New Control Scheme for a Unified Power-Quality Compensator-Q With Minimum Active Power Injection

Voltage sags are one of the most frequently occurring power-quality problems challenging power systems today. The unified power-quality conditioner (UPQCs) is one of the major custom power solutions capable of mitigating the effect of supply voltage sags at the point of common coupling (PCC) or load. A UPQC-Q employs a control method in which the series compensator injects a voltage that leads the supply current by 90° so that the series compensator at steady state consumes no active power. However, the UPQC-Q has some disadvantages. First, there are limitations in rating when using UPQC-Q for series compensation. Second, there is a phase difference between the input and output voltage in proportion to the severity of voltage sags. As a result, it cannot offer effective compensation for voltage drops. This paper proposes a new control scheme for the UPQC-Q that offers minimum active power injection. The proposed power injection method takes into consideration the limitations of the rated voltage capacity of the series compensator, and the phase difference during voltage sag events. The validity of the proposed control scheme has been investigated by simulation and experimental results for less than 50% voltage sag conditions.

[1]  S. Muthu,et al.  Steady-state operating characteristics of unified active power filters , 1997, Proceedings of APEC 97 - Applied Power Electronics Conference.

[2]  A. Ghosh,et al.  Design of a capacitor-supported dynamic voltage restorer (DVR) for unbalanced and distorted loads , 2004, IEEE Transactions on Power Delivery.

[3]  Subhashish Bhattacharya,et al.  Active filter system implementation , 1998 .

[4]  Y.Y. Kolhatkar,et al.  Experimental Investigation of a Single-Phase UPQC With Minimum VA Loading , 2007, IEEE Transactions on Power Delivery.

[5]  Dong-Seok Hyun,et al.  A three-phase parallel active power filter operating with PCC voltage compensation with consideration for an unbalanced load , 2002 .

[6]  San Shing Choi,et al.  Dynamic voltage restoration with minimum energy injection , 2000, 2000 IEEE Power Engineering Society Winter Meeting. Conference Proceedings (Cat. No.00CH37077).

[7]  Dong-Seok Hyun,et al.  New control scheme of three-phase PWM AC/DC converter without phase angle detection under the unbalanced input voltage conditions , 2002 .

[8]  Luis Morán,et al.  Control system for three-phase active power filter which simultaneously compensates power factor and unbalanced loads , 1995, IEEE Trans. Ind. Electron..

[9]  Hirofumi Akagi,et al.  The unified power quality conditioner: the integration of series- and shunt-active filters , 1998 .

[10]  Dong-Seok Hyun,et al.  The control system of the active power filter considering power factor in unbalanced load , 2000, Conference Record of the 2000 IEEE Industry Applications Conference. Thirty-Fifth IAS Annual Meeting and World Conference on Industrial Applications of Electrical Energy (Cat. No.00CH37129).

[11]  S. S. Choi,et al.  A new control strategy for energy-saving dynamic voltage restoration , 2000, 2000 Power Engineering Society Summer Meeting (Cat. No.00CH37134).

[12]  Seung-Gi Jeong.  Representing line voltage unbalance , 2002, Conference Record of the 2002 IEEE Industry Applications Conference. 37th IAS Annual Meeting (Cat. No.02CH37344).

[13]  J. Allmeling,et al.  A control structure for fast harmonics compensation in active filters , 2004, IEEE Transactions on Power Electronics.

[14]  P. Rioual,et al.  Regulation of a PWM rectifier in the unbalanced network state using a generalized model , 1996 .

[15]  B. Han,et al.  New configuration of UPQC for medium-voltage application , 2006, IEEE Transactions on Power Delivery.

[16]  G. D. Marques,et al.  An active power filter and unbalanced current compensator , 1997, IEEE Trans. Ind. Electron..

[17]  Geza Joos,et al.  Analysis and design of a series voltage compensator for three-phase unbalanced sources , 1992, IEEE Trans. Ind. Electron..

[18]  Kamal Al-Haddad,et al.  A review of active filters for power quality improvement , 1999, IEEE Trans. Ind. Electron..

[19]  Hirofumi Akagi,et al.  New trends in active filters for power conditioning , 1996 .

[20]  Valentin Navrapescu,et al.  Single-Phase Unified Power Quality Conditioner with Optimum Voltage Angle Injection for Minimum VA requirement , 2007, 2007 IEEE International Symposium on Industrial Electronics.