSystems lets you analyze the electrical network topology and compute the equivalent state-space model of your circuit without running a simulation. You can link the state-space model to the Linear System Analysis app in Control System Toolbox™ to obtain time-domain and frequency-domain responses. The SimPowerSystems FFT analysis tool. The frequency spectrum of a voltage waveform is displayed, and power quality is measured by calculating total harmonic distortion.

Simulating AC to DC to AC PWM converter

A 60 Hz, voltage source feeds a 50 Hz, 50 kW load through an AC-DC-AC converter. The 600V, 60 Hz voltage obtained at secondary of the Wye/Delta transformer is first rectified by a six pulse diode bridge. The filtered DC voltage is applied to an IGBT two-level inverter generating 50 Hz. The IGBT inverter uses Pulse Width Modulation (PWM) at a 2 kHz carrier frequency. The circuit is discretized at a sample time of 2 us The load voltage is regulated at 1 pu (380 V rms) by a PI voltage regulator using abc_to_dq and dq_to_abc transfomations. The first output of the voltage regulator is a vector containing the three modulating signals used by the PMW Generator to generate the 6 IGBT pulses. The second output returns the modulation index. The Multimeter block is used to observe diode and IGBT currents. In order to allow further signal processing, signals displayed on Scope1 block (sampled at simulation sampling rate of 2us ) are stored in a variable named 'psbbridges_str' (structure with time). Simulation Start the simulation. After a transient period of approximately 50 ms, the system reaches a steady state. Observe voltage waveforms at DC bus, inverter output and load on Scope1. The harmonics generated by the inverter around multiples of 2 kHz are filtered by the LC filter. As expected the peak value of the load voltage is 537 V (380 Vrms). In steady state, the mean value of the modulation index is m = 0.80 and the mean value of the DC voltage is 778 V. The fundamental component of 50 Hz voltage buried in the chopped inverter voltage is therefore: Vab = 778 V * 0.612 * 0.80 = 381 V rms Once simulation is completed, open the Powergui and select 'FFT Analysis' to display the 0 - 7000 Hz frequency spectrum of signals saved in the 'psbbridges_str' structure. The FFT will be performed on a 2-cycle window starting at t=0.1-2/50 (last 2 cycles of recording). Select input labeled 'Vab Load' . Click on Display and observe the frequency spectrum of last 2 cycles. Notice harmonics around multiples of the 2 kHz carrier frequency. Maximum harmonic is 1.4 % of fundamental and THD is 2%. Observe diode currents on trace 1 of Scope2, showing commutation from diode 1 to diode 3. Also observe on trace 2 currents in switches 1 and 2 of the IGBT/Diode bridge (upper and lower switches connected to phase A). These two currents are complementary. A positive current indicates a current flowing in the IGBT, whereas a negative current indicates a current flowing in the antiparallel diode.

