Research On Voltage Stability Control Of Active Distribution Network Based On Power Spring

With the continuous development of new power generation technology,the distributed generation has become a research focus in power system due to its flexibility and near-load characteristics.However,because of the natural factors such as wind speed and solar light change,the output power of distributed generation unit has strong random fluctuation.When a large amount of distributed generation is connected to active distribution network,it will inevitably have a strong negative effect on the voltage of distribution network,or even affect the normal operation of critical loads seriously.In recent years,with the introduction of the electric spring technology,the electric spring provides a new solution for the voltage stability control of active distribution network as a new kind of voltage control device,and also provides new convenience for large-scale renewable energy power generation access to power grid in the future.Therefore,in order to achieve active distribution network voltage stability and reliability,and to improve the reliability of the critical load in distribution network,this thesis focuses on the electric spring and its corresponding improved control methods,supplemented by optimization of distributed generation configuration.The main contents of this thesis paper are shown as follows:Firstly,the concept and basic model of active distribution network are introduced,including the power model of wind and PV distributed generation units,the general model of distribution network and the calculation method of power flow in active distributed network.In order to improve the stability of the system voltage from the planning stage of active distribution network and to reduce the comprehensive cost,the advance genetic algorithm and evaluation indexes of active distribution network are used to establish the optimal configuration method of distributed generation in active distribution network.Secondly,the working principle and basic model of electric spring including intelligent load model and circuit mode of electric spring are studied.By using advanced particle swarm optimization and fuzzy control control method,the single electric spring control method based on traditional PI control is improved.The advanced particle swarm optimization algorithm is used to calculate the initial optimal parameters of PI control,and the fuzzy control method is used to realize the real-time adjustment of control parameters.As a result,the adaptive control method of electric spring is proposed,and the voltage regulation performance and working stability of a single electric spring can be improved.Thirdly,according to the requirements of multi electric springs connected to active power distribution network,a hierarchical control structure and method of multi electric springs are established based on the multi-agent technology.Among them,the load layer adopts the electric spring control method considering the noncritical load voltage constraint.The feeder layer adopts the control method which is combined with multi electric springs control based on voltage droop characteristic and emergency control.Then the multi electric spring control method for active distributed network is proposed,which can realize the coordinated operation among different electric spring and enhance the actual users' experience.Thus the stability control ability of distribution network voltage is improved.Finally,the Matlab/Simulink simulation test platform is used to perform simulation test for the optimal configuration method of distributed generation,the adaptive control method of electric spring and the control method for multi electric springs in active distribution network,respectively.The test results verify the feasibility and effectiveness of each method above.The in-depth study of electric spring technology provides an effective solution for the stability of the voltage in active distribution network.