Antiovervoltage Control Strategy for Electrolytic Capacitorless PMSM Drives Based on Power Balance State Regulation

Addressing the coupling effect between speed and voltage controllers in the traditional antiovervoltage control strategy for electrolytic capacitorless permanent magnet synchronous motor (PMSM) drives, a novel antiovervoltage control strategy based on power balance state regulation is proposed. The active–reactive power coordinate frame based on synthesized voltage vector orientation is constructed in the proposed scheme. Subsequently, the power balance current for maintaining dc-link voltage constant can be extracted independently of inverter and motor parameters. To achieve the decoupling between controllers, the power balance current is set as a threshold to switch the designed operating mode. Thus, the coupling issue can be solved between the speed and voltage controllers in the case of reduced dc-link capacitance values. To control the dc-link voltage following the designed voltage trajectory in braking mode, the active and reactive currents are allocated based on the power balance current. Furthermore, controller coefficients are designed from frequency domain to ensure a sufficient phase margin. While ensuring maximum copper loss, the dc-link voltage overshoot can be significantly reduced by the proposed scheme. Experimental results validate the effectiveness of the proposed scheme in 2.2-kW reduced dc-link capacitance PMSM drives. Compared with the traditional antiovervoltage control scheme, the proposed scheme can suppress dc-link voltage overshoot to 2%.