Research On Reactive Power And Voltage Optimization Control In Small Hydropower Area

Water resources are widely distributed in China with a long exploration history,as an integral part of water resources,small hydropower plays an important role in China's energy development.In recent years,the development of small hydropower has provided the guarantee for the local power demand and industrial operation.However,with the increase of generating capacity of small hydropower,it also brings a series of problems such as regional voltage limitation and the increase of network loss.In this thesis,through the analysis of the reactive power brought by the grid-connection of small hydropower,the reactive power compensation and reactive power optimization are studied.The main research contents include the following aspects:(1)The causes of the reactive power voltage problem in the area of small hydropower is analysed.In this thesis,the excess reactive voltage and the lack of effective regulating means of small hydropower area in the period of abundant water are discussed from the influence of hydropower grid for large power grid,distribution of reactive power compensation device in distribution network and the geographical restrictions of small hydropower.Then,from the aspects of the management status of small hydropower and the coordinated operation of small hydropowers,the reasons why the reactive power in the area of small hydropower is more serious and difficult to adjust are explained.(2)For the issues of excessive loss of network and the serious exceeding voltage caused by the lack of reactive power compensation equipment in small hydropower area,the measures of reactive compensation based on comprehensive sensitivity analysis are proposed.Firstly,the ideal reactive power compensation capacities for each node are determined through the economic pressure theory.Then the reactive power voltage control capacity and reactive power loss sensitivity are calculated for each node,besides,the comprehensive sensitivity index is established and the appropriate installation nodes of reactive power compensation device are determined.Finally,an example in southern Shaanxi area is given to illustrate the effectiveness of the proposed method.(3)In order to solve the problems of over-limit voltage and abandoned water in small hydropower area,a reactive power voltage control scheme based on two-stage programming method is proposed,in order to maintain regional stability operation,meanwhile reduce the consumption of water resources and improve system energy storage.The first stage is the optimal regulation of hydropower,taking the maximum consumption of generation as objective function,the output of each hydropower station in the system is determined;the second stage is the reactive power optimization,firstly,the ideal switching condition of reactors is determined using static optimization method,and then the switching group number of capacitors is adjusted by taking the number of adjustment as limit,finally,the reactive power optimization is achieved by the leading phase operation of the small hydropower system.