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.

将三相电压源转换器（VSCs）交错连接是一种广泛应用于中高功率应用场景的解决方案。除了环流电流外，脉宽调制（PWM）策略对直流链路电流纹波的影响也是实际直流链路电容器设计中一个至关重要的议题，这可能会对系统的可靠性和使用寿命产生不利影响。已有研究对传统脉冲宽度调制策略，如空间矢量调制（SVM）、正弦PWM（SPWM）和断续PWM（DPWM）的影响进行了评估。然而，最近提出的二自由度（2DoF）PWM的影响尚未得到充分研究。在本文中，通过考虑不同的调制指数和功率因数范围，对采用2DoF交错PWM的直流链路电流进行了分析。结果表明，与现有的交错PWM技术相比，在较低的调制指数或较高的功率因数范围内，该策略展现了更优的直流链路电流性能。此外，对环流电流对直流链路电流纹波的影响进行了分析和解释。通过实验结果验证了所提出的2DoF交错PWM策略的优势。