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Various studies on arc detection methods are described. Series AC arc is detected based on the characteristics extracted from arc voltage, frequency, and time domain of the current. Methods of arc detection using artificial intelligence have been studied previously. In the present study, the performance of multiple methods is analyzed by comparing different input parameters and artificial neural networks. In addition to the input parameters presented in the literature, the performance is compared and analyzed using the following parameters: zero-crossing period, frequency average, instantaneous frequency, entropy, combination of fast Fourier transform (FFT) and maximum slip difference, and combination of FFT and frequency average. These parameters and different neural networks are studied in the bounded and unbounded case, and the performance is compared. For different combinations of neural networks and input parameters, another research question is to identify the input parameters to be used if the number of training data is limited. Moreover, this study investigates the change in detection rate depending on the number of training samples. As a result, the minimum dataset size required to obtain the final detection rate is identified.
Chang-Ju Park; Hoang-Long Dang; Sangshin Kwak; Seungdeog Choi. Deep learning-based series AC arc detection algorithms. Journal of Power Electronics 2021, 1 -11.
AMA StyleChang-Ju Park, Hoang-Long Dang, Sangshin Kwak, Seungdeog Choi. Deep learning-based series AC arc detection algorithms. Journal of Power Electronics. 2021; ():1-11.
Chicago/Turabian StyleChang-Ju Park; Hoang-Long Dang; Sangshin Kwak; Seungdeog Choi. 2021. "Deep learning-based series AC arc detection algorithms." Journal of Power Electronics , no. : 1-11.
This paper presents a computational reduction algorithm for applying model predictive control to a three-level four-leg converter. An optimal switching state is selected by only considering 7 voltage vectors located near the reference voltage vector, rather than using 81 voltage vectors in every sampling period, as in the conventional method. The sector, prism, and tetrahedron are sequentially selected using the position of the reference voltage vector. In addition, the seven voltage vectors selected in advance are the vectors constituting the selected tetrahedron. Thus, the proposed method reduces the computational cost and provides an improved model predictive control that does not affect the performance. The proposed method comprises an experimental setup of the proposed three-level four-leg converter to compare its performance with that of the conventional method.
Chan Roh; Sangshin Kwak; Seungdeog Choi. Three-phase three-level four-leg NPC converters with advanced model predictive control. Journal of Power Electronics 2021, 1 -11.
AMA StyleChan Roh, Sangshin Kwak, Seungdeog Choi. Three-phase three-level four-leg NPC converters with advanced model predictive control. Journal of Power Electronics. 2021; ():1-11.
Chicago/Turabian StyleChan Roh; Sangshin Kwak; Seungdeog Choi. 2021. "Three-phase three-level four-leg NPC converters with advanced model predictive control." Journal of Power Electronics , no. : 1-11.
This paper proposes a DC series arc detection algorithm in a photovoltaic (PV) system using an adaptive moving average (AMA). The proposed algorithm uses two moving averages of
Jaechang Kim; Sangshin Kwak; Seungdeog Choi. DC series arc detection algorithm based on adaptive moving average technique. IEEE Access 2021, 9, 1 -1.
AMA StyleJaechang Kim, Sangshin Kwak, Seungdeog Choi. DC series arc detection algorithm based on adaptive moving average technique. IEEE Access. 2021; 9 ():1-1.
Chicago/Turabian StyleJaechang Kim; Sangshin Kwak; Seungdeog Choi. 2021. "DC series arc detection algorithm based on adaptive moving average technique." IEEE Access 9, no. : 1-1.
Owing to the low number of submodules (SMs) in modular multilevel converters (MMCs), especially in medium-voltage applications, the output current and voltage generated by conventional nearest-level control (NLC) methods contain evident distortions. Previously, various hybrid and level-increased NLC methods have been proposed to improve the output voltage quality, but such measures wither increased the complexity or did not regulate all the control objectives simultaneously. To further enhance the output performances of MMCs containing low numbers of SMs, an improved predictive NLC (I-PNLC) method combining NLC and model predictive control (MPC) is proposed, where the output and circulating currents are regulated with the corresponding predicted references, and the output voltage is controlled by the added voltage correction. The proposed I-PNLC not only reduces the output current and voltage total harmonic distortion (THD) considerably but also avoids additional complexity in the control system design. The results of simulations and an experiment are presented to verify the proposed approach, in addition to a comparison of the evaluations of conventional NLC methods.
