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Study of HVDC Transmission for Offshore Wind Farms Based on Voltage Source Converters
, M.Sc. Thesis Sharif University of Technology ; Parniani, Mostafa (Supervisor)
Abstract
In this thesis, DC transmission of offshore wind farms is studied thoroughly. Various system configurations that are introduced in the literatures are discussed and their control scheme for normal conditions and grid faults are studied. Then, the HVDC transmission based on voltage source converter, located between a local offshore ac grid and the onshore ac system is investigated as the most practical choice. The HVDC linke circuit elements are calculated and the control strategies of the offshore and onshore converters are introduced. DFIGs are considered to be the best choice for the offshore wind turbine generators. Then, the system is simulated and the frequency of the offshore grid is...
Stabilization of Subsynchronous Oscillations of ILAM Refinery Gas Turbine Units in Islanded Operations
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Ilam refinery has three synchronous generator units each with a capacity of 26.5 MVA and two six-phase LCI-fed synchronous compressors, each with a capacity of 8 MW. Generators of Ilam gas refinery have instability issue in case of island operation. With launching one generator unit and then connecting two compressors the instability problem and tripping of the generators appear. Given the importance of this issue, various tests and corresponding measurements in both electrical and mechanical aspects were carried out at the plant in on-grid and island operations to analyze the cause of instability phenomena. The mechanical part of tests analyses the frequency of oscillations and vibration in...
Down-conversion self-oscillating mixer by using CMOS technology
, Article Proceedings - 2012 IEEE 8th International Colloquium on Signal Processing and Its Applications, CSPA 2012 ; 2012 , Pages 33-36 ; 9781467309615 (ISBN) ; Zahedi, A ; Sabaghi, M ; Ameri, S. R. H ; Niyakan, M ; Sharif University of Technology
2012
Abstract
In this paper a self-oscillating mixer is presented fundamental signal generated by the oscillator subcircuit in the mixing process. The oscillator core consumes 3mA of current from a 1.8 V DC supply and results in an output power of -0.867 dBm per oscillator, and a measured phase noise of -91, -102 and -108 dBc/Hz at 100 KHz, 600 KHz and 1 MHz from the carrier, respectively. In the mixing process the proposed mixer achieved IIP3 of 0 dBm with conversation gain of 1.93 dB. The circuit was designed and simulated in 0.18-μm CMOS technology by ADS2010
Optimizing the normalized dead-time and maximum switching frequency of a wide-adjustable-range LLC resonant converter
, Article IEEE Transactions on Power Electronics ; Volume 26, Issue 2 , August , 2011 , Pages 462-472 ; 08858993 (ISSN) ; Rashidian, B ; Zolghadri, M. R ; Alavi, S. M. H ; Sharif University of Technology
2011
Abstract
LLC resonant converter has been widely used in dcdc converters. In this paper, optimum dead-time and maximum switching frequency of a wide-adjustable-range LLC resonant converter are investigated for realizing the zero voltage switching (ZVS) operation even under the worst-case conditions. Analyses demonstrate that these parameters depend on the converter inductance ratio and ratio of the converter resonant capacitor and the effective capacitance appeared in parallel with the drainsources of the power MOSFETs. The necessary dead time for realizing the ZVS operation can be minimized by choosing the normalized maximum switching frequency, properly. Using the dead-time optimum value, soft...
Using LLC resonant converter for designing wide-range voltage source
, Article IEEE Transactions on Industrial Electronics ; Volume 58, Issue 5 , 2011 , Pages 1746-1756 ; 02780046 (ISSN) ; Rashidian, B ; Zolghadri, M. R ; Alavi, S. M. H ; Sharif University of Technology
Abstract
LLC resonant converter with significant resonant inductance is proposed for designing an adjustable wide-range regulated voltage source. Large resonant inductance increases output voltage adjustment range and conversion efficiency, particularly at light loads. Soft switching is achieved for all power devices under all operating conditions by choosing the dead time and maximum switching frequency properly and operating in the converter's inductive region. Using a power-factor-correction (PFC) converter reduces the resonant converter's output voltage dependence to the variations of the main ac input voltage. Thus, the compensation of the load variations and the wide-range adjustment of the...
