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Seminar on Improved Power Quality AC-DC Converters with High Frequency Transformer Isolation By Prof. Bhim Singh Department of Electrical Engineering Indian Institute of Technology Delhi Hauz Khas, New Delhi-110016, India email:[email protected] Ph.: (91)-011-2659-1045 Classification Improved Power Quality AC-DC Converters with High Frequency Transformer Isolation The control of DC-DC converter is done such as the input current wave shaping is achieved for AC-DC Diode converter. The DC-DC converter can be operated in both DCM and CCM mode. The control technique for DCM and CCM are different. It works as voltage follower in DCM mode and there is no need of input voltage & current sensing for power factor correction. Applications DC Power Supplies, Telecommunication Power Supply, Improved Power Factor ballast, Power Supplies for equipments like computers, medical equipments, printers, scanners etc. Drives Applications with Power Factor Improvement at AC side, Electrical Welding, Lighting such as ballasts, CFL etc. Single-Phase Buck Boost Flyback AC-DC Converter HFT is vs io Ls Cs Co Cd Q + Vo Load Single-Phase Buck Forward AC-DC Converter HFT is vs Ls Cs Lo io Co Cd Q + Vo Load Single-Phase Buck Push-Pull AC-DC Converter HFT is vs Ls Cs Cd Lo Co Q1 Q2 io + Vo Load Single-Phase Buck Half-Bridge AC-DC Converter HFT is vs Lo io Ls Cd1 Q1 Co Cs Cd2 Q2 + Vo Load Single-Phase Buck Full Bridge AC-DC Converter Ld is HFT io Ls Q1 vs Lo Cs Q3 Cd Co Q2 Q4 + Vo Load Single-Phase Boost Forward AC-DC Converter D1 Ld is vs HFT Lo io Ls D2 Cs Cd Q Co + Vo Load Single-Phase Boost Push-Pull AC-DC Converter HFT is vs Lo io Ls Cd Cs Ld Co + Q1 Rd Q2 + Vo Load Single-Phase Boost Half-Bridge AC-DC Converter Ld is vs HFT Lo Ls Cs io Q1 Co Q2 + Vo Load Single-Phase Boost Full Bridge AC-DC Converter Ld is vs HFT Lo io Ls Cs Q1 Q3 Q2 Q4 Cd Co + Vo Load Single-Phase Buck-Boost Cuk AC-DC Converter is vs Ls L1 Cs C1 HFT C2 L2 Co Q io + Vo Load Single-Phase Buck-Boost SEPIC ACDC Converter is vs Ls Ld Cd HFT io Co Cs Q + Vo Load Single-Phase Buck-Boost Zeta AC-DC Converter HFT is Ls C1 Lo io Q vs Cs Cd Co + Load Single-phase buck-boost flyback AC-DC converter in DCM Single-Phase Buck Boost Flyback AC-DC Converter Average current mode control in CCM operation Single-Phase Buck Boost Flyback AC-DC Converter FLYBACK Converter in DCM average input current over a switching cycle is given as: i1 1 I pk D 2 (1) where I is the peak of input current (that’s switch current) and D is the duty ratio. From Fig.1b I is given as: pk pk I pk DTs v1r Lm (2) where v1r is rectified input voltage and L is transformer magnetizing inductance referred to primary. From eqns (1) and (2), the input current is as: m D 2 Ts i1 v1r 2L m (3) Single-Phase Buck Boost Flyback AC-DC Converter Design of Flyback Converter in DCM Equation (3) presents nicely PFC operation in DCM. It is clear that if duty cycle and switching frequency is kept constant, then input current is a linear function of input voltage. Eqn. (3) can be written as: i1 I1 sin t (4) where, v1r V1 sin t (5) V1 D 2 Ts I1 2L m (6) Since input inductor current is nothing but the rectified ac mains current, thus from Eqn. (4), it is clear that by keeping the duty cycle and switching frequency constant, the average input current in flyback converter in DCM follows the input voltage exactly thus emulating a resistor and is known as voltage follower technique. Therefore, flyback converter behaves as an