Minh Hoang Nguyen; Sangshin Kwak. Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion. IEEE Access 2020, 9, 4769 -4783.
AMA StyleMinh Hoang Nguyen, Sangshin Kwak. Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion. IEEE Access. 2020; 9 ():4769-4783.
Chicago/Turabian StyleMinh Hoang Nguyen; Sangshin Kwak. 2020. "Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion." IEEE Access 9, no. : 4769-4783.
When single-phase three-level neutral-point-clamped (NPC) converters operate, there are two main control objectives that need to be met for correct operation. First, the ac source current must be controlled to be sinusoidal. Second, the dc capacitor voltages must be balanced. In original model predictive control (MPC) methods for NPC converters, an optimization process involving an empirical weighting factor design is required to meet both of these objectives simultaneously. This study proposes an MPC approach developed for single-phase three-level NPC converters to meet these objectives using a single reference voltage consisting of a difference-mode term and a common-mode term in each phase. The difference-mode term and the common-mode term are responsible for sinusoidal ac source current synthesis and dc capacitor voltage balancing, respectively. Then, a single cost function compares the adjusted reference voltage with possible voltage candidates to select an optimal switching state, resulting in the smallest cost function value. Different from the conventional MPC method, the proposed approach avoids the selection of weighting factors and the attendance of various control objectives. Thanks to the deterministic approach, the proposed MPC method is straightforward to implement and maintain fast transient performance while guaranteeing the control objectives. Finally, the effectiveness and feasibility of the proposed approach for single-phase three-level NPC are verified through comprehensive experimental results.
Eun-Su Jun; Minh Hoang Nguyen; Sangshin Kwak. Model Predictive Control Method Based on Deterministic Reference Voltage for Single-Phase Three-Level NPC Converters. Applied Sciences 2020, 10, 8840 .
AMA StyleEun-Su Jun, Minh Hoang Nguyen, Sangshin Kwak. Model Predictive Control Method Based on Deterministic Reference Voltage for Single-Phase Three-Level NPC Converters. Applied Sciences. 2020; 10 (24):8840.
Chicago/Turabian StyleEun-Su Jun; Minh Hoang Nguyen; Sangshin Kwak. 2020. "Model Predictive Control Method Based on Deterministic Reference Voltage for Single-Phase Three-Level NPC Converters." Applied Sciences 10, no. 24: 8840.
As one of the most vulnerable components to temperature and temperature cycling conditions in power electronics converter systems in these application fields as wind power, electric vehicles, drive system, etc., power semiconductor devices draw great concern in terms of reliability. Owing to the wide utilization of power semiconductor devices in various power applications, especially insulated gate bipolar transistors (IGBTs), power semiconductor devices have been studied extensively regarding increasing reliability methods. This study comparatively reviews recent advances in the area of reliability research for power semiconductor devices, including condition monitoring (CM), active thermal control (ATC), and remaining useful lifetime (RUL) estimation techniques. Different from previous review studies, this technical review is carried out with the aim of providing a comprehensive overview of the correlation between various enhancing reliability techniques and discussing the corresponding merits and demerits by using 144 related up-to-date papers. The structure and failure mechanism of power semiconductor devices are first investigated. Different failure indicators and recent associated CM techniques are then compared. The ATC approaches following the type of converter systems are further summarized. Furthermore, RUL estimation techniques are surveyed. This paper concludes with summarized challenges for future research opportunities regarding reliability improvement.
Minh Hoang Nguyen; Sangshin Kwak. Enhance Reliability of Semiconductor Devices in Power Converters. Electronics 2020, 9, 2068 .
AMA StyleMinh Hoang Nguyen, Sangshin Kwak. Enhance Reliability of Semiconductor Devices in Power Converters. Electronics. 2020; 9 (12):2068.
Chicago/Turabian StyleMinh Hoang Nguyen; Sangshin Kwak. 2020. "Enhance Reliability of Semiconductor Devices in Power Converters." Electronics 9, no. 12: 2068.
