• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.3
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• pp.17-26
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• 2005

The random pulse width modulation(RPWM) in inverter-fed induction motor drive is presented. This paper describes a RPWM method based on space vector PWM strategy for shaping the switching noise spectrum in such a way it can merge with the natural system noise. To verify the validity of the proposed RPWM scheme, the experiment based on the DSP56F803 microprocessor was executed finally, the simulation and experimental results will be given to demonstrate the effectiveness of the unposed RPWM scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1174-1181
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• 2005

The exact bit error rate(BER) calculation of an UWB-TH PPM multiple access communication system, which is known to be suitable for the fast transmission of massive information data, is introduced. The statistic feature of the multiple access intereference (MAI) of the system is precisely modeled by the characteristic function technique. The concrete expression for the MAI allows the exact expression for BER to be derived. In addition, we propose the approximate expression for the BER which reveals superior accuracy to the expression from the previous Gaussian approximation of the MAI. The validity of the proposed expressions is confirmed from the comparison of proposed results with the results from Monte-Carlo simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.927-933
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• 2014

Ship Power Management System(SPMS) based on Communication Network(CN) is one of the most significant factor for a safe voyage. Therefore, most of the vessels are using greater capacity generator than necessary to prevent pulsating load for safety purposes. However, It provokes low-load damage and reduces generator efficiency that using large capacity generator. Accordingly, in this paper propose hybrid power system for prevent damage of pulse load. Simulation using NI's LabVIEW was conducted for the design of the power system based on actual navigation data of the ship. Also, propose applying methods for hybrid power system in connection with the auxiliary power system for safe navigation.

• Journal of Power Electronics
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• v.16 no.2
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• pp.542-552
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• 2016

Central 60° synchronous modulation is an easy pulse-width modulation (PWM) method to implement for the traction inverters of urban rail trains at a very low switching frequency. Unfortunately, its switching patterns are determined by a Fourier analysis of assumed steady-state voltages. As a result, its transient responses are not very good with over-currents and high instantaneous torque pulses. In the proposed solution, the switching patterns of the conventional central 60° modulation are modified according to the dynamic error between the target and actual stator flux. Then, the specific trajectory of the stator flux and current vector can be guaranteed, which leads to better system transients. In addition, stator flux control is introduced to get smooth mode switching between the central 60° modulation and the other PWMs in this paper. A detailed flow chart of the control signal transmission is given. The target flux is obtained by an integral of the target voltage. The actual PMSM flux is estimated by a minimum order flux state observer based on the extended flux model. Based on a two-level inverter model, improved rules in the α-β stationary coordinate system and equations of the switching patterns amendment are proposed. The proposed method is verified by simulation and experimental results.

• Journal of Power Electronics
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• v.16 no.2
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• pp.490-497
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• 2016

The analysis of the switch status of each unit module of a cascaded multi-level inverter reveals that the working condition of the switch of a chopper arm causes unnecessary switching under the conventional unipolar sinusoidal pulse width modulation (SPWM). With an increase in the number of cascaded multilevel inverters, the superposition of unnecessary switching gradually occurs. In this work, we propose an improved SPWM strategy to reduce switching in cascaded multilevel inverters. Specifically, we analyze the switch state of the switch tube of a chopper arm of an H-bridge unit. The redundant switch is then removed, thereby reducing the switching frequency. Unlike the conventional unipolar SPWM technique, the improved SPWM method greatly reduces switching without altering the output quality of inverters. The conventional unipolar SPWM technique and the proposed method are applied to a five-level inverter. Simulation results show the superiority of the proposed strategy. Finally, a prototype is built in the laboratory. Experimental results verify the correctness of the proposed modulation strategy.

• Journal of IKEEE
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• v.24 no.3
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• pp.814-820
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• 2020

In the M-ary DCSK system up to now, as M increases, the distance between constellation signal points becomes closer and performance deteriorates. we propose a hybrid modulation scheme based on PPM and DCSK to improve the BER performance. one part of the bit is modulated by the PPM and the other part by DCSK. Thus, the information bearing signal is modulated simultaneously according to the selected pulse position of the PPM determined by the information bit and the additional information bit. The analytical BER performance of the proposed plan is derived and verified by simulation. The results show that the proposed scheme outperforms conventional M-DCSK, code index modulation DCSK and rectified code index DCSK in additional white Gaussian noise and multipath Rayleigh fading channels.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.15-16
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• 2010

This paper is study on a high efficiency DC-DC converter of discontinuous conduction mode (DCM) added electric isolation. The converters of high efficiency are generally made that the power losses of the used semiconductor switching devices is minimized. To achieve high efficiency system, the proposed converter is constructed by using a quasi resonant circuit. The control switches using in the converter are operated with soft switching by quasi resonant method. The control switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the efficiency of the system is high. The proposed converter is also added electric isolation which is used a pulse transformer. When the power conversion system is required electric isolation, the proposed converter is adopted with the converter system development of high efficiency. The soft switching operation and the system efficiency of the proposed converter are verified by digital simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.5
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• pp.376-380
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• 2010

This paper presents a circuit configuration of multilevel inverter to increase the number of output voltage levels by using conventional 5-level inverters connected in series. Most of all it can maximize the number of output voltage levels by employing input voltage sources, which have the power of five. When it synthesizes the same number of output voltage levels, the proposed inverter can save the number of switching devices compared with the conventional cascaded H-bridge cell inverter. So it can reduce the size, cost, power consumption of the system. We implemented computer-aided simulation and experiments for a 25-level inverter employing two 5-level inverters.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1186-1194
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• 2017

This paper proposes an improved low frequency Selective Harmonic Mitigation-PWM (SHM-PWM) technique. The proposed method mitigates the low order harmonics of the output voltage up to the $50^{th}$ harmonic well and satisfies the grid codes EN 50160 and CIGRE-WG 36-05. Using a modified criterion for the switching angles, the range of the modulation index for non-linear SHM equations is improved, without increasing the switching frequency of the CHB converter. Due to the low switching frequency of the CHB converter, mitigating the harmonics of the converter up to the $50^{th}$ order and finding a wider modulation index range, the size and cost of the passive filters can be significantly reduced with the proposed technique. Therefore, the proposed technique is more efficient than the conventional SHM-PWM. To verify the effectiveness of the proposed method, a 7-level Cascaded H-bridge (CHB) converter is utilized for the study. Simulation and experimental results confirm the validity of the above claims.

• Journal of Power Electronics
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• v.18 no.3
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• pp.789-801
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• 2018

Model predictive direct power control (MPDPC) is a widely recognized high-performance control strategy for a three-phase grid-connected pulse width modulation (PWM) rectifier. Unlike those of conventional grid-connected PWM rectifiers, the active and reactive powers of permanent magnet synchronous generator (PMSG)-connected PWM rectifiers, which are used in electromagnetic transmitters, cannot be calculated as the product of voltage and current because the back electromotive force (EMF) of the generator cannot be measured directly. In this study, the predictive power model of the rectifier is obtained by analyzing the relationship among flux, back EMF, active/reactive power, converter voltage, and stator current of the generator. The concept of duty cycle control in the proposed MPDPC is introduced by allocating a fraction of the control period for a nonzero vector and rest time for a zero vector. When nonzero vectors and their duration in the predefined cost function are simultaneously evaluated, the global power ripple minimization is obtained. Simulation and experimental results prove that the proposed MPDPC strategy with duty cycle control for the PMSG-connected PWM rectifier can achieve better control performance than the conventional MPDPC-SVM with grid-connected PWM rectifier.