A novel two-quadrant (2Q) zero-current-transition (ZCT) converter with the capabilities of 2Q power flow, and ZCT switching profile for DC motor drives is presented. It possesses the advantages that both the main and auxiliary switches can operate with zero-current switching (ZCS), reduced switching losses and stresses, minimum voltage and current stresses as well as minimum circulating energy during both the motoring and regenerating modes. This converter is particularly useful for DC traction systems in which both motoring and regenerative braking are desired to have high efficiencypublished_or_final_versio

Chan, CC

Chau, KT

Ching, TW

International Journal of Electronics

HKU Scholars Hub

Title A novel two-quadrant zero-current transition converter for dcmotor drivesAuthor(s) Ching, TW; Chau, KT; Chan, CCCitationThe 24th Annual Conference of the IEEE Industrial ElectronicsSociety (IECON '98), Aachen, Germany, 31 August-4 September1998. In Conference Proceedings, 1998, v. 2. p. 715-720Issued Date 1998URL http://hdl.handle.net/10722/99231Rights Creative Commons: Attribution 3.0 Hong Kong LicenseA Novel Two-Quadrant Zero-Current-Transition Converter for DC Motor Drives T. W. Ching, K.T. Chau, and C.C. Chan Department of Electrical & Electronic Engineering The University of Hong Kong Pokfulam, Hong Kong, China twching@eee.hku.hk Abstract - A novel two-quadrant (24) zero-current- transition (ZCT) coinverter with the capabilities of 2Q power flow, and ZCT switching profile for DC motor drives is presented. It possesses the advantages that both the main and auxiliary switches can operate with zero-current switching (ZCS), reduced switching losses and stresses, minimum voltage and current stresses as well as minimum circulating energy during both the motoring and regenerating modes. This converter is particularly useful for DC traction systems in which both motoring and regenerative braking are desired to have high efficiency. I. INTRODUCTION Nowadays, the use of low-inductance DC motors is becoming attractivc because of the advantages of higher power density, lower rotor inertia, smoother commutation and lower manufacl uring costs. However, it usually suffers from high current ripples, resulting in increased losses and switching stresses. To alleviate this problem, the switching frequency of power converters needs to be increased from less than one to over one hundred kilohertz. With available power devices technologies, hard-switching PWM converters operating at such high frequencies impose high switching losses and switching stresses. Recently, a number of soft-switching techniques, providing zero-vol tage switching (ZVS) or zero-current switching (ZCS) conditions, have been successhlly developed for switched-mode power supplies (SMPS) [ 11- [5]. Surprisingly, the development of soft-switching converters for DC imotor drives has been very little. Even so, it has been assumed that those being developed for SMPS can be directly applicable. Until recently, a systematic evaluixtion of available soft-switching converters for DC motor drives has been carried out [6], [7]. As a result, these soft-switching converters cannot satisfy the operating requirements of DC motor drives. Apart from suffering excessive voltage and current stresses, they cannot handle bidirectional power flow during regenerative braking. Different to SMPS, DC motor drives especially for traction application:, need regenerative braking. Technically, the DC motor operates as a generator to convert the kinetic energy into the electrical energy while the converter must allow for bidirectional power flow to restore the energy to the power networks or battery systems. This energy- recovery feature is particularly attractive to electric railways and battery-powered electric vehicles. 