| As one of the most important energy sources for the development of society,electric energy plays an important role in national economy and people’s livelihood.Chinese power system is becoming more and more complex,which requires higher and higher utilization efficiency of power generation energy,therefore,the requirements for power system stability are increasing.Under the guidance of the principle of "transmission from west to east,mutual supply from north to south,and nationwide interconnection",China is building a regional interconnected power grid that is suitable for large-scale cross-regional power transmission.The large-scale interconnected power grid strengthens the electrical connection of the power grids in various regions and improves the economics of power grid operation,but at the same time,it also makes the operation condition of power grid more complex,leading to the occurrence of low-frequency oscillations between regions that endanger the stable operation of the system.In this case,the local control method which only relies on the local signal is still adopted,and it is difficult to control the wide area power system accurately,so the wide area control method of the power system emerges as the times require.The emergence of wide-area measurement systems has vigorously promoted the development of stable control technologies for large-scale interconnected power systems.Due to the use of remote control signals,its delay cannot be neglected,and the stability of the wide-area time-delay power system is accurately analyzed in advance,which plays an important role in its reliable operation.This article has made a more in-depth study on the signal transmission delay in the wide area power system.The main contents include:(1)For interconnected wide-area power systems,considering multiple secondary loops with transmission delay and the presence of time-varying uncertainties in parameters.Then,based on the description of differential algebraic equations for power systems without delays,adding time-delay terms and uncertainty disturbance terms,and the mathematical models for studying its stability and robust stability are derived respectively;(2)The improved stability criterion for multi-delay control system is given,the double integral term is added to the Lyapunov-Krasovskii functional augmentation vector,and the redundant part of the functional is also eliminated,and a better description system is constructed,then use the improved integration inequality with very little conservatism to define the integral terms that still exist after the functional derivative,finally,the outgoing line is derived The improved stability criterion of multi time-delay power system based on the matrix inequality scheme.This criterion has a more free solution space,so the conservativeness is very small,and no additional loose variables are introduced,so this criterion has very few decision variables and has favorable calculation efficiency.The stability criterion is less conservative than the existing ones,in addition,the criterion can effectively calculate multiple time-delay stability intervals of the system,and the calculation result is accurate.At present,other criteria cannot Reveal this phenomenon;(3)Based on the improved stability criteria for multi-delays control systems,the influence of the norm bounded time-varying parameter uncertainty on the wide-area power system with time-delay is considered.By constructing a better Lyapunov-krasovskii functional,and then combining with the improved integral inequality,and applying two lemmas to deal with the disturbance,the multi-delays control system with linear matrix inequality format is derived.The improved robust stability criterion makes full use of the delay boundary information of the uncertain system with multi-delays to provide additional degrees of freedom for solution,so the conservatism of the criterion is very small.The multi-delays power system stability criterion and robust stability criterion deduced in this paper,can provide a reference for the stability analysis and control design of practical wide-area power systems,which is of great significance both in theoretical research and in engineering application. |
