| With the development of high power self-turn-off devices and microcontroller, high power electronic equipment is increasingly deeply studied and is more and more widely applied in large capacitance motor drive, power transmission and so on. But an important problem is that the low working frequency of high power devices is not to apply some better modulated technique of PWM. Phase shift Space Vector Modulation technique (PS-SVPWM) presented in this paper is just about an excellent modulated technique to solve the problem mentioned above, and to reduce the high order harmonics produced by PWM control efficiently.The basic principle and modulation technique of SVPWM are introduced in the paper. Based on the SVPWM and the carrier phase-shifted SPWM, continuous symmentrical switching modulation(seven segments) and zero vectors alternation modulation (switching frequency optimized modulation) are applied in PS-SVPWM, also its realizing method is presented.The PS-SVPWM method is simulated dynamically by using MATLAB6.5.1/ SIMULINK dynamic simulation software. Compared with the conventional carrier phase shift SPWM, the output harmonic feature of the cascaded multilevel inverters with seven segments modulation and zero vectors alternation modulation PS-SVPWM is researched and analyzed through simulation.It is obvious that seven segments modulation and zero vectors alternation modulation PS-SVPWM can reach an effect of higher equivalent switching frequency through counteracting lower order harmonics,so it has a perfect performance on harmonic feature. Compared with carrier phase-shifted SPWM, PS-SVPWM has higher linear operating range, easier implementation by digital and is more suitable for motor drive occasion. Especially the way of zero vector by turns of switch frequency optimized modulation has lower device switching frequency and lower harmonic of output voltage. But because Seven segments have four segments zero vectors, its pulse torgue become very small. |
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