A Space Vector Pulse Width Modulation Strategy Of Low Common-Mode Voltage In Inverters

The common-mode voltage for the output of inverter is the main negative factor on influencing the normal operation of the variable frequency drive system. It will lead to the damage of bearing and cause a serious impact on the stability and the life of motor running. In this paper, it is the aim to inhibit the common-mode voltage effectively for the output of inverter. Based on the traditional voltage space vector modulation strategy, a novel one is proposed that can inhibit the common-mode voltage effectively and provide a theoretical basis of the common-mode voltage suppression method for further study.Under the traditional voltage space vector modulation strategy, high common-mode voltage is produced by inverters mainly due to the zero vectors, so that the common-mode voltage for the output of inverter has reached half of the DC bus voltage. Therefore, this paper provides an improved three sectors voltage space vector modulation strategy, which eliminates the effect of two zero vectors. A new sector is divided on the basis of the six non-zero vector. It makes the calculation of a non-zero vector modulation time and the judgment of sector to achieve the calculation in the new sectors and the modulation in traditional nonzero vector on purpose. The SVPWM modulation strategies for the improved three sectors itself characteristics are analyzed. The modulation waveform of this modulation strategy is sine wave, the DC bus voltage utilization ratio is 86.6%, the harmonic of motor phase and line voltage are increased, but it suppresses the non-carrier frequency of integer multiple harmonic for times, and has little effect on the phase current harmonic of the motor.The MATLAB/simulink simulation model of the improved three sectors SVPWM modulation strategy is built. It is applied in the motor control model. The correctness and motor performance of the improved three sector SVPWM modulation strategies are analyzed by simulation; the motor control system based on DSP28335 hardware experimental platform and GUI visual graphic interface based on MATLAB are built to further verify the correctness of the improved three sectors SVPWM modulation strategy. The results of simulation and experiment show the validity of theoretical analysis and the stability of the improved three sectors SVPWM modulation strategy. Through simulation and experiments, it is verified the common-mode voltage for the output of inverter drops to about 60% than the traditional voltage space vector modulation strategy.