At present, the power inverter mainly adopts PWM, and the controller switches to DC quickly within a pulse cycle to ensure that the integral value of DC is equal to the sampling value of AC sine wave. After filtering, more than 96% of sine wave output can be achieved. Pulse inverter is self - excited inverter, the output voltage is pulse modulation. This kind of power inverter can reduce the number of voltage and current pulses by increasing the number of switching cycle pulses, and only need to increase the frequency of inverter commutation.
The inductance of AC power inverter determines the content of current harmonics. Therefore, in order to meet grid-connection requirements, the equivalent inductance of the photovoltaic power generation system should be small. The power inverter is connected to a low pass filter and an isolation transformer. It can filter out the harmonics below n-1, where N is the current period of the triggering pulse stream. In order to increase the switching frequency, the power loss of the electronic equipment will increase, but the loss of the low-pass filter with the low switching frequency will increase. If the current clock frequency multiplier of the single-phase AC grid is combined, the frequency of the AC control signal modulated by the DC output of the photovoltaic generator will be doubled.
