A Novel Midpoint Voltage Balance Control Strategy Based on Resonant Current Adjustment for Auxiliary Resonant Commutated Pole Inverter

The auxiliary resonant commutated pole (ARCP) inverter with dc-link divider capacitors has the midpoint voltage fluctuation in the motor drive application since the fundamental frequency starts at zero. This problem leads to incomplete soft-switching and additional losses. In this article, a novel midpoint voltage balance control strategy is proposed to eliminate the midpoint voltage fluctuation of the ARCP inverter in full operating conditions. First, the transferred charges of the commutation during the switching period are calculated, and the precharge currents are adjusted to make the total transferred charge balanced in each switching period. Second, a resonant switching action scheme and a midpoint voltage balance strategy in the interference modulation and overmodulation regions are proposed for the safety of the full operating conditions. Experimental verifications prove that, compared with the traditional control method, the midpoint voltage fluctuation during low-frequency operation is significantly decreased by more than 52% with the proposed strategy, which reduces the demand for dc-link divider capacitance and achieves an efficiency of up to 99.14%. Therefore, the proposed strategy makes the ARCP inverter safer and more efficient for motor drive applications under full operating conditions.