As a new type of photovoltaic grid-connected device, photovoltaic microinverters have broad development prospects. While pursuing the design goals of long-term, high-efficiency, and stable operation, the size and cost of the equipment should also be taken into account.
The following aspects should be considered when designing a micro inverter:
1. Power density: Micro inverters require high power density, and the overall circuit should have a small size.
2. Conversion efficiency: Since the energy conversion efficiency of photovoltaic cells is currently not high, every 1% increase in the efficiency of photovoltaic grid-connected equipment can bring huge economic value.
3. Reliability: The mean time to first failure (MTFF) of centralized grid-connected inverters is typically 5 years, and the mean time to failure (MTBF) is approximately 10 years. Photovoltaic cells have a lifespan of over 20 years; therefore, the lifespan design specifications of micro-inverters must be comparable to those of photovoltaic cells to demonstrate the advantages of this solution. Their MTBF should be greater than 20 years, and their MTFF should be greater than 10 years.
4. Cost: The AC module system equips each photovoltaic panel with a micro-inverter, which requires the micro-inverter to be low-cost and contain fewer components in the circuit. Its controller must be able to handle all control, communication, and computing tasks while also being inexpensive.
Significant progress has been made in the research of traditional photovoltaic grid-connected systems, and these achievements can be drawn upon in the design of micro-inverter grid-connected systems. This paper will conduct specific research and analysis on different micro-inverter main circuits.