Power Electronics, converters, research and Applications: A Brief overview

Power electronics is the application of solid-state electronics for the control and conversion of electric power. It also refers to a subject of research in electronic and electrical engineering which deals with design, control, computation and integration of nonlinear, time varying energy processing electronic systems with fast dynamics. The capabilities and economy of power electronics system are determined by the active devices that are available. Their characteristics and limitations are a key element in the design of power electronics systems. Formerly, the mercury arc valve, the high-vacuum and gas-filled diode thermionic rectifiers, and triggered devices such as the thyratron and ignitron were widely used in power electronics. As the ratings of solid-state devices improved in both voltage and current-handling capacity, vacuum devices have been nearly entirely replaced by solid-state devices. Power electronic devices may be used as switches, or as amplifiers. An ideal switch is either open or closed and so dissipates no power; it withstands an applied voltage and passes no current, or passes any amount of current with no voltage drop. Semiconductor devices used as switches can approximate this ideal property and so most power electronic applications rely on switching devices on and off, which makes systems very efficient as very little power is wasted in the switch. By contrast, in the case of the amplifier, the current through the device varies continuously according to a controlled input. The voltage and current at the device terminals follow a load line, and the power dissipation inside the device is large compared with the power delivered to the load. Several attributes dictate how devices are used. Devices such as diodes conduct when a forward voltage is applied and have no external control of the start of conduction. Power devices such as silicon controlled rectifiers and thyristors (as well as the mercury valve and thyratron) allow control of the start of conduction, but rely on periodic reversal of current flow to turn them off. Devices such as gate turn-off thyristors, BJT and MOSFET transistors provide full switching control and can be turned on or off without regard to the current flow through them. Transistor devices also allow proportional amplification, but this is rarely used for systems rated more than a few hundred watts. The control input characteristics of a device also greatly affect design; sometimes the control input is at a very high voltage with respect to ground and must be driven by an isolated source. As efficiency is at a premium in a power electronic converter, the losses that a power electronic device generates should be as low as possible. Devices vary in switching speed. Some diodes and thyristors are suited for relatively slow speed and are useful for power frequency switching and control; certain thyristors are useful at a few kilohertz. Devices such as MOSFETS and BJTs can switch at tens of kilohertz up to a few megahertz in power applications, but with decreasing power levels. Vacuum tube devices dominate high power (hundreds of kilowatts) at very high frequency (hundreds or thousands of megahertz) applications. Faster switching devices minimize energy lost in the transitions from on to off and back, but may create problems with radiated electromagnetic interference. Gate drive (or equivalent) circuits must be designed to supply sufficient drive current to achieve the full switching speed possible with a device. A device without sufficient drive to switch rapidly may be destroyed by excess heating. Power electronic circuit’s process and control electrical energy, and are critical elements in many kinds of systems. The rapid evolution of technology is generating a demand for power electronics whose capabilities greatly exceed what is presently achievable. Challenges of particular importance include miniaturization and integration of power electronics, and improving their cost and dynamic performance. Miniaturization is difficult in part because the magnetic components used in most power circuits scale down poorly in size. Likewise, achieving integration and low cost is difficult because of the diverse materials and assembly methods that are required for contemporary designs. My research interest includes working to address these challenges through a combination of new technologies. One research focus is on the development of improved power passive components. Passive components such as inductors and capacitors often dominate the size and cost of power circuits, and limit their efficiency, noise attenuation, and transient performance. In one effort, we are developing means to improve the performance of passive filter components by compensating for their parasitic. These efforts have led to new integrated filter components with much better performance than conventional passives. Likewise, we are developing new types of power passive components that better scale to small sizes and high frequencies. Construction of these components using micro fabrication techniques is also being explored, with the goal of enabling integrated fabrication of power converters. A second research focus is the development of techniques to achieve greatly increased switching frequencies in power converters. Higher frequencies are desirable because they enable faster transient response and reduce passive component requirements. Moreover, at sufficiently high frequencies, batch fabrication of many circuit components may become possible, enabling higher levels of integration to be achieved. We are exploring new system architectures, circuit designs, and control methods that together enable substantial increases in operating frequency over the present state of the art. It is anticipated that the technologies under development will lead to miniaturized, highly integrated power electronics. In addition to developing fundamental power conversion technologies, we are applying them in a variety of applications. Automotive power generation and control is one such area. For example, we have investigated the application of power electronics to enhance the efficiency, power, and transient performance of automotive alternators. We have also developed dc/dc converters and other power electronics for automotive applications, with the goal of enabling improved performance, safety, and comfort in vehicles. Other areas of interest include power components and circuits for industrial, commercial, consumer, and medical applications where improved size, efficiency, and performance are of importance. Applications of power electronics range in size from a switched mode power supply in an AC adapter, battery chargers, fluorescent lamp ballasts, through variable frequency drives and DC motor drives used to operate pumps, fans, and manufacturing machinery, up to gigawatt-scale high voltage direct current power transmission systems used to interconnect electrical grids. Power electronic systems are found in virtually every electronic device. For example: • DC/DC converters are used in most mobile devices (mobile phones, PDA etc.) to maintain the voltage at a fixed value whatever the voltage level of the battery is. These converters are also used for electronic isolation and power factor correction. A power optimizer is a type of DC/DC converter developed to maximize the energy harvest from solar photovoltaic or wind turbine systems. • AC/DC converters (rectifiers) are used every time an electronic device is connected to the mains (computer, television etc.). These may simply change AC to DC or can also change the voltage level as part of their operation. • AC/AC converters are used to change either the voltage level or the frequency (international power adapters, light dimmer). In power distribution networks AC/AC converters may be used to exchange power between utility frequency 50 Hz and 60 Hz power grids. • DC/AC converters (inverters) are used primarily in UPS or renewable energy systems or emergency lighting systems. Mains power charges the

