基于虚拟同步电机的交直流混合微电网控制策略

A Novel Control Strategy of AC/DC Converter in Hybrid Microgrid Based on Virtual Synchronous Generator

交直流混合微电网中,由一台或多台联络换流器(interfacing converter,IFC)实现交、直流网络之间的能量传递,分布式电源的效率以及系统的稳定性很大程度取决于IFC的控制策略。传统基于电压环、电流环结构的IFC控制策略存在弱电网下稳定性差、需要交流电源提供参考正弦电压等问题。针对这些问题,该文利用直流网络电压与虚拟转速归一化后的差值作为虚拟机械力矩,提出一种基于虚拟同步发电机技术的IFC控制策略。通过建立其小信号模型来证明所提控制策略的稳定性对参数的选取不敏感,有较强的鲁棒性。最后,利用PSCAD/EMTDC在孤岛情况下对所提算法进行测试,测试结果表明,所提算法能有效改善被动孤岛过程中的动态性能,同时能较好地实现交、直流电源输出功率分配以及联络换流器之间的均流。

In hybrid microgrid, interfacing converters（IFC） connect the AC and DC subgrid. The control strategy significantly affect the stability of hybrid microgrid and the efficiency of DGs. Most traditional control strategies of IFC are consist of voltage loop and current loop, which need sinusoidal voltage provided by AC sources as reference and have poor stability in weak network. Under these motivations, a novel control strategy of IFC based on virtual synchronous generator（VSG） technology is proposed, using the error between normalized DC voltage and virtual rotating speed as virtual mechanical torque. Furthermore, a small-signal model is built to prove that the stability of the system is insensitive to its parameters. Finally, based on a typical hybrid microgrid, simulated results on PSCAD/EMTDC have verified that the proposed control strategy can effectively improve the dynamic performance under sudden island operation. Meanwhile, equivalent power transfers among DGs and IFCs can be achieved.