Research On Theory And Market Application Of Power System Frequency Regulation Service Considering Dynamic Controllable Load

The high penetration combined with the intermittent nature of large-scale distributed generation and the continuous growth of peak load in China bring a number of uncertainties to power system operation.In particular,the large fluctuation of wind or solar power output in extreme weather,as well as DC blocking and other failures,have posed significant challenges to the frequency stability.In order to correct the instability between generation and load,conventional generators may be required to provide more frequency regulation(FR)capacity.However,this will result in low efficiencies,high cost and short lifetimes.In recent years,researchers have been actively exploring the utilization of dynamic Dmand Response(DDR)in FR as well as the coordinated dispatch of sourch-load.The dynamic controllable loads(DCLs)can quickly adjust the power consumption under flexible control strategies with little impact on consumers' comfort.As a result,the DCL is a promising approach to maintain the power balance of the grid and to provide auxiliary services for FR,which promotes the renewable energy consumption and enhances the flexibility of the power system.In addition,with the deepening of the power market reform,the new situation brings new requirements for the market trade of FR services in China.The market mechanism design for the auxiliary service in China is in the exploratory stage.Therefore,it is of great practical significance to study the theory and market application of DCLs participating in power system FR service.Based on the process of the power market reform in China,the feasibility of DDR participating in power system FR is analyzed and the existing DCL modeling methods and control strategies are summarized.Since the potential of residential loads to provide FR service via DDR is huge,the air-conditioning load and electric vehicle load from residential level are taken as our research objects.The DCL control strategy for the load aggregator(LA)is proposed to provide both Primary Frequency Regulation(PFR)and Secondary Frequency Regulation(SFR).In addition,the operation framework of LAs to participate in the auxiliary service market is designed,and the DDR dispatch strategy of LAs to participate in the day-ahead market is studied.All the specific contents are arranged as follows:1.The operation framework for the LA to implement DDR is proposed based on the role of LAs.The detailed process of implementing DDR under the common direct load control is introduced,which is the foundation for the research on the residential load control strategy.The services provided by the LA trough the DDR projects are analyzed and the operation mechanism for LAs to participate in the power market is proposed,which lays a theoretical foundation for future work.2.A detailed control framework for the LA to participate in FR is presented based on the residential heating,ventilation and air conditioner(HVAC)loads.The response priority approach is introduced which chooses efficient responsive loads with a shorter state-shift time,which poses less impact on the operation cycle of the activated units and implicitly considers consumers' comfort.The state-shift time based random recovery approach is applied to mitigate possible load rebound after the load control,which avoids frequent activations of load control and preserves the lifetime of HVAC units.Based on the simulation results,the proposed strategy is demonstrated to provide reliable FR service with relatively quick response while maintaining consumers' comfort.Further,the aggregated HVAC loads can emulate a generator,such that the required spinning reserve can be reduced in general.3.To promote the research and application of DDR,a progressive load control strategy is proposed based on the response priority,in which both the HVAC loads and the electric vehicle(EV)loads are considered.In order to avoid the over response caused by the simultaneous action of a large number of loads,a coordinated PFR strategy is proposed based on the trigger frequency signal since several LAs are considered to participate in the FR together.The dispatch center calculates the trigger frequency signal of each LA,such that the LA will start the PFR process only when it detects that the frequency rises or falls continuously and the frequency deviation reaches the trigger frequency signal.In addition,a load control strategy for SFR considering the response delay is proposed,which prevents the excessive power compensation of DCLs.Each responsive load is switched on or off with a random time delay,during which if the frequency reaches the rated frequency,the SFR will stop immediately.The simulation results verify the fisibility and effectiveness of the proposed control strategy.The paticipation of EV loads can effectively share the SFR task of HVAC loads,and helps the system frequency recover to rated value faster.Overall,DCLs are an effective supplementary approach for improving dynamic performance and the new steady-state frequency of the studies power system.4.A DR aggregator operation framework is proposed dealing with the interaction between the aggregator and customers.Three types of DR contracts,namely LC contracts,LS contracts and FCL contracts,are designed which can be customized.In terms of the responsive load,consumer behavior is innovatively modeled through the consumer psychology in order to reveal the relationship between the incentives and the expected customer response.A multiobjective model for the aggregator to maximize both its profit and the customers' welfare is proposed which encourages the positive enrollment of potential DR resources.The proposed model is a multi-objective integer-programming model,which is solvable for Non-dominated Sorting Genetic Algorithm II(NSGA-II)after reformulating.A comprehensive analysis for several case studies demonstrate the feasibility of the model and the flexibility provided by DR contracts that enables the aggregator to participate in the electricity market.