New Inter- and Inner-Phase Power Control Method for Cascaded H-Bridge Based on Simplified PWM Strategy

Cascaded H-bridge (CHB) converters characterized with high scalability have been widely used in photovoltaic and energy storage systems. However, the three-phase power and the voltages are often unequal due to various reasons, making the system less efficient. Therefore, the ability to deal with unequal power is necessarily required in CHB. This article proposes three interphase power control methods (PCMs) based on simplified pulsewidth modulation (PWM) strategy to improve the efficiency of the system. A control method with better performance both in dynamic and steady states is adopted to adjust power distribution. The relationship between duration times and dc power is analyzed. On the basis of controlling the interphase power, an inner-phase PCM is proposed by redistributing the duration time of each submodule, to further enhance the power control ability of the system. The simulation and experimental results show that under the condition of balanced or unbalanced voltage, the interphase and inner-phase power can be controlled, which verifies the feasibility and practicability of several modulation strategies proposed in this article.