Reactive Power Optimization Of Urban High Voltage Power System Borrowing Ideas From The Simplex Method

The purpose of reactive power optimization is to reduce the active power loss and to improve the voltage quality in power networks by adjusting reactive power devices. Research of reactive power optimization has great significance in theory and practical application.The problem of reactive power optimization is a multi-variable and multi-constrained mixed integer programming problem.The variables for describing the state of switching capacitor banks and the stalls of transformer taps are discrete variables, therefore, it is very complex to solve optimization problems.Considering the influence degree in the actual urban power, this paper deals with the capacitor bank and transformer tap separately, with optimizing the switching state of the capacitor bank to reduce power loss and adjusting transformer taps to meet the network's voltage quality.Total active power loss is reduced by switching on/out capacitor banks.In the process of implementation, the capacitor bank state is determined from the quasi-Newton method which calculates reactive power demand of compensation nodes, and is regarded as the initial value for further computation. In view of the obvious superiority in running speed and convergence reliability of the simplex method used for linear programming problems, the basic idea of selecting'call in' and'call out'variables in the simplex method is introduced to the nonlinear reactive power optimization in urban high voltage power systems. During the "basic point" conversion,'Call in' and 'Call out' variables are selected referring to the reactive power sensitivities to optimize switching on/out capacitor banks state by calculating the size of the objective function.The objective function of synthetic reactive power optimization is the compositive costs with considering the cost of adjusting control devices.The optimization procedure is composed of two stages of static and compositive optimization. In the static stage, capacitor bank states is determined by using the idea of the base transformation in the simplex method.,and the operation ranges of transformer taps for selection are determined from requirement of nodal voltage regulation. In the compositive optimization stage, device states in 24 hours are coordinated. Computed result gives out the adjusting scheme.in 24 hours, including the total compositive economic index, capacitor set states and transformer tap values at every hours. Testing computation shows that the compositive economic index will be improved and the number of device adjustment will be largely reduced by using the compositive reactive optimization.