3-WIRE TRANSFORMER-FREE UPS SYSTEM AND METHOD OF CONTROL TO REDUCE COMMON MODE CURRENT

摘要

A common mode choke in a 3-wire transformer free UPS system with which different rectifier and bypass power sources are used is eliminated by using different types of PWM control depending on whether the inverter is paralleled with the bypass power source. When the inverter is paralleled with the bypass power source, a type of PWM control is used that does not have common mode voltage injection. When the inverter is not paralleled with the bypass power source, a type of PWM control is used that has common mode voltage injection. In an aspect, the PWM control that does not have common mode voltage injection is sine-triangle PWM and the PWM control that has common mode voltage injection is space-vector PWM.

主权项

1. A method of controlling a double-conversion three-wire transformer free uninterruptible power supply system having a rectifier and a bypass switch, the rectifier coupled to a rectifier bypass source and the bypass switch coupled to a bypass power source wherein the rectifier power source and the bypass power sources are different power sources, the uninterruptible power supply system including an inverter and a control module, comprising:
controlling the inverter with the control module with a pulse width modulation control that does not have common mode injection when the inverter is paralleled with the bypass power source and with a pulse width modulation control that has common mode injection when the inverter is not paralleled with the bypass power source.