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    An open circuit fault diagnostic technique in IGBTS for ac to dc converters applied in microgrid applications
    (2011-01-01) ;
    Sae-Kok, Warachart
    ;
    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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    Application of electrolyzer to alleviate power fluctuation in a stand alone microgrid based on an optimal fuzzy PID control
    (2012-12-01)
    Due to the high intermittent power generations from wind and photovoltaic in the microgrid (MG) system, these result in the severe power fluctuation. When the fuel cell (FC) equipped with the aqua electrolyzer (AE) has been installed in the MG, in addition to hydrogen production for FC, the absorbed power by AE can be controlled to alleviate the power fluctuation. This paper proposes the coordinated control of AE and FC to solve the power fluctuation problem in the MG. By control of the power absorption by AE and the power production by FC, the power fluctuation in the MG can be suppressed. The optimal fuzzy logic based-proportional-integral-derivative (FLPID) is used to design the controllers of AE and FC. Without trial and error as in the conventional FLPID controller design, scale factors, membership functions and control rules of the optimal FLPID controller are automatically and simultaneously tuned by a bee colony optimization. Simulation results confirm the superior stabilizing effect of the proposed optimal FLPID controller in comparison with the conventional FLPID controller under several system disturbances. © 2012 Elsevier Ltd. All rights reserved.
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    Application of electrolyzer system to enhance frequency stabilization effect of microturbine in a microgrid system
    (2009-09-01)
    Vachirasricirikul, Sitthidet
    ;
    ;
    It is well known that the power output of microturbine can be controlled to compensate for load change and alleviate the system frequency fluctuations. Nevertheless, the microturbine may not adequately compensate rapid load change due to its slow dynamic response. Moreover, when the intermittent power generations from wind power and photovoltaic are integrated into the system, they may cause severe frequency fluctuation. In order to study the fast dynamic response, this paper applies electrolyzer system to absorb these power fluctuations and enhance the frequency control effect of microturbine in the microgrid system. The robust coordinated controller of electrolyzer and microturbine for frequency stabilization is designed based on a fixed-structure H<inf>∞</inf> loop shaping control. Simulation results exhibit the robustness and stabilizing effects of the proposed coordinated electrolyzer and microturbine controllers against system parameters variation and various operating conditions. Crown Copyright © 2009.
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    Alleviation of power fluctuation in a microgrid by electrolyzer based on optimal fuzzy gain scheduling PID control
    (2014-01-01)
    Chaiyatham, Theerawut
    ;
    This paper presents an application of the electrolyzer (EZ) to alleviate the power fluctuation in a microgrid with hybrid power generations from wind, photovoltaic array, fuel cell, and diesel engine. In this microgrid, the intermittent power generations from wind and photovoltaic arrays cause severe power fluctuation. With the fast response of EZ, the power absorbed by EZ can be controlled to compensate for the power fluctuation, in addition to the hydrogen production for fuel cell. The structure of the active and reactive power controllers of EZ is the fuzzy gain scheduling of a proportional-integral-derivative (FGS-PID) controller. Without trial and error, the scale factors, membership functions, and control rules of the FGS-PID controller are automatically optimized by bee colony optimization. A simulation study confirms that the proposed EZ with optimal FGS-PID controller is much superior to the optimal PID controller in terms of damping effect, robustness against disturbances, and hydrogen production. © 2014 Institute of Electrical Engineers of Japan.
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    Robust coordinated control of electrolyzer and PSS for stabilization of microgrid based on PID-based mixed H 2/H ∞ control
    (2012-09-01)
    In the stand-alone microgrid with hybrid wind, fuel cell (FC) with electrolyzer (EZ) and diesel generations, the intermittent wind power may cause the serious power fluctuation. In addition to the hydrogen production for FC, the EZ can be used to alleviate power fluctuation by an appropriate control of the absorbed power. Nevertheless, the EZ may fail to suppress the power fluctuation due to large disturbances. To enhance the EZ control performance, a power system stabilizer (PSS) which is assumed to be equipped with a diesel generator can be used. This paper proposes the robust coordinated control of EZ and PSS for microgrid stabilization. The structure of power controller of EZ and PSS is a proportional-integral-derivative (PID). To improve the damping performance and robustness of EZ controller and PSS, the PID parameters of both EZ and PSS are simultaneously tuned based on the mixed H <inf>2</inf>/H <inf>∞</inf> control by bee colony optimization. Simulation studies show that the stabilizing performance and robustness of the proposed EZ and PSS are superior to those of the individual device under system uncertainties such as various wind patterns, loading conditions and severe faults. © 2012 Elsevier Ltd.
