Abstract
Unlike a dc distribution system with a three-phase inverter, the one with a single-phase inverter to regulate the dc-bus voltage will result in high voltage ripple. This paper presents dc-bus voltage regulation for a dc distribution system integrated with a single-phase bidirectional inverter. In a dc distribution system, a bidirectional inverter controls its inductor current to balance power flow and to regulate the dc-bus voltage. To reduce the line current distortion and the influence of dc-bus ripple voltage on regulation control, one line-cycle regulation approach (OLCRA) and quarter line-cycle regulation approach (QLCRA) are proposed. The OLCRA can regulate the dc-bus voltage with low ac current distortion, and the QLCRA can regulate the voltage under a fast load variation and with voltage ripple. Moreover, for enhancing the operational reliability and availability of the dc distribution system, the bidirectional inverter shifts the dc-bus voltage to different levels according to the load conditions. This shift mechanism can also reduce the possibility of entering under or over voltage protection without increasing dc-bus capacitance. In addition, the design of dc-bus capacitance for the system and the online estimation of the capacitance at the system startup and under the aging effect are proposed, which can help regulate the dc-bus voltage tightly in the long-Term operation. The stability analysis of the dc-bus voltage regulation under capacitance variation is also addressed. Experimental results measured from a 5-kW system with a single-phase bidirectional inverter have verified the analysis and discussion.