ideal current shaper, and performs current shaping automatically with no control when operating in DCM. Single-Phase Buck Boost Flyback AC-DC Converter Design of Flyback Converter in DCM The design of the converter depends whether it is working in discontinuous or continuous conduction mode. The transfer function of the flyback converter in DCM is given as: Vo Dv 1r D1n (7) where n is the turn ratio. From Fig. 1b, for DCM operation, the condition is: D D1 1 (8) From Eqns. (7) and (8), for the desired maximum duty ratio at minimum input voltage, turn ratio can be obtained by satisfying following inequality as: n D V1 (1 D) Vo (9) Single-Phase Buck Boost Flyback AC-DC Converter Design of Flyback Converter in DCM In order to ensure DCM of operation at maximum load, following condition must be satisfied Lm R L min 1 V 4f s ( o ) 2 n V1min (10) where V is the peak value of minimum input voltage. RL min is the minimum value of load resistance and f is the switching frequency. Output capacitor is selected on the basis of maximum peak-to-peak ripple in output voltage ( r ) as: 1 min s v Co Vo rvRL (11) Single-Phase Buck Boost Flyback AC-DC Converter Design of Flyback Converter in DCM and CCM Stresses on semiconductor devices in DCM can be given by following equations, Peak current through switch is given as: V DT I (12) L 1 s swpk m Peak voltage across switch is given as: Vswpk V1 nVo (13) Similarly, peak current through diode is as: I diopk n 2 Vo D1Ts Lm (14) and peak voltage across the diode can be given as: Vdiopk V1 Vo n (15) Single-Phase Buck Boost Flyback AC-DC Converter Design of Flyback Converter in DCM and CCM For CCM operation, the transfer function is given as: Vo Dv 1r (1 - D)n (16) Thus in a similar manner as in DCM, for desirable maximum duty ratio, the turn ratio is determined. However, magnetizing inductance of the transformer is defined by satisfying the following inequality [6]: Lm R L max V 4f s ( o ) 2 V1min (17) Referring Fig. 2b, switch current at half of the ripple is given as: I swh Pomax V1min ηD max (18) Single-Phase Buck Boost Flyback AC-DC Converter Design of Flyback Converter in DCM and CCM From Fig 2b, switch peak current for ripple I sw is given as: I sw 2 (19) V1min D max Ts Lm (20) I swpk I swh where , ΔI sw Switch RMS current is given as: 1 2 2 I swRMS D max [I swpk ΔI sw I swpk ΔI sw 3 (21) Similarly diode current at half of the ripple is given as: I dh I o max (1 Dmax ) From Fig 2b, diode peak current for ripple I dpk I dh I d 2 (22) I d is given as: (23) where, I d Vo (1 Dmax )Ts L2 (24) Single-Phase Buck Boost Flyback AC-DC Converter Specifications Input: V1 220VRMS , 50Hz, Single-Phase AC Supply Output: Vo 110V , Po 1kW , Output voltage-ripple less than 2% Switching frequency f s ( s / 2 ) 50kHz Design parameters for DCM Transformer turn ratio (n) 1.5:1, Magnetizing inductance L m 50H , L f 1mH , Cf 800nF and C o 15mF . Single-Phase Buck Boost Flyback AC-DC Converter Source voltage and current in DCM at 100% load Steady state output voltage in DCM at 100% load Single-Phase Buck Boost Flyback AC-DC Converter Source voltage and current in CCM at 100% load Steady state output voltage in CCM at 100% load Single-Phase Buck Boost Flyback AC-DC Converter TABLE I Comparisons of Flyback Converter Operation in DCM and CCM DCM Operation CCM Operation Quantity 10% Load 100% Load 10% Load 100% Load Input Current THD 12% 5.1% 11% 4.4% PF 0.981 0.997 0.989 0.998 Output Ripple 0.55% 1.73% 0.52% 1.45% Normalized Current Peak of Switch