The Effect Of Operation Strategies For CCHP System On The Extent Of Demand Response

The purchase and sale of electricity between the CCHP system(Combined Cold Heat and Power,CCHP)and the grid under different operation strategies can affect the shape of load curve of the grid-side bus,thus producing certain economy effects and participating in demand response at the same time.The strategies of how to participate in demand response,and how to improve the economy of CCHP system belongs to different decision-making levels,thus the paper establishes the evaluation level of demand response as the upper target,and takes the economics of CCHP system as the underlying objective to make a bi-level optimization model.Different from CCHP system under the strategy of "Following the Power Load"and "Following the Heat Load",CCHP system under the strategy of "mixed operation" don’t have additional restrictions with heat and electricity output,and is not influenced by thermoelectric coupling,thus it has more space to participate in demand response.The paper establishes an economy model of CCHP containing fuel costs,electricity cost and auxiliary boiler fuel costs.Using "0","1" variable to represent the "Following the Power Load" and "Following the Heat Load" strategy respectively of CCHP system at each time,then the two decision variables of heat and electricity in "mixed operation" strategy can be simplified and easy to find the optimal solution.Demand response is produced by the unbanlance of power load and generation and amounts.Demand response can realize peak shifting.However,conventional indexes of load characteristics can hardly characterize the improvement extent of load curves.Thus,the evaluation index of demand response based on stationarity measure of time series is developed.After using marginal values to describe the real-time variance of power load,unifying marginal values with per unit system and improving stationarity measure of time series,the author computes the radius of neighborhood of the stable set which consists of marginal values from load curves.The radius of neighborhood mentioned above is defined as the radius of marginal neighborhood of load curves and used as index of load curves stability to evaluate the demand response.Taking the minimum marginal neighborhood radius index as the upper optimization target,and the minimum economy costs of CCHP system under the"mixed operation" strategy as the lower target,the paper builds a bi-level optimization model.Based on the branch-bound method and particle swarm optimization(PSO)algorithm,it find the solution of the bi-level coupled model to solve the coupling of electrical output in the upper and the lower target,and to solve the thermoelectric coupling in the the lower target within CCHP system.Final it is concluded with the optimal operation strategies considering the decision-making variables and thermoelectric coupling of CCHP system.