The employment of flexible electric loads such as electric vehicles (EVs) in power system optimal dispatching could improve the operation economics of the power system concerned. For this type of load

the electric power company or related management agency should give appropriate economic incentives. Since neither the EV aggregators nor the electric power company are sure about the profits or costs of the other side for scheduling the EV charging loads

a negotiation process can be introduced to work out reasonable economic rewards. Against this background

the negotiation strategies between the EV aggregators and the power company are studied for the participation of EV in day-ahead optimal dispatching. First

the optimal dispatching model considering the participation of the EV aggregators and the charging load model for the EV aggregators are developed. The negotiation bidding strategies and the bidding adjusting strategies between the EV aggregators and the power company are proposed next based on their expectations of possible economic revenues of the power company and possible losses suffered by the EV aggregators through dispatching the EV charging loads. Finally

with the modified IEEE 30-bus system as an example

the negotiation strategies developed are simulated and analyzed to account for the basic characteristics of the strategies. This work is supported by National Basic Research Program of China (973 Program) (No. 2013CB228202)

National Natural Science Foundation of China (No. 51361130153

No. 51361130152) and State Grid Zhejiang Electric Power Company (No. 5211DF13500M).