应用于光伏微网的一种虚拟同步发电机结构及其动态性能分析

A Hardware Structure of Virtual Synchronous Generator in Photovoltaic Microgrid and Its Dynamic Performance Analysis

可再生能源、分布式发电和微电网技术长期以来受到广泛关注,传统的并网逆变器控制策略没有考虑其惯性缺失导致频率变化率过快的问题,因而采用虚拟同步发电机策略模拟同步机特性,提升新能源并网发电的备用旋转惯量。对于光伏微电网,当前大多数的虚拟同步机方案将光-储结合结构作为直流侧,其性能的实现仅需要控制逆变器模拟同步机特性即可。该方案控制策略简单,但具有硬件结构复杂、不灵活的缺陷。文章介绍了一种光伏微电网中的虚拟同步发电机结构的应用以及相应控制策略,并研究其动态性能,该结构灵活可靠、易于扩展。仿真和实验证明了该结构及相应的控制策略能在光伏功率波动和负载变化时稳定母线频率,提升微电网的动态性能。

Renewable energy resources and distributed generations have attracted much attention in recent years. However, control strategies of inverters in microgrids usually ignore rate of change of frequency due to lack of rotary inertia. Therefore, virtual synchronous generator（VSG） is proposed to imitate traditional synchronous generator and then provide backup inertia. In most available schemes of VSG in photovoltaic microgrid, photovoltaic arrays and energy storages are combined and controlled through a dc-dc converter, which are connected to the dc-bus of inverter. The scheme is easy for inverter control but increases complexity of hardware implementation and lacks flexibility and reliability. In this paper, a hardware structure and corresponding control strategies were proposed for implementation of VSG in photovoltaic microgrid, which can enhance performance of VSG in flexibility, reliability and augment ability. Dynamic performance was studied through transfer function model. The proposed strategy was verified in simulation and experiment.