Hong-Hee Lee

University of Ulsan, Urusan, Ulsan, South Korea

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Publications (129)103.06 Total impact

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    Cong-Long Nguyen, Hong-Hee Lee
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    Cong-Long Nguyen, Hong-Hee Lee
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    ABSTRACT: This paper develops a digital control scheme with power factor correction for a front-end converter in an electric vehicle battery charger. The front-end converter, which is the boost-type switching-mode rectifier, takes both two roles of the battery charger including the power factor control and the robust charging performance. The proposed control scheme consisting of a charging control algorithm and a grid current control algorithm aims to obtain the unity input power factor and robust performance. Based on the linear averaged model of the converter, the constant-current constant-voltage (CC-CV) charging control algorithm is proposed through only one proportional-integral (PI) controller and a current feed-forward path. In the current control algorithm, we utilize a second band pass filter, a single-phase phase-locked loop (PLL) technique, and a duty-ratio feed-forward term to control the grid current not only to be in phase with the grid voltage but also to be a pure sinusoidal waveform. In order to verify the effectiveness of the proposed control scheme, both simulations and experiments are carried out.
    04/2015; 20(2). DOI:10.6113/TKPE.2015.20.2.18
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    ABSTRACT: Utilizing the optimal capacity of a battery in wind-battery hybrid power systems is crucial to minimize costs. In this paper, we modify the min-max dispatch method to effectively integrate wind power into the grid. In line with the dispatch principle, we define a lifetime cost function, which indicates the battery energy storage system (BESS) cost of dispatching 1 kWh of wind energy, to determine the optimal battery capacity. By using the optimal battery capacity, the operation costs are minimized and the hybrid system is able to dispatch the scheduled power at any dispatching time. Moreover, the short-term power dispatch control is also considered; we smooth the transient power between two consecutive dispatching intervals and control the state of charge (SOC) of the battery by an online-control algorithm. To evaluate the performance of the proposed optimization method and the short-term power dispatch control, we perform several numerical studies with a 3MW wind turbine generator and real wind speed data.
    IEEE Transactions on Industry Applications 01/2015; 51(1). DOI:10.1109/TIA.2014.2330073 · 2.05 Impact Factor
  • Huu-Nhan Nguyen, Hong-Hee Lee
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    ABSTRACT: This paper presents an enhanced space vector modulation (SVM) method to drive matrix converters (MCs) with zero common-mode voltage by using the rotating vectors, which are not used in the traditional SVM for MCs. The reference output voltage vector is generated by a combination of the closer rotating vectors in order to minimize the output distortion. Explicit equations are used to develop the switching patterns so that the proposed SVM method can achieve full control of the output voltage vector and input current phase angle with good performance of the input/output current waveforms. Together with the theoretical analysis, the experimental results are provided to validate the feasibility of the proposed method.
    IEEE Transactions on Power Electronics 01/2015; 30(4):1788-1792. DOI:10.1109/TPEL.2014.2348019 · 5.73 Impact Factor
  • Quoc-Nam Trinh, Hong-Hee Lee
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    ABSTRACT: This paper introduces an advanced current control strategy for grid-connected operations of distributed generation (DG), which supports the DG to transfer a sinusoidal current into the utility grid despite the distorted grid voltage and nonlinear local load conditions. The proposed current controller is designed in the synchronous reference frame and composed of a proportional–integral (PI) controller and a repetitive controller (RC). An RC serves as a bank of resonant controllers, which can compensate a large number of harmonic components with a simple delay function. Hence, the control strategy can be greatly simplified. In addition, the proposed control method does not require the local load current measurement or harmonic analysis of the grid voltage. Therefore, the proposed control method can be easily adopted into the traditional DG control system without installation of extra hardware. Despite the reduced number of sensors, the grid current quality is significantly improved compared with the traditional methods with the PI controller. The operation principle of the proposed control method is analyzed in detail, and its effectiveness is validated through simulated and experimental results.
