Grid-forming controller design of low-voltage ride-through for parallel energy storage converters

Abstract

The grid-connected parallel energy-storage converters using grid-forming control should have the gridforming low-voltage ride-through (LVRT) capability to avoid reducing the grid strength during grid faults. This paper proposes a grid-forming low-voltage ride-through control method for energy storage converters. This method has two characteristics: (1) Under normal grid conditions, virtual impedance control is employed into the voltage controller loop of the virtual synchronous machine control to reshape the output impedance characteristics of the parallel energy storage converter; (2) When a three-phase short-circuit fault occurs in the grid, a grid-forming low-voltage ride-through control method considering the amplitude and phase compensation of the output voltage of the converter with virtual impedance is proposed, and the parameters of the voltage controller are optimized to achieve the rapid tracking of the fault point voltage by the output voltage of the energy storage converter during the fault, ensuring that both the transient and steady state currents of the converter are within the required range. The simulation cases and simulation results verify the correctness and effectiveness of the proposed control method.