IEEE Transactions on Industrial Electronics

Volume 49, Number 4, August 2002 Access to the journal on IEEE XPLORE IE Transactions Home Page

Special section on Multilevel Inverters

49.4.1	J. Rodriguez, "Guest editorial," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 722- 723, August 2002. Abstract Link Full Text Abstract: Not Available
49.4.2	J. Rodriguez, Jih-Sheng Lai, Fang Zheng Peng, "Multilevel inverters: a survey of topologies, controls, and applications," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 724- 738, August 2002. Abstract Link Full Text Abstract: Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.
49.4.3	A. von Jouanne, S. Dai, H. Zhang, "A multilevel inverter approach providing DC-link balancing, ride-through enhancement, and common-mode voltage elimination," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 739- 745, August 2002. Abstract Link Full Text Abstract: This paper presents a simple control method for balancing the DC-link voltage of three-level neutral-point-clamped inverters, while providing enhanced ride-through and common-mode voltage (CMV) elimination. The method uses DC-DC power converter technology on the DC link for balancing and ride-through enhancement, and a modified pulsewidth-modulation switching algorithm for CMV elimination. Simulation and experimental results are supplied to confirm the validity of the proposed method, which includes full digital signal processor control.
49.4.4	K.A. Corzine, J. Yuen, J.R. Baker, "Analysis of a four-level DC/DC buck converter," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 746- 751, August 2002. Abstract Link Full Text Abstract: In this paper, a four-level DC/DC buck power converter is introduced. The primary application for this converter is to regulate the center capacitor voltage in a four-level inverter system. The steady-state and average-value models for the proposed converter are developed and compared in simulation. The converter was constructed in the laboratory and verified on a four-level motor drive system. It was shown that the four-level DC/DC converter provides capacitor voltage balancing and allows higher output voltage utilization from the inverter.
49.4.5	M. Juneesoni, P. Tenca, "Diode-clamped multilevel converters: a practicable way to balance DC-link voltages," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 752- 765, August 2002. Abstract Link Full Text Abstract: The converter topologies identified as diode-clamped multilevel (DCM) or, equivalently, as multipoint clamped (MPC), are rarely used in industrial applications, owing to some serious drawbacks involving mainly the stacked bank of capacitors that constitutes their multilevel DC link. The balance of the capacitor voltages is not possible in all operating conditions when the MPC converter possesses a passive front end. On the other hand, in AC/DC/AC power conversion, the back-to-back connection of a multilevel rectifier with a multilevel inverter allows the balance of the DC-link capacitor voltages and, at the same time, it offers the power-factor-correction capability at the mains AC input. An effective balancing strategy suitable for MPC conversion systems with any number of DC-link capacitors is presented here. The strategy has been carefully studied to optimize the converter efficiency. The simulation results related to a high-power conversion system (up to 10 MW) characterized by four intermediate DC-link capacitors are shown.
49.4.6	K.A. Corzine, J.R. Baker, "Reduced-parts-count multilevel rectifiers," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 766- 774, August 2002. Abstract Link Full Text Abstract: Multilevel power converters have gained much attention in recent years due to their high power quality, low switching losses, and high-voltage capability. These advantages make the multilevel converter a candidate topology for the next generation of naval ship prolusion systems. The primary disadvantage of these systems is the large number of semiconductors involved. This paper presents a reduced-parts-count rectifier which is well suited for naval rectifier applications where bidirectional power flow is not required. The proposed converter is analyzed and experimentally verified on an 18-kW four-level rectifier/inverter system.
49.4.7	T. Ishida, K. Matsuse, T. Miyamoto, K. Sasagawa, L. Huang, "Fundamental characteristics of five-level double converters with adjustable dc voltages for induction motor drives," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 775- 782, August 2002. Abstract Link Full Text Abstract: In this paper, two kinds of control strategies for a three-phase five-level double converter are described on the assumption that the converter is applied to an induction motor drive system. The purposes of the proposed control strategies are to correct voltage imbalance of the DC-bus capacitors, to keep the input power factor at near unity, and to achieve an adjustable-speed drive. Characteristics of the converter operated by each of the two control strategies are examined and the validity is verified by experiments using a 3.7-kW induction motor.
