Solar Micro-Inverter
Photovoltaic inverters convert the direct current (DC) generated by photovoltaic modules into alternating current (AC) and supply it to local loads or the grid. Inverters can be categorized into centralized inverters, string inverters, and microinverters based on their technical routes. Currently, the market mainly features centralized inverters and string inverters.
Microinverters were first developed by the American company Enphase in 2006. The main goal of developing microinverters was to improve the output power of each component and improve the efficiency of string inverters, which had low power generation efficiency.
Compared with centralized or string inverters, the main feature of microinverters is the full parallel circuit design that connects to each module, enabling individual control of each module. This allows for maximum power point tracking for each module, which is then inverted and fed into the AC grid.
Microinverters are generally smaller in power, but have higher power generation efficiency and safety. Depending on the number of connected components per microinverter, they can be divided into five categories: one-to-one, one-to-two, one-to-four, one-to-six, and one-to-eight.
Advantages of Microinverters
1) Greater safety: components are connected in parallel, and there is no voltage addition between components, with the maximum voltage being only 60V. There is no direct current high voltage, so it is safer. The microinverter completely solves the problem of fire caused by high-voltage direct current arcing, and also solves the rescue obstacle. However, the string inverter has a cumulative high voltage of 600-1500V, with a high risk of electric shock and fire.
2) Better economic performance: In terms of economic performance, it mainly reflects the initial installation cost and IRR (internal rate of return) comparison. As high-power modules gradually become the mainstream in the distributed market, and the large-scale promotion of one-to-many micro-inverters, the single-W price of micro-inverters has been continuously decreasing, especially in the small and medium power range, where micro-inverters have better economic performance.
Microinverters have a lower initial investment cost than string inverters + optimizers for projects below 20kW; from the IRR perspective over the entire life cycle, microinverters have higher IRR than all the solutions of string inverters for projects below 20kW.
Compared to central inverters and string inverters, micro inverters are more efficient because they perform maximum power point tracking for each individual photovoltaic module, while micro inverters have a low light intensity requirement for startup, and they generate higher power output in partial shading and on rainy days, so the efficiency of micro inverters is over 80%, which means they can generate more electricity. The power gain of micro inverters is 10%-20%.
3) More flexible and digitally advanced: Micro inverters can achieve individual component-level control, shutdown, and data collection, making them more flexible and digitally advanced. This includes more flexible operation and maintenance in the later stage, with household maintenance being safe and convenient for a single person.
Market size of microinverters
1) The global photovoltaic (PV) installed capacity continues to grow at a high speed:① After continuous technological progress, the current per-Watt price of PV generation has become economically competitive. In the future, the PV industry will continue to reduce costs and increase efficiency, and the economic feasibility of PV generation will continue to improve.② Governments of various countries generally have a favorable attitude towards renewable energy industries such as PV, and are constantly issuing various industrial and fiscal policies to support the development of the PV industry. It can be said that the world is supporting the development of the PV industry, and the energy revolution led by PV is unstoppable. The installed capacity of PV will continue to grow rapidly. It is expected that the annual new installed capacity of global PV will grow by 30%-40% from 2021 to 2025.
The compound annual growth rate (CAGR) of micro inverters in the industry over the next few years is no less than that of energy storage and far exceeds the overall industry growth rate of inverters.
2) Continuous improvement in penetration rate: The proportion of distributed photovoltaics will continue to increase, and the penetration rate of micro inverters in distributed scenarios will also continue to increase rapidly.
In 2021, the global penetration rate of distributed micro inverters was only around 7%左右， of which the household penetration rate was around 11%左右， and the industrial and commercial penetration rate was as low as 2%. It is expected that the penetration rate of micro inverters in distributed generation will be around 10%左右 in 2022, with a total of about 10GW. Currently, the penetration rate of micro inverters in the United States is as high as 50%； the penetration rate in Europe and Latin America is around 10%； domestic micro inverters in China have not yet truly started, with a penetration rate of 0.0%.
According to estimates from multiple institutions, the penetration rate of micro inverters is expected to reach 17% by 2025, reaching 45GW. The compound annual growth rate of micro inverter shipments from 2021 to 2025 is expected to be 80%. Taking into account the price factor, it is expected that the market size of the micro inverter industry will exceed 50 billion yuan by 2025, with a compound annual growth rate of 60% for the micro inverter market size from 2021 to 2025.
Device Recommendations
Traditional microinverters use ultrafast recovery diodes in the MPPT unit, which has the advantage of low cost; as the cost of SiC diodes continues to drop, most microinverters now use SiC diodes, which have an inverse recovery time of approximately zero compared to ultrafast recovery diodes. SiC diodes have extremely low reverse recovery loss, reducing device heating and improving reliability, resulting in higher overall value.
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