A power take-off (PTO) system for an oscillating water column (OWC) wave energy converter comprises a turbine-generator-power converter. In this study, only the topologies of the power converter that affect the load control algorithm are compared. A power converter for renewable energy is composed of a diode-dc/dc converter and a pulse-width modulation (PWM) converter operating at small and large capacities, respectively. However, selecting a power converter according to the capacity based on the characteristics of the wave energy converter, in which the input energy is highly fluctuating, can significantly reduce the power performance. Thus, to verify load control characteristics according to the topology of the power converter, the turbine-generator-power converter was incorporated in the modeling, and the power performance based on the power converter topology under various wave conditions was analyzed. Further, torque control to obtain the maximum power among load control algorithms was applied under irregular wave conditions, and the power performance and PTO system characteristics according to the torque coefficient were analyzed. The results of this study suggested an increase in the torque coefficient of the maximum power control for the operational stability of the OWC-WEC, and it was confirmed that the RPM characteristics of the PTO system were reduced.
Roh Chan; Kil-Won Kim; Ji-Yong Park; Se-Wan Park; Kyong-Hwan Kim; Sang-Shin Kwak. Power Performance Analysis According to the Configuration and Load Control Algorithm of Power Take-Off System for Oscillating Water Column Type Wave Energy Converters. Energies 2020, 13, 6415 .
AMA StyleRoh Chan, Kil-Won Kim, Ji-Yong Park, Se-Wan Park, Kyong-Hwan Kim, Sang-Shin Kwak. Power Performance Analysis According to the Configuration and Load Control Algorithm of Power Take-Off System for Oscillating Water Column Type Wave Energy Converters. Energies. 2020; 13 (23):6415.
Chicago/Turabian StyleRoh Chan; Kil-Won Kim; Ji-Yong Park; Se-Wan Park; Kyong-Hwan Kim; Sang-Shin Kwak. 2020. "Power Performance Analysis According to the Configuration and Load Control Algorithm of Power Take-Off System for Oscillating Water Column Type Wave Energy Converters." Energies 13, no. 23: 6415.
In this study, the frequency characteristics of series DC arcs are analyzed according to the types of frequency fluctuations caused by inverters in photovoltaic (PV) systems. These frequency fluctuation types used in analysis include centralized frequency fluctuations by three-phase inverter, spread frequency fluctuations by three-phase inverter, and centralized frequency fluctuations by single-phase inverter. To collect arc current data, the frequency fluctuations are generated by inverters in the arc-generating circuit, designed by referring to UL1699B, and the arcs are generated by separating the arc rods of the arc generator. The frequency analysis of the arc current data, collected using an oscilloscope, is conducted using MATLAB. From the results of the frequency characteristics analysis, it is confirmed that the frequencies in the range from 5 to 40 kHz increase after arc generation regardless of the type of frequency fluctuation. In addition, the smaller the current, the greater the increase in frequencies between 5 and 40 kHz after arc generation. Further, in case of arc currents with centralized frequency fluctuations, for larger switching frequencies, the 5 to 40 kHz components increase to a greater extent after arcing.
Jae-Chang Kim; Sang-Shin Kwak. Frequency-Domain Characteristics of Series DC Arcs in Photovoltaic Systems with Voltage-Source Inverters. Applied Sciences 2020, 10, 8042 .
AMA StyleJae-Chang Kim, Sang-Shin Kwak. Frequency-Domain Characteristics of Series DC Arcs in Photovoltaic Systems with Voltage-Source Inverters. Applied Sciences. 2020; 10 (22):8042.
Chicago/Turabian StyleJae-Chang Kim; Sang-Shin Kwak. 2020. "Frequency-Domain Characteristics of Series DC Arcs in Photovoltaic Systems with Voltage-Source Inverters." Applied Sciences 10, no. 22: 8042.
This paper proposes a predictive control method with offset voltage injection for achieving a neutral point (NP) voltage balance of three-phase three-level neutral point clamped (NPC) inverter, without employing a weighting factor. In order to ensure the proper and reliable operation of the NPC inverter, the NP voltage balance should be regulated in addition to the sinusoidal output current. The conventional predictive control methods for NPC has suffered from tedious weighting factor selection. Besides, when the converter’s parameters value and control condition changes, it is cumbersome to empirically redesign the weighting factor. Therefore, the proposed predictive control method without the weighting factor can successfully maintain the balance of NP voltage by utilizing an offset voltage, which is determined according to the difference between the upper and lower capacitor voltages. As a result, the proposed algorithm using the offset voltage injection can control the output currents and maintain the balance of NP voltage. Simulation and experiments are presented to prove the validity of the NP voltage balancing of the proposed control method.
