Research On LADRC Circulation Suppression And Improved Voltage Balancing Control Strategy In MMC-STATCOM System

As an important devices of FACTS,STATCOM(Static synchronous compensator)provides a very serviceable methods for the grid command,it has a more wider field for development and prospective of applying,and owing its excellent reactive power control ability and good performance,STATCOM become the superior in power quality control.In this paper,the MMC-STATCOM system in the circulation suppression and other issues are studied,the specific research work is as follows:Based on the analysis of the topological structure and operation characteristics of the MMC,the control method of loop current suppression based on linear auto-disturbance-rejection(LADRC)is proposed,and its working mechanism and implementation method are studied.The results show that the voltage imbalance of the sub-module is caused by the analysis of the voltage imbalance of the sub-module,and the voltage balance problem can not be solved when the light-load control method is adopted at the light load.The improved method is based on the original pulse.Loop algorithm to solve the light load can not be achieved when the pressure problem.After comparing the modulation strategy,CPS-SPWM modulation technology with wider working range and higher modularity is selected.Aiming at the characteristics of MMC-STATCOM system,the hierarchical control strategy is designed,and the upper layer is double closed-loop Feedforward decoupling control strategy and LADRC loop suppression control strategy,the lower layer to improve the capacitor voltage balance control strategy.A simulation model of MMC-STATCOM system with 21 levels is built in the PSCAD/EMTDC simulation software.The simulation results show that the control strategy can be used in light load condition The voltage fluctuation of the system is simulated,and the correctness of the proposed loop suppressor and the ability of suppressing the system voltage fluctuation by MMC-STATCOM are also verified.Wave content of the CPS-SPWM is analyzed and compared to verify the CPS-SPWM phase-shifting and filtering effect.