Study On Key Technology Of Intelligent Flexible Voltage Reactive Power Compensation

Static Synchronous Compensator (STATCOM), as a new type of intelligent reactive power compensation device, is an important member of the Flexible AC Transmission Systems family. It has drawn wide attention from domestic and foreign experts and scholars because of its superior performance of smooth reactive regulation and fast dynamic response. Given falling behind of some reactive power compensation devices, which can not reach the requirements of power quality, this subject conducts research on key technology of a new generation of reactive power compensation device STATCOM in low voltage distribution network and presents relative design scheme, mainly including several aspects as follows.The paper detailed describes two structures (VSI&CSI) and working principle of the main circuit of STATCOM, analyses STATCOM mathematical model when the system voltage is symmetrical and asymmetrical, which lay the foundation for proposing STATCOM control strategy. When system voltage is asymmetry, the paper puts forward an improved ip-iq current detection method, which combines with modern instantaneous reactive power theory and bases on traditional reactive compensating current detection methods. This method rationally handles the three-phase asymmetric voltage by using the three-phase fundamental positive sequence voltage as synchronization reference signal to avoid unfavorable effects brought about by the use of PLL. It is proved that the method can quickly and accurately detect the fundamental current changes which the system should compensate for the current by simulation. So the method, which can improve the speed and accuracy of the system, is superior to the traditional compensation current detection methods to.Indirect current control and direct current control method are discussed in this paper. Direct current control strategy based on fuzzy PI control is proposed by combining with rather sensitive components to compensation current control, which is involved in this paper, such as capacitance inductance and so on. According to the characteristics of reference compensation current instruction, the space voltage vector pulse width modulation (SVPWM) technique is introduced into the STATCOM, which is used in tracking control in the system of compensation current, to make the proposed control strategy function effectively, to achieve the reactive power compensation of power grid system and to improve power quality of power grid.In this paper, the proposed key technologies of STATCOM reactive power’compensation is modeled and simulated with the MATLAB7.0simulation software. The results of simulation indicate that the presented control strategy is certainly feasible. Meanwhile, the design of control system based on the DSP (TMS320LF2407) digital signal processor-based completes the main circuit, the control circuit and software design of the system.