IEEE Transactions on Industrial Electronics

Volume 52, Number 3, June 2005 Access to the journal on IEEE XPLORE IE Transactions Home Page

Special Section Papers on Modern Rectifiers - Part 3

52.3.1	C. Rech, J.R. Pinheiro, "Line current harmonics reduction in multipulse connection of asymmetrically loaded rectifiers," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 640- 652, June 2005. Abstract Link Full Text Abstract: This paper proposes a new arrangement for the multipulse connection of asymmetrically loaded six-pulse rectifiers. This arrangement is, therefore, particularly suitable for implementing the dc voltage sources of hybrid multilevel inverters in applications with active power transfer, such as medium-voltage adjustable-speed drives. A new design methodology is proposed to determine the phase shifts among the secondaries of the isolation transformer, even when the active power levels processed by each rectifier and their input and output impedances are different. A set of phase angles is obtained to minimize, and even to eliminate, undesired low-order harmonics of the input current, in particular, the 5th harmonic, because this harmonic component presents an amplitude considerably higher than the amplitude of the other harmonics. In consequence, the proposed design methodology increases the input power factor and reduces the input current total harmonic distortion. Simulation and experimental results are presented to demonstrate the feasibility of the proposed structure.
52.3.2	J. Dixon, L. Moran, "A clean four-quadrant sinusoidal power rectifier using multistage converters for subway applications," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 653- 661, June 2005. Abstract Link Full Text Abstract: A special 27-level four-quadrant rectifier for subway applications is analyzed. The arrangement uses only three H-bridges per phase, common dc bus, and independent input transformers for each H-bridge. The transformers allow galvanic isolation and power escalation to obtain high-quality voltage waveforms, with total harmonic distortion of less than 1%. Some advantages of this 27-level rectifier are: 1) only one of the three H-bridges, called the main converter, manages more than 80% of the total active power in each phase and 2) it switches at fundamental frequency, reducing the switching losses at a minimum value. The rectifier analyzed in this paper is a current-controlled voltage-source type, with a conventional feedback control loop. Some simulations in a rectifier substation, including power reversal at full load are displayed (750 Vdc, 1200 A). The rectifier shows the ability to produce clean ac and dc waveforms without any ripple, and fast reversal of power. Some experimental results with a small prototype, showing voltage and current waveforms, are finally displayed.
52.3.3	M. Glinka, R. Marquardt, "A new AC/AC multilevel converter family," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 662- 669, June 2005. Abstract Link Full Text Abstract: A new ac/ac modular multilevel converter (M/sup 2/LC) family will be introduced. The new concept stands out due to its modularity and superior control characteristics. The stringent modularity results in a very cost-efficient and versatile converter construction. This new M/sup 2/LC concept is well suited to a wide range of multiphase ac/ac converters. The basic working principle together with the static and dynamic behavior are explained in detail on a single-phase ac/ac converter enabling four-quadrant operation. It is demonstrated that this converter concept fulfils the demanding requirements for future ac-fed traction vehicles very well.
52.3.4	A. Dell'Aquila, M. Liserre, V.G. Monopoli, P. Rotondo, "An energy-based control for an n-H-bridges multilevel active rectifier," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 670- 678, June 2005. Abstract Link Full Text Abstract: This paper deals with the control of a multilevel n-H-bridges front-end rectifier. This topology allows n distinct dc buses to be fed by the same ac source offering a high loading flexibility suitable for traction applications as well as for industrial automation plants. However, this flexibility can lead the system to instability if the dc buses operate at different voltage levels and with unbalanced loads. Thus, linear controllers, designed on the basis of the small-signal linearization, are not effective any longer and stability can not be ensured as large-signal disturbances occur. The use of a passivity-based control (PBC) designed via energy considerations and without small-signal linearization properly fits stability problems related to this type of converter. The system has been split into n subsystems via energy considerations in order to achieve the separate control of each dc bus and its stability in case of load changes or disturbances generated by other buses. Then, a set of n passivity-based controllers (one for each subsystem) is adopted: the controllers are linked using dynamical parameters computed through energy balance equations. Hence, the system dc buses are independent and stable as experimental results demonstrate.
