Family of ZC-ZVS converters with wide voltage range for renewable energy systems

This paper presents a new family of soft switched pulse-width modulated (PWM) quadratic converters which are suitable for systems with a wide fluctuating DC input voltage range, e.g. photovoltaic (PV) and fuel cells systems. In the proposed scheme, an auxiliary circuit is added to the conventional quadratic converters and used to achieve soft-switching for both the active and passive switches while not incurring any additional losses due to the unique location of the snubber capacitor and inductor in the auxiliary circuit. The active switches in the new converters are turned-on with zero-current and zero-voltage switching (ZC-ZVS) and turned-off with zero-voltage switching (ZVS). The diodes commutate softly and the reverse-recovery problems are greatly alleviated. Besides operating at a constant frequency and with reduced commutation losses, the proposed converters are subjected to minimum voltage and current stresses and have output characteristics similar to their hard-switching PWM quadratic converters counterparts. As a result, there are no additional conduction losses in the semiconductor devices. A quadratic boost converter adopting this technique is presented as an example. The principle of operation, theoretical analysis, design equations, simulation and experimental results of the new ZC-ZVS quadratic boost converter are provided to verify the performance of this new family of converters.

► A family of soft switched pulse-width modulated quadratic converters is proposed.
► The voltage gain is extended without using extreme duty-cycles and transformer.
► The active switches in the new converters are turned on and off softly.
► The converters can achieve both high efficiency and wide input voltage range.
► The proposed converters are suitable for photovoltaic and fuel cells systems.