Coupled Inductor Based Boost Microinverter With Dual Mode Time Sharing Operation for Renewable Energy Applications

Abstract

Household power conversion stages process significant amounts of power when they add up to form a microgrid. Microinverters are considered one of the best choices to utilize the renewable energy harvested power. Microinverter integration encounters several challenges when interfaced with expanding microgrids. This paper proposes a coupled inductor-based boost microinverter operating in dual mode time sharing technique for renewable energy applications. It is composed of an absolute sinewave modulated voltage boost converter and series capacitor connected to the secondary winding of the coupled inductor followed by a single-phase Full bridge inverter. The coupled inductor integration allows a significant reduction in current ripple and improved energy conversion efficiency. In the proposed microinverter, the DC link voltage is not required to be constant, instead, it process an absolute sinewave modulated voltage and then it is unfolded to AC and fed into the grid. The DC link capacitor is substituted by an efficient AC thin film type capacitor. The dual mode time-sharing principle intends to reduce the switching losses of the microinverter and consequently achieves high conversion efficiency. The proposed converter’s analysis, design, and simulation are validated on a 2.0 kW setup system using PSIM simulation software. The feasibility and performance of this new microinverter topology is proved experimentally via laboratory prototype. The current ripple can be reduced to one half in case of matching coupled inductor primary and secondary windings compared to the typical boost converter. In another scenario, the current ripple can be fully eliminated in either of the coupled inductor windings when winding inductance equals to the mutual inductance. The proposed microinverter topology offers a notable enhancement in power conversion performance that reached 97%. In addition, a high-quality sinusoidal output current waveform of 1.1% total harmonic distortion is achieved.

Keywords

• Microinverter
• dual mode
• time-sharing
• coupled-inductor
• boost converter
• renewable energy