Design, simulation, and implementation of an Electric Hybrid Motorcycle
, Article Proceedings of the ASME Design Engineering Technical Conference, 15 August 2010 through 18 August 2010 ; Volume 4 , August , 2010 , Pages 163-171 ; 9780791844120 (ISBN) ; Seyed Mohammadi, S. H ; Yousefi Koma, A ; Habibidoost, M ; Aghnoot, R ; Karimi, B ; Pourhosseini, S. M ; Jalali, H ; Sharif University of Technology
2010
Abstract
This paper presents a general integrated procedure of fabricating a Hybrid Electric Motorcycle (HEM). Firstly, a simple model designed and simulated using ADVISOR2002 and the proposed model is exported to MATLAB/SIMULINK. Secondly, the controller schematic and its optimized control strategy are described. In addition, the ratings of the components including the batteries, electric motor, and internal combustion engine (ICE) are calculated based on the design. A 125 cc ICE motorcycle is selected for conversion to HEM. A brushless DC (BLDC) motor assembled in front wheel as accessory propellant. The nominal powers are 8.2 kW at 8500 rpm and 500 W for the ICE and BLDC respectively. The original...
Post-Fault Control of Fault-Tolerant Multi Module Converters
, M.Sc. Thesis Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
Nowadays, multilevel converters are significantly developed in industrial applications as well as energy transmission systems regarding proper quality of output waveforms and fault tolerant operation ability. Among the different topologies of multilevel converters, modular multilevel converter (MMC) due to its modularity feature it more accepted in high voltage direct current (HVDC) transmission systems. Fast fault detection in power electronics converters is necessary to bypass the defected part in order to prevent failure propagation to other Submodules and to provide continues servicing. On this basis, different researches are reported in literature for MMCs fault tolerant operation. In...
A lifetime improved single phase grid connected photovoltaic inverter
, Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 234-238 ; 9781467301114 (ISBN) ; Tahami, F ; Sharif University of Technology
2012
Abstract
In this paper, a reliable low power single phase grid-connected inverter for photovoltaic modules is proposed. The inverter has improved lifetime since large electrolytic capacitor is replaced with small film capacitor due to circuit topology, power processing and proper control scheme. Thus the main limiting component in single phase grid connected inverters is obviated. The proposed inverter consists of two power processing stages. First a dual active bridge (DAB) converter boosts the voltage of PV panel to approximately 440 V and eliminates impact of high dc bus voltage ripples. A proper feed forward control is proposed to regulate the dc bus voltage with high ripple. Simulation results...
A design procedure for optimizing the LLC resonant converter as a wide output range voltage source
, Article IEEE Transactions on Power Electronics ; Volume 27, Issue 8 , 2012 , Pages 3749-3763 ; 08858993 (ISSN) ; Rashidian, B ; Zolghadri, M. R ; Alavi, S. M. H ; Sharif University of Technology
2012
Abstract
LLC resonant converter is one of the most suitable circuit topologies that have been introduced for designing constant output voltage switched-mode power supplies. In this paper, a design procedure is introduced for using this converter as a wide output range voltage source. Unlike constant output voltage applications which need small converter inductance ratio and narrow switching frequency variations, for wide output range applications, large values of these parameters are needed simultaneously and should be optimized. Instead of minimizing the components stresses, leading to a great value of the inductance ratio, proper choice of the converter parameters resulting in a smaller inductance...
Input-output linearisation of a fourth-order input-affine system describing the evolution of a three-phase/switch/level (Vienna) rectifier
, Article IET Power Electronics ; Volume 4, Issue 8 , 2011 , Pages 867-883 ; 17554535 (ISSN) ; Feyzi, M. R ; Akbari Hamed, K ; Sadati, N ; Yasaei, Y ; Ouni, S ; Sharif University of Technology
Abstract
This study presents an analytical approach for proper selection of output functions to be regulated for the Vienna rectifier such that the resultant closed-loop systems are minimum phase. Specifically, two different adaptive control methodologies based on the input-output linearisation are developed and categorised. In the first category, three output functions are introduced and imposed to be zero by using three dynamic feedback laws. On the basis of states to be regulated, four different cases are studied and it is shown that only one of these cases results in a one-dimensional zero dynamics with an asymptotically stable equilibrium point. In the second category, two output functions are...
