Unbalance Load Compensation for a Three Phase Electrolytic Capacitor-Less Converter /Inverter

Abstract

Unbalance load compensation for an electrolytic capacitor-less converter/inverter of the flywheel long life uninterruptible power supply which rating of 3 phase, 200V and 5kW-1min is described. The compensation has following characteristics.
(1) Automatic output voltage balancer to cancel output voltage offset and output unbalance of 3 phase inverter.
(2) An input negative phase sequence current controller to compensate input current harmonic distortion at unbalanced loads.
(3) Automatic gain control on converter to improve input currents and transient states.
The UPS has excellence test results which are obtained such as total harmonic distortion THD of input current of 1.2% and 2.0% at 2.6kW single phase load and single rectifier load, respectively. Output voltage offset and unbalance are compensated by automatic output voltage balancer under 0.5s.