Studies On Several Important Problems Of Bilateral Transactions In Electricity Market

Interregional power exchange, interprovincial power exchange, and direct power purchase by large consumers, are all bilateral transactions mode. They will largely exist in a more open electricity market in the future. Bilateral transaction seems to be the trend in the near future. Therefore it will be of great significance to analyze the various issues of the bilateral transactions. Now world-wide studies primarily focus on aspects as allocation of transmission losses and congestion cost, as well as on design of market mechanism and regulation. While other studies are not adequate on the following as game playing strategy, negotiation strategy based on multi-agent, congestion management and stimulation.The paper aims to explore the bilateral transactions in electricity market and focuses its study primarily on the following aspects:1. Negotiations between different traders of bilateral transaction are simulated by utilizing multi-agent technology. The Q-learning algorithm based on previous quote data is adopted to strengthen the agents'self-learning capacity. Hence the agents could react timely to their opposite parties. Meanwhile, in order to keep the fair competition, a two-stage negotiation mechanism of“negotiations + auction”is proposed, giving one more opportunity to the generator agent with some cost advantage but used to fail due to the underestimation of the negotiations. Also, the actual diversity of different generating cost is reflected by contract power price so as to inspire the generators to gain initiatives by lowering their costs.2. Based on Nash equilibrium theory and through the introduction of generators'cost matrix and vector of expectation to pay, the bidding strategies have been established for multiple market participators in bilateral transaction in electricity market. The model is solved by genetic algorithm with strong global searching ability. Simulation results show that the model is effective and practical, and can always get the Nash equilibrium strategy combination with the smallest total cost, which can maximize the benefit of each market participator. Meanwhile, the strategy also reflects the effect on market caused by generators'strategic bidding.3. A coordination mechanism of electricity supply chain, based on the cooperative game, is proposed to make both the buyer and the seller to undertake the risk of quantity deviation between the actual demand and contract quantity together. With this mechanism, the generators made their pricing strategy according to the principle of maximizing the profits of the supply chain, and optimizing the ordr quantity by counter purchase policy. In addition, it can ensure both sides to gain satisfactory profits respectively. Pareto optimality is finally achieved in electricity markets.4. A congestion management framework in bilateral electricity market is proposed based on interruptible load auction model. The optimal load shedding quantity was identified by market mechanism. Under the proposed framework, the procedure of dispatch can be identified as 3 stages: pre-dispatch, unconstrained dispatch and congestion dispatch considering interruptible loads. The customers could submit their interruptible load bidding curves to ISO at the third stage. The congestion dispatch model is set up, considering syntheticlly the minimization of the interrupted loads and the payment to customers who provide interruptible load services.5. Based on the swarm platform, some models are set up as the market model of bilateral trade, the buyer and seller model, and the learning model of intelligent agent. The paper investigates the practice of swarm platform into simulation of bilateral trade so as to realize the dynamic control and the real-time observation within the simulation. It also attempts to establish the learning models as intelligence inference and RE, and analyze the convergence rate and convergence price and so on.6. Several issues have been attentively examined as the present situation of bilateral trading modes and price formation mechanism for power transmission from the western region of South China power grid to its eastern region in southern electricity market. Besides, the paper introduces and evaluates the bilateral trading modes and price formation mechanism under the current situation of buyer's monopoly mode to design the bilateral negotiation mode. Trading platform on different bidding mode and market-driven mode are analyzed, and main problems are pointed out.. The paper also attempts to thoroughly analyze the impacts of different interest groups such as the grid companies, generation companies, large customers and local economy by direct power purchase with larger customers. Some suggestions are then presented.Finally, several conclusions are reached briefly and future research are expected.This paper is supported by the National Social Science Foundation of China (No. 04CJL012), the Program for New Century Excellent Talents in University (No. NCET-08-0207) and the Key Project of Chinese Ministry of Education(No. 109128).