52.3.5	E. Sanchis, E. Maset, J.A. Carrasco, J.B. Ejea, A. Ferreres, E. Dede, V. Esteve, J. Jordan, R. Garcia-Gil, "Zero-current-switched three-phase SVM-controlled buck rectifier," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 679- 688, June 2005. Abstract Link Full Text Abstract: A zero-current-transition (ZCT) cell is analyzed and designed to be used with a three-phase pulsewidth-modulation buck rectifier. This rectifier was space-vector controlled and used unidirectional current switches. The proposed ZCT circuit is load independent and achieves a high noise and voltage stress reduction and provides ZCTs to almost all transitions of the rectifier's switches and to the additional auxiliary switches. Theoretical equations have been obtained for design purposes. The circuit is easy to design and the driving signals for the auxiliary switches are also easy to obtain, as demonstrated in this paper.
52.3.6	Chien-Ming Wang, "A novel ZCS-PWM power-factor preregulator with reduced conduction losses," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 689- 700, June 2005. Abstract Link Full Text Abstract: This paper proposes a new single-phase high-power-factor rectifier, which features regulation by conventional pulsewidth modulation (PWM), soft commutation, and instantaneous average line current control. A new zero-current-switching PWM (ZCS-PWM) auxiliary circuit is configured in the presented ZCS-PWM rectifier to perform ZCS in the active switches and zero-voltage switching in the passive switches. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZCS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path and the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Nine transition states for describing the behavior of the ZCS-PWM rectifier in one switching period are described. The PWM switch model is used to predict the system performance. A prototype rated at 1 kW, operating 50 kHz, with an input ac voltage of 220 V/sub rms/ and an output voltage 400 V/sub dc/ has been implemented in laboratory. An efficiency of 97.3% and power factor over 0.99 has been measured. Analysis, design, and the control circuitry are also presented in this paper.
52.3.7	M.M. Jovanovic, Y. Febg, "State-of-the-art, single-phase, active power-factor-correction techniques for high-power applications - an overview," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 701- 708, June 2005. Abstract Link Full Text Abstract: A review of high-performance, state-of-the-art, active power-factor-correction (PFC) techniques for high-power, single-phase applications is presented. The merits and limitations of several PFC techniques that are used in today's network-server and telecom power supplies to maximize their conversion efficiencies are discussed. These techniques include various zero-voltage-switching and zero-current-switching, active-snubber approaches employed to reduce reverse-recovery-related switching losses, as well as techniques for the minimization of the conduction losses. Finally, the effect of recent advancements in semiconductor technology, primarily silicon-carbide technology, on the performance and design considerations of PFC converters is discussed.
52.3.8	Huang-Jen Chiu, Li-Wei Lin, "A high-efficiency soft-switched AC/DC converter with current-doubler synchronous rectification," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 709- 718, June 2005. Abstract Link Full Text Abstract: An improved ac/dc converter based on asymmetrical half-bridge topology is proposed in this paper. To substantially enhance the efficiency for low-voltage/high-current output applications, a current-doubler synchronous rectifier is combined with a modified asymmetrical half-bridge converter that retains the inherent zero-voltage-switching property. The power losses in the secondary rectification stage and the primary switches can be significantly reduced. The proposed architecture exhibits extreme simplicity and lower cost while providing unity power factor, well-regulated output, and high power density. The detailed operating principles and design procedures for the proposed converter are described in this paper. Simulation and experimental results for a laboratory prototype are discussed to verify the feasibility.
52.3.9	P. Ide, F. Schafmeister, N. Frohleke, H. Grotstollen, "Enhanced control scheme for three-phase three-level rectifiers at partial load," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 719- 726, June 2005. Abstract Link Full Text Abstract: A prominent boost-type three-level topology (VIENNA Rectifier I), which proved to represent a cost-effective and highly efficient solution for switched-mode rectifiers is inspected toward its operation at discontinuous conduction mode (DCM). This mode of operation occurs not only at high input voltage in conjunction with low load currents but even at medium loading in the vicinity of mains voltage zero crossings. When this circuit is operated in DCM, additional measures are required for improved behavior to avoid conflicts with requirements on total harmonic distortion and regulations as well as safe operation in terms of voltage balancing and overvoltage protection. A detailed analysis of DCM and associated states is performed enabling determination and location of error voltages. Basic rules for the location of error voltages can be found. This leads to a novel optimized modulation and control scheme, facilitating designs without additional inductance. Selected simulation and measurement results prove the enhanced modulation scheme.
