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- 1. M.E.Sc. Thesis Wijeratne Outline A Three-Phase AC-DC Single-Stage ZVZCS Introduction PWM Full-Bridge Converter Literature Review Thesis Objectives Fundamental Principles M.E.Sc Public Lecture The Proposed Summer 2009 Converter Converter Analysis Converter Design Dunisha Wijeratne & Experimental Student Number: 250442424 Waveforms Conclusion University of Western Ontario, London, Ontario, Canada 2009 August 04
- 2. M.E.Sc. Thesis Outline 2 Wijeratne Outline Introduction Introduction Literature Review Thesis Objectives Literature Review Fundamental Principles Thesis Objectives The Proposed Converter Fundamental Principles Converter Analysis Converter Design The Proposed Converter & Experimental Waveforms Converter Analysis Conclusion Converter Design & Experimental Waveforms Conclusion
- 3. M.E.Sc. Thesis Acknowledgements 3 Wijeratne Outline I appreciate the support given by everybody to accomplish Introduction my Masters. Literature Review My supervisor Dr. Gerry Moschopoulos Thesis Objectives Fundamental My thesis examination committee, Dr. Abbas Samani, Principles Dr. Jagath Samarabandu, Dr. Kazimierz Adamiak and The Proposed Converter Dr. Mile Ostojic. Converter Analysis Dr. S. Kumarawadu of University of Moratuwa Converter Design & Experimental My senior Dr. Sondeep Bassan Waveforms Conclusion Gerrit Aartsen, Eugen Porter and Trent Steensman in the Electronics Shop Administrative staff of the ECE department My Parents.
- 4. M.E.Sc. Thesis Introduction 4 Wijeratne Introduction to Power Electronics Outline Introduction Power electronics is the field of electrical engineering related Literature Review to the use of semiconductor devices to convert power from Thesis Objectives the form available from a source to that required by a load. Fundamental A block diagram of a typical power electronic system is Principles shown in the figure below. The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 5. M.E.Sc. Thesis Introduction 5 Wijeratne Semiconductor Devices Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms MOSFET symbol IGBT symbol Conclusion Applications: MOSFETs: Low power & High switching frequency IGBTs : Low switching & High power
- 6. M.E.Sc. Thesis Introduction 6 Wijeratne Soft Switching Techniques Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design Soft switching techniques used are classified as & Experimental Waveforms Zero-voltage switching (ZVS) or Conclusion Zero-current switching (ZCS). MOSFETs have a significant drain-source capacitance, hence usually implemented with ZVS. IGBTs have a slower turn-off, hence usually implemented with ZCS.
- 7. M.E.Sc. Thesis Introduction 7 Wijeratne Ac-Dc Two-Stage Power Conversion Outline Introduction Literature Review Thesis Objectives Fundamental Principles Stage 1- Six-switch rectifier. The Proposed Converter Stage 2- Full-bridge converter(FBC) for higher power Converter Analysis applications. Converter Design & Experimental Example Waveforms Conclusion
- 8. M.E.Sc. Thesis Introduction 8 Wijeratne Problem Statement Outline Introduction The standard practice is to use two separate power Literature Review converters to convert an ac input voltage to a desired & Thesis Objectives isolated dc output voltage, where the front end converter is Fundamental Principles performing the power factor correction(PFC) & back The Proposed converter is performing the isolation. Converter Converter Analysis Solution Converter Design & Experimental A new 3-phase, single-stage ac-dc full-bridge converter is Waveforms proposed in the thesis that is cost effective, relatively simple Conclusion in design & which can be switched using standard PWM techniques. Goto S6
- 9. M.E.Sc. Thesis Introduction 8 Wijeratne Problem Statement Outline Introduction The standard practice is to use two separate power Literature Review converters to convert an ac input voltage to a desired & Thesis Objectives isolated dc output voltage, where the front end converter is Fundamental Principles performing the power factor correction(PFC) & back The Proposed converter is performing the isolation. Converter Converter Analysis Solution Converter Design & Experimental A new 3-phase, single-stage ac-dc full-bridge converter is Waveforms proposed in the thesis that is cost effective, relatively simple Conclusion in design & which can be switched using standard PWM techniques. Goto S6
