Research On Operation Strategies And Planning Methods For Multi-type Microgrids Under Uncertainties

As an effective approach of comprehensive utilization of distributed renewable energy sources(RESs),microgrids(MGs)are facing a broad development prospect under the general trend of energy transformation.In the meantime,cyber physical systems and advanced control technologies are driving MGs to reshape and develop in multiple type to enrich their application scenarios.Under this background,the conventional research methods for distribution grids,such as such as planning theory,scheduling framework,optimization modeling,will face both applicability and rationality challenge.Hence,it is of great significance to carry out relevant research on operation and planning cosidering different operation control modes and communication characteristics of microgrid.This paper aimed at the scenario of the significant increasing uncertainties due to high shares of RESs integration,the operation and planning of multi-type MGs are studied by focusing on the optimization modeling and solving algorithm.The main work is listed as follows:(1)In order to evaluate the safety of grid-connected MGs,over-limited probability of voltage,confidence voltage range,and over-limited probability branch power are put forward as the key indices for the safe operation of MGs.Considering the change of operation characteristics caused by the point of common coupling(PCC)voltage control for distributed generation+energy storage,extending QV bus-type is adopted to describe the operation feature of PCC reasonably.On this basis,a probabilistic load flow(PLF)with QV bus-type is proposed for the first time,which enriches the bus types of PLF and realizes fast online evaluation of operation state of grid-connected microgrid.The simulations are conducted to verify the accuracy of the proposed PLF model and algorithm,and also shows the proposed evaluation indices and method can effectively quantify the risk of MGs operation and identify the weak buses of the system.(2)In view of the shortage casused by adopting sigle spinning reserve for islangdes MGs(IMGs)with high shares of RESs,a generation-load-storage collaborative reserve system is proposed.Based on the system,a day-ahead optimal scheduling model of joint power-reserve considering considering risk-based reserve decision is established.The conditional value-at-risk theory is introduced to measure the operational loss caused by insufficient reserve.A novel forecast errors model of RESs and load is presented by considering the correlation among forecast errors,and the Latin hypercube sampling with correlation is used to generate the scenario of forecast errors,so as to greatly reduce the dimension of the traditional MCS.The simulation results show that the proposed optimal scheduling model joint power-reserve can effectively alleviate the reserve shortage caused by the high share of RES and also improve the safety and economy of IMGs.(3)Aiming at the vacancy of PLF analytical method and the lack of coordinated planning theory of active-reactive power resources for peer-peer controled IMGs,firstly,an analytical method based on cumulants considering the correlation of input variables is proposed to solve the PLF for peer-peer controlled IMGs.Nataf transform is used to deal with the correlation,and the PLF is solved using the cumulant method and the Gram-Charlier series expansion.Then,a multi-objective coordinated planning model of active-reactive power resources is presented considering annual comprehensive cost and operation risk simultaneously.The Pareto optimal solution set is found using non-dominated sorting genetic algorithm-II(NSGA-II)to provide a set of alternative planning schemes.Case studies verify the accuracy of the proposed PLF analytical meothod,and comparative analysis of planning schemes also shows the effectiveness and rationality of the established planning model.(4)To solve the real-time power dispatch problem of islanded multi-microgrids(IMMGs),a decentralized cooperative dispatch framework is proposed.Based on the multi-agent consensus theory,the real-time economic dispatch problem of IMMG is changed into the regulation cost consensus problem to realize the distributed collaborative power dispatch.According to the operation characteristic of each dispatchable unit,priority-based collaborative dispatch strategy is proposed,and then the regulation cost function of MGs is constructed.In order to optimal configuration of dispatchable active power resources,a bi-level model that couples the planning and operation problems of IMMG is established.In the model,more detailed models are proposed for the regulation costs of various dispatchable units.Consensus algorithm is embedded in multiple population genetic algorithm(MPGA)to solve the bi-level model.Case studies demonstrate th effectiveness and superiority of the proposed model and dispach strategy.The research results of this paper enrich the theory and method of optimization modeling and solving of MGs,and have broad application prospects in the field of generation-grid-load-storage collaborative optimal operation and planning.The work was supported by the National Natural Science Foundation of China(51777077)and the Natural Science Foundation of Guangdong Province(2017A030313304).