This paper presents a newly developed an 80MVA GCT STATCOM for the Kanzaki substation of the Kansai Electric Power Co., Inc. The commercial operation was started in June, 2004. The main purpose of the STATCOM is to maintain voltage during single circuit connection of source to the substation resulting from an AC system fault in order not to break down load system of the substation. The developed STATCOM has three distinctive features: (1) a high-efficient, compact and AC filter-less system using multistage three-level GCT converter and customized harmonics reduction PWM; (2) a coordinated voltage regulator with tap control of main transformers; and (3) a continuous operation from a single phase-ground fault through reclosing of the faulted circuit by limiter adjustments of the reactive current reference. This paper describes characteristics of the coordinated voltage control in the substation, and shows performance of the continuous operation during AC system faults using data of commercial operations and the simulation results.

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In this paper, the technical stream on a high efficiency and high frequency chopper for the automotive industry, new energy and energy conservation technology field is surveyed. QRAS (Quasi-resonant Regenerating Active Snubber) and SAZZ (Snubber Assisted Zero Voltage and Zero Current Transition) topologies aimed for the electric vehicle (EV) drive application are proposed. 25kHz-8kW QRAS, 100kHz-8kW SAZZ choppers and 50kHz-25kW bilateral SAZZ-1 chopper are constructed and tested under rating conditions. It is verified that SAZZ topology retains high efficiency even at the increased operating frequency of 100kHz. It is shown that high efficiency can be realized at high operating frequency even in high power converters by QRAS and newly proposed SAZZ soft switching topologies.

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The buck-boost power factor corrected (PFC) converter has the wide range of the dc output voltage. A new non-isolated three-phase hard-switching and a soft-switching buck-boost PFC converter are proposed. Removing the three-phase transformer from the converters makes their size more compact and their costs lower. In addition, the new control method based on the PWM technique is proposed in this paper to achieve the high power factor. Complete soft-switching is also achieved under the discontinuous current mode (DCM) operation.

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Technology fusion between motor design and control can produce new applications. This paper introduces a saliency-based sensorless drive of adequate designed IPM motor for a specific application in a robot vehicle. The motor is deliberately designed to meet the requirements of robot application and lend itself better for saliency based sensorless control. The speed and position of multiple wheel-motors are synchronously controlled by the drive amplifiers and a single motion controller over the speed range from zero to maximum speed for the robot vehicle application. Finally, two types of robot vehicles, one being a two-wheeled differential drive and the other being an omni directional drive, are developed to transport objects and human. This paper mainly focuses on the concept of motor design and its control. Some analysis and test data are given in this paper.

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A novel zero current soft-switching (ZCS)-PWM cell-assisted half-bridge DC-DC converter topology with a high frequency link is proposed in this paper. The newly-proposed DC-DC converter consists of a PWM-controlled single-ended half-bridge high frequency (HF) inverter and a current doubler rectifier linked with a HF transformer. In order to attain the wide range of ZCS-PWM operation in the primary-side HF inverter, an active edge resonant snubber cell composed by a switched capacitor and a lossless inductor is adopted in the half-bridge leg, providing ZCS commutation for a wide range of output power. The operation characteristics of the DC-DC converter proposed here are described, and its feasibility data is demonstrated and evaluated with simulation and experimental results.

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According to grid codes issued by utilities, tripping of wind turbines following grid faults is not allowed. Besides, to provide voltage support to the grid mandatory reactive current supply is necessary. To enable wind turbines ride-through low voltage periods special protection measures have to be implemented. In this paper the behavior of DFIG based wind turbines during grid faults is discussed and elucidated using simulation results. It is shown that with properly designed crowbar and DC-link chopper even zero voltage ride-through is possible.

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Although a hysteresis current control is a simple and a reliable modulation technique in switching control systems, its spectral contents around switching sideband are not distributed broadly. Random Pulse Width Modulation (RPWM) technique is an effective scheme which distributes the spectral contents of a load current and can reduce acoustic noise and mechanical vibrations of an inverter-fed motor drive. This paper presents a Random-Band Hysteresis Current Control (RBHCC) technique with bipolar and unipolar modulations. Mathematical analysis and simulation results show the RBHCC with the unipolar modulation has no significant effect on distributing the spectral contents of the load current compared to the bipolar modulation technique. Finally, the effect of the random-band hysteresis current control is analysed to determine the best hysteresis band height variation for the bipolar modulation.