11. TWO QUADRANT CONVERTER DC DRIVES Fig. 1 shows the circuit diagram of the conventional 24-  PWM converter for DC motor drives. Conventional PWM converters process power by interrupting power flow by means of abrupt switching. This operation results in pulsating currents and voltages, thus imposing high voltage and current stresses on semiconductor devices and contributing to electromagnetic interference (EMI). Resonant type converters, including the series resonant converter (SRC), parallel resonant converter (PRC), class-E converter (CEC), quasi-resonant converter (QRC) and multi- resonant converter (MRC), process power in a sinusoidal or quasi-sinusoidal form. The power switches are commutated with either ZVS or ZCS. Hence, the switching losses and stresses of these resonant type converters are reduced in comparison with the conventional PWM converters. Recently, a 2Q-ZVS MRC has been applied to DC motor drive [6]. The corresponding schematic diagram is shown in Fig. 2. The major advantages of this converter are: 0 0 0 constant-frequency operation, 0 0 However, the high circulating energy and hence the conduction losses are significantly increased, resulting the power devices and other circuit components to be rated for higher VA ratings, as compared with their PWM counterpart. Very recently, a 2Q-ZVT converter has been newly proposed for DC motor drives [7]. It possesses the advantages that both main transistors and rectifiers can switch with ZVS and unity device stresses during both the motoring and regenerating modes of operation. Fig. 3 shows its circuit diagram. This new ZVT converter is particularly useful for those DC motor applications, employing power devices such as power MOSFET, suffering from severe capacitive tum-on switching losses. Following the spirit of our previous development on the 2Q-ZVT in [7], the purpose of this paper is to propose a novel 2 4  zero-current-transition (ZCT) converter for DC motor drives. Differing from the 2Q-ZVT converter, this 2Q-ZCT converter takes the role to be particularly useful for those DC motor applications, employing power devices such as IGBT, suffering from severe inductive turn-off switching losses. ZVS operation of both power switches, full ranges of both voltage conversion-ratio and load, capability of short-circuit operation, and absorption of all major parasitics. 0-7803-4503-7/98/$10.00 1998 IEEE 715 111. PRINCIPLE OF OPERATION OF 2Q-ZCT CONVERTER Fig. 4 shows the circuit diagram of the proposed 24- ZCT converter for, DC motor drives. Compared with the conventional 2Q-PWM converter, the proposed converter needs additional components - a resonant inductor Lr , a resonant capacitor Cr and two auxiliary switches Sa and Sa'. It should be noted that these additional components are inevitable for soft-switching operation. In fact, the corresponding hardware count is minimum. The theoretical waveforms and diagrams of the proposed 2Q-ZCT converter are illustrated by Figs. 5-8. The operating waveforms in both the motoring and regenerating modes are shown in Figs. 5 and 7, respectively. The corresponding topological stages are shown in Figs. 6 and 8, respectively. From Figs. 6 and 8, it can be found that both modes of operation consist of nine stages within one switching cycle. Fig. 1. Conventional 2Q-PWM converter for DC motor drives. d S  A. Motoring Mode (Figs. 5 and 6) Fig. 2.2Q-ZVS MRC for DC motor drives A s  Fig. 3.2Q-ZVT converter for DC motor drives. Fig. 4. Proposed 2Q-ZCT converter for DC motor drives. (a) Stage 1 [T,-T,]: Sa is tumed on and Lr and Cr start resonating. i, increases from zero to peak, then decreases towards zero, and changes direction. i, reaches -I, at T,  and the antiparallel diode of Sa becomes on. (b) Stage 2 [T,-T,]: Sa is turned off while S is turned on with ZCS at TI. The current of D' is directed to the auxiliary circuit. i, increases rapidly towards zero. (c) Stage 3 [T2-T3]: i, retums to zero at T2 and the antiparallel diode of Sa is tumed off naturally. Lr and Cr continue resonating and the positive i, is conducted by D,'. When i, returns to zero, D,' turns off naturally at T3. Stage 5 [T4-T5]: Before S is tumed on, Sa is turned on again. Lr and Cr start resonating. i, increases from zero to peak, then decreases towards zero, and changes direction. When it reaches -I, at T,, the antiparallel diode of Sa becomes on. (f) Stage 6 [T,-T,]: At T,, i, reaches -I, and the current