Dong-Choon Lee

Yeungnam University, Onyang, South Chungcheong, South Korea

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Publications (46)47.66 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: This paper proposes a low-voltage ride-through scheme for the permanent magnet synchronous generator (PMSG) wind power system at the grid voltage sag. The dc-link voltage is controlled by the generator-side converter instead of the grid-side converter (GSC). Considering the nonlinear relationship between the generator speed ω$_m$ and the dc-link voltage V$_{\bf dc}$ , a dc-link voltage controller is designed using a feedback linearization theory. The GSC controls the grid active power for a maximum power point tracking. The validity of this control algorithm has been verified by simulation and experimental results for a reduced-scale PMSG wind turbine simulator.
    IEEE Transactions on Power Electronics 01/2012; 27(5):2376-2384. · 4.08 Impact Factor
  • Dong-Eok Kim, Dong-Choon Lee
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    ABSTRACT: In this paper, a feedback linearization technique is proposed to control the output voltage control of three-phase uninterruptible power supply systems. First, a nonlinear model including the output LC filters is derived from the power balance condition between the inverter output terminal and the load side. Then, input-output feedback linearization is applied to the nonlinear model to make it linear. The controller of the linearized model is designed by linear control theory. The tracking control law is obtained with a pole placement technique. It is shown experimentally that the proposed control scheme gives high dynamic responses in response to load variation as well as a zero steady-state error.
    IEEE Transactions on Industrial Electronics 04/2010; · 5.17 Impact Factor
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    ABSTRACT: This paper proposes a robust control strategy of the PMSG wind power system for the grid voltage sag. The DC-link voltage control is achieved by the generatorside converter instead of the grid-side converter. Considering the nonlinear relationship between the generator speed (ωm) and DC-link voltage (vdc), a DC-link voltage controller is designed using feedback linearization technique. The grid-side converter controls the grid power for MPPT. The validity of this control algorithm has been verified by simulation results for 2MW PMSG wind power system.
    01/2010;
  • Source
    Dong-Eok Kim, Dong-Choon Lee
    [show abstract] [hide abstract]
    ABSTRACT: This paper proposes a feedback linearization control scheme of AC/DC PWM converters with LCL input filters using no damping resisters. Feedback linearization techniques use a transformation from nonlinear system models into equivalent linear models in a simpler form. The feedback linearization scheme in this work has cascade structures unlike usual feedback linearization, therefore it has an advantage that it is possible to limit the capacitor current to a certain level. The performance of the proposed controller is validated with simulation and experimental results.
    Journal of Power Electronics. 04/2009; 9.
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    ABSTRACT: Machine speed is usually required for maximum power point tracking (MPPT) control of permanent-magnet synchronous generators (PMSG). In this paper, a sensorless control method is applied to the PMSG for micro wind turbine systems. The machine speed is estimated by using a rotor flux observer and induced EMF signal, which can solve the delay problem of the estimated speed. For vector control of PMSG for micro wind turbines, a cost-effective back-to-back PWM-type converter consisting of a two-leg three phase PWM converter and a half-bridge PWM converter is used, by which generator output power can be increased both in steady state and in transient state. The validity of the proposed control algorithm has been verified by simulation results.
    Power and Energy Conference, 2008. PECon 2008. IEEE 2nd International; 01/2009
  • Source
    A.G. Abo-Khalil, Dong-Choon Lee
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    ABSTRACT: In this paper, a new online capacitance estimation method for dc-link capacitors in a three-phase ac/dc/ac pulsewidth-modulation converter is proposed. A controlled ac voltage with a lower frequency than the line frequency is injected into the dc-link voltage, which then causes ac power ripples at the dc output side. By extracting the ac power component on the dc output side using digital filters, the capacitance can then be calculated using a support vector regression method. A function that defines the relation between a given capacitor power and its corresponding capacitance is determined using a set of training data. This function is then used to predict the output for the given input which is not included in the training set. The proposed method can be simply implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.15%.
    IEEE Transactions on Industry Applications 10/2008; · 1.67 Impact Factor
  • Dong-Eok Kim, Dong-Choon Lee
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    ABSTRACT: In this paper, a fault diagnosis scheme of three-phase PWM inverters is proposed, which is based on a discrete wavelet transform (DWT) and a pattern recognition algorithm called support vector machine (SVM). First, a discontinuity of current signal, which is usually caused by switch open-circuit faults, is detected by the DWT, and then fault detection and isolation are processed by the SVM. The proposed method is verified by simulation results.