- 10. M.E.Sc. Thesis Introduction 9 Wijeratne Full-Bridge Converter Operation Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design S1 & S2 are on; & Experimental Waveforms Transformer Voltage= +ve Conclusion Power Transfer Mode S2 is off, the body-diode of S3 & S1 are on Transformer Voltage= 0 Freewheeling Mode
- 11. M.E.Sc. Thesis Introduction 10 Wijeratne Dc-Dc Full-Bridge Converter (Contd) Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design S1 is off & the body-diode of S4 & S3 are on & Experimental Waveforms Transformer Voltage= −ve Conclusion Power Transfer Mode S3 is off & the body-diode of S2 & S4 are on Transformer Voltage= 0 Freewheeling Mode Goto S1
- 12. M.E.Sc. Thesis Introduction 11 Wijeratne Phase-Shift Pulse Width Modulation Outline Introduction The output dc voltage is controlled by controlling the Literature Review width of the +ve & −ve voltage pulses relative to the Thesis Objectives zero voltage portions of the transformer. Fundamental This is done by shifting the gating signal pulses of the Principles switches in one leg, relative to those of the switches in The Proposed Converter the other leg. Converter Analysis Converter Design & Experimental Waveforms Conclusion This is considered to be the standard controlling of a dc-dc full-bridge converter.
- 13. M.E.Sc. Thesis Literature Review 12 Wijeratne Outline Ac-Dc Front-End Converters Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design The Standard practice- 6-switch ac-dc Rectifier & Experimental Waveforms Converter. Conclusion Disadvantage: Too many switches lead to complication & cost increase.
- 14. M.E.Sc. Thesis Literature Review 13 Wijeratne Modular Approach Outline Introduction Each module is 2-staged, where PFC boost converter is Literature Review followed by a dc-dc converter. Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion Advantage: Available single-phase modules can be used. Disadvantage: The operation of each module should be synchronized with respect to others.
- 15. M.E.Sc. Thesis Literature Review 14 Wijeratne Reduced Switch Front-end Rectifiers Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design Advantage: & Experimental Waveforms Ac-dc rectifier switches are reduced to 4. Conclusion Disadvantages: Still requires 7 or 8 switches in total. 2-stage power conversion.
- 16. M.E.Sc. Thesis Literature Review 15 Wijeratne Three-phase Single-Switch Ac-Dc Front-end Rectifier Outline Introduction There are 2 types: Literature Review Boost (step-up) converter Thesis Objectives Buck (step-down) converter Fundamental Principles Boost converter operation: The Proposed When S is on, each line inductor current rises to a peak Converter proportional to the voltage applied in that switch cycle. Converter Analysis When S is off, inductors discharge into the output Converter Design capacitor, currents fall to zero. & Experimental Waveforms Conclusion Single-switch boost converter Inductor current
- 17. M.E.Sc. Thesis Literature Review 16 Wijeratne Three-phase Single-Switch Ac-Dc Front-end Rectifier Outline Introduction Operation of Buck Converter Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Single-switch buck converter Capacitor voltage Analysis Converter Design & Experimental When the switch is on input capacitors (Ca , Cb , & Cc ) Waveforms discharge into the load. Conclusion Capacitors charge with line currents when the switch is off. For PFC at the input side input capacitors must be discontinuous. Discontinuous capacitor voltage is bounded by the sinusoidal average.
- 18. M.E.Sc. Thesis Literature Review 17 Wijeratne Three-Phase Single-Stage Ac-Dc Converters Outline Introduction Single-stage converter: A single converter performs both Literature Review functions of PFC & dc-dc isolation. Thesis Objectives Plenty of research on low power, single-stage converters, Fundamental Principles but inadequate research on 3-phase, single-stage The Proposed converters. Converter Converter This is because of the challenges of merging PFC & Analysis dc-dc conversion over a much wider load range than Converter Design & Experimental what the low power converters encounter. Waveforms Conclusion There are many drawbacks associated with the existing single-stage converters.
