An improved control strategy for hybrid active front-end converters in grid-connected applications

Active front-end converters with bidirectional power flow capability have been extensively used for utility applications of power electronics, in which the hybrid type with copupling capacitor in series connection is receiving much attention due to its low operating voltage and low switching ripples. This paper proposes an improved control strategy for hybrid active front-end converters in grid-connected applications. Real power of the converter are controlled by adjusting the reactive current, while reactive power delivered to the power system is dependent on the real current of the converter. Due to series-connected capacitor, the converter can be operated between a low-voltage dc side and high-voltage grid side without any low-frequency transformer. Operation principles are explained in detail, and computer simulations and experimental results are provided to validate the effectiveness of the proposed approach.