英文原文Simulink DemosSimulink is a tool for modeling, analyzing, and simulating physical and mathematical systems, including those with nonlinear elements and those that make use of continuous and discrete time.As an extension of MATLAB, Simulink adds many features specific to dynamic systems while retaining all of general purpose functionality of MATLAB.Run demos for other Simulink products you have installed. Try these demos to seewhich Simulink products might be appropriate for the work you do. Note that this is a comprehensive list of Simulink products. Your particular installation of MathWorksIn the Contents pane, for each Simulink product, see documentation Examples to viewmore sample code you can run or copy.Three-phase Three-level PWM Converter (discrete)This demonstration illustrates simulation of a 3-phase, 3-level inverterand Discrete3-phase PWM Generator. It also demonstrates harmonic analysis of PWM waveformsusing the Powergui/FFT tool.Circuit Description The system consists of two three-phase three-level PWM voltage source convertersconnected in twin configuration。The inverter feeds an AC load (1kW, 500 var 60Hz 208 Vrms) through a three-phase transformer.Harmonic filtering is performed by the transformer leakage inductance (8%) and loadcapacitance (500 var).Each of the two inverters uses the Three-Level Bridge blockwhere the specified power electronic devices are IGBT/Diode pairs.Each arm consistsof 4IGBTs, 4 antiparallel diodes, and 2 neutral clamping diodes.The inverter iscontrolled in open loop. Pulses are generated by the Discrete 3-Phase Discrete PWMGenerator block. This block is available in theExtras/Discrete Control Blocks library.This PWM generator or modulator can be used to generate pulses for 3-phase, 2-level,or 3-level converters usingone bridge or two bridges (twin configuration). In thisdemo, the PWM modulator generates two sets of 12 pulses (1 set per inverter) at P1and P2 outputs. Open the Discrete 3-phase PWM Generator menu. Notice that thegenerator can operate either in synchronized or un-synchronized mode.When operating in synchronized mode, the carrier triangular signal is synchronized ona PLL reference angle connected to input wt.In synchronized mode, the carrier chopping frequency is specified by the switching ratio as a multiple of the output frequency.Three sinusoidal 0.85 pu modulating signals are provided by the Discrete 3-phase Programmable Source to obtain a modulation index of 0.85.The carrier signals are synchronized on the modulating signals. in the PWM Generator block, you can instead select Un-synchronized and Internal generation of modulating signals. In such a case the magnitude (modulation index), frequency and phase angle of the output signals are specified. directly inside the PWM Generator block menu.For this example the DC bus voltage is 400V (+/- 200 V) , chopping frequency is 1080 Hz (18*60 Hz), magnitude of the three modulating signals is 0.85(corresponding to a modulation index m = 0.85) and the frequency of the three generated signals is 60 Hz.In order to allow further signal processing, signals displayed on the Scope block (sampled at simulation sampling rate of 3240 samples/ cycle)are stored in a variable named psb3phPWM3level_str (structures with time) .DemonstrationRun the simulation and observe the following three waveforms on the Scope block:Phase-neutral voltage Van_inv1 generated by inverter 1 (trace 1), phase A voltage Vaa_inverter generated by the twin inverter (trace 2) andphase-phase load voltage Vab_load (trace 3). The Van_inv1 waveform cleary demonstrates the three levels: +200 V, 0 V, and -200 V.Once the simulation is completed, open the Powergui and select FFT Analysis to display the 0 - 5000 Hz frequency spectrum of signals saved in the psb3phPWM3level_str structure. The FFT will be performed on a 2-cycle window starting at t = 0.1 - 2/60 (last 2 cycles of recording). Selelect the input labeled Vaa _inverter. Click on Display and observe the frequency spectrum of last 2 cycles.The fundamental component of Vaa_inverter and THD for the 0 - 5000 Hz frequency range are displayed above the spectrum window.Because of the forward voltage drops in the IGBTs (Vf=1 V) and diodes (Vfd=1V), the magnitude of the fundamental voltage of the inverter (335 V)is slightly lower than the theoretical value (340 V for m=0.85). As expected for a twin inverter, first harmonics occur around multiples of doubleof carrier frequency (n*2*1080 Hz +- k*60Hz). The same circuit using two-level inverters in twin configuration is available in the psb3phPWM.mdl demonstration file.Run this demo and compare the harmonic contents in the 2-level and 3-level inverter voltage for the same modulation index (m = 0.85).Harmonics occur at the same frequencies but their magnitude is approximately two times lower for a 3-level inverter.DC/DC and DC/AC PWM Converters (discrete)This demonstration illustrates use of the UniversalBridge andDiscrete PWM Pulse Generat