• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.60-70
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• 2014

This paper discusses the impacts of large scale grid-connected wind farm equipped with permanent magnet synchronous generator (PMSG) on power system small signal stability (SSS) incorporating wind generation uncertainty and volatility. Firstly, a practical simplified PMSG model with rotor-flux-oriented control strategy applied is derived. In modeling PMSG generator side converter, the generator-voltage-oriented control strategy is utilized to implement the decoupled control of active and reactive power output. In modeling PMSG grid side converter, the grid-voltage-oriented control strategy is applied to realize the control of DC link voltage and the reactive power regulation. Based on the Weibull distribution of wind speed, the Monte Carlo simulation technique based is carried out on the IEEE 16-generator-68-bus test system as benchmark to study the impacts of wind generation uncertainty and volatility on small signal stability. Finally, some preliminary conclusions and comments are given.

• Journal of Power Electronics
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• v.18 no.3
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• pp.789-801
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• 2018

Model predictive direct power control (MPDPC) is a widely recognized high-performance control strategy for a three-phase grid-connected pulse width modulation (PWM) rectifier. Unlike those of conventional grid-connected PWM rectifiers, the active and reactive powers of permanent magnet synchronous generator (PMSG)-connected PWM rectifiers, which are used in electromagnetic transmitters, cannot be calculated as the product of voltage and current because the back electromotive force (EMF) of the generator cannot be measured directly. In this study, the predictive power model of the rectifier is obtained by analyzing the relationship among flux, back EMF, active/reactive power, converter voltage, and stator current of the generator. The concept of duty cycle control in the proposed MPDPC is introduced by allocating a fraction of the control period for a nonzero vector and rest time for a zero vector. When nonzero vectors and their duration in the predefined cost function are simultaneously evaluated, the global power ripple minimization is obtained. Simulation and experimental results prove that the proposed MPDPC strategy with duty cycle control for the PMSG-connected PWM rectifier can achieve better control performance than the conventional MPDPC-SVM with grid-connected PWM rectifier.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.397-402
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• 2005

A new control algorithm of soft starter is proposed for the reduction of the inrush current during the grid connection of the induction-type wind power generator. Currently, the fixed speed wind turbine using induction generator is the most popular wind generation system in Korea. It is shown that the amount of inrush current mainly depends on the control algorithm of the soft starter, a thyristor-based grid connection device. For the simulation study, a 600kw wind turbine simulation model is developed and the transient waveforms are investigated with conventional md proposed methods. Also experimental results using 3.7kW experimental set-up show that the peak value of inrush current is reduced about 20$\%$ using proposed algorithm.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.12
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• pp.1163-1168
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• 2009

The power quality of wind energy becomes more and more important in connecting wind-farms to the grid, especially weak grid. This paper presents the simulation of a wind farm of a permanent magnet synchronous generator (PMSG) and a doubly fed induction generator (DFIG). Flicker mitigation is performed by using PMSG as a static synchronous compensator (STATCOM) to regulate the voltage at the point of common coupling (PCC). A benefit of the measure is that integrating two function of to control the active power flow and to reduce the voltage flicker in a wind farm. Simulation results show that controlling PMSG is an effective and economic measure in reducing the flicker during continuous operation of grid connected wind turbines regardless of short circuit capacity ratio, turbulence intensity and grid impedance angle.

• Journal of the Korean Solar Energy Society
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• v.34 no.2
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• pp.16-23
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• 2014

This paper presents a renewable energy configuration plan of Micro grid in Gapa Island. To analyze the characteristics of Micro grid, BESS (Battery Energy Storage System), PMSG (Permanent Magnet Synchronous Generator) and SCIG (Squirrel Cage Induction Generator) are first modelled. The PMSG and SCIG will operate with basis on the real power curve. when the total power demand is larger than the total power generation, the BESS will be operated and the SOC (State Of Charge) is reduced. If the value of SOC could drop down to limited value, the system may be broken because of the voltage drop of BESS. To solve this problem, a DG (Diesel Generator) is used to charge the BESS and keep the voltage value of BESS with in a allowance limit. This paper represents simulation result when PMSG, SCIG connected to the Micro grid installed in Gapa Island. The simulation is carry out by using PSCAD/EMTDC program with actual line constant and transformer parameter in Gapa Island.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.30-37
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• 2018