- 19. M.E.Sc. Thesis Literature Review 18 Wijeratne Some Examples-Three-Phase Single-Stage Converters Outline Introduction Example 1 Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 20. M.E.Sc. Thesis Literature Review 18 Wijeratne Some Examples-Three-Phase Single-Stage Converters Outline Introduction Example 2 Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 21. M.E.Sc. Thesis Literature Review 18 Wijeratne Some Examples-Three-Phase Single-Stage Converters Outline Introduction Example 3 Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 22. M.E.Sc. Thesis Literature Review 18 Wijeratne Some Examples-Three-Phase Single-Stage Converters Outline Introduction Example 4 Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 23. M.E.Sc. Thesis Thesis Objectives 19 Wijeratne Outline To propose a new 3-phase, ac-dc, single-stage, PWM Introduction converter that can operate with an excellent input power Literature Review factor & that does not have the disadvantages of the Thesis Objectives existing 3-phase single-stage converters. Fundamental Principles The Proposed To analyze its steady-state operation & determine its Converter steady-state characteristics. Converter Analysis Converter Design To develop guidelines & a procedure for designing the & Experimental Waveforms proposed converter. Conclusion To confirm its feasibility with results obtained from a experimental prototype.
- 24. M.E.Sc. Thesis Fundamental Principles 20 Wijeratne Outline The proposed single-stage converter is based on the Introduction combination of Literature Review A single-switch 3-phase buck converter, Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 25. M.E.Sc. Thesis Fundamental Principles 20 Wijeratne Outline The proposed single-stage converter is based on the Introduction combination of Literature Review A single-switch 3-phase buck converter, Thesis Objectives Fundamental A dc-dc zero-voltage-zero-current switched (ZVZCS) Principles The Proposed full-bridge converter. Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 26. M.E.Sc. Thesis Fundamental Principles 20 Wijeratne Outline The proposed single-stage converter is based on the Introduction combination of Literature Review A single-switch 3-phase buck converter, Thesis Objectives Fundamental A dc-dc zero-voltage-zero-current switched (ZVZCS) Principles The Proposed full-bridge converter. Converter Converter Ac-Dc Three-Phase Single-Switch Buck Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 27. M.E.Sc. Thesis Fundamental Principles 21 Wijeratne Three-Phase Single-Switch Buck Converter-Modes of Outline Operation Introduction During a typical switching cycle, the converter goes through Literature Review 3 significant modes of operation: Goto 20 Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Mode 1 Mode 2 Conclusion Mode 3
- 28. M.E.Sc. Thesis Fundamental Principles 22 Wijeratne Input PFC in Single-Switch Buck Converter Outline Introduction The input currents are sinusoidal & in phase with the Literature Review input phase voltages if input capacitors completely Thesis Objectives discharge as shown. Goto 21 Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion When the average input capacitor voltages are sinusoidal, voltages across input inductors are sinusoidal.
- 29. M.E.Sc. Thesis Fundamental Principles 23 Wijeratne Dc-Dc Zero-Voltage-Zero-Current Switched (ZVZCS) Outline Full-Bridge Converter Introduction Literature Review A conventional dc-dc FBC is essentially a buck Thesis Objectives converter, but with transformer isolation. Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Dc-dc full-bridge converter Dc-dc buck converter Conclusion In a typical FBC primary current flows in the reverse direction out of the converter & back into the source. If a FBC is to replace the the buck converter, then there cannot be a reverse current.
- 30. M.E.Sc. Thesis Fundamental Principles 24 Wijeratne Can ZVZCS Full-Bridge Converter replace Single-Switch Outline Buck Converter? Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms A ZVZCS converter has the property that most of the Conclusion circulating primary current when it is in a freewheeling mode can be extinguished, so there is no current in the anti-parallel diodes of the switches when the converter exits a freewheeling mode.
