Studies On Co-optimization Of Reserve Allocation For Supply/Demand Sides Based On Modeling Of Air Conditioning Loads

To deal with increasingly prominent issues,including energy crisis and environmental pollution,many countries are actively exploring and utilizing renewable energy such as wind and solar energy.And accordingly,there are more and more renewable energy integrated into power systems and the proportion of traditional fossil energy decreases.However,more reserves are needed because of the stochastic and intermittent characteristics of the renewable energy in power systems and the higher requirement for reliability.If all these reserves are provided by means of traditional fossil energy,the environmental benefits from the renewable energy will be diminished and the generation efficiency will considerably decrease.To relieve the stress of the reserve supply by the generation side,the demand side reserve should be focused on.Air conditioning loads can provide reserves owing to their high proportion in the demand and thermal energy storage characteristics.With the development of smart grids,more mature instrumentation and measurement technology and two-way communication technology provide technical support for controllable load participation in power system ancillary services.Moreover,the national policy also supports the development of demand side response and there are many existing programs for load response at home and abroad.Therefore,air conditioning loads are feasible to participate in the reserve service.This dissertation focuses on the cooperative optimization for supply/demand side reserve based on modeling of air conditioning loads.Firstly,it is necessary to understand the operating characteristics of a single air conditioner and a first-order space thermal model is applied to describe the thermal process of the room,in which dynamic parameter identification is an essential problem considering the influence of the environment.Then.,the aggregate model is proposed based on coupled Fokker-Planck equations(CFPEs).Further more.we propose reserve allocation model with air conditioning loads considering lock time and hierarchical solving method based on Benders decomposition.Finally,we expand the controllable loads to central air conditioning loads and the reserve providing of central air conditioning loads is studied based on the test platform.The main contributions are as follows:(1)Window varying particle filter(WVPF)for time-varying parameter identification of space thermal model.The parameters of space thermal model are usually time-varying considering the influence of the environment.And accordingly,parameters should be identified in a dynamic way.The identification results of parameters are usually sensitive to measurement noise and initial value using conventional particle filter method.To overcome these issues,a modified particle filter algorithm,called WVPF,is proposed to identify time-varying parameters of space thermal model in an online way by adaptively changing the prediction time window in this paper.WVPF is proposed with improvements in prediction of particle swarm and weight update steps.Furthermore,a measurement system for split fixed frequency air conditioner is developed to collect data for parameter identification and to verify the accuracy of space thermal model.It should be noted that this system can also realize remote control of air conditioner.The identification results are accurate using WVPF.In addition,WVPF is not sensitive to measurement noise and initial value.(2)Aggregate model of air conditioning load based on CFPEs.Since CFPEs are partial differential equations,it is difficult to solve CFPEs analytically.Linear state equations,which can be used for control conveniently,are developed by solving CFPEs using the finite difference method(FDM).The grid spacings(including time step and temperature step)of difference scheme are obtained by analyzing numerical stability and convergence based on the maximal principle.The complete analytical form of the stationary solutions of CFPEs is derived.To obtain the stationary solutions quickly,a numerical method is proposed.Considering that the parameters may be heterogeneous,a classification method using dimension reduction is proposed.To avoid the limitations of point estimation.interval estimation is applied to describe the stochastic behavior according to the normal distribution,which is used to approximate the binomial distribution.Simulation results of point estimation and interval estimation are verified by Monte Carlo simulation.Regarding stationary solutions,the simulation results of analytical and numerical methods are almost the same.indicating that the methods proposed in the paper are effective.The aggregate model is successfully applied to an existing control strategy to follow the reference signal for regulation services.and the performance is good.(3)Hierarchical reserve allocation with air conditioning loads considering lock time An aggregate model of air conditioning loads considering the lock time is proposed and linear constraints of the air conditioning loads are developed.Among these constraints,lockout constraints are linear slack constraints for convenient in computation and the validity of the slack form has been proved.These constraints are integrated into the reserve allocation in dynamic economic dispatch.This problem is reconstructed as a three-level hierarchical problem,and Benders decomposition is applied.To increase the calculation efficiency,we propose three methods,which are adding necessary conditions,adjusting upper bound and applying parallel computing.The simulation results show that air conditioning loads can provide load reserve,and the lock time is necessary in reserve allocation.Simulation results verify the effectiveness of the proposed model and method.In addition,the efficiency promotion methods can increase the calculation speed significantly.(4)Modelling and control of central air conditioning loads to provide reserve based on the test platform for central air conditioner.By analyzing the operating theory of central air conditioner,a simplified model of the central air conditioner is established,including the coefficient of performance of the chiller,heat transfer process of the chilled water,heat exchange of fan coil and the space thermal model of terminal room.The controllability of each components of central air conditioner is also studied,and the control scheme of central air conditioning load to respond the power shortage accident is proposed.By remolding the power supply of the chiller and the oil pump,central air conditioning loads can quickly respond the accident and the safety of central air conditioner can also be ensured.After a period of time,the ampere rating of the chiller is restricted to avoid the load shock to the power systems while considering the users’ comfort.Based on the test platform for central air conditioner,parameters of central air conditioner are identified.The results verify the effectiveness of the model and the identified parameters.Further,control of central air conditioner is conducted,which verifies the feasibility of the central air conditioning loads to respond the power shortage accident.Test results also show that the control on central air conditioner does not affect users’ comfort seriously.