Research On Distributed Optimization Method For Operation Control Of Active Distribution Network

With the continuous development of new energy technology,the permeability of distributed power supply in distribution network is increasing.The traditional distribution network system has changed from passive one-way power supply network to active power twoway flow network,which makes the operation and control of distribution network face many new challenges.The cost of maintaining reliable operation of distribution network by means of network upgrade or operation structure change is high and passive,which will no longer be applicable.Using active strategy to control and manage distributed controllable resources in distribution network has become the main means to optimize the system operation mode and improve the penetration of renewable energy.In 2008,the concept of "active distribution network" was put forward by the International Great Power Grid Conference.It is of great significance to promote the development of clean energy,improve the permeability of new energy in distribution network,and improve the reliability and economy of distribution network.However,most of the power generation units in ADN are not owned by the grid company,and the need to protect data privacy makes traditional centralized optimization operation control methods challenging.Therefore,the research on distributed optimization of ADN operation control has very important theoretical significance and engineering value.Based on an idea of coordinated zone control and convex optimization,a distributed optimal reactive power control method for active distribution network is proposed.This method takes network power loss as objective function,and the constraints are power flow equation,upper and lower bounds of bus voltage and reactive power output of distributed generation.Thus a non-convex optimal reactive power control problem is transformed into convex quadratic programming problem with simplified branch flow equation,and the convex quadratic programming problem is solved with distributed calculation in form of physical partition.The system is divided into several sub-areas,each sub-area is equipped with a controller,and each controller only measures data of its own area and collects boundary coordination information from adjacent controllers.Through this distributed optimization calculation with synchronous alternating direction method of multipliers,the controller of each area obtains optimal reactive power control strategy for distributed generation.Finally,with case study in IEEE 33-bus system and IEEE 69-bus system,correctness and effectiveness of the proposed method are verified and the partitioned distributed reactive power optimization control of ADN is realized.Considering the uncertainty of renewable energy output,a distributed robust optimal dispatch model for ADN is established.Firstly,the AC power flow equation is linearized,so the approximate linear relationship between node voltage and injection power is obtained,and the approximate linear expression of node voltage security and line current security constraint is derived.Secondly,by using dual optimization theory,the robust optimal dispatch model is transformed into a quadratic programming model without uncertain variables.Then,the quadratic programming model is separated into sub-optimal problems of the distribution network side and the controllable resource side,and the sub-optimal problems are solved in a distributed way using alternate directional multiplier method.Finally,with the case study of modified IEEE33-bus system and IEEE 69-bus system,correctness and effectiveness of the proposed method are verified,and the distributed robust optimal scheduling between different stakeholders of ADN is realized.