Average (pu) RMS 25.1 6.73 6.53 2.60 0.93 0.71 0.54 0.67 2.87 1.62 1.35 1.14 Normalized Current Peak of Diode Average (pu) RMS 14.5 9.76 10.13 3.95 1.13 1.48 1.29 1.16 5.27 2.86 2.57 1.90 Control Technique Voltage Mode Control Average Current Control Size of Converter Small Large Circuit Simplicity Simple Complex Single-Phase Buck Boost Flyback AC-DC Converter Vs (V), is(A) Vdc (V) Idc (A) Test results of AC mains voltage, AC mains current, output DC voltage and output DC current waveform of AC-DC flyback converter for load perturbation response on equivalent resistive load (60W to 200W to 60W). (Scale on X-axis 1div=20ms, Yaxis channel-1 1div =85V, channel-2 1div =5A, channel-3 1div= 100V, channel-4 1div= 2A) Single-Phase Buck-Boost Cuk AC-DC Converter in DCM Single-Phase Cuk AC-DC Converter Inductors voltage and current waveforms in DCM Single-Phase Cuk AC-DC Converter CCM operation Single-Phase Cuk AC-DC Converter Inductors voltage and current waveforms in CCM Single-Phase Cuk AC-DC Converter in DCM Operation To simplify the analysis, all quantities are referred to the primary side of the transformer. Volt-second balance on the inductor gives following equality: vo ' d (1) v1r d1 where vo ' and v1r are output voltage (referred to primary) and rectified input voltage respectively. d is the duty ratio and d1 is the off period of switch, during which inductor currents decrease linearly. Assuming 100% efficiency for simplification, the current ratio is: i1 d (2) i 2 ' d1 where i1 and i 2 ' are the input inductor current and output inductor current referred to primary side of the transformer. Single-Phase Cuk AC-DC Converter in DCM First stage of Operation When switch is on, two inductor currents increase linearly with the voltage across them equal to input voltage. The equations of input and output inductor currents for the interval 0 t dTs (referring to Fig. 1b(i)) are given by: v i1 i 1r t L1 v i 2 ' i 1r t L2 ' (3) (4) where i is the minimum input inductor current. Second Stage of Operation When switch is off, inductor currents decrease linearly with voltage across them equal to output voltage. Referring to Fig. 1b(ii) and Fig. 1c, inductor currents are given by: v ' v i1 o t 1r dTs i L1 L1 v ' v i 2 ' o t 1r dTs i L2 ' L2 ' (5) Single-Phase Cuk AC-DC Converter in DCM Third stage of Operation This is the stage when the diode current is zero. Averaged input and output inductor currents over a switching period can be given by [1]: v1r i1 dTs (d d1 ) i 2L1 v1r i2 ' dTs (d d1 ) i 2L 2 ' (7) (8) Sum of the input and output inductor currents is given by: i1 i 2 ' 1 v1r d dTs 1 1 d 2 L eq d L1L 2 ' L where, eq L L ' 1 2 (9) (10) Single-Phase Cuk AC-DC Converter in DCM By substituting the expression in eqn. (2) in to eqn. (9), we get: d 1 v1r d i1 1 1 dTs 1 1 d d 2 L eq d (11) After simplification it gives: v1r d 2 Ts i1 2L eq (12) It can be written as: i1 I1 sin t (13) where, v1r V1 sin t (14) V1d 2Ts I1 2L eq (15) Single-Phase Cuk AC-DC Converter Average and peak currents in the semiconductors and input inductor Average current ( i sw av ) and peak current ( i sw pk ) of the MOSFET switch over a switching cycle are as: v i sw av 1r L eq d 2Ts (I 1max I 2max ' ).d 2 (16) i sw pk (I1max I 2max ' ) (17) where I1max and I 2max ' are the maximum value of input inductor current and output inductor current (referred to primary) respectively. Average current ( i d av ' ), and peak current ( i d pk ' ) of the diode (all referred to primary) are as: v i d av ' o L eq d 2 Ts (I 1max I 2max ' ).