Research Of Low-Voltage STATCOM

At present, the power system is lack of var compensation, furthermore most compensation methods for the compensation devices are not good enough to meet the requirement of compensation for power system. STATCOM is an appropriate solution of these problems. Heretofore, the studies and application about STATCOM are emphasized on large capability and high voltage devices. For compensating reactive power and harmful currents in low voltage power system, the paper proposed two control schemes for STATCOM, which are indirect-current control and direct-current control. The main works and conclusions are as follows:For compensating reactive power of balanced power system, STATCOM using indirect-current control is developed. Through comparing accustomed structures of main circuit, a converter with three legs is selected as main circuit. The math model is established. In the paper, two inverse-system PI controllers are used to control output of reactive power and voltage on DC side respectively. The result of simulation confirmed that the STATCOM have good compensation performance, and its dynamic performance is improved.The hardware of STATCOM is designed. The work includes the selection of main circuits components and control chip, the designs of measuring circuit, control circuit and electrical source circuit. The hardware constitutes STATCOM device.For compensating harmonic, zero-sequence and negative-sequence currents besides reactive current, STATCOM using direct-current control is developed. Through comparing two accustomed structures of main circuit, a converter with four legs is selected as main circuit. The detection based on generalized instantaneous reactive power theory is selected after introducing several kinds of reference current detection. The math model is established. A new hysteresis current control based on ??? coordinate system is proposed to control the converter. The results of simulation show that the STATCOM not only can compensate reactive power, but also can eliminate the harmonic, zero-sequence and negative-sequence current effectively.