Research On Power System Optimal Despatch Considering Source-demand Interaction

With the advancements of society and modern technology,the electric power industry has been in a sustained and stable development,power grid has also been gradually changed from the traditional mode to the intelligent one.Under this background,the power sources not only rely on the conventional energy resources,but also include more renewable energy resources.In addition,power electricity consumers are no longer passive rigid loads.In contrast,they are cooperative with response strategies from power operators.The mutual transformation of energy source structure,power grid mode and power demand type paves the way for the sourcedemand interaction.Meanwhile,modern control technology,communication technology and sensing technology further provide technical support for source-demand interaction.However,with a source-demand interactive mode,more challenges and requirements have been brought into the research on power system optimal dispatch.On the other hand,electricity market is becoming an effective approach to stimulate the source-demand interaction.To further promote the benign interaction of participating units from source side and demand side under marketoriented environment is also a trend of the research on power system optimal dispatch considering source-demand interaction.Thus,it is of great importance to explore the sourcedemand characteristics and utilize the electricity market mechanism on the optimal dispatch related researches.This paper is focused on power system optimal dispatch,combining the source-demand interactive mode and electricity market mechanism.It consists of new power flow computation methods,power system security assessment and optimal dispatch under market environment.The details boil down as follows:(1)Power flow computation is the basis of power system researches including optimal dispatch.With a source-demand interaction,more uncertainties appear in power systems.The conventional deterministic power flow computation method cannot consider the uncertainties from both the variables and the interactive process.In contrast,the probabilistic power flow method is capable of dealing with this issue.The relationship between Nataf transformation and Gauss-Hermite integration is explored in this paper.Based on Gauss-Hermite integration technology,an improved multi-point estimate method is proposed through combining Nataf transformation and point estimate method(PEM).Both the fluctuations of wind power and the stochastic characteristics of loads under different distribution patterns are considered.The multi-point estimate method has a higher precision than conventional PEM under the scenario including a large number of non-normal distribution variables.(2)The security is one of the most important indices in power system optimal dispatch.The source-demand interaction,along with the fluctuations of renewable resources,imposes more requirements on the security assessment in the power system dispatch process.In this paper,a set of composite security indices,which are derived from the Hyper-box and Hyperellipse space theory,are extended by probabilistic power flow method to model multiple probabilistic scenarios under uncertainties.In addition,with an interval-number sorting technology,the dynamic indices are promoted to form a composite assessment approach for power system security.(3)According to the composite security assessment indices,a security-based active demand response(DR)strategy is proposed in this paper.The proposed strategy is able to provide expected active DR capacity based on the forecast wind power fluctuations.Also,it can quantificationally reflect the impacts of active DR on wind power consuming and system security.(4)In the source-demand interactive mode,considering both security and economy has become the key to the research on power system optimal dispatch.In this paper,a two-stage dispatch strategy considering source-demand interaction is proposed.In the first stage,a multiobjective optimal dispatch model including security and economy is established based on the composite security assessment indices.The multi-objective optimal dispatch model is solved by NSGA-II method.The relationship between security and economy is presented under two dispatch schemes.In the second stage,an amendatory intraday dispatch strategy considering wind power underestimate/ overestimate,thermal power unit adjustment and active DR is proposed.The impacts of interactive response on wind power consuming and daily cost are also analyzed,which can provide a basis for designing relevant interactive response mechanism in specific regional power grids.(5)With the development of electricity market,power system optimal dispatch consists of more features which are significantly different from those in the conventional optimal dispatch.In this paper,a locational marginal price(LMP)theory based scheduling model is established from the perspective of market participants.It is a bi-level day-ahead scheduling model including grid-level ES and IBDR-VPP.Furthermore,this scheduling model is extended to the intraday market,forming a remedial strategic rescheduling approach for the daily profits of market participants.The approach can not only analyze the impacts of interactive units' behavior on peak-shaving function,but also provide the market participants with loss reducing assessment.With the remedial strategic rescheduling approach,the market participants can adjust their flexible units to deal with the coming contingencies.