49.4.8	Y. Kawabata, M. Nasu, T. Nomoto, E.C. Ejiogu, T. Kawabata, "High-efficiency and low acoustic noise drive system using open-winding AC motor and two space-vector-modulated inverters," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 783- 789, August 2002. Abstract Link Full Text Abstract: The combining of the outputs of two inverters using interphase reactors is a widely used method for supplying large AC drives rated at more than several thousands kilowatts. Certain drawbacks are associated with this method, such as high acoustic noise and high losses due to the interphase reactors. To overcome these problems, the authors propose a new high-efficiency drive system using an open-winding motor and two space-vector-modulated inverters. This configuration consists of a three-level inverter with switching at once every cycle and a two-level inverter of about 1-kHz switching frequency, connected, respectively, to the opposite terminals of the open-winding AC motor. With the proposed configuration, good current waveforms, high efficiency, and low acoustic noise can be obtained.
49.4.9	Xinbo Ruan, Dayu Xu, Linquan Zhou, Bin Li, Qianhong Chen, "Zero-voltage-switching PWM three-level converter with two clamping diodes," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 790- 799, August 2002. Abstract Link Full Text Abstract: A zero-voltage-switching pulsewidth-modulation three-level (ZVS PWM TL) converter realizes ZVS for the switches with the use of the leakage inductance (or external resonant inductance) and the output capacitors of the switches, however, the rectifier diodes suffer from reverse recovery which results in oscillation and voltage spike. In order to solve this problem, this paper proposes a novel ZVS PWM TL converter, which introduces two clamping diodes to the basic TL converter to eliminate the oscillation and clamp the rectified voltage to the reflected input voltage; in the meanwhile, all the switches keep to realize ZVS. Furthermore, the proposed ZVS PWM TL converter can be simplified by removing the two freewheeling diodes. The operation principle of the novel converter and the simplified converter are analyzed and are verified by a prototype converter. The experimental results are also included in this paper.
49.4.10	Xiaoming Yuan, I. Barbi, "Zero-voltage switching for the neutral-point-clamped (NPC) inverter," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 800- 808, August 2002. Abstract Link Full Text Abstract: This paper proposes a transformer-assisted pulsewidth-modulation zero-voltage-switching neutral-point-clamped (NPC) inverter. With the assistance of a transformer-assisted small-rating lossless auxiliary circuit, the main switches work with zero-voltage switching without suffering from any voltage/current spikes, under simple explicit control. The technique allows for higher operating frequency and better device utilization of the NPC inverter. Operation, analysis, design, as well as testing results from a 7-kW prototype are presented in detail.
49.4.11	M.F. Escalante, J.-C. Vannier, A. Arzande, "Flying capacitor multilevel inverters and DTC motor drive applications," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 809- 815, August 2002. Abstract Link Full Text Abstract: In this paper, the requirements imposed by a direct torque control (DTC) strategy on multilevel inverters are analyzed. A control strategy is proposed in order to fulfill those requirements when a flying-capacitor multilevel inverter is used. Simulation and practical results will confirm the performance of the proposed strategy when using the multilevel inverter to control an induction motor by the DTC principle. Also, the advantages of using a multilevel inverter with a DTC strategy are shown by simulation results.
49.4.12	H. Ertl, J.W. Kolar, F.C. Zach, "Analysis of a multilevel multicell switch-mode power amplifier employing the "flying-battery" concept," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 816- 823, August 2002. Abstract Link Full Text Abstract: This paper presents a novel switch-mode power amplifier based on a multicell multilevel circuit topology. The total output voltage of the system is formed by series connection of several switching cells having a low DC-link voltage. Therefore, the cells can be realized using modern low-voltage high-current power MOSFET devices and the DC link can easily be buffered by rechargeable batteries or "super" capacitors to achieve very high amplifier peak output power levels ("flying-battery" concept). The cells are operated in a phase-shifted interleaved pulsewidth-modulation mode, which, in connection with the low partial voltage of each cell, reduces the filtering effort at the output of the total amplifier to a large extent and, consequently, improves the dynamic system behavior. The paper describes the operating principle of the system, analyzes the fundamental relationships being relevant for the circuit design, and gives guidelines for the dimensioning of the control circuit. Furthermore, simulation results as well as results of measurements taken from a laboratory setup are presented.
