• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.126-131
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• 2001

This paper deals with implementation of inverter systems for DC power regeneration, which can regenerate the excessive DC power from DC bus line to AC supply in substations for traction systems. From the viewpoint of both power capacity and switching losses, a three-phase square-wave inverter system is adopted. To control the regenerated power, the magnitude and phase of fundamental output voltages should be appropriately controlled in spite of the variation of input DC voltage. Inverters are operated with modified a-conduction mode to fix the potential of each arm. The overall system consists of the line-to-line voltage and line current sensors, an actual power calculator using d-q transformation method, a complex power controller with PI control scheme, a gating signal generator for modified $\alpha-conduction\;mode\;with\;\delta\;and\;\alpha$, a DPLL for frequency followup, and power circuit.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.30-33
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• 2001

도시철도 DC 급전시스템은 부하전류가 사고전류보다 클 수 이는 특징을 가지고 이다. 이러한 이유로 DC 급전시스템에서는 di/dt를 측정하여 사고전류를 부하전류로부터 구분하고 있다. 이것은 사고전류의 di/dt와 부하전류의 di/dt는 서로 다른 상이한 특성을 보이고 있기 때문이다. 본문에서는 DC도시철도급전시스템에서 흔히 사용되는 di/dt 계전기와 이의 설정을 위한 사고전류의 분석 및 설정방법에 대해 알아본다.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.800-805
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• 2005

In this study, control schemes are proposed for a propulsion system of TTX(Tilting Train eXpress). In developed traction converter, unity power factor control, compensation method of dc link voltage have been applied. Output current of converter contains harmonic ripple at twice input ac line frequency, which causes a ripple in the dc link voltage so that beatless control is developed in inverter system to reduce the pulsating torque current. This system is verified by the system modelling and prototype test.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.410-415
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• 2001

This paper proposes a new control scheme for the power factor improvement of DC power regenerating systems, which can regenerate the excessive DC power from DC bus line to AC supply in substations for traction systems. From the viewpoint of both power capacity and switching losses, the system is designed on the basis of three-phase square-wave inverters and composed of two inverters, zig-zag connected output transformers, and an AC filter. The output voltages of the regenerating system are not sinusoidal. However, regenerated complex power is analyzed on the basis of fundamental components and thus the reactive power produced by harmonics is not considered. Therefore, it is needed a new control scheme capable of controlling the reactive power nearly to zero even for nonsinusoidal cases. To verify the validity of the proposed control scheme, computer simulations are carried out. And the results show that the power factor is theoretically higher than 0.99.

• Proceedings of the KSR Conference
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• 2006.05b
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• pp.1215-1220
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• 2006

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.351-354
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• 2000

This paper deals with the voltage amplitude control in inverter systems which can regenerate the excessive DC power from DC bus line to AC supply in substations for traction systems. To maintain the magnitude of output fundamental voltage constant in spite of the variation of input DC voltage inverters are operated in symmetrical $\alpha$-conduction mode with the range of $120^{\circ}$<$\alpha$<$180^{\circ}$ To match the output voltage of the inverter systems with AC supply voltage harmonic reduction techniques are also investigated. Computer simulations are carried out to verify the validity of the proposed systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.493-500
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• 2000

The battery charger for high speed trail car is very important power source for the purpose of safety and system stability It provides control power of VVVF, CVCF, DC/DC converter and inverter for traction motor. This paper included power circuit of the ZVZCS type battery charger for high speed trail car and battery charging algorithm. Also the optimum parallel operation of 50kW battery charger for high speed trail car, and charring control method of Ni-Cd battery illustrates validity and effectiveness through the experiments.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.676-681
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• 2005

The regenerative braked cars are being introduced in DC electric railway for energy saving. There has been a recent tendency for DC traction substation with regenerative inverter to increase in number. This is strongly related to the desire for effective utilization of electric power regenerated by DC electric cars and to the aim ensuring stable operation of regenerative braking system. The regenerative inverters DC power feed back from a generative car into AC power at a substation and supplies it to distribution lines. This paper suggest the result of characteristic analysis and capacity simulation. economical analysis in the regenerative inverter system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.680-685
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• 2011

Nowadays, in metropolitan railroad, DC feeding system is being generally applied. In order to reduce damages of electro-chemical corrosion caused by stray current and leakage current, in DC feeding system, rail is used as negative-polarity return conductor for traction load current. However, it has problem of rail potential increase and there are no adequate measures to prevent it in domestic. In this paper, we presented fundamental theory and related standards about rail potential increase. And then, we analyzed field testing data and simulated a variety of operations by using PSCAD/EMTDC as an analysis program of power system. In addition, voltage control device is suggested to prevent accidents caused by rail potential increase.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.88-89
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• 2017

This paper investigates the design of multi-winding coupled inductor for minimum inductor current ripple in rapid traction battery charger systems. Based on the general circuit model of multi-winding coupled inductor together with the operating principles of dc-dc converter, the relationship between the ripple size of inductor current and the coupling factor is derived under the different duty ratio. The optimal coupling factor which corresponds to a minimum inductor ripple current becomes -(1/n-1), i.e. a complete inverse coupling without leakage inductance, as the steady-state duty ratio operating point approaches 1/n, 2/n, … or (n1)/n. In an opposite manner, the optimal coupling factor value of zero, i.e. zero mutual inductance, is required when the steady-state duty ratio operating point approaches either zero or one.