多VSG单元的惯量协调控制策略研究

Research on inertia coordinated control strategy of multiple VSG cells

大规模光伏并网系统中常采用多个虚拟同步发电机(virtual synchronous generator,VSG)单元进行协调配合,为电网提供虚拟惯性。但在实际运行中,虚拟惯量分配不合理会导致系统频率响应差及源端易损等。针对此问题,提出一种针对混合光储多VSG单元的惯量协调控制策略。该策略通过构造隶属函数,将储能单元荷电状态、换流器可调功率、储能充放电可调功率3个指标转化到同一量纲下,以解决惯量分配时多目标转换困难的问题。同时,为区分各指标对频率稳定的重要程度,避免惯量分配时权重选择的主观性,构建一种权重优化系数,可根据指标的差异度实时调节权重。通过建立六端交流系统小信号模型,运用根轨迹法对隶属函数中主导参数进行稳定性分析,进而确定参数选取范围。在MATLAB/SIMULINK中搭建光储六端交流系统模型并进行时域仿真,仿真结果可以验证所提控制策略的有效性。

In large-scale photovoltaic grid-connected systems,multiple virtual synchronous generator(VSG)units are often used to coordinate and provide virtual inertia for the grid.However,the unreasonable distribution of virtual inertia will lead to poor system frequency response and source-end vulnerability in actual operation.To solve this problem,this paper proposes an inertia coordination control strategy for hybrid optical storage multiple VSG cells.By using the membership function,the strategy converts three indicators of the state of charge of the energy storage unit,i.e.,the adjustable power of the converter and the adjustable power of the energy storage charge and discharge,into the same dimension,so as to solve the problem of multi-objective conversion in the moment of inertia distribution.At the same time,the parameters in the membership function can be flexibly adjusted according to the index characteristics to adapt to the inertia distribution under different working conditions.By establishing a small signal model of six-terminal AC system,the root locus method is used to analyze the stability of the dominant parameters in the membership function,and then to determine the parameter selection range.The optical storage six-terminal AC system model was built in MATLAB/SIMULINK and the time domain simulation was carried out.The simulation results verified the effectiveness of the proposed control strategy.