of S is reduced to zero, thus S is turned off with ZCS. i, keeps decreasing, and flows through the antiparallel diode of S. (d) Stage 4 [T3-T4]: It is a forward powering mode. (e) 0-7803-4503-7/98/$10.00 1998 IEEE 716 Stage 7 [T,-T,]: At Ts, i, reaches to -1, and the antiparallel diode of S stops conducting. Stage 8 [T7-T8]: At T,, vCr is discharged to zero, and D starts to conduct. The current in D increases gradually. Stage 9 [T8-T9]: It is a freewheeling mode via D. B. Regenerating Mode (Figs. 7 & 8) Stage 1 [T,-T,]: S,' is turned on, and Lr and Cr start resonating. When i, decreases from zero to negative peak and then increases towards zero and changes direction. i,, reaches Z, at T, and the antiparallel diode of S,' becomes on. Stage 2 [T,-T2]: S,' is turned off while S' is turned on with ZCS at T,. The current of D is directed to the auxiliary circuit. i,, decreases rapidly towards zero. Stage 3 [T2-T3]: i,, returns to zero at T2 and the antiparallel diode of S,' is turned off naturally. Lr and Cr continue resonating and the negative i,, is conducted by D,. i,, returns to zero and D, is turned off naturally a1 T3. Stage 4 [ T3-T4] : It is a freewheeling mode Stage 5 [T4-T5]: Before S' is turned on, S,' is turned on again. Lr and Cr start resonating. i,, decreases from negative zero to peak, then increases towards zero, and changes direction. When it reaches Z, at T,, the antiparallel diode of S,' becomes on. Stage 6 [T,-T,]: At T,, i, reaches I ,  and the current of S' 1s reduced to zero, so S' is turned off with ZCS. As i, keeps increasing, it flows through the antiparalle I diode of S'. Stage 7 [T6-T7]: At T,, i, falls to Z, and the antiparallel diode of S' stops conducting. Stage 8 [T,-T,]: At T7, vcr is discharged to zero and D starts to conduct. The current in D increases gradually. Stage 9 [T8-T9] It is a backward powering mode via D. , VCF i,, 2 s  V.9 vg V P  s2 s7 Fig. 5.  Equivalent circuit and key waveforms at motoring mode. 14 Fig. 6 .  Nine topological stages at motoring mode. Fig. 7. Equivalent circuit and key waveforms at regenerating mode. 0-7803-4503-7/98/$10.00 1998 IEEE 717 Fig. 8. Nine topological stages at regenerating mode. IV. SIMULATION AND EXPERIMENTAL RESULTS To verify the theoretical results, the 2Q-ZCT converter is PSpice-simulated and hardware prototyped. As shown in Fig. 9, the resonant components are selected as 10 pH and 0.1 yF, and the IGBT is adopted as those power devices. The PSpice-simulated waveforms for the 2Q-ZCT converter operating in both the motoring and regenerating modes are shown in Figs. 10 and 11, respectively. It can be found that they closely agree with those theoretical waveforms, especially all main and auxiliary switches (S, S' and Sa, Si) can always maintain ZCS operation. Moreover, in order to verify the simulation results, a 40 kHz, 500 W prototype of the proposed 2Q-ZCT converter has been constructed to drive a DC motor. From the experimental waveforms as shown in Figs. 12 and 13, they closely agree with those theoretical and simulation waveforms, especially the main and auxiliary switches can always maintain ZCS operation. 0-7803-4503-7/98/$10.00 1998 IEEE 718 Fig. 14 shows the turn-off switching transients (device voltage and device current) of S' of the proposed 2Q-ZCT converter operating in the regenerating mode. It can be found that the turn-off voltage across S' starts to rise when the current decays down to practically zero. Compared with those switching transients of the conventional PWM converter as shown in Fig. 15, it can be seen that the IGBT turn-off switching loss due to voltage-current overlapping can be alleviated. Fig. 9. Experimental 2Q-ZCT converter. Fig. 10. PSpice simulation at motoring mode Fig. 11. PSpice simulation at regenerating mode. Fig. 12. Measured waveforms at motoring mode: (6,,=O.7);vv (5OV/div); i,, (10Ndiv); vga, vg (SV/div). . y - - .................... .............................................. - ............................... Fig. 13. Measured waveforms at regenerating mode: (6,=O.3);vs (50V/div); i,, (5Ndiv); vg,', v i  (5Vldiv). :L 10.0v 2 20.0g ~ 1 2 . 