Eun-Su Jun; Minh Hoang Nguyen; Sang-Shin Kwak. Model Predictive Control Method With NP Voltage Balance by Offset Voltage Injection for Three-Phase Three-Level NPC Inverter. IEEE Access 2020, 8, 172175 -172195.
AMA StyleEun-Su Jun, Minh Hoang Nguyen, Sang-Shin Kwak. Model Predictive Control Method With NP Voltage Balance by Offset Voltage Injection for Three-Phase Three-Level NPC Inverter. IEEE Access. 2020; 8 (99):172175-172195.
Chicago/Turabian StyleEun-Su Jun; Minh Hoang Nguyen; Sang-Shin Kwak. 2020. "Model Predictive Control Method With NP Voltage Balance by Offset Voltage Injection for Three-Phase Three-Level NPC Inverter." IEEE Access 8, no. 99: 172175-172195.
Model predictive control has become a tremendously popular control method for power converters, notably a modular multilevel converter, owing to the ability to control various objectives at once with a particular cost function and prominent dynamic performance. However, the high number of submodules in cascaded control means that the model predictive control for the modular multilevel converter suffers from a computational burden. Several approaches focused on reducing the computational burden based on limiting the number of possible switching states (possible choices) to be evaluated at each sampling instant. The dynamic performance of the modular multilevel converter is degraded in a transient state, despite the reduced computational burden. This paper presents an improved indirect model predictive control method to reduce the computational burden and enhance the dynamic performance. The proposed approach considers the steady-state and transient state individually and applies a different range of choices for each specific case. The range of choices during the steady-state is limited in order to reduce the computational burden without deteriorating the output quality, whereas the number of choices will be increased during the transient state to guarantee dynamic performance. The results that were obtained by implementing an experiment on a laboratory setup of a single-phase modular multilevel converter are presented in order to verify the proposed approach’s effectiveness. From the experimental setup, the computational time in the proposed approach was reduced by about 75% when compared with the conventional indirect model predictive control, whereas keeping fast dynamic performance.
Minh Hoang Nguyen; Sangshin Kwak. Improved Indirect Model Predictive Control for Enhancing Dynamic Performance of Modular Multilevel Converter. Electronics 2020, 9, 1405 .
AMA StyleMinh Hoang Nguyen, Sangshin Kwak. Improved Indirect Model Predictive Control for Enhancing Dynamic Performance of Modular Multilevel Converter. Electronics. 2020; 9 (9):1405.
Chicago/Turabian StyleMinh Hoang Nguyen; Sangshin Kwak. 2020. "Improved Indirect Model Predictive Control for Enhancing Dynamic Performance of Modular Multilevel Converter." Electronics 9, no. 9: 1405.
Electric compressor systems for air conditioning operations are an essential part in battery electric vehicle systems, which are not applicable to conventional belt-driven compressors due to no combustion engines. Three-phase voltage source inverters (VSI) and interior permanent magnet (IPM) motors are generally used for electric compressor systems in battery electric vehicles. Direct current (DC)-link capacitors are a critical component in the power converter systems, which affect the cost, size, performances and scale. Metallized polypropylene film capacitors are considered more reliable than conventional electrolytic capacitors for high temperature environments such as electric vehicle applications. This paper presents comprehensive comparisons and evaluations of electric compressors with two types of DC-link capacitors. Based on a 5 kW IPM motor drives and a VSI with a nominal DC voltage of 360 V for electric compressors, performances with electrolytic and film capacitors have been evaluated by experimental tests.
Namhun Kim; Changju Park; Sangshin Kwak; Jeihoon Baek. Experimental Comparisons and Evaluations of Different Types of DC-link Capacitors for VSI-Based Electric Compressors in Battery Electric Vehicle Systems. Electronics 2020, 9, 1276 .
AMA StyleNamhun Kim, Changju Park, Sangshin Kwak, Jeihoon Baek. Experimental Comparisons and Evaluations of Different Types of DC-link Capacitors for VSI-Based Electric Compressors in Battery Electric Vehicle Systems. Electronics. 2020; 9 (8):1276.
Chicago/Turabian StyleNamhun Kim; Changju Park; Sangshin Kwak; Jeihoon Baek. 2020. "Experimental Comparisons and Evaluations of Different Types of DC-link Capacitors for VSI-Based Electric Compressors in Battery Electric Vehicle Systems." Electronics 9, no. 8: 1276.
