| With the wide access of distributed generations and energy storage devices to the distribution network,the physical characteristics of the distribution network has changed from passive to active,and its control ability has increased significantly.The main access methods are generally divided into two types: as independent customer agents or in microgrid manner.Under the background of power market,distribution networks,distributed generations,energy storage devices and microgrids may belong to different owners.At the same time,distributed generations and microgrids have the characteristics of decentralized autonomy,therefore the active distribution network gradually presents multi-agent characteristics.As a result,while performing optimal dispatch of active distribution networks,privacy among different agents should be protected,which brings great challenges to the traditional optimal dispatching mode.Aiming at the optimal power flow problem of active distribution networks with multiple independent agents,this paper studies its high-precision linear modeling and efficient decentralized solution method.Firstly,aiming at the optimal power flow problem of active distribution networks with high photovoltaic penetrations,the original nonlinear optimal power flow model is constructed with the objective of minimizing network loss and penalty cost for abandonment of PV outputs,considering network security constraints,upper and lower limits of PV outputs and reactive power regulation constraints of PV.A high-precision linear approximation method for power flow equation of distribution networks is adopted.The node voltage is expressed as a linear function of node injection power,and then the distribution network and photovoltaic inverters are regarded as independent agents respectively.The original model is transformed into a decentralized quadratic programming model.The cutting plane consistency algorithm is used to implement the fully decentralized solution.The correctness and effectiveness of the method are verified by testing a real roof photovoltaic system and IEEE33 bus system.Secondly,aiming at the dynamic optimal power flow problem of active distributionnetworks with photovoltaic,distributed controllable generation units and energy storage devices,considering the coupling of 96 time periods throughout the day,a non-linear dynamic optimal power flow model of multi-agent distribution networks is constructed with the help of positive and negative spinning reserve to deal with the uncertainty of photovoltaic outputs.A quadratic programming model is constructed by approximating the AC power flow equation with high accuracy and verifying that the complementary constraints describing the operation status of energy storage devices can be automatically satisfied under certain conditions.Then distribution networks,distributed power generations and energy storage devices are taken as independent agents respectively,thus the nonlinear dynamic optimal power flow model is transformed into a decentralized quadratic programming model,and the auxiliary problem principle is used to solve it.Tests on IEEE 33-bus system and a practical 265-bus distribution network system show that the proposed method not only protects the privacy of various owners,but also realizes the coordination and optimization among independent agents by exchanging boundary variable information among them,so as to achieve global optimization.Finally,in order to solve the dynamic optimal power flow problem,in which distributed generators are connected to distribution networks in the form of micro-grid clusters,the distribution network and micro-networks are regarded as independent agents respectively.Based on Ward equivalence,a decentralized quadratic programming model for the dynamic optimal power flow problem of active distribution networks with multi-microgrids is established,and the cutting plane consistency algorithm is used to solve the problem.Tests on a system consisting of 69-node distribution network and two 13-node micro-networks show that the method has good confidentiality,does not need upper-level coordinator,and can converge to the optimal solution even when the information of cut planes is lost. |
PDF Full Text Request