• 대한전기학회논문지:시스템및제어부문D
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• 제51권6호
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• pp.241-251
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• 2002

The effect of sensor faults in direct torque control(DTC) based induction motor drives is analyzed and a new Instrument fault detection isolation scheme(IFDIS) is proposed. The proposed IFDIS, which operated in real-time, detects and isolates the incipient fault(s) of speed sensor and current sensors that provide the feedback information. The scheme consists of an adaptive gain scheduling observer as a residual generator and a special sequential test logic unit. The observer provides not only the estimate of stator flux, a key variable in DTC system, but also the estimates of stator current and rotor speed that are useful for fault detection. With the test logic, the IFDIS has the functionality of fault isolation that only multiple estimator based IFDIS schemes can have. Simulation results for various type of sensor faults show the detection and isolation performance of the IFDIS and the applicability of this scheme to fault tolerant control system design.

• Transactions on Electrical and Electronic Materials
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• 제17권2호
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• pp.57-68
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• 2016

In this study, we present the modern hybrid system based power generation for electric vehicle applications. We describe the hybrid structure of modified current source based DC - DC converters used to extract the maximum power from Photovoltaic (PV) and Fuel Cell system. Due to reduced dc-link capacitor requirement and higher reliability, the current source inverters (CSI) better compared to the voltage source based inverter. The novel control strategy includes Distributed Maximum Power Point Tracking (DMPPT) for photovoltaic (PV) and fuel cell power generation system. The proposed DC - DC converters have been analyzed in both buck and boost mode of operation under duty cycle 0.5>d, 0.5<d<1 and 0.5<d for capable electric vehicle applications. The proposed topology benefits include one common DC-AC inverter that interposes the generated power to supply the charge for the sharing of load in a system of hybrid supply with photovoltaic panels and fuel cell PEM. An improved control of Direct Torque and Flux Control (DTFC) based induction motor fed by current source converters for electric vehicle.In order to achieve better performance in terms of speed, power and miles per gallon for the expert, to accepting high regenerative braking current as well as persistent high dynamics driving performance is required. A simulation model for the hybrid power generation system based electric vehicle has been developed by using MATLAB/Simulink. The Direct Torque and Flux Control (DTFC) is planned using Xilinx ISE software tool in addition to a Modelsim 6.3 software tool that is used for simulation purposes. The FPGA based pulse generation is used to control the induction motor for electric vehicle applications. FPGA has been implemented, in order to verify the minimal error between the simulation results of MATLAB/Simulink and experimental results.

• Journal of Power Electronics
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• 제16권6호
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• pp.2294-2305
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• 2016

The introduction of a high-voltage direct-current (HVDC) system based on a modular multilevel converter (MMC) for wind farm integration has stimulated studies on methods to control this type of converter. This research article focuses on the control of the AC voltage and circulating current for a wind-farm-side MMC (WFS-MMC). After theoretical analysis, emotional learning (EL) controllers are proposed for the controls. The EL controllers are derived from the learning mechanisms of the amygdala and orbitofrontal cortex which make the WFS-MMC insensitive to variance in system parameters, power change, and fault in the grid. The d-axis and q-axis currents are respectively considered for the d-axis and q-axis voltage controls to improve the performance of AC voltage control. The practicability of the proposed control is verified under various conditions with a point-to-point MMC-HVDC system. Simulation results show that the proposed method is superior to the traditional proportional-integral controller.

• 한국결정성장학회지
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• 제15권5호
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• pp.198-201
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• 2005

Carbon nanofibers were formed on silicon substrate which was applied by negative direct current (DC) bias voltage using microwave plasma-enhanced chemical vapor deposition method. Formation of carbon nanofibers were varied according to the variation of the applied bias voltage. At -250 V, we found that the growth direction of carbon nanofibers followed the applied direction of the bias voltage. Based on these results, we suggest one of the possible techniques to control the growth direction of the carbon nanofibers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.553-554
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• 2007

This paper proposes the method to increase the current direct load control program by inspecting the problems of the DLC program. In order to increase the number of the customers participating DLC program, a raise of the base incentive and the direct load control incentive is suggested based on the interruption cost of electric power considering the characteristics of kinds of load.

• 한국유기농업학회지
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• 제21권4호
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• pp.523-538
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• 2013

To help improve the current government practice of direct damage-compensation policies, resulting from the loss of profit, sustained by Hanwoo farmers, as a result of the recent Korea-U. S. Free Trade Agreement (FTA), this research aims to examine any problems or issues caused by said policies. To accomplish this task, we have established Hanwoo-SIMO model and estimated the damage of Hanwoo farmers, one without the implementation of the FTA and another with the FTA, to compare and contrast the two. We then analyzed the efficacy of the current government policies. According to our analysis, the current direct compensation policies for the loss of profit on the part of Hanwoo farmers are insufficient. To address this problem, we recommend the government enact a new direct damagecompensation law to address the following issues. First, as the base formula of damage-compensation, the government should use current price of the beef rather than the annually changing flexible price. Second, the flexible control index should remain fixed at 1.0 rate while the government prepares the adequate amount of the damage compensating direct payment resulting from the FTA. Third, the direct government compensation policy should extend beyond the current 15 years (2013-2026) as the profit loss is expected to increase after the midpoint of the FTA.

• 전기학회논문지
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• 제64권2호
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• pp.232-239
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• 2015

Faced with unbalanced grid operation mode, the high voltage direct current (HVDC) based on voltage source converter (VSC) can be properly controlled by a dual current control scheme. For the modular multilevel converter (MMC) controlling the AC side current is able to limit the arm current which flows along the IGBT of submodule (SM) to rated current. However the limitation of the arm current results in leaving the control range of active power at MMC confined to below the rated capacity. As a result, limiting the arm current causes the problem that the DC side voltage of the HVDC can not be controlled to the reference value since MMC HVDC adjusts the DC side voltage through the active power. In this paper, we propose the algorithm adjusting the active powers of both MMCs to resolve the problem. The back-to-back MMC HVDC applying the algorithm is modeled by PSCAD/EMTDC to verify the algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.475-478
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• 1994

In this paper two methods of torque control for brushless DC motor with non-ideal trapezoidal back EMF are presented. One is the method of modulating the reference current so as to give a constant torque since the torque is given by the back EMF and the. phase currents. And the current control loop includes the feedforward control of back EMF and of the neutral voltage between the neutral points of the inverter and of the machine. The other is a direct voltage calculation algorithm for a given reference torque. In the two methods, the time delay due to the calculation is compensated by one sampling current prediction. The simulation results are presented to verify the proposed methods.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.293-296
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• 2002

This paper presents an implementation of Direct torque control(DTC) of Reluctance Synchronous Motor(RSM) drives for an industrial servo drive system with stator current space vector. The estimation of the stator flux magnitude are obtained by using the neural network from measuring the modulus and angle of the stator current space vector. The develolled digitally high-performance control system are shown a good response characteristic of control results and high performance features using 1.0kW RSM.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.297-299
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• 2002

This paper is proposed maximum torque control for electric vehicle drive. At low speeds, the reluctance torque is used to maximize the output for a given current level. This Is achieved maximum torque per ampere(MTPA) by selecting an optimal value of the direct stator current component. At high speeds, the system reaches a point at which the inverter will not be able to supply the desired voltage In this case it Is necessary to make use of an increased value the direct current component. The proposed control algorithm is applied to PMSM drive system, the operating characteristics controlled by maximum torque control are examined in detail by simulation.