This paper proposes a circuit technique that reduces losses cauased by reverse-recovery characteristics of the diode in converters. In high voltage, high power, Reverse recovery characteristics of the diode gives large stresses to switching devices. To solve the problem, we propose a circuit with active snubber between diode and switch. By controling di/dt rate of thr diode, the proposed technique reduces the losses and the stresses of switching devices.

This Paper presents a novel resonant switching Watkins-Johnson DC-DC converters. In the proposed converters, the basic steady-state analysis of the have been presented for the ZVS type Watkins-Johnson converter. From the results, it is shown that the output voltage of the converter is independant of load resistance, and is determined only by the switching frequency. Consequently, a design procedure is presented that minimizes voltage stress to the switch while maintaining ZVS for all loads.

A class-D zero voltage switching (called soft-switching) inverter with only one capacitor in parallel with both FET, along with an approximate analysis and experimental results, is introduced. The inverter offers both zero turn-on and zero turn-off switching losses, yielding high efficiency at high frequencies. In addition, soft switching reduces switching noise associated with the high frequency ringing at the swithching instants.

This paper propose zero voltage and zero current switching buck converter using a single switch. This converter is electrically equivalent to two basic buck converter in a cascade. Proposed converter is switching at high frequency and operate in high efficiency at wide load range due to resonant switching.

In this paper, we designed and fabricated a fast switching system for high power pulse. This system consists of a voltage conversion circuit, high voltage charging circuit, trigger circuit, and discharging circuit. Especially discharging line is designed by strip-line for low inductance and resistance. The experimental result is that current slew rate of the system is 6.67kA/86ns and this result is fully qualified for initiating EBW or EFI

In the industrial motor drive system, a shaft torsional vibration is often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of such a system. Recently, there are new methods which estimate unknown state variables by using a reduced order observer and feedback these state variables by using a pole placement design method. But there is a trade-off between the fast command following property and the attenuation of disturbances and vibrations in these design methods. In this paper, the vibration suppression control of a two-mass system using a reference model is proposed. Because of using a reference model, the proposed control satisfy the fast command following property and the attenuation of disturbances and vibrations. Control parameter can be changed to maintain high system performance in control using a reference model. Experimental results show the validity of the proposed state feedback control using a reference model, and this controller is compared with the state feedback controller.

For an analysis and simulation of the conducted EMI of switching converters, an accurate simulation model for MOSFET is needed. This paper presents a new modeling approach, which incorporates DC output characteristics and AC dynamics especially the parasitic capacitances. It uses Pspice ABM(Analog Behavioral Model) and the MOSFET parameters can be obtained from the Data sheet in the frequency range of interest for EMI analysis. The model verified with an experimental setup and the EMI for a test converter is analyzed with respect to the MOSFET switching waveforms.

The conducted differential mode (DM) EMI in a flyback converter are analyzed. Circuit modeling of passive components and PCB pattern for the EMI simulation are presented. Using the model, high frequency noise path is analyzed. The analyses are verified with simulations by identifying the peakings of the EMI pattern.

This paper proposes the advanced PWM method which can reduce common-mode voltage in 3 phase PWM converter/inverter system. By shifting the zero voltage vector of inverter in a sampling period, it is possible to cancel out a common-mode voltage pulse defined by switching functions of converter and inverter. Without any loss of control performance of converter/inverter system, overall common-mode voltage can be reduced by one-third compared with that of conventional PWM scheme.

Traction battery chargers are an integral part of the required charging infrastructure. EV charging systems are continuing to improve in design. The newer types are affecting power quality to a much lesser extent. High efficiency battery chargers are being designed and produced which form little or no harmonic distortion. In addition chargers are becoming smaller and lighter. This is due mainly to the fact that there are improvements in the power electronics industry, especially with respected to IGBTs. Lower costs are achieved by the reduction in price of the IGBTs, standard magnetic material and small cores for inductors and transformers. But electric vehicles occupy a relatively small market niche at present. Therefore with already existing power supply networks, establishment of EV infrastructure can safeguard the service value of present vehicle as well as ensure the ability to charge a significant number of such vehicle. In this paper, we surveyed the update charging technologies according to the conductive charging, inductive charging and fast charging. Then we suggested cost-optimized charging infrastructure in consideration of the economical, political and technical standpoint.

In this paper, a new 3-phase PWM converter power control algorithm is proposed using feedback linearization for the regulation of the active and reactive power demanded by load side. The direct power control can be realized through the proposed control scheme, cancelling out d-q axis coupling terms and nonlinear effects between inputs and states. The actual experimental results prove the feasibility of the proposed nonlinear power controller.

Balanced differential SCF with common-mode reject fully differential SC network is introduced. Through simulation, performance of balanced differential bandpass SCF and its potentiality of practical application is proposed.

A five-level VSI(Voltage Source Inverter) is introduced as a SVC(Static Var Compensator) like a large scale power source. The problems in using SVC are that the power device can easily be destroyed by voltage unbalance and accurate reactive power control is difficult because of voltage variation. A asymmetrical PAM(Pulse Amplitude Modulation) switching pattern is proposed to solve this problem and analyze both fundamental component and harmonic current in the system. Through experimental results of 3.5 kVA experimental test system. It is confirmed that DC capacitor voltage can be controlled by asymmetrical PAM switching pattern control.

In this paper. a noble dead time minimization algorithm is presented for reducing the switching losses. Firstly, the effects of the inverter dead time are examined, Secondly the principle of the proposed algorithm is explained with the commutation conditions. And the validity of the proposed algorithm is verified by simulation results. We can conclude from the results that the proposed algorithm have a virtue which is able to reducing the hamonics in the output voltages and which make the output voltage equal to the reference vlaue. Another merit is this method can reduce the number of inverter switchings.

