PV inverter selection skills

- Nov 20, 2018-

The choice of inverter must first consider having sufficient rated capacity to meet the electrical power requirements of the equipment under the maximum load. For inverters that are loaded with a single device, the selection of the rated capacity is relatively simple.

When the electrical equipment is pure resistive load or the power factor is greater than 0.9, the rated capacity of the inverter is 1.1 to 1.15 times of the capacity of the electrical equipment. At the same time, the inverter should also have the ability to withstand capacitive and inductive load shocks.

For general inductive loads, such as motors, refrigerators, air conditioners, washing machines, high-power pumps, etc., the instantaneous power may be 5-6 times of its rated power when starting, at this time, the inverter will bear a large moment. surge. For such systems, the rated capacity of the inverter should be left with sufficient margin to ensure that the load can be reliably started. The high-performance inverter can be started multiple times at full load without damaging the power device. For the safety of small inverters, it is sometimes necessary to use soft start or current limit start.

Installation precautions and maintenance

  1. Before installation, you should first check whether the inverter is damaged during transportation.

  2. When selecting the installation site, it should be ensured that there is no interference from any other power electronic equipment in the surrounding area.

  3. Before making electrical connections, be sure to cover or disconnect the DC side circuit breakers with opaque materials. When exposed to sunlight, the PV array will generate dangerous voltages.

  4. All installation operations must be performed by professional technicians only.

  5. The cables used in the photovoltaic system power generation system must be firmly connected, with good insulation and appropriate specifications.

Development trend

For solar inverters, improving the conversion efficiency of the power supply is an eternal issue, but when the efficiency of the system is getting higher and higher, almost 100%, further efficiency improvement will be accompanied by low cost performance, therefore, how to maintain A high efficiency and maintaining good price competitiveness will be an important issue at present.

Compared with the improvement of inverter efficiency, how to improve the efficiency of the entire inverter system is becoming another important issue of the solar system. In a solar array, when a local 2~3% area shadow appears, for an inverter with an MPPT function, even when the system output power is bad, there will even be a power drop of about 20%! Better adapt to conditions like this For single or partial solar modules, a one-to-one MPPT or multiple MPPT control functions are a very effective method.

Because the inverter system is in grid-connected operation, the leakage of the system to the ground will cause serious safety problems; in addition, in order to improve the efficiency of the system, most of the solar arrays will be connected in series to a high DC output voltage; Due to the occurrence of abnormal conditions between the electrodes, it is easy to generate a DC arc. Since the DC voltage is high, it is very difficult to extinguish the arc, which is extremely likely to cause a fire. With the widespread adoption of solar inverter systems, system safety issues will also be an important part of inverter technology.

In addition, the power system is ushering in the rapid development and popularization of smart grid technology. A large number of solar energy and other new energy power systems are connected to the grid, which poses new technical challenges for the stability of the smart grid system. Designing an inverter system that can be more quickly, accurately and intelligently compatible with the smart grid will become a necessary condition for the future solar inverter system.

In general, the development of inverter technology has evolved with the development of power electronics, microelectronics and modern control theory. Over time, inverter technology is moving toward higher frequencies, higher power, higher efficiency, and smaller size.


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