Ahmadreza Tabesh

This paper proposes and demonstrates the idea of using electropermanent magnet (EPM)-based actuator in the structure of eddy current separator to recycle non-ferrous metals. It uses a coil excited by a full-bridge inverter to statically switch the direction of magnetic flux in the EPM, inducing eddy current within metal particles. This provides a pulsating magnetic actuator to repel non-ferrous metals mixed with other materials on a recycling conveyor. Conventional eddy current separators typically use a costly and bulky rotating permanent magnet drum or a static electromagnetic coil to generate the required repulsive forces. The static EPM-based separator eliminates the need for the expensive rotating drum structure. Furthermore, it reduces power losses compared to static electromagnetic coils by using narrow-band current pulses instead of continuous sinusoidal current. A quadratic approximation of the magnetic flux density is proposed to improve the accuracy of the repulsive force calculation. The paper also elaborates on a core optimization and electromagnetic heating analysis. A proof-of-concept EPM separator is developed and experimentally tested to calculate the repulsive force based on measured deviations in particle angle and distance. Comparing the test results shows an average error of less than 5%, confirming the improved accuracy of the quadratic approximation.

This article presents and demonstrates a voltage feedback-based technique to implement a power management integrated circuit (PMIC) for piezoelectric energy harvesting. It is analytically shown that the conducting time interval of a rectifying diode at the maximum power point is a fixed ratio of the vibration period. Thus, it can be used as a feedback to track the maximum power without measuring the output current/power. The technique can be tailored to various interface circuits, including full-bridge (FB), voltage doubler, and synchronized switch harvesting on an inductor. The micro-fabricated PMIC includes a FB rectifier, a digital maximum power point tracking (MPPT) controller, and a zero-current-switching (ZCS) integrated buck converter that uses two off-chip inductor and rectifying capacitor. The proposed technique enables the implementation of robust and power-efficient PMICs for MPPT of piezoelectric energy harvesters. To evaluate the performance of the technique, a PMIC using 130-nm CMOS technology is implemented and tested with a low power $( < 0.5$ mW) piezoelectric energy harvester. The results show that the PMIC effectively tracks the maximum power point at different vibration frequencies and amplitudes while the power consumption of its control circuitry is less than 0.001 mW.

This paper presents a framework for health estimation of a Li-ion battery that is conceptually formed based on dimensionless and common physical characteristics of a Li-ion battery. The proposed normalized features and framework enable the formation of a data-driven model to be trained using an available dataset and applied to estimate the state of health of another Li-ion battery. It is established based on introducing the new concepts of participation factors and normalized dimensionless features which are independent of a battery capacity and its dimensions. Effective training of a model using a conventional data-driven approach needs an enriched dataset that is not readily available, particularly in high-power and custom-made battery energy storage applications. The reason is that data generation needs time-consuming and expensive lifespan experiments using several samples of Li-ion batteries. To evaluate the performance of the proposed framework, four widely used Li-ion battery datasets with different capacities and dimensions are selected and compared with conventional z-score and min-max normalization methods. Test results show that the average error using the proposed method in the early stage of battery lifespan is 3.5% that is 10% less than the error in existing methods.

This paper presents a method to maximize power transfer efficiency (PTE) in wireless power transfer (WPT) systems with low-quality factors merely based on tuning the receiver-side components. The paper also suggests an algorithm to find the optimum components values considering the effect of input impedance of receiver-side rectifier at high-frequency (MHz) applications such as portable electronic devices. Existing methods often consider the input impedance of the full-bridge rectifier as a pure resistance at low frequencies. However, at high frequencies, the complex impedance of the rectifier should be taken into account since it impacts on the components optimum values to maximize PTE. Despite conventional maximizing PTE methods for series-series and series-parallel topologies, this paper shows that a series-parallel WPT system with low load quality factor requires adjusting the resonant capacitor in addition to resistive load. The validity of the proposed method is verified based on numerical simulations and experiment tests using a 100 mW cm-scale prototype of a resonant inductive link at 6.78 MHz with varying distance between coils. The test results show a PTE improvement up to 40% in a series-parallel WPT compared with the methods that only tune the load equivalent resistance.

This paper presents the Weighted Dynamic aggregation (WD agg) method to obtain an equivalent Wind Turbine Generator (WTG) for an induction machine-based wind farm using its dynamic model. The suggested approach obtains the equivalent d-q model of the induction generators considering the contribution of each unit in the model. The challenges in the aggregation of a large-scale wind farm are the variation of wind speeds at different zones and differences in the WTGs parameters. Compared with the existing methods such as Full aggregation (Full agg), Zone aggregation (Zone agg), and Semi aggregation (Semi agg), the suggested WD agg method provides an accurate single unit equivalent model for a large-scale wind farm while taking into account various wind speed zones and unequal WTG parameters. The proposed method is evaluated through time-domain simulation of a 4-WTG and a largescale 20-WTG Doubly-Fed Induction Generator (DFIG) wind farms and their aggregated models. These simulations cover combinations of different wind speeds and WTGs parameters. Also, a 4-WTGs fixed-speed wind farm is studied to show the generality of the proposed method. Comparing WD model with the detailed response of the wind farm verifies the accuracy of the method in both steady-state and transient behaviors.

