独立光储直流微电网分层协调控制

Hierarchical coordinated control of island DC microgrid with photovoltaic and storage system

针对独立运行的光储直流微电网,提出分层协调控制策略。第一层控制光伏和储能系统等单元独立运行,且各单元变流器可依次对母线电压进行自动调节。采用自适应下垂控制协调多组储能来稳定母线电压并根据最大功率和荷电状态自动协调不同储能电池之间的负荷功率分配。当独立直流微电网中所需储能系统充电功率超过其最大允许功率时,光伏系统由最大功率跟踪控制切换为下垂模式控制母线电压稳定,且不同光伏单元可根据各自最大功率自动分配负荷功率,同时采用电压前馈补偿控制动态调整下垂控制器的参考电压将母线电压提升至额定值。为了提高运行效率并增强直流母线电压的稳定性,第二层控制根据母线电压协调不同变流器的工作方式,确保不同工作模式下均有变流器根据电压下垂特性控制直流电压来维持系统内的有功功率平衡。最后在Matlab/Simulink搭建仿真模块,分别验证在三种不同工作模式下所设计分层控制策略的有效性。仿真结果表明,该分层控制可实现独立直流微电网的稳定运行。

This paper presents a hierarchical coordinated control for autonomous DC microgrid with photovoltaic and storage system. In order to assure the voltage stability, under the primary control, units including photovoltaic and energy storage system operate independently, and converters in each unit are responsible for voltage stability in turn under different operation modes. Multi-groups of batteries that equipped with self-adaptation droop control are used to stabilize voltage and the load power is dynamically shared by the batteries according to their states of charge and maximum power. Photovoltaic system is switched to droop mode to stabilize bus voltage when the charge power of storage system in autonomous DC microgrid is more than its maximum limitation, the load power is dynamically shared by PV units according to their maximum power and the voltage feed forward control is used to reduce voltage fluctuation through dynamical adjusting reference voltage of droop controller. In order to improve the system efficiency and enhance bus voltage stability, the supervisory control is designed to control operation modes of converters, which assures that there＇s always have converters responsible for voltage stability through the droop control. Under the proposed hierarchical control, the autonomous DC microgrid runs in three different operation modes. The simulation results in Matlab software indicate the proposed strategy makes the DC microgrid operate stably.