A 1.93 pA/√Hz transimpedance amplifier for 2.5 Gb/s optical communications
, Article Proceedings - IEEE International Symposium on Circuits and Systems ; 2011 , Pages 2889-2892 ; 02714310 (ISSN) ; 9781424494736 (ISBN) ; Medi, A ; Saniei, N ; Sharif University of Technology
Abstract
A state-of-the-art low-noise transimpedance amplifier (TIA) for 2.5 Gb/s family is presented using IBM 0.13-m CMOS technology. This TIA would be a part of a homodyne detector in a quantum key distribution (QKD) system. In this work a thorough design methodology based on a novel analytical noise optimization is presented. Also a unique method for eliminating the DC current of the input photodiodes (PDs) is proposed. The post-layout simulation results show bandwidth of 52 kHz to 1.9 GHz, average input referred noise of 1.93 pA/√Hz, and transimpedance gain of 80 db while dissipating 12 mW from a 1.5 V power supply, including the output buffer
A new control method of three-phase PMSG wind turbine connected to single-phase network through a Back-to-Back converter
, Article Asia-Pacific Power and Energy Engineering Conference, APPEEC ; 2011 ; 21574839 (ISSN) ; 9781424462551 (ISBN) ; Hojabri, H ; Mokhtari, H ; Chang, L ; Sharif University of Technology
Abstract
In this paper, a new control strategy is proposed to improve the performance of a wind generator system composed of a three-phase PMSG and a Back-to-Back three-phase to single-phase converter. With the use of the large inductance of the synchronous generator, the control method minimizes the generator torque ripple when the system supplies a single-phase load. The problem arises from the fact that the instantaneous power of a single-phase load is pulsating at the double of the system frequency. This paper tries to minimize the effect of this pulsating power on the PMSG torque without using a large capacitor on the DC link. Simulation results show the effectiveness of the proposed method. ©...
Performance improvement of steady-state and transient operation of offshore wind farm HVDC power transmission
, Article 2015 IEEE 16th Workshop on Control and Modeling for Power Electronics, COMPEL 2015, 12 July 2015 through 15 July 2015 ; July , 2015 , Page(s): 1 - 7 ; 9781467368476 (ISBN) ; Ebrahimi, S ; Parniani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Wind power generation is increasing fast as a clean renewable energy resource. Offshore wind farms are popular due to advantages such as higher and smoother wind speeds, less farm site limitations, etc. High capacitive currents and need to expensive compensations, make use of high-voltage-direct-current (HVDC) power transmission indispensable for longdistance wind farm power generations. Steady-state and transient performance improvements of HVDC systems have always been an interesting industrial and academic research area. In this paper, a novel control method is proposed to improve the steady-state operation of HVDC system. Moreover, a new fault detection scheme is proposed to improve the...
Small-signal model development for a Cúk converter while operating in DCVM for both DC and AC input voltages
, Article 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings, 12 September 2010 through 16 September 2010 ; September , 2010 , Pages 2613-2619 ; 9781424452866 (ISBN) ; Nasirian, V. R ; Ahmadian, M ; Yaghoobi, J ; Zolghadri, M. R ; Ferdowsi, M ; Sharif University of Technology
2010
Abstract
The Cúk converter operating in discontinuous capacitor voltage mode (DCVM) inherently benefits from PFC features as unity power factor can be achieved by using a constant duty cycle and switching frequency. In this paper, the switch network modeling technique is applied to the Cúk converter operating in DCVM in order to develop its small-signal model under the assumption that it is fed by a dc voltage source. Afterwards, the model is extended to derive the small-signal behavior of the converter while operating as a PFC converter. The validity of the proposed model is confirmed by both simulation and experimental results
Constant input power control of a three phase isolated buck+boost rectifier
, Article INTELEC, International Telecommunications Energy Conference (Proceedings), 6 June 2010 through 10 June 2010, Orlando, FL ; June , 2010 ; 02750473 (ISSN) ; 9781424433841 (ISBN) ; Zolghadri, M. R ; Ferdowsi, M ; Sharif University of Technology
2010
Abstract
A novel control method is proposed for single-stage three-phase isolated buck+boost rectifier. The control method is based on the conventional cascade two-loop control structure and is modified to achieve constant instantaneous input power. Input voltages, output voltage, and DC-link inductor current are measured to control the power switches to achieve output voltage regulation as well as input power factor correction. In the proposed method, input currents are controlled such that input power is constant even for unbalanced mains. Thus for balanced mains converter behaves like an ideal rectifier, and for unbalanced mains, low-frequency harmonics of the output voltage are suppressed. The...
