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power Electronic and Drive systems and Technologies Conference (PEDSTC)

作者： Mahmoud Shahbazi Mohammad Reza Zolghadri Saeed Ouni Center of Excellence in Power System Management & Control (CEPSMC) Sharif University of Technology Tehran Iran

Interleaved DC-DC boost converters are interesting choices in applications like fuel cells and photovoltaic systems. Although this converter offers low current ripple, but an open-circuit switch fault can lead to unacceptable current ripples. In this paper, a very fast and simple method is proposed to detect an open-circuit switch fault and its location. This method doesn't need any additional sensors, is efficient in CCM and DCM modes of operation, and can detect the fault in less than one switching period. Moreover, this method is suitable for implementation on an FPGA, due to the use of simple math and state machine blocks. Simulations are carried out to validate the effectiveness of this method.

关键词： Switches Fault detection Inductors Estimation DC-DC power converters Current measurement Sensors

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Bad data injection as a threat for power system security

Bad data injection as a threat for power system security

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2015 Smart Grid Conference, SGC 2015

作者： Farajollahi, M. Hosseini, S.H. Fotuhi-Firuzabad, M. Safdarian, A. Electrical Engineering Department Sharif University of Technology Center of Excellence in Power System Control and Management Iran

ISBN: (纸本)9781509003693

power system operation is undeniably affected by system security indications providing system operators with insight into power system status. In this regard, any tampered data would compromise power system security. This paper aims at presenting an approach to scrutinize the impact of cyber attacks on the system security indices. With this in mind, two well-known system security indices representing voltage and loading severities are taken into account. The approach uses genetic algorithm to find the most severe conditions for each security index from financial and technical viewpoints. In the former, bad data injection targets to overestimate security indices resulting in unnecessary preventive actions, thus higher operation costs. In the latter, however, underestimation of security indices may threat system security. The proposed algorithm is applied to the standard IEEE 30-bus system. The obtained results indicate how cyber attacks could manipulate the system security indices, leading to fallacious insight over power system status. © 2015 IEEE.

关键词： Genetic algorithms

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Optimal transmission switching as a remedial action to enhance composite system reliability

Optimal transmission switching as a remedial action to enhan...

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2015 Smart Grid Conference, SGC 2015

作者： Khorram, Seyed Abbas Tabatabaei Fard, Ali Abbaspour Tehrani Fotuhi-Firuzabad, Mahmud Safdarian, Amir Department of Electrical Engineering Center of Excellence in Power System Management and Control Sharif University of Technology Tehran Iran

ISBN: (纸本)9781509003693

Increasing redundant paths in transmission grids has always been thought to be a tool to enhance service reliability. However, network equations by intertwining power flows through redundant paths impose more limits on systems with more redundancy. Accordingly, autonomous removing of a few lines may relief capacity limit violations in some contingency events thereby enhancing service reliability. This paper aims to study impacts of manual removing of transmission lines on composite system reliability. For doing so, the existing model is extended to consider optimal transmission switching (OTS) as a remedial action. The model minimizes total damage cost imposed by load curtailments. The extended model is formulated in mixed integer linear programming (MILP) format that can be easily solved via commercial solvers. The model is applied to likely contingencies wherein violations in capacity limits are encountered. Then, the results along with occurrence probability of the contingencies are taken into use to calculate load point and system oriented reliability indices. Simulation results on the modified reliability test system (MRTS) demonstrate great enhancements in service reliability when OTS is realized. © 2015 IEEE.

关键词： Integer programming

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Introduction of dimensioned approach to evaluation of distribution transformer short circuit forces 23

Introduction of dimensioned approach to evaluation of distri...

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23rd Iranian Conference on Electrical Engineering, ICEE 2015

作者： Moradnouri, Ahmad Vakilian, Mehdi Elhaminia, Pedram Bahrami, Mansour Electrical Engineering Department Center of Excellence in Power System Management and Control Sharif University of Technology Tehran Iran

ISBN: (纸本)9781479919727

in this paper the radial and axial forces developed under windings short circuit conditions in two different designs of a 630 kYA distribution transformer (using analytic a^id finite element method) are determined and compared. The simulation results using FEM software verify the results of the employed analytic method. These results show that although the transformer with larger dimensions have a better operating performance and lower total owning cost with respect to one with smaller sizes (assuming the same mechanical strength for winding and support structures of both), the risk of failure due to its related short circuit forces elevates in the former. Additionally, this paper presents some analytical expressions which demonstrate the relationships between short circuit forces and transformer geometrical parameters. These relationships help transformer designers to choose the best dimensional parameters to improve the transformer performance in such a way that risk of failure of transformer due to short circuit forces doesn't increase 01 increase in a lower paste if compared with the other sample. © 2015 IEEE.

关键词： Finite element method

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Fast detection of open-switch fault in cascaded H-Bridge multilevel converter

Fast detection of open-switch fault in cascaded H-Bridge mul...

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power Electronic and Drive systems and Technologies Conference (PEDSTC)

作者： Mahmoud Shahbazi MohammadReza Zolghadri Center of Excellence in Power System Management & Control (CEPSMC) Sharif University of Technology Tehran Iran

ISBN: (纸本)9781479976546

Cascaded H-Bridge converter has recently been utilized in different high-power applications due to its modular and simple structure. In order to have a balanced operation after a fault occurrence in this converter, it is necessary to detect the switch fault and its location. In this paper, a fast power switch fault detection method is presented to identify the fault and its location. Only one voltage measurement per phase is required by this method, and the fault detection is faster compared to the existing methods. Moreover, it is easy for implementation on an FPGA device, due to the use of simple math, relational and state machine blocks. The proposed method is verified by computer simulations.

