Get More Power from Your Low Power Inverters

Abstract

A group of UCF researchers has developed a three-phase micro-inverter for low power applications, specifically batteries, solar panels, or fuel cells, with higher power density and efficiency. The entirely new control approach eliminates the need for expensive additional parts often required of hard switched inverters, such as SiC diodes or additional inductors, thereby increasing the power density and solving the light load efficiency problem. The three-phase grid-tied power micro-inverter provides a three-level control scheme. Phase skipping control is one of the control schemes, and it selectively injects power through each phase, ensuring that the phases' received power operates at a greater percentage of load capacity, thus significantly improving the micro-inverters power efficiency. For the first time, a power inverter employs a hybrid zero-voltage switching (ZVS) current control technique for a switching inverter and soft switched controls which increases the switching frequency and yields higher power conversion efficiency. Now, achieve power conversion with lower costs, higher reliability, and higher power density.

Technical Details

Micro-inverter use has been limited to small scale, single-phase residential and commercial PV installations. By extending the micro-inverter concept to large size PV installation where three-phase AC connection is used, advantages such as individual variable frequency maximum power point tracking (MPPT) to determine a switching frequency for a resonant power converter, redundant system architecture, ease of installation, removal of unreliable electrolytic capacitors, and less DC distribution losses can be gained. To make the idea of PV farm architecture based on three-phase micro-inverters feasible, a high efficiency, low cost, high reliability, high compact micro-inverter was designed and built. Invented three-phase micro-inverter can be used for any PV power plant, from small scale to proof applications for commercial building to large scale PV power plants.

Benefit

Market Application

Publications

• Efficiency Improvement of Grid-Tied Inverters at Low Input Power Using Pulse-Skipping Control Strategy, IEEE Transactions on Power Electronics, December 2010, vol. 25, no. 12, pp.3129-3138
• High Efficiency Dual Mode Current Modulation Method for Low Power DC/AC Inverters, IEEE Transactions on Power Electronics, June 2014, vol. 29, no. 6, pp. 2638-2642