    Industrial Electronics, 2008. ISIE 2008. IEEE International Symposium on; 08/2008
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    A.G. Abo-Khalil, Dong-Choon Lee
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    ABSTRACT: In this paper, a novel algorithm for wind-speed estimation in wind-power generation systems is proposed, which is based on the theory of support-vector regression (SVR). The inputs of the SVR wind-speed estimator are chosen as the wind-turbine power and rotational speed. During the offline training, a specified model, which relates the inputs to the output, is obtained. Then, the wind speed is determined online from the instantaneous inputs. The experimental results have verified the validity of the proposed estimation algorithm.
    IEEE Transactions on Industrial Electronics 04/2008; · 5.17 Impact Factor
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    ABSTRACT: This paper proposes a control scheme which can eliminate the torque ripple of the DFIM at unbalanced source voltage. The machine torque is expressed using the positive and negative sequence components of the voltage and current. For suppression of the torque ripple, the stator reactive power ripple is controlled to be zero. The proposed torque elimination method is verified by simulation results using PSCAD/EMTDC.
    Power Electronics and Drive Systems, 2007. PEDS '07. 7th International Conference on; 12/2007
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    Dong-Eok Kim, Dong-Choon Lee
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    ABSTRACT: In this paper, an improved nonlinear control strategy of the inverter output voltage for the three-phase UPS systems is proposed. At first, a nonlinear modeling including the output LC filters is derived from the power balance condition between the inverter output and load sides. Then input-output feedback linearization is applied to the nonlinear model, which can be linearized. The controller of the linearized model can be designed easily by linear control theory. The tracking control law is obtained with the pole placement technique. It is shown that the proposed control scheme gives high dynamic responses at load variation as well as a zero steady-state error.
    Industrial Electronics Society, 2007. IECON 2007. 33rd Annual Conference of the IEEE; 12/2007
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    A.G. Abo-Khalil, Hong-Geuk Park, Dong-Choon Lee
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    ABSTRACT: In this paper, a novel control algorithm for minimizing the operating loss of doubly fed induction generators (DFIG) for variable speed wind turbines is presented. At first, the generator losses are modeled, which consist of the copper loss and the iron losses. Then, a stator d-axis current is derived which minimizes the total generator loss. Based on this current, the stator reactive power level is controlled. The experimental results for a 3 kW DFIG wind turbine simulator show that the amount of power saving approaches to 23% at 5[m/s] wind speed, which is more significant at low wind speed.
    Industrial Electronics Society, 2007. IECON 2007. 33rd Annual Conference of the IEEE; 12/2007
  • Source
    Dong-Eok Kim, Dong-Choon Lee
    [show abstract] [hide abstract]
    ABSTRACT: This paper proposes a feedback linearization control scheme of AC/DC PWM converters with LCL input filters using no damping resisters. Feedback linearization techniques use a transformation from nonlinear system models into equivalent linear models in a simpler form. The feedback linearization scheme in this paper has cascade structures unlike the usual feedback linearization, therefore it has an advantage that it is possible to limit the converter current to a certain level. To reduce the number of sensors, source voltages and currents are estimated. The performance of the proposed controller is validated with simulation and experimental results.
    Power Electronics, 2007. ICPE '07. 7th Internatonal Conference on; 11/2007
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    [show abstract] [hide abstract]
    ABSTRACT: This paper proposes a low-cost power converter for micro wind turbine systems using permanent magnet synchronous generators (PMSG). The proposed converter consists of a two-leg three-phase PWM inverter for the generator control and a single-phase half-bridge PWM converter which is connected to the utility grid. For the two separate DC-link voltages, a balancing control is added and the adverse effect of the DC-link voltage ripples on the inverter output voltage is compensated. The control performance of the proposed converter topology for the micro wind turbine system is shown by the simulation results using PSIM software.
    Power Electronics, 2007. ICPE '07. 7th Internatonal Conference on; 11/2007
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    Jul-Ki Seok, Kyung-Tae Kim, Dong-Choon Lee
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    ABSTRACT: Conventional proportional/proportional-integral (P/PI) speed controller for today's servo drives has to be manually tuned at the controller switching set point by trial and error, which may translate into drive system downtime and a subsequent loss of productivity. The adjustable drive performance is heavily dependent on the quality of expert knowledge. The performance becomes inadequate in applications where the operating conditions change in a wide range, i.e., tracking command, acceleration/deceleration time, and load disturbances. In this paper, we discuss the demands on simple controls/setups for industry servo drives. Analyzing the frequency content of the motor torque command, P/PI speed control mode switching is automatically performed with only a prior knowledge of the mechanical time constant. The dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time over the entire set of operating conditions. For a comprehensive comparison of conventional P/PI control scheme, we carried out extensive tests on an actual servo system.
