A High-Efficiency MOSFET Transformer Less Inverter for Non isolated Micro inverter Applications
MOSFET-based inverter topologies suffer from one or more of these drawbacks: MOSFET failure risk from body diode reverse recovery, increased conduction losses due to more devices, or low magnetic utilization. By splitting the conventional MOSFET based phase leg with an optimized inductor, this paper proposes a novel MOSFET-based phase leg configuration to minimize these drawbacks. Based on the proposed phase leg configuration, a high efficiency single-phase MOSFET transformer less inverter is presented for the PV micro inverter applications. The pulse width modulation (PWM) modulation and circuit operation principle are then described. The common-mode and differential-mode voltage model is then presented and analyzed for circuit design.
There have been quite a few new transformerless PV inverters topologies, which eliminate traditional line frequency transformers to achieve lower cost and higher efficiency, and maintain lower leakage current as well. For highpower- level transformerless inverters, most of them adopt neutral point clamp (NPC) or T-type three-level inverter topologies, which require high dc-bus voltage and are not suitable for low power PV inverter application. For the lower power level transformerless inverters, most of the innovative topologies use super junction metal–oxide–semiconductor field-effect transistor (MOSFET) to boost efficiency. With super junction MOSFETs, the conduction and switching losses are lowered. However, with the poor reverse recovery from MOSFET’s slow body diode, MOSFET-based phase legs will have a risk of device failure, which is related to high dv/dt, di/dt and phase-leg shoot through from gating voltage false trigging on.
The proposed transformer less inverter has no dead-time requirement, simple PWM modulation for implementation, and minimized high-frequency A 250Whardware prototype has been designed, fabricated, and tested in two-stage non-isolated micro inverter application.
Experimental results demonstrate that the proposed MOSFET transformer less inverter achieves 99.01% peak efficiency at full load condition and 98.8% CEC efficiency and also achieves around 98% magnetic utilization. Due to the advantages of high efficiency, low CM voltage, and improved magnetic utilization, the proposed topology is attractive for two-stage non-isolated PV micro inverter applications and transformer less string inverter applications.
TOOLS AND SOFTWARE USED:
Baifeng Chen, Student Member, IEEE, Bin Gu, Member, IEEE, Lanhua Zhang, Student Member, IEEE, Zaka Ullah Zahid, Student Member, IEEE, Jih-Sheng (Jason) Lai, Fellow, IEEE, Zhiling Liao, and Ruixiang Hao, Member, IEEE, “A High-Efficiency MOSFET Transformerless Inverter for Nonisolated Microinverter Applications” , IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 7, JULY 2015