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    Design of Optimal SMES Controller Considering SOC and Robustness for Microgrid Stabilization
    (2016-10-01) ;
    Vachirasricirikul, Sitthidet
    The microgrid with wind and photovoltaic (PV) power sources unavoidably encounters the power fluctuation problem. To solve this problem, the superconducting magnetic energy storage (SMES) can be used. Nevertheless, large power fluctuation from wind and PV sources, and severe system faults may cause the overcharge or deep-discharge state of SMES. These abnormal states highly degrade the dynamic performance of the SMES. To handle these situations, this paper concentrates on the new SMES power controller design considering state-of-charge (SOC), robustness, and optimal inductance of the superconducting coil for microgrid stabilization. The active and reactive power controllers of SMES are represented by the proportional-integral (PI) control. The SOC deviation control and the mixed H<inf>2</inf>/H<inf>∞</inf> control are proposed to optimize the SMES coil inductance and PI parameters. Simulation study is performed to signify the control effect of the proposed SMES.
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    A bee colony optimization based-fuzzy logic-pid control design of electrolyzer for microgrid stabilization
    (2012-09-01)
    Chaiyatham, Theerawut
    ;
    This paper proposes the optimal fuzzy logic based-proportional-integral-derivative (FLPID) controller design of the electrolyzer (EZ) by a bee colony optimization (BCO) for microgrid (MG) stabilization. The study MG system consists of wind power (WP), photovoltaic (PV), fuel cell (FC) equipped with EZ, diesel generator, and load. The intermittent power generations from WP and PV cause the severe power fluctuation in the MG. To alleviate power fluctuation, the EZ which is normally used to produce the hydrogen input for FC, can be applied. By control of active and reactive powers absorbed by EZ, the power fluctuation can be stabilized. The structure of active and reactive power controllers of EZ is the FLPID which consists of scale factors (SCs), membership functions (MFs), and control rules (CRs). Without trial and error, SCs, MFs, and CRs of the FLPID controller are automatically optimized by a BCO. Simulation study confirms that the proposed EZ with an optimal FLPID controller is much superior to the EZ with a conventional FLPID controller or an optimal PID controller in terms of stabilizing effect and robustness against various loading conditions and severe disturbances. © 2012 ICIC International.
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    Robust frequency stabilization in a microgrid system
    (2009-12-16)
    Vachirasricirikul, S.
    ;
    ; ;
    Chaiyatham, T.
    This paper proposes a new design of a robust control and monitoring system (RCMS) for robust stabilization of frequency fluctuation in a microgrid (MG) system. In MG system, the power sources consists of wind power (WP), photovoltaic (PV), microturbine (MT) and fuel cell (FC). Due to WP, PV and load fluctuations, the frequency stabilization of RCMS is performed by adjusting the power outputs of MT and electrolyzer system (ES) in both islanding and interconnected utility grid operations. The structure of MT and ES controllers is a proportional integral (PI). To enhance the robustness of designed controllers against system uncertainties, controller parameters of MT and ES are concurrently tuned by the particle swarm optimization based on a specified-structure H<inf>∞</inf> loop shaping control. Simulation results display the effectiveness and robustness of the proposed RCMS against system parameters variation and several operating conditions.
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    Microgrid stabilization using controllable electrolyzer & fuel cell based on bee colony optimization of fuzzy-pid controller
    (2010-12-01)
    Chaiyatham, Theerawut
    ;
    Due to the intermittent power generations from wind and photovoltaic in the microgrid, these result in the power fluctuation. To suppress power fluctuation, the coordinated controls of aqua electrolyzer (AE) and fuel cell (FC) can be applied as the controllable distributed generations. In this paper, a bee colony optimization (BCO) is proposed to design the optimal fuzzy logic based-proportional-integral-derivative (FLPID) controller of AE and FC. Without trial and error as in the conventional FLPID controller design, scale factors, membership functions and control rules of the optimal FLPID controller are automatically and simultaneously tuned by the BCO. Simulation results confirm the superior effect of the proposed optimal FLPID controller in comparison with the conventional FLPID controller.
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    Microgrid stabilization by superconducting magnetic energy storage with optimal energy capacity by genetic algorithm
    (2012-01-01)
    In a microgrid with wind and photovoltaic power generations, the intermittent power from these sources may cause a large power fluctuation. Besides, when the severe fault occurs in the system, it may cause the transient power fluctuation. If the power fluctuation cannot be maintained in the acceptable range, the system stability may be deteriorated. To compensate for fast power fluctuation, a superconducting magnetic energy storage (SMES) can be applied. This paper proposes a new optimization technique of SMES power controller with optimal energy capacity. The power controller structure is the first-order lead-lag compensator. The optimization problem of power controller parameters, coil inductance and initial coil current is formulated based on an enhancement of system damping and a minimization of initial energy capacity of SMES. The genetic algorithm is applied to achieve all optimized parameters. Simulation results confirm the control effect of the SMES with optimized energy capacity against various disturbances. © 2012 Praise Worthy Prize S.r.l. - All rights reserved.