    IEEE Transactions on Industrial Electronics 12/2014; 61(12):6528-6537. DOI:10.1109/TIE.2014.2320218 · 6.50 Impact Factor
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    ABSTRACT: This paper proposes a phase-locked loop (PLL)- based seamless transfer control method between grid-connected and islanding modes in a three-phase grid-connected inverter. The PLL is used to synchronize the phase of the load voltage to a grid voltage in grid-connected operation, and to generate an angle with the desired frequency in islanding operation. The stability of both the grid current loop for grid-connected operation and the load voltage control loop for islanding operation is analyzed. The phase and magnitude of the load voltage are successively matched to the grid voltage for a seamless transfer from islanding to grid-connected operation. When grid voltage sag occurs, an operating sequence including a PLL operation is suggested in order to transfer smoothly to islanding operation and to provide a stable and seamless voltage to a sensitive load under the voltage sag condition. The simulation and experimental results are carried out to verify the effectiveness of the proposed algorithm.
    IEEE Transactions on Power Electronics 10/2014; 29(10):1-1. DOI:10.1109/TPEL.2013.2290059 · 5.73 Impact Factor
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    Cong-Long Nguyen, Hong-Hee Lee
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    ABSTRACT: Abstract—Use of a battery energy storage system (BESS) becomes a feasible solution to mitigate the intermittent characteristic of wind power resource. Due to the cost, the minimal battery capacity is the crucial requirement to obtain the economic wind-battery system operation. In this paper, an optimal power dispatch strategy is proposed to minimize the storage capacity while the fluctuation mitigation requirement (FMR) imposed by grid codes is satisfied. The power dispatch which is determined through a first-order low-pass filter (FLF) is optimized by adjusting the filter smoothing time constant (FSTC). In order to optimize the FSTC, we introduce two online-based optimization methods that include a linear search approach and a direct computation approach. In the first method, the search objective is the appropriate FSTC to minimize the BESS capacity with a constraint that the power dispatch satisfies the FMR in a time window. In the second method, we demonstrate a mathematical relationship between the FSTC and FMR in 1-sampling time scale; therefore, the optimal solution can be directly computed. As a result, the proposed power dispatch strategy significantly reduces the BESS capacity. In order to verify the effectiveness of the proposed power dispatch strategy, case studies using a 3-MW wind turbine with real wind speed data are shown.
    2014 IEEE, Energy Conversion Congress and Exposition (ECCE), Pittsburgh, PA, USA; 09/2014
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    ABSTRACT: This paper introduces a simple grid-voltage-sensorless control scheme for single-phase power factor correction (PFC) boost converters. The grid voltage waveform is obtained based on the dc output voltage, the switching duty ratio, and a phase-lead compensator. In addition, the duty ratio feedback is utilized to obtain the unity input power factor and the zero harmonic current. The proposed control scheme is designed and mathematically analyzed based on a small-signal model of PFC boost converters. To verify the effectiveness of the proposed control scheme, several simulations and experiments are carried out in two applications: an industrial power system with a 60 Hz grid frequency and a commercial aircraft application with a 400 Hz grid frequency.
    Journal of power electronics 07/2014; 14(4):712-721. DOI:10.613/JPE.2014.14.4.712 · 0.75 Impact Factor
  • Quoc-Nam Trinh, Hong-Hee Lee
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    ABSTRACT: The presence of grid voltage distortion and nonlinear local load are badly impact on the performance of grid-connected distributed generation (DG). This paper introduces an enhanced current control strategy to improve the grid current performance of grid-connected DG under such scenario. The proposed current controller is designed in the synchronous reference frame and composed of a proportional-integral (PI) controller and three resonant controllers tuned at 6n (n = 1, 2, 3) of fundamental frequency. The proposed controller is operated without demand of local load current measurement, which means that no extra hardware is required to achieve good performance of the grid current. The DG with the proposed current controller can transfer a sinusoidal current into the utility grid despite the presence of distorted grid voltage and/or nonlinear local load. Various test cases are considered and experimental results are given to verify the effectiveness of the proposed current controller.
    2014 IEEE 23rd International Symposium on Industrial Electronics (ISIE); 06/2014
  • Quoc-Nam Trinh, Hong-Hee Lee