The multi-level approach seems to be best suited to high power, high voltage ac drives with low torque ripple and fast dynamic response. If high control performance is required, space vector control becomes desirable, and the task becomes time critical. In this paper, a simplified space vector PWM method for the control of a three level inverter is proposed. As the PWM is simple in structure, it is easy to implement and the fluctuation of the neutral point potential of DC link can be supressed effectively. The simulation results demonstrate that the proposed PWM strategy can be applied to high power, high voltage inverter systems. And its application to multi-level inverter is easily done on the same principle.

지금 까지 유도 가열용 인버터의 여러 가지 회로 방식이 소개 되었다. 그러나, 회로 방식을 선정 하는데 있어서 설계자의 취향, 또는 종래의 회로을 채택으로 인하여, 각기 다른 출력, 스위치 소자의 정격 전압, 전류, 및 수동 소자의 정격 전압, 전류을 만족하는 회로 선정이 될 수 있는 수식적 모델링, 비교 실험이 부족 하였다.

This paper has described about a SEPP Inverter for induction heating load. It is analyzed theoretically about the Inverter operation for induction heating. According to the parameters of induction heating load, it is proposed a method of circuit analysis and operation characteristics of the Inverter. In addition, the soft switching technology known as ZVS(Zero Voltage Switching) is used to reduce turn on and off loss at switching. The Proposed inverter shows it can be practically used as power source system for high frequency induction heating appliancs.

In the case of synchronous machines, certain power system disturbances cause the induced rotor current to assume negative values when no static converter is present. A converter, however. prevents negative current from flowing, so that overvoltages occur. The overvoltages can be effectively limited as crowbar circuit using GTO. This newly proposed crowbar circuit with current limiting resistor absorbs energy when overvoltage comes from power system repeatedly and is verified through experiment.

In this paper, a control method for field weakening region of induction machine drive which is based on indirect field oriented control was implemented. Also, application method of direct field oriented control in the field weakening region using maximum torque control methods which is adaptable for parking facilities was studied. The implemented method which is based on direct field oriented control method ensures the full utilization of the output torque capability of the machine over the conventional 1/${\omega}_r$ method. And machine drive system can obtain the robustness to motor parameter variation.

In this paper, the robust vector control method of Induction Motor for the purpose of improving the system performance deterioration caused by parameter variations is proposed. The full order state observer estimates the stator current and the rotor flux by using the state prediction of state variables. And, the motor speed is estimated without speed sensor using the full order state observer. Also, the parameter variation is compensate by the Sliding Observer. By using this method, speed sensorless control and current contol with no affection of the parameter variation can be obtained simultaneously.

D-STATCON using the multilevel voltage source inverters is presented for voltage regulation and reactive power compensation in distribution system. This cascade M-level inverter consists of (M-1)/2 single phase full bridge inverter(FBI). This multilevel inverter is a natural fit to the flexible ac transmission systems(FACTS) including STATCON, SVC, series compensation and phase shifting, It can solve the problems of conventional transformer-based multipulse inverters and multilevel diode-clamped inverters. From the simulation results, the superiority of D-STATCON with cascade multilevel inverter is shown for high power application.

This paper proposes a new snubber circuit for multilevel inverter and converter. The snubber circuit makes use of Undeland snubber as basic snubber unit and can be regarded as a generalized Undeland snubber. The proposed snubber keeps such good features as fewer number of components, improved efficiency due to low loss snubber, capability of clamping overvoltage across main switching devices, and no unbalance problem of blocking voltage. Furthermore, the proposed concept of constructing a snubber circuit for multilevel inverter and converter can apply to any kind of basic snubber unit such as Holtz nondissipative snubber, McMurray efficient snubber, Lauritzen lossless snubber, etc which have been utilized for two-level inverter.

In this paper, single-phase PWM AC to AC converter that operates with unit power factor and sinusoidal input line currents is presented. The output voltage of this converter is able to be obtain step up voltage as well as step down voltage. because the converter applies to operating method of buck-boost converter. The control of this converter is performed with PI control method. By using this control method low lipples in the output current and the voltage as well as fast dynamic response are achieved.

This paper proposes a new control scheme for enhanced power factor in the boost type AC/DC rectifier. The control scheme is to generate duty-cycle pattern without instantaneous measurement of the input line current. With a very simple controller structure the line current is forced to trace a sinusoid in phase with input voltage. The simulation results show the validity of the proposed control scheme.

This paper presents a simple switching method to generate a PWM pattern mostly relevant to signle-phase three-level PWM rectifier. The adopted PWM switching pattern is performed in a manner similar to the space vector PWM method, which is popularly used in the three-phase rectifier and inverter. A set of possible voltages has been selected so that an equation with a time integral considered within a sampling period should be satisfied every sampling time. The simulation result shows that the proposed control scheme is good in some performance criteria such as unity power factor, low harmonic distortion of input current, dynamic response and voltage balancing of two series-connected DC capacitors.

A new PWM rectifier which offers a unity power factor is proposed. The circuit has same inductance as the conventional boosting type PWM rectifier in powering mode, but the inductance is splitted to 2 part in freewheeling mode. So the period of freewheeling mode is shorter than that of conventional boosting type PWM rectifier, and discontinuous input current is obtained in wide duty range. Therefore the proposed PWM rectifier accomplishs a unity power factor in wide range of duty ratio and boosting factor. And the conventional boosting type PWM rectifier has poor power factor near the unity boosting ratio, the proposed PWM rectifier improves this problem. The mathmatical analysis are presented and experimental results are given.

This paper presents a novel current control system to eliminate the steady state control error for PWM AC-DC converter. A general mathematical model of the converter which is represented as a state-space model is established. The state-space model is used for the simulation of converter with the proposed tracking control system of sinusoidal current. In this system, a novel current control which do not require coordinate transformations using internal principle of PI controller is described. It is proved that the steady state deviation reduce to zero through a transfer function of source current control system. Finally, simulations show good source current control characteristics by means of a simplified control system which do not require coordinate transformations.