A predictive control method using injected offset voltage to achieve neutral point (NP) voltage balance of three-phase three-level neutral point clamped (NP) rectifiers, without employing a weighting factor, is proposed in this study. One of the biggest problems with the three-level NP rectifiers is the dc link capacitor voltage imbalance. Therefore, it is necessary to maintain the balance of the NP voltage in addition to synthesize the three-phase sinusoidal input current by control methods. Conventional predictive control methods for the NP rectifiers have used a weighting factor in a cost function that determines the control ratio of the input currents and the capacitor voltage balance. As a result, it is burdensome to empirically redesign the weighting factor when the rectifiers’ parameter values and control conditions change. Unlike the conventional methods, the proposed approach without the weighting factor can significantly eliminate differences between two DC capacitor voltages by utilizing an offset voltage, which is generated by using the difference between the upper and lower capacitor voltages. Consequently, the proposed approach using the offset voltage injection can control the input currents and retain the balance of NP voltage. Simulation and experiments are presented to verify the correctness of the NP voltage balancing of the proposed control method.
Eun-Su Jun; Minh Hoang Nguyen; Sangshin Kwak. Three-Phase Three-Level Neutral Point Clamped Rectifier with Predictive Control Method without Employing Weighting Factor. Applied Sciences 2020, 10, 5149 .
AMA StyleEun-Su Jun, Minh Hoang Nguyen, Sangshin Kwak. Three-Phase Three-Level Neutral Point Clamped Rectifier with Predictive Control Method without Employing Weighting Factor. Applied Sciences. 2020; 10 (15):5149.
Chicago/Turabian StyleEun-Su Jun; Minh Hoang Nguyen; Sangshin Kwak. 2020. "Three-Phase Three-Level Neutral Point Clamped Rectifier with Predictive Control Method without Employing Weighting Factor." Applied Sciences 10, no. 15: 5149.
For so many years, silicon (Si) IGBTs have been widely utilized in power converters for low-to-medium voltage high-power applications. However, the ever-increasing requirements to improve power density, power quality, and efficiency of power converters have urged researchers to explore alternative technologies such as silicon-carbide (SiC) MOSFETs. SiC devices fill the mentioned gaps with increased voltage blocking capability, higher switching speed, and lower on-state resistance; yet, their price is much more elevated. Both technologies are adopted in matrix rectifiers (MRs), which have recently gained attention for on-board electric vehicle (EV) charger and battery energy storage system (BESS) applications because of their controllable bidirectional power flow and compact size. A MR contains bidirectional switches made up of two power devices, doubling the device count and cost to conventional voltage source converters (VSCs). In this paper, we compare in terms of efficiency four types of MRs, each one consisting of a specific bidirectional switch configuration. Among these switches, we propose a cost-effective hybrid configuration consisting of Si IGBTs and SiC MOSFETs for straightforward commutations during the charging mode of matrix rectifiers. Also, the proposed configuration is compared to other typical bidirectional switch configurations. To perform these comparisons, the switching energy losses in 1200 V commercial IGBTs and MOSFETs, constituting the bidirectional switches, are measured through the double-pulse test (DPT). Performance comparisons of the MRs are supported through a simulator and verified via experimental work, where the proposed arrangement results in a cost-effective solution in MRs operating with switching frequencies up to 50 kHz and further.
Bryan Gutierrez; Sang-Shin Kwak. Cost-Effective Matrix Rectifier Operating With Hybrid Bidirectional Switch Configuration Based on Si IGBTs and SiC MOSFETs. IEEE Access 2020, 8, 136828 -136842.
AMA StyleBryan Gutierrez, Sang-Shin Kwak. Cost-Effective Matrix Rectifier Operating With Hybrid Bidirectional Switch Configuration Based on Si IGBTs and SiC MOSFETs. IEEE Access. 2020; 8 (99):136828-136842.
Chicago/Turabian StyleBryan Gutierrez; Sang-Shin Kwak. 2020. "Cost-Effective Matrix Rectifier Operating With Hybrid Bidirectional Switch Configuration Based on Si IGBTs and SiC MOSFETs." IEEE Access 8, no. 99: 136828-136842.
