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Online monitoring is an inevitable necessity for dc–dc converters in industrial applications to achieve a fault-tolerant structure, which ensures reliable operation and prevents catastrophic failures. In this paper, a comprehensive monitoring system is proposed for non-isolated dc–dc converters. The proposed approach is mainly focused on monitoring the most prone to failure components of these converters including switching devices and capacitor. Using the proposed monitoring system, switch/diode open circuit and short circuit faults are detected in less than one switching cycle. Furthermore, online monitoring of the capacitor equivalent series resistance and switch on-state voltage as effective precursors of aging is also carried out. Finally, an inter-turn fault detection technique is presented for the converter inductor. The mentioned monitoring tasks are accomplished using only two electrical sensors (for capturing voltages across the converter diode and inductor) and two temperature sensors. The presented monitoring approach is simple, cost-effective, easy to implement, and applicable for all non-isolated dc–dc converters including buck, boost, and buck-boost converters. Performance of the monitoring system is evaluated by considering different scenarios in the experiments carried out on a laboratory prototype. The results confirm the effectiveness of the proposed system for fault diagnosis and aging monitoring in non-isolated dc–dc converters. [ABSTRACT FROM AUTHOR]

Reliable operation of dc–dc converters is vital for many applications. An appropriate converter monitoring scheme is required for fault detection and adoption of effective remedial strategies. Switch faults and degradation of electrolytic capacitor account for a considerable portion of the converter failures. Although rate of diode failures is not remarkable, power switch may be damaged in case of diode fault occurrence. Furthermore, for applications in which a redundant switch is employed as a remedy, it will be also endangered by diode failures if diode fault detection has not been considered in the monitoring scheme. Therefore, diode condition monitoring improves reliability of the converter monitoring approaches. This paper presents a simple diagnosis technique for open-circuit and short-circuit faults of the switch and diode in nonisolated dc–dc converters. The technique only employs diode voltage as the detection signature. The diode voltage and gate driver signal are processed in a simple logic circuit to generate some indicators for switch and diode fault diagnosis. Basis of the technique is discussed in detail. Several experiments have been carried out on buck, boost, and buck–boost converters. The results confirm the technique capability for switch and diode fault diagnosis in less than one switching cycle. [ABSTRACT FROM PUBLISHER]

Power switches and electrolytic capacitors are the most vulnerable components in the power electronic converters. Any failure in these components may result in severe damages, if no remedial action is employed. Prior to any remedy, the first step is fault diagnosis. In this paper, a new type of Rogowski coil sensor is proposed. The sensor captures the inductor current derivative, which contains suitable signatures for switch fault diagnosis and capacitor lifetime monitoring in nonisolated single-switch dc–dc converters. Using the captured signal, detection of switch open-circuit and short-circuit faults is realized by a simple logic circuit. Furthermore, a new capacitor lifetime monitoring technique is proposed, which employs this signal for calculating equivalent series resistance of the capacitor. The proposed sensor has some remarkable advantages. Due to its nonmagnetic core, the problem related to nonlinear response of magnetic cores at high frequencies will not be encountered. Furthermore, the proposed cost-efficient approach can be easily implemented even for already fabricated converters. The performance of the proposed sensor is evaluated using some finite-element simulations and experiments for a buck converter. The results confirm the capabilities of the sensor for switch fault diagnosis and capacitor lifetime monitoring in nonisolated single-switch dc–dc converters. [ABSTRACT FROM PUBLISHER]

Owing to the key role of the power electronic converters in various applications, their reliability is an important issue. The electrolytic capacitor and the power switch are the most vulnerable components of the converters. On fault occurrence in these components, a suitable remedial strategy should be employed to prevent further damages. The first step in any remedial strategy is fault diagnosis including fault detection and identification. This study proposes a technique for switch fault diagnosis and capacitor lifetime monitoring in non‐isolated single‐switch DC–DC converters. The proposed cost‐effective method could be easily implemented using a printed circuit board Rogowski coil (PCBRC) on the capacitor terminals. The derivative of the capacitor current is captured by the PCBRC. The captured signal contains suitable signatures for detection of switch open‐circuit and short‐circuit faults. In addition to switch fault detection, lifetime of the converter capacitor is also monitored by the PCBRC via calculation of the capacitor equivalent series resistance. The proposed technique is implemented for a buck converter. The experimental results confirm the capability of the proposed technique for switch fault diagnosis and capacitor lifetime monitoring in non‐isolated single‐switch DC–DC converters. [ABSTRACT FROM AUTHOR]

Optimization seeks to find inputs for an objective function that result in a maximum or minimum. Optimization methods are divided into exact and approximate (algorithms). Several optimization algorithms imitate natural phenomena, laws of physics, and behavior of living organisms. Optimization based on algorithms is the challenge that underlies machine learning, from logistic regression to training neural networks for artificial intelligence. In this paper, a new algorithm called two-stage optimization (TSO) is proposed. The TSO algorithm updates population members in two steps at each iteration. For this purpose, a group of good population members is selected and then two members of this group are randomly used to update the position of each of them. This update is based on the first selected good member at the first stage, and on the second selected good member at the second stage. We describe the stages of the TSO algorithm and model them mathematically. Performance of the TSO algorithm is evaluated for twenty-three standard objective functions. In order to compare the optimization results of the TSO algorithm, eight other competing algorithms are considered, including genetic, gravitational search, grey wolf, marine predators, particle swarm, teaching-learning-based, tunicate swarm, and whale approaches. The numerical results show that the new algorithm is superior and more competitive in solving optimization problems when compared with other algorithms. [ABSTRACT FROM AUTHOR]

