• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.403-407
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• 2018

This study proposes a predictive direct power control method in a modular multilevel converter (MMC) high-voltage direct-current (HVDC) system. The conventional proportional integral (PI)-based control method uses a cascaded connection and requires an optimal gain selection procedure and additional decoupling scheme. However, the proposed control method has a simple structure for active/reactive power control due to the direct power control scheme and exhibits a fast dynamic response by predicting the future status of system variables and considering time delay. The effectiveness of the proposed method is verified by simulation results.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.425-430
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• 2022

A pumped storage power station is an important means to solve the problem of peak load regulation and ensures the safety of power grid operation. The doubly fed variable-speed pumped storage (DFVSPS) system adopts a doubly fed induction machine (DFIM) to replace the synchronous machine used in traditional pumped storage. The stator of DFIM is connected to the power grid, and the three-phase excitation windings are symmetrically distributed on the rotor. Excitation current is supplied by the converter. The active and reactive power of the unit can be quickly adjusted by adjusting the amplitude, frequency, and phase of the rotor-side voltage or current through the converter. Compared with a conventional pumped storage hydropower station (C-PSH), DFVSPS power stations have various operating modes and frequent start-up and shutdown. This study introduces the structure and principle of the DFVSPS unit. Mathematical models of the unit, including a model of DFIM, a model of the pump-turbine, and a model of the converter and its control, are established. Fast power control strategies are proposed for the unit model. A 300 MW model of the DFVSPS unit is established in MATLAB/Simulink, and the response characteristics in generating mode are examined.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.442-443
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• 2011

In this paper, a voltage control method based on DQ transformation and Space Vector Pulse Width Modulation (SVPWM) for a single phase three-level converter is proposed. This control method is designed to use DC values instead of using instantaneous values of current which are usually used in single-phase application, so that it results in a fast and robust voltage control response. Simulation results demonstrate the validity of the control strategies.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.160-162
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• 2008

This paper presents the practical pressure control of hydraulic oil-pump system using SR drive for industrial application. In order to get a high performance of pressure dynamics in actual application, a data based PID control scheme is proposed in this paper. The look-up table from pre-measured data produces an approximately proper current reference according to motor speed and oil-pressure. And, PID controller can compensate the pressure error. With the combination of two references, the proposed control scheme can get a fast dynamics and stable operation. Furthermore, the suitable current controller considering the nonlinear characteristics of SRM(Switched Reluctance Motor) and practical test method for data measuring are introduced. The proposed control scheme is verified by the experimental test.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.269-272
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• 1988

This paper introduces a method to reduce the reactive power required by electronic converters. The instantaeous reactive power is calculated and compensated by the current controlled PWH voltage source converter connected parallel between the power lines and the converter. A high performance current control technique which is based on the current deviation vector is used for the PWM converter as compensator of reactive power. Accurate compensation of the reactive power and t control system ensuring fast response to the sudden change of loaf are attained. The converter structure and control scheme are discussed. Simulation of the system is performed.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.606-613
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• 2010

This paper proposes a novel current-based maximum power point tracking (CMPPT) method for a single-phase photovoltaic power conditioning system (PV PCS) by using a modified incremental conductance method. The CMPPT method simplifies the entire control structure of the power conditioning system and uses an inherent current source characteristic of solar cell arrays. Therefore, it exhibits robust and fast response under a rapidly changing environmental condition. Digital phase locked loop technique using an all-pass filter is also introduced to detect the phase of grid voltage, as well as the peak voltage. Controllers of dc/dc boost converter, dc-link voltage, and dc/ac inverter are designed for coordinated operation. Furthermore, a current control using a pseudo synchronous d-q transformation is employed for grid current control with unity power factor. A 3 kW prototype PV PCS is built, and its experimental results are given to verify the effectiveness of the proposed control schemes.

• Journal of Korea Multimedia Society
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• v.15 no.12
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• pp.1485-1491
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• 2012

In this paper, we address the problem of fast handover support for future internet networks. The current mobility support protocols, for example Proxy Mobile IPv6, follow a centralized architecture in which a mobility controller is used to manage intra-network handovers that gives rise to high handover latency. To handle this problem, we propose a novel distributed mobility control architecture in which gateways in the network can exchange user information with neighbour gateways to support intra-network handovers, the mobility controller is only needed in case of inter-network handovers. Simulation results show that our architecture reduce approximately 20% intra-network handover latency than Proxy Mobile IPv6.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1047-1054
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• 2007

This paper presents a high efficiency direct instantaneous torque control (DITC) of Switched Reluctance Motor(SRM) based on the nonlinear model. The DITC method can reduce the high inherent torque ripple of SRM drive system, but drive efficiency is somewhat low due to the high current and switching loss during commutations. In order to reduce a torque ripple, a fast torque reference trajectory is selected at every instantaneous rotor position. Based on the nonlinear model of SRM, the developing torque by one phase is fixed and the other phase is regulated for minimum switchings of phase switch and variation of torque. The switching during commutation can be reduced and fast commutation can be obtained in the proposed method. As a result, drive efficiency could be improved as well as torque ripple reduction. The validity of proposed method is verified by computer simulations and comparative experiments.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.252-255
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• 2001

In this paper, a mathematical model of permanent magnet synchronous motor (PMSM) fed by inverter with Direct Torque Control (DTC) Dynamic and steady state characteristics of PMSM is simulated and analyzed: electro-magnetic torque response, speed response, locus of the stator flux linkage. It is mathematically proven that the increase of electromagnetic torque in a permanent magnet motor is proportional the increase of the angle between the stator and rotor flux linkages, and, therefore, the fast torque response can be obtained by adjusting the rotating speed of the stator flux linkage as fast as possible. The simulation results verify the proposed control and also show that the torque response under DTC is much faster than the PWM current controlled drive.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.67-69
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• 2007

PMSM (Permanent Magnet Synchronous Motor) current control is a most inner loop of electromechanical driving systems and it plays a foundation role in the hierarchy's control loop of several mechanical machine systems. In this paper, a simple RMRAC control scheme for the PMSM is proposed in the synchronous frame. In the synchronous current model, the input signal is composed of as a calculated voltage by adaptive laws and system disturbances. The gains of feed-forward and feed-back controller are estimated by the proposed e-modification methods respectively, where the disturbances are assumed as filtered current tracking errors. After the estimation of the disturbances from the tracking errors, the corresponding voltage is fed forward to control input to compensate for the disturbances. The proposed method is robust to high frequency disturbances and has a fast dynamic response to time varying reference current trajectory. It also shows a good real-time performance duo to it's simplicity of control structure. Through the simulations considering several cases of external disturbances and experimental results, efficiency of the proposed method is verified