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- 저자 : Mokhlis Hazlie (검색결과 3 건)
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Rosli Hazwani Mohd,Mokhlis Hazlie,Mansor Nurulafiqah Nadzirah,Sapari Norazliani Md,Halim Syahirah Abd 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.3
Islanding of distribution network can severely aff ect the system frequency and voltage due to imbalance power between generation and load demand. In a standard practice, distributed generations (DGs) are required to be disconnected when islanding occurs because of the technical concerns. However, the practice is not an ideal approach as the DGs can be used to energize some of the loads in the system. However, DGs can be allowed to continuously operate by addressing the power imbalance between generation and load demand by means of load shedding scheme (LSS). Therefore, this paper proposes an improved LSS based on modifi ed Discrete Evolutionary Programming (MDEP) and analytic hierarchy process (AHP). Two factors, which are the minimum power imbalance and minimum stability index are considered to attain a stable frequency and voltage of the system. The MDEP starts by short-listing the bus candidates to be shed while AHP method decides on the rank of the load to be shed considering both the power imbalance and stability index. The performance of the proposed LSS is evaluated based on the frequency responses. The eff ectiveness of the proposed scheme is tested on an 11 kV Malaysian distribution network, energized by the grid and two mini-hydros. Simulation results show a signifi cant improvement in the consistency (73.3%) of the proposed MDEP and converged at lower iteration number. Comparative study reveals the eff ectiveness of the proposed LSS in stabilizing the system frequency without frequency overshoot, a reduction of 68.4% and 17.7% of operating time during islanding and overloading events. Voltage profi le of the system is also improved for all buses.
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Jasrul Jamani Jamian,Wardiah Mohd Dahalan,Hazlie Mokhlis,Mohd Wazir Mustafa,Lim Zi Jie,Mohd Noor Abdullah 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.4
Optimal Distributed Generation (DG) output and reconfiguration are among the well accepted approach to reduce power loss in a distribution network. In the past, most of the researchers employed optimal DG output and reconfiguration separately. In this work, a simultaneous DG output and reconfiguration analysis is proposed to maximize power loss reduction. The impact of the separated analysis and simultaneous analysis are investigated. The test result on the 33 bus distribution network with 3 units of DG operated in PV mode showed the simultaneous analysis gave the lowest power loss (global optimal) and faster results compared to other combined methods. All the analyses for optimizing the DG as well as reconfiguration are used the Artificial Bee Colony Optimization technique.
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Feedforward of Grid Line-to-Line Voltages for Grid-Connected Inverter under the Weak Grid Condition
Alireza Shayestehfard,Hamza Belkamel,Saad Mekhilef,Hazlie Bin Mokhlis,Mutsuo Nakaoka,Koki Ogura 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Feedforward control is reliable for rejecting fast and dynamic voltage disturbances in the grid. Mainly this scheme is implemented based on phase voltages of the wye connected configuration. Under unbalanced and distorted grid-condition, the online conversion of line-to-line values into the phase values is unworkable. In order to exploit full advantages of feedforward controller, an appropriate modulator is needed. In this paper the feedforward of grid line-to-line voltages is used in lieu of phase voltages. The introduced feedforward method is implemented with implicit zero-sequence discontinuous pulse width modulation (IZDPWM) technique that is compatible for grid-connected inverters. Regardless the grid topology, IZDPWM exactly copies the distorting harmonics of the grid voltage. Hence, a sinusoidal current is injected to the grid. Moreover, for measuring the grid line-to-line voltages two sensors are required; hence overall system cost is reduced and control system reliability is increased.
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