Static Voltage Stability Study On Planning Method Research Of Transmission Network With Wind Farms

In order to promote the sustainable development of economy and society, wind power has been developed rapidly in China. As the rating of wind power in power network rises, and the voltage levels of the network that wind farms connected to is higher, the influence which large grid-connected wind farms bring to the power system can not be ignored. Therefore, planning the suitable transmission network to improve the influence which large wind farms bring to the power system is the important issue standing on the way of network development. The major research and contributions are as follows:Newton-Raphson power flow calculation model is used to test the standard IEEE 14 bus system with a wind farm which consists of double-fed asynchronous generator at constant power factor control mode. Analysis shows that wind farm bus voltage and reactive power increase along with the active power of the wind farm increases; meanwhile, wind farm connected to the network will enable the system bus voltage increase and the system load power change, and the network close to wind farms has a greater impact.Based on the power flow calculation, system voltage stability index is used to quantified the system voltage stability. Tests on the revised standard IEEE 14 bus system show that as the load increases, the system static voltage stability is reduced; when the load maintains at a certain level and the output of wind farm is within a certain range, with the increase in output power, the system static voltage stability is improved; when the wind power output has further growth, the system static voltage stability reduces rapidly or even collapses.Considering the voltage stability problem of the system that wind farm combining to is very prominent, the planning problem of 220kV transmission network that large-scale wind power combining to is studied from the power grid construction economics and system security. A multi-objective optimal model of the transmission network is established to minimize the cost of power grid construction and the power loss of network and maximize the static voltage stability margin. The multi-objective planning is transformed into single objective planning by employing the fuzzy optimization theory, and the model is solved by improved genetic algorithm. By using 220kV power transmission system of a region in China as a calculation example, we got a satisfactory optimal network, it shows that the model is reasonable.