GTO inverter used for traction motor drives includes harmonics in the output current and torque by the limitation of switching frequency. However, the hybrid PWM method, using SPWM in low frequency range and SHE PWM in upper frequency range, can be obtained the relative less harmonic characteristic. The transient reaction, which the magnetic flux and the torque is altered and instantly the large current is flowed, may be produced at the mode change. This paper presents the techniques which can reduce the transient reactions produced in the gear changing of inverter fed traction motor drives operating in the hybrid PWM. The results are verified by the simulations.

In this study, we present the power conversion system of the passive transponder which is operated at 2.4GHz. First, The passive transponder which is the power conversion system is one of the passive transponder elements is presented. And then the power conversion system is analyzed and simulated.

The three-level voltage source inverter (VSI) is good topology for high voltage and high power applications where no semiconductor devices are available. However, it has an inherent problem of switching loss and midpoint charge balance. Therefore, this paper presents two ways. The one is to adopt ZCT soft-switching method to the conventional three-level VSI. The another is to be proposed the method of the midpoint charge balance in three-level VSI. To prove the proposed topology, the paper presents a comprehensive evaluation with theoretical analysis, simulation and experimental results.

본 연구에서는 단상 인버터에서 출력 고조파 성분을 억제하기 위해 3레벨 PWM 인버터의 전력회로를 제안하였다. 이 제안된 전력회로를 이용하여 정현적 PWM전압을 발생하기 위한 스위칭함수를 구현하였다. 또한 부하변동에 따른 동특성을 개선시키고, 인덕터의 편자현상을 보상하기 위해 인덕터의 전류제어기를 구성하였다.

Reference/modulating waveform continuity is not a necessary condition for the implementation of switching patterns for three-phase pulse-width modulated(PWM) converters. This is based on the fact that the converter phase-voltages do not need to be sinusoidal and switching pattern discontinuities do not degrade the quality of output/input voltage/current waveforms by introducing low-order harmonics if certain parameters are optimized. This paper introduces the selected harmonic elimination to reduce the switching frequency and low-order harmonics compared with continuous PWM techniques and some discontinues switching patterns for PWM converter.

In this paper, a new simplified configuration for a multi-level PWM inverter is proposed. The proposed inverter consists of an auxiliary circuit with one switching device, and 3 phase full-bridge inverter. The proposed inverter, in spite of reduction of the switching devices, offers characteristics similar to the NPC(Neutral - point - clamped)- PWM inverter. Also, since the reduction of the switching devices, the control strategy is simplified. And switching loss is reduced. In addition to, it is possible that reliable DC level voltage than former multi-level inverter. And load power application is same to conventional NPC-PWM inverter. The performance of the system is verified by simulation. In this paper, show the simulation result of the single phase full bridge inverter application.

This paper describes a gate drive circuit for series connected IGBTs in high voltage applications. The proposed control criterion of the gate circuit is to actively limit the voltages during switching transients, while minimizing switching transient and losses. In order to achieve the control criterion, an analog closed loop control scheme is adopted. The performance of gate drive circuit is examined experimentally by the series connection of three IGBTs with conventional snubber circuits. The experimental results show the voltage balancing by an active control under wide variation in loads and imbalance conditions.

Harmonic analysis is important for PWM rectifiers with high powerfactor. This paper describes the harmonic analysis of input current in high powerfactor boost-type rectifier. The magnitudes of the harmonics are obtained through the current wave from analysis and the effect of source reactance is also analyzed.

Recently, new trend in telecommunication device is to apply low voltage, about 3.3V-1.5V. However, it is undesirable in view of high efficiency and power desity which is the most important requirement in the distributed power system. Rectification loss in the output stage, in on-board converter for distributed power system are constrained to obtain high efficience at low output voltage power suppies. This paper explains the basic operational principles of three kinds of ZVS DC/DC converters with self-driven synchronous rectifier. The three topologies are analyzed by simulation and exprimentation, and the characteristics comparisons of high efficience converter are carried out in view of the minimized rectification losses in the out stage.

본 논문에서는 출력단에 동기정류기를 사용하는 영전압 스위칭 방식의 고효율 하프 브리지(H-B)컨버터에 대해 다루고자 한다. 컨버터 손실의 대부분은 출력단 정류기 부분, 주 스위치, 트랜스 등에서 발생되며, 이중 출력단 정류기에 쇼트키 다이오드를 이용하는 경우 쇼트키 다이오드의 on-drop에 의한 손실이 적지 않게 된다. 따라서 이를 감소시키기 위해 쇼트키 다이오드를 MOSFET동기 정류기로 대치하고자 한다. 동기 정류기 방식에 이용되는 MOSFET에는 도통손실이 있으나 이는 쇼트키 다이오드의 on-drop에 의한 손실에 비해 매우 작으며, 특히 MOSFET의 기생 성분을 이용하여 영전압을 구현함으로써 MOSFET의 도통 손실을 현저히 감소시킬 수 있게 된다. 또한 H-B 컨버터의 경우 주 스위치에 전원전압과 동일한 크기의 전압이 인가되므로 내압이 작은 소자의 이용이 가능하게 되며, 이와 같이 함으로써 사용 부품 수의 감소, 내압이 낮은 주 스위치의 사용, 더 나아가 효율이 높은 고효율 컨버터를 구현 할 수 있다.

