Control strategy for suppression of circulating current using high-frequency voltage compensation in asynchronous carriers for modular and scalable inverter systems

Abstract

In this study, a circulating current suppression strategy is proposed using high-frequency voltage compensation when asynchronous carriers exist between modules in modular and scalable inverter systems (MSISs). In MSIS, an inverter and a control unit constitute one module. Because each module is connected in parallel, the power capacity and efficiency can be increased. However, according to the switching state in the parallel module, a circulating current can be generated. This current causes stress on the switches. Furthermore, the circulating current not only deteriorates the current control performance but also increases the difficulty of load sharing. In this study, a novel method is proposed to suppress high-frequency circulating current caused by asynchronous carriers. This current can be reduced by generating the same switching pattern in two modules using high-frequency voltage compensation. Simulation and experimental results are presented to verify the proposed method.