An Improved Modulated Carrier Control with On-Time Doubler for Single-Phase Shunt Active Power Filter

ABSTRACT

This paper proposes an improved modulated carrier control with on-time doubler for the single-phase shunt active power filter, which eliminates harmonic and reactive currents drawn by nonlinear loads. This control method directly shapes the line current to be sinusoidal and in phase with the grid voltage by generating a modulated carrier signal with a resettable integrator, comparing the carrier signal to the average line current and making duty ratio doubled. Since the line current compared to the carrier signal is not the peak, but the average value, dc-offset appeared at the conventional control methods based on one-cycle control is effectively addressed. The proposed control technique extirpates the harmonic and reactive currents and solves the dc-offset problem. The operation principle and stability characteristic of the single-phase shunt active power filter with the proposed control method are discussed, and experimental results with laboratory prototype under various load conditions verify its performance.

 

KEYWORDS

  1. Single-phase shunt active power filter
  2. Modulated carrier control
  3. Indirect control
  4. One-cycle control
  5. Harmonic and reactive currents elimination
  6. Nonlinear load.

 SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM

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Fig. 1. Single-phase shunt active power filter with nonlinear load.

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Fig. 2. Overall control structure of the proposed control method with the shunt APF.

 

EXPECTED SIMULATION RESULTS

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Fig. 3. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system based on the proposed control method at full load condition (vin : 200 V/div, iin : 20 A/div, if : 20 A/div, i- L : 20 A/div).

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Fig. 4. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system based on the proposed control method at half load condition (vin : 200 V/div, iin : 20 A/div, if : 20 A/div, iL : 20 A/div).

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Fig. 5. Current controller switching mechanism.

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Fig. 6. Measured dc-link voltage, line current, APF current and load current waveforms of the shunt APF system in load transient from 800 W to 1600 W (vo : 100 V/div, iin : 20 A/div, if : 20 A/div, iL : 20 A/div).

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Fig. 7. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system at 110 Vrms grid voltage. (vin : 100 V/div, iin : 10 A/div, if : 10 A/div, iL : 10 A/div) Under (a) 200 W, (b) 270 W, (c) 340 W, (d) 400 W load condition

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Fig. 8. Power factors of the nonlinear load system with and without the APF under various load conditions.

CONCLUSION

An improved modulated carrier control for single-phase active power filter has been proposed. The shunt APF with the proposed control method fulfills harmonic and reactive current elimination at the line current by comparing the carrier signal to the average line current and having the duty ratio doubled. On top of that, the control method totally gets rid of the dc-offset problem arisen at the conventional one based on one-cycle control and ameliorates the current control loop stability without additional ramp signal. The operation principle of power stage, the main control mechanism, and the stability characteristic of the current control loop are analyzed in detail. Experimental results with the shunt APF system under assorted conditions verify the performance of the proposed control method in steady and transient states.

 REFERENCES

  1. Elham B. Makram, E.V. Subramaniam, Adly A. Girgis, and Ray Catoe, “Hamonic filter design using actual recorded data,” IEEE Transaction on Industrial Application, vol. 29, no. 6, pp. 1176-1183, Nov. 1993.
  2. Z. Peng, “Harmonic sources and filtering approaches,” IEEE Transaction on Industrial Application Magazine, vol. 7, no. 4, pp. 18-25, Jul. /Aug. 2001.
  3. Czarnecki, L. S., Ginn, H. L., “The effect of the design method on efficiency of resonant harmonic filters,” IEEE Transactions on Power Delivery, vol. 20, no. 1, pp. 286-291, Jan. 2005.
  4. Fakhralden A. Huliehel, Fred C. Lee, and Bo H. Cho, “Small-signal modeling of the single-phase boost high power factor converter with constant frequency control,” PESC’92 Record. 23rd annual IEEE Power electronics Specialists Conference, 1992, vol.1, pp. 475 – 482.
  5. Martinez, P. N. Enjeti, “A high-performance single-phase rectifier with input power factor correction,” IEEE Transactions on Power Electronics, vol. 11, no. 2, pp. 311–317, Mar. 1996.

Analysis of Active Islanding Methods for Single phase Inverters

ABSTRACT:

This paper presents the analysis and comparison of the main active techniques for islanding detection used in grid-connected single phase inverters. These techniques can be divided into two classes: techniques introducing positive feedback in the control of the inverter and techniques based on harmonic injection by the inverter. The algorithms mentioned in this work are simulated in PSIMTM in order to make a comparative analysis and to establish their advantages and disadvantages according to IEEE standards.

 KEYWORDS:

Single phase inverter

Active Islanding Detection Methods

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

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 Fig.1. Block diagram of the developed inverter

EXPECTED SIMULATION RESULTS:

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Fig. 2. (a) Active power injection. PCC voltage, RMS Voltage and islanding detection. (b) Reactive power injection. PCC voltage, frequency and islanding detection.

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Fig. 3. GEFS. PCC voltage, frequency and islanding detection.

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Fig. 4. Impedance detection. PCC voltage and islanding detection.

CONCLUSION:

In this paper was presented an analysis of various active methods resident in the inverter for islanding detection in single phase inverters. It became evident that for the same test conditions as established by the IEEE 929 all methods met, however the positive feedback based methods have a longer trip time that those based on harmonic injection because positive feedback methods should reach the threshold of UOV or UOF, whereas methods based on harmonic injection what is sought is to detect variations in the impedance of the grid, which allows to work with smaller detection thresholds. On the other hand, despite these methods are based on disturbing the system and degrading the power quality, their effect is not significant and they are within the harmonic distortion limits set by standards.

REFERENCES:

[1] M, Pietzsch, “Convertidores CC/CA para la conexión directa a red de sistemas fotovoltaicos: comparación entre topologías de 2 y 3 niveles,” Bachelor thesis, Universidad Politécnica de Cataluña, España, Dec. 2004.

[2] V. Task, “Evaluation of islanding detection methods for photovoltaic utility-interactive power systems,” Tech. Rep. IEAPVPS T5-09:2002, March. 2002.

[3] P. Mahat, C. Zhe and B. Bak-Jensen, “Review of islanding detection methods for distributed generation,” in Third International Conference on Electric Utility Deregulation and Restructuring and Power Technologies, 2008, pp.2743-2748.

[4] Mohan, N., Underland, T.M.& Robbins, W.P. 2003 Power electronics: converters, applications, and design. 3th ed. International. John Wiley & Sons.

[5] T. Esram and P.L. Chapman, “Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques,” Energy Conversion, IEEE Transactions on , vol.22, no.2, pp.439-449, June 2007.