Papers by Behrooz Mirafzal
Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting, 2006
Abstract The main objective of this paper is to develop and experimentally verify a method of ide... more Abstract The main objective of this paper is to develop and experimentally verify a method of identifying the faulty phase in a three-phase armature of an induction motor with concentric coil construction, when such an armature suffers from an inter-turn within one of its phases ...
2011 Twenty-Sixth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2011
ABSTRACT A fault-tolerant technique valid for both open- loop and vector-control motor-drive syst... more ABSTRACT A fault-tolerant technique valid for both open- loop and vector-control motor-drive systems is introduced in this paper. The technique is merely presented for AC motors with Delta-connected circuits in their stator windings. Hence, it enables the operation of the three phase motor upon a failure in one of its phases without the need of a special fault detection algorithm. This technique is to significantly mitigate torque pulsations, which are caused by an open-Delta configuration in the stator windings. The performance of the fault-tolerant technique was experimentally verified using a 5-hp 460V induction motor-drive system and the results are presented in this paper.
IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society, 2010
... Arash Nejadpak1, Student member, IEEE, Behrooz Mirafzal1, Senior Member, IEEE, Osama Mohammed... more ... Arash Nejadpak1, Student member, IEEE, Behrooz Mirafzal1, Senior Member, IEEE, Osama Mohammed1, Fellow, IEEE and Lixiang Wei2, Member IEEE 1Energy Systems Research Laboratory, ECE ... For sake of simplicity, the simulation of the IGBT module shown in Fig. ...
2016 IEEE Energy Conversion Congress and Exposition (ECCE), 2016
Regulations for grid-tied inverters, outlined in IEEE 1547, allow distributed energy resources to... more Regulations for grid-tied inverters, outlined in IEEE 1547, allow distributed energy resources to control the reactive power injected into or absorbed from the grid. The operational region of a grid-tied inverter has asymmetry around the PQ plane in terms of apparent power limitations and harmonics injected into the grid. This asymmetrical behavior, caused by the filter used to interface the inverter with the grid, must be considered in order to meet strict grid standards, e.g. IEEE 519 and 1547, for all desired operating points of a grid-tied inverter. The objective of this paper is to identify operational points available for grid-tied inverters and to explain how some operational points must be avoided due to undesirable characteristics, e.g. poor quality of the injected current waveform. This work (i) enables filter networks for distributed sources to be designed to meet grid requirements even under worst case operating conditions, (ii) provides distribution engineers with information regarding the feasible active and reactive power which can be generated by grid-tied inverters, and (iii) provides a basis for assessing operating point trajectories when altering the steady-state operation of grid-tied inverters. Simulation and experimental data are presented to verify the findings of this work.
The Journal of Engineering, 2018
Here, a new topology for direct drive wind turbines (DDWTs) with a new power electronics interfac... more Here, a new topology for direct drive wind turbines (DDWTs) with a new power electronics interface and a low-voltage generator is presented. In the presented power electronics interface, the grid-side converter is replaced by a boost current source inverter (CSI) which eliminates the required dc-bus capacitors, resulting in an increase in the system lifetime. The inherently required dc-link inductor for this topology is eliminated by utilising the synchronous inductance of the permanent magnet synchronous generator. The control technique used for the developed DDWT is described here. The boost CSI enables conversion of a low dc voltage to a higher line-to-line voltage creating an indirect boost matrix converter, and thus, enabling the implementation of a low-voltage generator. This further enables a reduction in the number poles required in direct drive wind generators. The feasibility of the proposed generator-converter topology for DDWTs and its controllers are verified through simulations and experimental results on a laboratory scale 1.5 kW, 240 V setup .
2016 IEEE Energy Conversion Congress and Exposition (ECCE), 2016
In this paper, a new generator-converter system for direct drive wind turbines in order to decrea... more In this paper, a new generator-converter system for direct drive wind turbines in order to decrease the capital cost and improve the system reliability is presented. The grid-side Voltage Source Inverter (VSI) is replaced by a single-stage boost inverter. This provides flexibility to design a low-voltage generator and thus decreasing the number poles required in the generator. A 1.5MW generator for the proposed system is designed using Finite Element (FE) computations. This design is compared with an existing 1.5MW permanent magnet generator for direct drive wind turbine. The proposed system is supported with set of finite element computations and MATLAB/Simulink simulations.
