Research On Microgrid Economical Scheduling

As the current international and domestic economic situation and energy situation is undergoing profound changes,the energy revolution represented by Internet technology and new energy technology has begun.With rapid development of distributed generation(DG),microgrid(MG)is an effective way to absorb DG.In order to achieve reliable and economic operation of MG in grid-connected or islanded mode,it’s necessary to minimize the negative impact of intermittent energy to MG.And it’s also important to make full use of DG output,develop interaction potential of load demand,and improve power supply reliability and power quality.So that an effective energy management makes great significance to MG.This paper focuses on several issues in MG economical scheduling.The main work and achievements are as follows.1)An interaction load model was established,including shiftable load,curtailable load and transferable load,which was applied in MG day-ahead economic scheduling under the interaction environment.First,the proposed model for shiftable load was described by integer variable and power distribution vector,which immensely reduces the model scale.Second,the involved model for curtailable load considers interaction frequency and duration.Third,the one for transferable load regards transferable timespan.Even more important,the model remains linear;as a result,the solution is independent of initial points when solved by an optimization solver.The contents of customer interaction contract were discussed.A case was performed to verify the proposed model.2)A mixed integer programming model,which can be used in MG intra-day scheduling,is put forward.The model of storage battery charge/discharge process,which considers charge/discharge cycles and aging cost,is proposed.Compared with the conventional model for MG economical dispatching,the linearized constraint model,such as power flow with voltage amplitude limitation,branch capacity based on Cartesian geometry,transferring power and power factor of point of common couple,and et al,is established.The numerical cases are studied to verify the proposed model.3)A MG economic dispatching model which considers the power characteristics of distributed power is established in this paper.The model,which linearizes P-Q capacity limitation of DG based on analytic geometry,is solved.Such that it can effectively take the power characteristics of DG with voltage source inverter,doubly fed induction generator and synchronous generator into account.In the framework of multi time-scale MG economic dispatching,the proposed model is verified on a MG system.4)The three-phase MG economic dispatching model which considers harmonics power flow is established in this paper.Firstly,the optimal three-phase power flow model of MG with DG is analysed.Then the harmonic equivalent models of electrical devices and harmonic source are established to calculate three-phase asymmetrical harmonic power flow.Finaly,considering decreasing three-phase disequilibrium and total harmonic distortion in MG,the proposed model is verified on a MG system.