1,720,968 research outputs found
Comparative study on tuning methods for variable speed drives
No full textThe aim of this study is to analyse the tuning and compare the performance of four well known speed control algorithms used in variable speed drives: the proportional-integral, integral-proportional, two degrees of freedom proportional-integral and state feedback motion controllers. The study compares pole-placement-based tuning with command-tracking frequency response function (FRF) based tuning. The assessment is focused on the resulting command tracking, mechanical impedance, and sensitivity FRFs. Simulation and experimental results confirm that tuning the controllers with the command-tracking FRF approach leads to an increased disturbance rejection capability of the speed loop
Experimental assessment of induction motors fed by Sub-MHz-PWM wide band gap inverters
Full text linkThree phase inverters with switching frequencies above 100 kHz have recently become feasible thanks to the significant progress made in wide band gap semiconductor technology. The main drivers behind the intense research and development of these ultra-high switching frequency PWM inverters are the extraordinary gravimetric and volumetric power densities that can be achieved. On the other hand, not as much attention has been devoted to the loads that these inverters supply, quite frequently consisting in ac motors. The impact of sub-MHz PWM and of the associated tens of nanoseconds range switching transients on motor terminal overvoltage, common mode currents and losses are still to be discussed exhaustively. The authors have thus decided to investigate what happens to induction motors supplied by inverters having switching frequencies up to 350 kHz. After an introduction on wide band gap semiconductor devices, the paper presents some interesting experimental observations conducted on a 1.1 kW 4-pole induction motor fed by a silicon carbide inverter. Further insight is provided by tests on a laminated steel toroid, supplied by a single-phase full bridge silicon carbide inverter. Discussions on the experimental results highlight the previously unreported impact of common mode losses, which become a predominant part of the PWM harmonic losses
Signal-injection-aided position and speed estimation for PMSM drives with low-resolution position sensors
No full textThe aim of this paper is to reduce the low-speed limitation of PMSM drives that use low-resolution position sensors. It is recognized, for the first time, that this may be overcome by merging signal-injection-based self-sensing and low-resolution sensor technologies, if the machine possesses a detectable amount of electromagnetic saliency. The supplementary information coming from the injection of an additional high frequency magnetic field may be used to aid the low-resolution-based position and speed estimation algorithm, significantly improving the low-speed performance of the drive. In this research contribution, the quantization-harmonic decoupling vector-tracking observer is used for speed and position estimation. It is shown how this algorithm can be easily integrated with any high frequency signal injection method. Extensive experimental results are provided demonstrating the significant performance improvements at low speeds for a PMSM drive using 1, 2 and 3 bit-per-pole-pair sensing systems, when signal injection is used to aid position and speed estimation
Coupled hydraulic and electronic regulation of cross-flow turbines in hydraulic plants
No full textThe potential benefit of coupling hydraulic and electronic regulation to maximize the energy production of a cross-flow turbine in hydraulic plants is analyzed and computed with reference to a specific case. Design criteria of the cross-flow turbine inside hydraulic plants are first summarized, along with the use of hydraulic regulation in the case of constant water head and variable discharge. Optimal turbine impeller rotational speed is derived, and traditional as well as innovative systems for electrical regulation are presented. A case study is analyzed to evaluate the potential energy production according to the expected monthly mean flow distribution and two possible choices: CFT1 with the hydraulic regulation, and CFT2 with coupled hydraulic and electric regulations. The return time of capital investment (RCI), computed for both the solutions, showed that the CFT2 solution provides an increment of the total produced energy, along with an increment of approximately 30% of the corresponding RCI. The sensitivity of the results to water head variability and to possible different pipe design criteria in future scenarios is finally discussed
Impact of closed loop pole placement on the low speed performance of VFDs using low-resolution position sensors
No full textThe main aim of this paper is to investigate the influence of speed loop pole locations on command tracking and torque disturbance rejection at low speed in variable speed drives using low-resolution position sensors. The study considers a fixed position speed estimation algorithm, and experimental tests have been conducted on a 3kW permanent magnet synchronous motor drive. The experimental results validate the effectiveness and feasibility of the theoretical study
Fault-Decoupled Instantaneous Frequency and Phase Angle Estimation for Three-Phase Grid-Connected Inverters
No full textFrequency and phase angle estimation is a key aspect for grid-connected inverters that are required to guarantee low-voltage fault-ride-through capability. Over the past two decades, a number of estimation algorithms have been proposed, mostly based on the well-known phase-locked loop (PLL). It has been demonstrated that standard PLLs do not perform correctly in abnormal grid conditions, due to the oscillations produced in the frequency and phase angle estimates by the voltage harmonics. This paper introduces a new, general approach to harmonic decoupling and presents a highly intuitive and simple scheme, applying it to an αβ-PLL; compensation of any desired number of harmonic components is possible. Two implementations of this decoupling scheme are presented. It is shown that the performances of the resulting fault-decoupled PLLs are comparable with those of other advanced frequency and phase angle estimation structures
2016 IEEE IAS Industrial Drives Committee Third Prize Paper Award
No full textThis paper investigates Hall-effect sensor faults in brushless dc drives and proposes a very effective methodology for their detection, identification and compensation. It is shown that these faults cause erroneous commutation, generally leading to unstable operation. By using a fault detection and identification technique proposed by the authors in a previous paper related to low cost field-oriented drives, together with appropriate fault-compensated position and speed estimation algorithms, it is shown for the first time that proper operation is guaranteed for both single and double faults. Comparative experimental results are provided for operation with three state of the art, Hall-effect sensor based, estimation algorithms: the zeroth order algorithm, the hybrid observer, and the vector-tracking observer. It is verified that stable operation is achieved with three, two or only a single Hall-effect sensor functioning correctly
On the effects of ultra-high switching frequency on PWM-inverter-fed induction motors
No full textWhen the 'ultra-high switching frequency' concept is evoked, the mind immediately runs towards the wide bandgap semiconductors and to inverters having unimaginable gravimetric and volumetric power densities. More rarely, people are interested in the effects of very high frequency pulse width modulation on the electrical load, particularly when considering 'rugged' induction machines. Starting from this observation and being aware that these inverters are dedicated only to 'special' machines and applications, the authors decide to investigate what happens - in a broad sense - to induction motors supplied by inverters with switching frequencies up to 350 kHz. After an introduction on wide-bandgap semiconductor device technologies, the paper presents some interesting experimental observations conducted on a 1.1 kW 4-pole induction motor fed by a silicon carbide inverter
A new method to select rotor position sensor resolution in variable speed drives
No full textThe aim of this research is to present a new method for the selection of position sensor resolution in variable speed drives. The proposed approach links the minimum sensor resolution Nds to the required drive performances, expressed in terms of desired quantization speed harmonics attenuation and speed control loop bandwidth, both defined at the minimum requested operating speed. Although the selection of rotor position sensor resolution is presented for a vector tracking observer, this approach is general and can be used in conjunction with the operating point model of any speed estimation algorithm. Simulations and experimental results validate the effectiveness of the proposed method
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