IEEE Transactions on Power Systems, 2016
As the number of renewable energy generation units and, consequently, solid-state based converter... more As the number of renewable energy generation units and, consequently, solid-state based converters increases in the power grid, many power electronics concepts should be integrated into power system analysis and design. Thus, a power laboratory course with emphasis on the nexus between power electronics and power system is desired. However, the flexibility of instructors in designing a wide range of educational experiments is limited by the use of specialized educational setups. This problem can be resolved by allowing students to assemble their setups using laboratory scaled-down devices; however, implementation times can limit students to focus on the main concepts of the experiments. In particular, lacking experience with hardware description languages to develop switching patterns and control schemes for solid-state based converters further increases the implementation times. In this paper, a technique for rapidly implementing switching patterns and control schemes for power converters is proposed. This technique provides an easy-to-use laboratory allowing students to focus on reinforcing the theory learned in energy conversion, motor-drive, power electronics, and power system classes while still providing instructors with the flexibility to design a wide range of educational experiments. Index Terms-FPGA applications in power laboratory, power engineering education, solid-state based power converters.
2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014, 2014
ABSTRACT Three-phase single-stage boost inverter requires narrow pulses, thus a low resolution DS... more ABSTRACT Three-phase single-stage boost inverter requires narrow pulses, thus a low resolution DSP can cause some pulse droppings which results in asymmetries in the output waveforms of the boost inverter. This leads to an increase in the total harmonic distortion (THD) of the output waveforms. In order to solve this problem, a modified version of the phasor pulse width modulation (PPWM) switching pattern is developed based on constant charging time over each sector and staircase pattern for the discharging times variation. Also, the boost inverter needs a relatively large dc-link inductor to boost and convert a small dc voltage to a nominal ac voltage. Due to the existence of the dc-link inductor, large voltage spikes appear across inverter switches. Thus, in the modified PPWM method an overlap-time is implemented in order to suppress the voltage spikes. A 2kW 208/230V laboratory-scale three-phase boost inverter has been designed, built and tested using reverse-blocking IGBTs. The behavior of the boost inverter along with the modified PPWM switching pattern and the overlap-time has been investigated, and the results are presented in this paper.
IEEE Transactions on Industry Applications, 2009
A failure mode for PWM inverter-fed AC motors due to the anti-resonance phenomenon is introduced ... more A failure mode for PWM inverter-fed AC motors due to the anti-resonance phenomenon is introduced and investigated in this paper. At high frequencies, an AC motor behaves as a series RLC circuit with a resonance point, so-called anti- resonance, typically above 1.0 MHz. If the voltage oscillation frequency, caused by the reflected wave phenomenon matches the motor anti-resonance frequency, an amplified voltage will appear internally between the turns of the stator windings. This externally unobservable state causes winding insulation failure in the AC motor. This phenomenon is experimentally verified using a rewound Permanent Magnet (PM) motor with accessible taps along the stator windings, and the results are presented in this paper.
IEEE Transactions on Industry Applications, 2009
AbstractA systematic procedure to determine the parame-ters of a previously proposed low-to high... more AbstractA systematic procedure to determine the parame-ters of a previously proposed low-to high-frequency induction motor model is presented. An analysis of the high-frequency behavior with regard to the impact of magnetic core selection, parasitic interturn and ...
IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society, 2010
The concept of regenerative energy management for pulse-loads in dual DC-AC micro-grids is invest... more The concept of regenerative energy management for pulse-loads in dual DC-AC micro-grids is investigated in this paper. Although this study is presented herein for electric ship power systems, the findings can also be applied for dual DC-AC micro-grids with flywheel (FW) energy storage systems. The mitigation of pulse-load effects is achieved via both the proposed system configuration and time-coordination between the occurrence of pulse-loads and kinetic energy-releases. In this paper, it is demonstrated that the kinetic energies of FW and prime-movers in an electric ship can be used to regulate the voltage of a DC distribution system in the presence of pulse-loads. This improves the stability of the overall system. The findings of this investigation are experimentally verified using a laboratory-scale micro-grid, and the test results are presented in this paper.
