This whitepaper deals with the Sungrow SH5.0-10RT and SH15-25T hybrids.
The string configuration for the Sungrow SHxxRT & SHxxT hybrids is crucial for the optimal operation of your PV power plant. To achieve maximum efficiency, the string voltage should be close to the inverter's nominal voltage of 600 Vmpp. Attention should also be paid to the string length during planning. As a general rule, the strings should ideally be equal in length.
Long strings and a high DC/AC ratio are incompatible, as this combination can lead to voltages exceeding the MPP rated power range, power losses, and reduced efficiency.
If the strings are too short, this can result in the system either not switching on, switching on only after a delay, or potentially switching off again during midday in summer. This is partly due to the electrical properties of the solar modules, which means, for example, that the PV module voltage decreases at high temperatures.
At the inverter level, it should be noted that the current on MPPT 2 is slightly lower or that it starts production later, as the hybrid inverter deducts its self-consumption. For smooth operation, note that the light blue boundary zones (see Figs. 1 and 2) should not be included in planning, as to do so could reduce inverter performance. For the string configuration, values within the orange MPP voltage range should be selected (see Fig. 1 and Fig. 2). These values can also be found in the appendix of the relevant product manual.
When selecting modules, it is particularly important to pay attention to the short-circuit currents. Here, in conjunction with the inverter, a 15% reserve should be allowed between the short-circuit current indicated in the panel datasheet STC and the inverter PV input short-circuit current in order to take into account roof tilt, temperature coefficient, white cloud reflection, panel positive sorting, and flasher tolerance within the overall system. The Impp is another important aspect: If the module's Impp exceeds the inverter's Impp, the inverter will reduce the current to match its own Impp – a phenomenon known as clipping. Here, the string voltage is increased so that less power is typically lost than initially appears to be the case when analyzing the current curve.
When operating with a battery, note that string voltages above 700 Vmpp reduce the maximum charging capacity, and from 800 Vmpp, it can drop to around 2 kW. The maximum PV voltage for battery charging is 900 Vdc. In this case, the discharge capacity remains unaffected.
SH5.0-10RT:
In relation to the Sungrow SH5.0-10RT hybrid series, we recommend a maximum difference of seven panels between the MPPTs. Nonetheless, even in this case, it is advisable to form strings of equal length where possible.
With regard to the 15% reserve between the panel datasheet Isc and the inverter Isc, we arrive at the following values:
SH5.0-10RT V11/V112 | SH5.0-10RT-20 |
Max. panel datasheet Isc = 13.9 A | Max. panel datasheet Isc = 15.7 A |
Inverter Impp = 12.5 A | Inverter Impp = 13.5 A |
Fig. 1
SH15-25T:
In relation to the Sungrow SH15-25T hybrid series, we recommend a maximum difference of four panels between the MPPTs. Nonetheless, even in this case, it is advisable to form strings of equal length where possible.
SH15-25T |
Max. panel datasheet Isc = 17.4 A |
Inverter Impp = 16 A |
In this hybrid series, an AFCI error message may be output if the voltage is outside the upper or lower MPP nominal voltage limits, or if the 700 Vdc battery limit is surpassed, depending on the firmware.
Fig. 2
For more information, please refer to the user manuals and the installer training courses on the hybrids of the SHxxRT(-20) and SHxxT series.
This manual is intended for qualified personnel trained to install and commission the inverter, as well as for the owners of the inverters who may interact with them. Always read the manual and all associated documents before handling or operating the inverter. The documents must be stored carefully and kept readily accessible at all times. Their contents may be regularly updated or revised as the result of product development. The information in this manual may be changed at any time without prior notice. The latest manual can be obtained from http://ger.sungrow-emea.com.