Current Decoupling Control Strategy of Medium Voltage Cascaded Multilevel STATCOM

As one of effective regulation methods, static synchronous compensator (STATCOM) has been widespread used to regulate dynamic reactive power and solve dynamic voltage stability problems into powergrid. Through the analysis of mathematical model, cascaded STATCOM, which is constructed by several cascaded H-bridges, is a nonlinear, multivariable, strongly coupled system. It will make difficulties in the design and practical application of controller. In this paper, mathematical models of cascaded STATCOM in a -bc and d-q coordinates are deduced. Based on the theory of internal model control and PI control strategy, the internal decoupling control algorithm is introduced to realize independent control of active current and reactive current. At the same time, decoupling control algorithms are designed and decoupling control models are given and simulated. From the combined circuit topology and control with multi-FPGA, the simulation and experimental platform of cascaded SVG, which use the control algorithms of double-loop control with the current inner loop and capacitor voltage outer loop. Both in a-b-c coordinates and d-q-0 coordinates, experiment and simulation results show that three-phase current of STATCOM has good tracking performance and control precision, which show the regulator design method and parameters setting are feasible and effective. Copyright © 2014 IFSA Publishing, S. L.