SBIR/STTR Award attributes
This proposal primarily targets a well-rounded approach of ‘design for manufacturing’ and ‘design for reliability’ for photovoltaic (PV) microinverters by leveraging the fast-switching and low-loss properties of the emerging wide band gap (WBG) Silicon Carbide (SiC) and Gallium Nitride (GaN) power semiconductors. It is aimed at substantially reducing the cost of bill of material (BOM) from $0.25/W to less than $0.11/W, while enhancing the reliability of residential-use PV micro-inverters. We propose a single-stage isolated DC-AC matrix inverter configuration for the microinverter that does not require bulky passive power transfer inductors and the intermediate DC link capacitor. The design comes with a high degree of modularity and configurability, where multiple power converter units can be paralleled on the output side to scale up the power level. The proposed microinverter unit with a maximum power rating of 400W will be capable of interfacing a PV panel of an output between 20V and 60V DC with a single-phase 120V as well as 240V nominal RMS AC grid. Further, the electrolytic DC capacitors, conventionally used on the input (PV) side will be replaced by a GaN half-bridge based actively controlled power pulsating buffer (PPB) solution that significantly reduces the capacitance requirement, which is then realized by ceramic capacitors with enhanced reliability – thus increasing the mean time to failure (MTTF) as well as reducing the maintenance cost. The proposed solution (rated for 400W) is expected to demonstrate over 97% peak efficiency, 96.5% rated load efficiency, ~60% reduction in BOM cost, and 25% increase in power density compared to off-the-shelf state-of-the-art. Further, the microinverter will be designed with all surface mount components and planar magnetics technology, which highly automate the manufacturing and assembly line without having any need for additional investment and upfront cost of adding new machines. In Phase I, we will be performing (a) design optimization of resonant-matrix single-phase inverter, (b) high-density loss-minimized PCB-integrated planar magnetics with stray capacitance minimization and (c) high-density active buffer solution for electrolytic capacitor elimination for reliability enhancement.
