First, photovoltaic grid-connected power generation is the mainstream, and over 90% of global solar installation systems are grid-connected power generation systems, and their share is gradually increasing.
Second, there are three types of photovoltaic grid-connected inverter power supply technology: no isolation transformer type; power frequency transformer isolation type; high-frequency transformer isolation type; no isolation transformer-type grid-connected inverter with power generation security, into the exchange Problems such as large DC components in the power grid are gradually banned in most areas. The United States completely prohibits grid-connected inverters without isolation transformers from being connected to the grid. In China, photovoltaic power generation standards also tend to isolate isolated inverters. The share of non-isolated transformer-type grid-connected inverters in the newly installed solar power generation system has gradually declined each year.
Third, in the global solar grid-connected power generation system, each sub-system below 30KW (the output power of the grid-connected inverter power supply) accounts for 93%, and 30KW or more accounts for 7%. The European solar energy industry is currently the world's largest installed capacity, before 2005, there are still some 100KW, 250KW large-scale power frequency transformer isolated grid-connected inverter power supply is in use. There are also more than 100KW power frequency isolation photovoltaic inverter power supply is adopted (master-slave relationship) 1 +1 parallel connection, that is, photovoltaic grid-connected inverter power supply power is 200% of the solar module power, doubled the cost . After 2005, the number of photovoltaic installations in Europe has increased dramatically. In this case, there is basically no application of grid-connected inverters with power frequency transformers of more than 30 kW. What are the reasons? Mainly for the following two points:
1. The maximum availability of inverters isolated by industrial frequency transformers is 0.99999. Once a fault occurs, the maintenance of the machine is difficult and the system cannot generate electricity during the maintenance process. In the development of the European photovoltaic industry, large-scale industrial frequency isolation and grid-connected inverters are used. The power supply (above 30KW) does not pass the test of actual market operation.
2. The larger the power generation subsystem, the more system wiring, the worse the effect of tracking the maximum power point of solar energy, and cannot maximize the efficiency of the solar panel;
Fourth, with the rapid development of the solar energy industry, high-frequency transformer-isolated products have also developed rapidly. In the communications and power industries, as early as 10 years ago, high-frequency transformer-isolated product technology has long since completely replaced power frequency transformer-isolated products (phased communications power supplies). In the past two years, manufacturers of global solar grid-connected inverters are developing high-frequency and pressure-isolated products. Although the high-frequency transformer isolated product has a long development cycle and high technical difficulty, it has great advantages. It saves copper materials, is small in size, light in weight, and can also realize a modular distributed structure, making the availability reach 0.99999999. In the case of ensuring high availability of the system (7 9), a single set of photovoltaic power generation subsystems can do more, such as 40KW, 50KW, 100KW, 200KW and so on. In the next one or two years, the high-frequency transformer-isolated grid-connected inverters will surely occupy the market of photovoltaic grid-connected inverter power supplies.