A scalable offset-cancelled current/voltage sense amplifier
, Article ISCAS 2010 - 2010 IEEE International Symposium on Circuits and Systems: Nano-Bio Circuit Fabrics and Systems, 30 May 2010 through 2 June 2010, Paris ; 2010 , Pages 3853-3856 ; 9781424453085 (ISBN) ; SharifKhani, M ; Jahinuzzaman, S. M ; Sharif University of Technology
2010
Abstract
the application of current sense amplifiers in scaled SRAM design is limited by two factors: the DC offset due to the device mismatch and limited voltage headroom. The presented scheme reduces the effect of offset by proposing an extra phase for offset cancellation before current sensing takes place. A twofold reduction of the cell access time is achieved compared to the conventional scheme under similar cell current and bitline capacitance. The offset cancellation phase takes place in parallel to the wordline decoding time in order to speed up the current sensing. The proposed scheme requires a small power budget due to a self shut off mechanism. In addition to presenting a comparison with...
Single-phase PWM rectifier parameters optimized by using the intelligent method
, Article Proceedings - 2010 IEEE Region 8 International Conference on Computational Technologies in Electrical and Electronics Engineering, SIBIRCON-2010, 11 July 2010 through 15 July 2010, Irkutsk Listvyanka ; 2010 , Pages 677-681 ; 9781424476268 (ISBN) ; Dastfan, A ; Tahmasebi, R ; Rahideh, M ; Sharif University of Technology
Abstract
This paper is dealing with single phase PWM rectifier parameter optimization. A control loop has been designed to attain a suitable output DC voltage with minimum ripple, input current with minimum harmonic and maximum input power factor. In this paper these parameters have been optimized by using Genetic algorithm. To verify the effectiveness of proposed optimization, different simulations have been done. The simulation results prove that the proposed system working good
Efficient control scheme of wind turbines with doubly fed induction generators for low-voltage ride-through capability enhancement
, Article IET Renewable Power Generation ; Volume 4, Issue 3 , May , 2010 , Pages 242-252 ; 17521416 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
As the penetration of wind power in electrical power systems increases, it is required that wind turbines remain connected to the grid and actively contribute to the system stability during and after grid faults. This study proposes an efficient control strategy to improve the low-voltage ride-through (LVRT) capability in doubly fed induction generators (DFIGs). The proposed scheme consists of passive and active LVRT compensators. The passive compensator is based on a new crowbar arrangement located in series with stator windings. It considerably reduces the rotor inrush current at the instants of occurring and clearing the fault. The active LVRT compensator is realised through rotor voltage...
Electrokinetic behavior of asphaltene particles
, Article Fuel ; Volume 178 , 2016 , Pages 234-242 ; 00162361 (ISSN) ; Zare, E ; Ayatollahi, Sh ; M. Vargas, F ; G. Chapman, W ; Kostarelos, K ; Taghikhani, V ; Sharif University of Technology
Elsevier Ltd
Abstract
The effect of electrostatic field on the aggregation rate and aggregate size of asphaltene particles precipitated from three different crude oil samples suspended in a mixture of toluene and n-heptane (a model oil) was investigated. An electrode-embedded glass micro-model utilizing a high-voltage direct current power supply was utilized in this study. The asphaltene particle size and the rate of aggregation under the electric field were monitored using a high-resolution optical microscope and the average aggregate size for asphaltene particles was estimated using image processing software. To investigate the effects of structural parameters on asphaltene aggregation rate, aggregate size and...
On the primary resonance of an electrostatically actuated MEMS using the homotopy perturbation method
, Article Proceedings of the ASME Design Engineering Technical Conference, 30 August 2009 through 2 September 2009, San Diego, CA ; Volume 6 , 2009 , Pages 569-574 ; 9780791849033 (ISBN) ; Moghimi Zand, M ; Taghi Ahmadian, M ; Sharif University of Technology
Abstract
In this paper, primary resonance of a double-clamped microbeam has been investigated. The Microbeam is predeformed by a DC electrostatic force and then driven to vibrate by an AC harmonic electrostatic force. Effects of midplane stretching, axial loads and damping are considered in modeling. Galerkin's approximation is utilized to convert the nonlinear partial differential equation of motion to a nonlinear ordinary differential equation. Afterward, a combination of homotopy perturbation method and the method of multiple scales are utilized to find analytic solutions to the steady-state motion of the microbeam, far from pull-in. The effects of different design parameters on dynamic behavior...