    IEEE Transactions on Industrial Electronics 11/2007; · 5.17 Impact Factor
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    A.G. Abo-Khalil, Dong-Choon Lee, Jeong-Ik Jang
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    ABSTRACT: This paper presents a new control scheme for minimizing the torque ripple of the generator under unbalanced grid voltage for wind turbine systems using doubly-fed induction generators, where the negative sequence component of the rotor current is utilized. It is found that the generator torque ripples are related with the reactive power component. Increase of stator active power ripples caused by reducing the torque ripple is compensated by controlling the active power ripples of grid-side converter. Simulation results using PSCAD and experimental results show that the conventional vector control of DFIG without considering grid voltage unbalance results in excessive oscillations on the stator active and reactive power, and electromagnetic torque. On the other hand, with the proposed control strategy, improved system control and operation such as reducing oscillations of active power and generator torque can be achieved.
    Industrial Electronics, 2007. ISIE 2007. IEEE International Symposium on; 07/2007
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    Dong-Choon Lee, Young-Sin Kim
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    ABSTRACT: This paper proposes a novel control scheme of single-phase-to-three-phase pulsewidth-modulation (PWM) converters for low-power three-phase induction motor drives, where a single-phase half-bridge PWM rectifier and a two-leg inverter are used. With this converter topology, the number of switching devices is reduced to six from ten in the case of full-bridge rectifier and three-leg inverter systems. In addition, the source voltage sensor is eliminated with a state observer, which controls the deviation between the model current and the system current to be zero. A simple scalar voltage modulation method is used for a two-leg inverter, and a new technique to eliminate the effect of the dc-link voltage ripple on the inverter output current is proposed. Although the converter topology itself is of lower cost than the conventional one, it retains the same functions such as sinusoidal input current, unity power factor, dc-link voltage control, bidirectional power flow, and variable-voltage and variable-frequency output voltage. The experimental results for the V/f control of 3-hp induction motor drives controlled by a digital signal processor TMS320C31 chip have verified the effectiveness of the proposed scheme
    IEEE Transactions on Industrial Electronics 05/2007; · 5.17 Impact Factor
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    Jeong-Ik Jang, Dong-Choon Lee
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    ABSTRACT: In this paper, a high-performance control scheme of the PWM converters under nonideal source voltage is proposed. To reduce the harmonic contents in the converter input current due to distorted source voltage, additional current control loops are added to the basic controller. These control loops can eliminate the 5<sup>th</sup> and 7<sup>th</sup> order harmonics which are hardly to be done by using filters. To reduce the DC-link voltage ripples due to unbalanced source voltage, additional control loop is presented. Experimental results show the validity of the proposed control scheme.
    Industrial Technology, 2006. ICIT 2006. IEEE International Conference on; 01/2007
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    A. G. Abo-Khalil, Dong-Choon Lee
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    ABSTRACT: This paper presents a new wind speed estimation method for a variable speed wind turbine system, where the theory of SVR (support vector regression) is applied. The turbine speed is controlled to capture the maximum power according to the optimal tip-speed ratio. The inputs of SVR estimator are the wind turbine power and the rotational speed. By off-line training, a specified function which relates the input with the output is obtained. Then, the wind speed is determined from this predicted off-line function and the instantaneous input. The simulation and experimental results have shown that the wind speed is estimated rapidly and accurately.
    01/2007;
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    A.G. Abo-Khalil, Dong-Choon Lee
    [show abstract] [hide abstract]
    ABSTRACT: In this paper, a novel online capacitance estimation method for a DC-link capacitor in a three-phase AC/DC/AC PWM converter is proposed. A controlled AC voltage with a lower frequency than the line frequency is injected into the DC-link voltage, which then causes AC power ripples at the DC output side. By extracting the AC voltage and power components on the DC output side using digital filters, the capacitance can then be calculated using the support vector regression (SVR) method. A continuous-valued function that plots the fundamental interrelation between a given input (capacitance power) and its corresponding output (capacitance value) can be estimated using SVR and based on the training data. This function then can be used to predict outputs for given inputs that are not included in the training set. The proposed method can be simply implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.15%
    Industry Applications Conference, 2006. 41st IAS Annual Meeting. Conference Record of the 2006 IEEE; 11/2006
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    Jeong-Ik Jang, Young-Sin Kim, Dong-Choon Lee
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    ABSTRACT: In this paper, a novel control method for smoothening the stator active or reactive power ripple components under unbalanced grid voltage for wind power generation using doubly-fed induction generators (DFIG) is proposed. The negative sequence component of the rotor current is used to reduce the active and reactive power ripples, which is extracted by band pass filters. It is shown that reducing the reactive power ripples results in the torque ripple reduction. Simulation results using PSCAD show the proposed control algorithm can reduce the active or reactive power ripple components as well as reducing the torque and speed ripples
    Power Electronics and Motion Control Conference, 2006. IPEMC 2006. CES/IEEE 5th International; 09/2006