Ultra-compact Power Pulsation Buffer for single-phase DC/AC converter systems

In single-phase power conversion systems, typically bulky electrolytic capacitors are installed in order to cope with the intrinsic double-line frequency power pulsation. However, since the voltage ripple at the dc bus is typ. limited to just a few percent of the nominal voltage, only a small fraction of the actually stored energy in the capacitors is used for the power decoupling. In this paper an auxiliary buffer converter is employed, shifting the double-line frequency power pulsation away from dc bus to a buffer capacitor. Being relieved from strict voltage ripple requirements, a larger voltage ripple is allowed across the buffer capacitor, significantly reducing the capacitance requirement. In this paper an ultra compact Power Pulsation Buffer (PPB) is designed for a 2kW PV-inverter application by means of a comprehensive Pareto optimization. Besides compensating the power pulsation, the PPB must be able to quickly stabilize the dc bus in case of abrupt load variations and maintain an average buffer capacitor voltage. In this paper, a novel cascaded control structure is presented, meeting all aforementioned control objectives. A constructed prototype of the optimized PPB is presented in the paper and experimental measurements verify the outstanding performance of the proposed control system.