With the continuous development of photovoltaic grid-connected power generation, in the case of distributed grid-connected power generation, micro grid-connected inverters are a key equipment. Therefore, the selection of miniature grid-connected inverters is also particularly critical. There are many domestic companies engaged in R&D and production of micro grid-connected inverters, and their technology and quality are also uneven. At the same time, because users are not very familiar with the performance parameters of micro grid-connected inverters, they are often just selected from the price. This will not only affect the benefits of its photovoltaic power generation, but will also cause poor grid connection and affect the use of electricity in the power grid.
Domestic micro grid-connected inverter manufacturers can be broadly classified into three types. One is the earlier research and development of micro grid-connected inverters or direct connection with foreign technologies, such as Ying Weili, Shanneng, Nortel, etc. The second category is engaged in the production of in-vehicle inverters or other products, and switched to micro grid-connected inverters. The third category is independent and independent research and development, learn from other families successful experience, unique rising star.
The structure of the micro-grid inverter is mostly boosted by the front stage and generates a bow wave. The rear stage uses a full-bridge to achieve level reversal (this is also the case in Enphase products), but the boost and header of the front stage The wave generation is somewhat different, and there are roughly the following types:
1. Staggered Flyback: The front stage consists of two flyback circuits that run in parallel. This is true of Enphase, English Wealth, and Kannon.
2. Use UCC2806, or UCC3806 to achieve the current loop, the control chip only input a reference waveform, the control chip is generally a low-end microcontroller. Strictly speaking, this architecture can not be called digital power, because its main control is still analog chips such as UCC2806 or UCC3806 to achieve. This scheme is similar to domestic fishing machines, welding machines and on-vehicle inverters. It belongs to a very low-end product and its grid-connected output power quality is very poor. However, the cost of such products is very low, so it is heavily flooded with the domestic market.
3. Use other architectures: such as SunSource's newly introduced mini-grid inverters fall into this category. Its predecessor uses a push-pull forward circuit and introduces a clamp capacitor to control the peak voltage of the front-stage MOSFET below 100V. The MOSFET with a pre-stage 150V withstand voltage can be operated safely and safely. It is the same 1200V silicon carbide diode as Enphase and Ying Weili, etc. The performance is beyond, the whole machine is equipped with electronic potting glue, no noise during operation, long working time, and will not run for a while like UCC2806 and other controlled products. protection. When SunSource introduced this product, the price was positioned between the UCC2806 product and the fault-added flyback product, but its performance was close to staggered flyback products. Suitable for 180-320W 60Cell or 72Cell photovoltaic panels.
The output power factor (PF) of the grid-connected inverter is defined as the COS value between the output waveform of the grid-connected inverter and the waveform of the grid. We know that COS(0)=1, that is, the closer the PF is to 1, the Explain the smaller the grid-connected phase shift. SunSource's micro-grid inverter output PF can reach up to 0.997.
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