2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2012
In this paper, the dynamic model of a three-phase boost inverter is developed in dq-frame of refe... more In this paper, the dynamic model of a three-phase boost inverter is developed in dq-frame of reference. The boost inverter utilizes the current source topology and applies a modified space-vector pulse-width-modulation (SVPWM) switching technique, here called phasor pulse-width-modulation (PPWM). In the presented modeling approach, the state-space equations of the system are derived in dq-frame of reference and averaged over a
IEEE Transactions on Power Electronics, 2011
In many modern energy conversion systems, a dc voltage, which is provided from a sustainable ener... more In many modern energy conversion systems, a dc voltage, which is provided from a sustainable energy source or energy storage device, must be boosted and converted to an ac voltage with a fixed amplitude and frequency. In this paper, a switching pattern based on the concept of the conventional spacevector pulsewidth-modulated (SVPWM) technique is developed for single-stage, three-phase boost-inverters using the topology of current-source inverters. The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three-charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the dc input voltage. The developed switching pattern was experimentally verified through a laboratory-scaled threephase 500-W boost inverter and the results are presented in this paper. Index Terms-Grid-connected and stand-alone sustainable energy (SE) systems, microgrid, modified space-vector pulsewidthmodulated (SVPWM) technique, single-stage boost inverter, threephase current-source inverter (CSI) topology.
Smart solar powered charge stations (SSPCS) and smart microgrids that control power flow to elect... more Smart solar powered charge stations (SSPCS) and smart microgrids that control power flow to electric vehicles at work sites, shopping malls, restaurants, schools, parks, etc. will become important as the number of electric vehicles (EVs) increases. Progress on the development of SSPCS will be presented. This will include the rationale for SSPCS and a triple bottom line analysis of SSPCS. Wide adoption of SSPCS will enhance and support the electrification of transportation and market penetration of EVs. Business models that ...
This paper presents a second order model for stability analysis of grid-connected voltage source ... more This paper presents a second order model for stability analysis of grid-connected voltage source inverters (VSIs). VSIs are commonly modeled as ideal voltage sources for analysis. However, this approach cannot guarantee accuracy since it does not take into consideration the dominant states of the inverter. In this paper, a reduced-order model based on balanced truncation method is derived from a comprehensive twelfth-order model for a grid-connected VSI. The developed second-order model is computationally modest while providing an accurate representation of the system characteristic. The efficacy of the developed model is verified through time-domain simulations and root locus studies of the model eigenvalues against its full-order counterpart.
In this paper, a virtual inductance control scheme is proposed to improve the stability of voltag... more In this paper, a virtual inductance control scheme is proposed to improve the stability of voltage source inverters (VSIs) in weak grids. The large grid impedance in weak grids can make grid-tied VSIs unstable. To keep VSIs stable in weak grids, control and circuit parameters can be designed to expand the stable operating region of VSIs. In this paper, a closed-loop state-space model is developed for PQ-controlled VSIs with the virtual inductance term in the controller. Using the root locus analysis, impacts of the LCL filter inductance, as well as the virtual inductance feedforward controller on the stability of VSIs are studied. The performance of the virtual inductance is then verified for both symmetrical and asymmetrical grid impedance setups through hardware tests carried out on a three-phase grid-tied VSI in the laboratory.
arXiv (Cornell University), Dec 26, 2022
This article studies the possibility of controlling the surge impedance of the electric motor in ... more This article studies the possibility of controlling the surge impedance of the electric motor in motor drives. The existing solution to suppress (or eliminate) the reflected wave impact on the motor insulation run by a Si-IGBT or SiC-MOSFET-based drive is to use either a sinewave filter or / filter. The alternative solution suggested in this article is to implement a high-bandwidth electronic circuit at the end of the cable or at the motor terminals to match the surge impedance of the cable and motor. The highfrequency voltage ringing due to the reflected waves in motor drives is around , depending on the cable parameters and the length of the cable. In the proposed method, the electronic circuit can quickly detect the / rise and fall edges and adjust the electronic circuit equivalent impedance when pulses arrive the motor terminals. Thus, the cable and motor surge impedances can be matched over a short time to prevent reflected waves. As a result, the leakage currents passing through the ball bearing and overvoltage stress on the motor insulation can be suppressed significantly.
2023 IEEE Applied Power Electronics Conference and Exposition (APEC)
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Papers by Behrooz Mirafzal