Study On Control Technology Of STATCOM Based On MMC

Static synchronous compensator (STATCOM) provides an effective method forsolving the power grid management, and now it is developing to the main force forelectricity quality control field. In contrast of the power quality management for highvoltage and high power applications, this paper analyzes the advantages anddisadvantages of converter topologies of several compensation devices based onmulti-level control strategy.This paper presents a novel topology based on themodular multilevel converter (MMC), then deep analyses and researches the workmechanism and key technology based on high voltage and large capacitySTATCOM.The content of this research lays a foundation for the extensiveapplication of static synchronous compensator (STATCOM) for future high voltage,large capacity. This paper carries out the following work:Firstly, the topological structure and working principle of MMC are introducedin this paper, and the structure and operation mode of the sub module has beenanalyzed. Through comparation of several common modulation applied to MMC,this paper chooses carrier phase-shifting technology (CPS-SPWM) as the modulationstrategy of MMC. And this paper has analyzed the causes of unbalanced voltage ofthe sub modules, in order to solve the problem the methods of voltage grading andvoltage sorting has been proposed, and through analyzing both the advantages anddisadvantages of the two capacitor voltage balance control strategy determines theirmost appropriate for individual applications. According to the shortcoming ofhigh switching frequency of traditional voltage sorting method, this paper proposesan improved method. And this paper also proposes a novel topology based on MMCto solve the problem of system circulation.Secondly, the paper introduces the principle of STATCOM, and proposes thereactive current detection method based on instantaneous reactive power theory.Through the establishment of mathematical model of the system, put forward the control strategy based on feed-forward decoupling of voltage and current doubleclosed-loop system. Combined with the controller of the novel topology, the controlstrategy of the general design has been proposed.Thirdly, Simulating test is proceeded by relevant simulation software MATLAB.The compensatory effect of system and dynamic performance, the balance controlstrategy of module capacitor voltage and the circulation inhibit controller basedon a novel topology are verified.Finally, the whole design of the system is performed, which includes thecalculation of components of the main circuit parameters, hardware design andsoftware program design. DSP and FPGA are chose as the core of the control system.An experimental platform is built, the simulation results of the prototype and thesystem are basically same, and furtherly verify the correctness of control technologyproposed in this paper.