52.3.10	Guanghai Gong, M.L. Heldwein, U. Drofenik, J. Minibock, K. Mino, J.W. Kolar, "Comparative evaluation of three-phase high-power-factor AC-DC converter concepts for application in future More Electric Aircraft," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 727- 737, June 2005. Abstract Link Full Text Abstract: A passive 12-pulse rectifier system, a two-level, and a three-level active three-phase pulsewidth-modulation (PWM) rectifier system are analyzed for supplying the dc-voltage link of a 5-kW variable-speed hydraulic pump drive of an electro-hydrostatic actuator to be employed in future More Electric Aircraft. Weight, volume, and efficiency of the concepts are compared for an input phase voltage range of 98-132 V and an input frequency range of 400-800 Hz. The 12-pulse system shows advantages concerning volume, efficiency, and complexity but is characterized by a high system weight. Accordingly, the three-level PWM rectifier is identified as the most advantageous solution. Finally, a novel extension of the 12-pulse rectifier system by turn-off power semiconductors is proposed which allows a control of the output voltage and, therefore, eliminates the dependency on the mains and load condition which constitutes a main drawback of the passive concept.
52.3.11	J.R. Rodriguez, J. Pontt, C. Silva, E.P. Wiechmann, P.W. Hammond, F.W. Santucci, R. Alvarez, R. Musalem, S. Kouro, P. Lezana, "Large current rectifiers: State of the art and future trends," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 738- 746, June 2005. Abstract Link Full Text Abstract: This paper presents the different technologies used in the generation of large controlled currents, in the kiloamperes range. After a brief review of processes requiring large currents, the paper discusses the working principles of thyristor phase-controlled rectifiers commonly used in these applications. Chopper-rectifiers using high-current insulated gate bipolar transistors are introduced as an alternative being considered in recent projects. The pulsewidth-modulated current-source rectifier, currently used in medium-voltage motor drives, is also analyzed as a future alternative for rectification in industrial processes. In addition, this paper presents the most important requirements and specifications to be considered in the applications of these high-power units. A system comparison is developed between thyristor and chopper-rectifiers in terms of quality of control, harmonics, power factor, losses, and efficiency.
52.3.12	P. Ladoux, G. Postiglione, H. Foch, J. Nuns, "A comparative study of AC/DC converters for high-power DC arc furnace," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 747- 757, June 2005. Abstract Link Full Text Abstract: Today, dc arc furnaces are supplied by thyristor rectifiers. Because of the phase control strategy on the rectifiers, the arc voltage swings induce large reactive power variations on the power network and a static VAr compensator (SVC) or a static synchronous compensator (STATCOM) is always added to avoid flicker effect. In this paper, the authors present a new control strategy which suppresses the flicker effect and increases the furnace productivity. To supply the dc arc furnace, the ac/dc converter is based on diode rectifiers and choppers with a constant power control strategy. Consequently, the ac/dc converter can operate without a STATCOM or an SVC. To evaluate the gain in flicker and furnace productivity, simulations are done with Matlab software. These simulations take into account arc voltage measurements on a 100-MW dc arc furnace and allow for comparison of the different solutions.
52.3.13	J.C. Wiseman, Bin Wu, "Active damping control of a high-power PWM current-source rectifier for line-current THD reduction," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 758- 764, June 2005. Abstract Link Full Text Abstract: The use of active damping to reduce the total harmonic distortion (THD) of the line current for medium-voltage (2.3-7.2 kV) high-power pulsewidth-modulation (PWM) current-source rectifiers is investigated. The rectifier requires an LC filter connected at its input terminals, which constitutes an LC resonant mode. The lightly damped LC filter is prone to series and parallel resonances when tuned to a system harmonic either from the utility or from the PWM rectifier. These issues are traditionally addressed at the design stage by properly choosing the filter resonant frequency. This approach may result in a limited performance since the LC resonant frequency is a function of the power system impedance, which usually varies with power system operating conditions. In this paper, an active damping control method is proposed for the reduction in line current THD of high-power current-source rectifiers operating at a switching frequency of only 540 Hz. Two types of LC resonances are investigated: the parallel resonance excited by harmonic currents drawn by the rectifier and the series resonance caused by harmonic pollution in the source voltage. It is demonstrated through simulation and experiments that the proposed active damping control can effectively reduce the line-current THD caused by both parallel and series resonances.
