An Arm Current Control Strategy for MMC-HVDC Based on Novel Generalized Integrators

The mathematic model of MMC based on arm currents was established and computational formula of the arm current reference was presented. In order to achieve ac-side current control and circulating current suppression simultaneously, this paper presented an arm current control strategy which is based on the proportional integrator and two sinusoidal signal regulators in parallel in the three-phase stationary frame. This paper presented a novel generalized integrator (NGI), and then thorough analysis and comparison between NGI and the quasi second order generalized integrator (QSOGI) were carried on from the point of time domain and frequency domain. The comparison shows that the control system has good control accuracy and transient performances and big phase margin when NGI is used as the current controller. Simulation results demonstrate that the proposed control strategy can work well under balanced grid voltage as well as under severe grid faults. © 2017 Chin. Soc. for Elec. Eng.