Photovoltaic inverter selection tips


Release time:

2023-06-21

The function of the photovoltaic inverter is to convert the DC power generated by the solar cells into AC power that meets the power quality requirements of the grid. It consists of electronic components (IGBT, capacitors, resistors, reactors, PCB, etc.), structural parts (cabinets, chassis, etc.) and auxiliary materials.

The function of the photovoltaic inverter is to convert the DC power generated by the solar cells into AC power that meets the power quality requirements of the grid. It consists of electronic components (IGBT, capacitors, resistors, reactors, PCB, etc.), structural parts (cabinets, chassis, etc.) and auxiliary materials. According to specific functions, it can be divided into: string photovoltaic inverter, centralized Photovoltaic inverters, distributed photovoltaic inverters, micro photovoltaic inverters. Photovoltaic inverters are the core of the photovoltaic power generation industry and are positively related to the development of the photovoltaic industry.

The booming photovoltaic industry has driven the growth of demand for photovoltaic inverters. However, photovoltaic inverters are a large category with various specifications and models, and their selection is also a complex knowledge. Today we will introduce photovoltaic inverters and their selection tips.

Classification of photovoltaic inverters:

According to the output waveform, operation mode, output AC phase number, and power flow direction, it is divided as follows:

Output waveform: square wave inverter, ladder wave inverter, sine wave inverter;

Operation mode: off-grid inverter, grid-connected inverter;

Number of output alternating current phases: single-phase inverter, three-phase inverter;

Power flow direction: one-way inverter, two-way inverter.

Photovoltaic inverter selection tips

The basic circuit structure of the inverter is shown in the figure, which mainly consists of input circuit, output circuit, main inverter switch circuit (main inverter circuit), control circuit, auxiliary circuit and protection circuit.

The factors that determine the selection of photovoltaic transformers include technical parameters such as output voltage, load power factor, rated output current, rated output capacity, rated output efficiency, and overload capacity. In addition, there are other requirements such as operating environment conditions, electromagnetic interference and noise requirements, safety performance requirements for protective measures, etc. Specifically, you can refer to the following points:

1. Rated output capacity:

It represents the inverter's ability to supply power to the load. First consideration should be given to having sufficient rated capacity to meet the electrical power requirements of the equipment under maximum load, as well as system expansion and the connection of some temporary loads.

2. Output voltage adjustment performance

The adjustment performance of the output voltage indicates the ability of the inverter to stabilize the output voltage. Generally, the inverter gives voltage regulation rate and load regulation rate.

Voltage regulation rate: The deviation (%) of the inverter's output voltage within the allowable fluctuation range of the inverter's input DC voltage should be ≤3%;

Load regulation rate: A high-performance inverter should also provide the deviation (%) of the inverter's output voltage when the load changes from 0 to 100%, which should be ≤ 6%.

Off-grid photovoltaic power generation systems use batteries as energy storage equipment, and the battery terminal voltage can vary up to about 30% of the nominal voltage. Therefore, in order to ensure that the photovoltaic power generation system supplies power with a stable AC voltage, the inverter must have good voltage regulation performance.

3. Overall machine efficiency

The overall efficiency indicates the power loss of the inverter itself. Inverters with larger capacity also provide efficiency values under full load operation and low load operation. Generally, the efficiency of inverters below kW level should be 80% to 85%; the efficiency of 10kW level inverters should be 85% to 90%; the efficiency of larger power inverters must be above 90% to 95%.

In the design of special inverters for photovoltaic power generation systems, special attention should be paid to reducing its own power loss and improving the efficiency of the entire machine. This is because the actual efficiency of a 10kW-class general-purpose inverter is only 70% to 80%. When used in a photovoltaic power generation system, it will cause an energy loss of 20% to 30% of the total power generation. Therefore, when the household system is not using power, the inverter should be turned off to reduce losses when power is not used.

4. Protection function

The inverter should have over-voltage, over-current and short-circuit automatic protection, over-heat protection function, circuit breakage, phase loss protection and other functions.

5. Startup performance

The inverter should start reliably under rated load. A high-performance inverter can be started at full load multiple times without damaging the power switching devices and other circuits. For their own safety, small inverters sometimes use soft start or current limiting starting measures or circuits.

Summarize

The above are the selection tips for photovoltaic inverter transformers. The quality of photovoltaic inverter transformers is related to the power production work. It is recommended to choose a regular, reliable and powerful supplier to ensure the stability of its product quality.

We at Leilang Electric were established in 2007. We have been deeply involved in the field of electrical equipment for many years and have rich experience in design, production and manufacturing. The workshop covers an area of 3,000 square meters, has more than 60 large and small production equipment, and has an annual output of more than 100,000 units/set of finished products. It has a certain scale and strength. We selected high-quality raw materials (H-class insulating paint and H-class enameled wire, new oriented/non-oriented silicon steel sheets, high-quality auxiliary parts) as transformer materials, and used advanced automated production equipment and segmented paint dipping processes in strict accordance with ISO9001 : 2015 quality management system for production. The product quality is stable and reliable. It has passed CE certification and third-party quality inspection. New and old customers are welcome to come for consultation!

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