大功率变流技术Project1 SPWM Control Schemes for TwoLevel Voltage Source Inverter.docx

1、大功率变流技术Project1 SPWM Control Schemes for TwoLevel Voltage Source InverterPower Conversion SystemsSPWM Control Schemes for Two-Level Voltage Source InverterPeng Jiaqiao, 3130104084, 1056607357Abstract-Voltage source inverter has been widely used in modern industrywith a very important position.In the

2、 process of obtaining better equipment and system performance, how to change the control method and circuit parameters to reduce the THD is very important.The report can be divided in three parts.The first part, the circuit inductance, impedance, and other component parameters are designed in accord

3、ance with the requirements. The second part, by regulating different voltage amplitude ratio circuit THD changes will be observed.The third part, inject third harmonic modulation circuit to observe the relationship of the amplitude modulation ratio and circuit THD.Each time the simulation, the low h

4、armonic of the circuit will also be observed.In Part B, it is seen that the amplitude modulation ratio increases, reducing the output voltage and current THD, and increase the utilization of the bus voltage, but at the same low order harmonics also increases.In the harmonic injection plan, when the

5、third harmonic amplitude is relatively high, the output voltage and current has a smaller THD, also with low harmonic.This report describes the process and simulation results of the experiment.Index TermsSPWM, Two-Level Voltage Source Inverter, harmonic, THD, common mode voltage injection.I.Introduc

6、tionVoltage source inverter has been widely used in modern life in order to meet the normal work of the different electrical equipment.This year, with the invention of the greater variety of topologies, the voltage source inverter has been developed rapidly.But in this essay we discusstwo-level volt

7、age source inverter because it is one of the most common.Sinusoidal pulse width modulation (SPWM modulation), in order to get a better output voltage and current, the circuit control scheme is very important.People always want the circuit to have the higher voltage bus utilization, faster response t

8、ime, less low harmonic as well as small waveform distortion, but they cannot achieve.In a different circuit design, we must according to the needs SubmittedData: Signature:of the circuit of the above performance trade-offs.Then we need to know the different circuit parameters on circuit performance.

9、So the author used computer modelingTwo-Level Voltage Source SPWMInverter circuit and do some simulation with different parameters.Finally a lot of valuable conclusions have been gotten.The report described in detail in the experimental procedures and results, the final simulation model.The simulati

10、on of this report based on Matlab/Simulink.II.Part ASystem SpecificationsInverter Topology: Two-level voltage source inverter as follow Rated Inverter Output Power: 1MVARated Inverter Output Voltage:4160V (fundamental line-to-line voltage, rms)Rated Inverter Output Current: To be calculated (fundame

11、ntal, rms)Rated dc Input Voltage: Constant dc (to be determined)Load: RL load with a per-phase resistance of 0.95pu and inductance of 0.31pu, which gives the load impedance of 1.0pu with a lagging power factor of 0.95. Note that the RL load is fixed for the inverter operating under various condition

12、s.Switching Devices: Ideal switch (no power losses or forward voltage drops)Based on the given system specifications, we can calculate the circuit parameters- output current Io, dc input Vd, load resistance and inductance.As a result, III.Part BThe author developed a simulation program for the conve

13、ntional SPWM scheme and run the simulation program for the tasks given in the Table 1.For each of the tasks, the author drawn the waveforms (two cycles each) for the inverter line-to-line voltage VAB (V) and inverter output current iA (A). The harmonic spectrum (0 to 60th harmonics) of VAB normalize

14、d to the dc voltage Vd and iA normalized to its rated fundamental component I A1 will also be given.B.3 Analyze your simulation results and draw conclusions.Table 1. Simulation tasks for conventional SPWM schemeSimulation Taskf1 (Hz)maTHD (%)vABTHD (%)iAT.1200.34.020.07T.2300.74.531.47T.3301.126.701

15、4.07T.4600.631.153.13T.5600.843.2313.14T.6601.332.6813.28T.1 f1=20Hz, ma=0.3 (the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB) (the harmonic spectrum of iA)T.2 f1=30Hz, ma=0.7(the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB) (the harmonic spectrum of iA)