49.4.13	A.J. Visser, J.H.R. Enslin, H. de T Mouton, "Transformerless series sag compensation with a cascaded multilevel inverter," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 824- 831, August 2002. Abstract Link Full Text Abstract: The use of a cascaded multilevel inverter for transformerless sag/dip compensation is investigated. This topology is investigated as a cost-effective means for series sag compensation by eliminating the large injection transformer and output filter components that are used in conventional series injection devices. This prototype inverter is designed for sag compensation of a 250-kVA load. In this design, cost effectiveness plays a major role in the selection of the energy storage and the switching components. Control schemes are discussed for series sag compensation with this multilevel inverter. New control methods for sag compensation and injection are also introduced. A prototype is developed and the control schemes of this sag compensator are successfully verified in the practical results and show successful compensation for sags for different types of loads. The performance of this compensator makes it promising for future power rating upgrade and industrialization.
49.4.14	R. Teodorescu, F. Blaabjerg, J.K. Pedersen, E. Cengelci, P.N. Enjeti, "Multilevel inverter by cascading industrial VSI," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 832- 838, August 2002. Abstract Link Full Text Abstract: In this paper, the modularity concept applied to medium-voltage adjustable speed drives is addressed. First, the single-phase cascaded voltage-source inverter that uses series connection of insulated gate bipolar transistor (IGBT) H-bridge modules with isolated DC buses is presented. Next, a novel three-phase cascaded voltage-source inverter that uses three IGBT triphase inverter modules along with an output transformer to obtain a 3-p.u. multilevel output voltage is introduced. The system yields in high-quality multistep voltage with up to four levels and low dv/dt, balanced operation of the inverter modules, each supplying a third of the motor rated kVA. The concept of using cascaded inverters is further extended to a new modular motor-modular inverter system where the motor winding connections are reconnected into several three-phase groups, either six-lead or 12-lead connection according to the voltage level, each powered by a standard triphase IGBT inverter module. Thus, a high fault tolerance is being achieved and the output transformer requirement is eliminated. A staggered space-vector modulation technique applicable to three-phase cascaded voltage-source inverter topologies is also demonstrated. Both computer simulations and experimental tests demonstrate the feasibility of the systems.
49.4.15	J. Rodriguez, L. Moran, J. Pontt, J.L. Hernandez, L. Silva, C. Silva, P. Lezana, "High-voltage multilevel converter with regeneration capability," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 839- 846, August 2002. Abstract Link Full Text Abstract: This paper presents a multilevel converter with regeneration capability. The converter uses several power cells connected in series, each working with reduced voltage and with an active front end at the line side. This paper presents the following: (1) the control method of each cell; (2) the use of phase-shifting techniques to reduce the current and voltage distortion; and (3) criteria to select the connection of the cells. The converter generates almost sinusoidal currents at the load and at the input and works with very high power factor.
49.4.16	B.P. McGrath, D.G. Holmes, "An analytical technique for the determination of spectral components of multilevel carrier-based PWM methods," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 847- 857, August 2002. Abstract Link Full Text Abstract: This paper presents an analytical approach for determining the spectral components of multilevel pulsewidth modulation (PWM) strategies, which avoids the problems of spectral leakage, roundoff, and subtle programming errors associated with the more usual approach of using discrete Fourier transforms of simulated switched waveforms. The approach uses a double Fourier integral formulation to analyze the inverter switched output, establishing the inner and outer integral limits of this formulation under conditions of natural sampling, regular sampling, and overmodulation. Closed-form and numerical integration solutions are presented for phase disposition PWM of a diode-clamped inverter to illustrate the technique, together with a comparison of theoretical and experimental spectral results for the naturally and asymmetric regularly sampled cases to confirm the validity of the approach.
49.4.17	B.P. McGrath, D.G. Holmes, "Multicarrier PWM strategies for multilevel inverters," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 858- 867, August 2002. Abstract Link Full Text Abstract: Analytical solutions of pulsewidth-modulation (PWM) strategies for multilevel inverters are used to identify that alternative phase opposition disposition PWM for diode-clamped inverters produces the same harmonic performance as phase-shifted carrier PWM for cascaded inverters, and hybrid PWM for hybrid inverters, when the carrier frequencies are set to achieve the same number of inverter switch transitions over each fundamental cycle. Using this understanding, a PWM method is then developed for cascaded and hybrid inverters to achieve the same harmonic gains as phase disposition PWM achieves for diode-clamped inverters. Theoretical and experimental results are presented in the paper.