Capacitors are critical components of power converter systems as they influence the cost, size, performance, and scale of such systems. However, capacitors exhibit the highest degeneration and breakdown rates among all power converter components due to their wear-out failures and short lifespans. Therefore, condition monitoring is a vital process to estimate the health status of capacitors and to provide predictive maintenance for ensuring stability in the operation of power converter systems. The equivalent series resistance (ESR) and the capacitance of the capacitor are two widely used parameters for evaluating the health status of capacitors. Unlike the ESR, the capacitance of a capacitor is suitable for the health monitoring of various types of capacitors; therefore, it is more preferable for large-scale systems. This paper presents an overview of previous research addressing this aspect of capacitors and provides a better understanding of the capacitance monitoring of capacitors utilized in power converter systems.
Hoang-Long Dang; Sangshin Kwak. Review of Health Monitoring Techniques for Capacitors Used in Power Electronics Converters. Sensors 2020, 20, 3740 .
AMA StyleHoang-Long Dang, Sangshin Kwak. Review of Health Monitoring Techniques for Capacitors Used in Power Electronics Converters. Sensors. 2020; 20 (13):3740.
Chicago/Turabian StyleHoang-Long Dang; Sangshin Kwak. 2020. "Review of Health Monitoring Techniques for Capacitors Used in Power Electronics Converters." Sensors 20, no. 13: 3740.
Nearest-level control (NLC) is a popular technique used in modular multilevel converters (MMCs) with a large number of submodules (SMs) owing to the NLC’s flexibility and ease of implementation. However, in medium-voltage applications, MMCs contain a relatively low number of SMs, and the drawbacks of the NLC methods emerge, wherein the poor quality of output voltages and currents result in high total harmonic distortion, large ripples in SM capacitor voltages, and unsuppressed circulating currents. Several NLC methods have been proposed to handle these problems, but they do not satisfy all the control objectives simultaneously. This paper proposed a modified NLC capable of enhancing the output quality of MMCs with low number of SMs without deteriorating the control objectives. Unlike previously reported NLC methods, instead of directly calculating the numbers of SMs from the upper and lower arm voltage references, the difference and total number of SMs are obtained from the output voltage reference and circulating current control, respectively. Hence, the numbers of SMs in the upper and lower arms are acquired by simply solving a system of first-order two-variable equations. The simulated and experimental results for a single-phase MMC system were used to verify the appropriateness and effectiveness of the proposed modified NLC method.
Minh Hoang Nguyen; Sangshin Kwak. Nearest-Level Control Method With Improved Output Quality for Modular Multilevel Converters. IEEE Access 2020, 8, 110237 -110250.
AMA StyleMinh Hoang Nguyen, Sangshin Kwak. Nearest-Level Control Method With Improved Output Quality for Modular Multilevel Converters. IEEE Access. 2020; 8 ():110237-110250.
Chicago/Turabian StyleMinh Hoang Nguyen; Sangshin Kwak. 2020. "Nearest-Level Control Method With Improved Output Quality for Modular Multilevel Converters." IEEE Access 8, no. : 110237-110250.
전력변환장치를 이용한 제어는 빠른 응답을 얻을 수 있기 때문에 최근에 연구가 많이 되고 있다. 하지만 기존에 파력발전용 전력변환장치 제어를 위한 비례적분제어(Proportional Integral control, PI-Control) 기반의 펄스폭변조기법(Pulse Width Modulation, PWM)은 입력 에너지가 수초단위로 변화하는 파랑에너지 특성상 빠른 과도 응답을 얻기가 어렵다. 매 샘플링 스텝마다 최적의 스위칭 상태를 사용하는 것이 아니라 기준 전압 벡터 인근에 위치한 다양한 스위칭 상태를 이용해서 제어하기 때문에 과도 상태가 발생 했을 때 기준 전류를 빠른 시간 안에 추종할 수 없게 한다. 그래서 본 논문에서는 파력발전용 전력변환장치의 모델을 이용한 전류예측제어(Model Predictive Current Control, MPCC)를 통해 빠른 동특성을 갖는 최적제어기법을 제안한다. 제안하는 방법은 전력변환장치의 모델을 통한 다음 스텝의 전류를 예측하고, 예측된 전류와 기준 전류를 이용해 비용 함수(Cost Function)을 구성한 다음 매 샘플링 스텝마다 최적의 스위칭 상태 하나를 선택한다. 기존의 방법처럼 매 샘플링 마다 다양한 스위칭 상태를 사용하는 것이 아닌 기준 전압 벡터와 가장 인접한 최적의 전압 벡터 즉 최적의 스위칭 상태 하나만 사용하기 때문에 빠른 과도 응답을 얻을 수 있다. 제안하는 방법의 제어기 성능을 검증하기 위해 PSIM을 이용해 시뮬레이션을 진행하였고, 기존의 PI기반의 PWM방법(PI-PWM)과 제안하는 방법을 정상상태와 다양한 과도상태 비교 분석을 통해 제안하는 방법의 성능을 입증한다.