The principle of the MHD generation is based on Faraday's law of induction that a eletromotive force(u ${\times}$ B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In MHD power generation system, enthalpy of the working gas is converted to electric power directly through expansion in generator channel. It means that electric power can be generated without moving mechanical linkage such as turbine blades. There are two types in the MHD generator; linear type Faraday and disk type hall generator. Disk type hall generator is the main target of this paper. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

This paper presents an optimal efficiency control for the inverter fed induction machine system using neural network. The motor speed and the load torque vary the efficiency characteristics of an induction motor. The optimal slip frequency has nonlinearity varied by the load torque as well as the motor speed. The induction motor is driven using the inverter system and the indirect vector control method which input is slip frequency. The neural network for estimating the optimal slip frequency has two input layer(the motor speed and the load torque) and one output layer(the optimal slip frequency that minimize the input power). Learning algorithm of the neural network is the back-propagation. Using the equivalent circuit including the nonlinearity of the induction motor, the loss reduction is analyzed quantitatively. Experimental results are shown noticeable power savings by proposed scheme in high speed and light load conditions.

A single phase induction motor is predominant in fractional horsepower rating and is widely used in home and industrial equipment. For example, these motors provide the motive power to washing machines, fans, refrigerators, etc. In this paper has presented the design and implementation of a microcontroller software - based self - starting SPIM. The control algorithm used in the experimentation employed simple control strategies which enabled a single chip programmable microcontroller to execute both the self - starting and self - detecting control of SPIM with relatively simplified hardware.

A vector control scheme is widely used in AC drive system in these days. In this country for commercializing the system, it has lots of dependency on advanced foreign technology. Therefore we have developed high-performance vector controlled inverter sytems ourselves for two years whose capacitives are 15kW, 30kW and 45kW. For computation of data in high speed DSP is empolyed and by using a IGBT with high switching the current ripple is reduced. Consequently, developed drive systems have high performance and accurary on speed control. There are proved in experimental results.

The compensation problem of error and various problems due to delay of speed sensor itself and speed detection have issued in case using speed sensor in the adjustable speed control of induction motor. This paper have applied the stator flux oriented vector control algorithm and space voltage vector PWM method in order to improve an dynamic character of voltage-source inverter system, and also used the better IP controller in the speed response than Pl controller as speed controller. This paper estimated the rotator speed using input current of inductor motor and flux component invoked through voltage drop by terminal voltage and stator resistor.

This paper deals with the tension control of continuous processing line for steel plant. In order to improve the tension control performance, tension control is included in POR. FF compensation is applied to get the same speed characteristics during acceleration and deceleration period. In simulation roll diameter variation and inertia variation are considered. It becomes clear that the proposed tension control system has high accuracy performance.

A speed controller of a induction motor using Microcontroller and Fuzzy logic is presented in the paper. Generally, fuzzy logic controller is known as a controller which can be coped with a non-linear and a complex system. A fuzzy logic is used for robust and fast speed control and space vector modulation method is used for PWM wave generation in this proposed system. The results of experiment show excellence of the proposed system and that the proposed system is appropriate to control the speed of a induction motor for industrial application.

In this paper, the compensation algorithm of the stator resistance which is essential to improving the performance of the direct vector control system is proposed. This paper focuses on the improvement in the torque response of the direct vector control in a constant speed region. The conventional compensation algorithms are analyzed and a new method is developed to compensate the stator resistance in the direct vector control system. In addition, the effect of the variation of the stator resistance on the drive performance is analyzed for the vector control. The proposed algorithm is very simple to implement that does not require the modifications on the motor model or additional interrupts of the controller. Also, the value of the stator resistance can be obtained in real-time through the measurement of the terminal voltage and current. From the simulation and experimental results, the validity of the proposed scheme is confirmed.

The rotor speed flux information most important in the speed sensorless vector c So in the paper used current voltage model for flux information in a induction motor. Voltage realized low pass filter insted of integrator, c model realized used of current equation. And cur voltage model estimated flux compoed of Pl cont For conpensation of estimated flux error conpansation algorithm using exactly, rapidly flux obtained for conpensation of estimated flux Proposed control system used TMS320C31 DS high speed processing. The effectiveness of proposed method is verified by simulation experimental results. This method shows h characteristic speed estimation highly flux esti and stable, robust character of load regulation.

When the vector control, which does not need a speed signal from a mechanical speed sensor, it is possible to reduce the cost of the control equipment and to improve the control performance in many industrial application. This paper describes a rotor speed identification method of induction motor based on the theory of Model Reference Adaptive System(MRAS). The identifier execute the rotor speed identification so that the vector control of the induc-tion motor may be achieved. The improved auxiliary variable are introduce to perform accurate rotor speed identification. Simulation and experimental result show the validity of the proposed control method.

The conventional PI controller has been widely used in industrial applications. If a PI control gain is selected suitable, the PI controller shows very good control performance. But it is very difficult to find the optimal PI control gain. Therefore, in this paper, the 4-rule based fuzzy logic modifier of the conventional PI controller are presented. The fuzzy logic modifier which exhibits a stabilizing effects on the closed-loop system, has good robustness regarding the improperly tuned PI controller. The simulation are performed to verify the capability of proposed control method on vector controlled induction motor drive system.

This paper deals with the design of a field oriented control system model for the high performance induction motor using Matlab with Simulink. The proposed control system model, which is not used the speed and flux sensor, contains IM model, Tranformation, Decoupling, FFOC(Field Flux Orientation Controller), Torque calculator and PI Controller to control speed, torque. Results present the stator and rotor flux phasor trajectory, the startup and transient response of speed, torque and stator current with field oriented control and the response to changes in reference speed with no load. This paper shows that the propose control system is more robust than other vector control system, and suggest the enchanced model, using Matlab with Simulink for the high performance in induction motor control.

