700 Watt Solar Micro Inverter, Grid-tie Inverter

700W Micro Inverter User Manual

What is maximum power point (MPP) of solar inverter?

Solar cell can work in a wide range of voltages and currents. By the resistive load on the battery from zero (short circuit) continues increase to high value (open circuit) to determine MPP. MPP is operation point of the maximum value of V x I (voltage multiply current), and reach maximum power in the sun light intensity. The output power is zero in short-circuit (PV voltage equal to zero) or open circuit (PV current is equal to zero).

High quality single crystal silicon solar cells can generate 0.6 volts open circuit voltage in the temperature 25 °C. In full light and air temperature is 25 °C, the temperature of solar cell may be close to 45 °C, which makes the open circuit voltage drops to about 0.55V. With the increases of temperature, the open circuit voltage continuous declines until the PV module short circuit.

The maximum power of the solar cell in temperature of 45 °C usually is usually produced under the conditions of 80% open circuit voltage and 90% short circuit current. The solar cell short-circuit current is almost proportional to the intensity of illumination, while the open circuit voltage may only drop 10% when the illuminate intensity decreases 80%. Lower quality solar cells' voltage will drop faster in the case of the current increase, thereby decrease the output power from 70% to 50 % or even 25%.