The widespread implementation of DC energy distribution systems is hindered by the multiple challenges that subsist regarding the protection of these systems. Many DC circuit breaker (DCCB) topologies have been proposed to overcome the challenges of DC protection, including the absence of zero-crossing points and very fast rising rate of the fault current. Within DC circuit breaker topologies, solid-state circuit breakers (SSCBs) reveal as a good option for the protection of low-voltage DC systems and are known for their fast operation. Despite the important advancements made so far in SSCB technology, cost reduction, structural complexity minimization, control optimization, and reliability remain some of the priorities in the construction of new SSCBs. To promote a simpler and cost-effective solution, this paper provides a SSCB structure suitable to simultaneously provide protection for two loads, featuring reduced components count and simple control. Besides, a single energy absorbing component is used for the whole SSCB, while maintaining the safe operation of the SSCB and, consequently, of the whole grid.

Power converters are one of the main elements of numerous critical systems. These converters are composed of several components, some of which are particularly vulnerable, namely semiconductors and capacitors. Therefore, monitoring those components' condition is fundamental, mainly in applications that require high reliability and safety. One of the most commonly used capacitor in power converters is the aluminum electrolytic capacitor (AEC), whose aging manifests itself through an increase in its equivalent series resistance (ESR) and a reduction in its capacitance (C). Several techniques have been proposed to assess the AEC state of health, having the Equivalent Series Resistance (ESR) value as a reference. For this purpose, a current sensor is used in the capacitor branch. However, the current sensor imposes practical restrictions; namely, it requires space and introduces an unwanted resistive and inductive effect. In this paper, a Decision Tree Regressor (DTR) based model, combined with the Short Time Least Squares Prony's (STLSP) approach is used to detect the fault. At first, the STLSP algorithm is used to train the DTR model to predict the capacitor current amplitude (A-Ic). Then, using both STLSP and DTR algorithms, it is possible to estimate the ESR value without the need to use a current sensor inside the converter.

Multilevel DC–DC power conversion solutions reveal excellent features for implementation in energy management and storage applications, such as electric vehicle (EV) charging. Conventional control approaches applied to multilevel converters show weaknesses in preserving optimal conversion performance. Despite the potential improvements in terms of control robustness, attainable through the exploitation of model-based predictive control (MBPC) approaches, parameter sensitivity of such control approaches shows potential to deteriorate the response of the converter. To overcome such challenge, this paper describes a novel Model-Free Predictive Control (MFPC) approach suitable for multilevel DC–DC power converters, convening in a single solution the benefits of predictive control and insensitivity against parameter uncertainty, which is particularly concerning in energy storage applications. A set of operation scenarios confirm the effectiveness of the proposed MFPC in both steady- and transient-states.

A novel online inter-turn short circuit (ITSC) fault and Unbalance Supply Voltage (USV) detection system is to be introduced and tested. The proposed indicators, which are based on the stator’s voltage and impedance symmetrical components ratio, offer reduced calculations, non-invasive and a relatively affordable budget solution. This paper presents the introduction of a new scheme that distinguish between the ITSC fault and USV condition. Using the stator’s windings impedances estimated from the magnitudes of the fundamental spectrum component of both current and voltage signals measured using the Short Time Least Square Prony’s (STLSP) method. The online implementation of this method is performed on a LabVIEW environment. The work was validated using experimental results, taking into consideration different operating conditions and the different types of stator connections (Star and Delta connections (Y/Δ)).

This paper proposes a single inductor multiple output (SIMO) driver architecture for RGB LEDs with hybrid dimming technique, for use in large installation, with minimal loss of luminous flux and light flickering. Among other benefits, the proposed dimming technique provides improved accuracy in the color control, while maintaining low current ripple. Such advantages are easily attained, even when resorting to a simple SIMO LED driver. To confirm the effectiveness of the proposed hardware and software architecture, a comprehensive set of scenarios is established and tested resorting to a simulation model of the LED system.

This paper presents the calculation of the AC loss factor of a hairpin winding configuration using an analytical approach. For this purpose, the layer conductor model is developed to evaluate the AC loss factor. Moreover, the numerical model was created, and the collected numerical data was used to successfully validate the proposed analytical method.

Under abnormal electrical supply conditions, induction motors can easily reach an overheating condition. A continuous operation under thermal stress significantly decrements the motors useful lifetime. In this paper a short-time thermal transient analysis, based on a Lumped Parameter Thermal Network (LPTN), is performed in order to evaluate the thermal behaviour of an asynchronous machine operating under supply voltage unbalance. Three types of supply unbalance are considered in this paper: unbalanced voltage amplitude, unbalanced phase, and a combination of both. The analytical model is used to estimate the temperature in different points of the stator. This model presents a reasonable compromise between simplicity, accuracy, and rapidity. The obtained results are validated using an experimental prototype.