Roh Chan; Jong-Su Choi; Sang-Shin Kwak; Kyong-Hwan Kim. A Study on Model Predictive Current Control Method of Power Converter for Fast Dynamics Response in OWC Wave Energy Converter. Journal of the Korean Society for Marine Environment & Energy 2020, 23, 1 -12.
AMA StyleRoh Chan, Jong-Su Choi, Sang-Shin Kwak, Kyong-Hwan Kim. A Study on Model Predictive Current Control Method of Power Converter for Fast Dynamics Response in OWC Wave Energy Converter. Journal of the Korean Society for Marine Environment & Energy. 2020; 23 (1):1-12.
Chicago/Turabian StyleRoh Chan; Jong-Su Choi; Sang-Shin Kwak; Kyong-Hwan Kim. 2020. "A Study on Model Predictive Current Control Method of Power Converter for Fast Dynamics Response in OWC Wave Energy Converter." Journal of the Korean Society for Marine Environment & Energy 23, no. 1: 1-12.
A model predictive current control method is proposed to reduce switching losses in an AC-DC matrix converter. In the proposed control strategy, several vectors are selected from among all possible switching vectors for a given location of the input current reference. The switching vector that minimizes the cost function is applied to the converter in the next sampling period. The principle of the proposed method involves clamping the selected switches to stop performing the switching operation to minimize the number of switchings in every sampling cycle. The total efficiency of the AC-DC matrix converter under the proposed strategy is 91.2% whereas that of the conventional strategy is 89.7%. In addition, unity-power-factor operation is guaranteed and smooth and sinusoidal waveforms are achieved. Finally, simulation and experimental results are demonstrated to confirm the validity of the proposed control strategy.
Eun-Su Jun; Hoang-Long Dang; Sangshin Kwak. Predictive Control Method Based on Adjacent Vector Confinement Technique for a Three-Phase AC-DC Matrix Converter with High Efficiency. Electronics 2019, 8, 1535 .
AMA StyleEun-Su Jun, Hoang-Long Dang, Sangshin Kwak. Predictive Control Method Based on Adjacent Vector Confinement Technique for a Three-Phase AC-DC Matrix Converter with High Efficiency. Electronics. 2019; 8 (12):1535.
Chicago/Turabian StyleEun-Su Jun; Hoang-Long Dang; Sangshin Kwak. 2019. "Predictive Control Method Based on Adjacent Vector Confinement Technique for a Three-Phase AC-DC Matrix Converter with High Efficiency." Electronics 8, no. 12: 1535.
In a current source rectifier such as a matrix rectifier, input voltage and current cannot be in phase unless an additional input power factor control technique is implemented. This paper proposes such a technique for a matrix rectifier using power-based space vector modulation (SVM). In the proposed method, the modulation index and phase required in order to apply the SVM are calculated based on the active and reactive power of the rectifier for intuitive power factor control. The active power that the rectifier should generate for the regulation of the output inductor current is obtained by the PI (proportional-integral) controller. The reactive power, which is supplied by the rectifier for adjustment of the power factor, is assigned differently depending on the output condition: for the output condition capable of unity power factor, it is set to a negative value of reactive power of the input capacitor, and when the unity power factor is not achievable, it is set with the maximum reactive power the rectifier can generate under the given condition to attain the maximum possible input power factor. It is determined whether the given condition is the light load condition by comparing the absolute value of the reactive power supplied by the input capacitor with the maximum rectifier reactive power that can be produced under the given condition. The SVM based on the active and reactive power of the rectifier in this technique allows the input power factor control to be intuitive and simple. The performance and feasibility of the technique were proved by simulation and experimentation.
Jae-Chang Kim; Dongyeon Kim; Sang-Shin Kwak; Kim. Direct Power-Based Three-Phase Matrix Rectifier Control with Input Power Factor Adjustment. Electronics 2019, 8, 1427 .
AMA StyleJae-Chang Kim, Dongyeon Kim, Sang-Shin Kwak, Kim. Direct Power-Based Three-Phase Matrix Rectifier Control with Input Power Factor Adjustment. Electronics. 2019; 8 (12):1427.
