A Control Strategy for Unified Power Quality Conditioner

ABSTRACT:

 This paper presents a control strategy for a Unified Power Quality Conditioner. This control strategy is used in three-phase three-wire systems. The UPQC device combines a shunt-active tilter together with a series-active filter in a hack to- back configuration, to simultaneously compensate the supply voltage and the load current. Previous works presented a control strategy for shunt-active filter that guarantees sinusoidal, balanced and minimized source currents even if under unbalanced and / or distorted system voltages, also known as “Sinusoidal Fryze Currents”. Then, this control strategy was extended to develop a dual control strategy for series-active filter. Now, this paper develops the integration principles of shunt current compensation and series voltages compensation, both based on instantaneous active and non-active powers, directly calculated from a-b-c phase voltages and line currents. Simulation results are presented to validate the proposed UPQC control strategy.

KEYWORDS:

1.      Active Filters

2.      Active Power Line Conditioners

3.      Instantaneous Active and Reactive Power

4.      Sinusoidal Fryze Currents

5.      Sinusoidal Fryze Voltages

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 . General configuration of the Unified Power Quality Conditioner - UPQC.

 EXPECTED SIMULATION RESULTS:

Fig. 2: Load current. current of the shunt active filter and source current.

Fig 3 Supply voltage. compensating voltage and the compensated voltage delivered to the critical load

Fig. 4. DC link voltage signal v_DC and DC voltage regulator signal G_loss

Fig. 5. Source currents, compensated voltages  and the compensated

voltage V_aw together with the source current l

CONCLUSION:

A control strategy for Unified Power Quality Conditioner - the UPQC - is proposed. Simulation results have validated the proposed control strategy, for the use in three-phase three-wire systems. In case of using in three phase four-wire systems, there is the necessity of compensating the neutral current. In this case, three-phase four wire PWM converter is necessary.

The computational efforts to develop the proposed control strategy is reduced, if compared with pq-Theory based controllers, since the α-β-0 transformation is avoided. For three-phase three-wire systems, the performance of the proposed approach is comparable with those based on the pq Theory, without loss of robustness even if operating under distorted and unbalanced system voltage conditions.

Presently, the authors are working on the possibility of extending the proposed control strategy for the use in three phase four-wire systems.

REFERENCES:

[1] S. Fryze. "Wirk-. Blind- und Scheinleistung in elektrischen Stromkainsen mit nicht-sinusfomigen Verlauf von Strom und Spannung." ETZ-Arch. Elektrotech.. vol. 53. 1932, pp. 596-599. 625-627. 700-702.

[2] L. Malesani. L. Rosseto. P. Tenti. "Active Filter for Reactive Power and Harmonics Compensation", IEEE - PESC 1986. pp. 321-330.

[3] Luis F.C. Monteiro, M. Aredes. "A Comparative Analysis among Different Control Strategies for Shunt Active Filters." Proc. (CDROM) of the V INDUSCON - Conferencia de Aplicacoes In dustriais. Salvador. Brazil, July 2002. pp.345-350.

[4] T. Furuhashi, S . Okuma. Y. Uchikawa, "A Study on the Theory of Instantaneous Reactive Power," IEEE Trans. on Industrial Electronics. vol. 37. no. 1. pp. 86-90. Feb. 1990.

[5] L. Rossetto, P. Tenti. "Evaluation of Instantaneous Power Terms in Multi-Phase Systems: Techniques and Application to Power- Conditioning Equipments." ETEP - Eur.. Trans.elect. Po wer Eng . vol. 4. no. 6. pp. 469-475, Nov./Dec. 1994.