Research On Load Frequency Control Of Power System Based On Event-triggered Mechanism

With the rapid development of communication network technology,the power system is moving towards the intelligent direction of deep integration of communication network and power network.Frequency as one of the important indicators to measure the output power quality of power system,the large fluctuation will cause impact to both power generation equipment and power-using equipment in the power system,and endanger the safe operation of the whole system in serious cases.A large number of studies have shown that Load frequency control(LFC)can effectively maintain the balance of power generation and load power,thus ensuring that the output power of the generator set can respond to the fluctuation of system load in a timely and accurate manner.The further development of power system technology requires new network communication architectures to support the increasingly decentralized nature of the control process,which has led to the gradual replacement of traditional dedicated communication methods by open networks.Network communication technology is increasingly used in power systems,which facilitates the regulation of power system load frequency by technicians but also reveals some problems such as bandwidth limitations,data packet loss and security issues caused by network attacks.Therefore,it is a hot topic to design a class of power system load frequency control scheme based on the existing results related to bandwidth limitation,network security and parameter uncertainty issues.In addition,the limitations of physical devices themselves make actuator saturation a non-negligible problem in the development of power system technology.In order to accelerate the process of power system networking,for the power system load frequency control problem,the current mainstream approach is to construct an abstract mathematical model of the turbine,valve,generator and other components in the power system framework according to their own characteristics,and then combine control theory techniques to construct the whole power system into a more general network control system model.Based on this model,the stability of LFC power system in complex environment,the design of safety controller and the control problems under the influence of actuator saturation are discussed in depth.Firstly,the bandwidth constraint problem in network communication environment is considered.Based on the existing achievements,a large number of studies have shown that the traditional Event-Triggered Mechanism(ETM)can not meet the current complex power system needs.In this context,a new dynamic trigger mechanism based on the existing event trigger technology is proposed.The trigger mechanism is very sensitive to the fluctuation of the system state.When the system state fluctuates violently,the trigger threshold can be automatically reduced to trigger more control signals.On the contrary,when the system state stabilizes,the signal reception of the control unit should be greatly reduced.In addition,the design of output feedback controller for LFC power system based on this event is also studied.A large number of experimental results show that the scheme effectively alleviates the bandwidth burden.Secondly,the controller design problem related to network security is studied.Aiming at the possible network attacks and network delay problems,a delay-dependent system model is constructed for power system,and an effective control scheme is designed to suppress the influence of network attacks on power system.Through Lyapunov function and Jensen inequality method,the stability condition of LFC power system with small conservatism is derived,and the output feedback controller suitable for power system in complex environment is designed.The results show that the strategy not only saves bandwidth resources but also effectively inhibits the impact of network attacks.Finally,the controller design of LFC power system under actuator saturation and network attacks is discussed.Saturation often occurs in the actuator and becomes a stumbling block that hinders the normal operation of the power system,which can lead to system paralysis in severe cases.Aiming at the influence of actuator saturation and deception attack on LFC power system,a mathematical model of LFC power system related to actuator saturation is constructed.Based on this model,the sufficient conditions for the asymptotic stability of power system and the design scheme of output feedback controller of LFC power system under actuator saturation are obtained by using Lyapunov theory and Wirtinger-type inequality method.The results show that the scheme can effectively suppress the impact of network attacks and actuator saturation on the power system,and ensure the normal operation of the power system while reducing the bandwidth burden.