电力电子化电力系统暂态稳定分析新框架:基于耦合因子的非线性解耦方法

New Analysis Framework for Transient Stability Evaluation of Power Electronics Dominated Power System: Coupling Factors Based Nonlinear Decoupling Method

不同于以同步机为主导的传统电力系统,电力电子化电力系统的惯性较低。当受到扰动时系统的状态变量极易发生较大范围的变化,使得系统面临着严重的暂态稳定性问题。然而,长期以来,对于电力电子化电力系统的暂态稳定性缺乏有效的分析工具。针对此问题,提出基于耦合因子的非线性解耦方法来进行暂态稳定分析。所提基于耦合因子的非线性解耦方法充分借鉴解耦思路,将原高阶非线性系统近似地转化为一系列解耦的一阶二次和二阶二次子系统。在解耦空间中,针对这些低阶二次非线性子系统,可以利用现有的分析工具对其进行详细地暂态稳定分析,从而可以间接地反映原系统的暂态稳定性。为有效指导非线性解耦,相应地提出耦合因子的概念,用以评价系统状态变量之间的耦合程度,便于最终确立解耦空间中的系统结构。基于耦合因子的非线性解耦方法普适性广,对所研究的电力电子化电力系统结构无特殊要求,以期成为一种新的暂态稳定分析框架。最后,通过一个直流微电网算例,对所提基于耦合因子的非线性解耦方法的有效性进行验证。

Being different from the conventional synchronous generators dominated power system, the power electronics dominated power system(PEPS) has much lower inertia. Hence, system state variables are easily changed acutely after being disturbed, which makes the system meet the serious transient stability issues. However, for a long time, there has been no effective analysis method to process the transient stability of the PEPS. Focusing on this problem, this paper proposed a coupling factors based nonlinear decoupling(CFND) method. Based on the decoupling thought, the proposed CFND method approximately transforms the original high-order nonlinear system into a series of first-order quadratic or second-order quadratic subsystems. In the decoupled state, some mature tools can be adopted to analyze these low-order quadratic subsystems. Then, the transient stability of the original system can be reflected in an indirect way. To provide the better guidance for the nonlinear decoupling, the concept about the coupling factor was proposed, which can evaluate the coupling degree among different state variables and can help determine the final form of the decoupled system. The CFND method has universality and has no special requirement for the studied PEPS, thus it can be viewed as a new analysis framework for transient stability studies. At last, through a case of a DC microgrid, the accuracy of the proposed CFND method was verified.