• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1041-1044
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• 1992

A solar cell should be operated at the maximum output point on the I-V characteristic curve with constant current and constant voltage in order that the solar energy be fully utilized. According to, in this paper, we describes a controller which can track the maximum power point of a solar arry using current and voltage ripple variation of step up chopper system. The control circuit is desinged such that actual current and voltage are sensed directly from the solar cell array. These two signal are then holded sampling and multiplies by a single chip multiplier.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.329-334
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• 2001

This paper presents exact autotransformer-fed AC electric railroad system modeling using constant current mode. The theory is based on the solution of algebraic. The proposed modeling is considered the line self-impedances and mutual-impedances. Besides, the load modeling improved results are obtained as application to the proposed constant current mode. In the analysis on AT-fed AC electric railroad system circuit, a generalized analysis method using the loop equation on a case by case. the simulation objectives are to calculate the catenary and rail voltages with respect to ground, as the train moves along a section of line between two adjacent ATs. The model contains assumptions regarding the representation of the autotransformer, the impedance of the track/catenary system, and the grounding arrangements, which all effect the accuracy of the result. The modeling results seem very reasonable. It is established that techniques for the AC electric railroad system modeling and analysis.

• Journal of Power Electronics
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• v.2 no.3
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• pp.155-161
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• 2002

This paper presents a maximum power point tracking algorithm for Photovoltaic array using only instantaneous output current information. The conventional Hill climbing method of peak power tracking has a disadvantage of oscillations about the maximum power point. To overcome this problem, we have developed an algorithm that will estimate the duty ratio corresponding to maximum power operation of solar cell. The estimation of the optimal duty ratio involves, finding the duty ratio at which integral value of output current is maximum. For the estimation, we have used the well know Lagrange's interpolation method. This method can track maximum power point quickly even for changing solar isolation and avoids oscillations after reaching the maximum power point.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4112-4118
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• 2011

Electrical Railroads provide electric power, which can operate vehicles, via feeder wires. And the supplied current returns to the transformer substation through lines and ground net. The return current, related to signal, power and power line, and track circuit systems, is one of the most important component in the electric railway. Therefore, to prevent system faults and breakdown according to unbalance and overcurrent of the return current, various and detailed analyses for the return current are needed. In the paper, we present measurement and analysis manners in real environment and evaluate its safety. For analysis, we utilize the measured values of return currents measured in track circuits in electric railway. we expect that this research plays a key role to the related fields.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.1
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• pp.15-24
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• 2012

In this paper, we suggest the dynamic-response-free SMPS using a new high-resolution DPWM generator based on switched-capacitor delay technique. In the proposed system, duty ratio of DPWM is controlled by voltage slope of an internal capacitor using switched-capacitor delay technique. In the proposed circuit, it is possible to track output voltage by controlling current of the internal capacitor of the DPWM generator through comparison between the feedback voltage and the reference voltage. Therefore the proposed circuit is not restricted by the dynamic-response characteristic which is a problem in the existing SMPS using the closed-loop control method. In addition, it has great advantage that ringing phenomenon due to overshoot/undershoot does not appear on output voltage. The proposed circuit can operate at switching frequencies of 1MHz~10MHz using internal operating frequency of 100 MHz. The maximum current of the core circuit is 2.7 mA and the total current of the entire circuit including output buffer is 15 mA at the switching frequency of 10 MHz. The proposed circuit has DPWM duty ratio resolution of 0.125 %. It can accommodate load current up to 1 A. The maximum ripple of output voltage is 8 mV. To verify operation of the proposed circuit, we carried out simulation with Dongbu Hitek BCD $0.35{\mu}m$ technology parameter.