52.3.14	R. Garcia-Gil, J.M. Espi, E.J. Dede, E. Sanchis-Kilders, "A bidirectional and isolated three-phase rectifier with soft-switching operation," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 765- 773, June 2005. Abstract Link Full Text Abstract: A bidirectional-power-flow three-phase rectifier with high-frequency isolation and all-digital control, based on the matrix converter topology, is analyzed in this paper. The selected topology consists of a bidirectional three-phase-to-single-phase reduced matrix converter with power-factor correction and a bidirectional active rectifier. The inclusion of the isolation transformer at the switching frequency permits the reduction of volume and weight. By synchronizing the commutation of both converters and adding a saturable inductor and a blocking capacitor it is possible to achieve soft commutation for most of the semiconductor elements. An all-digital control based on a digital-signal-processor and a field-programmable gate array was used to implement space-vector modulation and output current regulation. This power converter is intended to feed the low-energy correction magnet of a particle accelerator. Experimental results of a 1.5-kW 20-kHz prototype are presented to illustrate the performance of the proposed topology.
52.3.15	S. Rees, "New cascaded control system for current-source rectifiers," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 774- 784, June 2005. Abstract Link Full Text Abstract: A control method for current-source rectifiers (CSRs), which realizes substantially sinusoidal line currents, unity displacement power factor, and a dc-link current control with excellent dynamic properties is presented. CSRs are usually operated by pulsewidth-modulation (PWM) or space-vector-modulation techniques. However, due to the mains LC filter resonant circuits when using these modulation methods the system stability has to be investigated, resulting in restrictions on the minimum PWM frequency and the minimum size of the LC filter. Furthermore most known dc-link current control loops use dc-link inductors of considerable size. This limits the dynamic performance and, therefore, reduces the attainable efficiency of CSRs. To overcome these problems, a new cascaded dc-link current control system for CSRs is presented. Its inner capacitor voltage controller is based on a time-discrete modulation method, which realizes a fundamentally stable control of the mains LC filter resonant circuits, avoiding the mentioned restrictions. The system controlled by the superimposed dc-link current controller is linearized by a new approach, allowing excellent dynamic performance and, therefore, a comparatively small dc-link inductor to be used. The paper includes guidelines on how to design the mains filter components and the dc-link inductor. The feasibility of the presented cascaded controller is confirmed by measurements taken on a 60-kVA model current-source converter and different loads. Drive Control
52.3.16	A.A. Naassani, E. Monmasson, J.-P. Louis, "Synthesis of direct torque and rotor flux control algorithms by means of sliding-mode theory," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 785- 799, June 2005. Abstract Link Full Text Abstract: This paper is an attempt to synthesize the direct torque and rotor flux control (DTRFC) algorithms of induction motor using sliding-mode theory. The choice of the sliding-mode theory has been motivated by the presence of switches in the voltage-source inverter (VSI). Changes in the state of the switches cause the variation in the topology of the controlled system. In addition, this theory offers a mathematical process that allows rigorous procedures of analysis and synthesis. The developed voltage vector is generated by two methods: direct control of the VSI (hysteresis VSI control), and indirect control of the VSI using space-vector modulation. In addition, taking into account the complementarity of the advantages of each VSI control algorithm, the high dynamic performance of the direct control and the smoothness of the indirect control, the idea of the dynamic reconfiguration of DTRFC algorithms is proposed.
52.3.17	H. Nakai, H. Ohtani, E. Satoh, Y. Inaguma, "Development and testing of the torque control for the permanent-magnet synchronous motor," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 800- 806, June 2005. Abstract Link Full Text Abstract: Hybrid electrical vehicles and electrical vehicles are being actively developed. A hybrid electric vehicle motor design requires high efficiency, high power/weight ratio, and reliability from low rotor speed to high rotor speed. The permanent-magnet synchronous motor is used in order to fulfill these requirements. The purpose of this paper is to develop a permanent-magnet synchronous motor control method for all rotor speeds. This method increases the torque and the efficiency at high speed when compared to the ordinary current error feedback method. A method composed of two compensators is proposed to achieve this objective. One of the compensators controls the torque using the voltage phases. The other one is the ordinary current error feedback. Several correcting methods for the voltage phase compensator have been proposed for the compensator for many control demands. The validity of the proposed method was confirmed using simulation and experimental evaluations.
