Low-Cost, Multi-Input, Single Resonant Tank LLC Converters

Abstract

Researchers at the University of Central Florida have developed a new multi-input power DC-DC converter that uses a single LLC resonant tank to transfer energy and perform power conversion from multiple sources. With other technologies, the number of switches and circuit components increases with each added power source, thus raising total costs and reducing reliability. In comparison, the new UCF technology allows several photovoltaic (PV) panels and battery storage to share the same resonant tank without the need for more circuit components. Thus, it provides a more reliable and cost-effective means of improving power density for conventional inverters, microinverters, and motor controllers.

Technical Details

The UCF power converter comprises a single LLC resonant tank that includes an inductor, a capacitor, and the magnetizing inductance of a transformer. Bridge circuits can receive power from two or more PV panels and external batteries. The power converter employs a phase-shift pulse width modulation (PWM) control to implement independent maximum power point tracking (MPPT) for each PV panel. Zero-voltage-switching (ZVS) occurs in all switches over the entire range of source voltage and load conditions. Also, voltage stress across switches does not exceed the input PV voltage. To demonstrate the performance of the topology, the researchers built a 500-W prototype with an input voltage range between 25 V to 50 V and an output voltage regulated at 440 V DC. Experimental results show that the converter can achieve peak efficiency of 95.8 percent while maintaining a wide input voltage range and implementing MPPT for each PV panel.

Partnering Opportunity

The research team is looking for partners to develop the technology further for commercialization.

Stage of Development

Prototype available.

Benefit

Market Application