Detailed Explanation Of Photovoltaic Grid-Connected Inverter Parameters

Let's take Sungrow's SG30T-CN Inverter As An Example.

For example: SG30T-CN inverter

SG: represents the Sunshine inverter product line;

T:Three represents three-phase inverter

30: represents the inverter output power of 30kW;

CN: represents the Chinese version.

This refers to the maximum voltage allowed to be input to the inverter, that is, the sum of the open-circuit voltages of all panels in a single string cannot exceed this value.

For example, for Sungrow's SG30T-CN inverter, considering the negative temperature characteristics of the open-circuit voltage of the components in cold weather (the open-circuit voltage increases as the temperature decreases), the open-circuit voltage of a single string cannot exceed the maximum input voltage of the inverter, 1100V.

A wider MPPT voltage range can achieve earlier power generation in the morning and more power generation after sunset. When the MPPT voltage of the string reaches the inverter MPPT voltage range (such as the voltage range of Sungrow's SG30T-CN is 160V-1000V), the inverter can track the maximum power point of the string.

Note: The optimal operating voltage of the three-phase inverter is around 620V, at which time the inverter has the highest conversion efficiency. In actual applications, when the string operating voltage is lower than the rated voltage (620V), the inverter boost circuit starts to work, which will produce certain losses and reduce efficiency. Therefore, it is recommended that the MPPT voltage of each string of components is slightly higher than 620V when configuring the string.

4. The number of MPPT paths and the number of strings per MPPT input refers to the number of MPPT paths of the inverter and the number of strings that can be connected to each MPPT.

Take the following figure as an example:

There are 6 DC inputs, namely A, B, C, D, E, and F. PV1 and PV2 represent two MPPT inputs. The string inputs under one MPPT must be equal, and the string inputs under different MPPTs can be unequal, that is, A=B=CD=E=F, but A can be unequal to D.

The maximum current allowed to pass through the inverter, maximum DC input current = maximum input current of a single string x number of strings.

Inverter AC Output Side Technical Parameters

It refers to the output power of the inverter at rated voltage and current, which is the power that can be output stably for a long time.

The maximum power is also called peak power, which refers to the maximum power value that the inverter can output in a very short time. Since the maximum power can only be maintained for a very short time, it does not have much reference significance.

In an AC circuit, the cosine of the phase difference (Ф) between voltage and current is called the power factor, which is represented by the symbol cosФ. In terms of numerical value, the power factor is the ratio of active power to apparent power, that is, cosФ=P/S. Generally speaking, the power factor of resistive loads such as incandescent bulbs and resistance furnaces is 1, and the power factor of circuits with inductive loads is generally less than 1. When the power factor of the equipment is less than 0.9, a fine will be imposed. The power factor output of the Sungrow inverter is 1, and can be adjusted between 0.8 leading and 0.8 lagging.

Power factor is an issue that requires special attention in industrial and commercial distributed photovoltaic projects. It needs to be considered from a system perspective. Not only the type and size of the load must be considered, but also the performance, test points and control methods of the reactive compensation device. It is recommended to observe the operation of the entire photovoltaic system to ensure that the system active power is normal.

The inverter is a device in a photovoltaic power station that converts the DC power generated by the components into AC power.

In the process of converting DC power into AC power, a small amount of energy is lost in the form of heat, so the energy on the AC output side of the photovoltaic inverter is less than the energy on the DC input side. The ratio of the output power of the photovoltaic inverter at the AC end to the input power at the DC end is called the conversion efficiency of the inverter.

Photovoltaic inverters with small size, light weight and simple installation method have always been favored by customers. Small size and light weight often mean convenient transportation, reducing the risk of machine damage during transportation. The wall-mounted installation method is the first choice of customers. Customers only need to check whether the wall or installation attachment point is stable and reliable, reducing the manpower and material resources of installation.

The operating temperature range is also a technical parameter that everyone needs to pay attention to. The operating temperature range of the inverter often reflects the inverter's ability to withstand low and high temperatures and determines the life of the inverter. If the inverter has a wider ambient temperature range, it means that the inverter has a better ability to withstand low and high temperatures and has better performance.

Generally speaking, photovoltaic inverters are divided into indoor and outdoor use. Those with a relatively low protection level, generally IP20 or IP23, are for indoor use and require a dedicated inverter room. IP54 and IP65 both meet the standards for outdoor use and do not require an inverter room.

Note: You can safely install an inverter with an IP65 protection level outdoors, but you must add a cover to the inverter, or install it under the eaves, or install it on a bracket (under the component), etc., to ensure that it avoids direct sunlight, reduces the impact of various adverse factors, and guarantees the investment return of the photovoltaic system throughout its life cycle.

Many inverter manufacturers have different opinions on the cooling method. Some manufacturers think that fans are not needed at all, while others think that all inverters should be equipped with fans.

Both of these statements have their own reasons. The fan is a consumable part. If used for a long time, it will be easily damaged, which will reduce the stability of the inverter and increase the operation and maintenance costs.

On the other hand, if the fan is not installed, the heat dissipation of the inverter will be affected, especially when the external ambient temperature is very high. The inverter cannot dissipate heat in time, which will affect its life. Of course, under certain conditions, we need to consider how to avoid the impact of wind and sand on equipment with fans.