DC battery. If the mains fail, an inverter produces AC electricity at mains voltage from the DC battery. Solar inverter, both smaller string and larger central inverters, as well as solar micro-inverter are used in photovoltaic as a component of a PV system. Motor drives are found in pumps, blowers, and mill drives for textile, paper, cement and other such facilities. Drives may be used for power conversion and for motion control. For AC motors, applications include variable-frequency drives, motor soft starters and excitation systems. In hybrid electric vehicles (HEVs), power electronics are used in two formats: series hybrid and parallel hybrid. The difference between a series hybrid and a parallel hybrid is the relationship of the electric motor to the internal combustion engine (ICE). Devices used in electric vehicles consist mostly of dc/dc converters for battery charging and dc/ac converters to power the propulsion motor. Electric trains use power electronic devices to obtain power, as well as for vector control using pulse width modulation (PWM) rectifiers. The trains obtain their power from power lines. Another new usage for power electronics is in elevator systems. These systems may use thyristors, inverters, permanent magnet motors, or various hybrid systems that incorporate PWM systems and standard motors.

Solar photo voltaic power generation system

Photovoltaic (PV) technology converts one form of energy (sunlight) into another form of energy (electricity) using no moving parts, consuming no conventional fossil fuels, creating no pollution, and lasting for decades with very little maintenance. The use of a widely available and reasonably reliable fuel source the sun with no associated storage or transportation difficulties and no emissions makes this technology eminently practicable for powering remote scientific research platforms [2]. Indeed, numerous examples of successfully deployed systems are already available around the globe [7, 8]. The completely scalable nature of the technology also lends itself well to varying power requirements i.e. from the smallest autonomous research platforms to infrastructure-based systems. This technology can be limited, however, by annual fluctuations in solar insolation, especially at extreme latitudes. Based on semiconductor technology, solar cells operate on the principle that electricity will flow between two semiconductors when they are put into contact with each other and exposed to light (photons). This phenomenon, known as the Photovoltaic effect was first discovered by

Fig. 2.1 Solar cell Edmund Becquerel in 1839. Actual development of PV technology began in the 1950s and gained greater impetus through the NASA space program during the 1960s. Research continues today at national laboratories and within private industry, focusing on increasing conversion efficiencies and mass production strategies to further lower the cost of producing PV modules. Solar photovoltaic systems convert solar energy directly into electrical energy. Basic conversion device used is known as a solar photovoltaic cell or a solar cell as shown in fig. 2.1. Although other light sources may also produce photovoltaic electricity, only sunlight based PV cells are considered in this chapter. A solar cell is basically an electrical current source, driven by flux of radiation. Solar cells were first produced in 1954 and were rapidly developed to provide power for space satellites based on semiconductor electronics technology. Its terrestrial applications were considered seriously only after the oil crisis of 1973, when a real need of alternative energy source was felt globally. Efficient power utilization depends not only on efficient generation in the cell but also on the dynamic load matching in the in the external circuit. Major advantages of solar PV systems over conventional power systems are as under: 1. It converts solar energy directly into electrical energy without going through thermal mechanical link. 2. Solar PV system is reliable, modular, and durable and generally maintenance free. 3. These systems are quiet, compatible with almost all environmental, respond instantaneously to solar radiation and have an expected life span of 20 years or more. 4. It can located at the place of use i.e. onsite and hence no distribution network is required. It also suffers from some drawbacks which can be overcome by the technology in future, such as: 1. At present the cost of solar cells are high, making them economically uncompetitive with other conventional power sources. 2. The efficiency of solar cell is low. 3. As solar energy is intermittent, some kind of electrical energy storage e.g. battery is required which makes the whole system more expensive. 2.2 Components of Photovoltaic system 2.2.1 PV Panels PV panels tend to work much better in cold weather than in hot climates (except for amorphous silicon panels). Add a reflective snow surface and the output can sometimes exceed the rating for the panel. Array currents up to 20% greater than the specified output have been reported. In general, PV materials are categorized as either crystalline or thin film as shown in fig. 2.2 and they are judged on two basic factors: efficiency and economics. For remote installations where the actual space available for PV panels is often quite limited, the greater conversion efficiency of crystalline technology seems to have the advantage. It is also worth noting that the conversion efficiency of thin-film panels tends to drop off rather rapidly in the first few years of operation. Decreases of more than 25% have been reported. This performance deterioration must be taken into account when sizing the array for a multi-year project. However, there are still applications where the lighter weight and greater flexibility of the thin-film panels may be more suitable. Which PV technology is more appropriate for a given application will need to be determined on a case-by-case basis [14].