16、T.3 f1=30Hz, ma=1.1(the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB) (the harmonic spectrum of iA)T.4 f1=60Hz, ma=0.6(the waveform of VAB)(the waveform of iA)(the harmonic spectrum of VAB)(the harmonic spectrum of iA)T.5 f1=60Hz, ma=0.8(the waveform of VAB) (the waveform of iA

17、)(the harmonic spectrum of VAB)(the harmonic spectrum of iA)T.6 f1=60Hz, ma=1.3(the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB)(the harmonic spectrum of iA)The above diagram of the output voltage and current waveforms is similar to the sine wave, its harmonic distortion incre

18、ase as Ma increases when Ma 1, the voltage waveform in Figure will has obvious distortion.And the frequency also play an important role as we can see the harmonic distortion is very unconspicuous when f1 is very low.By amplification of the Fourier analysis of images, we found that there are no even

19、harmonics in many harmonic order.Exclude the error of the software itself, harmonic in line with the frequency will be 2 as I set fcr=2000Hz.IV.Part CI Modified simulation program developed in Part B with common mode voltage injection scheme. Table 2. Simulation tasks for common mode voltage injecti

20、on schemeSimulation Taskf1 (Hz)maTHD (%)vABTHD (%)iAT.1201.018.9013.93T.2201.230.6315.53T.3201.332.6116.13T.4601.041.5112.31T.5601.232.1012.34T.6601.332.6912.22T.1 f1=20Hz, ma=1.0(the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB) (the harmonic spectrum of iA)T.2 f1=20Hz, ma=1.2

21、(the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB) (the harmonic spectrum of iA)T.3 f1=20Hz, ma=1.3(the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB)(the harmonic spectrum of iA)T.4 f1=60Hz, ma=1.0(the waveform of VAB) (the waveform of iA)(the harmonic spe

22、ctrum of VAB) (the harmonic spectrum of iA)T.5 f1=60Hz, ma=1.2(the waveform of VAB) (the waveform of iA)(the harmonic spectrum of VAB) (the harmonic spectrum of iA)T.6 f1=60Hz, ma=1.3(the waveform of VAB)(the waveform of iA)(the harmonic spectrum of VAB)(the harmonic spectrum of iA)Starting from 0.1

23、, I changed the magnitude of the third harmonic with 0.1 as the interval.I focused on the corresponding THD and fond it has been reduced obviously though it was still very high. But the magnitude for the minimum THD of VAB was always not equal to that for the minimum THD of iA though very close, whi

24、ch gave me some trouble. And there was also an interesting conclusion that with the increase of the magnitude of the third harmonic amplitude, THD first decreased to a minimum, and then increased gradually.V.ConclusionThis report is about Two-level voltage source inverter and the matlab/simulink sim

25、ulation.The report is divided into three parts: Part A detailed derivation and calculation at all levels of the circuit parameters. Based on this, we can establish the circuit model for a software simulation.In Part B, the modulation of different magnitude is worse than the circuit performance under

26、 the inquiry to draw the relevant conclusions of different frequency circuit simulation, in contrast to further theoretical knowledge practice.Reduce the total harmonic distortion is the key to enhance the performance of the circuit. Third harmonic injection provides us with a good idea.And experime

27、nts showed that the scheme greatly improves the performance of the circuit.Overshoot after the third harmonic injected been improved, from Part C of the experiment, we clearly see that the third harmonic injection, low harmonic is significantly reduced.However, this does not mean that the third harm

28、onic the bigger the better, the greater the injection will also increase the THD, and whats worse, the difficulty of filter filtering.Therefore, continuous experimentation to seek a compromise plan.In fact, doing experiments in the laboratory to test the most suitable parameter will spend a lot of t

29、ime and money. But based on matlab simulation, the cost of this essay was almost negligible while we still got large amounts of data.And observing the results on the computer also saved a lot of time. Its obvious that computer technology is very helpful for the electrical engineering.VI.AppendixScreenshot of Matlab Model:(Part B)(Part C: plus third harmonic injection)References: 1Bin Wu, “High-power Converters and AC Drives”2王晶，翁国庆，张有兵. 电力系统的MATLAB/SIMULINK仿真与应用M. 西安：西安电子科技大学出版社，2008