Research On Voltage Control Strategy Based On Coordinated Active-reactive Power Optimization In Distribution Networks

To improve the energy efficiency and build environment-friendly society,it is allowed and encouraged that the construction and development trend of distribution system need the reasonable introduction and making full use of DGs.The power flow and the advantage and disadvantage of voltage quality in the power system are the guarantee of the security,stability and economics of power system operation.With the continuous development of smart distribution grid,kinds of electricity power equipment of regulated providing a high penetration in power system,which increases the difficulty of distribution network optimal control.This paper starts with the optimal control of reactive power and voltage of distribution networks,moreover investigate the daily dispatch mathematic model based on active and reactive power coordinated optimization and its optimization algorithm,in order to obtain optimum scheme for operation of distribution networks.The specific contents are as follows:Firstly,an optimal controlling model of reactive power and voltage of distribution networks is established,in which the operating condition of power grid in a year has been divided into three scenes.The optimal model takes into account the operation economic efficiency and voltage control effect,uses the minimum of the total costs,which is constituted by yearly cost of distributed network energy loss and the investment cost of reactive power compensation device,as objective function.And then,the above cost models was expanded and improved with the voltage control penalty function,in order to obtain better voltage control effect.This paper chooses a numerical solving algorithm named bat algorithm as the method of solving the model.In order to tackle the shortcoming of the bat algorithm that has low convergence speed in the later period of the optimization and is liable to fall into local optimum,introduces niche technique in the unit bat and makes improvement.This paper solves the model by using improved niche bat algorithm;finally determine the allocation and operation scheme of reactive power compensation device.Secondly,the influence of distributed generation on voltage profile of the power system is discussed from three aspects of DGs site,capacity and power factor.This paper derived the active/reactive sensitivity matrix to node voltage based on Newton-Raphson power flow equation,and establishes the overvoltage control strategy based on the power coupled sensitivity matrix.The control strategy takes the minimum of voltage offset as a goal of optimization,considers the compound regulating effect of DGs and reactive compensation devices,and selects control nodes according to the sensitivity matrix,which makes the voltage control operation more purposeful.Finally,this paper establishes an inter-day multi-period optimization strategy for distributed network with DGs based on active and reactive power coordination function,which consider the randomness and fluctuation of DGs,the controllability of energy storage system(ESSs)and the regulating effect of capacitor banks.The established model is a multi-object optimization problem with target functions of the lowest network loss,the smallest voltage deviation and the highest using efficiency of ESSs.The multi-objective model is processed by the method of data envelopment analysis(DEA)and principal component analysis(PCA),and then is transformed into a single objective optimization model with weight coefficient.The improved niche bat algorithm is adopted to solve the model,and the effectiveness of the proposed strategy in this thesis is proved.