Selection, use and maintenance of solar inverters

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. Convert. Nowadays, the more popular solar inverter methods in the world are: centralized inverter, string inverter, multi-string inverter and module inverter. Now we will analyze the application situations of several inverters.

Centralized inversion

Centralized inverter is generally used in systems of large photovoltaic power stations (>10kW). Many parallel photovoltaic strings are connected to the DC input end of the same centralized inverter. Generally, three-phase IGBT power modules are used for high power. The smaller ones use field effect transistors and use DSP conversion controllers to improve the quality of the generated power so that it is very close to a sine wave current. The biggest feature is the high power and low cost of the system. However, the efficiency and electrical production capacity of the entire photovoltaic system are affected by the matching of photovoltaic strings and partial shading. 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 inverter topological connections to obtain high efficiency under partial load conditions.

On the SolarMax centralized inverter, a photovoltaic array interface box can be attached to monitor each string of photovoltaic sail panels. If one of the strings is not working properly, the system will The information is transmitted to the remote controller, and this string can be stopped through remote control, so that the failure of one photovoltaic string will not reduce or affect the work and energy output of the entire photovoltaic system.

String inverter

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 to the grid 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 operating point of photovoltaic modules.

Mismatch with the inverter, thereby increasing power generation. These technical advantages not only reduce system costs, but also increase system reliability. At the same time, the concept of "master-slave" is introduced between strings, so that when the power of a single string in the system cannot make a single inverter work, several groups of photovoltaic strings can be connected together to allow one or several of them to work. , thereby producing more electrical energy. The latest concept is that several inverters form a "team" with each other to replace the "master-slave" concept, making the system more reliable. Currently, transformerless string inverters have taken the dominant position.

Multiple string inverter

Multi-string inverter takes the advantages of centralized inverter and string inverter, avoids their disadvantages, and can be applied to photovoltaic power stations with several kilowatts. In the multi-string inverter, different individual power peak tracking and DC-to-DC converters are included. The DC is converted into AC power through a common DC-to-AC inverter and connected to the grid. Different ratings of photovoltaic strings (e.g. 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 (e.g. : east, south and west), different tilt angles or shading, can be connected to a common inverter, with each string operating at their respective maximum power peak.

At the same time, the length of the DC cable is reduced, minimizing the shadowing effect between strings and the loss caused by differences between strings.

Component inverterThe module inverter connects each photovoltaic module to an inverter, and each module has an independent maximum power peak tracking, so that the module and the inverter cooperate better. Usually used in 50W to 400W photovoltaic power stations, the total efficiency is lower than that of string inverters. Since they are connected in parallel at the AC side, this increases the complexity of the wiring on the AC side and makes maintenance difficult. Another thing 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 ordinary AC sockets, which can reduce costs and equipment installation, but often the safety standards of the power grid in various places may not allow it. In doing so, the power company may object to the direct connection of the generating device to an ordinary household socket. Another safety-related factor is whether an isolation transformer (high frequency or low frequency) is required or whether a transformerless inverter is allowed. This inverter is most widely used in glass curtain walls.

Solar inverter use and maintenance

use:

1. Connect and install the equipment strictly in accordance with the requirements of the inverter operation and maintenance instructions. During installation, you should carefully check: whether the wire diameter meets the requirements; whether the components and terminals are loose during transportation; whether the insulated parts are well insulated; whether the system's grounding meets the regulations.

2. The inverter should be operated and used strictly in accordance with the instructions for use and maintenance. In particular: before turning on the machine, pay attention to whether the input voltage is normal; during operation, pay attention to whether the sequence of turning on and off the machine is correct, and whether the indications of each meter and indicator light are normal.

3. Inverters generally have automatic protection for circuit breakage, overcurrent, overvoltage, overheating and other items, so when these phenomena occur, there is no need to shut down manually; the protection points of automatic protection are generally set at the factory, and no need to Adjust again.

4. There is high voltage in the inverter cabinet. Operators are generally not allowed to open the cabinet door, and the cabinet door should be locked at ordinary times.

5. When the room temperature exceeds 30°C, heat dissipation and cooling measures should be taken to prevent equipment failure and extend the service life of the equipment.

Maintenance and inspection:

1. Regularly check whether the wiring of each part of the inverter is firm and whether there is any looseness. In particular, the fan, power module, input terminal, output terminal and grounding should be carefully checked.
2. Once the alarm shuts down, it is not allowed to start up immediately. The cause should be found out and repaired before starting up. The inspection should be carried out strictly in accordance with the steps specified in the inverter maintenance manual.

3. Operators must receive special training and be able to determine the causes of general faults and eliminate them, such as skillfully replacing fuses, components, and damaged circuit boards. Untrained personnel are not allowed to operate the equipment.

4. If an accident occurs that is difficult to eliminate or the cause of the accident is unclear, detailed records of the accident should be kept and the inverter manufacturer should be notified in a timely manner for resolution.