Design Of Frequency Controller For Isolated Microgrid Based On Random Long Delay In Communication Of Cyber Physical System

The rapid development of communication technology and computer technology has provided the key technology for the intellectualization of microgrid.As an efficient and flexible way of energy utilization,microgrid is the best solution to solve the power supply problem that the main grid can not.With the development of microgrid,considering the randomness and intermittence of new energy output and the fluctuation of load,it is necessary to carry out global real-time monitoring.This requires the introduction of communication network to transmit the data collected from the bottom and the control instructions issued by the controller.Microgrid has gradually developed into a tight coupling network control system(NCS)between continuous-time power system and discrete-time information system.It is a typical Cyber Physical System(CPS).Existing NCS studies have shown that due to the existence of network timedelay,the original physical system performance degradation,or even destroy the stability of the system.In view of the above problems,considering the development of microgrid,this paper studies the design of frequency controller for island micro-grid based on wireless communication with random long time-delay.Firstly,the particularity of microgrid communication is introduced,and then the communication delay in microgrid is discussed.Then,a cascade delay model considering the load variation of communication network is established by using queuing theory.Secondly,considering the inherent continuous time characteristics of power system,the frequency of microgrid under continuous time is established.Then,considering the discrete event characteristics of the information system,and in order to avoid the influence of sampling period on the control performance of the continuous system,a time-delay microgrid frequency control model with communication delay in discrete time is established,in which uncertainties such as new energy and load fluctuation are also considered.Then,the controller is designed according to the linear quadratic Gaussian control method in stochastic optimal control theory to reduce the influence of communication delay on the frequency stability of power grid.Finally,in the part of simulation experiment,the influence of communication delay on the frequency stability of microgrid is verified,and the importance of considering the influence of communication delay is clarified.Secondly,the frequency response of microgrid with different controllers is simulated in the fixed time-delay scenario;then the random time-delay scenario caused by network load changes is simulated;finally,the frequency response of microgrid with different network size is simulated.The results show that the proposed delay model and controller design method can effectively reduce the influence of communication delay on frequency stability,reduce the maximum frequency deviation and adjustment time in the frequency dynamic process of microgrid,and improve the dynamic performance of microgrid frequency.