Adaptive shunt filtering control of UPQC for increased nonlinear loads

Abstract

In a distribution system, to compensate for the effect of voltage sag/swell and mitigate harmonic currents, a unified power quality conditioner (UPQC) is used. Conventionally, the power rating of UPQC is determined based on the expected sag/ swell, linear and nonlinear loads. However, with the shift towards usage of electronic loads and electrical drives, the composition of nonlinear loads is increasing. Hence, the UPQC deployed earlier may not be capable of handling increased harmonic currents due to its limited current rating. While trying to compensate for both harmonic currents and voltage sag/swell, the shunt converter (of UPQC) may reach its current limit and would result in undesirable behaviour. To address this issue, a technique to prioritise sag/swell compensation over active filtering is proposed in this study. The remaining power capacity of UPQC (after sag/swell compensation) is utilised for harmonic filtering. Adaptive determination of harmonic compensation current also allows prioritising the various harmonics to be compensated. This helps in case passive tuned filters are installed for some harmonic frequencies for which UPQC need not respond. Detailed simulation studies are performed on MATLAB/SIMULINK platform and results are included in this study. A laboratory prototype of single phase UPQC is developed to validate the performance of the proposed scheme.

Modeling and Simulation of a PI Controlled Shunt Active Power Filter for Power Quality Enhancement Based on P-Q Theory

“…The presence of nonlinear loads, such as personal computers, variable frequency drives (VFDs) and arc furnaces, gives rise to power quality problems, e.g., harmonic distortion, voltage fluctuation and noise [3][4][5]. Harmonic distortion in low-voltage distribution systems is responsible for power losses, electric devices heating, insulation failures, interference issues in communication systems and in the worst cases, electric power system failure [6,7]. Therefore, the need for the elimination of power quality problems has become an important issue for both the utility and the customer [8].…”

Transformer‐less single‐phase unified power quality conditioner of no circulating current

“…Generally, an active power filter (APF) is used to handle the current-related PQ problems, while dynamic voltage restorer (DVR) is preferred to tackle the voltage-related PQ problems [4,5]. Unified PQ conditioner (UPQC), as the integration of an APF and a DVR sharing a common dc-link [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], can deal with both current and voltage-type of PQ issues, simultaneously. Specifically, it can regulate load voltage, mitigate voltage transients, eliminate source current harmonics, and correct source power factor over a wide operating range.…”

Three‐phase four‐wire unified power quality conditioner structure with independent grid current control and reduced dc‐bus voltage operating with inverted/dual compensating strategy

“…For control purposes, conventional strategies of power‐line compensating usually use non‐sinusoidal voltage/current references to control both voltages and currents of the series and the parallel converters . In this paper, the dual/inverted compensating strategy is adopted to control the parallel converter for acting as a sinusoidal voltage source and the series converter for working as a sinusoidal current source .…”