Most of the state-of-the-art LED drivers employed in lighting applications adopt current control strategies that rely on current sensing resistors. In multi-string LED lighting systems, commonly based on the single inductor multiple output (SIMO) topology, a current sensing resistor is typically inserted in each string, allowing to precisely control the current flowing through each string. This current control approach presents critical drawbacks: 1) the overall energy conversion efficiency is seriously affected by the fairly high number of current sensing resistors; 2) the system complexity is enhanced, as each LED string requires a current control loop; 3) the lifetime of both LEDs and drivers suffers an important depreciation due to the additional power losses incurred by the current sensing resistors. To overcome such drawbacks, this paper proposes a sensorless current control strategy suitable for LED drivers operated at continuous conduction mode (CCM), feeding multi-string LED lighting systems, which obviates the requirement of individual string current control. The proposed control strategy is implemented and validated on a fault-tolerant SIMO LED driver.

Stator electrical faults are considered the most severe and challenging to detect among the various induction motor faults. This is due to the fast evolving severity level that leads from an early inter-turn fault to the machine breakdown. Many works have been published over the years presenting a variety of diagnostic techniques to detect this fault. However, the fault level severity is kept high enough to allow for the diagnosis neglecting the fact that at that severity level the machine will fail and thus diagnosis of the fault is useless. This paper challenges the existing technical know-how in the subject, while attempting to detect the fault at very low severity levels. It will be shown with extensive experimental testing and analysis that many well established methods are completely unreliable for this task. Finally, the authors propose a novel method that is able not only to detect the fault reliably but is also sensitive to the fault level severity.

Conventional Finite-Control-Set Model Predictive Torque Control (FCS-MPTC) suffers from the high computational burden and the weighting factor tuning effort, which increase the flux and torque ripples and have a negative impact on the drive performance. Accordingly, this paper presents an enhanced FCS-MPTC for Permanent Magnet Synchronous Motor (PMSM) drives with reduced computational effort and without the use of weighting factors. Based on the use of a new 2-D lookup table (LUT) of Direct Torque Control (DTC) and different from prior method using eight predicted voltage vectors in the cost function, only three voltage vectors are predicted and evaluated, which reduce notably the computational effort. Furthermore, with the aim to eliminate the weighting factors in the cost function, the torque and flux vector references are converted into an equivalent angle between the stator and rotor flux vectors, which decreases the current and flux ripples and improves the control performance. Simulation results are presented to show the effectiveness of the proposed control method.

Aluminum electrolytic capacitors (AECs) are widely used in the DC link of power converters, such as the three-phase interleaved boost converter (IBC) which offers many advantages over the conventional amplifier converter. IBCs can operate both in closed- or open-loop systems and any fault in the converter components can reduce significantly the overall system performance. AECs failures represent the major cause for power electronics equipment breakdown, mainly due to both aging and temperature effects involving significant increase on their equivalent series resistance (ESR) parameter. This reveals the importance of developing robust control strategies that allow evaluating the electrolytic capacitor state condition and keeping, at the same time, the performance of the converter controller, even under a capacitor fault occurrence. For that purpose, a fault detection and control strategy is proposed in this paper, for a three-phase interleaved boost converter application. The control task of this strategy uses a mixed sensitivity H∞ controller to ensure fast dynamics and robustness even under failure mode operation, while the fault detection task uses the Short Time Least Square Prony's (STLSP) method to perform an online estimation of the ESR parameter, allowing a continuous evaluation of the electrolytic capacitor state condition, and consequently avoiding a total system failure. The effectiveness of the proposed strategy is verified by several experimental tests.

This paper presents a fault-tolerant permanent magnet synchronous generator (PMSG) drive for wind turbine systems, with the ability to handle power semiconductor open-circuit (O-C) faults in the full-scale back-to-back converter. The fault-tolerant topology consists of a five-leg converter, with a shared leg connected to a generator phase and to its corresponding grid phase. The main contribution of this paper consists on the development of an alternative vector-control-based pulse-width-modulation (PWM) control scheme for both machine-side converter (MSC) and grid-side converter (GSC), allowing to reduce the dc-bus voltage ratings. Moreover, a reliable fault diagnosis algorithm is also integrated, providing the information required to instantaneously trigger fault-tolerant remedial strategies, without any additional sensors. Simulation and experimental results are presented to validate the effectiveness of the proposed fault-tolerant PMSG drive.

