Evaluation Of Voltage Stability For Local Power Grid

Load growth and the development of long distant large capacity transmission bring both power angle stability problem and voltage instability. Three aspects that cause voltage instability are listed as follow. The first one is the load growth that could drop the voltage. The second one is the faults which can lead to the continued deterioration of operation state. The margin of voltage stability cannot ensure the security of power system. The last one is variation of wind power which will also cause voltage instability. This paper evaluated the voltage stability of power system while considering the three aspects mentioned above. Firstly, this paper defined the indexes of voltage stability. Sensitivity of reactive power loss and the load margin were computed by the CPF method. And the weak nodes were obtained by sorting the indexes of reactive power loss. Meantime, comparison was conducted between the indexes of voltage stability with and without SVC in weak nodes and non-weak nodes, respectively. Then, this paper brought the probability analysis method into the evaluation of voltage stability combined with the index of voltage instability while considering the load random variation and the probability of lines’fault. And this paper also achieved the probabilistic evaluation of local grid’s voltage stability. Finally, indexes of voltage stability were defined in response to the variation of wind power. The change curves of expected value of voltage, variance of voltage and the margin indexes of voltage stability based on the generalized Telegen theorem with the variation of wind power were obtained based on the nonlinear prime-dual interior point method. At last, this paper simulated the three circumstances mentioned above with the IEEE14study case and the evaluation of voltage was done. And a more comprehensive evaluation results were worked out.