(1 - d) 2 i d pk ' (I1max I 2max ' ) (18) (19) Single-Phase Cuk AC-DC Converter Average and peak currents in the semiconductors and input inductor Peak voltage across switch ( Vsw pk ) and diode ( Vd pk ' ) (referred to primary) is given as: Vsw pk Vd pk ' Vinmax Vo ' (20) The average current ( i L1av ) and RMS current ( i L1 rms ) of input inductor are as: 2I i L1 av 1max (21) π i L1 rms I1max 2 (22) Single-Phase Cuk AC-DC Converter Design Description in DCM and CCM Step 1: Conversion ratio Defining the dc voltage conversion ratio (M) as, V M o v1r (23) where, v1r V1 sin t (24) For t 90 , conversion ratio is obtained as the first step of the design. Here V1 is the peak value of input voltage. Step 2: Condition for operation in DCM and CCM Design must ensure the DCM operation, for which following inequality must hold good: Ke 1 2(M n) 2 where K e is the conduction parameter and n is the transformer primary to secondary turn ratio. (25) Design Description in DCM and CCM For CCM, following condition must be satisfied to ensure the continuous conduction mode of operation: 1 Ke (26) 2(M n) 2 K e is calculated for minimum value of M which occurs at minimum output voltage and maximum input voltage in CCM for given range of specification. Step 3: Equivalent inductance ( Leq ) which is the parallel combination of L1 and L 2 ' , is given as: L eq K e R L Ts 2 (27) where R L is the load resistance. Step 4: Duty Ratio The duty ratio for the given power (load resistance) in DCM is obtained by: d 2M K e (28) Design Description in DCM and CCM Step 5: L1 and L 2 ' Design L1 can be obtained by considering the specified maximum current ripple for DCM as: L1 2L eq dri (29) where ri is p.u. ripple current. L 2 ' can be obtained using expressions for L1 and L eq in eqns. (29) and (10) respectively. Similarly, for CCM L1 and L 2 ' can be obtained by specified maximum current ripple allowed and eqn. (10). Design Description in DCM and CCM Step 6: Design of energy transfer capacitor C1 It has great influence on input current waveform. To avoid input current oscillations at every line half cycle, it is given by: C1 1 (30) r 2 (L1 L 2 ' ) where, L r s Resonant frequency ( r ) should lie between line frequency ( L ) and switching frequency ( s ). Step 7: Output Capacitor Output capacitor is chosen according to specified ripple allowed in the output voltage. It can be achieved by following formula: Co 1 L rv R L min where rv is the pu ripple in the output voltage and resistance. (31) R L min is the minimum load Single-Phase Cuk AC-DC Converter Specifications Input: V1 160 270VRMS , 50Hz, Single-Phase AC Supply Output: Vo 98 132V adjustable with nominal value of 120V , Po 2.6kW Output voltage-ripple less than 2% Switching frequency f s ( s / 2 ) 50kHz Design parameters for DCM mode: Transformer turn ratio (n) 1:1, L1 1500H , L 2 4.3H , C1 2.5F , C 2 10F , and Co 30mF . Single-Phase Buck-Boost Cuk AC-DC Converter Source voltage and current in DCM at 100% load Steady state output voltage in DCM at 100% load Single-Phase Buck-Boost Cuk AC-DC Converter Source voltage and current for 100% load in CCM Steady state output voltage in CCM at 100% load Single-Phase Buck-Boost Cuk AC-DC Converter TABLE I Comparisons of Cuk Converter Operation in DCM and CCM at Full Load Quantity DCM Operation CCM Operation Input Current THD 5.5% 3.8% PF 0.998 to 1.0 0.9975 to 1.0 Ripple Factor 1.83% 1.67% Peak Current Through Device 170A 60A Control Technique Voltage Mode Control