Khomfoi, Surin

Preferred name

Khomfoi, Surin

Alternative Name

Khomfoi, S.

Main Affiliation

School of Engineering

surin.kh@kmitl.ac.th

Now showing 1 - 10 of 14

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An open circuit fault diagnostic technique in IGBTS for ac to dc converters applied in microgrid applications
(2011-01-01)
Khomfoi, Surin
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Sae-Kok, Warachart
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Ngamroo, Issarachai
An open circuit fault diagnostic method in IGBTs for the ac to dc converters used in microgrid applications is developed in this paper. An ac to dc converter is a key technology for microgrids in order to interface both distributed generation (DG) and renewable energy resources (RES). Also, highly reliable ac to dc converters are necessary to keep converters in continuous operation as long as possible during power switch fault conditions. Therefore, the proposed fault diagnostic method is developed to reduce the fault detection time and to avoid any other fault alarms because continuous operation is desired. The proposed diagnostic method is a combination of the absolute normalized dc current technique and the false alarm suppression algorithm to overcome the long fault detection time and fault alarm problems. The simulation and experimental results show that the developed fault diagnostic method can perform fault detection within about one cycle. The results illustrate that the reliability of an ac to dc converter interfaced with a microgrid can be improved by using the proposed fault diagnostic method.
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Coordinated Control of Electric Vehicles and Renewable Energy Sources for Frequency Regulation in Microgrids
(2020-01-01)
Jampeethong, Phoompat
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Khomfoi, Surin
A Control technique of electric vehicles (EVs) cooperating with ac microgrids is considered as an important role with integration of renewable energy sources (RES), i.e. wind and solar farms. As known, the intermittent power generations of these RESs can provide significant changes of the frequency in microgrids. Consequently, outputs of these generations are regarded as continuous disturbances. Previously, the ability to permit frequency stabilizing effect was usually neglected in microgrid design; thereupon, the performance of controller may be ineffective to regulate the frequency in such a microgrid. To address this problem, a new coordination of EV, wind farm (WF), and photovoltaic (PV) for microgrid frequency regulation is proposed in this article. In the control design, the proposed adaptive PI controller is developed by using practical proportional integral (PI) controllers. An effect of a small delay is also considered in input-output pairs of the adaptive PI controllers. Simulation model is developed for validating the proposed controller. Simulation results demonstrate that the proposed coordinated control technique of EVs, WF, and PV power generation provides a better frequency regulation performance than a fixed PI controller under various uncertainties such as wind and solar power fluctuations, N-1 outages, disconnection of RESs, load variations, and the number of EVs.
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Transient stability improvement using coordinated control of solar PVs and solid state transformers
(2018-11-01)
Khemmook, Panya
;
Khomfoi, Surin
An optimization coordinated controller applied for solar farm together with a solid state transformer in order to improve transient stability is presented in this paper. Transient stability issues in a modern electrical power grid represent one of the challenge topics for an electrical engineer because uncertain renewable energy resources (RES) are increased because of a demand for green energy requirement. This increased RES can adversely disturb a terminal voltage; consequently, a damage to electrical equipment can happen. In order to solve a transient response issue, it is possible to use a solid state transformer (SST) or intelligent transformer, used to interface between RES and a power grid. SST consists of a set of converters which can be modulated via the converters to maintain the desired voltage levels; thus, this solution can reduce transient response and power fluctuation concurrently. For this reason, this paper presents a controller design for a solar photovoltaic (SPV), connected to a power grid via SST in order to enhance the quality of power injections from RES to improve transient stability of the electrical system. The optimization of a controller model is proposed by modifying a PI controller from a commercial one. The proposed controller is validated with the standard IEEE 39 buses. The validation scenario of both an uncertainty due to time delay accounting for a range of 425ms-525ms and various solar radiation patterns are also taken into account for the evaluation of a proposed controller performance. Simulation results demonstrate that power fluctuation due to uncertain RES can be mitigated by using the proposed controller. Moreover, in case of large disturbances such as a circuit breaker tripping to open a power line due to a fault, the proposed coordinated control of SPV and SST can satisfactorily perform to suppress severe voltage swings within an electrical device rated voltage limit to protect catastrophe damage. The results suggest that the proposed controllers can be alternative solutions in order to solve a transient stability issue due to uncertain increased RES in a modern power grid.
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A cascaded hybrid multilevel inverter incorporating a reconfiguration technique for low voltage DC distribution applications