8 y  lOOZ/ $3 RUI Y - - ............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  ......................... - - - . . . . . . . . . .  ............................. ......... - - - .......... - $ohage . ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . .  i .  .................... .......................... ..........urrent..l.........i.........i........ ' ............................................... - i - - A Fig. 14. Turn-off switching transients of the main IGBT using ZCT. 0-7803-4503-7/98/$10.00 1998 IEEE 719 Y - - - . . . . . . . . .  : .  . . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . - - - . . . . . . . . . / . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  - - V. CONCLUSION . . . . . . . . . 1 . . . . . . . . .  . .  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  - - - - - L A A novel 2Q-ZCT converter for DC motor drives has been presented. It possesses the definite advantages that all main and auxiliary switches can achieve ZCS while the corresponding device voltage and current stresses are kept minimum. Moreover, the proposed converter provides reduced switching losses and stresses, minimum voltage and current stresses, minimum circulating energy, simple circuit topology, low cost and improved switching characteristics - leading to achieve high power density and high efficiency. Other key features are the use of the same resonant tank for both forward and backward power flows and the full utilization of all built-in diodes of the power devices, thus minimizing the overall hardware count and cost. Both PSpice simulation and experimental measurement have verified the validity of the proposed converter. The proposed 2Q-ZCT technique can readily be extended to other types of converters. VI. ACKNOWLEDGMENT This work was supported and funded in part by the Committee on Research and Conference Grants in the University o f  Hong Kong, and the Hong Kong Research Grants Council. VII. REFERENCES D. Maksimovic and S. Cuk, “Constant-fi-equency control of quasi-resonant converters,” IEEE Trans. Power Electronics, vol. 6, 1991, pp. 141-150. G. Hua, C.S. Leu and F.C. Lee, “Novel zero-voltage- transition PWM converters,” In Proceedings of VPECSeminur, 1991, pp. 81-88. C.C. Chan and K.T. Chau, “A new zero-voltage- switching DCDC boost converter,” IEEE Trans. Aerospace & Electronic Systems, vol. 29, 1993, pp. J.G. Cho, J. W. Baek, G.H. Rim and I. Kang, “Novel zero voltage transition PWM multi-phase converters,” In Proceedings of IEEE APEC, 1996, H. Mao, F.C.Y. Lee, X. Zhou, H. Dai, M. Cosan and D. Boroyevich, “Improved zero-current transition converters for high power applications,” IEEE Truns. Industry Applications, vol. 33, 110.5, 1997, pp. 1220- 123 1. K.T. Chau, T.W. Ching and C.C. Chan, “Constant- frequency multi-resonant converter-fed DC motor drives,” In Proceedings ofIECON, 1996, pp. 78-83. K.T. Chau, T.W. Ching, C.C. Chan and T.W. Chan, “A Novel Soft-Switching Two-Quadrant Converter for DC Motor Drives,” In Proceedings of IECON, 125-134. pp. 500-506. 1997, pp. 517-522. 0-7803-4503-7/98/$10.00 1998 IEEE 720 

A novel two-quadrant zero-current transition converter for dc motor drives

A new zero-voltage-transition (ZVT) two-quadrant (2Q) converter for DC motor drives is presented. It possesses the definite advantage that both main switches and diodes can operate with zero-voltage switching in both motoring and regenerating modes, while both of these switches are subjected only to unity voltage and current stresses, namely the same as their PWM counterpart. This converter is particularly useful for DC traction systems in which both motoring and regenerative braking are desired to have high efficiency. The corresponding theoretical analysis and its high-efficiency performance are verified by both simulation and experimental results.link_to_subscribed_fulltex

A new two-quadrant zero-voltage transition converter for DC motor drives

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A novel two-quadrant zero-current transition converter for dc motor drives

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