Frequency Coordinated Control Strategy Of Power System Based On Electric Vehicles And Thermostatically Controlled Loads

With the increasing installed capacity of renewable energy in power systems,the variability and uncertainty of renewable energy generation lead to the difficulties in frequency stability of the power system.Considering the high cost and limited regulation capacity of traditional frequency regulation methods,responsive loads are suggested to participate in demand response to provide the frequency regulation service.The electric vehicles(EVs)can be regarded as mobile energy storage devices,which can interact with the power system by optimizing their charging and discharging processes.The thermostatically controlled loads(TCLs)can change the working state within the constraints of users’ comfortable temperature and change their power demand.EVs and TCLs are able to participate in the frequency regulation of power systems.In this paper,the frequency coordination control strategy of power system based on EVs and TCLs is studied.The main work is as follows:1)Considering the user demand and travelling characteristics of EVs,a frequency control strategy based on response priority of EVs is proposed in this paper.Firstly,the charging and discharging process of EV is described by the charging model,then the controllable area of EV is constructed considering the constraints of user travelling demand,and the frequency regulation framework of the EV cluster is studied.Finally,the frequency control parameters of EVs are proposed based on the position of EVs in the controllable areas,and the response priority of EVs is determined.According to the proposed frequency control strategy,the proposed frequency control strategy can control the EVs to response to the frequency regulation requirements and suppress the frequency fluctuations.2)Aiming at the thermal dynamic process of TCL represented by heat pump(HP),a frequency control strategy based on the state switching sequence of TCL is proposed in this paper.The equivalent thermodynamic parameter model is applied to describe the temperature change process of HP,and the controllable area of HP is constructed.Based on this,the frequency regulation framework and frequency control parameters of TCLs are proposed to determine the state switching sequence of TCL cluster.The frequency control strategy can adjust the total power of HPs according to the proposed control strategy,and provide frequency regulation service for the power system.3)Using only EVs or HPs for the frequency regulation of power system has limited response capacity.To solve this problem,a frequency coordinated control strategy using EVs and HPs is proposed in this paper.Firstly,a parameter called state of aggregator(SOA)is introduced to describe the available response capacity of the EVs and the HPs,by which the frequency regulation requests are allocated between the EVs and the HPs according to the frequency regulation capacity of loads and the values of SOA in a coordinated way.The EV aggregator and the HP aggregator change the working status of loads to suppress the frequency fluctuation according to their own frequency control strategy.