DC-DC converters face an exponential growth in the context of the ever-increasing use of DC grids, namely at the home and business levels. In this domain, efficiency and reliability are of major concern. Solutions already available in the literature concerning fault-tolerant DC-DC converters do not consider the application of such converters in household environments and their constraints. To solve this problem, this work presents a simple, yet effective, way to detect power switches open-circuit faults in DC-DC converters that use a current control strategy. In opposition to the complex model-based approaches, this paper introduces an intuitive signal-based analysis for fault detection purposes. The proposed method was simulated in an interleaved DC-DC boost converter, and the obtained results demonstrate its effectiveness to detect multiple faults in the converter power switches, even under harsh operating conditions.

Condition monitoring and fault diagnosis are considered key features in order to increase the reliability and availability levels of wind turbine systems. Accordingly, this paper proposes a single fault diagnostic algorithm for multiple IGBTs open-circuit faults and current sensor faults in direct-driven wind turbines, based on permanent magnet synchronous generators with full-scale back-to-back converters. The proposed method is based on the currents residual generation and on a new adaptive threshold approach. This threshold is calculated from the measured currents and their corresponding reference signals that are already available from the main control system. The proposed diagnostic technique is applied to both generator-side and grid-side converters of a conventional back-to-back topology. Several simulations are presented, showing the algorithm reliability against false alarms under both multiple IGBTs and current sensor faults in the back-to-back converter.

This paper presents a theoretical study and an experimental analysis of a stand-alone, low-cost wind turbine system proposed to be used in rural and remote areas, implementing the maximum power point tracking (MPPT) with the Hill-Climb Searching (HCS) control via Perturb and Observe (P&O) method. In order to prove how effective the MPPT was for a low-cost wind turbine suitable to be installed in rural areas, the proposed system was first simulated and then the results were compared with experimental data obtained by tests measuring the system functionality and MPPT capability under the same conditions. The implemented M PPT method was validated varying both the wind speed and the time interval corresponding to each wind speed to observe the transient behavior.

This paper presents a novel technique based on evolutionary algorithms for identifying severity of ball bearing faults in three-phase induction motors. The proposed technique can be used to determine if the induction motor bearings are still in healthy condition or there is some defect at their inner or outer raceway. These defects cause basic motions on the air gap distribution that can be recognized as temporary air gap eccentricity. The particle swarm optimization algorithm is used to estimate severity of the resultant temporary air gap eccentricity. At this end, a rather exact model of the induction motor is required with the proposed bearing faults at variable severities. Winding function approach is extended to develop such model. This is a non-invasive technique because it uses only the line voltages and line currents of the stator. Other advantages of this method include: insensitive to unbalanced supply voltage, load level variation and temperature variation. The proposed technique is evaluated using simulation data obtained for a 2.2 kW three-phase induction machine. The simulation results demonstrate the effectiveness of the proposed technique for the diagnostics of the bearing faults.

It has been reported in the past that, the non-adjacent broken rotor bars in three-phase induction motors can influence the diagnostic ability of the line current frequency spectrum. In this paper, the traditional line and zero-sequence current broken rotor bar fault signatures are studied for different broken rotor bar fault configurations. More specifically, the cases to be investigated are healthy, one broken bar, two adjacent broken bars and two non-adjacent broken bars. The results shown in this paper lead to the conclusion that the zero-sequence current presents several advantages compared to the traditional line current-based method. This can be especially useful in industrial motors where there is the possibility of measuring these currents since it can help to avoid some false negative cases obtained with the conventional Motor Current Signature Analysis.

A new fault diagnostic method is presented in this paper for bidirectional half-bridge DC-DC converters. This algorithm uses only the converter control variables without requiring extra-sensors and its implementation requires only a minimum computational effort. Simulation results in a wind power system including supercapacitors and batteries have been used to validate the fault diagnostic method under different operating conditions.

In this paper, the instantaneous active and reactive power signature analyses are presented for stator fault diagnosis in operating squirrel cage three-phase induction motors either directly connected to the mains or fed from inverters. Both simulation and experimental results are presented to show the effectiveness and the merits of the proposed approach that offers the possibility to detect this type of fault and to discriminate it from other abnormality conditions responsible for the same motor behavior by comparing the signature analyses of the two considered quantities.

Energy storage systems are mandatory in renewable energy based power supplies. They work as both an energy buffer and a backup. Regarding the renewable energy sources intermittent behavior and the load profile, high energy and power density are important requirements. To achieve both, this paper presents a modular design of a hybrid storage system including supercapacitors and batteries, benefiting from resizing possibility, optimized control strategies and improved reliability. Its performance in a renewable energy standalone power supply is analysed.

The reliability of bidirectional dc-dc converters is a critical issue in many applications where the power flows from or to energy storage systems regularly, such as automotive applications and standalone power systems. This paper addresses dual active bridge converters faulty operation and proposes a fault detection method.