Impact Study For The Voltage Stability Analysis Of Wind Power Integrated System

Energy crisis and environmental deterioration have been increasingly threatening the security and development of human society. For this reason, countries around the world are actively seeking to develop new energy sources. As one of the fastest growing new energy, wind power has lots of advantages such as large reserves, renewable, no pollution, wide distribution etc. Wind energy for power generation are increasingly popular around the world. In recent years, domestic and international wind power industry has been developing rapidly. Both the number of wind farms and the installed capacity increased rapidly. Because wind power is intermittent, random and non-regulatory, with the increasing of wind power output the impact of wind power on the grid especially voltage stability is increasing, so the research on the voltage stability of wind power systems is necessary.With the development of wind turbines, double-fed induction wind turbine with its high cost performance gradually become the mainstream fan, so this paper mainly focus on the wind farms composed of double-fed wind turbine for the study. This article describes the steady-state model of doubly-fed units in detail. Thanks to the control of the inverter, active and reactive power of double-fed units can be decoupling controlled. Because the output of the unit will be limited by the maximum current limit of the converter, the paper also deduced an expression of the reactive power which is the network systems unit can output with certain active power being output at the same time. In flow calculation, wind farm composed of double-fed induction wind turbines can access system as different equivalent models based on the turbines’different control methods. With the change of the unit output power, the equivalent model of wind farms in the flow calculation also may change.This paper mainly adopted the method of voltage stability index L to analysis the static voltage stability of wind power accessed grid. If the L index of a node is larger, the weakness degree of the node will be higher, and voltage instability is more likely to occur in this node. Based on L index, this paper derived an L-P sensitivity index to measure the effect degree of the change in wind farm active power injected into the system on each node’s voltage stability index of sensitivity of L-P index. By sorting the index the wind farm node’s strong correlated nodes can be obtained. Through the value of the index we can also estimate the size of wind power injected under the influence of increasing or decreasing, the possible voltage stability index value of each node in the system will produce. These two indicators have simple structure, and their calculation can be enough quickly to be used for line voltage stability analysis.Then, according to these two indexes, the IEEE-39 system is analyzed. The voltage stabilities are compared when the wing farm integrated to the system. Furthermore, changing conditions such as injected wind power, the parameter of transmission and access way of the wind farm, the voltage stability are analyzed, coming a conclusion. It is significant in the actual wind farm integrated to the grid system.Finally, this paper analyzed voltage stability of the region before and after the wind farm were accessed to the Yantai, Weihai actual grid. Within each wind farm’s rated output range, by changing the wind power injection and calculating the influence on the voltage and voltage stability index of the buses to determine the advantages or disadvantages of wind power.by calculating L-P sensitivity index of the interconnection buses when the wind farm output the rated power to judge the feasibility of the wind farm’s expansion. And this paper also explored the changed system operation mode and different wind farms’access way bring the effect on grid’s voltage stability. Finally, this paper presented several measures to reduce the voltage fluctuations and enhance the voltage stability caused by wind farm. Particularly, In particular, it focused on the in situ reactive power compensation of wind farms.