并网变换器的暂态同步稳定性分析:稳定域估计与镇定控制

Transient Grid-synchronization Stability Analysis of Grid-tied Voltage Source Converters:Stability Region Estimation and Stabilization Control

针对并网变换器在大扰动下暂态同步稳定性问题,当前的研究缺少基于直接法的严谨分析(如稳定域估计)。为此,该文构造解析的李雅普诺夫函数,通过研究耗散区间和最大临界等位面得到稳定域的定量估计方法。据此,进一步给出暂态同步稳定性的定量判据及稳定裕度指标,定量分析实际变量对暂态同步稳定性的影响。在此基础上提出两种稳定控制方法:一种通过补偿锁相环的负阻尼效应扩大稳定域范围;另一种通过重塑状态轨迹将锁相环的状态引导至稳定域内,以实现失稳镇定。所提稳定域估计方法相较当前其他解析方法(如等面积法)更为严格;所提镇定控制方法的有效性均在PSCAD/EMTDC仿真和RT-LAB硬件在环平台进行了全面验证。

Regarding the transient grid-synchronization stability(GSS) of the phase-locked loop(PLL)-synchronized voltage source converters(VSCs), a rigorous practice of Lyapunov’s direct method(e.g., stability region estimation) is still in need. In this regard, a dedicated Lyapunov function(LF)was proposed, and its dissipative-region-based critical level set was derived. A stability criterion was developed, as well as an analytical stability index, to evaluate the GSS of the VSC.Quantitative analysis of the parametric influence on GSS was conducted accordingly, and two control methods were raised to improve the GSS, i.e., the phase-locked loop stabilizer(PLLS)and the PLL-integrator-limiter-based stabilization method. The PLLS could compensate the negative damping effect of PLL,while the integrator limiter could guide the unstable states back into the stability region. The proposed method for GSS evaluation exhibits better performance than the previous methods(e.g., the equal area criterion(EAC)). Furthermore,the proposed stability control methods can be verified via both PSCAD/EMTDC simulation and RT-LAB controller hardwarein-loop(CHIL) platform.