- 31. M.E.Sc. Thesis Fundamental Principles 25 Wijeratne Dc-Dc ZVZCS Full-Bridge Converter Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Similar to conventional dc-dc FBC, except for the Conclusion passive circuit of Cx , Dc & Dd . Cx impresses a counter voltage across the transformer primary during a freewheeling mode to extinguish the circulating current.
- 32. M.E.Sc. Thesis Fundamental Principles 26 Wijeratne Dc-Dc ZVZCS FBC Modes of Operation Outline Introduction Literature Review Thesis Objectives Fundamental Principles Mode 1 (t0 < t < t1 ) The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Mode 2 (t1 < t < t2 ) Conclusion Mode 3 (t2 < t < t3 ) Goto S2
- 33. M.E.Sc. Thesis Fundamental Principles 27 Wijeratne Dc-Dc ZVZCS FBC Modes of Operation Outline Introduction Literature Review Thesis Objectives Fundamental Principles Mode 4 (t3 < t < t4 ) The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Mode 5 (t4 < t < t5 ) Conclusion Mode 6 (t5 < t < t6 ) Goto 26
- 34. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 28 Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms The converter consists of a 3-phase L-C filter, a 3-phase Conclusion diode bridge rectifier, & a ZVZCS full-bridge converter. The most important thing to note is that the FBC acts like the switch in the 3-phase, single switch, ac-dc buck converter.
- 35. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 29 Outline Comparison Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion Power Transfer Mode
- 36. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 29 Outline Comparison Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion Freewheeling Mode
- 37. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 30 Outline Introduction Modes of Operation Mode 1 (t0 < t < t1 ) Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms At t = t0 , S2 is on with ZCS & current If b , flows into Conclusion the FBC. If b is made of the currents of the input capacitors & the input inductors. The transformer secondary current charges the auxiliary capacitor, Cx through diode Dc .
- 38. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 31 Outline Introduction Mode 2 (t1 < t < t2 ) Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms At t = t1 , Ca , Cb , Cc are fully discharged & the dc bus Conclusion voltage is zero. Since Ca no longer provides current into the FBC, If b , is constant & equals Ia . The t/f leakage inductor (Llk ) current drops due to the impressed counter voltage across Llk by Cx . Cx continues to charge & mode ends at t = t2 when S1 is off.
- 39. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 32 Outline Introduction Mode 3 (t2 < t < t3 ) Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms At t = t2 , the capacitors of S1 & S4 charge & discharge Conclusion respectively. The current in the FBC continues to decrease. Since ILlk drops below that coming from the input inductors, Ia starts to flow into Ca . During mode 3, the capacitor across S4 , is fully discharged & its body diode starts to conduct.
- 40. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 33 Outline Introduction Mode 4 (t3 < t < t4 ) Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms At t = t3 , S4 is tuned on with ZVS. Conclusion The t/f primary current, ILlk freewheels through the 2 bottom switches & continue to decrease. Entire input inductor currents flow through the input capacitors. The mode ends when diode Dd begins to conduct & discharge Cx .
- 41. M.E.Sc. Thesis A New Three-Phase Single-Stage ZVZCS Wijeratne Ac-Dc Converter 34 Outline Introduction Mode 5 (t4 < t < t5 ) Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms At t = t5 , there is no current flowing in the t/f primary. Conclusion This allows S2 to be turned off with ZCS. The input capacitors charge & Cx discharges via Dd .