52.3.18	C. De Angelo, G. Bossio, J. Solsona, G.O. Garcia, M.I. Valla, "A rotor position and speed observer for permanent-magnet motors with nonsinusoidal EMF waveform," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 807- 813, June 2005. Abstract Link Full Text Abstract: A new nonlinear reduced-order observer to estimate the rotor speed and position for permanent-magnet motors, with arbitrary electromotive force (EMF) waveform, is presented. The proposed observer is suitable for the realization of a torque control with minimum torque ripple. In order to implement the observer, the EMF generated by the motor is first obtained experimentally offline. After that, it is approximated by a Fourier series in order to develop the model to be used in the online estimation. From the estimated EMF, rotor position and speed are calculated using the relationship between the EMF and the rotor variables. The proposal is validated with experimental results.
52.3.19	Y.X. Su, C.H. Zheng, B.Y. Duan, "Automatic disturbances rejection controller for precise motion control of permanent-magnet synchronous motors," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 814- 823, June 2005. Abstract Link Full Text Abstract: A highly robust automatic disturbances rejection controller (ADRC) is developed to implement high-precision motion control of permanent-magnet synchronous motors. The proposed ADRC consists of a tracking differentiator (TD) in the feedforward path, an extended state observer (ESO), and a nonlinear proportional derivative control in the feedback path. The TD solves the difficulties posed by low-order reference trajectories which are quantized at the sensor resolution, and the ESO provides the estimate of the unmeasured system's state and the real action of the unknown disturbances only based on a measurement output of the system. Simulations and experimental results show that the proposed ADRC achieves a better position response and is robust to parameter variation and load disturbance. Furthermore, the ADRC is designed directly in discrete time with a simple structure and fast computation, which make it widely applicable to all other types of derives.
52.3.20	V.T. Somasekhar, K. Gopakumar, M.R. Baiju, K.K. Mohapatra, L. Umanand, "A multilevel inverter system for an induction motor with open-end windings," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 824- 836, June 2005. Abstract Link Full Text Abstract: In this paper, a multilevel inverter system for an open-end winding induction motor drive is described. Multilevel inversion is achieved by feeding an open-end winding induction motor with two two-level inverters in cascade (equivalent to a three-level inverter) from one end and a single two-level inverter from the other end of the motor. The combined inverter system with open-end winding induction motor produces voltage space-vector locations identical to a six-level inverter. A total of 512 space-vector combinations are available in the proposed scheme, distributed over 91 space-vector locations. The proposed inverter drive scheme is capable of producing a multilevel pulsewidth-modulation (PWM) waveform for the phase voltage ranging from a two-level waveform to a six-level waveform depending on the modulation range. A space-vector PWM scheme for the proposed drive is implemented using a 1.5-kW induction motor with open-end winding structure.
52.3.21	Rong-Jong Wai, Kuo-Min Lin, "Robust decoupled control of direct field-oriented induction motor drive," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 837- 854, June 2005. Abstract Link Full Text Abstract: This paper focuses on the development of a decoupling mechanism and a speed control scheme based on total sliding-mode control (TSMC) theory for a direct rotor field-oriented (DRFO) induction motor (IM). First, a robust decoupling mechanism including an adaptive flux observer and a sliding-mode current estimator is investigated to decouple the complicated flux and torque dynamics of an IM. The acquired flux angle is utilized for the DRFO object such that the dynamic behavior of the IM is like that of a separately excited dc motor. However, the control performance of the IM is still influenced seriously by the system uncertainties including electrical and mechanical parameter variation, external load disturbance, nonideal field-oriented transient responses, and unmodeled dynamics in practical applications. In order to enhance the robustness of the DRFO IM drive for high-performance applications, a TSMC scheme is constructed without the reaching phase in conventional sliding-mode control (CSMC). The control strategy is derived in the sense of Lyapunov stability theorem such that the stable tracking performance can be ensured under the occurrence of system uncertainties. In addition, numerical simulations as well as experimental results are provided to validate the effectiveness of the developed methodologies in comparison with a model reference adaptive system flux observer and a CSMC system. Power Electronics
52.3.22	T. Bruckner, S. Bernet, H. Guldner, "The active NPC converter and its loss-balancing control," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 855- 868, June 2005. Abstract Link Full Text Abstract: The three-level neutral-point-clamped voltage-source converter (NPC VSC) is widely used in high-power medium-voltage applications. The unequal loss distribution among the semiconductors is one major disadvantage of this popular topology. This paper studies the loss distribution problem of the NPC VSC and proposes the active NPC VSC to overcome this drawback. The switch states and commutations of the converter are analyzed. A loss-balancing scheme is introduced, enabling a substantially increased output power and an improved performance at zero speed, compared to the conventional NPC VSC.