关键词： Switches Field programmable gate arrays Computers Computational modeling Ice

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Impact of erroneous measurements on power system real-time security analysis

Impact of erroneous measurements on power system real-time s...

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Iranian Conference on Electrical Engineering (ICEE)

作者： Mohammad Farajollahi Mahmud Fotuhi-Firuzabad Amir Safdarian Electrical Engineering Department Sharif University of Technology Center of Excellence in Power System Control and Management Tehran Iran

power system security analyses as well as decisions made to preserve system security are all on the basis of an approximate insight over the system status. This approximate insight is provided based on erroneous measurements throughout the system. The error in the input data may result in a misleading index which either increases system operating costs or jeopardizes service continuity. This paper aims at establishing an step-by-step algorithm to study impacts of error in measurements on system security indices. Two different security indices representing under voltage severity and over load severity are studied in this paper. The proposed algorithm has three major steps. In the first step, typical measurements are sampled according to the system operating state and randomly generated errors. This is done using Monte Carlo sampling approach. The second step is to extract an approximate model of the system true state which is done via state estimators. Then, security indices are calculated for both the approximated and true states in the third step. Comparison between the indices demonstrates impacts of the erroneous measurements on security assessment.

关键词： Decision support systems Electrical engineering Conferences

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Changing Electrical Safety

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IEEE INDUSTRY APPLICATIONS MAGAZINE 2014年第5期20卷 6-6页

作者： Capelli-Schellpfeffer, Mary Center of Excellence in Power System Management & Control Sharif University of Technology Tehran Iran

n this year’s “Electrical Safety” columns, we have been exploring the topic of changing electrical safety, with thoughtleaders offering their perspectives. Our guest contributors have had truly prestigious careers dedicated to advancing the well-being of those who work in and benefit from the power economy. Reflects on the remarks and observations made.

关键词： Electrical safety power systems reliability power system safety

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An adaptive droop control method for low voltage DC microgrids

An adaptive droop control method for low voltage DC microgri...

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power Electronic and Drive systems and Technologies Conference (PEDSTC)

作者： A. Khorsandi M. Ashourloo H. Mokhtari The Center of Excellence in Power System Management & Control Sharif University of Technology Tehran Iran

DC microgrids (MGs) are becoming popular as effective means to integrate different energy resources. Conventionally, the droop control is adopted as a decentralized control method for power sharing in DC MGs. However, current sharing accuracy or voltage regulation deteriorates due to the effects of line impedances. In this paper, a new adaptive control strategy is proposed for DC MGs. In low load conditions, the output currents of the DGs are far from their maximum acceptable limits. Therefore, current sharing accuracy is not important. As load increases, the output currents of the DGs approach their maximum acceptable limits. Therefore, at high load conditions, accurate current sharing is necessary. In the proposed method, with increasing the load, the equivalent droop gains are automatically increased to attain more accurate current sharing. Simulation results are provided to verify the validity and effectiveness of the proposed method.

关键词： Microgrids Distributed power generation Reliability Accuracy

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A new power management control strategy for a MV microgrid with both synchronous generator and inverter-interfaced distributed energy resources

A new power management control strategy for a MV microgrid w...

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IEEE International Symposium on Industrial Electronics (ISIE)

作者： Mohsen Zangeneh Mohsen Hamzeh Hossein Mokhtari Houshang Karimi The Center of Excellence in Power System Management & Control Sharif University of Technology Tehran Iran

control strategies of a microgrid which includes both synchronous generators and converter-based distribution generation (DG) units must be designed such that effective operation of the microgrid is achieved. The main objective of this paper is to develop a high performance control strategy for an islanded medium voltage (MV) microgrid consisting of inverter and non-inverter interfaced DG units. A new control method for the synchronous generator in an islanded microgrid is proposed based on a virtual droop scheme. The proposed strategy can effectively manage the real and reactive powers of the microgrid among the inverter and non-inverter based DG units. The steady state and dynamic responses of the MV microgrid is significantly improved by using the proposed power management scheme. The performance of the proposed control strategy is verified by using digital time-domain simulation study in the PSCAD/EMTDC software environment.

关键词： Microgrids Voltage control Synchronous generators Reactive power Steady-state Frequency control control systems

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Design and implementation of a single phase grid-connected PV inverter with a new active damping strategy

Design and implementation of a single phase grid-connected P...

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power Electronic and Drive systems and Technologies Conference (PEDSTC)

作者： M. Hamzeh Y. Karimi E. Asadi H. Oraee The Center of Excellence in Power System Management & Control Sharif University of Technology Tehran Iran

This paper presents an effective current injection method for a single phase grid-connected PV inverter with LCL filter. The main objective of the proposed control strategy is to compensate the resonance effect of the LCL filter. In the proposed control strategy, a resonance compensator is augmented to the conventional proportional resonance (PR) controller to attenuate current oscillations in resonance frequency of LCL filter. The proposed strategy robustly regulates the output current of grid connected inverter in various grid impedances and provides a high quality current injection capability for the PV inverter in harmonic polluted condition of the grid voltage. The performance of the proposed control scheme is verified by using digital time-domain simulation in MATLAB Simulink environment. Moreover, the proposed scheme has been tested experimentally in the laboratory.

关键词： MATLAB Voltage control Frequency control Resonant frequency Arrays Inverters Time-frequency analysis

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