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Development and Implementation of Novel Techniques for the Control of Shunt Active Filter

Development and Implementation of Novel Techniques for the Control of Shunt Active Filter. By P.Rathika, Asso.Prof , Cape Institute of Technology Levengipuram , Kanyakumari . Guided By. Dr.D.Devaraj , Professor/EEE, Arulmigu Kalasalingam College of Engineering, Krishnankoil. II.

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Development and Implementation of Novel Techniques for the Control of Shunt Active Filter

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  1. Development and Implementation of Novel Techniques for the Control of Shunt Active Filter By P.Rathika, Asso.Prof, Cape Institute of Technology Levengipuram, Kanyakumari. Guided By Dr.D.Devaraj, Professor/EEE, ArulmiguKalasalingam College of Engineering, Krishnankoil

  2. II IV Plan of Presentation III I Introduction Proposed Control Strategies • Power Quality • Harmonics – an overview • Sources of harmonics • Mitigation Techniques for Harmonics • Principle of operation • Reference Current Extraction • Voltage and Current control method Shunt Active Filter Conclusions • Hysteresis Current Control Techniques • Fuzzy Logic based Current control strategies • Voltage Control Techniques • Time and Frequency domain based current extraction • Simulation Results • Hardware Implementation with Results

  3. Power Quality Quality of the current and voltage provided to the customers • Providing customers with a pure sinusoidal waveforms at 50 Hz without any deviations. • Providing power to allow sensitive electronic equipment operate reliably. Any deviation from a perfect sinusoidal waveform that can results in failure or mis-operation of customer equipment

  4. sin(5x) f(x) = 5 sin(5x) f(x) = sin(x) + 5 What are Harmonics • Harmonics • A sinusoidal voltage or current having frequencies that are integral multiples of the power frequency. In the resultant wave the sinusoidal character is lost f(x) = sin(x) = +

  5. Sources of Harmonics Modern electronic equipments such as • personal or notebook computers • laser printers • fax machines • telephone systems, stereos, radios, TVs • adjustable speed drives and variable frequency drives • battery chargers, UPS, and any other equipment powered by switched-mode power supply (SMPS) equipment Non-linear loads: draw current only a part of the voltage cycle Non-linear load devices create harmonics when they convert ac to dc, dc to dc, dc to ac, and ac to ac

  6. Harmonics Total Harmonic Distortion (THD) It is the ratio between the RMS value of the harmonic currents to the fundamental current.

  7. Harmonics Sources Examples Computer Rectifiers THD = 20 to 60% THD = 80 to 140%

  8. Effects of Harmonics • Over heating of Transformer • Excessive neutral current • Damage of sensitive electronic equipments • Tripping of Circuit Breakers • Low system efficiency • Poor power factor • Skin Effect • Interference in the nearby communication systems

  9. Recommended limits - IEEE 519 The Institute of Electrical and Electronics Engineers (IEEE) has set recommended limits on both current and voltage distortion in IEEE 519-1992. Voltage Harmonic Distortion Limits

  10. Harmonic Current Limits • Isc: Maximum short-circuit current at the Point of Common • Coupling (PCC). • IL: Maximum demand load current (fundamental) at • the PCC.

  11. 1 2 3 • Active Filter • shunt active filter • series active filter • hybrid shunt – • series active filter Passive Filter Hybrid Filter Harmonics Solution Techniques Filters: The harmonics filters are the solution to eliminate the harmonics.

  12. Basic Operation of Shunt Active Filter

  13. Reference Current Generator 1 Heart of SAF 2 3 DC Voltage Control Gating Signal Generator Heart of Shunt Active Filter

  14. Block Diagram of SAF

  15. Research Objectives This research work focuses on developing suitable control techniques and reference current extraction method for the shunt active filter for three phase 3-wire and three phase 4-wire system. The objectives are • To develop an effective and reliable control strategy for three phase shunt active filter to suppress harmonic currents and compensate reactive power under ideal, non-ideal source voltage condition and also it should maintain a constant switching frequency. • To develop an effective reference current calculation method to extract the harmonics content present in the load current under ideal, non-ideal and noisy voltage source condition. • To develop a suitable voltage controller to maintain constant voltage across the DC bus capacitor.

  16. Shunt Active Filter with Fixed Hysteresis Band Technique

  17. Hysteresis current controller When the current through the inductor exceeds the upper hysteresis limit a negative voltage is applied by the inverter to the inductor. This causes the current in the inductor to decrease. Once the current reaches the lower hysteresis limit a positive voltage is applied by the inverter to the inductor and this causes the current to increase and the cycle repeats.

  18. Current Extraction Techniques Methods • Time domain Techniques • Frequency Domain Techniques - Large number of calculation is involved hence it is less practical. Time Domain Technique • Harmonics extraction methods in the time domain are based on instantaneous derivation of compensating signals in the form of either voltage or current signals from distorted and harmonic polluted voltage or current signals.

  19. Reference Current Extraction Clarke Transformation Voltage Current …..Contd

  20. Contd….. Instantaneous Real and Reactive Power Reference compensation currents in α-β coordinates Reference compensation currents in a-b-c coordinates

  21. PI – DC Bus Voltage Control Vc ref – Reference DC Voltage Vc - Actual DC Voltage

  22. Simulation Results

  23. Test System

  24. Circuit Diagram of Shunt Active Filter

  25. Without Filter Distorted three phase line current Harmonic Spectrum of the distorted line current THD=26.34%

  26. Results with AF Three phase line current with filter Harmonic Spectrum of the line current with filter THD=4.1%

  27. Switching Frequency • The switching frequency is varying between 19kHz to 20kHz • The switching loss gets increases

  28. Constant Frequency Hysteresis Band Control

  29. Constant Frequency Hysteresis Current Control generates switching pulses based on the prediction of current error and its slope and the past switching ON/OFF time of the switches in the inverter. In this technique, the hysteresis bandwidth need not be specified in the entire control algorithm.

  30. Calculation of Switching Time The switching time is calculated from the system parameters

  31. Without Filter Distorted three phase line current Harmonic Spectrum of the distorted line current THD=26.34%

  32. Results with Filter

  33. Harmonic Contents -supply current and voltage

  34. Source voltage and Current Real and Reactive power supplied by the source to the Load

  35. Average Switching Frequency of the Inverters

  36. DRAWBACKS

  37. Fuzzy Adaptive Hysteresis Band Current Control

  38. Adaptive Hysteresis Current Control Band width

  39. Fuzzy Membership function

  40. Fuzzy Rule Base

  41. Simulation Results

  42. Test System

  43. Four wire System with APF

  44. Distorted Phase and Neutral current

  45. Ideal supply voltage conditions

  46. Ideal supply voltage conditions (Contd..)

  47. Unbalanced and Distorted Condition

  48. Result-After filtering

  49. Results Summary

  50. Average Switching Frequency

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