Control method during zero-crossing operation of bridge arms in UPS

摘要

A control method is disclosed that involves controlling zero-crossing operation of bridge arms in a UPS, wherein the UPS has a rectifying bridge with first and second switching transistors, a midline bridge arm with third and fourth switching transitors, and an inverter bridge arm with fifth and sixth switching transitors. The midline and rectifying bridge arms are controlled to cross zero synchronously. The inverter bridge arm is controlled to be disconnected during a period before a zero-crossing point of the rectifying bridge arm to a period after the zero-crossing point of the rectifying bridge arm. The periods before and after the zero-crossing point of the rectifying bridge arm are time differences between the zero-crossing points of the inverter bridge arm and the rectifying bridge arm. The influence of asynchronous zero-crossing between the PFC circuit and the inverter circuit on the UPS performance indices may be reduced by using the present control method.

主权项

1. A control method to control zero-crossing operation of bridge arms in an uninterruptible power supply (UPS), wherein the UPS has a rectifying bridge arm consisting of a first switching transistor (Q1) and a second switching transistor (Q2), a midline bridge arm consisting of a third switching transistor (Q3) and a fourth switching transistor (Q4), and an inverter bridge arm consisting of a fifth switching transistor (Q5) and a sixth switching transistor (Q6), the method comprising:
controlling the midline bridge arm and the rectifying bridge arm to cross zero synchronously; controlling both the fifth and sixth switching transistors of the inverter bridge arm to be continuously disconnected during a period beginning before a zero-crossing point of the rectifying bridge arm to a period after the zero-crossing point of the rectifying bridge arm has been passed; and wherein a first period length before the zero-crossing point and a second period length after the zero-crossing point are determined based on a time difference between a zero-crossing point of the inverter bridge arm and the zero-crossing point of the rectifying bridge arm.