Research On Coordinated Optimization And Dispatching Strategy For Clustered Charging Loads In Urban Distribution Networks

As one of the important ways to reduce greenhouse gas emissions and ease energy tension,the large-scale promotion of electric vehicles(EV)will bring positive effects in energy saving and emission reduction,clean energy,fuel substitution and green environment protection,etc.With the economic development and electrification of transportation system,the demand for EVs is bound to grow.However,the charging behavior of EVs in clusters is affected by subjective factors of users,which has the complex characteristics of randomness and disorder,and the charging load characteristics with strong randomness and overlapping peak effect are formed at the level of distribution network,which will bring risks to the safe and stable operation of urban distribution system.Therefore,how to control and optimize the charging load of EVs is an urgent problem to be solved.Based on the above background,this paper first analyzes the impact mechanism of cluster EV charging load access on urban distribution network,then proposes an optimal management strategy of regional charging load optimization considering load scheduling potential and aggregator game based on demand response mechanism,and finally proposes a charging load consumption strategy based on flexible interconnection mechanism with cooperative operation of “source-storage-charging.(1)The form and characteristics of EV charging system connected to urban distribution network are explored,and the impact of charging load on the load characteristics,distribution substation load and three-phase balance of the distribution network is quantified and analyzed.The changes of electrical quantities when the charging system is connected to the distribution network under fault disturbance and the impact on fault protection are studied.(2)A charging load optimal scheduling strategy based on the load aggregator game is proposed.The strategy establishes a three-level control structure of grid-load aggregatorcharging users,and a dispatchable potential evaluation model considering the travel pattern and two-stage charging characteristics of EV users.The non-cooperative game optimization of aggregators at the coordination level is carried out with the objective of maximizing the interests of each load aggregator,solving their optimal bidding strategies,and setting a rebound buffer strategy for charging loads after the demand response ends.The algorithm verifies the applicability of the proposed model and method.(3)A charging load consumption and promotion strategy based on flexible interconnection mechanism and coordination of "source-storage-charging" is proposed.Firstly,the load absorbing mechanism based on the synergy of "source-storage-charging" and flexible interconnection is analyzed,and the mathematical model of flexible interconnection is established.Secondly,a dynamic power flow model of active distribution network based on multi-terminal flexible interconnection is established by fully considering the adjustable factors of active distribution network,and strict multi-section operation constraints are set.Finally,the model is optimized by second order cone transformation and linearization.An example is given to verify the effectiveness of the proposed strategy and the optimization stability of the model.