Fig. 2.2 Types of solar cells

Fig. 2.3 OFF grid Residential Solar PV system Mono-crystalline silicon panels should be utilized when a higher voltage is desirable. This would be in an instance where the DC power has to travel some distance before being utilized or stored in a battery bank as shown in fig. 2.3. These panels are also the most efficient PV technology, averaging 14% to 17%. New technology charge controllers, which allow for a higher array voltage than the battery bank voltage, somewhat obviate the advantages of the mono-crystalline panels. Polycrystalline silicon panels have efficiencies of 12% to 14% and can often be purchased at a lower cost per watt than mono-crystalline silicon panels. This type of panel sees the widest use in polar applications. Thin-film technologies include amorphous silicon, cadmium telluride, copper-indium dieseline, and others (refer fig. 2.2). Although the cost of these panels appears attractive at first, it is important to note that the efficiencies are comparatively low. The 8% to 10% efficiencies seen in new panels quickly degrade to about 3% to 6% after several months of exposure to sunlight. Furthermore, amorphous silicon and cadmium telluride modules are sensitive to a much narrower band of colors, and the winter shift to redder sunlight results in slightly poorer performance. Newer, triple-junction thin film technologies appear to have higher efficiencies and less degradation over time, but they are still subject to the same problems mentioned above, if to a lesser degree. The somewhat flexible nature of thin-film technology may make it appropriate for some applications, but in general, the higher efficiencies and more robust nature of the crystalline silicon modules make them a better choice for polar applications. Regardless of the technology employed, the researcher would be well advised to look for modules with heavy-duty aluminum frames, UL ratings, easy-to-use junction boxes, and a long warranty (20+ years). All of these are indicative of a quality unit that will withstand the rigors of the polar environment.

Fuel cell for automobiles and power generation

A fuel cell is a device that generates electricity by a chemical reaction. Every fuel cell has two electrodes, one positive and one negative, called, respectively, the anode and cathode. The reactions that produce electricity take place at the electrodes. Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes. Hydrogen is the basic fuel, but fuel cells also require oxygen. One great appeal of fuel cells is that they generate electricity with very little pollution–much of the hydrogen and oxygen used in generating electricity ultimately combine to form a harmless byproduct, namely water. One detail of terminology: a single fuel cell generates a tiny amount of direct current (DC) electricity. In practice, many fuel cells are usually assembled into a stack. Cell or stack, the principles are the same. The purpose of a fuel cell is to produce an electrical current that can be directed outside the cell to do work, such as powering an electric motor or illuminating a light bulb or a city. Because of the way electricity behaves, this current returns to the fuel cell, completing an electrical circuit. (To learn more about electricity and electric power, visit "Throw The Switch" on the Smithsonian website Powering a Generation of Change.) The chemical reactions that produce this current are the key to how a fuel cell works. There are several kinds of fuel cells, and each operates a bit differently. But in general terms, hydrogen atoms enter a fuel cell at the anode where a chemical reaction strips them of their electrons. The hydrogen atoms are now "ionized," and carry a positive electrical charge. The negatively charged electrons provide the current through wires to do work. If alternating current (AC) is needed, the DC output of the fuel cell must be routed through a conversion device called an inverter. Oxygen enters the fuel cell at the cathode and, in some cell type, it there combines with electrons returning from the electrical circuit and hydrogen ions that have traveled through the electrolyte from the anode. In other cell types the oxygen picks up electrons and then travels through the electrolyte to the anode, where it combines with hydrogen ions. The electrolyte plays a key role. It must permit only the appropriate ions to pass between the anode and cathode. If free electrons or other substances could travel through the electrolyte, they would disrupt the chemical reaction. Whether they combine at anode or cathode, together hydrogen and oxygen form water, which drains from the cell. As long as a fuel cell is supplied with hydrogen and oxygen, it will generate electricity. Even better, since fuel cells create electricity chemically, rather than by combustion, they are not subject to the thermodynamic laws that limit a conventional power plant (see "Carnot Limit" in the glossary). Therefore, fuel cells are more efficient in extracting energy from a fuel. Waste heat from some cells can also be harnessed, boosting system efficiency still further. Alkali fuel cells operate on compressed hydrogen and oxygen. They generally use a solution of potassium hydroxide (chemically, KOH) in water as their electrolyte. Efficiency is about 70 percent, and operating temperature is 150 to 200 degrees C, (about 300 to 400 degrees F). Cell output ranges from 300 watts (W) to 5 kilowatts (kW). Alkali cells were used in Apollo spacecraft to provide both electricity and drinking water. They require pure hydrogen fuel, however, and their platinum electrode catalysts are expensive. And like any container filled with liquid, they can leak. Molten Carbonate fuel cells (MCFC) use high-temperature compounds of salt (like sodium or magnesium) carbonates (chemically, CO3) as the electrolyte. Efficiency ranges from 60 to 80 percent, and operating temperature is about 650 degrees C (1,200 degrees F). Units with output up to 2 megawatts (MW) have been constructed, and designs exist for units up to 100 MW. The high temperature limits damage from carbon monoxide "poisoning" of the cell and waste heat can be recycled to make additional electricity. Their nickel electrode-catalysts are inexpensive compared to the platinum used in other cells. But the high temperature also limits the materials and safe uses of MCFCs–they would probably be too hot for home use. Also, carbonate ions from the electrolyte are used up in the reactions, making it necessary to inject carbon dioxide to compensate. Phosphoric Acid fuel cells (PAFC) use phosphoric acid as the electrolyte. Efficiency ranges from 40 to 80 percent, and operating temperature is between 150 to 200 degrees C (about 300 to 400 degrees F). Existing phosphoric acid cells have outputs up to 200 kW, and 11 MW units have been tested. PAFCs tolerate a carbon monoxide concentration of about 1.5 percent, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed. Platinum electrode-catalysts are needed, and internal parts must be able to withstand the corrosive acid. Proton Exchange Membrane (PEM) fuel cells work with a polymer electrolyte in the form of a thin, permeable sheet. Efficiency is about 40 to 50 percent, and operating temperature is about 80 degrees C (about 175 degrees F). Cell outputs generally range from 50 to 250 kW. The solid, flexible electrolyte will not leak or crack, and these cells operate at a low enough temperature to make them suitable for homes and cars. But their fuels must be purified, and a platinum catalyst is used on both sides of the membrane, raising costs. Solid Oxide fuel cells (SOFC) use a hard, ceramic compound of metal (like calcium or zirconium) oxides (chemically, O2) as electrolyte. Efficiency is about 60 percent, and operating temperatures are about 1,000 degrees C (about 1,800 degrees F). Cells output is up to 100 kW. At such high temperatures a reformer is not required to extract hydrogen from the fuel, and waste heat can be recycled to make additional electricity. However, the high temperature limits applications of SOFC units and they tend to be rather large. While solid electrolytes cannot leak, they can crack.

