Research On The Application Of STATCOM In Power Grid Voltage Disturbance Elimination

This paper proposed a method to eliminate the voltage disturbance caused by permanent magnetic synchronous generator on Point of Common Coupling(PCC) via STATCOM. Because of the change of wind speed, the weak magnetic of turbine and the hysteresis of the converter, wind turbines may cause voltage fluctuation, voltage drop and other instabilities on PCC. An eliminating technology is urgently to be developed.First of all, the mathematical model of STATCOM will be established, to analyze its basic compensating principle. According to different conditions of loads and the working status of STATCOM, four kinds of modes will be obtained, which will be analyzing by vector diagrams. The relationship between the device parameter of STATCOM and the electrical quantity at quiescent operating point will be obtained by Kirchhoff laws. A simulation will be accomplished to validate the analysis above. All the work will provide an effective method for designing STATCOM device parameters.Feed forward decoupling method will be used in this paper to design the controlling system with a current inner-loop and a voltage outer-loop. Since a shorter response time of compensator is highly preferred in wind farm, an adaptive PI controller will be designed in this paper, which is able to resolve the contradiction between the response time and the overshoot. At the same time, a protective control strategy that keeps highest priority of DC voltage stability will be proposed. The protective strategy can effectively eliminate the fluctuation of reactive power under a drastic load change. A simulation will be accomplished to validate the designed strategy.The small-signal model of STATCOM will be established to solve the approximation of its characteristic equation, which is able to describe the response time of the hardware. Based on the small-signal model, mathematical models of controller in frequency domain will be obtained. By analyzing the relation between the device parameters and the controller performance, a numerable designing principle on hardware will be proposed. Moreover, a data-processing method based on sliding-window Discrete Fourier Transform will be introduced to minimize the data-processing time.Finally, a 20 k VA STATCOM platform will be designed and established in the lab. The whole platform includes the control circuit and the main circuit. The whole scheme will be accomplished on DSP2812. The induction loads will be utilized to generate the voltage disturbance. The experimental results can validates the effectiveness of the whole scheme. The response time of the designed STATCOM is about 10 ms. The THDi and THDu caused by STATCOM are less than 8% and 4% respectively, which meets the codes of China.