Active Power/Frequency Control In Power System Considering The Flexibility Of Load Response

Traditionally,the active power and frequency regulation process in power system is adjusting the generation output with standby resources to track the load change.Since the load forecast is solved in advance and the unit commitment of the power system is determined,the impact of the random variation of load fluctuation is controllable.However,as the structure of power supply begins to change,especially when the ratio of nuclear power,wind power and other intermittent power generation continues to increase,the required capacity of standby reserve to complement the supply and demand balance is also growing.If the power generation side can only rely on the standby resources for system operation,a considerable part of the thermal power unit generating capacity will be wasted and will incurs great environmental costs involved by the frequency control.Under this circumstances,more research began to focus on the potential of demand response from the load side.There are a lot of load resources which are of flexible controllability in the power system,such as TCLs,fridges,lighting loads,PEVs and so on.Load resources is responsive for system demand and makes the system frequency in control under the random fluctuations.The utilization of load frequency control resources mainly concerned about how to integrate the potential values of load resources,secondly,is to consider the side effect of control to users,like switching instant demand or cutting demand directly.If there is no indemnifying measures for negative effects or the measures are too vague,the participants will become indifferent in system planning.Take the LED lighting load and the energy storage PEV load as example,the different character of users' demand is analyzed,and the loads demand control are integrated into the power system active power/frequency regulation process.The finished work and achievement are as follow:1)On the basis of LED individual model and the monte-carlo load modeling,this paper proposed an active control strategy of LEDs to participate the system frequency regulation.First,a led power-illumination characteristic model is established in this paper.Every users' comfort of controlled member have been considered in the standard illumination condition.By using monte-carlo sampling,a LED lighting loads model is proposed.LED loads are categorized into 3 groups:Local lighting,Indoor lighting and Street lighting group.Then,the LEDs categorized by different groups are subject to different control strategies.With standard illumination range to dimming control,LED will actively participate demand respond according to local frequency signals and adjust its power demand.At last,the cases in interconnected system model verified validity of LED participation in AGC frequency regulation process.2)A static economic dispatch involving PEV loads control is designed.The strategy proposed a cooperative generation-load optimization model on the basis of economic dispatch.The mean-field game method is applied to optimize the bottom layer PEV's charging control.An interactive mechanism system is established between the layers to ensure the consistency of optimization from different layers.The information access,process and interaction problem is solved in the economic dispatch process.The optimal dispatch problems for PE Vs and dispatch center are decoupled and then united.In the end,the problem is finely tuned at different layers.This paper applied MFG method for PEV charging control and information interaction.The rigorous method(IPM optimization)is applied to solve scheduling problem.With a few times of iteration,the system obtained an accurate solution which is a Nash-equilibrium.The cases proved benefit of MFG method in bottom layer optimization.The feasibility of cooperative optimization is discussed.3)Considering the controllable loads as an economic resource,integrating the LED loads and PEV load into the traditional AGC,this paper proposed an AGC model with participation of two responsive loads.At primary frequency regulation time scale,LED loads proceed decentralized response.Changing the users' demand according to the frequency signals,the power grid will save capacity for primary regulation.At secondary frequency regulation time scale,to realize frequency control,the economic cost of system resources is considered to determine the power dispatch of different resources.At every sampling period,by MFG method,PEV loads respond to the incremental cost of power consumption.During the AGC period,PEV responsive loads cooperate with generation reserve to realize secondary frequency regulation.The case study adopt IEEE 3 machine 9 node system,considered AC network constraints.The simulation results showed the effectiveness of integration of controllable loads with traditional AGC strategies.