Transformerless voltage clamp circuit applied to a soft switched DC/AC current source inverter

The selection of a regenerative, battery powered, DC/AC converter for uninterruptible power supply or traction applications is a compromise among the following major issues: efficiency, output waveforms quality, ruggedness and cost. A zero current switching current source inverter represents a suitable solution in terms of losses and output wave shape; furthermore, the opportunity to use thyristors maintaining the capability to withstand short circuit contains cost and confers ruggedness. Ishikawa proposed an effective topology, but this topology requires a transformer with very low leakage inductance to contain the voltage stress of switching devices. This paper proposes and analyzes a modified zero current switching DC/AC current source inverter. The proposed topology includes a transformerless voltage clamp circuit overcoming the aforementioned problem. Furthermore, the circuit obtains a zero current turn off for each switch. The paper overviews the zero current switching DC/AC current source inverter, proving its functionality by means of numerical simulations