An Analytical Approach to Harmonic Analysis and Controller Design of a STATCOM

• Main Authors: Ben-Sheng Chen, 陳本盛
• Other Authors: Yuan-Yih Hsu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/97289352997168560356

博士 === 國立臺灣大學 === 電機工程學研究所 === 94 === Steady-state harmonics and transient performance of the conventional static synchronous compensator (STATCOM) controllers are first investigated. Based on the sensitivity analysis of the STATCOM output power, it is found that the voltage magnitude is more effective than the phase angle in controlling the reactive power output. An analytical approach to harmonic analysis of a STATCOM based on Bessel functions of the first kind is described. Harmonic analysis of the STATCOM using the proposed analytical approach reveals that the total harmonic distortion of the STATCOM output voltage is minimal as the modulation index is fixed at unity at steady state. Based on these results, two new STACOM controllers are proposed in order to achieve both minimal steady-state harmonics and fast transient response. The first STATCOM controller proposed in this thesis is one with a fixed modulation index reference. The modulation index is held constant at unity at steady state by the proposed STATCOM controller in order to minimize voltage and current harmonics. By comparing the voltage and current response curves and harmonic spectra obtained from the analytical approach, the computer simulations, and the experiments, it is concluded that minimal harmonics can be maintained at steady state and fast dynamic responses can be achieved to regulate ac system bus voltage by the proposed STATCOM controller through the fast adjustment of the modulation index during the transient period. In the second proposed STATCOM controller, a variable DC capacitor voltage reference is employed to minimize voltage and current harmonics at steady state and to adjust DC capacitor voltage level and STATCOM output reactive power rapidly during the transient period. A systematic design procedure based on pole-zero cancellation, root locus method, and pole assignment method is developed in order to determine proper parameters for the current regulator, the DC voltage controller, and the AC voltage controller of the STATCOM. With the proposed STATCOM controller, harmonic distortions in the inverter output current and voltage can be reduced when the modulation index is held constant at unity in steady state. In addition, fast adjustment in the STATCOM output reactive power can be achieved to regulate AC bus voltage through the adjustment of DC voltage reference during the transient period. Simulation and experimental results for steady-state operating condition and transient operating conditions for the system subjected to reactive current step changing testing, three phase line to ground fault testing, and load changing testing are presented in order to demonstrate the effectiveness of the proposed STATCOM controller.