An Efficient UPF Rectifier for a Stand-AloneWind Energy Conversion System

ABSTRACT:

In this paper, a near-unity-power-factor front-end rectifier employing two current control methods, namely, average current control and hysteresis current control, is considered. This rectifier is interfaced with a fixed-pitch wind turbine driving a permanent-magnet synchronous generator. A traditional diode-bridge rectifier without any current control is used to compare the performance with the proposed converter. Two constant wind speed conditions and a varying wind speed profile are used to study the performance of this converter for a rated stand-alone load. The parameters under study are the input power factor and total harmonic distortion of the input currents to the converter. The wind turbine generator–power electronic converter is modeled in PSIM, and the simulation results verify the efficacy of the system in delivering satisfactory performance for the conditions discussed. The efficacy of the control techniques is validated with a 1.5-kW laboratory prototype, and the experimental results are presented.

 KEYWORDS:

  1. Average current control (ACC)
  2. Hysteresis current control (HCC)
  3. Permanent-magnet synchronous generator (PMSG)
  4. Unity-power-factor (UPF) converter

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, a WECS interfaced with a UPF converter feeding a stand-alone load has been investigated. The use of simple bidirectional switches in the three-phase converter results in near-UPF operation. Two current control methods, i.e., ACC and HCC, have been employed to perform active input line current shaping, and their performances have been compared for different wind speed conditions. The quality of the line currents at the input of the converter is good, and the harmonic distortions are within the prescribed limits according to the IEEE 519 standard for a stand-alone system. A high power factor is achieved at the input of the converter, and the voltage maintained at the dc bus link shows excellent voltage balance. The proposed method yields better performance compared to a traditional uncontrolled diode bridge rectifier system typically employed in wind systems as the front-end converter. Finally, a laboratory prototype of the UPF converter driving a stand-alone load has been developed, and the ACC and HCC current control methods have been tested for comparison. The HCC current control technique was found to be superior and  has better voltage balancing ability. It can thus be an excellent front-end converter in a WECS for stand-alone loads or grid connection.

REFERENCES:

[1] C. E. A. Silva, D. S. Oliveira, L. H. S. C. Barreto, and R. P. T. Bascope, “A novel three-phase rectifier with high power factor for wind energy conversion systems,” in Proc. COBEP, Bonito-Mato Grosso do Sul, Brazil, 2009, pp. 985–992.

[2] Online. Available: http://en.wikipedia.org/wiki/Wind_energy

[3] M. Druga, C. Nichita, G. Barakat, B. Dakyo, and E. Ceanga, “A peak power tracking wind system operating with a controlled load structure for stand-alone applications,” in Proc. 13th EPE, 2009, pp. 1–9.

[4] S. Kim, P. Enjeti, D. Rendusara, and I. J. Pitel, “A new method to improve THD and reduce harmonics generated by a three phase diode rectifier type utility interface,” in Conf. Rec. IEEE IAS Annu. Meeting, 1994, vol. 2, pp. 1071–1077.

[5] A. I. Maswood and L. Fangrui, “A novel unity power factor input stage for AC drive application,” IEEE Trans. Power Electron., vol. 20, no. 4, pp. 839–846, Jul. 2005.

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