Research On Control Strategies Of General Model Of Three-level STATCOM

STATCOM is one of the representatives in the field of reactive power compensation. The STATCOM attracts extensive attention for its perfect performance such as smooth regulation of var and dynamic capability. In view of its broad application prospect, the control strategy has been one of the hot study spots. This thesis mainly includes the control strategy of three-level STATCOM.Firstly, this thesis introduces the background and significance of the research. STATCOM classification and its control strategy research are also introduced. A detailed analysis of the STATCOM main circuit structure and working principle are given. The mathematical model is built in rotating coordinates system, and the steady state characteristic under the condition of balanced system voltage is deduced;Secondly, in order to adapt to different projects, this thesis research on common model of three-level STATCOM based on per unit. Under different voltage levels, only modify the voltage values of the common model, with no changes to internal control strategy, and achieve the normal operation of three-level STATCOM;Thirdly, based on per unit, study the control strategy of three-level STATCOM, respectively for the balanced and unbalanced system voltage. Under balanced system voltage condition, the neutral-point balancing strategy of the neutral-point-clamped three-level rectifier is analyzed;Finally introduce the direct current decoupling control strategy and instantaneous phase-current tracking control strategy, then based on analysis the advantages and disadvantages of them, propose an novel sliding mode variable structure control strategy for three-level STATCOM, so device can have advances of the two mentioned strategy. The device can normally work in different condition, so as to expand the scope of the stable operation of STATCOM.