• Journal of Power Electronics
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• v.16 no.6
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• pp.2067-2075
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• 2016

Cascaded H-bridge multilevel inverters are currently used because it enables the integration of various sources, such as batteries, ultracapacitors, photovoltaic array and fuel cells in a single system. Conventional modulation schemes for multilevel inverters have concentrated mainly on the generation of a low harmonic output voltage, which results in less effective utilization of connected sources. Less effective utilization leads to a difference in the charging/discharging of sources, causing unsteady voltages over a long period of operation and a reduction in the lifetime of the sources. Hence, a charge balance control scheme has to be incorporated along with the modulation scheme to overcome these issues. In this paper, a new approach for charge balancing in symmetric cascaded H-bridge multilevel inverter that enables almost 100% charge balancing of sources is presented. The proposed method achieves charge balancing without any additional stages or complex circuit or considerable computational requirement. The validity of the proposed method is verified through simulation and experiments.

• Journal of Power Electronics
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• v.16 no.3
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• pp.915-924
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• 2016

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1177-1181
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• 2000

Usually, in many applications. high frequency resonant inverters are used, and the PAM(Pulse Amplitude Modulation), PFM(Pulse Frequency Modulation) or PWM(Pulse Width Modulation) techniques are used to control the output power of resonant inverters. And the resonant inverters have to control the output frequency for the reliable operation under the variable load conditions. In this paper, a new switching scheme is proposed as a resonant frequency following control of resonant inverters. With the proposed method. it can be obtained that optimum resonant frequency and unity output displacement factor under the variable resonant frequency adaptively. The detail algorithm of the proposed switching scheme and its characteristics are discussed. And the veridity of the proposed method is confirmed with the experimental results.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.9
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• pp.1239-1246
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• 1995

A forced commutated cycloconverter (FCC) is a direct ac-ac converter capable of providing simultaneous voltage and frequency transformations. In this paper, vector control of an induction motor controlling stator current with forced commutated cycloconverter is presented. The advantage of current control is that the stator dynamics are eliminated and high performance vector control can be achieved. A novel modulation method based on dq transformation techniques is presented. Proposed modulation strategy generates the low frequency modulation function by the instantaneous value of the desired output voltages not by the steady state values of output magnitude and output frequency. PI control and predictive control algorithm for current control are applied, and the validity of proposed method is confirmed through digital simulations. Simulation results of step response and torque distubance and current control are presented.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.17-18
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• 2013

To minimize construction of nuclear facility, it is required to reduce reinforcing bar amount and solve reinforcing bar concentration and for this, it is necessary to develop appication design technology and modular of high strength reinforcing bar. Hence, KHNP reduces excessive reinforcing bar amount which can cause possibility of poor construction of concrete through design standard development and modular of nuclear facility structure using high strength reinforcing bar to raise economics and has its purpose to maintain high-level safety and durability as they are. This study is to introduce application method for the Rebar Modulation of High-Strength Reinforcing Bars to the Nuclear Power Plant Structures.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.16-18
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• 2008

A novel general direct duty ratio pulse width modulation strategy is proposed to modulate matrix converters. By using average concept over one switching period, the modulation algorithm and the required equations are derived to synthesize the desired output voltage and to achieve the controlled input power factor. The proposed method use continuous carrier and the predetermined duty ratio signal for directly generating gating signals an thus is named "direct duty ratio PWM(DDPWM)". The feasibility and validity of the proposed strategy are verified by experimental results.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.739-741
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• 1993

This paper deals with the Improvement of inverter output waveform with space vector modulation using the DSP-chip. The proposed scheme can be considered as a alternative of the conventional, subharmonic method. This scheme features a maximum output voltage that is 15% greater. The number of switchings is also 30% less than the one obtained by subharmonic modulation method(SHM) A performance function(PF) which is the time integral function of the inverter output voltage is introduced in this paper. An optimal PWM pattern is obtained by minimizing the distortion factor of performance function. The experiment was carried out with an TMS320C25.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.6
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• pp.303-309
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• 2014

Chaos communication system can improve a system security due to characteristics of non-periodic, non-predictability, broadband signal and easy implementation. Also, chaos signal is sensitive to initial conditions of chaos map. By these reasons, security of chaos communication system is superior to digital communication system. BER performance of COOK modulation system is better than other chaos modulation systems, even if COOK modulation system uses an asynchronous receiver. However, security and safety of COOK modulated signal are worse than other chaos modulation systems, because information bits can be easily predicted from COOK modulated signal. In this paper, for security improvement of COOK modulated signal, we propose a novel Scrambling COOK modulation system by applying the scrambling method. Conventional COOK modulated signal can be predicted, because chaos signal is generated when data is only 1. However, proposed system cannot be predicted, because chaos signal is generated when data is 0 or 1. Therefore, security and safety of transmitted signal in scrambling COOK modulation system is superior to conventional COOK modulation system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.4
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• pp.22-30
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• 2008

In this paper, we deal with modulation classification method using WT capable of classifying incident digital signals without a priori information. These key features should have good properties of sensitive with modulation types and insensitive with SNR variation. The 4 key features for modulation recognition are selected using WT coefficients, which have the property of insentive to the changing of noise. The numerical simulations for classifying 8 digital modulation types using these features are peformed. The numerical simulations of the 3 types (i.e. DTC, MDC, and SVMC) of modulation classifiers are performed the investigation of classification accuracy and execution time to design the modulation classification module in software radio. The simulation result indicated that the execution time of MDC and DTC was best and MDC and SVMC showed good classification performance.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.3
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• pp.133-139
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• 2003

In this paper, a new control scheme of Class-E inverter for Induction Heating (IH) Jar applications with clamped voltage characteristics using Pulse-Frequency-Modulation (PFM) is introduced. To reduce the voltage stress of switch, the proposed PFM control scheme doesn't need any auxiliary circuit in comparison to a family of Active Clamped Class-E (ACCE) inverter. It can decrease voltage stress of switch through modulation of switching frequency. The Class-E inverter using the proposed control scheme has the advantage of not only the same output power when it is compared with a Hybrid-Active Clamped Class-E (Hybrid-ACCE) inverter but also Zero-Voltage-Switching (ZVS), which are characteristics of conventional Class-E and ACCE inverter. The control principles and analysis of proposed method are explained in detail and its validity is verified through simulation and experimental results.