• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.255-262
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• 2011

This paper proposes a grid-tied power conditioning system for fuel cell, which consists of three-phase current-fed DC-DC converter and three-phase PWM inverter. The three-phase current-fed DC-DC converter boosts fuel cell voltage of 26-48 V up to 400 V with zero-voltage switching (ZVS) scheme, while the three-phase PWM(Pulse Width Modulation) inverter controls the active and reactive power supplied to the grid. The operation of the proposed power conditioning system with fuel cell model is verified through simulations with PSCAD/EMTDC software. The feasibility of hardware implementation is verified through experimental works with a laboratory prototype with 1.2 kW proton exchange membrane (PEM) fuel cell stack. The proposed power conditioning system can be commercialized to interconnect the fuel cell with the power grid.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.133-136
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• 2004

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1322-1333
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• 2014

To track the sinusoidal current under stationary frame and suppress the effects of low-order grid harmonics, the multi-resonant quasi-proportional plus resonant (PR) controller has been extensively used for digitally controlled LCL-type pulse-width modulation (PWM) converters with capacitor-current-feedback active damping. However, designing the controller is difficult because of its high order and large number of parameters. Moreover, the computation and PWM delays of the digitally controlled system significantly affect damping performance. In this study, the delay effect is analyzed by using the Nyquist diagrams and the system stability constraint condition can be obtained based on the Nyquist stability criterion. Moreover, impact analysis of the control parameters on the current loop performance, that is, steady-state error and stability margin, identifies that different control parameters play different decisive roles in current loop performance. Based on the analysis, a simplified controller design method based on the system specifications is proposed. Following the method, two design examples are given, and the experimental results verify the practicability and feasibility of the proposed design method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.947-950
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• 2005

For revolving and elevating a turret of a tank, we substitute an existing oil pressure system with an electric system using a motor and applied the vector control method to this system. A switching method of an inverter for providing desired sinusoidal current to each phase of a motor, we adopted min-max pulse width modulation method which takes less computation time, rather than space vector pulse width modulation method. We designed a digital filter and applied it to the control system. Developed current controller is verified it's performance through a current control test, speed control test, frequency response and tracking a profile of speed test.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1253-1255
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• 2003

Since the residential load is an AC load and the output of solar cell is a DC Power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation. it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2334-2342
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• 2015

This paper proposes an LED driving circuit with a digital controller, power factor correct (PFC) function, and low light flicker. The key topology of the proposed circuit is a conventional Flyback combined with a pre-stage. As a result, there will be less light flicker than with other one-stage PFC circuits. A digital controller, implemented using a low-cost microcontroller, dsPIC30F2020, will meet PFC and low light flicker. The experimental results validate the functionality of the proposed circuit.

• Proceedings of the KWS Conference
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• 2000.04a
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• pp.99-102
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• 2000

Conventionally, ZVS FB DC/DC converter was controlled by monolithic IC UC3879, which includes the functions of oscillator, error amplifier and phase-shift circuit. Also, microprocessor and DSP have been widely used for the remote control and for the immediate waveform control in ZVS FB DC/DC converter. However the conventional microprocessor controller is complex and difficult to control because the controller consists of analog and digital parts. In the case of the control of FB DC/DC converter, the output is required of driving a direct signal to the switch drive circuits by the digital controller. So, this paper presents the method and realization of designing the digital-to-phase shift PWM circuit controlled by DSP (TMX320C32) in a 2,500A, 40㎾ WS FB DC/DC converter.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.630-632
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• 1999

In this paper, we develop intelligent digitally redesigned PAM and PWM fuzzy controllers for nonlinear systems. Takagi-Sugeno fuzzy model is used to model the nonlinear systems and a continuous-time fuzzy-model-based controller is designed based on the extended parallel-distributed-compensation method. The digital controllers are determined from existing analogue controllers. The proposed method provides an accurate and effective method for digital control of continuous·time nonlinear systems and enables us to efficiently implement a digital controller via pre-determined continuous-time TS fuzzy-model-based controller. We have applied the proposed method to the balancing problem of the inverted pendulum to show the effectiveness and feasibility of the method.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1536-1541
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• 2003

In order to investigate the cooling and heating characteristics of a variable-capacity system A/C using a digital scroll compressor, the cooling and heating capacities and EER are measured by the psychrometric calorimeter. The capacity of the system is controlled by the digital scroll compressor, which is operated by controling PWM valve and the loading vs. unloading time. When the system A/C is operated under the cooling and heating standard conditions, EER is nearly uniform but cooling capacity and heating capacity increase at minimum, rated and maximum modes. When the auxiliary heater is on, at the cold region, the system A/C produces the excellent heating capacity.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.137-139
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• 2006

This paper present an implementation of digital control system for a phase-shift full-bridge converter using a digital signal processor. The digital control of phase-shift full-bridge converter provides many advantageous of easily generating various phase-shift timing and implementing a complex voltage and current control algorithm. The digital controller is implemented using the DSP TMS320F2812 and the converter and controller operation is proved through the experimental results.