Stability Analysis of a Flexible Load Virtual Inertia Control System Based on Multivariate Nyquist Array Theory

In the context of a new type of power system, for the multivariate high-order system univariate Nyquist curves do not reflect the stability of the multi-input and multi-output system well, at the same time, in order to solve the problems of the multivariate system coupling is serious and the design of the controller is cumbersome and difficult, a method of stability analysis of Nyquist arrays is proposed based on the Gershgorin disc band. Firstly, based on the general structure of the multivariate system is used to derive its forward transfer function matrix Q(s) and feedback gain transfer function matrix F, and the compensation matrix is designed for the non-diagonal dominant system. After that, the Gershgorin disc band curves of the system are plotted and stability analysis is carried out using Nyquist array theory. Finally, Matlab/Simulink simulation and dSPACE semi-physical experiments are used to verify the effectiveness of the proposed method. The proposed method enhances the decoupling degree between the controller variables and reveals the stability and operating conditions of the system under the coupling of variables. It is well adapted in multivariable flexible load virtual inertia systems.