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This paper presents three control strategies for maximum peak power tracking (MPPT) based algorithm to optimize the captured wind energy. The first control strategy uses a predetermined peak torque-speed characteristic as a system command. The second strategy employs perturbation and observation (P&O) technique to determine the optimal operating points based on the slope of the power-rotational speed curve. The calculated torque references are used in conjunction with the fuzzy logic control in the third control strategy to derive the torque command. Stall regulation is employed to limit the output power of the wind generator. The MPPT- based algorithm with all three strategies was implemented on a low cost digital signal controller and was tested with a system consisting of a wind turbine controller and a wind turbine simulator. The experimental results confirm that all strategies can attain the maximum power for any wind speeds below-rated speed but with different control performances in terms of power fluctuation, rotational speed fluctuation and tracking time. The stall regulation was very effective in limiting the output power of the system at the wind speeds above-rated speed.

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This paper presents a converter topology used to interface a bank of Supercapacitors (SC) to a stiff DC-Link, like the one constituted by a typical battery. Main feature of the proposed converter is the reduced ratings of the power electronics switches compared to standard topologies. The capabilities of the proposed system in terms of energy storage and controllability of the power flow in and out the SC bank are identical to those of a conventional system, making the solution very attractive in terms of cost and efficiency in a wide number of applications. Theoretical principles underlying the converter operation are given, along with an experimental evaluation of the proposed solution, showing its practical feasibility.

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High power isolated DC/DC converters have been extensively used in various applications. Significant research efforts have been devoted to increase the operating efficiency and power density of the converter. Soft switching full bridge converter has been proposed to meet these goals by establishing zero voltage switching condition across the power transistors. However, a significant inductor is required to facilitate the resonance condition, and results in increased loss and reduced power density of the converter.
In this article, a full bridge converter with limited soft switching capability ^(1)-(3) and a coaxially-wound transformer are presented to improve the power density. With the coaxial winding structure, the coupling coefficient the transformer will be much higher than conventional transformer, and result in small leakage inductance. The duty cycle loss of the converter is also reduced thanks to the low leakage inductance of the coaxial transformer.
Various coaxial structures are presented in this paper Detailed simulations using Ansoft are conducted to observe their magnetic characteristics. These coaxial transformers are constructed in the laboratory and tested with the full bridge converter under soft-switching conditions to evaluate the performance of the entire system.

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More and more utility companies provide dual power feeders as a premier service of high power quality and reliability. To take advantage of this, the solid-state transfer switch (STS) is adopted to protect the sensitive load against the voltage sag. However, the fast transfer process may cause in-rush current on the load-side transformer due to the resulting DC-offset in its magnetic flux as the load-transfer is completed. The in-rush current can reach 2∼6 p.u. and it may trigger the over-current protections on the power feeder. This paper develops a flux estimation scheme and a thyristor gating scheme based on the impulse commutation bridge STS (ICBSTS) to minimize the DC-offset on the magnetic flux. By sensing the line voltages of both feeders, the flux estimator can predict the peak transient flux linkage at the moment of load-transfer and evaluate a suitable moment for the transfer to minimize the in-rush current. Laboratory test results are presented to validate the performance of the proposed system.

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This paper presents an integrated framework for modelling inverter performance and evaluating power devices in hybrid electric vehicle drives. Based in MATLAB/Simulink, it uses a novel method of decoupling the device and inverter simulation to maintain high accuracy of power losses and devices temperatures, and achieve faster than real time inverter simulation. An illustration is given for a full hybrid vehicle for different driving cycles. Device models are included for silicon carbide Schottky diodes as well as silicon IGBTs and PIN diodes. Evaluation of the new material devices is performed, to estimate the potential performance gains achievable. The simulation framework offers the potential to rapidly improve the inverter and powertrain design process, and to evaluate device selection quickly.

