Medium-and Long-term Optimal Dispatching Method Of Cascade Hydropower Plants Considering Contract Energy Decomposition

Hydropower energy dominates in the southwestern region of China.The provincial market is mainly based on medium-and long-term transactions,supplemented by short-term transactions.Hydropower medium-and long-term market transactions are mainly completed in the form of annual and monthly bilateral negotiations.As a result,it is difficult to balance market shares of different time scales when formulating medium-and long-term transaction scheme.In this paper,the cascaded hydropower station in the middle and lower reaches of the Lancang River is regarded as the research object.It is assumed that hydropower stations participate in prior transmission,west-to-east power transmission,and provincial market trading.The provincial market trading is reduced to annual and monthly bilateral trading.And the west-to-east power transmission is reduced to the prior transmission quantity in the agreement.The information on the quantity and prior transmission quantity in the agreement is known.It is focused on the optimal operation of cascade hydropower stations in mediumand long-term market,mainly including the following aspects:(1)Consideration of medium-and long-term optimal scheduling methods for cascade hydropower stations with uncertain quantity and price.In order to solve the problem of mid-and long-term generation scheduling and trading scheme of cascade hydropower station,an optimal scheduling model with the goal of maximizing generation benefits is established.In this model,multiple groups of incoming water scenarios are randomly generated by the annual average inflow flow;the provincial market electricity price function is fitted based on the relationship between electricity quantity and electricity price;the electricity generated after deducting the prior transmission electricity is allocated to different types of transactions;and the market price and benefits are determined according to the shares of different types of transaction electricity.In order to maximize power generation benefit,the hybrid algorithm of stepwise optimization and successive approximation is used to solve the combinatorial cycle of power output and quantity.The equalizing-progress distribution method is introduced as a comparison scheme.(2)Consideration of medium-and long-term transaction optimization methods for cascade hydropower stations with electricity price risk.In order to solve the risk problem caused by the prediction error of the medium and long-term market price of cascade hydropower station,the medium and long-term transaction optimization method considering the price risk is proposed.This method can reasonably balance the relationship between the benefits and risks of cascade power stations and determine the best transaction combination scheme.In this method,multiple groups of incoming water scenarios are randomly generated by the annual average inflow flow;and three kinds of market transaction situations are used to fit the provincial market price function;the power generation after deducting the prior transmission electricity is allocated.In order to make medium and long-term trading scheme,the utility value maximization model of coupling benefit and risk is established by the portfolio theory.The benefit risk is represented by the benefit deviation caused by the electricity price prediction error of the bilateral trading market.Value at risk theory(Va R)is introduced as a risk analysis and comparison scheme.(3)Analysis of the influence of different factors on the trading results.There are differences in the ways of making trading scheme considering benefit-risk and not considering benefit-risk,which are mainly reflected in the final benefit of each power station,the market share of traded electricity,and so on.At the same time,the constraints set by cascade power stations and the different importance of benefits and risks when considering risks also have a great impact.Therefore,the benefit maximization model and the utility maximization model coupled with yield-risk construction are selected as the research models.The trading results of the two models are compared through the benefits and risks of a cascade power station,the market share of traded electricity,the optimal distribution range of annual electricity,the rate of benefit,and the degree of emphasis on benefit-risk.The influence rules of different factors on trading results are analyzed.