Unlike an AC system, a DC system does not cause problems with synchronization, stability, reactive power, system losses, and cost. However, more research is still required for the application of DC Systems. This paper proposes a stable black-start strategy for a stand-alone DC micro-grid, which consists of an energy storage system, photovoltaic generator, wind-turbine generator, diesel generator, and DC loads. The proposed method is very important for avoiding inrush current and transient overvoltage in the power system equipment during restoration after a blackout. PSCAD/EMTDC software was used to simulate, analyze, and verify the method, which was found to be stable and applicable for a stand-alone DC micro-grid.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.91-103
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• 2015

This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage wind power system under unbalanced grid conditions. Negative sequence control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors: fault ride-through capability, instantaneous active power pulsation, harmonic distortions, and torque pulsation. The control algorithm having zero amplitude of torque ripple indicates the most cost-effective performance in terms of torque pulsation. The least active power pulsation is produced by a control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive power. A combination of these two control algorithms depending on operating requirements and depth of grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions, leading to a high-performance DFIG wind turbine system with unbalanced grid adaptive features.

• Journal of Power Electronics
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• v.11 no.4
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• pp.568-575
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• 2011

This paper proposes an application of energy storage devices (ESD) for low-voltage ride-through (LVRT) capability enhancement and power smoothening of doubly-fed induction generator (DFIG) wind turbine systems. A grid-side converter (GSC) is used to maintain the DC-link voltage. Meanwhile, a machine-side converter (MSC) is used to control the active and reactive powers independently. For grid disturbances, the generator output power can be reduced by increasing the generator speed, resulting in an increased inertial energy of the rotational body. Design and control techniques for the energy storage devices are introduced, which consist of current and power control loops. Also, the output power fluctuation of the generator due to wind speed variations can be smoothened by controlling the ESD. The validity of the proposed method has been verified by PSCAD/EMTDC simulation results for a 2 MW DFIG wind turbine system and by experimental results for a small-scale wind turbine simulator.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2192-2201
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• 2016

Wind energy is currently the fastest-growing electricity source worldwide. The cost efficiency of wind generators must be high because these generators have to compete with other energy sources. In this paper, a system that utilizes an open-winding permanent-magnet synchronous generator is studied for wind-energy generation. The proposed system controls generated power through an auxiliary voltage source inverter. The VA rating of the auxiliary inverter is only a fraction of the system-rated power. An adjusted control system, which consists of two main parts, is implemented to control the generator power and the grid-side converter. This paper introduces a study on the effect of unbalanced voltages for the wind-generation system. The proposed system is designed and simulated using MATLAB/Simulink software. Theoretical and experimental results verify the validity of the proposed system to achieve the power management requirements for balanced and unbalanced voltage conditions of the grid.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.478-480
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• 1998

We develops a simulator to evaluate the performance of the autosyncronizer. The autosyncronizer is used to automatically syncronize magnitude, frequency, and phase of 3 phase signals of generator with respect to those of the utility grid. This autosyncronizer needs to be evaluated its performance to prevent malfunctions. To do this, 3 phase signals of generator and the utility grid are simulated and signals of the generator should be changed by ouput of the autosyncronizer with high precision. In this paper, we uses TMS320C31 to generate high precision sinusoidal 3 phase signals using Table Lookup method. In this process, it is very desirable to control magnitude, frequency, and phase of the signal with high precision and this is achieved by appropriate interpolation method. The resulted signal is well controlled and has low THD and could be used to evaluate the performance of the autosyncronizer.