- 42. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 35 Outline Introduction Mode 6 (t5 < t < t6 ) Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental At t = t5 , ILlk is zero & Cx continues to discharge as Waveforms Conclusion the entire load current flows through it. Input capacitors continue to charge. At t = t6 , S3 is turned on with ZCS & current starts to flow through S3 & S4 . The converter will then go through the same modes of operation for the remaining half cycle. Goto S2
- 43. M.E.Sc. Thesis A New Three-Phase Single-Stage Ac-Dc Wijeratne ZVZCS Converter 36 Outline Converter Features Introduction Literature Review The converter can operate with standard phase-shift Thesis Objectives PWM. Fundamental Principles The input currents are continuous; do not have a very The Proposed Converter large ripple, therefore additional input filtering is Converter avoided. Analysis Converter Design & Experimental Since the input currents are continuous, the Waveforms semiconductor peak current stresses are not excessive. Conclusion The converter does not have the circulating current in a freewheeling mode so fewer conduction losses. The converter is inexpensive & simple.
- 44. M.E.Sc. Thesis Converter Analysis 37 Wijeratne Outline Purpose: to derive expressions and determine relations Introduction of key converter parameters. Literature Review Relations obtained can then be used to draw the Thesis Objectives characteristic curves which would aid the design process. Fundamental Principles Input Capacitor Relations-Input Capacitor & Peak Switch The Proposed Voltage Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion The input capacitors must be discontinuous in order have a good PF at input side. Smaller capacitors would operate in discontinuous voltage mode (DVM) throughout the line cycle.
- 45. M.E.Sc. Thesis Converter Analysis 38 Wijeratne Input Capacitor & Peak Switch Voltage (Contd) Outline Introduction Ca , however, cannot be too small as it determines the Literature Review peak voltage stress of the switches. Thesis Objectives The conflicting criteria of having an excellent input PF Fundamental & not having excessive switch stress must be considered Principles The Proposed when implementing the converter. Converter The input currents may not be perfectly sinusoidal, but Converter Analysis should meet the appropriate standards if it is to be used Converter Design in the industry. & Experimental Waveforms Conclusion Input Capacitor & Output Dc Voltage Ca also affects the output dc voltage Vo . Ca affects the shape of the dc bus voltage, Vbus & Vo is dependent on the average Vbus .
- 46. M.E.Sc. Thesis Converter Analysis 39 Wijeratne Input Capacitor & Output Dc Voltage Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design In a standard dc-dc FBC, the ratio of Vo to Vbus can be & Experimental Waveforms expressed as in (1): Conclusion Vo = nD (1) Vbus,ave Therefore, Ca should also be selected such that, Vbus is sufficient enough to give required Vo to the load.
- 47. M.E.Sc. Thesis Converter Analysis 40 Wijeratne Input Capacitors, Voltage Ratio V & Duty Ratio D Outline Introduction After a thorough analysis, a relation between D, V & K Literature Review as in (2) is obtained. Thesis Objectives 1 η Fundamental V = (2) Principles (1 − D) K The Proposed Converter Where K is defined as, Converter Analysis Ts Converter Design K= & Experimental 2RC Waveforms Conclusion
- 48. M.E.Sc. Thesis Converter Analysis 41 Wijeratne Voltage Conversion Ratio(V ) vs. Duty Ratio(D) Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion To compromise between the switch stress & input PF, Ca is selected so that VCa drops to zero just at the end of an energy transfer mode then immediately rises when the converter enters a freewheeling mode.
