Network Planning And Optimal Dispatch Strategies Of Active Power Distribution Systems

With increasing utilizations of distributed energy resources and smart energy apparatuses,power distribution systems are undergoing a transition from passive to active and smart ones,which imposes challenges for distribution system operators in many aspects,including network planning and optimal dispatching.On this basis,the CIGRE6 study committee gives a definition of active power distribution system(APDS):distribution networks that have systems in place to control a combination of distributed energy resources(DERs).Distrbution systems operators have the possibility of managing the electricity flows using a flexible network topology.DERs take some degree of responsibility for system support,which will depend on a suitable regulatory environment and connection agreement.Given this background,this dissertation carries out some systematic research work on an APDS,as summarized below:(1)Expansion planning for active distribution networks considering deployment of smartmanagement technologies.First,a multi-stage long-term network planning model is proposed for the active power distribution system.The objective function is to minimize the system investment and operating costs in a coordinated manner over an established horizon.The planning model determines the follows construction options:upgrading substations,reinforcing and/or constructing cable circuits,placing voltage regulators(VRs)and/or static VAR generators(SVGs),and determining the connection points for distributed generators(DGs).During the planning cycle,the investment strategy is implemented in several stages,and the operational strategies of the system are determined according to different scenarios at each stage.In order to expedite the solution speed,the original model is transformed into a mixed integer quadratic programming(MIQCP)model by linearization and approximation techniques,so that the off-the-shelf solver can be invoked to solve the problem efficiently.The effectiveness of the proposed planning model is verified by a test system(2)Coalitional Game Based Transactive Energy Management in Local Energy Communities.The so-called local energy community(LEC)is a vital element of APDS.Thus,the energy management in a local energy community is studied using the cooperative game theory.Specifically,the participants in a LEC form a grand coalition and then the collective revenues are distributed according to some rules.The work is summarized as follows:First,the balancedness and superadditivity of the model are proved.Then,the revenues are allocated to every player based on the nucleolus solution to ensure the fairness and effectiveness.It is worthy to note that the uncertainty of renewable energy power output is considered in the model,and the Rayleigh distribution is taken as an example to simulate the output of renewable energy.The closed-form expression of the expected value of the income function is taken as the objective function.Case studies shows that the cooperative game can effectively improve the total revenues of LEC and to a certain extent improve the load characteristics of LEC.(3)Transactive Price Determination for Optimal Demand Response in Power Distribution Systems.With the development of advanced communication technology,real-time pricing scheme has increasingly become the non-negligible means of energy management for APDS.The bilevel optimization model is used to design the price signal by taking into account the energy price in wholesale market and the participation level of the demand response.The model could offer the retailer energy procurement strategy by inducing the responsive load to adj ust the consumption behavior,and thereby achieve the social benefit maximization.In the upper model,the electricity utility company determines the energy procurement strategy based on the forecast values of the electricity price in the wholesale market and calculates the price signal to adjust the power consuming behavior of the end users.In the lower level,each end user adjusts the consumption pattern according to the price signal to maximize the self-interest.By using the KKT conditions to represent the optimality of the lower level model,the bilevel model is transformed into a mixed integer quadratic programming problem.And case studies illustrate the effectiveness of the proposed model and method.(4)Decentralized Short-term Voltage Control in Active Power Distribution Systems.The static voltage control in a short-time scale in APDS is studied in this section.The active power and reactive power in the system is co-optimized to ensure that the system nodal voltages be maintained within a specified range.The network loss minimization and voltage deviation minimization are included in the objective function.Through relaxing the non-convex branch flow model,a second-order cone programming model is formulated in this section.Then,through decoupling networked components or entities,the model is solved by the Alternating Direction Method of Multipliers(ADMM)algorithm in a distributed fashion.Lastly,IEEE 33-and 123-bus test systems are employed to demonstrate that the expected nodal voltage magnitude ranges are well maintained by employing the developed method.