Research On Feedforward Compensation Adaptive Quasi-PR Control Of MMC-APF Circulation Suppression Strategy

The modular multilevel converter(MMC)has a significant competitive superiority over other inverters in high voltage and high power fields,such as HVDC transmission,power quality control and so on.Therefore,MMC is applied in active power filter(APF)to solve the shortcomings of traditional APF in high voltage and high power applications.This paper focuses on the problem of interphase circulation in MMC,and proposes a feedforward compensation adaptive quasi PR control method,and carries out simulation and experimental analysis.The mathematical modeling of the topology of MMC-APF is presented in this paper.The harmonic detection algorithm of MMC-APF and the modulation strategy of MMC are further briefly introduced.In order to solve the problem of capacitive voltage imbalance of MMC,an improved method is proposed in order to solve the problem of high switching frequency in traditional methods.In this paper,an adaptive quasi-PR control method is proposed for the double frequency current in the bridge arm current of the MMC.The adjustment rules of related parameters are given.At the same time,feedforward compensation is performed on the disturbance of the capacitance voltage of the sub-module to suppress other even-numbered circulations caused by the disturbance of the sub-module capacitance voltage.The control method proposed in this paper does not need coordinate transformation and phase decoupling.Each phase only needs one quasi-PR controller to suppress even-numbered circulation in MMC at the same time.The structure is simple and can adapt to the change of load.Finally,the simulation model and experimental prototype of MMC-APF are designed to verify the feasibility of the proposed control method.