49.4.18	M. Hashad, J. Iwaszkiewicz, "A novel orthogonal-vectors-based topology of multilevel inverters," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 868- 874, August 2002. Abstract Link Full Text Abstract: This paper presents a novel proposal of developing converter output voltage waveforms and novel converter topologies. The main idea is based on the assumption that the total converter output space vector is composed of two orthogonal space vectors. Two basic proposals are discussed. The first one is related to a converter built of two standard inverters: a main inverter (MI) and an auxiliary one. The converter output voltage space vector is composed of two orthogonal vectors generated by the respective inverters. The total power of the auxiliary inverter does not exceed 20% of the MI power. Thanks to the presented control method, the harmonic content of the output voltage is significantly reduced. The second proposal is related to a novel converter topology denoted as OVT-IHC. The converter is built of one two-level inverter and three isolated H-bridge circuit units. The structure and its performance are also discussed in the paper. The converter in question is able to generate 133 different output space vectors and permits achievement of a stepped adjustment of the RMS output voltage. Both topologies presented in the paper indicate some characteristics and advantages of multilevel inverters. The converters acting on the basis of the orthogonal vectors idea possess promising properties and are suitable to applications in medium-power converters. The paper presents main features and contribution to the theory.
49.4.19	S. Sirisukprasert, Jih-Sheng Lai, Tian-Hua Liu, "Optimum harmonic reduction with a wide range of modulation indexes for multilevel converters," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 875- 881, August 2002. Abstract Link Full Text Abstract: This paper proposes a novel modulation technique to be applied to multilevel voltage-source converters suitable for high-voltage power supplies and flexible AC transmission system devices. The proposed technique can generate output stepped waveforms with a wide range of modulation indexes and minimized total voltage harmonic distortion. The main power devices switch only once per cycle, as is suitable for high-power applications. In addition to meeting the minimum turn-on and turn-off time requirements for high-power semiconductor switches, the proposed technique excludes from the synthesized waveform any pulses that are either too narrow or too wide. By using a systematic method, only the polarities and the number of levels need to be determined for different modulation levels. To verify the theory and the simulation results, a cascaded converter-based hardware prototype, including an 8-b microcontroller as well as modularized power stage and gate driver circuits, is implemented. Experimental results indicate that the proposed technique is effective for the reduction of harmonics in multilevel converters, and both the theoretical and simulation results are well validated.
49.4.20	J. Rodriguez, L. Moran, P. Correa, C. Silva, "A vector control technique for medium-voltage multilevel inverters," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 882- 888, August 2002. Abstract Link Full Text Abstract: This paper presents a switching strategy for multilevel cascade inverters, based on the space-vector theory. The proposed switching strategy generates a voltage vector with very low harmonic distortion and reduced switching frequency. This new control method is an attractive alternative to the classic multilevel pulsewidth modulation techniques considering the following aspects: (1) voltage and current total harmonic distortion; (2) range of linear operation; and (3) number of commutations. Drive Control
49.4.21	J. Rodriguez Arribas, C.M. Vega Gonzalez, "Optimal vector control of pumping and ventilation induction motor drives," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 889- 895, August 2002. Abstract Link Full Text Abstract: An original speed control for centrifugal pump and fan drives with squirrel-cage induction motors that seeks the maximum energy saving is proposed. The strategy is based on minimizing the motor and converter losses at the steady state and minimizing the transient time that the motor employs in passing from one steady stage to another. The shortest transient time is achieved by applying the Pontriagin's maximum principle taking into account the parabolic load torque-speed dependence of these types of drives. Short-time transients, which take the motor from one point of maximum efficiency to another, contribute to reduce losses and to extend the application of the energy-saving concept to the drives with frequent changes of load torque and speed.
49.4.22	T. Su, M. Ishida, T. Hori, "Suppression control method for torque vibration of three-phase HB-type stepping motor utilizing feedforward control," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 896- 904, August 2002. Abstract Link Full Text Abstract: This paper proposes a method to reduce the vibration of the three-phase HB-type stepping motor with cogging torque by the feedforward compensation control. The compensation signal to suppress the vibration of the motor frame is obtained by the repetitive controller installing an online Fourier transformer and utilizing an acceleration sensor attached to the motor frame or an acoustic sensor such as a microphone placed close to the frame. The sensor is used only for the acquisition of the feedforward compensation data. The feedforward compensation signal at an arbitrary operating point is derived from the amplitude and phase data of the frequency components and the operating point data. Compensation data obtained by the repetitive controller is applied to the operating point changed by reference frequency and load condition in steady state. The compensation signal for the new operating point will be generated from compensation data utilizing polynomial equation approximation and linear interpolation method. The effectiveness of this proposed method is confirmed by the experimental results.