Average Current Control Size of Converter Small Large Circuit Simplicity Simple Complex Single-Phase Buck-Boost Cuk AC-DC Converter Vs (V), is(A) Vdc (V) Idc (A) Test results of AC mains voltage, AC mains current, output DC voltage and output DC current waveform of AC-DC cuk converter for load perturbation response on equivalent resistive load (60W to 200W to 60W). (Scale on X-axis 1div=20ms, Yaxis channel-1 1div =175V, channel-2 1div =5A, channel-3 1div= 100V, channel-4 1div= 1.75A) Single-Phase SEPIC AC-DC Converter in DCM Single-Phase SEPIC AC-DC Converter in DCM Single-Phase SEPIC AC-DC Converter CCM in Single-Phase SEPIC AC-DC Converter CCM in Single-Phase SEPIC AC-DC Converter Specifications Input: V1 230VRMS , 50Hz, Single-Phase AC Supply Output: Vo 110V , Po 1.5kW Output voltage-ripple less than 2% Switching frequency f s ( s / 2 ) 50kHz Transformer turn ratio (n) 1:1, L 2 8.1H , C1 1F , and Co 30mF . PI controller parameters: gain = 0.308, time constant = 0.03. L1 1200H , Single-Phase SEPIC AC-DC Converter DCM in Source voltage and current in DCM at 100% load Steady state output voltage in DCM at 100% load Single-Phase SEPIC AC-DC Converter CCM in Source voltage and current in CCM at 100% load Steady state output voltage in CCM at 100% load Single-Phase SEPIC AC-DC Converter TABLE I Comparisons of SEPIC Converter Operation in DCM and CCM DCM Operation Quantity 10% Load 100% Load CCM Operation 10% Load 100% Load Input Current THD 10% 6% 3.8% 8.5% PF 0.994 0.997 0.998 0.995 Output Ripple 0.22% 1.27% 1.1% 0.1% Peak 14.50pu 9.84pu 3.24pu 3.14pu Average 0.76pu 0.77pu 0.71pu 0.78pu RMS 4.60pu 2.18pu 1.50pu 1.39pu Peak 15.2pu 10.94pu 3.17pu 3.15pu Average 1.47pu 1.27pu 0.93pu 0.98pu RMS 7.22pu 3.34pu 1.68pu 1.56pu Normalized Current of Switch Normalized Current of Diode Control Technique Voltage Mode Control Average Current Control Size of Converter Small Large Circuit Simplicity Simple Complex Single-Phase SEPIC AC-DC Converter Vs (V), is(A) Vdc (V) Idc (A) Test results of AC mains voltage, AC mains current, output DC voltage and output DC current waveform of AC-DC sepic converter for load perturbation response on equivalent resistive load (60W to 200W to 60W). (Scale on X-axis 1div=20ms, Y-axis channel-1 1div =150V, channel-2 1div =5A, channel-3 1div= 100V, channel-4 1div= 1.75A) Single-Phase Buck-Boost Zeta AC-DC Converter in DCM Single-Phase Buck-Boost Zeta AC-DC Converter in DCM Single-Phase Buck-Boost Zeta AC-DC Converter in CCM Single-Phase Buck-Boost Zeta AC-DC Converter in CCM Single-Phase Zeta AC-DC Converter Specifications Input: V1 220VRMS , 50Hz, Single-Phase AC Supply Output: Vo = 48V, Po 1kW , output voltage-ripple less than 2% Switching frequency f s ( s / 2 ) 50kHz Transformer turn ratio (n) 5:1, inductance Lm =100μH , Lf =3mH , Lo =10mH C1 =10μF , Co =22mF , and Cf =100nF . Magnetizing Single-Phase Buck-Boost Zeta AC-DC Converter in CCM Source voltage and current in DCM at 100% load Steady state output voltage in DCM at 100% load Single-Phase Buck-Boost Zeta AC-DC Converter in CCM Source voltage and current for 100% load in CCM Steady state output voltage in CCM at 100% load Single-Phase Zeta AC-DC Converter Vs (V), is(A) Vdc (V) Idc (A) Test results of AC mains voltage, AC mains current, output DC voltage and output DC current waveform of AC-DC zeta converter for load perturbation response on equivalent resistive load (60W to 200W to 60W). (Scale on X-axis 1div=20ms, Yaxis channel-1 1div =150V, channel-2 1div =3A, channel-3 