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High frequency (HF) transformer isolated DC-DC converter is part of a fuel cell inverter system for utility interface, required to translate the level of low fuel cell stack voltage to meet the peak utility line voltage and provides isolation between inverter and utility line. This paper presents a comparison of various soft-switched HF transformer isolated DC-DC converters for fuel-cell to utility interface application. It is shown that due to wide variation in fuel cell voltage with load variation, none of the voltage-fed converters can maintain ZVS for the complete operating range. Active clamped two-inductor current-fed converter is able to maintain ZVS for wide load and fuel cell stack voltage variations and is suitable for the present application. Analytical, simulation and experimental results are presented to evaluate the performance of the current-fed converter.

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This paper presents a new non-insulated three-level DC-DC boost converter with quadratic static gain. The quadratic feature is interesting for applications where a wide voltage range is necessary. The voltage across the switches is smaller then the output voltage. Since it is a current-source converter, its application in fuel cell energy conversion systems seems interesting, but other applications where the involved voltages are higher is very possible. Theoretical analysis for CCM of operation and experimental results are presented. A comparison between the two cascaded boost converter, the single switch quadratic boost converter and the proposed converter is made regarding commutated power. By experimental results is shown that the efficiency of the proposed converter is higher than two cascaded boost converters, even with less installed semiconductor power.

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Power density of power electronic converters has roughly doubled every 10 years since 1970. Behind this trajectory is the continuous advancement of power semiconductor devices, which has increased the converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts and passive components are major barriers for a continuation of this trend. To identify such technological barriers, this paper investigates the volume of the cooling system and passive components as a function of the switching frequency for power electronic converters and determines the switching frequency that minimizes the total volume. A power density limit of 28kW/dm³ at 300kHz is calculated for an isolated DC-DC converter, 44kW/dm³ at 820kHz for a three-phase unity power factor PWM rectifier, and 26kW/dm³ at 21kHz for a sparse matrix converter. For single-phase AC-DC conversion a general limit of 35kW/dm³ results from the DC link capacitor. These power density limits highlight the need to broaden the scope of power electronics research to include cooling systems, high frequency electromagnetics, interconnection and packaging technology, and multi-domain modelling and simulation to ensure further advancement along the power density trajectory.

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In this paper, a forced air-cooled, 400kHz, 10kW Vienna Rectifier with a power density of 8.5kW/liter is presented. To further improve the power density, the switching frequency is increased to reduce the EMI filter volume. A design for an 18.5kW/liter, 2.5MHz rectifier is proposed. By using today's technology, it is calculated that the maximum power density for a forced air-cooled and water-cooled rectifier is 20.8kW/liter and 24kW/liter respectively. To achieve 30kW/liter, improvements must be made in passive component material properties, reducing semiconductor losses and improving the cooling system.

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This paper proposes a control strategy which extends the Virtual-Flux Direct Power Control traditionally employed for the conventional two-level VSI to a three-level NPC inverter. This topology generates a higher number of output voltage levels, increasing the flexibility for selecting an appropriate voltage vector. The mid-point potential is controlled according to the direction of the mid-point current and the sign of the mid-point voltage deviation. The method is adapted to be used with an LCL output filter, where some undesirable characteristics, such as filter resonance, have to be compensated. Further investigation concerning the dependency of the mid-point voltage with the current phase-shift is given. Theoretical analysis is presented and the performance of the proposed method is verified by simulation.

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In the area or power electronics there is a general trend to higher power densities. In order to increase the power density the systems must be designed optimally concerning topology, semiconductor selection, etc. and the volume of the components must be decreased. The decreasing volume comes along with a reduced surface for cooling. Consequently, new cooling methods are required. In the paper an indirect air cooling system for magnetic devices which combines the transformer with a heat sink and a heat transfer component is presented. Moreover, an analytic approach for calculating the temperature distribution is derived and validated by measurements. Based on these equations a transformer with an indirect air cooling system is designed for a 10kW telecom power supply.

