Bidirectional series ac-link inverter

This paper proposes a novel bi-directional inverter, named series ac-link inverter. This three-phase inverter belongs to a new class of partial resonant ac-link converters in which the link is formed by a series ac inductor/capacitor (LC) pair having low reactive ratings. The input and output of this converter can be either dc, ac, single-phase, or multi-phase. Therefore, they can appear as dc-dc, dc-ac, ac-dc, and ac-ac configurations. In all of these configurations the ac capacitor is the main energy storage element, and the inductor is merely added to facilitate the zero current turn-off of the switches and their soft turn-on. Due to zero current turn-off of the switches in the proposed converter, the use of SCRs with natural commutation is possible as well. Since the current and voltage of the link are both alternating, no bulky dc electrolytic capacitors are required in this converter. This paper mainly focuses on bidirectional dc to three-phase ac conversion. This single-stage inverter can step-up or step down the voltage in a wide range. If galvanic isolation is required a single-phase high-frequency transformer can be added to the link. In the proposed inverter the power can flow in both directions and therefore, it is an excellent candidate for battery-utility interface and electric vehicle applications. In this paper the principles of the operation of the proposed inverter along with its design and analysis is studied. Moreover, the performance of the proposed configuration is evaluated in this paper. Both simulation and experimental results are included in this paper.