- 49. M.E.Sc. Thesis Converter Analysis 42 Wijeratne Input Inductor Relation Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design Figure above shows a per phase equivalent circuit of L-C & Experimental Waveforms filter section which is helpful to find the relationship (3) Conclusion between Ca , La & line current harmonics. 2 Itfr 1 La Ca = 1+ (3) 2πfr 0.2Itfr
- 50. M.E.Sc. Thesis Converter Analysis 43 Wijeratne Transformer Leakage Inductor Relations Outline Introduction The t/f leakage inductance Llk prevents the premature Literature Review charging of the input capacitors. Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design Discontinuous input Capacitor voltage Transformer equivalent circuit & Experimental Waveforms In order to slow down the rate of discharge of Ca , time Conclusion constant, TC should be selected closer to the duration of energy transfer mode as in (4). VBDV M Ts Llk Ca ≥ · (4) n 2
- 51. M.E.Sc. Thesis Converter Analysis 44 Wijeratne Leakage Inductance vs. Input Capacitors Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 52. M.E.Sc. Thesis Converter Analysis 45 Wijeratne Auxiliary Capacitor Relations Outline Introduction The main function of Cx is to extinguish the primary Literature Review current in the transformer. Thesis Objectives Cx is selected considering equilibrium between the Fundamental energy stored & energy supplied by Cx to the load & to Principles Llk . The Proposed Converter 1 Converter Cx VCx,pk 2 − VCx,min 2 = Analysis 2 1 Converter Design & Experimental .Llk n.IL0 2 Waveforms 2 Ts Conclusion + R.IL0 2 − t4 2 Goto S4
- 53. M.E.Sc. Thesis Design & Experimental Results 46 Wijeratne Outline Design Specification Converter Parameters Introduction Literature Review Input voltage: 208 Vll,rms Duty ratio: D=0.55 Thesis Objectives Turns ratio: n= 0.3 Fundamental Principles Line frequency: 60 Hz Input capacitors: Ca = Cb = The Proposed Cc = 60nF Converter Output voltage: Vo = 48 Vdc Input inductors: La = Lb = Converter Analysis Lc =250 µH Converter Design & Experimental Leakage inductance: Waveforms Output power: 1.92 kW Llk =30 µH Conclusion Auxiliary capacitor: Switching frequency: Cx =38 µF fs =50 kHz Peak switch voltage stress: Vsw,pk =1026 V
- 54. M.E.Sc. Thesis Design & Experimental Results 46 Wijeratne Outline Design Specification Converter Parameters Introduction Literature Review Input voltage: 208 Vll,rms Duty ratio: D=0.55 Thesis Objectives Turns ratio: n= 0.3 Fundamental Principles Line frequency: 60 Hz Input capacitors: Ca = Cb = The Proposed Cc = 60nF Converter Output voltage: Vo = 48 Vdc Input inductors: La = Lb = Converter Analysis Lc =250 µH Converter Design & Experimental Leakage inductance: Waveforms Output power: 1.92 kW Llk =30 µH Conclusion Auxiliary capacitor: Switching frequency: Cx =38 µF fs =50 kHz Peak switch voltage stress: Vsw,pk =1026 V
- 55. M.E.Sc. Thesis Design & Experimental Results 46 Wijeratne Outline Design Specification Converter Parameters Introduction Literature Review Input voltage: 208 Vll,rms Duty ratio: D=0.55 Thesis Objectives Turns ratio: n= 0.3 Fundamental Principles Line frequency: 60 Hz Input capacitors: Ca = Cb = The Proposed Cc = 60nF Converter Output voltage: Vo = 48 Vdc Input inductors: La = Lb = Converter Analysis Lc =250 µH Converter Design & Experimental Leakage inductance: Waveforms Output power: 1.92 kW Llk =30 µH Conclusion Auxiliary capacitor: Switching frequency: Cx =38 µF fs =50 kHz Peak switch voltage stress: Vsw,pk =1026 V
- 56. M.E.Sc. Thesis Design & Experimental Results 47 Wijeratne Experimental Prototype Outline Introduction Literature Review MOSFETs: IXFN32N120-ND Thesis Objectives Fundamental Principles IGBTs: IXDH20N120-ND The Proposed Converter Converter Analysis Secondary side diodes: RHRP1560 Converter Design & Experimental Waveforms 3-phase diode rectifier: 36MT160 Conclusion It should be noted that the experimental waveforms will be compared to waveforms obtained with PSIM, well-known, commercially available power electronics software.