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This paper presents an elaborated mathematical analysis of the line loss minimum conditions of loop distribution systems. In order to achieve these conditions, the Unified Power Flow Controller (UPFC), a typical Flexible AC Transmission Systems (FACTS) device that is capable of instantaneous control of transmission and distribution power flow, is used. For minimizing the total line loss of the loop distribution system, the authors propose two control schemes, the Line Inductance Compensation control and the Line Voltage Compensation control. These control schemes can be applied for controlling the UPFC in the loop distribution system according to the line parameters. The effectiveness of the proposed control schemes has been verified experimentally using a laboratory prototype in a 200V, 6kVA system.

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We propose a new analysis method of harmonic wave components of magnetic fields in rotating machinery. Using the magnetic permeability obtained by the transient analysis of nonlinear magnetic field, the harmonic wave components of the magnetic field are individually calculated both in the spaces of rotor and stator under the boundary condition that the harmonic wave components obtained by the transient analysis are set on the sliding surface. The mode separation of magnetic field will contribute to the study of reducing the harmful harmonic wave components for the rotating machinery.

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We propose a new ground-to-train communication system using free-space optics between a train and the ground. In the proposed system, a cylindrical concave lens spreads the incoming beam from transmitter (Laser Diode: LD) horizontally to form a wide fan-shaped beam. The fan-shaped beam is projected to a train and the width of the projected beam is equal to the length of a typical bullet-train car. This transmitter with cylindrical concave lens and a receiver (Avalanche Photo Diode: APD) are installed at a train and the ground, and the horizontally spread beam is received continuously by corresponding receiver. The train can keep a communication link continuously to the ground thanks to this spread beam. We analyzed the performance of the proposed system by experiments. The experimental results show that a sufficient received Signal-to-Noise Ratio (SNR) can be obtained when a train is not moving; therefore, the signal can be received continuously even when the train is moving. Furthermore, in order to keep a continuous communication link even when the train vibrates or shifts vertically, the vertical spread angle of a laser beam is adjusted between 0.1 degrees and 0.5 degrees. These experimental results lead to the conclusion that this system is expected as a Giga-bit class high speed communication technology between the train and the ground.

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In this paper, we focus on a practical experiment concerning IP traffic engineering over Multi-Protocol Label Switching (MPLS), especially which features feedback control capabilities. We present control-theoretic analysis of the experimental results based on acquired knowledge of actual network behavior. Because stable automated control capabilities are key issues in IP traffic engineering, we model an IP traffic control system based on the resulting analysis. In addition, comparison between simulated network behavior and actual one shows this model to have a high degree of stability, with a high potential for application to real networks.

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This paper presents a method of estimating pole position of interior permanent magnet synchronous motors, IPMSMs. The proposed method estimates the pole position at low speeds and standstill by measuring only the DC link current of the inverter. The pole position is estimated by using the saliency of the IPMSMs. In order to detect the saliency, the three phase triangular carrier waves are used. The DC link current is measured at tops and bottoms of the carrier waves. Experimentation is performed to confirm the validity of the proposed method.

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This paper describes a new approach for high-performance image searching method named interlaced fast sequential matching and its application to document image processing for OA system. Conventional image retrieval method for a huge image such as Correlation Matching and SSDA have a shortcoming with their performance. Thus, we introduce the interlaced fast sequential matching in order to avoid the difficulty in the conventional methods. Generally speaking, image retrieval in many kind of documents continues to be one of the most common application for document prcessing. Therefore, if we can find an efficient method to retrieve any character objects without OCR process, the more efficient document management can be performed. We first discuss some essential issues to be considered in document processing with large document image. Experimental results by using the proposed method are also described. The good performance of the interlaced fast sequential matching approach is shown.

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This paper proposes a novel “Direct Space Vector PWM (Direct SVPWM)” strategy based on the direct AC/AC conversion approach for three-phase to three-phase matrix converters. This method allows the sine input and sine output waveforms as a major premise, and gives top priority to the improvement of the output control performance in motor drive applications, for instance, provides maximum riding comfort for an elevator, etc. Output voltage harmonics, switching losses, and common-mode voltage can be reduced across the entire voltage region. In addition, the switching count can be reduced even further by fully utilizing the output current detection value.
Direct space vectors are first defined, and the selection method of space vectors is described. Next, the PWM duty calculation technique is explained. Finally, the validity of the proposed method is proven from the comparison with the conventional virtual indirect method based on the experimental and analysis results.

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