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    ABSTRACT: This paper introduces a low cost high performance three-phase unified power quality conditioner (UPQC) by using four-switch three-phase inverters. In the proposed UPQC, both shunt and series active power filters (APFs) are developed by using four-switch three-phase inverters so that the number of switching devices in the proposed topology is reduced from twelve in the traditional UPQC down to eight devices. In addition, by inserting an additional capacitor in series with the shunt APF, the DC-link voltage in the proposed UPQC can also be greatly lessened. As a consequence, by using a smaller number of power switches with lower rating voltage in the proposed UPQC system, we can greatly reduce the system cost of the UPQC without degrading the harmonic compensation performance. Design of passive components for the proposed UPQC to achieve a good performance is discussed in detail in this paper. Simulation studies are performed to verify the effectiveness of the proposed topology.
    2014 IEEE 23rd International Symposium on Industrial Electronics (ISIE); 06/2014
  • Huu-Nhan Nguyen, Hong-Hee Lee
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    ABSTRACT: This paper focuses on the common-mode voltage (CMV) reduction in direct matrix converter (MC) using direct space vector modulation (DSVM) (SVM) method. Even though a previous DSVM method can reduce the CMV peak value to 42% compared to the traditional DSVM, it has some drawbacks such as high switching loss, high RMS value of CMV, etc. This paper proposes a new DSVM that can mitigate the peak value of the CMV to 42% compared to the traditional DSVM method with a better performance, lower RMS value of CMV, leakage current and reduced switching losses. The proposed method is easy to carry out via software without any additional hardware. Simulation results are shown to verify the correctness and effectiveness of the proposed method.
    2014 International Power Electronics Conference (IPEC-Hiroshima 2014 ECCE-ASIA); 05/2014
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    Cong-Long Nguyen, Hong-Hee Lee
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    ABSTRACT: By combining a wind turbine with an energy storage system (ESS), we are able to attenuate the intermittent wind power characteristic making the power derived from a wind farm dispatchable. This paper evaluates the influence of the phase delay of the low-pass filter in the conventional smoothing power control on the ESS capacity; longer phase delays require a larger ESS capacity. In order to eliminate the effect of the phase delay, we optimize the power dispatch using a zero-phase low-pass filter that results in a non-delayed response in the power dispatch. The proposed power dispatching method significantly minimizes the ESS capacity. In addition, the zero-phase lowpass filter, which is a symmetrical forward-reverse finite impulse response type, is designed simply with a small number of coefficients. Therefore, the proposed dispatching method is not only optimal, but can also be feasibly applied to real wind farms. The efficacy of the proposed dispatching method is verified by integrating a 3 MW wind turbine into the grid using wind data measured on Jeju Island.
    Journal of Electrical Engineering and Technology 05/2014; 9(3):1080-1088. DOI:10.5370/JEET.2014.9.3.1080 · 0.52 Impact Factor
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    ABSTRACT: This paper develops the brushless dc (BLDC) motor sensorless control system for an automotive fuel pump. The sensorless techniques that are based on a hysteresis comparator and a potential start-up method with a high starting torque are suggested. The hysteresis comparator is used to compensate for the phase delay of the back EMFs due to a low-pass filter (LPF) and also prevent multiple output transitions from noise or ripple in the terminal voltages. The rotor position is aligned at standstill for maximum starting torque without an additional sensor and any information of motor parameters. Also, the stator current can be easily adjusted by modulating the pulse width of the switching devices during alignment. Some experiments are implemented on a single chip DSP controller to demonstrate the feasibility of the suggested sensorless and start-up techniques.
    IEEE Transactions on Power Electronics 03/2014; 29(3):1382-1391. DOI:10.1109/TPEL.2013.2261554 · 5.73 Impact Factor
  • T.D. Nguyen, Hong-Hee Lee
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    ABSTRACT: A new space vector modulation (SVM) process for use in an indirect matrix converter (IMC) has been proposed in this paper to reduce the common-mode voltage (CMV) in a high voltage transfer ratio. The principles of selecting suitable active vectors and then properly arranging the switching sequence in the inverter stage of the IMC are described. The IMC with the new SVM method significantly reduces the peak-to-peak voltage of the CMV without any extra hardware. The new SVM method has some other advantages such as a lower total harmonic distortion of line-to-line output voltage and a reduced switching loss at the inverter stage through a minimum number of switching commutations as compared to the conventional reduced CMV-SVM method. The proposed modulation can be easily implemented in software without any additional hardware modifications. Both simulation and experimental results are shown to demonstrate that the new SVM method can generate good performance of the input/output waveforms and provide CMV reduction.
