| The problems, such as controlling flow, improving stability, brought by area interconnectedin field of modern power system, can’t handle by traditional adjustment. Flexible ACtransmission system (FACTS) developed rapidly as power electronics grew. Many solutions forimproving power system stability have been provided by powerful STATCOM, an advancedFACTS equipment. Multi-level technology realizes its application in middle and high voltage,huge capacity occasion, while STATCOM generating precise reactive power without delay. SoSTATCOM is selected to be researched by this paper.The equivalent circuit of transmission line in power system is studied firstly. A discussionabout factors cause system voltage unstable and power loss has been done to define meaningand goal of reactive power compensation. The control method and detect method for outputcurrent, and problems about control coupling of AC side are researched and solved based onfull and accurate analysis about structure and equivalent circuit of STATCOM. In chapter threeof this paper, two topology structures of multi-level converter have been compared, includingperformance, advantage and disadvantage. As a result, cascaded structure is selected as maincircuit of STATCOM, and phase shifted PWM as the control method, considering thecharacteristic of its application. The main controller, consist with digital signal processor (DSP)and field programmable gate array (FPGA), has been designed according to modular controlfeature of phase shifted PWM for STATCOM. This controller could compensate accuratereactive power rapidly to stabilize access point voltage by taking system voltage as target.In the last chapter of this paper, a simulation about41level cascaded STATCOM isfinished under MATLAB/Simulink circumstance. The ability of STATCOM to stabilize systemvoltage and control system flow have been proved by the result and its analysis, so does thetremendous value for multi-level technology used on huge capacity STATCOM. |
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