- 57. M.E.Sc. Thesis Design & Experimental Results 48 Wijeratne ZVS Leg Waveforms Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Simulation: Switch voltage(top) & current(bottom) [V: 250V/div, I: 10A/div, t: 5µs/div] Converter Analysis Converter Design & Experimental Waveforms Conclusion Experimental: Switch voltage(top) & switch current(bottom) [V: 500V/div, I: 25A/div, t: 2.5µs/div]
- 58. M.E.Sc. Thesis Design & Experimental Results 48 Wijeratne ZVS Leg Waveforms Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Simulation: Gate pulse(top) & switch current(bottom) [V: 5V/div, I: 10A/div, t: 1µs/div] Converter Analysis Converter Design & Experimental Waveforms Conclusion Experimental: Gate pulse (top) and switch current (bottom)[V: 25V/div, I: 25A/div, t: 1µs/div]
- 59. M.E.Sc. Thesis Design & Experimental Results 49 Wijeratne ZCS Leg Waveforms Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Simulation: Switch voltage (top) & switch current (bottom) [V: 250V/div, I: 5A/div, t: 5 µs/div] Converter Analysis Converter Design & Experimental Waveforms Conclusion Experimental: Switch voltage (top) & switch current (bottom) [V: 500V/div, I: 25A/div, t: 5 µs/div]
- 60. M.E.Sc. Thesis Design & Experimental Results 49 Wijeratne ZCS Leg Waveforms Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Simulation: Gate pulse (top) & switch current (bottom) [V: 5V/div, I: 10A/div, t: 5µs/div] Converter Analysis Converter Design & Experimental Waveforms Conclusion Experimental: Gate pulse (top) & switch current (bottom) [V: 25V/div, I: 10A/div, t: 5µs/div]
- 61. M.E.Sc. Thesis Design & Experimental Results 50 Wijeratne Input Voltage & Current Waveforms Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Simulation: Input phase voltage & input phase current [V: 100V/div, I: 20A/div, t: 4ms/div] Converter Analysis Converter Design & Experimental Waveforms Conclusion Experimental: Input phase voltage & input phase current [V: 75V/div, I: 10A/div, t: 4ms/div]
- 62. M.E.Sc. Thesis Design & Experimental Results 51 Wijeratne Input Capacitor Voltage Waveforms- Over Several Outline Switching Cycles Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Simulation: Input capacitor voltage measured across Ca [V: 200V/div, t=5ms/div] Converter Design & Experimental Waveforms Conclusion Experimental: Input capacitor voltage measured across Ca [V: 200V/div, t=5ms/div]
- 63. M.E.Sc. Thesis Design & Experimental Results 52 Wijeratne Input Capacitor Voltage Waveforms- Over Several Line Outline Cycles Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Simulation: Input capacitor voltage measured across Ca [V: 200V/div, t=4ms/div] Converter Design & Experimental Waveforms Conclusion Experimental: Input capacitor voltage measured across Ca [V: 200V/div, t=4ms/div]
- 64. M.E.Sc. Thesis Conclusion 53 Wijeratne Summary Outline Introduction The objective of this thesis was to propose, analyze, Literature Review design, implement, & experimentally confirm the Thesis Objectives operation of a new three-phase, ac-dc, converter, which Fundamental does not have the drawbacks of previously proposed Principles circuits. The Proposed Converter In this thesis, a background study of the 3-phase ac-dc Converter Analysis converters was carried out. Converter Design & Experimental The derivation of the proposed converter was presented. Waveforms Conclusion The general operating principles of the converter were reviewed. The converter’s steady-state modal operation was discussed.
- 65. M.E.Sc. Thesis Conclusion 54 Wijeratne Summary (Contd) Outline Introduction Considering the relationships between key parameters Literature Review graphs of steady-state characteristics were obtained. Thesis Objectives They were used as part of the design procedure to select Fundamental Principles the key converter parameters. The Proposed Converter A prototype was built & its functionality was confirmed Converter Analysis with simulation & obtained experimental results. Converter Design & Experimental Waveforms Conclusion Conclusion It is possible to combine a 3-phase, single switch ac-dc buck converter with a dc-dc ZVZCS FBC to get a feasible 3-phase, single-stage, ac-dc converter. The converter can operate with a very good input PF as long as the input capacitor operate in DVM.