    IEEE Transactions on Industrial Informatics 02/2014; 10(1):61-72. DOI:10.1109/TII.2013.2255032 · 8.79 Impact Factor
  • T.D. Nguyen, Hong-Hee Lee
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    ABSTRACT: This paper proposes an indirect matrix converter (IMC) topology with dual three-phase outputs and its effective carrier-based pulse width modulation (PWM) method. The proposed IMC topology can independently supply ac power for two three-phase loads from a single three-phase ac power source. This converter consists of a rectifier stage used in traditional three-phase IMC and a five-leg inverter. Besides a proposed IMC topology, the carrier-based PWM method suitable for this converter is also introduced. The proposed PWM method is easily implemented by using only one symmetrical triangular carrier signal to generate the PWM signals for a rectifier and five-leg inverter. Proposed IMC topology features the advantages of conventional three-phase IMC, such as sinusoidal input/output current waveforms, controllable input power factor, and simple commutation at the rectifier stage. Analysis, simulation, and experimental results are provided to demonstrate the advantages of the proposed IMC topology with dual three-phase outputs and to validate the effectiveness of the applied modulation strategy.
    IEEE Transactions on Power Electronics 02/2014; 29(2):569-581. DOI:10.1109/TPEL.2013.2255067 · 5.73 Impact Factor
  • Quoc-Nam Trinh, Hong-Hee Lee
    IET Generation Transmission & Distribution 01/2014; DOI:10.1049/iet-gtd.2013.0636 · 1.31 Impact Factor
  • Quoc-Nam Trinh, Hong-Hee Lee
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    ABSTRACT: This paper proposes an advanced control strategy to enhance performance of shunt active power filter (APF). The proposed control scheme requires only two current sensors at the supply side and does not need a harmonic detector. In order to make the supply currents sinusoidal, an effective harmonic compensation method is developed with the aid of a conventional proportional-integral (PI) and vector PI controllers. The absence of the harmonic detector not only simplifies the control scheme but also significantly improves the accuracy of the APF, since the control performance is no longer affected by the performance of the harmonic tracking process. Furthermore, the total cost to implement the proposed APF becomes lower, owing to the minimized current sensors and the use of a four-switch three-phase inverter. Despite the simplified hardware, the performance of the APF is improved significantly compared to the traditional control scheme, thanks to the effectiveness of the proposed compensation scheme. The proposed control scheme is theoretically analyzed, and a 1.5-kVA APF is built in the laboratory to validate the feasibility of the proposed control strategy.
    IEEE Transactions on Industrial Electronics 12/2013; 60(12):5400-5410. DOI:10.1109/TIE.2012.2229677 · 6.50 Impact Factor
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    Quoc-Nam Trinh, Hong-Hee Lee, Tae-Won Chun
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    ABSTRACT: This paper develops an enhanced harmonic voltage compensator which is implemented with the aid of two repetitive controllers (RCs) in order to improve the output voltage performance of stand-alone distributed generation (DG) systems. The proposed harmonic voltage compensator is able to maintain the DG output voltage sinusoidal regardless of the use of nonlinear and/or unbalanced loads in the load side. In addition, it can offer good steady-state performance under various types of loads and a very fast dynamic response under load variations to overcome the slow dynamic response issue of the traditional RC. The feasibility of the proposed control strategy is verified through simulations and experiments.
    Journal of power electronics 11/2013; 13(6). DOI:10.6113/JPE.2013.13.6.1070 · 0.75 Impact Factor
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  • Journal of power electronics 07/2013; 13(4):712-718. DOI:10.6113/JPE.2013.13.4.712 · 0.75 Impact Factor

Publication Stats

461 Citations
103.06 Total Impact Points

Institutions

  • 2004–2014
    • University of Ulsan
      • • Department of Electrical Engineering
      • • Department of Electrical Engineering
      Urusan, Ulsan, South Korea
  • 2007
    • Ho Chi Minh City University of Technology (HCMUT)
      • Department of Electronics Engineering
      Thành phố Hồ Chí Minh, Thanh pho Ho Chi Minh, Vietnam