From the photos you provided in the previous email, you can see that the frequency range of the two GSL1000 inverters is 45Hz~55Hz. If the grid frequency fluctuates within this range, the inverter will operate normally and will not cause the inverter power due to frequency fluctuations. If the grid frequency exceeds this range, the inverter will go off-grid and stop generating power. After the frequency falls within this range, the inverter will connect to the grid again for power generation. The frequency range of that GSM1250 inverter can also be modified to the range of 45Hz~55Hz on the display screen.