(2016-01-01)
Khomfoi, Surin
A cascaded hybrid multilevel inverter including a reconfiguration technique for low voltage dc distribution applications is proposed in this paper. A PWM generation fault detection and reconfiguration paradigm after an inverter cell fault are developed by using only a single-chip controller. The proposed PWM technique is also modified to reduce switching losses. In addition, the proposed topology can reduce the number of required power switches compared to the conventional cascaded multilevel inverter. The proposed technique is validated by using a 3-kVA prototype. The switching losses of the proposed multilevel inverter are also investigated. The experimental results show that the proposed hybrid inverter can improve system efficiency, reliability and cost effectiveness. The efficiency of proposed system is 97.45% under the tested conditions. The proposed hybrid inverter topology is a promising method for low voltage dc distribution and can be applied for the multiple loads which are required in a data center or telecommunication building.
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The Development of a 1 kW Mid-Range Wireless Power Transfer Platform for Autonomous Guided Vehicle Applications Using an LCC-S Resonant Compensator
(2025-06-01)
Pairindra, Worapong
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Phongsawat, Suwaphit
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Phophongviwat, Teeraphon
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Khomfoi, Surin
This study presents the development, simulation, and hardware implementation of a 48 V, 1 kW mid-range wireless power transfer (WPT) platform for autonomous guided vehicle (AGV) charging in industrial applications. The system uses an LCC-S compensation topology, selected for its ability to maintain a constant output voltage and deliver high efficiency even under load variations at a typical coil distance of 15 cm. It can also operate at different distances by adjusting the compensator circuit. A proportional–integral (PI) controller is implemented for current regulation, offering a practical, low-cost solution well suited to industrial embedded systems. Compared to advanced control strategies, the PI controller provides sufficient accuracy with minimal computational demand, enabling reliable operation in real-world environments. Current adjustment can be dynamically carried out in response to real-time changes and continuously monitored based on the AGV battery’s state of charge (SOC). Simulation and experimental results validate the system’s performance, achieving over 80% efficiency and demonstrating its feasibility for scalable, robust AGV charging in Industry 4.0 Manufacturing Settings.
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Advanced Control Approach Based on a Super-Twisting Sliding Mode for a Cascade Voltage and Current Control Topologies of a Grid-Supporting Grid-Forming Power Converters
(2023-01-01)
Khongkhachat, Somkiart
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Khomfoi, Surin
This paper introduces advanced control strategies for power electronic converters in distributed generation systems, specifically designed for islanding microgrid systems. The proposed methodology employs a non-linear Sliding Mode Control (SMC) approach, specifically utilizing the Super-Twisting Algorithm (STA) for the regulation of power converters in the Grid-Supporting Grid-Forming (GSGFm) mode. A cascaded control scheme with an outer-loop voltage controller and an inner-loop current controller utilizes a STA method implemented in the Synchronous Rotating Reference Frame (SRRF). The main advantage of the proposed SMC-STA algorithm in the cascade control methodology is its simple structure and easy implementation. The HIL test under normal conditions typically involves analyzing both transient and steady-state behavior when supplying energy to the load. The stability of both voltage and current is compared between the two control strategies. The experimental results provide confirmation of the control performance of the proposed control methodology based on the STA method. The results demonstrate that the STA-based control methodology effectively regulates voltage levels and minimizes fluctuations, surpassing the performance of a classical PI controller. Copyright © 2023 Praise Worthy Prize S.r.l.-All rights reserved.
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Fault diagnosis and reconfiguration for multilevel inverter drive using AI-based techniques
(2007-12-01)
Khomfoi, Surin
;
Tolbert, Leon M.
A fault diagnostic and reconfiguration method for a cascaded H-bridge multilevel inverter drive (MLID) using artificial-intelligence-based techniques is proposed in this paper. Output phase voltages of the MLID are used as diagnostic signals to detect faults and their locations. It is difficult to diagnose an MLID system using a mathematical model because MLID systems consist of many switching devices and their system complexity has a nonlinear factor. Therefore, a neural network (NN) classification is applied to the fault diagnosis of an MLID system. Multilayer perceptron networks are used to identify the type and location of occurring faults. The principal component analysis is utilized in the feature extraction process to reduce the NN input size. A lower dimensional input space will also usually reduce the time necessary to train an NN, and the reduced noise can improve the mapping performance. The genetic algorithm is also applied to select the valuable principal components. The proposed network is evaluated with simulation test set and experimental test set. The overall classification performance of the proposed network is more than 95%. A reconfiguration technique is also proposed. The proposed fault diagnostic system requires about six cycles to clear an open-circuit or short-circuit fault. The experimental results show that the proposed system performs satisfactorily to detect the fault type, fault location, and reconfiguration. © 2007 IEEE.
