Unified Power Quality Conditioner (UPQC) Based on Two Three-leg Convertes with Standby Operation Mode and Improved Voltage Swell Compensation

This paper proposes a single-phase unified power quality conditioner (UPQC) based on two three-leg AC-DC-AC converters. The converter A (main converter) is responsible for the operation under grid voltage sag and nominal conditions. In these scenarios, the converter B (auxiliary converter) remains in standby mode. When a voltage swell ocurrs the converter B starts operating in conjunction with converter A. For any operating scenarios of the grid voltage, the proposed system provides a high power factor on the grid side, keeping the load supplied with a compensated sinusoidal voltage. The system model and the system control, including the PWM techniques and the strategy to regulate dc-link voltage of converter B, whether during standby mode or in grid voltage swell scenarios, is presented. Additionally, simulations and experimental results are presented to demonstrate the viability of the proposed 6L-UPQC.