In design of a digital current controller for a 3$\phi$ voltage-source (VS) PWM converter, its conventional model, i.e., stationary or synchronous reference frame model, is used in obtaining its discretized version. It introduces, however, inherent errors since the following practical problems are not taken into consideration: the characteristics of the space vector-based pulsewidth modulation (SVPWM) and the time delays in the process of sampling and computation. In this paper, the new hybrid reference frame model of the 3$\phi$ VS PWM converter is proposed considering these problems. In addition, the direct digital current controller based on this model is designed without any prediction or extrapolation algorithm to compensate the time delay. So the control algorithm is made very simple. The validity of the proposed algorithm is proved by the computer simulation results.

In this paper we further propose to add a very simple regenerative clamping circuit to SSIPP to reduce the voltage stress and to recycle the energy trapped in the leakage inductance of the isolation transformer, thus eliminating the need for a lossy snubber circuit. In addition, this proposed clamping circuit also provides a mechanism to reset the magnetizing current of the output transformer of SSIPP employing a Forward converter as the output stage. Simulations and experimental results are reported to verify the operation and performance of the SSIPP with regenerative clamping.

Many power plants built 20-30 years ago are facing problems associated with the excitation system used for controlling generator output voltage. After years of reliable operation, generation is experiencing increased down time due to maintenance associated with the exciting excitation equipment. Reliability of the excitation system has become an issue, especially where many of these generation plants may be critical to the internal processes used for manufacturing. Wear out mechanisms such as those associated with the wire wound rheostat the electromechanical voltage regulator, insulation failures of the rotating exciter and commutator deterioration have become real problems typical of many older installations. These are some of the issues that are affecting system reliability for older power plants. This paper will address typical problems associated with the old excitation systems and the justification for a replacement static excitation system used in many Paper Mills.

We have developed a compact high frequency switch mode converter (HFSMC) power supply with DC 50 kV output voltage and 10 kW output power. Since the inverter circuit uses 25 kHz rescharging scheme, the current is flowing with t kHz. For the efficient output voltage transform performed a simple design process using the transformer principle and the commercial specification. For the DC 50 kV output, we employed 7 pa windings of secondary coils for the series stac connection of the output with full-bridge rectifi In this paper the design detail and the test re the high frequency transformer together with HFSMC power supply are presented.

It is always necessary to high performance power supplies for the magnet system in the accelerator, especially when the number of power supplies are large. When have developed the compact power supply using switching technology instead of SCR phase control. We adopt the pulse width modulation(PWM) method with a half bridge DC/DC converter. In this way, we can make a compact system with light weight and small volume. Actual system we developed is 1.2kW, 35V/35A bipolar DC power supply current precision of +/-0.02%. It is possible to mount 10 unit in a conventional 19 rack. The built in controller has an RS422 protocol to drive 10 unit by one serial port up to 1.2km distance. If we adopt RS485 protocol, one serial port can control 32 power supplies. In this paper, we will report the design and performance of the prototype power supply.

This paper describes a DC-DC converter connected two unites inverters, a half-bridge type of high frequency resonance inverter, at the input with parallel. The proposed paper certified that theorem waveforms are equal to experiment waveforms, in addition, it estimated characteristics such as characteristic of average power, characteristic of average output voltage, characterisic of output voltage ripple etc., for designing the device with normalized parameter value.

In the buck-boost DC-DC chopper which is used at a certain situation such as in factories where loads often change a lot, the switches in the device make big energy loss in operating at Buck-Boost Mode due to hard switching and are affected by lots of stresses which decrease the efficiency rate of the converter. In order to improve this problem, to decrease the loss of snubber and switching, it has been investigated that zero voltage switching mode and zero current switching mode which make the operation of switches with soft switching. For the more sophisticated and advanced device, this paper is presented the Partial Resonant Soft Switching Mode Power Converter which is adapted the power converter having the partial resonant soft switching mode, that makes switches operate when the resonant current or voltage becomes zero by making the resonant circuit partially at turning on and off of the switches with suitable layout of the resonant elements and switch elements in the converter. Also, this paper includes the analysis and simulation of the Partial Resonant type Buck-Boost Chopper.

In this paper, Operation characteristics of the active clamp(ACL) zero-voltage-switching(ZVS) forward converter(FC) and active clamp hard- switching(HS) forward converter are compared with respect to loss analysis. The losses of semiconductor (including conduction losses and switching losses), transformer(containing the core loss and copper loss) and parasitic element of passive element (capacitor, inductor) are measured and compared for each type. For an experiment we have built 50W ACL ZVS-FC and ACL HS-FC, in which the switching frequency is 200kHz, and test it. The experimental results show that both types of operation have nearly same characteristics.

In this paper, we proposed the alternated forward multi-resonant converter. It can reduce the voltage stress due to the operation of two multi resonant switches and also provides a high frequency applications. The proposed circuit is verified through the PSpice simulation and the 50W experimental set with 2MHz maximum frequency. The measured voltage stress is up to 170V of 2.9 times the input voltage and the efficiency is about 81.66% at low line.

To store and maintain electron beams in synchrotron machines, it is very important to read and keep precise magnet current ($<{\pm}50$ ppm). However, accurate DC current measurement tools are not readily available. In this paper, we introduce high precision, wide band zero-flux current transformer that is manufactured and tested at Pohang Accelerator Laboratory. This sensor can measure DC as well as AC current. Accuracy of the current transformer is less than ${\pm}$20 ppm. Performance of the manufactured current sensor is compared with a high precision DCCT which is commercially available sensor.

An uninterruptible power supply(UPS) with parallel operation is used to increase the power capacity of the system or to secure higher reliability at critical loads. In the parallel operating system composed of the multiple UPSs, load-sharing, i.e. current balance control between them is key technique. Because of its low impedance and quick response characteristics, inverter output current changes very rapidly and thereby easily researches an overload condition. The difference between total load current divided by number of operating inverters and its own current is detected as unbalanced current. Then frequency and voltage are controlled to minimize the active component and the reactive component. A good performance of the proposed load-sharing technique is verified by experiments in the parallel operating system with two 40kVA UPSs.

