Reactive Power Optimization With Electronic Power Transformer In Active Distribution Network

With the rapid development of new energy technology and smart grid, the third generation of active distribution network(ADN) with renewable is gradually maturing. As a large number of distributed energy resources(DER) are connected to distribution network, the traditional passive distribution network with unidirectional power flow becomes bidirectional active distribution network, voltage instability problems caused by distributed energy resources and the existing reactive power adjustment methods seriously affect the normal operation of the power grid. Therefore, research of reactive power of active distribution network is of great significance,which will help us to improve system voltage and ensure the system stability.Firstly, the composition of the active distribution network is introduced. In view of the structure of active distribution network including wind power technology, Photovoltaic power generation technology, fuel cell power generation technology, micro-turbines power generation technology and energy storage technology, which are made a brief introduction respectively, and the characteristics of all kinds of power generation are obtained. Moreover, Considering the active distribution network reactive power optimization methods, The circuit structure of the principle of power electronic transformer and reactive power control principle are introduced and got the equation of reactive power control.Secondly, the mathematical modeling and the method of the reactive power optimization of active distribution network are introduced. Considering the advantages of the reactive power flexibility control in Electronic Power Transformer(EPT), the Electronic Power Transformer is used to instead of On-load Tap Changer(OLTC) and parallel capacitor as a new reactive power control mode, and establishing a minimum active power loss as the objective function that can meet the constraints of active distribution network. Due to the particle swarm optimization is simple and easy to achieve restrain oneself, so we choose it to use to solve the reactive power optimization of active distribution network.Finally, A simulation example about reactive power optimization of distribution is set up, which containing wind power, energy storage and electronic power transformer. Using different reactive power control to analysis the optimization under different load conditions.The simulation results show that the results of reactive power optimization with EPT significantly stronger than with OLTC in the same condition, which proves the effectiveness of the power flow model of active distributed network,the reactive power optimization mathematical model and the particle swarm optimization algorithm. Meanwhile, controlling different working state of the energy storage device in the condition of different loads to verify the control advantages of active distribution network, reflecting its characteristics.