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.