52.3.23	T. Senanayake, T. Ninomiya, "An improved topology of inductor-switching DC-DC converter," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 869- 878, June 2005. Abstract Link Full Text Abstract: An improved version of an inductor-switching fast-response dc-dc converter is presented that will provide the requirements and features of the new generation of microprocessor and digital systems. Lower output voltage, higher output current, and smaller output voltage ripple requirements have greatly increased the difficulty of the power supply design. To further increase the problem, power-saving "stop-clock" modes of the microprocessor has demanded faster and more stable transient response from the dc-dc converter. A novel method of inductor switching is applied to a dc-dc converter, and it provides the prominent features of current amplification and absorption during the heavy burden of load transients. The design and simulation of the concept is verified by experiment with a 12-V input and 3.3-V/30-A output converter.
52.3.24	Dae-Wook Kang, Byoung-Kuk Lee, Jae-Hyun Jeon, Tae-Jin Kim, Dong-Seok Hyun, "A symmetric carrier technique of CRPWM for voltage balance method of flying-capacitor multilevel inverter," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 879- 888, June 2005. Abstract Link Full Text Abstract: This paper presents a simple carrier symmetric method for the voltage balance of flying capacitors in flying-capacitor multilevel inverters. The carrier-redistribution pulsewidth-modulation (CRPWM) method was reported as a solution for the voltage balance but it has a drawback at the transition of voltage level. To achieve the voltage balance of flying capacitors, the utilization of each carrier must be balanced during a half-cycle of the switching period such as phase-shifted PWM. However, the CRPWM method causes the fluctuation of flying-capacitor voltages because the balanced utilization of carriers is not achieved. Moreover, it does not consider that the load current change has an influence on flying-capacitor voltages by assuming that the current flows into the load. Therefore, the charging and discharging quantities of flying-capacitor voltages do not become zero during the switching period. To overcome the drawbacks of CRPWM, it is modified by the technique where carriers of each band are disposed of symmetrically at every fundamental period. Firstly, the CRPWM method is reviewed and the theory on voltage balance of flying capacitors is analyzed. The proposed method is introduced and is verified through simulation and experimental results.
