弱电网条件下虚拟同步机与SVG并联系统的暂态稳定性分析

Transient Stability Analysis of Virtual Synchronous Generator and SVG Parallel System Under Weak Grid Conditions

虚拟同步发电机(virtual synchronous generator,VSG)控制策略因具有较好的频率响应和惯量支撑特性已被广泛用于新能源并网逆变器。针对VSG的无功电压下垂特性对其功角稳定性的不利影响,可通过并联静止无功发生器(static var generator,SVG)来改善。首先,给出了VSG与SVG并联系统的典型控制策略,并利用功角特性曲线分析了VSG电压下垂特性对其暂态稳定性的影响。然后,建立了VSG-SVG并联系统的全阶非线性模型。进而利用T-S模糊模型逼近和线性矩阵不等式方法构建了针对非线性系统的Lyapunov稳定性判据,并定量估计了系统的功角稳定域。最后,分析了电路参数和控制参数对系统稳定性的影响。利用MATLAB仿真及硬件在环实验对理论分析结果的有效性进行了验证。

Owing to its good frequency response and inertial support,the virtual synchronous generator(VSG)control strategy has been widely used for inverters in renewable energy generation.However,the voltage droop characteristics may bring about an adverse impact on the transient stability of the VSG.To deal with this issue and provide better reactive power support,a static var generator(SVG)is generally applied to parallel with the VSG.Firstly,the typical control strategies are given for the VSG-SVG system,and the adverse impacts of the voltage droop characteristics is investigated based on the power-angle curve.Then,a full-order nonlinear dynamic model of the VSG-SVG system is established.With the application of T-S fuzzy modeling and linear matrix inequality(LMI)methods,a Lyapunov-based stability criterion is proposed to estimate the stability region of the paralleled system.Finally,the impacts of circuit parameters and controller parameters on the system stability are studied.To validate the effectiveness of the proposed stability analysis,the MATLAB simulation and hardware-in-loop experiment are carried out.