Why is the starting voltage of the inverter higher than the minimum voltage?
In photovoltaic inverters, there is a rather strange parameter, that is, the inverter input starting voltage. This voltage is approximately 30V higher than the minimum operating voltage. For example, in the single – phase hybrid inverter shown below, the MPPT operating voltage is from 125V to 425V, and the starting voltage is 150V. Many people are very puzzled. Between 125V and 150V, does the inverter work or not? If it works, but the inverter only starts at 150V. If it doesn’t start, how does the inverter work?
Actually, the reason why the starting voltage is higher than the minimum operating voltage is designed according to the characteristics of photovoltaic modules. Before the inverter starts, the modules are not working and are in an open – circuit state, and the voltage will be relatively high. When the inverter starts, the modules are in a working state and the voltage will decrease. In order to prevent the inverter from restarting repeatedly, the starting voltage of the inverter is higher than the minimum operating voltage.
For example, when three modules are connected in series, when there is sunlight in the morning, the open – circuit voltage may be 130V. If it starts at this time, it may only be 120V, which does not reach the operating voltage, and the inverter will shut down. Only when the open – circuit voltage exceeds 150V, if it starts at this time, the operating voltage will exceed 125V, and the inverter can work all the time.
After the inverter starts, it doesn’t mean that the inverter will have power output immediately. The control part of the inverter, such as the CPU and the screen, starts to work first. First, the inverter conducts self – inspection, and then detects the modules and the power grid. After there is no problem at all, the inverter will have output when the photovoltaic power exceeds the standby power of the inverter.