Studies On Theory And Algorithm Of Advanced Dispatch In Power Systems

With the expansion of grid scale,the introduction of market competition mechanism, the customer's higher requirement of power supply reliability and the increasing concerns about environment and energy issues,the power system advanced dispatch theories and algorithms are facing new challenges.Among these challenges,the spinning reserve allocation becomes the research focus because of its direct connection to power system operating reliability and economy.For advanced dispatch,more spinning reserve means higher operating reliability,but the operating economic objective will be inhibited at the same time,and vice versa.Further,the operating reliability level will be different when the same spinning reserve capability is allocated to different generators.In previous studies,the deterministic methods for spinning reserve allocation are easy to understand and implement.However,it is hard to quantify the relationship between the spinning reserve and system operating reliability as well as to find out the cause of spinning reserve.All these will result in improper spinning reserve allocation and spinning reserve responsibility allocation.Therefore,the traditional deterministic spinning allocation methods cannot satisfy the requirements of the power system deregulation.Especially,the increase of intermittent renewable power sources in power system intensifies the conflict between system operating reliability and economy. Therefore,in the current situation,taking spinning reserve allocation into account and focusing on the coordination of power system operating reliability and economy,to propose new advanced dispatch model and algorithm,which can follow power system changing trend and be suitable for electrical market operation,has significant theoretical and practical meanings.As mentioned above,this thesis around spinning reserve allocation problem, reviewing the history of advanced dispatch,aiming at the shortage of current advanced dispatch method,based on economic theory,using optimization skill, does thorough research on advanced dispatch.The main contribution of this thesis can be extracted as:(1) Aiming at the shortage of traditional deterministic advanced dispatch,an advanced dispatch method named advanced dispatch with equal response risk is proposed in this thesis.Probabilistic spinning reserve allocation method is used in this method.The response risk can be kept in the pre-defined level using this method.The expected demand not supplied(EDNS) index is used here to quantify the relation between the spinning reserve allocation and system reliability level.In the context,the EDNS is reformulated to be suitable for being incorporated into traditional advanced dispatch as a constraint through introducing {0,1} variables to its express.In this way,the dispatch process and the response risk estimate process can be incorporated.The resulted model is a mixed integer optimization problem.Additional constraints for {0,1} variables are then bounded to the original problem to converse mixed integer optimization problem to quadratic optimization problem to use traditional available quadratic optimization programs.And this accelerates the calculation of the model.Focusing on how to specify the system operating reliability level in advanced dispatch with equal response risk method,an advanced dispatch method considering customer interruption costs is proposed.Expected energy not supplied(EENS) and interrupted energy assessment rate(lEAR) indices are introduced here to assess the expected customer interruption costs(ECIC).In the proposed method,the expected customer interruption costs because of spinning reserve insufficiency are added to the objective function.Through this way,the predetermined operating reliability level is no longer necessary.Instead,the optimal reliability level as well as spinning reserve allocation can be decided during the optimizing progress.Further,physical and algorithmic decomposed methods are cooperated to solve the quadratic optimal problem which results from original {0,1} mixed integer optimization.Based on advanced dispatch considering customer interruption costs method, an advanced dispatch method considering network security constraints and customer interruption costs is proposed.The time-coupled constraints, space-coupled constraints and state-coupled constraints are included in the model which is more practical for power system operation.The pre-contingency active power outputs,post-contingency active power outputs and post-contingency load shedding are treated here as independent variables in this method.Because of the large size of the model,a decomposed method for solving primal-dual interior point KKT condition,which makes full use of weak coupled nature in time-coupled and state-coupled constraints,is proposed.This method can speed up the calculation,and enhance the effectiveness of the proposed method.Based on analysis of cap-and-trade greenhouse gases emission control policies,a compromising advanced dispatch method under cap-and-trade framework is proposed.The proposed method takes greenhouse gases emission into account,and this is suitable for power system energy conservation and emission reduction requirements.An emission affection factor is deduced using fuel price,emission allowance price and emission character of generators.The emission affection factor can be used to modify the generator's generation-cost curves.For the proposed method,no additional constraints are needed,and the only change of advanced dispatch model is to modify the objective function with emission allowance factors,so the method is easy to implement.To sum up,absorbing the advantages of current researches,this thesis develops advanced dispatch in model and algorithm,tradeoff between response risk and operating economy and relationship between operating reliability and decision.However,facing the quick development of current complex power system,there are still many works to do,such as the calculation of power system components fault rates in real-time,power system operation economic rules,as well as energy utilization strategies.