• Journal of Power Electronics
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• v.16 no.2
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• pp.798-804
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• 2016

This paper proposes a new operation and control strategy for Power-Assisted Wheelchairs (PAW) using one brushless DC (BLDC) motor. The conventional electrical wheelchairs are too heavy and large for one person to move because they have two electric motor wheels. On the other hand, the proposed PAW system has a small volume and is easy to move due to the presence of a single wheel motor. Unlike the conventional electric wheelchairs, this structure for a PAW does not have a control joystick to reduce its weight and volume. To control the wheelchair without a joystick, a special control system and algorithm are needed for proper operation of the wheelchair. In the proposed PAW system uses only one sensor to detect the acceleration and direction of PAW's movement. By using this sensor, speed control can be achieved. With a speed control system, there are three kinds of operations that can be done on the speed of a PAW: the increment of PAW speed by summing external force, the decrement of PAW speed by subtracting external force, and emergency breaking by evaluating the time duration of external force. The validity of the proposed algorithm is verified through experimental results.

• Journal of Power Electronics
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• v.13 no.3
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• pp.381-389
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• 2013

A method to control the speed or the torque of a permanent-magnet direct current motor is presented. The rotor speed and the external torque estimation are simultaneously provided by appropriate observers. The sensorless control scheme is based on current measurement and switching states of power devices. The observers performances are dependent on the accurate machine parameters knowledge. Sliding mode control approach was adopted for drive control, providing the suitable switching states to the chopper power devices. Despite the predictable chattering, a convenient first order switching function was considered enough to define the sliding surface and to correspond with the desired control specifications and drive performance. The experimental implementation was supported on a single dsPIC and the controller includes a logic overcurrent protection.

• Journal of Power Electronics
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• v.3 no.3
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• pp.197-204
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• 2003

An improved nonlinear speed control of a permanent magnet synchronous motor (PMSM) is presented A quasi-linearized and decoupled model including the influence of parameter variations and speed measurement error on the nonlinear speed control of a PMSM is derived Using this model, to overcome the drawbacks of conventional nonlinear control scheme, the improved nonlinear control scheme which employs time delay control (TDC) scheme is proposed. To show the validity of the proposed control scheme, simulation studies are carried out and compared with the conventional control scheme.

• Journal of Power System Engineering
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• v.3 no.1
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• pp.67-73
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• 1999

It is not easy to control the speed of AC motors accurately without modeling with some parameters for the controlled system. However, there are some application parts which do not require high speed responses strictly and the motor parameters can not to be identified simply. In this paper, a speed control method for a synchronous motor(S.M) with unknown parameters of the motor is investigated. The method is based on the current control algorithm. Speed controller and current controller are designed using PI control law. Some experiments are performed using DSP and power expert system to prove the validity of the proposed method. Throughout experimental results, the method is confirmed successfully. This method is expected to control the system with unknown parameters of the S.M efficiently.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.2
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• pp.107-115
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• 2006

In this paper, a new speed sensorless control based on an instantaneous reactive power is proposed for the interior permanent magnet synchronous motor(IPMSM) drives. In proposed algorithm, the current observer estimates the line currents and the estimated speed can be yielded from the voltage equation because the information of speed is included in back EMF. To implement speed sensorless control, the current observer is composed by using the voltage equation of the IPMSM in the stationary reference frame fixed to the stator. The estimated speed of the rotor is composed by using the voltage equation of the IPMSM in the rotating reference frame fixed to the rotor The estimated speeds to minimize the speed error compensated by using the instantaneous reactive power. The instantaneous reactive power is calculated on the rotating reference frame fixed to the rotor. The effectiveness of the preposed algorithm is confirmed by the experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.235-240
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• 2000

In this paper a digital-control algorithm of a power system suing a high-speed PWM for a MRI system is proposed. The MRI system requires an elaborate ladder-shaped current source. And the load of current source is the inductance with resistance. For the inductive load a voltage output of the power system has hi호 frequency components. Therefore this system requires high-speed PWM above 80KHz, A high speed PWM control algorithm which satisfies those conditions is designed. Finally the performance of proposed control algorithm is shown by simulation.

• Journal of Power Electronics
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• v.12 no.2
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• pp.305-316
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• 2012

The paper presents an accurate loss model based controller of an induction motor to calculate the optimal air gap flux. The model includes copper losses, iron losses, harmonic losses, friction and windage losses, and stray losses. These losses are represented as a function of the air gap flux. By using the calculated optimal air gap flux compared with rated flux for speed sensorless indirect vector controlled induction motor, an improvement in motor efficiency is achieved. The motor speed performance is improved using a fuzzy logic speed controller instead of a PI controller. The fuzzy logic speed controller was simulated using the fuzzy control interface block of MATLAB/SIMULINK program. The control algorithm is experimentally tested within a PC under RTAI-Linux. The simulation and experimental results show the improvement in motor efficiency and speed performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.941-945
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• 2006

In the development of electricity generating wind turbines for wind farm application, only two types have survived as the methods of power regulation; stall regulation and fun span pitch control. The sound measurement procedures of IEC 61400-11 are applied to field test and evaluation of noise emission from each of 1.5 MW and 660 kW wind turbine generators (WTG) utilizing the stall regulation and the pitch control for the power regulation, respectively. Apparent sound power level, wind speed dependence and third-octave band levels are evaluated for both of WTGs. It is found that while 1.5 MW WTG using the stall control is found to emit lower sound power than 660 kW one using the pitch control at low wind speed (below 8 m/s), sound power from the former becomes greater than that of the latter in the higher wind speed. Equivalent continuous sound pressure levels (ECSPL) of the stall control type of WTG vary more widely with wind speed than those of the pitch control type of WTG These characteristics are believed to be strongly dependent on the basic difference of the airflow around the blade between the stall regulation and the pitch control types of WTG. These characteristics according to the methods of power regulation lead to the very different noise emission characteristics of WTG depending on the seasons because the average wind speed in summer is lower than the critical velocity over which the airflow on the suction side of blade in the stall types of WT are separated. These results propose that, in view of environmental noise regulation, the developer of wind farm should give enough considerations to the choice of power regulation of their WTG based on the weather conditions of potential wind farm locations.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.331-334
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• 2003

In this paper, on the subject of a speed control wind turbine, the type of wind speed reference decision between conventional MPPT tracking speed control and MPPT with LPF(Low Pass Filter) speed control algorithm are introduced and its performances are compared using a model based on MATLAB Simulink, and to get more realistic output data, the stored wind data as its wind speed input from 30kW wind power system in Buan, Haechang is used.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1358-1366
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• 2015

This study focuses on an advanced second-order sliding mode control strategy for a variable speed wind turbine based on a permanent magnet synchronous generator to maximize wind power extraction while simultaneously reducing the mechanical stress effect. The control design based on a modified version of the super-twisting algorithm with variable gains can be applied to the cascaded system scheme comprising the current control loop and speed control loop. The proposed control inheriting the well-known robustness of the sliding technique successfully deals with the problems of essential nonlinearity of wind turbine systems, the effects of disturbance regarding variation on the parameters, and the random nature of wind speed. In addition, the advantages of the adaptive gains and the smoothness of the control action strongly reduce the chatter signals of wind turbine systems. Finally, with comparison with the traditional super-twisting algorithm, the performance of the system is verified through simulation results under wind speed turbulence and parameter variations.