1. Principle of full-control inverter: It is a single-phase output full-bridge inverter main circuit normally used. The AC components are IGBTs Q11, Q12, Q13, and Q14. The PWM pulse width modulation controls the conduction of the IGBT. Pass or stop.
When the inverter circuit is connected to the DC power supply, it is turned on by Q11, Q14, and Q1, Q13 are turned off. Then the current is output from the positive side of the DC power supply. After the Q11, L sense, the primary winding of the transformer is shown in Figure 1-2. When the Q11 and Q14 are turned off, Q12 and Q13 turn on, the current flows from the positive terminal of the power supply through Q13, the inductor of the primary winding of the transformer 2-1 returns to the negative terminal of the power supply of Q12. At this time, the primary winding of the transformer is positively formed. Negative alternating square wave, using high-frequency PWM control, the two pairs of IGBT tubes alternately repeat and generate AC voltage on the transformer. Because of the role of LC AC filter, the output terminal forms a sine wave AC voltage.
When Q11, Q14 turn off, in order to release the stored energy, the diodes D11, D12 are connected in parallel at the IGBT to return the energy to the DC power supply.
2. Working principle of semi-controlled inverter: Semi-controlled inverter uses thyristor components. Th1, Th2 are thyristors that work alternately. Let Th1 trigger to conduct first, then current flows through transformer through Th1, and at the same time, due to the induction of transformer. As a result, the commutating capacitor C is charged to 2 times the mains voltage. It is triggered when Th2 is turned on. Since the anode of Th2 is reverse-biased, Th1 is turned off and returns to the blocking state. Thus, Th1 and Th2 commutation are performed. The capacitor C is then reversed in polarity. This alternately triggers the thyristor. The current flows alternately to the primary of the transformer, and the alternating current is obtained in the secondary of the transformer.
In the circuit, the inductor L can limit the discharge current of the commutation capacitor C, prolong the discharge time, ensure that the circuit turn-off time is longer than the turn-off time of the thyristor, and does not need a large capacity capacitor. D1 and D2 are two feedback diodes, The energy in the inductor L can be released and the remaining energy in the commutation can be sent back to the power supply to complete the energy feedback.
