直流微电网离网与并网运行统一控制策略

Unified Control Strategy of Islanding and Grid-connected Operations for DC Microgrid

越来越多直流电源及直流负载的应用促进了人们对直流微电网技术的关注。该文以低压单母线型直流微电网系统为研究对象,将系统并网与离网运行模式结合在一起设计基于直流母线电压信息的协调自治控制方案。系统内各单元可依据当前直流母线电压实现并网、离网运行的无缝切换。使用下垂控制对工作在恒压输出下的多个分布式发电单元和蓄电池单元进行功率均分,给出了下垂系数选取原则。提出一种非重要负载降功率运行稳定直流母线电压的控制策略。通过系统仿真对所提控制方案进行验证,系统可根据预定控制方案在各模式间切换,若遇交流电网故障,系统可自主跳过并网模式进入离网运行,实现了系统离、并网运行的统一控制。非重要负载在系统内能量不足时主动降功率运行,提高了系统稳定运行区间。

DC microgrids are gaining an increasing interest because more and more DC load and DC power generation are used in renewable energy applications. In this paper, an autonomous control scheme based on DC bus voltage levels was proposed in a low-voltage single type DC bus microgrid system. The design ideas of control scheme combined both grid-connected and islanding operating conditions. In the system, distributed power generation units and battery energy storage system operating in constant voltage control can achieve power sharing by added droop control. The design method of droop gain was presented. A power cut-back control strategy for non-critical loads converter was proposed. The simulation results demonstrated the proposed scheme during various operating conditions. The system can automatically skip to islanding mode from grid-connected mode in case of AC grid failure. Non-critical loads converter can switch to power-reducing mode when the energy in the system is deficient and improves the system available operating range.