In spite of nonlinear or step-changing load and line disturbances, the inverter for the UPS must provide the pure sinusoidal output voltage with low THD(Total Harmonics Distortion). This paper proposes an inverter controller for the UPS which has a good dynamic response characteristic and robustness for applying industrial world directly. The inverter output voltage is controlled instantaneously with a double regulation loop by a TMS320C31 Digital Signal Processor so that it has very good dynamic response for nonlinear or step-changing load and line disturbances. To improve the voltage utilization and response characteristics, the Space Vector Modulation(SVM) technique is adapted for the switching method of this system. The characteristics of the proposed control system were verified by simulations and experiments.

A conventional UPS can supply the clean power to the load. However, it may generate input current harmonics and the input power factor can be very poor. Therefore, the UPS itself may be a power interruption. This paper provides multifunctional converter of using single phase UPS. The proposed UPS can supply the clean power to the load without polluting the mains power system. The multi-functional converter provides battery charging, var compensation and harmonic suppression simultaneously. It was simulated to verify this work.

In order to maintain a high quality output voltage, conventional UPS systems use complex filters with large passive components. To overcome this drawback, real time feedback control schemes have been invested. However, these techniques require a high inverter switching frequency to dynamically adapt to changing load conditions reduce harmonics of the output voltage, thereby rendering the system inadequate for high power applications. This paper presents real time digital signal processor(DSP) control of a large capacity UPS system feeding nonlinear loads to provide a sinusoidal inverter output voltage, unity input power factor, low bus voltage ripple, and excellent transient response.

The proper placement of work-coil is needed for heating the interior of an IH rice cooker uniformly. It is possible that the flavor of rice is better by heating it through the optimal placement of the work-coil of the IH rice cooker. This paper describes the procedure and the result of finding the optimal placement of the work-coil by analyzing the properties of the rising temperatures of the interior through Taguchi Method.

The development of the high-frequency induction-heating for 1800kW power range intend to make localization at forging and rolling mill part by technical innovation. And, the development makes to increase our's competitive power at technique, quality and cost. This paper describes the heart of high-frequency induction-heating technique, switching technique, a few problem in common using as an unsatisfied technique, load adjustment technique, system control, diagnostic system and auto-interface etc.

A prototype semiconductor switch for the command resonant charging system has been developed for a line type modulator, which charges parallel pulse forming network(PFN) up to voltage of 5 kV at repetition rates of 60 Hz. A phase controlled power supply provides charging of the 4.7 ${\mu}s$ filter capacitor bank to voltage up to 5 kV. A solid state module of series stack array of sixe matched SCRs(1.6 kV, 50 A) is used as a command charging switch to initiate the resonant charging cycle. Both resistive and RC snubber network are used across each stage of the switch assembly in order to ensure proper voltage division during both steady state and transient condition. A master trigger signal is generated to trigger circuits which are transmitted through pulse transformer to each of the 6 series switch stages. A pulse transformer is required for high voltage trigger or power isolation. This paper will discuss trigger method, protection scheme, circuit simulation, and test result.

신경회로망을 사용하여 몇 가지 경우에 대해 측정된 토오크 프로파일로부터 모든 전류값 및 회전자위치각에 대한 토오크 및 인덕턴스를 구하였다. 이를 바탕으로 수치해석을 통해 토오크중첩을 고려한 총합 발생토오크의 맥동성분을 최소화시키는 기준토오크 파형을 설정하여 제어하였다. 또한 제안된 방식을 실시간으로 처리하고, 제어기의 신뢰성을 높이기 위해 DSP를 사용하였다.

A cylindrical type Linear Pulse Motor (LPM) was designed as a linear motion actuator. In this paper, it is mentioned the mechanical design method of the LPM. It was designed as a prototype to estimate a new linearization control method for the nonlinear thrust force which is caused by the variable reluctance of the LPM. The designed LPM is determined a variable reluctance type to except the term of permanent magnetic force. The concreted figures and the dimensions will be described.

This paper presents STATCON(Static Condenser) control schemes for voltage regulation, power factor correction and harmonics mitigation. Each control scheme can be applied in the system depending on the system requirements. The 20KVA STATCON is developed and tested in the reduced system model for the verification of three different control algorithms. The results of proposed controls are compared for power factor correction and voltage regulation algorithms. For each algorithm, harmonic mitigation scheme is adopted as a part of control. Finally verification of STATCON for the transient response is implemented by voltage flicker test.

This paper describes an experimental results to analyze the dynamic characteristics of STATCOM, which is connected to the ac system for improving the voltage stability. The experimental results confirms that the scaled model for STATCOM operates correctly by the conceived control algorithm and properly compensates and regulates the bus voltage at the common connection point.

This paper presents a microcontroller-based electronic neon ballasts which is highly suitable for a multi-use and low power consumption by performing economical hardwares and variable software algorithms. Result of this study has the following functions : brightness control, frequency variable output, automatic lightening control, low power characteristics.

This paper presents the design method of a dimming electronic ballast for fluorescent lamps using a frequency control IC, and investigates the effects of circuit variables on its dimming characteristics. It is shown that effective dimming is possible with IC IR2151 for frequency control, and this leads to a feasible design of more smaller and cheaper dimming ballast. Five ballasts different in the values of the series inductance and capactance are designed, and their dimming characteristics are compared. As the result, the dimming range becomes more broader as the series inductance gets smaller and the capacitance larger. Thus appropriate selection of the values of L and C should be made according to the types of application site.

A low-cost electronic starter is developed to decrease ignition failure significantly through successive starting trial and to prevent overheating at the end of fluorescent lamp life. Moreover, it has an additional feature of being capable of ignition at the recovered lamp voltage without any circuit correction. The developed electronic starter is consisted of four parts - a half wave rectifier circuit, a timer circuit, a switching circuit and a protection circuit. The protection circuit made up of a transistor and capacitors utilizing capacitive characteristics, carries out successive starting trial and end-of-life protection. Lamp ignition is completed within 0.5 seconds with taking advantage of a high preheating current from the half-wave rectifier circuit. Nevertheless, its performance is proved to be very excellent through a standard switching endurance test.

