不平衡负载工况下三相变流器有源功率解耦控制

三相电压源型变流器(VSC)对于微电网的稳定运行有着重要的作用。然而,孤岛工况下带三相不平衡负载运行时,交流侧产生的二次脉动功率耦合至直流侧,导致系统的工作性能降低并影响系统的寿命。针对该问题,在二次功率脉动分析的基础上,提出了一种基于虚拟三相瞬时功率的解耦控制策略,通过控制虚拟三相瞬时功率脉动分量为0,在不增加开关器件的情况下,利用LCL滤波器中电容提供负载所需二次脉动功率,实现交直流侧二次脉动功率解耦。在此基础上进一步分析了该拓扑结构直流侧所需的最低电压以及电流应力影响因素。最后仿真和实验结果均表明所提控制策略可以较好地实现功率解耦控制,直流侧源电流二次脉动分量大大减小,有利于提高系统控制性能和实现直流侧电容轻量化。

Active Power Decoupling Control of Three-phase Converter With Unbalanced Load

Three-phase voltage source converter(VSC) plays important role in stable operation of microgrid. However, when operating with a three-phase unbalanced load under island condition, the secondary pulsating power generated on AC side is coupled to DC side, resulting in system performance degradation and affecting system life. Aiming at this problem, based on secondary power pulsation analysis, a decoupling control strategy based on virtual three-phase instantaneous power is proposed. By controlling the virtual three-phase instantaneous power pulsation component to zero, the secondary pulsating power required by the load is provided by the capacitors in LCL filter to realize secondary pulsation power decoupling between AC and DC sides without adding switching devices. Based on this, the influence factor of the minimum voltage on DC side of the topology and current stress are further analyzed. Finally, simulation and experimental results show that the proposed control strategy can achieve better power decoupling, and the ripple component in DC side source current is greatly reduced, which is beneficial to improve system control performance and realize weight reduction of DC side capacitor.