Decoupling Control Strategy for Conergy Three-Level Three Phase Grid Converter

Abstract

Conergy three-level NPC topology is often used in grid connected inverter due to its high efficiency, fewer switching devices and better EMI performance. Traditional half-bridge topology can be transformed to Conergy NPC topology by adding bi-direction switches. This paper proposed a novel control strategy for Conergy three-level NPC three phase grid converter with real and reactive power closed-loop controller in the synchronous d-q rotating frame. The power control loop is based on the feed forward decoupling of d-axis and q-axis components of the output current, thus the active and reactive power can be controlled separately. Additionally a proportional-integral controller is added to enhance the robustness of the power controller. Simulation results verify the effectiveness of the proposed strategy.