Search for: unbalance-load
0.005 seconds

    Control of an Islanded Multi-DG Microgrid under Unbalanced and Nonlinear Loads Conditions

    , Ph.D. Dissertation Sharif University of Technology Hamzeh, Mohsen (Author) ; Mokhtari, Hossein (Supervisor) ; Karimi, Houshang (Co-Advisor)
    Nowadays, the use of distributed generation (DG) units and microgrid systems is mainly limited to their operation in the grid-connected mode. In the grid-connected mode, a microgrid including its loads and DG units is connected to the main grid at the point of common coupling (PCC). In this case, the main grid provides fixed voltage and frequency for the microgird and each DG unit regulates its power components based on the conventional dq-current control strategy. Autonomous (islanded) operation of a microgrid, however, is not as straightforward as its operation in the grid-connected mode, i.e., control and power management of an islanded microgrid is very difficult due to the stochastic... 

    Evaluate and Compare the Performance of Steel Zipper Frames under Far and near Faults Earthquake

    , M.Sc. Thesis Sharif University of Technology Torkamaneh Parneshani, Ehsan (Author) ; Mofid, Masoud (Supervisor)
    Zipper frames were proposed to provide a solution of prevention of forming soft Story due to the existence of unbalanced vertical load in Chevron frames. In this study, at first, by performing a nonlinear pushover analysis on the 2D zipper frames with 3, 7 and 12 story and 3 span that the middle one are braced, a Response modification factor for zipper frames is proposed. Then, The seismic behavior of zipper frames is evaluated under far and near-fault earthquakes by nonlinear time history analysis and at the end of the research, the cyclic behavior and energy absorption capacity of these frames are compared with the 2-story-X chevron frames with 3 and 7 story. It is concluded that the... 

    Study of Current Unbalance Propagation Pattern and HV Systems Share of Downstream Networks

    , M.Sc. Thesis Sharif University of Technology Mehrabian, Mohammad Amin (Author) ; Mokhtari, Hossein (Supervisor)
    Electrical systems are prone to voltage or current unbalance due to unbalance loads or asymmetries in network elements such as untransposed lines. Voltage and current unbalance can cause malfunction or reduction in lifetime of different elements. Voltage unbalance has been studied in a variety of publications, due to its high importance and significant effects. However, current unbalance has not gained much attention despite its undeniable influence on transformers’ and line’s lifetime. Observing high values of current unbalance in LV systems is predictable and inevitable. On the other hand, HV systems must be much more balance due to their different structure and absence of large unbalance... 

    Control of a microgrid with unbalanced loads using virtual negative-sequence impedance loop

    , Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , p. 78-83 Hamzeh, M ; Karimi, H ; Mokhtari, H ; Mahseredjian, J ; Sharif University of Technology
    This paper presents an effective control strategy for autonomous operation of a multi-bus medium voltage (MV) microgrid (MG) consisting of several dispatchable distributed generation (DG) units. Each electronically-coupled DG unit supplies the loads which can be unbalanced due to the inclusion of single-phase loads. The proportional resonance (PR) and droop controllers are, respectively, used to regulate the load voltage and share the average powers among the DG units. The virtual negative-sequence impedance controller (VNSIC) is proposed to effectively compensate the negative-sequence currents of the unbalanced loads. Moreover, the VNSIC minimizes the negative-sequence currents in the MV... 

    A new decentralized voltage control scheme of an autonomous microgrid under unbalanced and nonlinear load conditions

    , Article Proceedings of the IEEE International Conference on Industrial Technology ; February , 2013 , Pages 1812-1817 ; 9781467345699 (ISBN) Paridari, K ; Hamzeh, M ; Emamian, S ; Karimi, H ; Bakhshai, A ; Sharif University of Technology
    This paper presents an effective voltage control strategy for the autonomous operation of a medium voltage (MV) microgrid under nonlinear and unbalanced load conditions. The main objectives of this strategy are to effectively compensate the harmonic and negative-sequence currents of nonlinear and unbalanced loads using distributed generation (DG) units. The proposed control strategy consists of a multi-proportional resonant controller (MPRC) whose parameters are assigned with particle swarm optimization (PSO) algorithm. The optimization function is defined to minimize the tracking error at the specific harmonics considering the stability limitations. In this paper the performance of the... 

    Power Flow Control and Power Quality Enhancement in Grid-Connected Microgrid with Back-to-Back Converter

    , M.Sc. Thesis Sharif University of Technology Sekhavatmanesh, Hossein (Author) ; Mokhtari, Hossein (Supervisor)
    A microgrid system consists of some distributed generators (DGs) and local loads which can operate in both grid-connected and islanded modes of operation. An islanded mode of operation is required when the grid voltage deteriorates and its power quality drops. This islanding operation can be attained by opening grid-side switches or by using back-to-back (b-to-b) converters. Due to the increase of highly sensitive loads and to have better power control and higher power quality, the use of back-to-back converters has recently attracted interests among researchers. However, the major drawback of this solution is the cost of a b-to-b converter. Therefore the aim of this project is to gain some... 

    A new control strategy for a multi-bus MV microgrid under unbalanced conditions

    , Article IEEE Transactions on Power Systems ; Volume 27, Issue 4 , 2012 , Pages 2225-2232 ; 08858950 (ISSN) Hamzeh, M ; Karimi, H ; Mokhtari, H ; Sharif University of Technology
    This paper proposes a new control strategy for the islanded operation of a multi-bus medium voltage (MV) microgrid. The microgrid consists of several dispatchable electronically-coupled distributed generation (DG) units. Each DG unit supplies a local load which can be unbalanced due to the inclusion of single-phase loads. The proposed control strategy of each DG comprises a proportional resonance (PR) controller with an adjustable resonance frequency, a droop control strategy, and a negative-sequence impedance controller (NSIC). The PR and droop controllers are, respectively, used to regulate the load voltage and share the average power components among the DG units. The NSIC is used to...