52.3.25	Jin-Ha Choi, Jung-Min Kwon, Jee-Hoon Jung, Bong-Hwan Kwon, "High-performance online UPS using three-leg-type converter," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 889- 897, June 2005. Abstract Link Full Text Abstract: A high-performance single-phase online uninterruptible power supply (UPS) is proposed. The UPS is composed of a three-leg-type converter which operates as a battery charger and an inverter. The first leg is controlled to charge the battery, and the third leg is controlled to make the output voltage. The common leg is controlled in line frequency. The charger and the inverter are controlled independently. The charger has the capability of power-factor correction while charging a battery. The inverter regulates output voltage and limits output current under an impulsive load. The three-leg-type converter reduces the number of switching devices. As a result, the system has less power loss and a low-cost structure. In the determination of the charger voltage, the nominal voltage is derived using the feedback linearization concept and then a perturbed voltage is determined for the reactive power control. The disturbance of input voltage is detected using a fast sensing technique of the input voltage. Experimental results obtained with a 3-VA prototype show a normal efficiency of over 87% and an input power factor of over 99%. Robotics and Vision
52.3.26	Meng Joo Er, Chang Deng, "Obstacle avoidance of a mobile robot using hybrid learning approach," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 898- 905, June 2005. Abstract Link Full Text Abstract: in this paper, a hybrid learning approach for obstacle avoidance of a mobile robot is presented. the key features of the approach are, firstly, innate hardwired behaviors which are used to bootstrap learning in the mobile robot system. a neuro-fuzzy controller is developed from a pre-wired or innate controller based on supervised learning in a simulation environment. the fuzzy inference system has been constructed based on the generalized dynamic fuzzy neural networks learning algorithm of Wu and Er, whereby structure and parameters identification are carried out automatically and simultaneously. Secondly, the neuro-fuzzy controller is capable of re-adapting in a new environment. After carrying out the learning phase on a simulated robot, the controller is implemented on a real robot. A reinforcement learning method based on the fuzzy actor-critic learning algorithm is employed so that the system can re-adapt to a new environment without human intervention. In this phase, the structure of the fuzzy inference system and the parameters of the antecedent parts of fuzzy rules are frozen, and reinforcement learning is applied to further tune the parameters in the consequent parts of the fuzzy rules. Through the hybrid learning approach, an efficient and compact neuro-fuzzy system is generated for obstacle avoidance of a mobile robot in the real world.
52.3.27	K.C. Tan, Y.J. Chen, K.K. Tan, T.H. Lee, "Task-oriented developmental learning for humanoid robots," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 906- 914, June 2005. Abstract Link Full Text Abstract: This paper presents a new approach of task-oriented developmental learning for humanoid robots. It is capable of setting up multiple tasks representation automatically using real-time experiences, thereby enabling a robot to handle various tasks concurrently without the need of predefining the tasks. In the approach, an evolvable partitioned tree structure is used for task representation knowledgebase that is partitioned into different task domains. The search/update of task knowledge is focused on a particular task branch, without considering the whole task knowledgebase that is often large and time consuming in the process. A prototype of the proposed task-oriented developmental learning is designed and implemented using a Khepera robot. Experimental results show that the robot can redirect itself to new tasks through interactions with the environment, and a learned task can be easily updated in order to meet varying specifications in the real world.
52.3.28	S. Takagi, N. Uchiyama, "Robust control system design for SCARA robots using adaptive pole placement," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 915- 921, June 2005. Abstract Link Full Text Abstract: SCARA robots generally have two revolute joints and one prismatic joint. One of the fundamental motions of the robots is horizontal transportation of a load by actuating the two revolute joints. Residual vibration of the prismatic joint generally occurs in the transportation, and it should be suppressed. In this paper, we propose an adaptive controller design for the transportation. The controlled object is modeled as a nonlinear double-input quadruple-output system with unknown mass of load. The controlled object is separated into two single-input double-output systems, which allows us to design an integral controller providing performance robustness with respect to estimation error of the mass. Experimental results demonstrate the effectiveness of the proposed method. Letters to the Editor
52.3.29	Kune-Shiang Tzeng, D.C. Tzeng, Jian-Shiang Chen, "An enhanced iterative learning control scheme using wavelet transform," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 922- 924, June 2005. Abstract Link Full Text Abstract: In this letter, an enhanced iterative learning control scheme with wavelet transform is presented. To improve its learning behavior, a wavelet transform is employed to extract the unlearnable dynamics from the measured feedback signal before it can be used to update the control profile.
52.3.30	Xiaoli Li, Xin Yao, "Multi-scale statistical process monitoring in machining," IEEE Trans. on Industrial Electronics, vol. 52, no. 3, pp. 924- 927, June 2005. Abstract Link Full Text Abstract: Most practical industrial process data contain contributions at multiple scales in time and frequency. Unfortunately, conventional statistical process control approaches often detect events at only one scale. This paper addresses a new method, called multiscale statistical process monitoring, for tool condition monitoring in a machining process, which integrates discrete wavelet transform (WT) and statistical process control. Firstly, discrete WT is applied to decompose the collected data from the manufacturing system into uncorrelated components. Next, the detection limits are formed for each decomposed component by using Shewhart control charts. A case study, i.e., tool condition monitoring in turning using an acoustic emission signal, demonstrates that the new method is able to detect abnormal events (serious tool wear or breakage) in the machining process.