1div= 100V, channel-4 1div= 1.75A) Single-Phase Zeta AC-DC Converter TABLE I Comparisons of Zeta Converter Operation in DCM and CCM DCM Operation Quantity 10% Load 100% Load CCM Operation 10% Load 100% Load Input Current THD 11% 4.98% 9.2% 1.36% PF 0.993 0.9975 0.994 0.998 Output Ripple 0.62% 1.99% 0.67% 1.98% Peak 9.21 4.15 2.92 1.75 Average 0.92 1.01 0.45 0.62 RMS 2.15 1.71 1.04 0.95 Peak 36.90 20.01 14.6 8.73 Average 4.52 3.02 3.24 3.17 RMS 10.45 5.41 5.37 4.57 Normalized Current of Switch Normalized Current of Diode Control Technique Voltage Mode Control Average Current Control Size of Converter Small Large Circuit Simplicity Simple Complex References • • • • • • • • R. W. Erickson, Fundamentals of Power Electronics. New York: Chapman & Hall, 1997. A. I. Pressman, Switching Power Supply Design. Second Edition, New York: McGraw-Hill, 1998. P. T. Krein, Elements of Power Electronics. New York: Oxford University Press, 1998. M. H. J. Bollen, Understanding Power Quality Problems: Voltage Sags and Interruptions. New York: IEEE Press Series on Power Engineering, 2000. D. Boroyevich and S. Hiti, Three-phase PWM converter: Modeling and Control Design. Seminar 9, IEEE APEC’96, 1996. M. F. Schlecht and B.A Miwa, “Active power factor correction for switching power supplies,” IEEE Trans. Power Electron.,vol.2, pp.273281, October 1987. M. Kravitz,“Power factor correction circuit for power supplies,” U.S. Patent 4,961,044, Oct. 1990. J. Sebastian, M. Jaureguizar, and J. Uceda, “An overview of power factor correction in single-phase off-line power supply systems,” in Proc. IEEE IECON’94, 1994, pp. 1688 -1693. • • • • • • • • • • • R. Redl, I. Balogh, and N.O. Sokal, “A new family of single-stage isolated powerfactor correctors with fast regulation of the output voltage,” in Proc. IEEE PESC’94, 1994, pp. 1137 –1144. J. Sebastian, J. A. Cobos, J.M. Lopera and J. Uceda, The determination of the boundaries between continuous and discontinuous conduction modes in PWM DC-toDC converters used as power factor preregulators,” IEEE Trans. Power Electron., vol. 10, pp. 574 -582, Sept. 1995. A. Zak, “Multi-channel single stage high power factor AC to DC converter,” U.S. Patent 5,619,404, April 1997. H. Mao, F. C. Y. Lee, D. Boroyevich, “Review of high-performance three-phase power-factor correction circuits,” IEEE Trans. Ind. Electron., vol. 44, pp. 437-446, August 1997. G. A. Karvelis, S. N. Manias and G. Kostakis, “A comparative evaluation of power converters used for current harmonics elimination,” in IEEE HQP’98, 1998, pp. 227232. H. Wei and I. Batarseh, “Comparison of basic converter topologies for power correction,” in IEEE SOUTHEASTCON’98, 1998, pp. 348-353. C. Qiao and K.M. Smedley, “A topology survey of single-stage power factor corrector with a boost type input-current-shaper,” IEEE Trans. Power Electron., vol. 16, pp. 360-368, May 2001. L.Huber, J. Zhang, M.M. Jovanovic and F.C. Lee, “Generalized topologies of singlestage input-current-shaping circuits,” IEEE Trans. Power Electron., vol. 16, pp. 508513, July 2001. F.L. Williamson, “Universal input/output power supply with inherent near unity power factor,” U.S. Patent 6,343,021, Jan. 2002. M. Keller, “Design of a 250 Amp telecom rectifier with true three-phase unity power factor input rectification stage,” in Proc. IEEE INTELEC’02, 2002, pp. 94- 100. O. García, J. A. Cobos, R. Prieto, P. Alou and J. Uceda, “Single Phase Power factor correction: A survey,” IEEE Trans. Power Electron., vol. 18, pp. 749-755, May 2003.