• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.170-175
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• 2003

A control algorithm is developed for highly efficient operation of auxiliary power unit (APU) that consists of a diesel engine and a directly coupled induction generator in series hybrid electric Bus (SHEB). In a series hybrid configuration the APU supplies the electric power needed for maintaining the state of charge (SOC) of the battery unit in various conditions of vehicle operation. As the rotational speed of generator does not depend on the vehicle speed, an optimized operation of engine-generator unit based on the efficiency map of each component can be achieved. The output torque of diesel engine can be controlled by the amount of fuel injection, and the power converted from mechanical to electrical energy can be adjusted by generate control unit (GCU) using the decoupling vector control of torque and flux. As for the given reference of the generating power, the multiply of speed and torque, many combinations of operating speed and torque are possible. The algorithm decides the new operating point based on the engine efficiency map and generator characteristic curve. During the transition of operating points, the speed controller saturation is avoided using variable limit and filtering of generator torque reference. A test rig and SHEB consist of a 1.5L diesel engine and a 30kw induction generator are constructed by Hyundai Motor Company.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.1
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• pp.1-9
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• 1990

The structure of A matrix of one machine connected to the infinite bus is described for a full model. The A matrix can be partitioned to submatrices which depend on the initial operating point and do not depend on it. When the dynamic properties for several different operating points are desired, those submatrices can be obtained through simple column operation. Furthermore, the elements of A matrix can be directly calculated from the manufacturer's data. RMS quantities of the state variables for the initial operating point are used. This approach can save the labor for calculating the elements of A matrix for the dynamic stability analysis.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.185-187
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• 2000

Fault current is flowed into 154/23kV M. Tr when line-to-ground fault occurs in power system. NGR(Neutral Grounded Reactor) is set up in order to prevent M.Tr fault by limiting magnitude of fault currents. Here, disconnection of NGR causes voltage increase by L-C resonance and line-to-ground fault in an unearthed system results in voltage increase at healthy phases. So Over Voltage Ground Relay(OVGR) is used for tripping M.Tr. Also, buses at second phases of M.Trs are all connected with section circuit breakers closed for the purpose of parallel operation and load shedding. In case of speciality buses are comprised of power cable in part for GIS connection. When no-load charged cable or bus is open by a section CB, unbalanced voltage charged on the bus is induced. Also discrepant opening time for circuit breakers on different phases gives rise to unbalanced zero sequence voltage. It was observed that this zero sequence voltage detected in the 22.9kV P.T (Potential Transformer for bus) mal-operated 59GT and tripped M.Tr. The zero sequence voltage of which vanishing time is longer than relay operating time came out by EMTDC simulation. Also, it was shown that the voltage waves of actual test are similar to those of simulation. On the basis of above results, R-C circuit complement on the relay without any effect on a power system made operating time of the relay longer than vanishing time of distorted waves. Consequently, operating time of the relay was delayed and magnitude of distorted waves was decreased by increasing time constant of the relay.

• Journal of Korean Society of Transportation
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• v.26 no.6
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• pp.61-70
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• 2008

The study proposed a new type of bus information, Real-time Bus Crowdedness (RBC) information, to meet various demands of users and improve the convenience level of using public transportation, while existing bus information provided by bus information systems(BIS) were limited to bus operating information such as predicted bus arrival time. To analyze the impacts of providing the proposed RBC information, stated preference(SP) survey was performed and a methodology of disaggregate analysis (e.g., binary logit) was applied to develop passenger choice models. Additionally, passenger choice models incorporating the heterogeneity of different user groups(i.e., by age or trip purposes) were developed to evaluate the different responses on RBC information. The results showed that providing RBC information was significantly related to users' bus choices and the responses of user groups were significantly different, especially the age group of more then 60 was most affected by the RBC information on their bus choices. Also trip purposes were significantly related to users' bus choices, for instance the impacts of providing RBC information was bigger for non-business trips(leisure/meet friend/personal business, shopping, hospital) compared to business trip.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.584-590
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• 2009

Since driving include compilcated actions that require a variety of abillity and cause extrme concentration or strain, divers tend to feel tired easiy. However, divers can't recognize fatigue degree by himself and accordingly the methods to measure quantitative fatigue degree exactly is quite difficult to be secured. In this study, the most efficient driving posture was suggested based on the analysis of quantitative muscular strength and fatigue degree according to posture. The driver whom we experimented included 9 commercial bus drivers. We also analyzed quantitative legs' muscular strength according te operating each pedal, left and right then we analyzed muscular strength and muscular fatigue degree according to driving pattern while driving commercial buses. And then we suggested the most efficient driving posture.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.859-862
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• 2003

This paper proposes an emulation environment for SoC designs using small number of large gate-count FPGA's and a PC system. To overcome the pin limitation problem in partitioning the design when the design size overwhelms the FPGA gate count, we use bus splitter modules that replicate on-chip bus signals in one FPGA to arbitrary number of other FPGA's with minimal pin count. The proposed scheme is applied to the emulation of 2 million gate multimedia processing chip using two Xilinx Viretex-2 6000 FPGA devices in 6.6MHz operating frequency. An ARM core, memories, camera and LCD display are modeled in software using dual 2GHz Pentium-III processors. This scheme can be utilized for more than 2 FPGA's in the same ways as two FPGA case without losing emulation speed.

• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.593-598
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• 2008

The power distribution is proposed to determine the target operating points of the system components as the basis for maximal the efficiency of the overall system for a power split dual electric machine hybrid electric bus. The coordinated control is constructed on the basis of the power distribution. The basic coordinated control is implemented to satisfy the driver's power demand, in which both the dynamic characteristics of the engine and the dual electric machine are explicitly taken into account. Moreover, the improved coordinated control is suggested to suppress engine dynamic operation and rich fuel injection.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.302-310
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• 2011

Congestion management is one of the most challenging tasks of a system operator to ensure the operation of transmission system within operating limits. In this paper, cluster/zone method and relative electrical distance (RED) method for congestion management are compared based on the considered parameters. In the cluster/zone method, rescheduling of generation is based on user impact on congestion through the use of transmission congestion distribution factors. In the RED method, the desired proportions of generations for the desired overload relieving are obtained. Even after generation rescheduling, if congestion exists, load curtailment option is also introduced. Rescheduling cost, system cost, losses, and voltage stability parameter are also calculated and compared for the above two methods of congestion management. The results are illustrated on sample 6-bus, IEEE 30-bus, and Indian utility 69-bus systems.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.2
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• pp.113-118
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• 1999

In this, sensitivity based approach to estimate BITC(bilateral interchange transfer capacity) considering the real power flow control function of FACTS devices is presented. The real power flow setting of the FACTS devices is adjusted so that it transfers the power flow from the first violation point of transmission capacity to other transmission lines in the power system, thus allowing more power to be transferred from the specified generator bus to the specified load bus. The transfer between the two bus locations is increased from this new operating condition until a violation of transmission capacity limits occurs or until the setting of the FACTS devices can no longer be adjusted. The proposed algorithm is illustrated using examples of small and real life power system.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.880-883
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• 1998

In this paper, sensitivity based approach to estimate BITC(bilateral interchange transfer capacity) considering the real power flow control function of FACTS device is presented. The real power flow setting of the FACTS device is adjusted so that it transfer the power flow from the first violation point of transmission capacity to other transmission lines in the power system, thus allowing more power to be transferred from the specified generator bus to the specified load bus. The transfer between the two bus locations is increased from this new operating condition until a violation of transmission capacity limits occurs or until the setting of the FACTS device can no longer be adjusted. The proposed algorithm is illustrated using examples of small and real life power system.