This paper proposes and demonstrates a fault detection method to locate inter-turn short circuits (ITSCs) in the stator windings of a brushless doubly-fed induction machine (BDFIM). The detection of ITSC is important in machine health prognostics as ITSC is an early stage fault that may lead to other faults such as coil-to-coil and coil-to-ground. BDFIM consists of power and control windings in the stator that are magnetically coupled through a nested-loop rotor winding. Existing ITSC detection algorithms use rotor slot harmonics in stator current spectra as fault indicators for only conventional doubly-fed induction machines. However, these algorithms cannot be applied to BDFIM due to its different stator/rotor winding structure. The paper primarily proposes a new analytical formulation for the nested-loop rotor slot harmonics (NRSHs) as ITSC fault indicators in BDFIMs. Using NRSHs, a detection algorithm is also proposed to detect and locate ITSC in power/control windings of BDFIMs. The proposed algorithm is verified based on numerical analysis of a BDFIM using finite element method. The accuracy of the proposed fault detection algorithm is also experimentally investigated and demonstrated using a BDFIM test rig. Both numerical and experimental test results confirm effectiveness of the proposed ITSC fault detection and location algorithm.

This paper presents an analytical method for the design and power optimization of vacuum packaged piezoelectric energy harvesters. It is shown that the maximum power point of a vacuum packaged energy harvester is different from the conventional one which occurs when the electrical damping ratio equals to its mechanical counterpart. Also, it is shown that the captured power by a vacuum packaged energy harvester is highly sensitive to the vibration frequency due to very low mechanical damping ratio, e.g. up to 50% power drops corresponding to 2% deviations in the frequency. The analysis and design is performed in the context of an ac-line magnetic field energy harvester in which the line frequency is also fixed and this energy harvester is useful for developing the self-powered wireless monitoring devices. Further, the vacuum packaged devices are inherently robust against dust storm and icing phenomenon which occur for overhead power lines. The proposed analytical method is established based on simplified assumptions and then an accurate method is developed for analysis of vacuum packaged devices. Obtained theoretical results are verified in the laboratory through a prototype of the vacuum packaged piezoelectric device which captures up to 90uW from a 10A line current.

This paper presents a passivity-based control (PBC) scheme for the Switched Reluctance Generator (SRG) in small-scale wind energy conversion systems (WECSs) for DC microgrid application. The main objective is to stabilize the output voltage in case the system supplies constant power loads (CPLs) and operate with maximum power point tracking (MPPT). Stability improvement and dc-link ripple reduction in the presence of CPLs is achieved using system level modeling of SRG-based DC microgrid through the Euler-Lagrange system (ELS) from the view point of the machine physical structure. Compared with other control methods, the proposed MPPT method based on passivity-based speed controller employs the back-EMF in the generation process as a position-dependent voltage source to overcome the major challenge of SRG complicated uncertain dynamic model. To deal with the time-varying inductance and back-emf of SRG, an adaptation mechanism is incorporated in proposed adaptive PBC and the control design is constructed by using the Lyapunov theorem where the closed-loop stability is ensured. The effectiveness of the proposed method in avoiding instability effects of SRG and CPL with voltage ripple reduction and precise wind turbine speed tracking is investigated with simulation results and validated with experimental by using a four-phase, 8/6 SRG drive system.

This paper presents a frequency-weighted impedance method for the characterization of piezoelectric bending beam energy harvesters. The method uses the frequency response of the beam to determine the beam model parameters. Existing methods often need to measure the beam tip deflection for the characterization of the parameters. This requires the accessibility of the tip and advanced measurement tools, such as a laser vibrometer. However, in the proposed method only the knowledge of the base acceleration is adequate to determine the electromechanical coupling coefficient of the beam. Furthermore, the rest of parameters including mechanical damping ratio can be determined based on a pure electrical test. The proposed method is useful for the characterization of all types of piezoelectric energy harvesters, particularly the vacuum-packed ones in which the tip of the beam is inaccessible. The validity of the method is experimentally verified using a test setup including a vacuum-packed piezoelectric energy harvester. The measured parameters of the beam are compared with the bulk material parameters showing that the proposed method can accurately estimate the model parameters without using the information of the tip deflection and with an error less than 4%.

This paper presents the design optimization of a magnetic field energy harvesting platform for self-powered ac power line monitoring devices in smart grid applications. The designed platform can be used with any type of vibration-to-electricity energy conversion schemes including piezoelectric, electromagnetic, and electrostatic energy harvesters. The platform includes a cantilever beam with a miniaturized permanent magnet (PM) at the tip that vibrates due to the interaction with the magnetic field of the ac line. The proposed method analytically determines the optimum geometric orientations of the platform as well as the optimum dimensions of PM to maximize the applied magnetic force to the beam. The validity of the design procedure and its assumptions are verified numerically and experimentally using a piezoelectric energy harvesting platform. The numerical and experimental test results confirm the calculated optimum orientation angles and PM dimensions that maximize the magnetic force. The analysis shows that for a PM with vibration direction in a plane normal to the power line, the maximum force can be achieved at the multiples of +45 degrees with reference to the vibration direction. The optimum orientation angle also depends on the angles between the magnetization vector and the direction of the vibration.