Unified Power Quality Conditioner (UPQC)

Power System

Unified Power Quality Conditioner (UPQC)

Unified power quality conditioners (UPQC) allow the mitigation of voltage and current disturbances that could affect sensitive electrical loads while compensating the load reactive power. Unified power quality conditioners UPQC consist of combined series and shunt active power filters for simultaneous compensation of voltage and current disturbances and reactive power. The basic structure of this equipment is shown in Figure.

Figure-1: Unified Power Quality Conditioner (UPQC)

Unified Power Quality Conditioner (UPQC) for non-linear and a voltage sensitive load has following facilities:
  • It reduces the harmonics in the supply current, so that it can improves utility current quality for nonlinear loads.
  • UPQC provides the VAR requirement of the load, so that the supply voltage and current are always in phase, therefore, no additional power factor correction equipment is required.
  • UPQC maintains load end voltage at the rated value even in the presence of supply voltage sag.
  • The voltage injected by UPQC to maintain the load end voltage at the desired value which is taken from the same dc link, thus no additional dc link voltage support is required for the series compensator.
The UPQC is expected to be one of the most powerful solutions to large capacity loads sensitive to supply voltage and load current disturbances or unbalance condition. The most effective type of these devices is considered to be the Unified Power Quality Conditioner (UPQC). There are numerous reasons why the UPQC is preferred over the others. UPQC is much flexible than any single inverter based device [15]. It can simultaneously correct for the unbalance and distortion in the source voltage and load current where as all other devices either correct current or voltage distortion. Therefore the purpose of two devices is served by UPQC only. Based on these reasons, the UPQC is widely considered as an effective custom power device in mitigating voltage sags and swells. In addition to voltage sags and swell compensation, UPQC can also add other features such as harmonics and power factor correction.


Rajeev Kumar is dedicated to teaching and research in the field of electrical and electronics engineering. He is always sharing valuable content of the engineering field on this website.

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