单/三相混合微电网中虚拟组合式三相变流器功率协调控制

针对单/三相混合微电网系统孤岛运行时单相电源和负载引起的三相电压不平衡问题,提出了虚拟组合式三相变流器及其功率协调控制。详细阐述了基于虚拟三相瞬时功率的下垂控制和虚拟阻抗控制,实现同相并联单元的功率分配。针对组合式三相变流器相间同步控制难点,提出了新型120°鉴相器和基于锁相环原理的相间同步控制,提高三相电压平衡度。在此基础上,给出了电压补偿控制,进一步改善供电质量。同相及相间功率协调控制无需附加任何同步芯片或通信线,原理简单,控制灵活,可靠性高。最后,仿真和实验结果表明所提控制策略可以实现动稳态工况下同相并联单元间功率按照设定比例分配以及不同相间相位和幅值的同步控制,100%不平衡负载下电压不平衡度为0.1%,供电质量较高。

Coordinated Power Control of Virtual Combined Three-phase Converter in Single-phase/Three-phase Hybrid Microgrid

When the single-phase/three-phase hybrid microgrid operates in an islanded mode, the three-phase voltage unbalance caused by single-phase power sources or loads may appear. To address this problem, the virtual combined three-phase converter and its coordinated power control are proposed. The droop control and virtual impedance control based on virtual three-phase instantaneous power are employed to achieve power sharing for the units paralleled in the same phase. Aiming at the control difficulty of interphase synchronous in combined three-phase converters, a novel 120° phase detector and the phase-locked loop based interphase synchronous control are proposed to improve three-phase voltage balance. On this basis, the voltage compensation control is given to further improve the power supply quality. The coordinated power control for the units in the same phase or between different phases is realized without any additional synchronous chips or communication lines. Its advantages of easy implementation, flexibility and high reliability are presented. Finally, simulation and experimental results show that, in various dynamic and steady state scenarios, the proposed control strategy can obtain power sharing for units paralleled in the same phase according to the set proportion and interphase phase and amplitude synchronous control. The voltage unbalance factor is 0. 1% under 100% unbalanced load condition.