Improved DC-link Current for Parallel Three-Phase VSCs with 2DoF Interleaving PWM

Interleaving three-phase voltage source converters (VSCs) is a popular solution for medium- and high-power applications. In addition to the circulating current, the impact of PWM strategies on the DC-link current ripple is an important issue for practical DC-link capacitor designs, which could affect system reliability and lifetime. Existing studies have been reported to evaluate the impact of conventional pulse width modulation (PWM) strategies such as space vector modulation (SVM), sinusoidal PWM (SPWM), and discontinuous PWM (DPWM). However, the impact of the recently proposed two-degree-of-freedom (2DoF) PWM has not been investigated. In this paper, the DC-link current with 2DoF interleaving PWM is analyzed by considering different modulation index and power factor range. It shows superior DC-link current performance under lower modulation index or higher power factor range comparing to the existing interleaving PWM techniques. Moreover, the influence of circulating current on the DC-link current ripple is analyzed and explained. Experiment results are obtained to verify the advantages of this proposed 2DoF interleaving PWM strategy.