Multi level inverters topologies and their simulation in Matlab/Simulink

In this study, a review of cascaded H-bridge multilevel inverter topology and control schemes was conducted. Multilevel inverter topology (MLI) H-bridge cascade is implemented to reduce harmonic for high power applications. Applications of multilevel converters are able to reduce the number of harmonics contained in the system of low-voltage electrical distribution. Each topology has their own advantages and disadvantages. The cascaded H-bridge multilevel inverter topology requires only a single DC power source with both input and output, high availability, and the control of power flow in the regenerative version. The selected switching technique to control the inverter will also have an effective role on harmonic elimination while generating the ideal output voltage. Intensive studies have been performed on carrier-based, sinusoidal, space vector and sigma delta PWM methods in open loop control of inverters. The results from this study represent a beneficial basis for matching of inverter topology and the best control scheme according to different application areas. In general, increasing the switching frequency in voltage source inverters (VSIs) leads to better output voltage and current waveforms. Harmonic reduction in controlling a VSI with variable amplitude and frequency of the output voltage is important, and thus, conventional inverters which are referred as two-level inverters require increased switching frequency along with various PWM switching strategies. The multilevel fundamental switching scheme is used to control the needed power electronics switches. Also, a method is presented where switching angles are computed such that a desired fundamental sinusoidal voltage is produced and at the same time certain higher order harmonics are eliminated. The generalized multilevel inverter topology can balance each voltage level by itself regardless of the inverter control and load characteristics. The concept of multilevel converters has been introduced since 1975. The usage of these applications has become more diverse and affects a wide field of electrical engineering from a few watts to several hundred megawatts. Converting static structures that comprise mainly applications of power electronics is becoming increasingly powerful, and the technology has had to adapt to the growth of the power to convert. Multilevel inverter topologies are the Neutral-Point Clamped (NPC) inverters (or DiodeClamped inverters), the cascaded H- bridge inverters (CHB), and the Flying Capacitor (FC) inverters (or Capacitor Clamped inverters), as shown in Figure 1. In this paper, a review of multilevel inverter based on cascaded h-bridge topology and control schemes was conducted. The advantages of this multilevel approach include good power quality, good electromagnetic compatibility (EMC), low switching losses, and high voltage capability.