• Journal of the Korean Society for Railway
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• v.12 no.3
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• pp.405-411
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• 2009

Railway signaling system in a rapid transit using the ATC system the approved a speed limit to a train and a part of signaling system in a metro approved a distance which is possible to move. Referring to the way of transmitting train control information, there are the one transmitting it to the on-board system of a train using the direct track, the another transmitting it establishing an instrument, and the other transmitting an instrument by a railway track. The one is the method using the direct track as a conductor for composing the part of the track and attaining the information controlling a train by transmitting a signal to the track. It is used for the high-speed railway and the subway. The method using the track attains information by transmitting it to returned information, and the on-board system of a train attains it by magnetic coupling. Because many reinforcing bars on the concrete slab track are used, interaction between a rail and a reinforcing bar that is not produced on ballast track is made. Due to the interaction, the electric characteristic of rail is changed. In the current paper, we numerically computed the coupling coefficient between the rail and the reinforcing bar based on the concrete slab track throughout the model related to the rail and the reinforcing bar using the concrete slab track that is used in the second interval of the Gyeongbu high-speed railway, and we defined the coupling coefficient not changed in the electric characteristic of rail in the condition that there is no interaction between the rail and the reinforcing bar.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1989-2000
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• 2015

In this paper, digital peak current mode control for single phase H-bridge inverters is developed and implemented. The digital peak current mode control is achieved by directly controlling the PWM signals by cycle-by-cycle current limitation. Unlike the DC-DC converter where the output voltage always remains in the positive region, the output of DC-AC inverter flips from positive to negative region continuously. Therefore, when the inverter operates in negative region, the control should be changed to valley current mode control. Thus, a novel control logic circuit is required for the function and need to be analyzed for the hardware to track the sinusoidal reference in both regions. The problem of sub-harmonic instability which is inherent with peak current mode control is also addressed, and then proposes the digital slope compensation in constant-sloped external ramp to suppress the oscillation. For unipolar PWM switching method, an adaptive slope compensation in digital manner is also proposed. In this paper, the operating principles and design guidelines of the proposed scheme are presented, along with the performance analysis and numerical simulation. Also, a 200W inverter hardware prototype has been implemented for experimental verification of the proposed controller scheme.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.802-810
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• 2006

For a thorough train control, the precise train position detection is necessarily required. The widely used current way for train position detection is the one of using track circuits. The track circuit has a simple structure, and has a high level of reliability. However trains can be detected only on track circuits, which have to be installed on all ground sections, and much amount of cost for its installation and maintenance is needed. In addition, for the track circuit, only discontinuous position detection is possible because of the features of the closed circuit loop configuration. As the recent advances in telecommunication technologies and high-tech vehicle-based control equipments, for the train position detection, the method to detect positions directly from on trains is being studied. Vehicle-based position detection method is to estimate train positions, speed, timing data continuously, and to use them as the control information. In this paper, the features of GPS navigation and DR navigation are analyzed, and the navigation filters are designed by constructing vehicle-based train position detection method by combining GPS navigation and DR navigation for their complementary cooperation, and by using kalman filter. The position estimation performance of the proposed method is also confirmed by simulations.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.948-953
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• 2011

In AC railway feeding system, three phase received from the network is changed to two phase power sources with different phases. The main circuit breaker installed train is automatically open by track signal when the train passes the neutral section. In order to continuously supply power source to train, the changeover system was used in Japan. Therefore, the train is able to operate under powering condition when it was passing through the neutral section. We investigated the control method to reduce the inrush current flowing main transformer in train. To examine the inrush current and operate the static semiconductor switch such as thyristor, we manufactured the small scale the changeover system and carried out performance tests.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.185-187
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• 2008

This paper proposed design and development of a photo voltaic (PV) array fed induction motor drive. A drive system using a chopper circuit to track maximum power from the PV for different solar insolation and a current controlled voltage source inverter (CC-VSI) to optimally match the motor to PV characteristics is presented. The model equations governing interaction of torque and flux producing components of motor current with available solar power is developed for the operation of the system at optimum efficiency. Performance of the system is presented for different realistic operating conditions, which demonstrates its special features for applications such as solar water pumping system, solar vehicles and floor mills located in hilly and isolated areas.