49.4.23	R.C. Luo, Long-Yeu Chung, "Stabilization for linear uncertain system with time latency," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 905- 910, August 2002. Abstract Link Full Text Abstract: Recently, various remote control systems through the public Internet have been broadly applied in factory automation, information appliance (IA), surgery, space exploration, the military, and also in our daily life. However, the time delay is unavoidable when the remote control systems through the Internet are distant from each other in the remote locations. Time delay usually causes control systems to become unstable or fail, even if the system is stable under no time delay. In this paper, stabilization for a class of linear uncertain systems with time latency is considered. The proposed control is based on the optimal control for its delay-free linear system with quadratic performance index. A Lyapunov functional theorem is used in the proof of our main result. A delay-dependent criterion is provided to guarantee asymptotic stabilizability for time-latency systems.
49.4.24	Hou-Tsan Lee, Li-Chen Fu, Hsin-Sain Huang, "Sensorless speed tracking of induction motor with unknown torque based on maximum power transfer," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 911- 924, August 2002. Abstract Link Full Text Abstract: In this paper, the authors first derive the maximum power transfer theorem for an induction motor. Then, a nonlinear indirect adaptive sensorless speed tracking controller for the motor with the maximum power transfer is proposed. In this controller, only the stator currents are assumed to be measurable. The rotor flux and speed observers are designed to relax the need of flux and speed measurement. In addition, the rotor resistance estimator is also designed to cope with the problem of the fluctuation of rotor resistance with temperature. Stability analysis based on Lyapunov theory is also performed to guarantee that the controller design here is stable. Finally, the computer simulations and experiments are conducted to demonstrate the satisfactory tracking performance of the authors' design subject to maximum power transfer. Power Electronics
49.4.25	Byungcho Choi, Jaeyeol Kim, B.H. Cho, Seungwon Choi, C.M. Wildrick, "Designing control loop for DC-to-DC converters loaded with unknown AC dynamics," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 925- 932, August 2002. Abstract Link Full Text Abstract: This paper presents a method for designing the control loop for DC-to-DC power converters when uncertainties exist in the AC characteristics of the converter's load. In the proposed method, a converter is initially considered as a stand-alone module feeding a current sink load and the control loop of the converter is then designed in a way that maximizes the robustness of the converter's closed-loop performance against the unknown AC dynamics of a potential load. As a result, the proposed control design method can provide the predictable closed-loop performance for a converter when it is loaded with an actual load whose AC characteristics are unknown in advance. Emerging Technology
49.4.26	R.C. Luo, Long-Yeu Chung, Chang-Hua Lien, "A novel symmetric cryptography based on the hybrid Haar wavelets encoder and chaotic masking scheme," IEEE Trans. on Industrial Electronics, vol. 49, no. 4, pp. 933- 944, August 2002. Abstract Link Full Text Abstract: In this scheme, the authors use the seven chaotic parameters (a,/spl beta/,a,b,x/sub 0/,y/sub 0/,z/sub 0/) and the dimension of Haar wavelet encoder matrix H/sub n/, the combining form of H/sub n/ with subwavelet basis {h/sub 0/,h/sub 1/,...,h/sub n-1/}, the prespecified time span t/sub s/, as well as the coefficients a/sub i/,i=1,...,n, and the prime number k of the collision-free one-way function to serve as the "encryption keys." The security property of the proposed cryptosystem results from two main parts: first, the high sensitivity of synchronization versus parameter or initial condition with small variation. It is sensitive enough to make the state trajectories separate from each other at an exponential rate. The second part depends on the Haar wavelets encoder H/sub n/ with its various combining form from the subwavelets basis {h/sub 0/,h/sub 1/,...,h/sub n-1/}; it is composed the same way as the lottery. Furthermore, due to the collision-free one-way function, the chaotic behavior control parameters are always different. Therefore, the system can be secured as long as the first chaotic parameters are kept secret. Moreover, the transmitting error-detection function of the proposed cryptosystem is also addressed.