In this paper, development of power interrupt tester which is highly suitable for microprocessor-based circuits test device is proposed. ATMEL 89C2051 microcontroller is performed to make power interrupt signal, and built-in software controls peripheral hardwares and many functions. Experimental results of this study will offer a good application to electronic appliance maker as a test device of hardware and software debugging-use

In this paper, a new speed estimation method using neural networks is proposed and speed sensorless vector control is realized with the estimated speed. The effectiveness and the usefulness of the proposed algorithms are thoroughly verified with the experiments on the fully-digitalized 2.2kW induction motor drive systems.

This paper proposed an improvement in the Buck ZC-ZVS converter Presented in [1]. This is achieved by change the auxiliary switch position, which reduces its rating power. By employing saturable inductor, the maximum voltage stress across the main switch becomes constant and independent of the load current. Operating principle of Buck proposed topolo described and confirmed by simulation results.

A full bridge double resonant type inverter using Phasor shift suitable for heating magnetic and nonmagnetic at high frequency is described. A series-parallel arrangement of capacitor is adopted and optimum mode of operation is proposed. Also, Based on the characteristics value, a method of circuit design is proposed.

Switched Reluctance Motor is simple structure which used Accel/Decel application field because of cheap cost and High efficiency. For driving this motor, it is essential to need position sensor and driving converter. so, many topology and sensor have been studied untill now. Asymmetric Bridge Converter which has been known for the best control and efficiency is used chopping to control current of motor coil according to changing of motor speed. But this is embossed as a fault because it come to bring switching loss due to rapid switching frequency. In this paper, I applied to Soft Switching Mode by Partial Resonant Method to compensate these fault and to show the usabilityness of low switching device.

This paper analyzes the sources of EMI noise, and Presents the noise reduction method using the modulation of switching frequency. Modulating the switching frequency makes the noise of side bands by shattering emission spectrum, and then can reduce the size of EMI filter at input line of power supply.

This paper proposes a new lossless snubber circuit on power supply for welding machine's output rectification diode. To improve the common inverter control type power supplies' problems that energy loss and heating in the snubber circuit because the output capacity makes too big heat energy in the circuit when the output current of the inverter is rectified by the diode bridge circuit, which includes the snubber circuit. This paper suggested new snubber circuit have increased power factor and confidence of output by being regenerate thus lost energy to input node.

A gate driver suitable for forced switch-mode power converters such as UPS and motor drive system is presented. The proposed gate driver uses regenerated snubber power and requires no separate power supply. This does not impose any additional complexity on the main switch. Experimental results show that the proposed circuit is valid.

The output characteristics of solar cell are nonlinear, and these characteristics vary with load solar insolation. solar cell temperature. The PWM power inverter is realized by driving a inverter constructed with a high frequency buck-boost chopper in the discontinuous conduction mode(DCM). This paper present a buck-boost PWM inverter and its application for residential system.

Recently the automatization and the robotization of the arc welding industry is promoted and also the improvement of the welding quality and the work efficiency is required strongly. In this paper, special welding current waveform control algorithm is developed for less spatter and improvement of welding performance in the high speed and low arc voltage range. And the output control and the short circuit waveform control to the varition of the welding is studied by appling the algorithm to the power source for pulse arc welding.

In recent years, A PWM Converter or Switched Mode Converter with high power factor and sinusoidal input current have got widespread studied. But, Almost all of studies is based on linear load. This paper reports on research aimed at achieving high power factor and sinusoidal input current waveform for electronic arc welder, which has nonlinear dynamic characteristics. It is shown that simulation result yield its property.

In this paper, we carried out investigation of monitoring algorithm development for examination of inverter system. For transmiting data, RS-422C is adopted. The LabWindows/CVI development tool of National Instruments Co. is used for the formation of monitoring screen. The experimental set-up is composed of a PC to PC system. It is applicable to electric car inspection and repair.

In this paper, discharging part of high voltage pulse power supply of E-beam generating device is simulated and experimented. It is composed of high voltage part and high voltage pulse part. High voltage part is AC 380, DC/DC converter, high voltage high frequency transformer. High voltage pulse part is double pulse forming network and Thyratron. In the result, computer simulation analysis is same to experimental result and high voltage pulse is obtained 10kV, 4A, 10uS.

With the increasing demands for clean environment, development of air cleaning systems has been received increasing attention. EP is usually used for air cleaning in the coal power plant. One of the key technology in the EP is high voltage pulse power supply, which affects the performance of the overall system. In this study, high voltage micro pulse power supply for the EP is developed for a 500MW coal power plant. The power supply has a dc source and a pulse one. The ratings of the dc and pulse source are 60kV, 800mA and 70kV, 400mA respectively.

Many semiconductive switches are operated in series for high voltage operation. The same number of gate drivers are needed to control all the switches, hence, the drivers cause high cost and system complexity. In this study, a simple and low cost gate driver for high voltage thyristor-diode switches is investigated. This gate driver can operate several high voltage thyristor-diode switches at the same time.

In this study, the speed sensorless vector control system with the magnetizing inductance compensation structure is presented. The estimations of the rotor speed and the magnetizing inductance using the terminal voltages and currents are performed with the reduced order Gopinath flux observer. The rotor speed is estimated by the torque producing current which is derived from the estimated value of the rotor flux and the measured stator currents. In order to compensate the variation of the magnetizing inductance under the saturated conditions, we also established the compensation scheme which is made with the instantaneous reactive power. The validity of the proposed method is verified by simulation results.

