The working principle of photovoltaic grid - connected inverter
Full-bridge inverter circuit to overcome the shortcomings of the push-pull circuit, the power transistor to adjust the output pulse width, the output AC voltage RMS that changes. Since the circuit has a freewheeling circuit, even if the inductive load, the output voltage waveform will not be distorted. The disadvantage of this circuit is that the upper and lower arms of the power transistor are not common, so you must use a special drive circuit or use isolated power supply. In addition, in order to prevent the upper and lower arm co-conduction, must be designed to turn off after the conduction circuit, that must be set dead time, the circuit structure is more complex.
In the small-capacity inverter generally push-pull inverter circuit, full-bridge inverter circuit and high-frequency step-up inverter circuit three, push-pull circuit, the step-up transformer neutral plug connected to the positive power supply, two power Alternating current, the output to get AC power, due to the power transistor to ground, drive and control circuit is simple, and because the transformer has a certain leakage inductance, can limit the short circuit current, thus improving the reliability of the circuit. The disadvantage is the low utilization of the transformer, driving the emotional load is poor.
Inverter will be converted into alternating current DC, if the DC voltage is low, then through the AC transformer boost, that is, the standard AC voltage and frequency. For large-capacity inverter, because the DC bus voltage is high, AC output generally does not require transformer boost that can reach 220V, in the small and medium capacity of the inverter, because the DC voltage is low, such as 12V, 24V, It is necessary to design a boost circuit.
