• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.194-197
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• 2007

This paper proposes a linearization technique for the 3 level NPC type inverter, which increases the linear control range of inverter up to the 6-step inverter. The overmodulation range is divided into two modes depending on the modulation index(MI), In mode I, the reference angles are derived from the Fourier series expansion of the reference voltage corresponds to the MI. In mode II, the holding angles are also derived in the same way. Therefore, it is possible to obtain the linear control and the maximized utilization of PWM inverter output voltage.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.746-748
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• 1987

A volocity and an efficiency of an induction motor are lower than those of a DC motor. But in the control, the utility of an AC motor is more enlarged with the development of inverter. But unfortunately, in using the induction motor, it include a lot of harmonics because of switching of semi-conductor devices(SCR or Tr) in the inverter. In PCR, as the change of a firing angle $\alpha$, harmonics are changed. Hence, in this thesis analyze the harmonics and provide the region of it's application when PWM and 6-step applied to inverter. Of course, frequencies of inverter changed. Especially, in PWM a carrier ratio is changed.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.816-818
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• 2001

This paper shows the characteristic analysis for an inverter fed induction motor by the 2-D F.E.A. in variation of the air gap length. Harmonic effects of the induction rioter with different air gap length driven by the 6 step voltage of inverter ate investigated. And the results of the characteristic analysis on the inverter fed induction motor are compared with those of sinusoidal voltage fed motor.

• Journal of Information Processing Systems
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• v.18 no.6
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• pp.784-793
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• 2022

Grid-connected distributed power generation has been widely used in green energy generation. However, due to the distributed characteristics, distributed power generation is difficult to be dynamically allocated and monitored in the electrical control process. In order to solve this problem, this research combined the Internet of Things (IoT) with the automatic control system of electrical engineering to improve the control strategy of the power grid inverter according to the characteristics of the IoT system. In the research, a connection system of the power grid inverter and the IoT controller were designed, and the application effect was tested by simulation experiments. The results showed that the power grid inverter had strong tracking control ability for current and power control. Meanwhile, the electrical control system of the IoT could independently and dynamically control the three-phase current and power. The given value was reached within 50 ms after the step signal was input, which could protect the power grid from being affected by the current. The overall system could realize effective control, dynamic control and protective control.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.6
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• pp.579-587
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• 1992

This paper is to study on the step-up DC-DC converter for power system which yields output characteristics of low voltage and high current, such as fuel cell generation system. DC-AC-DC scheme is suggested for high ratio of voltage conversion. Three phase MOSFET-SPWM inverter is adopted for intermediate AC conversion and inverter output frequency is chosen at 400[Hz] in order to reduce the size of magnetic circuit and DC filter. Since control strategy which combines voltage controller with current controller in parallel is used, good output performance is obtained both in steady state and in transient state like load variation, not only in single unit operation but also in parallel operation.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.6
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• pp.434-440
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• 2023

This paper propose the method that measure the main system parameters for current control of a.c. motor adopting the vector control technique. The automatical method that tuning PI control gains for current control of servo motors are used frequently through the information of main system parameters, wire resistance and inductance. In this study, the techniques to measure these two system parameters through the control of 3-phase inverter are presented. These control and measuring method are implemented by measuring output phase current obtained as a results of the step current control using simple proportional feedback input. Moreover, this method use freewheeling current of inverter at special switching mode for measuring inductance. This analytic strategy is could measure and calculate the system parameters without the complex measurement algorithm and new additional measuring circuits. That is could measure the total resistance and total inductance including wiring resistance and conduction resistance of switching devices using real driving circuits to control the motors.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.491-499
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• 1999

This paper is on the high perfonnance propulsion IGBT VVVF inverter adopted new technique for railways. To prove the high performance and stabilit~r of traction, running tests are carried out under the simulated condition alike real field. The tests are perfonned on not only a steady states but also a transient states such a as input voltage variation using inertia load equivalent to 160tons train. The vector control technique is a adopted to improve traction for 4 motors. The low switching synchronous PW1\l method based on a space v voltage vector modulation is pro\XlSed as the optimal method for propulsion system railway. The output voltage l is controlled continuously to six step by prolxlsed ovennodu]ation technique without sudden torque variation.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.472-480
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• 2009

This paper describes the overmodulative SVPWM technique and harmonics analyses of three phase NPC type three-level inverter to the modulation index. Three phase NPC type three-level inverter adopted SVPWM to extend the linear region to 0.907, moreover, the following voltage compensation using Fourier series was adopted in the region of overmodulation to make it work to six-step level. PD type of multi carrier method is used with the double Fourier series for the analysis of output power harmonics characteristic. Simulation was performed by PSIM, and the harmonics characteristics of 3-level inverter in each region are analyzed. The side band harmonics of carrier frequency are dominant in the linear region, but these harmonic components are decreased as the inveter goes to overmodulation region, and the harmonics due to the fundamental frequency is increased gradually at the same time. The harmonic analyses are verified through the simulation and experimental results under the same condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.7
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• pp.1055-1061
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• 2002

This paper deals with a design and fabrication of an electronic ballast for 70[W] ceramic discharge metal halide lamps. The proposed ballast is composed of a rectifier, an active power factor correction circuit (PFC), a half-bridge inverter, a LC resonant circuit and a microprocessor. The developed ballast also includes a specially designed time circuit which provides reignition signal of lamps. Running frequency of the ballast is .jet at 40[kHz] to avoid acoustic-resonance and flickering. From the experimental results, input power factor and efficiency of the ballast are estimated 99.8[%] and 93.1[%], respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.273-276
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• 2005

This paper presents an electronic ballast using a step down converter, a low frequency inverter for high pressure discharge lamp. The proposed ballast is composed of a full-wave rectifier, a step down converter operated as a current source with power regulation and a low frequency inverter with ignition circuit. The ignition circuit generates high voltage pulse of 1${\sim}$2[kV] peak, 130[Hz]. Moreover, it is able to reignite at regular intervals by protective circuit. As experimental results on the test, lamp voltage, current and consumption power are measured 132.5[V], 7.6[A] and 1,005[W], respectively. It was confirmed that the designed ballast operate the lamp with a constant power.