The choice of solar inverter

Due to the diversity of buildings, it will inevitably lead to the diversity of solar panel installations. In order to maximize the conversion efficiency of solar energy while taking into account the beautiful appearance of the building, this requires the diversification of our inverters to achieve the best way of solar energy. Conversion. The most common solar inverter methods in the world are: centralized inverters, string inverters, multi-string inverters and component inverters. Now we will analyze the applications of several inverters.

Centralized inverters are generally used in systems with large photovoltaic power stations (》10kW). Many parallel photovoltaic strings are connected to the DC input of the same centralized inverter. Generally, three-phase IGBT power modules are used for high power. The lower power uses field-effect transistors and the DSP conversion controller to improve the quality of the generated electric energy, making it very close to the sine wave current. The biggest feature is the high power and low cost of the system. However, it is affected by the matching of photovoltaic strings and partial shading, resulting in the efficiency and power capacity 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 photovoltaic unit group. The latest research direction is the use of space vector modulation control and the development of new inverter topology connections to obtain high efficiency under partial load conditions.

On the SolarMax centralized inverter, you can attach a photovoltaic array interface box to monitor each photovoltaic windsurfing string. If one of the strings is not working properly, the system will transmit this information to the remote controller At the same time, this 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.

String inverters have become the most popular inverters in the international market. The string inverter is based on the modular concept. Each photovoltaic string (1kW-5kW) passes through an inverter, has maximum power peak tracking at the DC end, and is connected in parallel at the AC end. Many large photovoltaic power plants use string inverters. The advantage is that it is not affected by module differences and shadows between strings, and at the same time reduces the optimal working point of photovoltaic modules

Mismatch with the inverter, thereby increasing the amount of power generation. These technical advantages not only reduce the cost of the system, 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 a single string of electric energy cannot make a single inverter work in the system, several sets of photovoltaic strings are connected together, and one or several of them can work. , So as to produce more electricity. The latest concept is that several inverters form a “team” to replace the “master-slave” concept, which makes the reliability of the system a step further. Currently, transformerless string inverters have taken the lead.

Multi-string inverter takes the advantages of centralized inverter and string inverter, avoids its shortcomings, 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. These DCs are converted into AC power by an ordinary DC-to-AC inverter and connected to the grid. Different rated values of photovoltaic strings (such as: different rated power, different number of components in each string, different manufacturers of components, etc.), photovoltaic modules of different sizes or different technologies, and strings of different directions (such as : East, South and West), different inclination angles or shadows, can be connected to a common inverter, and each string is working at their respective maximum power peak.

At the same time, the length of the DC cable is reduced, the shadow effect between the strings and the loss caused by the difference between the strings are minimized.

The component inverter is to connect each photovoltaic component to an inverter, and each component has a separate maximum power peak tracking, so that the component and the inverter are better matched. Usually used in 50W to 400W photovoltaic power plants, the total efficiency is lower than string inverters. Since it is connected in parallel at the AC, this increases the complexity of the wiring on the AC side and is difficult to maintain. Another issue that needs to be solved is how to connect to the grid more effectively. The simple way is to directly connect to the grid through an ordinary AC socket, which can reduce the cost and equipment installation, but often the safety standards of the grid may not allow it. In doing so, the power company may object to the power generation device being directly connected to the ordinary sockets of ordinary household users. Another factor related to safety is whether an isolation transformer (high frequency or low frequency) is required, or a transformerless inverter is allowed. This inverter is most widely used in glass curtain walls.