• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.535-539
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• 1989

A high-frequency asymmetrical PWM control technique is proposed which can improve the input power factor of ac chopper and also suppress its harmonic contents of currents at both its input and load sides and the acoustic noises by its switching semiconductor devices. The ideal switching function for the proposed technique is derived and hence converted into asymmetrical PWM pattern for practical implementation of ac voltage regulator. Also the various power circuits of three phase AC choppers are suggested. The theoretical characteristics of the proposed PWM technique are investigated by digital simulation.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.172-175
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• 2005

Recently international regulations governing the amount of harmonic currents(e.g IEC 61000-3-2) became mandatory and active Power factor correction (PFC) pre-regulator circuit became inevitable for the AC/DC converters. Among these topologies, the boost topology represents an optimum solution for a PFC pre-regulation in a high power application. This paper propose improved ZVT(Zero Voltage Transition) AC/DC PFC Boost using the average current control employing a soft-switching technique of the auxiliary switch with a minimum number of components. The conventional ZVT PFC Boost Converter has a disadvantage that the auxiliary switch turns off hard, which influences the overall efficiency and the EMI problem. In this paper, an improved ZVT PFC Boost converter using active snubber is proposed to minimize the switching loss of the auxiliary. The prototype of 100kHz, 640W system was implemented to show the improved performance.

• Journal of Power Electronics
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• v.13 no.2
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• pp.256-263
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• 2013

This paper presents an IHQRR (Integrated High Quality Rectifier Regulator) BIFRED (Boost Integrated Flyback Rectifier Energy Storage DC-DC) converter fed BLDC (Brushless DC) motor drive. A reduced sensor topology is derived by utilizing a BIFRED converter to operate in a dual DCM (Discontinuous Conduction Mode) thus utilizing a voltage follower approach for the PFC (Power Factor Correction) and voltage control. A new approach for speed control is proposed using a single voltage sensor. The speed of the BLDC motor drive is controlled by varying the DC link voltage of the front end converter. Moreover, fundamental frequency switching of the VSI's (Voltage Source Inverter) switches is used for the electronic commutation of the BLDC motor which reduces the switching losses in the VSI. The proposed drive is designed for a wide range of speed control with an improved power quality at the AC mains which falls within the recommended limits imposed by international power quality standards such as IEC 61000-3-2.

• Journal of Power Electronics
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• v.10 no.5
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• pp.538-547
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• 2010

This paper deals with a stand-alone wind energy conversion system (WECS) with an isolated asynchronous generator (IAG) and voltage and frequency (VF) control feeding three-phase four-wire loads. The reference generator currents are estimated using the instantaneous symmetrical component theory to control the voltage and frequency of an IAG system. A three-leg voltage source converter (VSC) with an isolated star/delta transformer is used as an integrated VSC. An integrated VSC with a battery energy storage system (BESS) is used to control the active and reactive powers of the WECS. The WECS is modeled and simulated in MATLAB using the Simulink and the Sim Power System (SPS) toolboxes. The proposed VF controller functions as a voltage and frequency regulator, a load leveler, a load balancer and a harmonic eliminator in the WECS. A comparison is made on the rating of the VSC with and without ac capacitors connected at the terminals of an IAG. Simulation and test results are presented to verify the control algorithm.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.2 no.2
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• pp.64-70
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• 1988

In many applications of inverter system, it is desirable to obtain an AC output voltage with variable frequency and amplitude. For the variable-speed AC motor drive, the system is one major area of application for the variable-frequency inverter. V ariable~voltage variable-frequency sinusoidal output in three-phase inverter is possible by employing the techniques developed. In this paper, the technique of particular harmonics elimination(PHE) in three-phase PWM inverter-output waveforms is introduced. The required switching patterns are determind on personal computer. Results are stored in look-up table in EPROM and used to control the switching of the inverter devices. The experimental results indicate that the loss in an induction motor is minimized to a degree by using this algorithm. The proposed PWM pattern is effective not only to the induction motor but also to the other electromagnetic machine such as Voltage Regulator, UPS.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.11
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• pp.671-679
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• 2004

This paper presents the on-line current controller tuning method of grid-connected inverter using PSO(particle swarm optimization) technique for minimizing the harmonic current. Synchronous frame PI current regulator is commonly used in most distributed generation. However, due to the source voltage distortion, specially in weak AC power system, current may contain large harmonic components, which increase THD(total harmonic distortion) and deteriorates power quality. Therefore, some tuning method is necessary to improve response of current controller. This paper used the PSO technique to tune the current regulator and through simulation and experiments, usefulness of the tuning method has been verified. Especially in simulating the tuning process, ASM(average switching model) of inverter is used to shorten execution time.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.5
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• pp.82-89
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• 2007

AVR(Automatic Voltage Regulator) of exciter control system in AC generator controls voltage and current according to load and terminal voltage variations in order to remain at the bus voltage. The output characteristics of main generator is dependent on the control performance of AVR. This paper presents the PWM type exciter system with transient response compensator for robust control of load variations. Additional transient response compensator generates compensation signal for load variation. So the proposed excitation control system has fast dynamic response in transient period and can control terminal voltage constantly. The proposed method is verified by the computer simulation and experimental results in prototype generation system.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.87-90
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• 2003

There are generally two temperature control methods using ac voltage regulators - the phase control method and the on-off control method. The phase control method uses thyristor's angles of extinction for the output power regulation and the on-off control method uses the control of on and off times for the output power regulation. Both of methods have the problems that are the unbalance of the three phase and surge current caused system's destruction. The main object of this study proposes a solution of problems of surge currents and unbalance of three phase when thyristor voltage regulator is switching. To solve the problem, It is proposes that the solution of surge currents is using a tap transformer and an additional switch with adjustable resistance and applies zero crossing of switching voltage of two input line to power load. This method is discuss and verified by computer simulations and experiments.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1697-1699
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• 2001

In this paper, the circuit of AC Choppers for $CO_2$ laser power supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transformer used with the proposed system. This improved circuit employs a 3 electrode - type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirement, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$ : $N_2$ : He = 1 : 9 : 15, total pressure of 15torr.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.211-213
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• 2007

The electrical parameters are used to calculate gains in the current regulator as well as to determine the reference currents of speed controller in various control strategies of Synchronous Reluctance Motors (SynRMs). Many methods of measuring or estimating the electrical parameters of SynRM have been proposed by other authors. But almost papers only measure or estimate in the limited conditions without fully considering the effects of inverter, connecting wire and magnetic saturation. The parameter results are usually different from the real system parameters. The drive performance, therefore, can not be good if using inaccurate parameters. In this paper, several methods used to measure the electrical parameters are introduced. The first method is LCR meter. And then, a method determining inductances by measuring AC current and voltage from AC power supply is presented. A new method with high reliability is proposed to measure the electrical parameters of SynRM. The experiment results verify the effectiveness of the new proposed method.