• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.86-87
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• 2013

본 논문에서는 직접 토크 제어(Direct Torque Control, DTC) 방식을 이용한 매입형 영구자석 동기전동기(Interior Permanent Magnet Synchronous Motor, IPMSM)의 운전 영역을 자속 평면에서 분석하고, 약자속 제어를 포함한 전 운전 영역에서의 최대 토크 운전 기법을 제안하였다.

• Journal of Wind Energy
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• v.2 no.1
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• pp.90-96
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• 2011

The purpose of this paper is to describe the control system for optimal performance of 2MW gearless PMSG wind turbine system, and to afford some techniques of the algorithm selection and design optimization of the wind turbine control system through analysis of load calculation and control characteristic. Wind turbine control system is composed of the main control system and remote control and monitoring system. The main control system is industrial PC based controller, and the remote control and monitoring system is a server based computer system. The main control system has a supervisory control of the wind turbine with operation procedures and power-speed control through the torque control by pitch angle. There are some applications to optimize the wind turbine system at the starting mode with increasing of rotor speed, and cut-in operating mode to prevent trundling cut-in and cut-out, a gain scheduling of pitch PID controller, torque scheduling and limitation of generation power by temperature limitation or remote command by remote control and monitoring system. Also, the server operation program of the remote control and monitoring system and the design of graphical display are described in this paper.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.24-27
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• 2008

For high voltage DC-DC converters, the parallel operation of several high voltage source modules is necessary to reduce the material cost. In the conventional parallel operation with HDC module control unit, it is difficult to repair the HDC system for the failure of control unit. To overcome these problems, new parallel operating algorithm for high voltage DC-DC converter is presented. The proposed algorithm has no main control unit and each module can be selected as the master according to the operating conditions. Therefore, one of modules can be replaced as the master immediately when the previous master module is failed. In addition, the extension of extra modules can be simple.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.150-151
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• 2007

In hydraulic oil pump system, pressure has a linear relationship with output torque of motor. Torque control of pump drive can easily output stable pressure, and it can retain required pressure at minimum speed to save power consumption. Switched reluctance motor(SRM) has many advantages such as low cost and low inertia. It can generate high torque at low speed. But inherent high torque ripple of SRM influences performance of pressure control in hydraulic oil system. This paper presents direct instantaneous torque control(DITC) of hydraulic oil pump system. DITC method can reduce inherent torque ripple of SRM, and output smoothing torque to load. So the proposed hydraulic oil pump system can support smooth pressure and fast dynamic power supply to the hydraulic pump system. At last the proposed hydraulic oil pump system is verified by computer simulation and experimental results.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1060-1068
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• 2018

Droop control schemes have been widely employed in the control strategies for Multi-Terminal Direct Current (MTDC) system for its high reliability. Under the conventional DC voltage-active power droop control, the droop slope applies a proportional relationship between DC voltage error and active power error for power sharing. Due to the existence of DC network impedance and renewable resource fluctuation, there is inevitably a DC voltage deviation from the droop characteristic, which in turn results in inaccurate control of converter's power. To tackle this issue, a piecewise droop control with DC voltage dead band or active power dead band is implemented into controller design. Besides, an advanced droop control scheme with versatile function is proposed, which enables the converter to regulate DC voltage and AC voltage, control active and reactive power, get participated into frequency control, and feed passive network. The effectiveness of the proposed control method has been verified by simulation results.

• Journal of Power Electronics
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• v.17 no.2
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• pp.368-379
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• 2017

In this paper, a direct torque control algorithm with novel duty cycle-based modulation is proposed for permanent magnet synchronous motor drives fed by neutral-point clamped three-level inverters. Compared with the standard DTC, the proposed algorithm can suppress steady-state torque ripples as well as ensure neutral-point potential balance and smooth vector switching. A unified torque/flux evaluation table with multiple voltage vectors and precise control levels is established and used in this method. This table can be used to evaluate the effects of duty-cycle vectors on torque and flux directly, and the elements of the table are independent of the motor parameters. Consequently, a high number of appropriate voltage vectors and their corresponding duty cycles can be selected as candidate vectors to reduce torque ripples by looking up the table. Furthermore, small vectors are incorporated into the table to ensure the neutral-point potential balance with the numerous candidate vectors. The feasibility and effectiveness of the proposed algorithm are verified by both simulations and experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.517-524
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• 1998

This paper discusses the development of a reactive power controller using digital signal processing. Digital Signal Processing is the technique of using digital devices to Process continuous signals or data, often in real-time. And DSP algorithms are associated with a discrete time interval between input samples. When one designs a digital filter, one can use a Laplace transform to determine the continuous time frequency response. The corresponding discrete time transform is called Z transform and depends upon discrete samples of the input spaced equally in time. The objectives of this paper are to minimize real power losses and improve the power factor of a given system. Also, the implementation of a direct-form non recursive filter on the TMS320C31 has been described. The application of this microprocessor-based controller using DSP on test system reveals its numerous advantages. Performance and features of the controller for the reactive power control are analyzed.

• Journal of Power Electronics
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• v.11 no.2
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• pp.148-155
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• 2011

Direct torque control(DTC) of induction machines is known to offer fast instantaneous torque and flux control with a simple control structure. However, this scheme has two major disadvantageous, namely, a variable inverter switching frequency and a high torque ripple. These problems occur due to the use of hysteresis comparators in conventional DTC schemes, particularly in controlling the output torque. This paper reviews the utilization of constant frequency torque controllers (CFTC) in DTC to solve these problems while retaining the simple control structure of DTC. Some extensions of the work in utilizing a CFTC will be carried out in this paper which can further reduce the torque ripple. This is particularly useful for a system which has a limited/low sampling frequency. The feasibility of a CFTC with an extended carrier frequency in minimizing the torque ripple is verified through experimental results.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.51-52
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• 2008

In this paper, we propose two control schemes. The first control scheme is an adaptive passivity-based excitation control which regulates the terminal voltage to its reference. This controller is obtained through two steps: firstly, a simple direct adaptive passivation controller is designed for the power system with parametric uncertainties; then a linear PI controller is applied to converge the terminal voltage to its reference. The second control scheme is a linear governor control which consists of the frequency and the mechanical power. It is shown that the internal dynamics are locally stable with controllable damping. In the end, the boundness of all electrical variables, the frequency, the mechanical power, and the convergence of the terminal voltage to its reference can be achieved by these control schemes.

• International Journal of Control, Automation, and Systems
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• v.3 no.spc2
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• pp.270-277
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• 2005

In this paper, a decentralized control problem is considered for multimachine power systems with nonlinear interconnections and disturbances. A direct feedback linearization compensator is employed to cancel most of the nonlinearities, and then a backstepping procedure is applied to deal with the interconnections and to reduce the effects of a disturbance that does not satisfy the matching condition. In this procedure, the disturbance is handled by using a smooth approximation of the signum function. Practical stability is achieved under the assumption that the infinite norm of the disturbance is known. However, even in the case where the infinite norm of the disturbance is not known precisely, the proposed control system still guarantees $L_2$ stability. Furthermore, the origin is globally uniformly asymptotically stable in the absence of the disturbance. A three-machine power system is considered as an application example.