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Due to the diversity of buildings, it will inevitably lead to the diversity of solar panel installation. In order to maximize the conversion efficiency of solar energy and take into account the beautiful appearance of the building, this requires the diversification of our inverters to achieve the best way of solar energy. Conversion. Currently, the world's more popular solar inverters are: centralized inverters, string inverters, multi-string inverters, and component inverters. Now we will analyze the applications of several inverters.
Centralized inversion
For centralized inverters commonly used in systems with large photovoltaic power stations (>10 kW), many parallel PV strings are connected to the DC input of the same centralized inverter. Generally, three-phase IGBT power modules with high power are used. Smaller power uses field-effect transistors and uses a DSP conversion controller to improve the quality of the power produced, making it very close to sine-wave currents. The most important feature is the high power and low cost of the system. However, due to the matching of the photovoltaic strings and the partial shading effect, the efficiency and the electrical capacity of the entire photovoltaic system are caused. At the same time, the reliability of power generation of the entire photovoltaic system is affected by the poor working condition of one photovoltaic unit group. The latest research directions are the use of space vector modulation control and the development of new inverter topology connections to achieve high efficiency under partial load conditions.
In the SolarMax centralized inverter, a photovoltaic array interface box can be attached to monitor each string of photovoltaic windsurfing strings. If one of the strings is not working properly, the system will The information is transmitted to the remote controller. At the same time, the string can be stopped by 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.
Inverted string
String inverters have become the most popular inverter on the international market. The string inverter is based on the modular concept. Each photovoltaic string (1kW-5kW) passes through an inverter and has maximum power peak tracking at the DC end and parallel connection at the AC end. Many large-scale photovoltaic power plants use string inverters. The advantage is that it is not affected by the module differences and shading between the strings, and at the same time, the best working point of the photovoltaic module is reduced.
Mismatched to the inverter, thus increasing the amount of power generated. 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" was introduced between strings, making it possible to link several sets of photovoltaic strings together to make one or several of them work when a single string of electrical energy cannot make a single inverter work. , which will produce more electricity. The latest concept is that several inverters form a “team†instead of a “master-slave†concept, making the reliability of the system one step further. At present, transformerless string inverters have taken a dominant position.
Multi-string inversion
Multi-string inversion takes advantage of centralized inverter and string inversion and avoids its disadvantages. It can be applied to several kilowatts of photovoltaic power stations. In the multi-string inverter, different individual power peak tracking and DC-to-DC converters are included. These DCs are converted into AC power through an ordinary DC-to-AC inverter and connected to the power grid. Photovoltaic strings have different rated values ​​(eg, different rated power, different number of components per string, different manufacturers of components, etc.), different sizes or different technologies of photovoltaic modules, and strings of different directions (eg, : East, South and West, different dips or shadows, can all be connected to a common inverter, and each string works at their respective maximum power peak.
At the same time, the length of the DC cable is reduced, shadowing effects between strings, and losses due to differences between strings are minimized.
Component Inverter
The component inverter connects each PV module with one inverter, and each component has a single maximum power peak tracking, so that the module and the inverter cooperate better. Typically used for photovoltaic power stations from 50W to 400W, the total efficiency is lower than string inverters. Because they are connected in parallel at the exchange, this increases the complexity of the connection on the exchange side and makes maintenance difficult. Another problem that needs to be solved is how to integrate the grid more effectively with the grid. The simple method is to connect the grid directly through an ordinary AC outlet. This can reduce the cost and installation of the equipment, but often the safety standards of the grids around the country may not allow it. In doing so, the power company may oppose the direct connection of the power generating device to an ordinary outlet of an ordinary home user. Another safety-related factor is whether it is necessary to use an isolation transformer (high or low frequency) or to allow the use of transformerless inverters. This inverter is most widely used in glass curtain walls.
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