| Power system gradually becomes a random-determine coupled system with large-scale wind power centralized into the grid because of different dynamic characteristics between wind turbine and synchronous machine, coupled with random fluctuations of wind power. This gives the power system stability, especially small signal stability (SSS) and its analysis a lot of new problems. Traditional deterministic methods are difficult to analyze the SSS of power system characteristics including wind farms accurately and completely.In this paper, Stochastic Differential Equations (SDE) and Probability analysis methods were employed to analyze the impact of random fluctuations of wind power to the SSS of power system with DFIG wind farms.Firstly, dynamic behaviors of system in the recovery process after a small perturbation occurred at the specific balance point were studied by SDE method. The stochastic dynamic model of power systems with DFIG was established to analyze the SSS of single and multi-machine system. And the impact of random excitation to the dynamic response of the state variables was described using fluctuation variance.Then, the SSS of random equilibrium of the large-scale actual system with DFIG was studied by Probability analysis method. Against the issue that traditional probabilistic methods are difficult to analyze the actual large-scale power system SSS with wind power, a Monte Carlo probabilistic analysis method based on stability analysis program of BPA was proposed to analyze SSS of power systems with wind power making Probabilistic analysis be applied to the actual large-scale power system SSS. The IEEE 3 machine 9-bus system and the actual large-scale power system of one province were studied using the proposed method.A set of SSS of stochastic analysis methods of power system with wind power was proposed in the entire study. The research achievements have reference value for studying on stability of a random-determine coupled power system. |
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