First, the customers should start from the application of distributed photovoltaic scenarios to match / choose inverter, and make it play the greatest role according to local conditions. How to choose inverter models? Single or three phase? These are dependent on the roof space, as we know, generally the family roof or courtyard hold a small capacity, in such cases, the single-phase or three-phase grid cascade photovoltaic inverter are chosen as a favorite; in case that roof space is big enough, one may make choice of three-phase inverter.
And under conditions such as industrial and commercial roofs, fields on the hill and greenhouses, which standing in irregularly orientated, prone to partial shade ，the three-phase grid cascade photovoltaic inverter are chosen in general. And for vast land and desert, the centralized box inverter model is proposed.
Second, efficient power generation is an even more critical factor for the select of inverter. To achieve efficient photovoltaic power generation, it relies on the inverter conversion efficiency. At ordinary times, we often see inverter efficiency specifications as in maximum and weighted. What is the difference between the two ideas? The maximum efficiency is the best performance of the inverter in the best case, while weighted efficiency is its integrated performance. It is a comprehensive implement to inverter that to achieve efficient power generation, in this way it seems that the weighted efficiency is more of a manufacturing significance. And here also we face a key factor MPPT efficiency---- of dynamic and static. For now, the static MPPT efficiency algorithm is not much problem, most manufacturers can achieve. The real key is dynamic MPPT efficiency, as a matter of fact, in the actual working environment for inverter, lighting, temperature and other conditions are constantly changing. The above mentioned conversion efficiency and MPPT efficiency will affect the inverter power generation, can extend the power generation time, thereby increasing power generation.
Third, as distributed photovoltaic system is usually near its user’s side, therefore, it becomes an important factor in the selection of the inverter, because of safety and reliability. In case of a 25-year life photovoltaic system buildup, measures should be taken as below:
1. To achieve cascade block monitoring, this requires fine monitoring, timely detection of line failure, component failure, shading and other issues.
2. Inverter should have a protective function, to be able to prevent fire, such as color steel tiles roof and mountain scene prone to fire, to lightning, such as roof and mountain and other places prone to thunderstorms; to be able to prevent PID and Electric shock.
3. Inverter thermal design by electronic device life 10 ℃ law: the device ambient temperature for each rise of 10 ℃,its life is reduced by half.
4. To consider the inverter process design and selection, it’s very necessary with a good design and a large number of experimental verifications, such as waterproof, dust, high and low temperature and so on so forth.
Fourth, grid-friendly should be put into consideration when selecting the inverter. In the photovoltaic system, inverter is an important tool to convert light energy into electric energy, in its front connected with light and at the rear connected with the power grid. Grid friendly inverter is characterized in three specifications----power factor, current harmonics and DC component.
For power factor PF, under normal circumstances PF = 1 is the best;
The smaller the current harmonic THDi is, the more close to the sine;
DC component DCI, the smaller it is the more ideal.
Fifth, for intelligent operation and maintenance, we provide different monitoring programs for different scenarios, now remote monitoring, online customer service; remote operation and maintenance are available in our team.
