考虑源端动态特性的光伏虚拟同步机多模式运行控制

Multi-mode Operation Control for Photovoltaic Virtual Synchronous Generator Considering the Dynamic Characteristics of Primary Source

分布式光伏发电主要以最大功率跟踪(maximum power point tracking,MPPT)方式并网运行,缺乏离网运行能力,且难以为电力系统提供有利于系统稳定的惯量和阻尼。虚拟同步机(virtual synchronous generator,VSG)因集成了传统同步机的运行机制以及电力电子设备控制灵活、响应迅速等优势,备受分布式发电领域专家的关注。结合虚拟同步机技术,并考虑光伏电源的时变性和有限性,提出了计及光伏电源动态特征的光伏虚拟同步机(photovoltaic VSG,PV-VSG)及其控制策略。根据光伏出力曲线与特征值分析得到光伏电源稳定运行区域;设计了光伏电源附加控制策略,可防止因光伏电源最大可用功率不足而造成的直流电压跌落,以保证PV-VSG直流侧电压稳定,并可根据负载或调度功率需求提供最有效的功率匹配。所提控制策略可使光伏电源直接通过虚拟同步发电机接入,并实现了离网与并网的灵活可靠运行。仿真分析与实验测试结果均验证了所提控制策略的有效性。

The distributed photovoltaic mainly operates at the maximum power point and connected to the power grid, which is lack of the operation of islanded mode and is hard to provide extra inertia and damping for the system stability. The virtual synchronous generator, which integrates the advantages of traditional synchronous generator and power electronics devices, is playing a more and more important role in the field of distributed generation. Combing the VSG technology and considering the dynamic characteristics of primary source, the Photovoltaic VSG（PV-VSG） and its control strategies are proposed. Firstly, the stability operation region of PV is obtained by theoretical analysis; Then, the PV-VSG control strategy is designed to ensure the DC voltage stable as well as to meet different power demands. The proposed PV-VSG makes it possible to achieve the PV connecting to the power grid through VSG directly, and the PV-VSG has two typical operation mode, such as grid-connected mode and islanded mode. The simulation and experimental results verify the correctness and effectiveness of the proposed PV-VSG control strategy.