In the event of adequately large smoothing reactance inductance in the DC side, the output voltage of the three-phase full-bridge rectification circuit is as follows:
Ud＝1.35 Ua cosα (1)
Ud --------average value of output DC voltage
Ua --------input line voltage of rectifier bridge
α---------trigger delay angle of SCR
If the rectifier bridge input line voltage Ua is given, the size of the output DC voltage can be changed by change of the trigger delay angle of the tube so as to achieve the purpose of regulating the output power of the equipment. Because of the cosine(non-linear) relationship between Ua and a, the non-linear link is added in the microcomputer control triggering procedure, which plays a key role in the improvement of linearization regulation. In the event of a failure, the pulse a> 90 degrees is subject to push inverter protection. It can be seen from the formula (1) that the Ud is negative. In this case, it is called the inverter operating status ofrectifier bridge. The essence is the feedback of energy to the power grid by load, which doesn't cause damage to inverter devices.
