Feedforward Compensation of the ESS Low-Frequency Current Ripple in the Three-Ports ANPC Converter

This paper proposes a feedforward control to mitigate the low-frequency current ripple in the secondary dc port current of the three-ports active neutral-point-clamped converter (ANPC-3P). This low-frequency current ripple is caused by the low-frequency voltage ripple at the inverter dc buses. Current ripple is an important design parameter for energy storage systems (ESS) and must be kept low to extend the ESS life cycle. Low-frequency current ripple is difficult to filter and thereby it should be avoided. In this paper, ESS current control system is composed of a proportional-integral (PI) controller associated with a proposed feedforward action. This control scheme is capable of generating a dc current without low-frequency ripple. The ac output current (grid current) is controlled by a resonant controller. The theoretical propositions are validated by simulation results.