On the reliability of electrical drives for safety-critical applications

The aim of this work is to present some issues related to fault tolerant electric drives,which are able to overcome different types of faults occurring in the sensors, in thepower converter and in the electrical machine, without compromising the overallfunctionality of the system. These features are of utmost importance in safety-criticalapplications. In this paper, the reliability of both commercial and innovative driveconfigurations, which use redundant hardware and suitable control algorithms, will beinvestigated for the most common types of fault: besides standard three phase motordrives, also multiphase topologies, open-end winding solutions, multi-machineconfigurations will be analyzed, applied to various electric motor technologies. Thecomplexity of hardware and control strategies will also be compared in this paper, sincethis has a tremendous impact on the investment costs

Power Loss Modelling of GaN HEMT based 3L ANPC Three Phase Inverter for different PWM Techniques

The paper presents a straightforward modelling approach to compute the power loss distribution in GaN HEMT based three phase and three level (3L) active neutral point clamped (ANPC) inverters, for different pulse width modulated techniques. Conduction and switching losses averaged over each PWM switching period are analytically computed by starting from the operating conditions of the AC load and data of GaN power devices. The accuracy of the proposed analytical approach is evaluated through a circuit based power electronics simulation tool, applied to different carrier-based PWM strategies.Comment: 10 pages, 13 figures, 24th European Conference on Power Electronics and Applications ( IEEE EPE 2022 ECCE Europe). This work has been carried out in the framework of the ECSEL-JU Project GaN4AP (Gallium Nitride for Advanced Power Applications) - Grant Agreement No.10100731

On the effects of position sensor resolution in variable speed drives

The aim of this paper is to further the knowledge on the inherent limitations imposed on variable speed drives by the resolution of the rotor position sensor. Starting from the well-known spatial harmonic formulation of quantized rotor position measurement, time harmonic formulations of both quantized position and speed are derived, which are valid under generic periodic torque disturbances. These formulations, based on modulation theory, justify the presence of otherwise unexplained additional rotor speed harmonics that are induced by the drive when subjected to torque disturbances. Simulations are provided to verify the correctness of the proposed mathematical representations

Fault-decoupled instantaneous frequency and phase angle estimation for three-phase grid-connected inverters

Frequency 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 don't 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

Coupled hydraulic and electronic regulation of cross-flow turbines in hydraulic plants

The 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

Performances analysis of non-model-based speed estimation algorithms for motor drives

This paper investigates the performances of speed-controlled motor drives using non-model-based speed estimation algorithms. A suitable modelling of the speed estimation algorithms combined to the analytical representation of the instantaneous quantized speed of finite resolution position sensors are exploited to evaluate the filtering action of the estimation algorithms, and the stability and rejection to torque disturbances of speed-controlled drives at low rotational speeds; the last operating condition is very critical for motor drives, especially for that using low resolution position sensors. In this study, the theoretical analysis is experimentally validated on a 2kW PMSM drive

Fault-Decoupled Instantaneous Frequency and Phase Angle Estimation for Three-Phase Grid-Connected Inverters

Frequency 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

Signal-injection-aided position and speed estimation for PMSM drives with low-resolution position sensors

The 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

Hall-effect sensor fault detection, identification and compensation in brushless DC drives

This 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, [22], 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, [19], the hybrid observer, [20], and the vector-tracking observer, [21]. It is verified that stable operation is achieved with three, two or only a single Hall-effect sensor functioning correctly