• Journal of the Korean Society for Railway
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• v.15 no.4
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• pp.357-363
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• 2012

This paper presents a new operation method for the single phase PWM(Pulse Width Modulation) converter train. Recently, the trains adopting the PWM converter have become the majority in the electric locomotives since there are distinct advantages over the predecessors, which can be operated at near unity power factor. However, a slight modification of the control scheme makes this kind of vehicles run in the region of leading power factor. Although this feature seems to be of no significant use by itself, the leading phase operation can improve the voltage profile and the line loss of the feeding systems is decreased by compensating the reactive power loss along the line when it considered together with the feeding systems. This method is even more economical and efficient comparing with the installation of SVC that is mainly used for this purpose since the train can become a movable compensator. With the conditions and some essential formula for the leading phase operation, a new power factor control algorithm has been proposed to implement this scheme. The results of simulation through SIMULINK model show that the proposed method is suitable enough for practical use.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.142-148
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• 2006

In this paper, authors propose a novel step-up AC-DC converter operated with power factor correction (PFC) and with high efficiency. The proposed converter behaves with discontinuous current control (DCC) of input current. The input current waveform in the proposed converter is got to be a discontinuous sinusoid form in proportion to magnitude of at input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC converters, the switching devices are turned-on with the zero current switching (ZCS). But turn-off of the switching devices is done at the maximum current. To achieve a soft switching at turn-off, the proposed converter uses a new partial resonant circuit, which results in the very low switching loss and the high efficiency of converter.

• Journal of Electrical Engineering and Technology
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• v.2 no.2
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• pp.249-256
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• 2007

This paper presents a new circuit topology and its digital control scheme for a half-bridge resonant inverter. As the proposed half-bridge inverter can be operated in load-freewheeling modes, the pulse-width modulation (PWM) method can be used for the output power control. The proposed half-bridge inverter is based on the resonant frequency-tracking algorithm with the goal of maintaining the unity of the output displacement factor of the load impedance even in varying conditions. In this paper, the operation principle, electrical characteristics, and detailed digital control scheme of the proposed half-bridge resonant inverter are described. The experimental results of the prototype experimental setup to verify the validity of the proposed half-bridge inverter are presented and discussed.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.63-68
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• 2002

In a utility interactive photovoltaic generation system, a PWM inverter is used for the connection between the photovoltaic arrays and the utility. The do current becomes pulsated when the conventional inverter system operates in the continuous current mode and dc current pulsation causes the distortion of the ac current waveform. To reduce pulsation of dc input current, This paper presents a Buck-Boost PWM power inverter and its application for residential photovoltaic system. The PWM power inverter is realized by combining two sets of a high frequency Buck-Boost chopper and by making it operate in the discontinuous conduction mode. In this paper, we show the Buck-Boost PWM power inverter circuit, its equivalent circuit and basic differential equations and the power flow characteristics are clarified when the proposed Inverter is interconnected with the utility lines. In conclusion, the proposed inverter system provides a sinusoidal ac current for domestic loads and the utility line with unity power factor

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.7
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• pp.272-277
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• 1986

The system that follows to the resonance frequency of high frequency MOSFET inverter and varies according to the changes of load characteristics is proposed. Also we suggested a method how to select the resonant load type between series and parallel circuit for a given inverter type. It leads to the conclusion that in the case of high impedance loads, parallel resonant circuits are preferable, on the other hand, for low impedance loads, series resonant circuits are more preferable. For frequency tracking, a PLL circuit is used as main control element to detect the phase difference of current and voltage of load. The realized apparatus composed of control circuit and voltage type full-bridged MOSFET elements as main parts of inverter. A stable frequency follow-up characteristics are obtained for 1.2MHz, 1.5KW high frequency output and power is always supplied to the load with unity power factor.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.518-520
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• 1996

High frequency switching converters are becoming more popular because of several benefits which are essential in power conversion system. This paper introduces a high speed digital controller using TMS320C40 DSP chip which can be used for high frequency switching converters and demonstrates its performance by operating three-phase PWM AC/DC converter with unity power factor at 20kHz sampling frequency. TMS320C40 DSP chip operates with 40-ns instruction cycle times and is capable of 275 MOPS. The running time of real time control loop at the three-phase PWM AC/DC converter is $44.6{\mu}sec$.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.14-20
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• 1997

Due to several advantages of Pulse Width Modulated(PWM) Converter, such as unity power factor with low-harmonics and energy regeneration, PWM converter has been widely used in industrial application. In every application of energy conversion equipment, the design and implementation must be carried out considering performance and cost. High quality with low cost is the best choice for energy conversion equipment. High dc link voltage can reduce inverter and motor side losses and system dimension compare to low dc link voltage. Analog controller can make PWM converter cheaper without considerable degradation of the performance than digital controller. This paper shows the simplified analog controller-for 600V dc link voltage using stationary reference frame control and the simulation results.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1937-1939
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• 1998

This paper presents a simple switching method to generate a PWM pattern mostly relevant to signle-phase three-level PWM rectifier. The adopted PWM switching pattern is performed in a manner similar to the space vector PWM method, which is popularly used in the three-phase rectifier and inverter. A set of possible voltages has been selected so that an equation with a time integral considered within a sampling period should be satisfied every sampling time. The simulation result shows that the proposed control scheme is good in some performance criteria such as unity power factor, low harmonic distortion of input current, dynamic response and voltage balancing of two series-connected DC capacitors.

• International Journal of Control, Automation, and Systems
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• v.4 no.1
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• pp.113-123
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• 2006

In this paper, an improved direct torque control (DTC) method for sensorless matrix converter drives is proposed which enables to minimize torque ripple, to obtain unity input power factor, and to achieve good sensorless speed-control performance in the low speed operation, while maintaining constant switching frequency and fast torque dynamics. It is possible to combine the advantages of matrix converters with the advantages of the DTC strategy using space vector modulation and a flux deadbeat controller. To overcome the phase current distortion by the non-linearity of a matrix converter drive, the simple non-linearity compensation method using PQR power theory are presented in the proposed scheme. Experimental results are shown to illustrate the feasibility of the proposed strategy.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.278-281
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• 1999

In a utility interactive photovoltaic system, a PWM inverter is used for the connection between the photovoltaic arrays and the utility. The DC current becomes pulsated causes the distortion of the AC current waveform. This paper presents the reduced pulsation of DC input current by operating the inverter with buck-boost chopper in the discontinuous conduction mode. The DC current with contains harmonics component is analyzed by means of separating into two terms of a ripple component and a direct component. The constant DC current without pulsation is supplied from photovoltaic array to the inverter. The proposed inverter system provide a sinusoidal AC current for domestic loads and the utility line with unity power factor.