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Solar inverters are generally divided into centralized inverters, string inverters, multi-string inverters, and component inverters. The principles and differences of each inverter are briefly described below.
1. Centralized inverters are generally used in large-scale photovoltaic power plants (>10kW) systems. Many parallel photovoltaic strings are connected to the DC input end of the same centralized inverter. Generally, three-phase IGBT power is used for large-scale inverters. Modules, which use less powerful field-effect transistors, use DSP conversion controllers to improve the quality of the generated power, making it very close to a sine wave current. The biggest feature is the system's high power and low cost. However, it is affected by the matching of photovoltaic strings and partial shading, resulting in the efficiency and power generation of the entire photovoltaic system. At the same time, the power generation reliability of the entire photovoltaic system is affected by the poor working status of a certain photovoltaic unit group. The latest research directions are the use of space vector modulation control and the development of new topological connections of inverters to obtain high efficiencies under partial load conditions. On the SolarMax centralized inverter, an interface box for a photovoltaic array can be attached to monitor each string of photovoltaic panels. If one of the strings is not working properly, the system will The information is transmitted to the remote controller, and at the same time, the string can be stopped through remote control, so that the failure of a string of photovoltaic strings will not reduce and affect the work and energy output of the entire photovoltaic system.
2. String inverters have become the most popular inverters in the international market. The string inverter is based on the concept of modularization. Each photovoltaic string (1kW-5kW) passes through an inverter, which has maximum power peak tracking at the DC end and is connected in parallel to the grid at the AC end. Many large PV plants use string inverters. The advantage is that it is not affected by module differences and shading between strings, and at the same time reduces the optimal operating point of photovoltaic modules. A situation that does not match the inverter, thereby increasing the power generation. These technical advantages not only reduce the system cost, but also increase the reliability of the system. At the same time, the concept of "master-slave" is introduced between the strings, so that when the power of a single string of the system cannot make a single inverter work, connect several groups of photovoltaic strings together and let one or several of them work , so as to produce more electricity. The latest concept is that several inverters form a "team" to replace the concept of "master-slave", which makes the reliability of the system a step further.
3. The multi-string inverter takes the advantages of centralized inverter and string inverter, avoids its disadvantages, and can be applied to photovoltaic power stations of several kilowatts. In the multi-string inverter, different individual power peak tracking and DC-to-DC converters are included, and these DCs are converted into AC power by a common DC-to-AC inverter and connected to the grid. Different ratings of photovoltaic strings (such as: different rated power, different number of modules per string, different manufacturers of modules, etc.), different sizes or different technologies of photovoltaic modules, different orientations of the strings (such as : east, south and west), different inclinations or shading, can be connected to a common inverter, and each string works at its respective maximum power peak. At the same time, the length of the DC cable is reduced, and the shading effect between the strings and the loss caused by the difference between the strings are minimized.
4. The module inverter is to connect each photovoltaic module with an inverter, and each module has a separate maximum power peak tracking, so that the cooperation between the module and the inverter is better. Usually used in 50W to 400W photovoltaic power stations, the total efficiency is lower than that of string inverters. Since it is connected in parallel at the AC side, this increases the complexity of the connection on the AC side and makes maintenance difficult. Another problem that needs to be solved is how to connect to the grid more effectively. The simple way is to connect to the grid directly through an ordinary AC socket, which can reduce the cost and equipment installation, but often the safety standards of the grid in various places may not allow In doing so, the power company may object to the direct connection of the generating unit to the common socket of the common household. Another safety-related factor is whether an isolation transformer (high frequency or low frequency) is required, or allows the use of a transformerless inverter. This inverter is most widely used in glass curtain walls.
The solar inverter methods are classified into the above four types, and it is especially important to choose a solution that suits you.
