基于双向接口变换器的混合微电网交直流母线电压统一控制策略

Unified Control Strategy of AC/DC Bus Voltage in Hybrid Microgrid Based on Bidirectional Interfacing Converter

交直流混合微电网中,交流电压不平衡引起的接口变换器瞬时功率脉动以及单相交流负荷并入直流微电网导致的直流电压二倍频脉动,影响混合微电网正常运行。针对上述问题,建立了双向接口变换器ab坐标系下的数学模型,分析了不平衡工况下交流子网以及直流子网单相逆变负荷的二倍频功率传输特性,在此基础上,通过在双向接口变换器直流侧引入降压型波动功率补偿电路,详细设计了基于改进型双向接口变换器的交流不平衡电压及直流二倍频脉动电压统一控制策略。对补偿电路电容容量进行定量分析,使双向接口变换器可以在较小直流母线电容容量情况下,利用自身功率余量同时补偿交流不平衡电压与直流二倍频脉动电压,仿真证明了所提控制策略的有效性。

In AC/DC hybrid microgrid,the instantaneous power ripple of a bidirectional interface converter caused by AC voltage imbalance and the DC voltage double frequency ripple caused by a single-phase AC load merging into DC network,increase the loss of the bi-directional interface converter and affect the stable operation of the AC/DC hybrid microgrid.In view of the above problems,a mathematical model of the bidirectional interface converter in ana-bcoordinate system is established,and the double frequency power transmission characteristics of the AC and the DC sub network single-phase inverter loads under the unbalanced conditions are analyzed.On this basis,the unified control strategy of the AC unbalanced voltage and the DC double frequency ripple voltage based on the improved bidirectional interface converter is designed in detail.The capacity of the compensation circuit is analyzed quantitatively,so that the bidirectional interface converter can compensate the AC unbalanced voltage and the DC double frequency pulsation voltage at the same time with its own power margin under the condition of a small DC bus capacitance.The simulation results show that the proposed control strategy is effective and feasible.