Research On The Calculation Of Power Supply Capability For Distribution System

Nowadays, with the development of economy, the increasing speed of load is obviously improved, and the demand for power supply capability for distribution system is becoming higher and higher. It is very important for power supply capability to evaluate distribution system, which can directly affect the security and economy of power system. Load is one of the most significant factors for power supply capability for distribution system, so this paper mainly studies on the calculation of maximum load supply capability for distribution system and optimum capacity-load ratio for multi-voltage grade distribution system which are closely connected with load.For the calculation of maximum load supply capability for distribution system, an optimized model to solve the problem is proposed, which is based on the improved maximum load multiple method. Because of the different developing speed of each node, in the proposed model the maximum load increasing year is taken as objective function, and the safety operation constraints are constraint conditions. The optimized model is solved by the genetic algorithm. Considering that a distribution network is usually a pure radial network or a weakly meshed network, the improved loop current method is used to calculate the power flow. In the method, the susceptance branch of line is under consideration in order to improve accuracy, and solve the problem of power flow of weakly meshed network.For the calculation of optimum capacity-load ratio for multi-voltage grade distribution system, an optimized model to solve the optimum capacity-load ratio for multi-voltage grade distribution system is proposed, which is based on both technic and economy. The optimized model is solved by the discrete particle swarm optimized algorithm. On technic, the parameters of the calculation formula in"The code of planning and design of urban electrical network"are analyzed in details, especially for the load scatter coefficient for which improved method and formula are proposed. On economy, there proposed the economy evaluation system to evaluate the economy of capacity-load ratio. In this system, there are six main factors. They are the cost of building the substation, the opportunity cost, the cost of maintaining the devices, the cost of the loss of electricity, the cost of wasting the devices and the cost of the residuary devices. Annual average cost is used to weigh the economy, also considering the cost of time.In the end, by taking IEEE 33 distribution network as an example, the maximum load supply capacity is calculated; by taking an distribution system of some district in east China as an example, the optimum capacity-load ratio for each voltage grade is calculated. These two examples prove that the model and algorithm are feasible.