Chicago/Turabian StyleJae-Chang Kim; Dongyeon Kim; Sang-Shin Kwak; Kim. 2019. "Direct Power-Based Three-Phase Matrix Rectifier Control with Input Power Factor Adjustment." Electronics 8, no. 12: 1427.
High modularity, easy scalability, and superior harmonic performance, comprising the topology with the most potential for medium-to high-voltage high-power applications, are representative features of a modular multilevel converter (MMC). Each application of a MMC requires a proper scheme such that it conforms to control objectives such as correct submodule capacitor voltage balancing control and the suppression of circulating current. Over the past few years, various studies have been presented that meet the MMC requirements through both classical control-based pulse-width modulation and model predictive control, although some drawbacks exist for both control concepts. The dynamic performance of the classical control methods with proportional-integral or proportional-resonant controllers is unsatisfactory, and the requirement of proportional-integral parameters tuning procedure makes converter operation performance depends on proportional-integral parameters adjustment. Meanwhile, model predictive control performance depends significantly on the mathematical model of a system, and weighting factor selection is tedious. In this paper, we propose an improved phase-shifted carrier pulse-width modulation method and capacitor voltage balancing control that inherits the merits from both classical control and model predictive control. Meanwhile, the proposed control method eliminates the requirement of the tedious proportional-integral parameters tuning procedure and improves the dynamic performance compared with the conventional phase-shifted carrier pulse-width modulation-based proportional-integral controller method. Simulations and experiments were conducted to demonstrate the proposed method’s properness.
Hoang Nguyen; Sangshin Kwak; Taehyung Kim. Phase-Shifted Carrier Pulse-Width Modulation Algorithm With Improved Dynamic Performance for Modular Multilevel Converters. IEEE Access 2019, 7, 170949 -170960.
AMA StyleHoang Nguyen, Sangshin Kwak, Taehyung Kim. Phase-Shifted Carrier Pulse-Width Modulation Algorithm With Improved Dynamic Performance for Modular Multilevel Converters. IEEE Access. 2019; 7 (99):170949-170960.
Chicago/Turabian StyleHoang Nguyen; Sangshin Kwak; Taehyung Kim. 2019. "Phase-Shifted Carrier Pulse-Width Modulation Algorithm With Improved Dynamic Performance for Modular Multilevel Converters." IEEE Access 7, no. 99: 170949-170960.
A switching losses reduction technique for the model predictive control (MPC) algorithm, which uses double-vector in the three-phase rectifier, is presented. The proposed method controls the output voltage of the rectifier by using reference rectifier input voltages with the offset voltage injection to reduce the switching losses. One leg with the largest source current among the three legs in the rectifier is clamped to either the positive or negative output voltage in the proposed method. The proposed method calculates the offset voltage on the basis of the future rectifier input voltages obtained by the reference rectifier input voltage, output voltage, and the source currents in every sampling period, so the clamping region in the leg conducting the largest input current is optimally varied depending on the reference rectifier input voltages and the source currents. Therefore, the proposed method can reduce the switching losses of the rectifier regardless of the different source power factor angle. Due to the effects of clamped legs, the quality of the input current waveform inevitably deteriorated. Thus, in the proposed method, double vectors were utilized to avoid degradation of current qualities and achieved compromised performance by reducing switching losses and keeping the current waveform quality. A performance comparison between the conventional method and the proposed method was made to show performance differences. Additionally, the simulation and experiment were conducted to verify the effectiveness of the proposed method.
Eun-Su Jun; Sangshin Kwak; Jun; Kwak. A Compromising Approach to Switching Losses and Waveform Quality in Three-phase Voltage Source Converters with Double-vector based Predictive Control Method. Electronics 2019, 8, 1372 .
AMA StyleEun-Su Jun, Sangshin Kwak, Jun, Kwak. A Compromising Approach to Switching Losses and Waveform Quality in Three-phase Voltage Source Converters with Double-vector based Predictive Control Method. Electronics. 2019; 8 (11):1372.
Chicago/Turabian StyleEun-Su Jun; Sangshin Kwak; Jun; Kwak. 2019. "A Compromising Approach to Switching Losses and Waveform Quality in Three-phase Voltage Source Converters with Double-vector based Predictive Control Method." Electronics 8, no. 11: 1372.