Research On Voltage Control Of Distributed Photovoltaic Distribution Network

After the access of a large number of distributed photovoltaic power sources,problems such as voltage crossing have frequently appeared in the distribution network.Therefore,it is urgent to carry out research on the influence of photovoltaic access on the voltage quality of the distribution network,the online voltage stability index of branches,and the reactive power optimization control strategy including photovoltaic access in the distribution network.Therefore,this thesis studies the voltage control strategy of distributed photovoltaic distribution network,aiming to improve the security of distribution network operation,reduce the network loss,improve the operation economy,reduce the voltage crossing problem caused by photovoltaic power access,and improve the adaptability of distribution network to voltage fluctuations.This thesis starts from two parts,namely,the voltage overlimit caused by the fluctuation of photovoltaic and the economic optimization problem of the distribution network regulation of photovoltaic access.The research is carried out under the framework of multi-time scale voltage control and multi-device coordinated voltage control.The specific research contents are as follows:Firstly,the voltage control model of the distribution network is studied,and the photovoltaic model,the on-load voltage regulating transformer model and the shunt capacitor model are established from the perspective of adjusting the speed and slow speed equipment.Under the background of voltage control problem after high-permeability photovoltaic grid-connection,the voltage safety index,voltage danger coefficient,is proposed to evaluate the time section of distribution network under high-permeability photovoltaic parallel network.Then,the mathematical model of voltage danger system is built on this basis.A multi-time scale voltage control model is established for the voltage overlimit problem caused by the fluctuation of photovoltaic.In the long time scale,a day-ahead optimization scheduling strategy was proposed based on the voltage risk factor,which aims to optimize the economic and safety satisfaction.In the short time scale,the fixed slope of the traditional sag control was dynamically corrected by the voltage risk factor,so as to release the reactive power margin of the photovoltaic inverter.At the same time,the feedback correction for long time scale is added into the optimization control of short time scale.In photovoltaic(pv)access to distribution network to adjust the economic optimization,more equipment coordinated voltage control model is established,in order to meet the power distribution network equipment adjustment cost minimum as the goal,with the low voltage distribution network rapid movement equipment as the object,using active forecast information,etc.,by adjusting the cost factor to determine the action will be the next moment fast regulating equipment,rapid equipment adjustment cost model is set up;After determining the equipment used,a coordinated control strategy of MPC active power and reactive power is proposed,which takes into account the adjustment cost and takes the system risk risk coefficient and adjustment cost coefficient as the objective,and then combines with the active power and reactive power regulation model of low-voltage distribution network.At the same time when each parallel point starts to control,the safety recovery control link solves the problem of insufficient rapid equipment margin.