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Solid state transformers using selective harmonic elimination technique for solar farm applications
(2020-01-01)
Khemmook, Panya
;
Khomfoi, Surin
Solid state transformers using selective harmonic elimination technique for solar farm applications are presented in this paper. As known, the usage of photovoltaic to generate electricity in the form of solar power plants in Thailand is one of the major renewable energy resources. In addition, a Solid-State Transformer (SST) with the application on the solar power plant in Thailand begins to be considered as an alternative solution. Since an SST has the ability to eliminate the core losses during non-operating condition, it can gain more efficiency compared to a conventional transformer. In addition, an SST is smaller and lighter than a conventional transformer because it will normally operate at high frequency. In addition, an SST has a variety of functions, which can be ancillary service devices for an electrical system to help maintain electrical stability, harmonic filter, power fluctuation regulator, power flow controller and increasing of the limitation of transmission lines etc. An SST can gain higher efficiency by using Selective Harmonics Elimination (SHE) techniques for generating Pulse Width Modulation (PWM) signals. This technique offers several advantages such as simple implementation, uncomplicated techniques, and compatibility with various sequences harmonic elimination in a seven-level cascaded h-bridge multilevel inverter. The proposed SHE technique can search a set of angles that gives the lowest percentage of the total harmonic distortion voltage (%THDv). Then, the calculated angles can be used to fine tune again for optimal angle in the proposed controllers. The proposed seven-level cascaded h-bridge multilevel inverter is developed to validate the proposed controller for transferring power via a High Frequency Transformer (HFT) at 10 kHz. The results show that the power losses with the SHE technique using the optimal angles can be reduced up to 1.45% at HFT comparing to quasi-square waveform techniques. The performance of this proposed SST is validated with both simulation and experimental results. The validated results illustrate that the developed SST is a promising solution for a solar farm application.
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A battery energy storage system control technique with ramp rate and C-rate parameter consideration for AC microgrid applications
(2018-01-01)
Prompinit, Krisada
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Khomfoi, Surin
Active power control of a battery energy storage system (BESS) in an ac microgrid to solve an impact of increasing of renewable energy resources (RES) is presented. The variability of active power from these renewable energy resources affects the reliability of the power grid. A BESS is used to connect with an ac microgrid consisting of RES such solar cells to manage the rapid change in flow of active power, so the output active power from RES is regulated within the standard for connecting to the Thailand grid-connected code. Ramp rate effects and characteristics of a battery used in a BESS are considered in proposed control strategy to control the flow of active power. The micro energy management system (μEMS) for calculating the appropriate active power slope is also developed. Therefore, the frequency deviation in the microgrid is regulated by using a proposed both control technique and μEMS. The control of this method ensures that the frequency stability is within the standard range of ±1 Hz in a 50 Hz system. Simulation and experimental results of the proposed method are good agreement, and the active power of the BESS in an ac microgrid can be satisfactorily controlled.
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A sliding mode control strategy for a grid-supporting and grid-forming power converter in autonomous AC microgrids
(2019-03-01)
Khongkhachat, S.
;
Khomfoi, S.
– This paper presents a sliding mode control technique combined with voltage orientation for grid-supporting and grid-forming (GSGFm) function in a power converter, used in AC microgrid during island operation. The robustness sliding mode control method (SMC) can provide stability control system and fast dynamic response. Therefore, a control law is designed using sliding mode techniques, which is based on the combination of continuous and discrete signals to generate the robustness system from uncertainties and disturbances. A sliding mode control approach is adopted in this paper in order to enhance for the inner control loops (level 0) to improve the dynamic response of a lowest hierarchical level based on droop regulated-microgrids. The main objectives of the proposed SMC technique are to keep frequency and voltages at normal values, according to the actual real-reactive power loads absorption. SMC has also produced the reference frequency and the voltage signals. Thereupon, the dynamic frequency and voltage can be regulated with a new control approach and can guarantee power reliability, quality and efficiency during this mode. Finally, the model and the controller design are validated by simulation and experimental results. The results show that the proposed SMC technique can be implemented in a GSGFm power converter for AC microgrid.

Khomfoi, Surin

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