New Matlab course for Electrical and Electronics Engineers Duration 1 month

Matlab is widely used in all areas of applied mathematics in education and research. Matlab software is built up around vectors and matrices. This makes the software particularly useful for linear algebra but it is also a great tool for solving algebraic and differential equations and for numerical integration. Matlab has powerful graphic tools and can produce nice pictures in both 2D and 3D. Matlab also has some tool boxes useful for signal processing, image processing, etc. This course of 1 month duration is exclusively tailor made to meet the requirement os electrical, electronics and power system engineers. It is described the application the MatLabTM software in analysis and simulations of transient phenomena in transmission lines. Using the characteristics of this software, transmission lines are easily modeled as a mono-phase circuit. Transient simulations are also easily carried out. For these applications, it is used basic and simple tools of the MatLabTM software. So, this software improves the analysis of the proposed problem, because it is possible to obtain several types of the graphic results that are not available in the specific programs for transient analysis like the EMTP programs. So, it is possible to analyze the resistance and inductance values that depend on the frequency when it is considered detailed transmission line models. It is possible to analyze the application of different numeric methods for solving the differential state equations by numeric integration routines. On the other hand, with a simple model of the transmission lines and the MatLabTM software, it is possible to develop a routine that is used by undergraduate students, making easy the learning about important concepts as wave propagation, transient phenomena and transmission lines. This routine can be modified, introducing elements that are able to consider the frequency influence in the transmission line parameters. These parameters have their characteristics distributed along the line and this is considered in the mentioned routine.

Release Notes for SimPowerSystems - MATLAB & Simulink - MathWorks India

Release Notes for SimPowerSystems - MATLAB & Simulink - MathWorks India

R2014a

New Features, Bug Fixes, Compatibility Considerations

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New names for SimPowerSystems technologies

SimPowerSystems™ Version 6.1 introduces new names for the SimPowerSystems Second and Third Generation technologies. SimPowerSystems Simscape™ Components is the new name for the Third Generation technology. SimPowerSystems Specialized Technology is the new name for the Second Generation technology.

Note:   The terms Simscape Components and Specialized Technology refer to the SimPowerSystems technology used. A SimPowerSystems version can contain one or both technologies.

For more information, see Comparison of Simscape Components and Specialized Technology.

Simscape Components

Time-Based Fault and Enabled Fault blocks

The Time-Based Fault block and the Enabled Fault block model any permutation of a single-phase, two-phase, or three-phase grounded or ungrounded fault. You specify the fault permutation and the values for resistance and conductance.

The Time-Based Fault block is activated and deactivated during simulation according to time-based parameters that you specify. The Enabled Fault block is activated when the input signal exceeds a threshold value that you specify. It is deactivated when the signal is equal to or less than the threshold value.

Saturation option for Synchronous Machine models

You can now simulate magnetic saturation on these synchronous machine blocks:

• Synchronous Machine Round Rotor (fundamental)
• Synchronous Machine Round Rotor (standard)
• Synchronous Machine Salient Pole (fundamental)
• Synchronous Machine Salient Pole (standard)

These blocks have a new Saturation tab, which contains the Magnetic saturation representation parameter. When you specify the field current and air-gap voltage per-unit saturation data, the block generates a per-unit air-gap voltage versus field current open-circuit lookup table. The block then uses the lookup table data to calculate a saturation factor.

Harmonic analysis functions

There are three new functions for performing harmonic analysis:

• pe_getHarmonics
• pe_calculateThdPercent
• pe_plotHarmonics

The pe_getHarmonics function returns the harmonic orders, magnitude, and fundamental frequency when you input a Simscape logging node variable.

To run the pe_getHarmonics function, at the MATLAB^® command prompt, type:

pe_getHarmonics( logging_node )

where logging_node is the Simscape logging node variable.

The pe_calculateThdPercent function returns the Total Harmonic Distortion (THD) percentage when you use the harmonic order and the harmonic magnitude as input arguments.

