A General Current Ripple Prediction Method for the Multiphase Voltage Source Converter

摘要

Current ripple is generated by pulse width modulation (PWM) switching in multiphase voltage source converters (VSCs). This letter introduces a general and fast current ripple prediction method for multiphase VSCs with arbitrary phase numbers. An equivalent converter-load model is derived for the $n$ -phase converter system. By combining the common-mode voltage of both converter terminal and load, the equivalent circuit for each phase can be modeled. The voltage dropping on the ac inductor can be calculated for the 2 $n$ + 2 zones in each switching cycle based on the equivalent circuit for each phase. Then the current ripple can be reconstructed based on the linear di/dt model in each zone. Simulation examples of five- and six-phase converters prove that the current prediction method is accurate. With this real-time prediction method, the current ripple can be controlled in application. An application example of five-phase variable switching frequency PWM is introduced to control the peak current ripple and reduce the switching losses.