• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.57-59
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• 2018

This paper presents a novel reference variable speed control scheme of a BLDC motor for the high-speed blender machine according to the current limit. Because of a pulsating load variation of a high-speed blender machine, the actual speed is pulsated by the current limit in the high-speed region. The proposed control scheme uses a variable reference speed to reduce the speed variation from the current limit in the constant power region. The pulsated load is occurred at the material crushing, then the pulsated load is reduced after grinding. The reference speed is smoothly reduced at the pulsated load variation, then the enough torque can make a constant speed during crushing. When the pulsating load is reduced, the reference speed is automatically increased to the original speed value. The proposed control scheme is verified by experimental result by practical blender machine.

• 동력기계공학회지
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• 제22권1호
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• pp.18-24
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• 2018

This paper focuses on systematic design about the membership ranges of the main design factors such as control error, control error rate, and sampling time for the fuzzy logic control of the variable speed drive refrigeration cycle. The upper and the lowest limit of the membership ranges are set up from the data of static characteristics obtained by experiments. Three kinds of membership ranges on the control error and the control error rate are tested by experiments. Especially, an effect of sampling time on control performance is also investigated in the same way. Experimental data showed the control error rate and the sampling time strongly effected on the control performance of the refrigeration cycle with a variable speed drive.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권2호
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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.

• KIEE International Transactions on Power Engineering
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• 제3A권4호
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• pp.206-213
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• 2003

The main purpose of this paper is to present a simulation model for assessing the impacts of a variable speed wind turbine (VSWT) on the distribution network and perform a simulation analysis of voltage profiles along the wind turbine installed feeder using the presented model. The modeled wind energy conversion system consists of a fixed pitch wind turbine, a synchronous generator, a rectifier and a voltage source inverter (VSI). Detailed study on the voltage impacts of a variable speed wind turbine is conducted in terms of steady state and dynamic behaviors. Various capacities and different modes of variable speed wind turbines are simulated and investigated. Case studies demonstrate how feeder voltages are influenced by capacity and control modes of wind turbines and changes in wind speed under different network conditions. Modeling and simulation analysis is based on PSCAD/EMTDC a software package.

• KIEE International Transactions on Power Engineering
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• 제4A권2호
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• pp.51-57
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• 2004

This paper describes the dynamic performance of a variable speed wind turbine system responding to a wide variety of wind variations. Modeling of the wind generation using power electronics interface is proposed for dynamic simulation analysis. Component models and equations are addressed and their incorporations into a transient analysis program, PSCAD/EMTDC are provided. A wind model of four components is described, which enables observing dynamic behaviors of the wind turbine resulting from wind variations. Controllable power inverter strategies are intended for capturing the maximum power under variable speed operation and maintaining reactive power generation at a pre-determined level for constant power factor control or voltage regulation control. The components and control schemes are modeled by user-defined functions. Simulation case studies provide variable speed wind generator dynamic performance for changes in wind speed

• 한국자동차공학회논문집
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• 제10권4호
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• pp.114-121
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• 2002

This paper describes the control system of the toroidal traction driver continuously variable-speed transmission(CVT) fur a tractor. The instrumentation system, the hydraulic power control system and the principle control scheme were introduced. Experimental tests in the bench and the tractor were conducted to validate the performance of the CVT utilizing the proposed controller. The speed of the vehicle was continuously changed to follow the speed set by driver under various operating conditions. Given the reduction ratio of the variator from 2.0 to 1.0, the settling time was about just 0.52 seconds which was satisfactory value for working with the tractor. It was also proved that the tractor could work with continuously variable speed under heavy load disturbances.

• 전기학회논문지
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• 제62권9호
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• pp.1234-1239
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• 2013

This paper provides a technical review of speed control using variable gain PI algorithm for BLDC(Brushless DC) motor. Usually the PI control is used in many motor applications, but a general PI control has problems of overshooting and disturbance for response. By the change of PI gain in motor control operation, these problems can be solved. To find the optimized PI gains for BLDC motor control, many control methods have been proposed. In this paper, the control algorithm with a variable PI gain is applied to improve overshooting response in transient region and rapid load disturbance rejection. Fixed gain and variable gain PI controls are compared. The validity of the propose method is verified by experiment.

• 드라이브 ㆍ 컨트롤
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• 제11권4호
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• pp.53-60
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• 2014

This paper proposes a control scheme to reduce the power consumption of a variable displacement swash-plate type piston pump supplying oil to a valve-controlled hydraulic cylinder at constant pressure. Whenever flow rate demand was absent, the swash plate angle and the pump speed were changed to the minimum values required to compensate for the internal leakage flow. In response to command signals, the pump speed was changed in proportion to the absolute mean value of the speed component for position commands. At the same time, a pressure regulator was activated to maintain constant system pressure by precisely adjusting the pump speed with the swash plate angle fixed at the maximum. The conventional system consisting of a pressure-compensated variable displacement type pump is driven at a constant speed of 1,800rpm. By comparison, computer simulation and experimental results showed that idling power at stand-by status could be reduced by up to 70% by reducing the pump speed from 1,800rpm to 300rpm and the swash plate angle to the minimum.

• Journal of Power Electronics
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• 제15권1호
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• pp.246-255
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• 2015

This paper presents experimental results and its assessment of a variable-speed wind power generation system (VSWPGS) using permanent magnet synchronous generator (PMSG) and boost chopper circuit (BCC). Experimental results are obtained by a test bench with a wind turbine emulator (WTE). WTE reproduces the behaviors of a windmill by using servo motor drives. The mechanical torque references to drive the servo motor are calculated from the windmill wing profile, wind velocity, and windmill rotational speed. VSWPGS using PMSG and BCC has three speed control modes for the level of wind velocity to control the rotational speed of the wind turbine. The control mode for low wind velocity regulates an armature current of generator with BCC. The control mode for middle wind velocity regulates a DC link voltage with a vector-controlled inverter. The control mode for high wind velocity regulates a pitch angle of the wind turbine with a pitch angle control system. The hybrid of three control modes extends the variable-speed range. BCC simplifies the maintenance of VSWPGS while improving reliability. In addition, VSWPGS using PMSG and BCC saves cost compared with VSWPGS using a PWM converter.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.652-655
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• 1996

This paper develops an AC motor controller for applications. The AC motor controller is designed based on the variable structure control method and a variable structure disturbance observer is added to reduce the effects of exogenous disturbances. The designed controller is installed on the z-axis of a CNC machining center and milling experiments were performed. The results show improved performance on both position and speed tracking, when compared to the factory-designed servo controller.