- 66. M.E.Sc. Thesis Conclusion (Contd) 55 Wijeratne Conclusion Outline Introduction Smaller the input capacitors, the better the input PF, Literature Review larger the maximum peak voltage of converter switches. Thesis Objectives A trade-off between peak switch voltage stress & input Fundamental Principles PF is made. The Proposed Converter If Llk is too small, then the input capacitors may start Converter Analysis to recharge while the converter is in an energy transfer Converter Design mode. & Experimental Waveforms The input capacitors determine converter’s ability to Conclusion produce the required output dc voltage. If they are too small, can’t store sufficient amount of energy during freewheeling which can be transferred during an energy transfer mode.
- 67. M.E.Sc. Thesis Conclusion 56 Wijeratne Contributions Outline Introduction A new 3-phase, ac-dc, single-stage, ZVZCS full-bridge Literature Review PWM converter that can operate with an excellent input Thesis Objectives PF was proposed & its operation was explained. Fundamental Principles The steady-state operation was analyzed & its The Proposed Converter characteristics were determined. Converter Analysis A procedure for its design was derived & demonstrated. Converter Design & Experimental Waveforms The feasibility & the properties of the new converter Conclusion were confirmed by simulation & by experimental results obtained from a prototype.
- 68. M.E.Sc. Thesis Conclusion 57 Wijeratne Proposal for Future Work Outline Introduction The switches in the ZCS leg of the converter turn off Literature Review with almost zero reverse current. Thesis Objectives This reverse current was absorbed by small, passive RCD Fundamental Principles snubber circuit connected across the dc bus. The Proposed Converter For future work, the dissipative snubber can be replaced Converter by suitable non-dissipative snubber to improve the Analysis efficiency. Converter Design & Experimental Waveforms The lack of a dc bus capacitor in the proposed converter Conclusion means that it cannot be used in applications as a stand alone converter if hold-up is required. For future work, some means to introduce energy storage at the dc bus can be investigated.
- 69. M.E.Sc. Thesis Wijeratne Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Thank you Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 70. M.E.Sc. Thesis Wijeratne Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Supplementary Slides Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 71. M.E.Sc. Thesis Typical Full-Bridge Converter Waveforms Wijeratne Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 72. M.E.Sc. Thesis Typical ZVZCS Converter Waveforms Wijeratne Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion Return to 10
- 73. M.E.Sc. Thesis Typical Waveforms of the Proposed Wijeratne Converter Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 74. M.E.Sc. Thesis Converter Analysis Wijeratne Auxiliary Capacitor Relations Outline Introduction The main function of Cx is to extinguish the primary Literature Review current in the transformer. Thesis Objectives Cx is selected considering equilibrium (5) between the Fundamental energy stored & energy supplied by Cx to the load & to Principles Llk . The Proposed 1 Converter Cx VCx,pk 2 − VCx,min 2 = Converter 2 Analysis 1 Converter Design .Llk n.IL0 2 & Experimental 2 Waveforms Ts Conclusion + R.IL0 2 − t4 2 Yields to, 1 Ts 2 .Llk n.IL0 2 + R.IL0 2 2 − t4 Cx = 2 · (5) VCx,pk 2 − VCx,min 2 Return to 45
- 75. M.E.Sc. Thesis Converter Analysis Wijeratne Boundary Discontinuous Voltage Mode Outline Introduction The converter can be said to be operating in boundary Literature Review discontinuous voltage mode (BDVM). Thesis Objectives 1 Fundamental KBDV M = (6) Principles n2 D2 (1 − D)2 The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion
- 76. M.E.Sc. Thesis Costing of the Proposed Converter Wijeratne Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion Return to 8 Go to S7
- 77. M.E.Sc. Thesis Cost Comparison Wijeratne Outline Introduction Literature Review Thesis Objectives Fundamental Principles The Proposed Converter Converter Analysis Converter Design & Experimental Waveforms Conclusion Return to S6