The accuracy of the current transformers (CTs) supplying the generator differential relay is essential in power plant stations. One important factor which decreases the CT accuracy is the stray flux originated from the adjacent phases. During external fault conditions, the currents of adjacent phases contain a considerable decaying DC component. Thus, corresponding fluxes also contain a decaying DC component which cannot be counteracted by bus bar enclosure and generator shell, completely. Hence, the CT output signal deviates from the correct waveform which may lead to undesirable operation of the differential relay supplied by the CT. In fact, there is no internal fault in the generator but the differential relay trips the breaker due to negative impact of stray flux on CT accuracy. In this paper, a real power plant bus bar is modeled using three-dimensional (3D) finite element method. Then, the effect of the stray flux on the accuracy of the CTs is studied. Finally, flux equalizing windings are considered on the CT’s secondary winding. According to finite element simulation results, the negative impact of the stray flux on the CT accuracy is decreased considerably by the flux equalizing windings. [ABSTRACT FROM PUBLISHER]

Electric train system is a very large load for the power network. This load consumes a large amount of reactive power. In addition, it causes a massive unbalance to the network, which results in many problems such as voltage drops, high transmission losses, reduction in the transformer output ability, negative sequence current, mal-operation of protective relays, etc. In this paper, a novel real-time optimization approach is presented to adjust the static VAR compensator (SVC) for the traction system to realize two objectives; current unbalance reduction and reactive power compensation. A multi-objective optimization technique entitled non-dominated sorting genetic algorithm (NSGA-II) is used to fulfill the regarded objectives simultaneously. A comprehensive simulator has been designed for electric train network modeling that is able to adjust the parameters of SVC in an optimum manner at any time and under any circumstances. The results illustrate that the provided method can efficiently reduce the unbalancing in current as well as supply the demanded reactive power with acceptable precision. [ABSTRACT FROM AUTHOR]

In this paper, a high-voltage unipolar pulse power generator is introduced for electroporation applications. Operating principle of the proposed structure is based on the buck–boost (BB) converter. The generator is comprised of parallel modules connected to the converter through an SCR and is supplied by a low-voltage dc source. Each module consists of an insulated gate bipolar transistor (IGBT), two diodes, and a capacitor. In fact, the proposed topology is a combination of the Marx generator and BB (MG-BB) converter. In comparison with other modular MG-BB structures, the proposed topology achieves interesting advantages including simpler structure, reduction of IGBTs voltage rating, and reducing number of components (inductors and switches). In order to clarify the features of the proposed structure, it has been compared with other unipolar MGs considering different aspects including the number of circuit components, number of required input supplies, amplitude of the output pulse, and the maximum voltage across switches and diodes. To validate the effectiveness of the structure, simulation and experimental results are presented. The results confirm that the proposed topology is capable of generating unipolar pulses with desirable amplitude and repetition frequency using a low-voltage dc supply. [ABSTRACT FROM AUTHOR]

In this paper, a new structure of Marx generator (MG) based on buck--boost converter is proposed to generate high-voltage pulses. In this structure, a single-phase inverter is employed to supply parallel diode--capacitor units by positive and negative values of the input dc source (±Vin). The main contribution of this paper is proposing a new switching strategy, by which a group of capacitors are charged properly. Finally, the charged capacitors are connected in series such that the output voltage is equal to summation of the capacitors' voltages. Considering specified value of the output voltage, the number of circuit elements in the proposed structure is reduced in comparison with other topologies of unipolar MG. Furthermore, voltage rating of switches and diodes in the proposed topology is lower than that of other unipolar MG structures. Design of the structure ensures that there is no need to connect the switches in series, when the number of stages is increased. To verify the performance of the proposed MG structure, simulation has been carried out in MATLAB/Simulink. Furthermore, a prototype of the proposed structure has been implemented in the lab. The simulation and experimental results confirm the capability of the structure for generating high-voltage pulses. [ABSTRACT FROM AUTHOR]

Switched reluctance motors (SRMs) are extensively utilised in electric vehicles (EVs) due to some outstanding capabilities such as rugged and fault tolerant structure. Since the excitation of the phases is performed independently in the SRM, the motor could continue operation even in case of fault occurrence in one of the phases by disabling the faulty phase. However, to improve the reliability of the SRM for EV applications, an efficient fault diagnosis approach should be employed. In this study, an on-line method for detection of winding inter-turn short-circuit fault in the SRMs is presented. The proposed technique is based on a model, in which the extended Kalman filter is utilised. The method achieves a fast response, thus, the remedial strategies could be employed at the initial moments after fault occurrence. The proposed method is simple to implement and reliable in practice. The performance of the proposed approach is verified using some simulations and experiments. The results confirm high capability of the method in different conditions. [ABSTRACT FROM AUTHOR]

Switched reluctance motors (SRMs) are extensively utilised in electric vehicles (EVs) due to some outstanding capabilities such as rugged and fault tolerant structure. Since the excitation of the phases is performed independently in the SRM, the motor could continue operation even in case of fault occurrence in one of the phases by disabling the faulty phase. However, to improve the reliability of the SRM for EV applications, an efficient fault diagnosis approach should be employed. In this study, an on‐line method for detection of winding inter‐turn short‐circuit fault in the SRMs is presented. The proposed technique is based on a model, in which the extended Kalman filter is utilised. The method achieves a fast response, thus, the remedial strategies could be employed at the initial moments after fault occurrence. The proposed method is simple to implement and reliable in practice. The performance of the proposed approach is verified using some simulations and experiments. The results confirm high capability of the method in different conditions. [ABSTRACT FROM AUTHOR]