• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.97-104
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• 2018

This paper proposes supplementary control of conventional coordinated control of a power plant which directly affects network frequency. The supplementary control with dynamic matrix control is applied for 1000 MW power plant with ultra-supercritical (USC) once-through boiler. The supplementary control signal is added to the boiler feedforward signal in the existing coordinated control logic. Therefore, it is a very practical structure that can maintain the existing multi-loop control system. This supplementary controller uses the step response model for the power plant system, and on-line optimization is performed at every sampling step. The simulation results demonstrate the effectiveness of the proposed supplementary control in a wide operating range of a practical 1000 MW USC power plant simulator. These results can contribute the stable operation of power system frequency.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3089-3091
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• 1999

To control IWR-III Biped Waking Robot, those complex modules are necessary that concurrent control multi-axes servo motors, PID & Feedforward gain tuning, initial value calibration, display current status of system, user interface for emergency safety and three-dimensional rendering graphic visualization. It is developed for various-type gait $data^{[1]}$ and for control modes (i.e open/closed loop and pulse/velocity/torque control) that Integrated Control Enviroment with GUI( Graphic User Interface) consist of time-buffered control part using MMC (Multi-Motion Controller) and 3D simulation part using DirectX graphic library.

• Journal of Power Electronics
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• v.5 no.4
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• pp.282-288
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• 2005

In this paper, a new speed sensorless induction motor scheme which can estimate rotor speed and rotor resistance simultaneously is presented. The rotor flux with a low frequency sinusoidal waveform is used to conduct on-line simultaneous estimation of the rotor speed and rotor resistance. Hence the proposed sensorless control method is robust to rotor resistance variations. Also, the control scheme has no current minor loop to determine voltage references. It contributes to good control performance at low speeds. Some simulation results supported by experiments are given to show the effectiveness of this method.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.159-161
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• 1994

A new control technique which generates high-quality sinusoidal output voltage from a single-phase resonant do link inverter suitable for the UPS systems is presented. The inverter output voltage control system has the PID controller with a minor loop of the filter inductor current and tile feedforward controller. The proposed control scheme also solves resonant voltage overshoot without any additional switch or passive component, resulting in pulses with uniform amplitude and high efficiency. Experimental results in the case of linear and nonlinear loads are presented to confirm the usefulness of the Proposed control algorithms.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2063-2065
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• 2001

This paper presents speed control of a three-phase Induction Motor(I.M.) based on the optimal control theory. This technique is based on the optimal preview controller. The proposed technique comprises a new error system, vector control of the I.M. and the preview feedforwad control loop. Preview feedforward steps are introduced into the control law to enhance the transient response and to improve the robustness of the controlled system. Some computer simulation studies are carried out.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.2
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• pp.54-60
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• 2007

In this paper, we suggest the high efficient control method based on general PI control law for a variable speed refrigeration system. In the variable speed refrigeration system, the capacity and the superheat are mainly controlled by an inverter and an electronic expansion valve, respectively, for saving energy and improving coefficient of performance. Thus, we proposed a decoupling model to eliminate the interfering loop between the capacity and superheat at first. Next, we designed PI controller to control the capacity and superheat independently and simultaneously. Finally, the control performance was investigated through some experiments. The experimental results showed that the proposed PI controller based on the decoupling model can obtain good control performance under the various control references and thermal load.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.146-153
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• 1996

A SCARA type direct drive robot which can be used in the assembly operation was designed and manufactured. Graphite fiber epoxy composite material was used in the fabrication of the robot arm structure in order to improve the speed of the robot arm with a high damping effect. For model-based control and sensitivity analysis of system parameters, the dynamic model of robot arm and drive servo amplifier parameters such as equivalent gains of PWM driver and velocity gains of servo system were estimated from frequency response tests. The complete dynamic model for overall robot system was used in the simulation of the open-loop control. The simulation results agreed reasonably well to the experimental results. The feedforward control using the dynamic models improved the trajectory tracking performance, decreasing the tracking error by factor of three compared with PID control. This study found that the inverse dynamic model of the robot arm including the drive servo system showed better performances than the case of arm dynamic model only.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.51-59
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• 2009

This paper presents the design of continuous-time sigma-delta modulator for acoustic sensor. The feedforward structure without summing block is used to reduce power consumption of sigma-delta modulator. A high-linearity active-RC filter is used to improve resolution of sigma-delta modulator. Excess loop delay problem in conventional continuous-time sigma-delta modulators is solved by our proposed architecture. A low power, high resolution fourth-order continuous-time sigma-delta modulator with 1-bit quantization was realized in a 0.13-${\mu}m$ 1-Poly 8-metal CMOS technology, with a core area of $0.58\;mm^2$. Simulation results show that the modulator achieves 91.3-dB SNR over a 25-kHz signal bandwidth with an oversampling ratio of 64, while dissipating $290{\mu}W$ from a 3.3-V supply.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1086-1093
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• 2001

A new linearization technique for RF high-power amplifiers(HPAs) using n-th order error signal generator (ESGn) is proposed. The n-th order ESG generates an error signal based on the complex envelope transfer characteristics of the HPA, which is combined at the output of the HPA. Therefore, the higher-order nonlinearlities are not affected by the ESG$\_$n/ and the stability of the linearized system is guaranteed due to the inherent open-loop configuration. Moreover, the output delay loss can be avoided, because the error signal is generated with the input signal of the HPA. The IMD(intermodulation distortion) improvement obtained applying the ESG$\_$7/ to 5 W class A HPA in cellular band demonstrates the feasibility of the proposed postdistortion system.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.134-141
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• 2010

Small PEM (Proton Exchange Membrane) fuel cell systems do not require humidification and have great commercialization possibilities. However, methods for controlling small PEM fuel cell stacks have not been clearly established. In this paper, a control method for small PEM fuel cell systems using a dual closed loop with a static feedforward structure is defined and realized using a DSP (Digital Signal Processor). The fundamental elements that need to be controlled in fuel cell systems include the supply of air and hydrogen, water management inside the stack, and heat management of the stack. For small PEM fuel cell stacks operated without a separate humidifier, fans are essential for air supply, heat management, and water management of the stack. A purge valve discharges surplus water from the stack. The proposed method controls the fan using double control loops to quicken transient response of the fan thereby improving the supply rate of air. Feedback control to compensate for the voltage change in fuel cell stack improves the response characteristics in fuel cell to load variations. The feasibility of proposed method was proved by the experiments with a 60W small PEM fuel cell system and operation of a notebook computer using this system.