Research Of Reactive Power Compensation And Angle Stability Of Wind Power Integration

With the continuous depletion of the Earth’s environment and the continues consuming of gasoline, natural gas and other energy, clean and renewable energy appeared on the stage of human history. Wind power is the typical representative of that type of energy. Today, wind power is developing to industrialization and large-scale, and its generating capacity is getting heavier in the proportion of power grid. However, due to the short time of the development of wind power, there are still many problems waiting to be solved. Such as after a large number of wind farms accessing to the high-voltage grid, wind power will influence the security and stability of the grid. This severely limits the size of the wind power generation, and limits the using conditions of wind power. Around the reactive power compensation and angle stability issues while wind power accessing to grid, following are the research results:1. To meet the fast and continuous transport of wind farm’s reactive power failure after the grid fault, using the reactive power compensation device SVC and STATCOM instead of the traditional switched capacitor group. Establish the mathematical models of wind turbine, SVC and STATCOM. Propose the control strategy of double-fed wind turbine, SVC and STATCOM. Using the software PSCAD to simulate the wind power grid model and control system. Asynchronous generators and doubly-fed generator were used in the simulation, and both generators install SVC or STATCOM. The simulation results show that, STATCOM act better than SVC.2. Research rotor over current issue and reactive power compensation issue causing by the fall of the wind farm voltage, and propose the control strategy based on crowbar circuit. During the grid fault, the doubly-fed machine will be a reactive load instead of reactive power, and increase the burden of grid. Applied STATCOM to wind farms, and appropriate control strategies based on the mathematical model to keep the balance of power grid. Then analyses the rotor current based on crowbar circuit, and gets the mathematical expression of the resistance and the rotor current. Finally, simulate with the control strategy of STATCOM and crowbar. Simulation results show that, after the fall of the grid voltage, the control strategy of STATCOM is able to continue deliver reactive power to the grid, and also to maintain the stability of the grid voltage. The reasonable operate of crowbar circuit can make the rotor current decay rapidly, so that the fan can continued hang on the grid.3. Established the model of wind turbine based on doubly-fed induction generator, and make the model linearization. Using eigenvalue analysis method to analysis the small signal stability of the wind turbine system, the result shows:the double-feeding system have oscillation mode and decay mode, and the low-frequency oscillation modes get acceptable damping ratio. So the wind turbine in this paper is stable with small signal disturbing.