To run the pe_calculateThdPercent function, at the MATLAB command prompt, type:

pe_calculateThdPercent( harmonicOrder, harmonicMagnitude )

where

• harmonicOrder is a vector of harmonic orders.
• harmonicMagnitude is a vector of harmonic magnitudes.

The pe_plotHarmonics function plots the harmonic data when you input a Simscape logging node variable.

To run the pe_plotHarmonics function, at the MATLAB command prompt, type:

pe_plotHarmonics( logging_node )

where logging_node is the Simscape logging node variable.

The Harmonic Analysis of a Three-Phase Rectifier example shows you how to use the three functions.

Primary and secondary winding blocks with new variables tab 

The Primary Winding and Secondary Winding blocks now contain a Variables tab, which allows you to specify target value and priority for a new initialization process.

For more information see the Simscape Release Notes item, Variables tab for specifying target value and priority for new initialization process

Compatibility Considerations 

In previous releases, the Primary Winding and Secondary Winding blocks contained parameters that let you specify an initial value for some internal block variables at the start of simulation. These parameters have now been removed. The following table lists the initialization parameters that have been removed from block dialogs and the names of the corresponding block variables:

Block Name	Parameter Name	Variable Name
Primary Winding	Leakage inductance initial current Magnetization inductance initial current Initial magnetic flux	Leakage inductance current Magnetization inductance current Magnetic flux
Secondary Winding	Leakage inductance initial current Initial magnetic flux	Leakage inductance current Magnetic flux

Legacy models using these blocks are affected by this change. If a block used the initialization parameter, then, once you open the model in the current release, this parameter value is no longer visible and is not automatically mapped to the corresponding variable value. The simulation results will only stay the same if you set the target value of the variable to be that of the original parameter and set the parameter priority to High.

Specialized Technology

Aircraft fuel cell hybrid emergency power system example

The Energy Management Systems for a Hybrid Electric Source (Application for a More Electric Aircraft) example illustrates a simulation model of a fuel-cell-based emergency power system for More Electric Aircraft (MEA). In MEA, as the landing-gear and flight-control systems become more electrically driven, the peak electrical load seen by the emergency power system increases. This increased load puts conventional ram air turbine (RAT) and air-driven generator (ADG) emergency power systems, which exhibit near-zero power production at lower speeds, at risk for overloading. This example presents an alternative emergency power system based on fuel cells, lithium-ion batteries, and supercapacitors that is more capable of handling the increased electrical load.

Text labels for Machine Block Bus output signals

In previous releases, you could only use alphanumeric signal names to identify bus labels on these SimPowerSystems machine blocks:

• Asynchronous Machine SI Units
• Asynchronous Machine pu Units
• DC Machine
• Permanent Magnet Synchronous Machine
• Simplified Synchronous Machine SI Units
• Simplified Synchronous Machine pu Units
• Single Phase Asynchronous Machine
• Synchronous Machine SI Fundamental
• Synchronous Machine pu Fundamental
• Synchronous Machine pu Standard

Machine blocks now have a Measurement output parameter that gives you the option to identify bus labels with alphanumeric signal names that are compatible with model referencing. To enable the option to convert bus signal names to valid signal names, on the machine block Configuration tab, under Measurement output, select the Use signal names to identify bus labels check box.

The Use signal names to identify bus labels check box is cleared by default.

Three-phase 3-Level Inverter with direct specification of diode and IGBT characteristics

In previous versions, the Loss Calculation in a Three-Phase 3-Level Inverter example allowed you to choose between three different pre-specified commercial (ABB^® or Fuji) components for the IGBT Type and Diode Typeparameters in the Half-bridge IGBT with Loss Calculation block dialog box. To use a value other than the prespecified commercial values, you entered your own IGBT and diode specifications via MATLAB MAT-files.

In the current version, you can enter your preferred IGBT and diode values directly to the Half-bridge IGBT with Loss Calculation block dialog box in the new IGBT and Diode tabs. You can click the Save button on either tab to save the values to MAT-files for future use. The tabs also contain a Plot Characteristics button that you can use to plot your IGBT or diode values.

The prespecified commercial (ABB or Fuji) component specifications are still available as MAT-files that you can upload by clicking the Load button on the IGBT or Diode tab.

Improved breaker block set interfaces

The dialog boxes for the breaker blocks in the Elements library have been standardized:

• Breaker
• Three-Phase Breaker
• Three-Phase Fault

power_cableparam function documentation enhancement

The power_cableparam function reference page has been expanded to include a formula for calculating