Research On Cordinated Frequency Regulation Strategy Considering Multiple Demand Side Adjustable Laods

The large-scale introduction of renewable energy in the field of power generation not only improves the ecological environment,but also brings new uncertainties to the frequency stability of power system due to its uncertainty and intermittence.Demand-side resources have been paid more and more attention because of the advantages of rapidity,flexibility and economy.Various kinds of demand-side adjustable resources have huge FR potential,but the response characteristics of different loads are quite different.In order to meet the demand of FR under short time scale,it is necessary to ensure that the multi-types of adjustable loads can be well coordinated,and the adjustable loads must be well coordinated with the traditional generator sets.Therefore,it is necessary to study the method of cooperative control of various adjustable loads to maximize the value of demand-side loads,improve the flexibility of FR at a small cost,and maintain the stability of frequency.Firstly,the feasibility of demand-side adjustable load participating in FR of power system is analyzed and the modeling methods and FR strategies are summarized.Then,the load models of inverter air-conditioning(IAC),fixed frequency air-conditioning(FFAC)and electric vehicles(EV)are constructed.The IACs are applied in the primary frequency regulation(PFR)of the power system.The FFACs and EVs are applied in the secondary frequency regulation(SFR),and their control strategies are studied respectively.In addition,a coordinated control strategy of these three types of loads based on load aggregators is designed.All the specific contents are arranged as follows:(1)The basic theory of FR mechanism of power system is studied,and the FR response model of power system considering the participation of adjustable loads on the demand side is proposed.This model takes into account the FR mechanism in which the demand-side resources and the generator sets participate together and lays a theoretical foundation for future work.(2)The load control model of IAC is studied and the PFR control strategy of IAC based on working frequency control is proposed.In this strategy,the control priority is determined by the maximum control time,and a stepwise recovery strategy of setting working frequency is proposed to reduce the rebound load.The simulation is carried out in IEEE 14-node system,and the influence of recovery strategy,outage size is further analyzed.The results prove the feasibility and superiority of the proposed strategy.(3)The control strategy of the FFACs participating in the SFR is established.The priority of control is determined by the time of state-shift.At the same time,the random state recovery strategy of adjusting setting temperature is proposed.When the response process is over,this recovery strategy helps the FFAC return to its natural running state.The effect of delay trigger is analyzed and the effect of random state recovery strategy of adjusting the setting temperature is studied in the simulation.The results show that it is feasible for FFAC to participate in the SFR under the premise of satisfying the user’s comfort requirements.(4)On the basis of considering different charging and discharging states of an EV,the FR capacity of a single EV is studied.The SFR control strategy of EVs considering discharge ratio is designed.The relationship between compensation price and discharge ratio is described by using consumer psychology model.The simulation results verify the feasibility of the EVs participating in the SFR and prove that the EV can effectively adjust the system frequency in different scenes.(5)A frequency control model of the co-participation of IACs,FFACs and EVs is proposed.The coordinated FR control strategy is designed.A hybrid control method of load aggregators(LA)controlling the loads in a centralized way and decentralized control among different LAs is adopted.This strategy can effectively overcome the frequency overshot caused by the independent response of each load aggregator by delivering consistent variables among them.The PFR task is undertaken by the IACs,and the SFR task is assigned by the FFACs and EVs according to their response capacity.The simulation is carried out in IEEE 24-node system.The effect of different discharge ratios and different FR capacity are analyzed.The results show the feasibility and superiority of the proposed coordinated FR model.