This study was carried out about the manufacture of test equipment for traction Motor Driving. The power converter is driven by two converter serially and keep a high power factor of power source. This system is haven all the characteristic of voltage source converter by having a processing ability of regenerating power. The traction motor is controlled by IGBT inverter. The test equipment is composed of traction motor, torque-meter, clutch, and inertia body of tubular type.

We proposed the speed control of the SLIM(Single-sided Linear Induction Motor) for conveyance system by the decoupled thrust control. The voltage equations of SLIM are expressed on the suitable $\alpha-\beta$ axis by the proposed equivalent circuit, which can analyze the characteristics of the thrust and the normal force and so on. These control methods, which are the slip angular frequency control and the decoupling control for the thrust and normal force by analyzing these parameters can be successfully driven without interfering of each axis. These results exemplified the linear drive of SLIM with the reference value.

This paper presents a Class-D type switched mode audio power amplifier employing ZVT(Zero-Voltage-Transition) soft switching technique. In order to obtain a wide bandwidth and lower distortion for an audio amplifier a high switching frequency is essential. The ZVT switching scheme enables a high frequency switching without sacrificing the efficiency much as in a hard switching. A prototype amplifier is built to demonstrate the feasibility of this technique for the audio power amplifier.

This paper proposes a constant frequency controlled zero voltage switching method that can reduce switching losses caused by emf on inductance in DC motor. The zero voltage switching method is used more than a zero current switching method because of reducing switching losses by capacitance of depletion region of MOSFET. To simplify the controller circuit, we propose constant frequency controlled zero voltage switching method in the paper. The control method is more stable than a variable frequency control method because it can optimize bandwidth of a closed-loop and reactances. Therefore, we construct a constant frequency controlled zero voltage switching converter and improve zero switching losses in high switching frequency. In the process, we can control low-losses in full range on variable voltage and load. We simulate the proposed converter with P-SPICE and compare results obtained through the experiment.

The traveling wave type ultrasonic motor(USM) has no electro-magnetic circuits( coil or core). The driving principle of the USM is based on high-frequency mechanical vibrations and frictional force. The USM, thus, is fed by two-phase high - frequency sinusoidal inverter using its series resonant parasitic components. For the using of series resonant type inverter, it should be needed to a USM parasitic capacitance and a proper inductor chosen. In this paper, the values of optimal inductance are designed and the efficiency of USM drives is achieved. The effectiveness of the proposed design is demonstrated by experiments.

This paper describes a Battery Checking & Monitoring System for monitoring battery cell and power system in Uninterruptible Power Supplies(UPS). The system is capable of measuring, in a matter of setting time, float and discharge voltage of up to 240 cells in a single installation, and has the memory capacity to store battery's alarm data information on up to 200 separate sites. This system are easy to maintain and attain cost effectively, so that prepared for meeting the customer's service needs immediately. The system is additionally programmed with a each model, that will enable to accurately determine the remain battery capacity in a UPS system following a short discharge test. It is also equipped with remote interrogation and control facilities.

In this paper a new high voltage dc power supply is proposed. The proposed power supply is suitable for a load having frequent short circuit. A spark down occurs frequently in a load such as ion source. To protect the ion source and power supply in case of spark down the fast switch off of the power supply is necessary. The proposed power supply scheme improves the performance, efficiency and reliability of the conventional power supply.

This paper presents an adaptive control scheme of a ballast for HID lamp for an automotive headlight. A flyback converter is used for the voltage step-up and for the control. A full bridge inverter is used as a ballast topology. The proposed control method is an adaptive output power control with a charge control. The developed ballast satisfies the requirement of a fast warm up characteristics and operating stability for an automotive application.

A PWM inverter using power FET is developed to switch the excitation current of 5 phase hybrid stepping motor for the use of driving X, Y table. A micro processor based controller is also developed to control the excitation current switching of X, Y axis stepping motor as well as synchronizing operation of Z-axis servo motor. The developed driving control system is applied to the industrial embroidery sewing machine.

In order to improved the three phase GTO CSI of high efficiency IM drive with low loss commutation and snubber energy, we studied the energy recovery circuit to recover stored energy in clamping capacitor, dc link inductor and snubber capacitor, used an induction motor as the load of inverter. Specially, we investigated how dc input power is increased or decreased according to size of dc link inductor. The validity of this system is proved through experiment.

In this paper, a speed estimation based on the quick torque control is proposed to realize speed sensorless control in a full range of induction motors. The proposed method can be formulated simply from a motor circuit equation and conducted easily by detecting primary motor currents and a voltage command at every sampling time. Since the method need not the differential values of primary currents in an arithmetic of a speed, it can be expected to improve the precision of speed estimation in a very low speed area, especially. Some numerical simulations were conducted with the assumption of using a Pulse Width Modulation voltage source inverter.

Sunlight makes it possible to adjust scale of electric power easily as a electric energy without air pollution. Solar cell to convert the sunlight to the electric energy has DC output which is influenced on temperature and irradiation time. Conversion of DC output from the solar cell to AC is necessary due to the fact that most loads to be used currently are compatible with AC generally. In the present work, Two-phase chopper system with two seperate groups to obtain two identical DC is used to preserve the energy from the solar cell in two battery. They are controlled to be operated around maximum output of the solar cell under the condition of constant voltage. Photovoltaic system with DC${\rightarrow}$AC conversion is also investigated for big capacity and two seperated electric power using two separate inverter.

Recently, for increasing consumed power and informational society, confidence of power supply is demanded. Beside, owing to most of these loads are nonlonear, utility line is polluted by these components, therefore, it is demanded compensation of harmonic current. In times past, special order of harmonic current is only compensated by passive filter, but active power filter can compensate whole harmonic current. Therefore, this paper propose uninterruptable power supply(UPS) with performance of active power filter.