Research on VIENNA Rectifier based on DSP under Unbalanced Power Grid

There are some problems in VIENNA rectifier under unbalanced grid voltage conditions, such as DC bus voltage fluctuation, active reactive power pulsation and serious harmonic distortion of grid side current. The model predictive control with fixed switching frequency(FCS-MPC) is proposed. The instruction voltage is obtained by double loop control of FCS-MPC and voltage outer loop control. The SVPWM modulation module is used to modulate the instruction voltage to generate the driving pulse signal of the VIENNA rectifier. Because the output polarity of SVPWM modulation of the VIENNA rectifier is different at each small sector pulse, the output pulse polarity configuration of the comparator in the PWM module needs to be changed continuously in one switching cycle, which can not be realized. The control method with DSP and FPGA is developed in this paper. The complex comparison part of SVPWM modulation is accomplished by FPGA. Finally, the experimental prototype of a 7.5KW three level VIENNA rectifier was built to verify the proposed control strategy. The experimental results have shown that the method is correct and effective under the condition of unbalanced voltage.