Single-Stage Bi-Directional DC-AC Converter and Its Input Current Ripple Suppression for Battery Energy Storage Systems

AC distributed generation systems (DGSs) typically require bidirectional DC-AC converters to interface with the common AC bus. However, the DC-side second harmonic current significantly degrades the converter’s power density and shortens battery lifespan. To address this issue, this paper proposes a single-stage bidirectional DC-AC converter for battery applications, employing an active power decoupling-based unipolar phase-shifted SPWM control strategy. The operational principle involves rectifying the sinusoidal pulse-width-position modulated (SPWPM) waveform from the high-frequency (HF) transformer into SPWM pulses during either the positive or negative half-cycle via a cycloconverter circuit. By analyzing the rising and falling slopes of the decoupling inductor current, real-time duty cycle allocation of the power decoupling bridge arm switches is implemented, effectively suppressing the DC-side second harmonic current. Additionally, design criteria for the decoupling capacitor and inductor are derived. Experimental results from a 1 kVA 96 V DC/220 V 50 Hz AC hardware-in-the-loop (HIL) platform validate the converter’s good performance, characterized by single-stage power conversion efficiency, low DC-side second harmonic current distortion, high-frequency electrical isolation, and high-quality grid-connected current. These findings provide a promising solution for battery-based AC distributed renewable energy systems and electric vehicle charging/ discharging interfaces.