Research On Reactive Power Optimization Of Distribution Network Including Distributed Photovoltaic Power Considering Power Quality

Because of its green,clean and sustainable development advantages,the permeability of distributed photovoltaic(PV)power in the distribution network gradually increases.However,the active power output of the PV power output is fluctuating by the influence of weather conditions such as light intensity and temperature,and the photovoltaic power source will inject the harmonic current into the distribution network,which adversely affects the power quality of the distribution network.Therefore,the complexity and flexibility of reactive power optimization in the distribution network has increased,resulting in that the traditional reactive power optimization method can not fully adapt to the grid-connected photovoltaic power system.In the process of operating in the grid,the PV power plant injects a large number of harmonic current into the distribution network,which reduces the power quality of the distribution network.In this paper,the static var generator(SVG)was connected to the outlet side of the PV power plant,and the SVG generated by the grid voltage feedforward control strategy was used to effectively suppress the harmonic current generated by the PV power plant.If the active power output of the PV plant and the reactive power output of the SVG changed,the harmonic current with SVG and PV would also change.Based on the back-propagation(BP)neural network,the harmonic current model with SVG and PV was established and the model could well calculate the harmonic current with SVG and PV.Aiming at the randomness of the PV power plant output and the uncertainty of the load,the stochastic harmonic power flow model with SVG and PV was established.The Monte Carlo simulation method was used to sample the distribution network data,and the stochastic harmonic power flow was calculated.Thus,the stochastic fundamental and stochastic power flow results were obtained,which could provide accurate information for the subsequent reactive power optimization.The harmonic current of SVG and PV,together with its uncertainties would affect the reactive power optimization of the distribution network.Based on the established harmonic current model with SVG and PV,and the established stochastic harmonic power flow model,the harmonics index-Total Harmonic Distortions of u(THDu,u represents voltage)was added to the traditional reactive power optimization mathematical model.Furthermore,chance constraints were put on the bus fundamental voltages and THDu.Thus,the reactive power optimization model of distribution network with PV and SVG considering the harmonic factors was established.In this paper,the Particle Swarm Optimization(PSO)was used to solve the reactive power optimization model.The IEEE 33 node distribution system case was used to verify the rationality and feasibility of the proposed reactive power optimization model and that model could reduce the active loss and the harmonic pollution,in order to improve the economy and security operation of the distribution network.