Fault-tolerant Capability Research Articles

A seven level fault tolerant hybrid cascaded inverter for renewable energy applications

Abstract The cascaded H-bridge (CHB) inverters are the prominent inverters used for renewable energy applications. Fault-tolerant operation is one of the foremost concerns to safeguard the continuous operation of the system under a fault on semiconductor switches and DC power supplies. A novel hybrid CHB inverter is proposed by adding a seven-level boost SLB module in cascade with the H-bridge modules. The proposed topology ensures the reliable and dynamic operation of the inverter during the occurrence of a fault. In addition to the fault-tolerant capability of the SLB inverter, the proposed design provides the voltage boosting and self-balancing of the switched capacitors. Extensive simulation results at different operating conditions substantiate the concept of the proposed novel fault-tolerant inverter structure. The prototype system is developed in the laboratory and the experimental results validate the proposed system configuration.

Review of High-Power-Density and Fault-Tolerant Design of Propulsion Motors for Electric Aircraft

As the electrification process of aircrafts continues to advance, the propulsion motor system, as its core component, has received more attention and research. This paper summarizes and analyzes the development status, research focus and typical cases in this field in recent years. Firstly, it analyzes the basic structure and principle of five common motors, summarizes the current status of their respective applications in electric aircrafts, and compares them to determine the most suitable type of motor for use as a propulsion motor, focusing on various performance indexes. Then, the optimized design of propulsion motors is generally divided into two categories, namely high power density and fault tolerance. Starting from the basic relationship equation of motor design, the basic method to improve the power density of motors is pointed out; at the same time, according to the basic principles and objectives of the fault tolerance of motors, the fault tolerance design is divided into two aspects, namely the redundant design and the design to improve the fault tolerance capability. Finally, this paper summarizes the current development status of the propulsion motor system and the existing problems and points out the main development direction of this field in the future, so as to provide reference for the further development of the electric propulsion system of aircraft.

Multi-objective optimization of two-stage AC–DC power supply for reliability and efficiency using NSGA-II and meta-heuristic honey bee algorithms

This paper introduces a novel approach to simultaneously optimize the reliability and efficiency of a switching power supply (SPS) using the Non-dominated Sorting Genetic Algorithm (NSGA-II) and Honey Bee Algorithm (HBA). The proposed method uses a Markov model to evaluate the reliability of the converter and maximizes objective functions, including efficiency and reliability, using optimization algorithms to identify the optimum values of the converter parameters. The optimization algorithm determines the optimal values for converter parameters, such as switching frequency, transformer turn ratio, and DC-link voltage. It also fine-tunes circuit components, such as the power factor correction inductor, DC-link capacitor, and output filter components. A sensitivity analysis is carried out to assess the impact of various parameters on the multi-objective functions of the converter. The converter’s reliability and mean time to failure (MTTF) are evaluated using the Markov reliability model, considering all components’ short and open circuit faults. The failure rates of converter components are calculated using the MIL-HDBK-217 methodology. The results obtained from the NSGA-II and HBA are compared to identify the superior algorithm with the best-optimized parameters. Simulation results indicate that the proposed optimization technique enhances the converter’s reliability performance while maintaining its efficiency. Furthermore, this paper presents comprehensive analyses, comparisons, and experimental findings to demonstrate the converter’s fault-tolerant capability. The multi-objective optimization approach offers a practical and effective strategy for optimizing switching power supplies for efficiency and reliability

Comparative Study on Fault-Tolerant Triple Three-Phase PM Machine Drive With Five Modular Windings

In this paper, five different triple 3-phase windings are presented for fault tolerant PM machine drive to achieve advanced turn short circuit fault (TSCF) current reduction effect. First, the five different winding configurations are briefly introduced and the reasons of TSCF reduction effect is explained. Then, the healthy performance and fault tolerant capabilities of several fault modes are investigated by detailed finite element (FE) prediction and test verification. They exhibit almost the same healthy performance. It is demonstrated that the zero sequence (ZS) flux linkages in Y connected winding is the fundamental factor of the huge TSCF current since the Y winding does not contain ZS current path. Thus, the Y-Δ winding exhibits the best the TSCF current suppression capability which creates the ZS current path to nullify the ZS flux linkages, and the delta winding ranks as the second which contains larger ZS circuit. The investigation provides effective approaches and solutions to obtain enhanced fault tolerant capability on the worst TSCF for the safety critical applications.

Position Sensorless Control of Dual Three-Phase IPMSM Drives With High-Frequency Square-Wave Voltage Injection

Dual three-phase interior permanent-magnet synchronous motor (IPMSM) drives have received more attention by the merits of better fault-tolerant capability and lower torque ripples. To improve the reliability of the system against failures in position sensor, it is necessary to investigate the position estimation method for dual three-phase IPMSM drives. The high-frequency (HF) signals injection is utilized for position estimation in three-phase IPMSM drives during low-speed operation region. However, the torque ripples are inevitable owing to the mixing of fundamental and HF components in the same control space for three-phase IPMSM drives. In this paper, the position sensorless control method has been proposed by injecting HF square-wave voltage in the harmonic subspace for the dual three-phase IPMSM drives. Since the harmonic subspace is decoupled from the torque subspace, the torque disturbance can be mitigated well with the proposed HF signal injection based position sensorless method. Moreover, the digital filters in signal extraction and current feedback can be avoided and the signal separation process becomes easy with the proposed method. The experiments have been conducted to validate the performance of the proposed method.

Performance evaluation of five‐level packed U‐cell inverter and its fault‐tolerant variants

SummaryIn the power electronics industry, reliability is of utmost importance to manufacturers. Power semiconductor devices are extensively utilized in multilevel inverters (MLIs), which results in increased failure probability. MLI structures have a significant impact on the system's overall reliability. MLIs with a high degree of reliability reduce system maintenance costs and improve efficiency and the life of the entire system. This paper presents a comprehensive evaluation of five‐level packed U‐cell (PUC5) inverter, modified five‐level PUC (MPUC5) inverter, and their fault‐tolerant (FT) variants with respect to reliability, degree of fault tolerance, power loss and efficiency, and cost. A more accurate reliability evaluation method is used in this work in which failure rates of each component of inverter topologies under healthy and post‐fault conditions are calculated. Hence, this method provides more accurate reliability function of an MLI topology as compared to other methods in which failure rates are assumed to be same for all switches. Typhoon HIL‐402 emulator is used to demonstrate the FT capabilities of topologies in hardware‐in‐the‐loop (HIL) environments.

DC-Bus Voltage Sensorless Control of an Active Rectifier with Modular Multilevel Converter

The modular multilevel converter (MMC) is recognized as one of the promising converters for the electrification of ships and railways. Among different energy conversion stages, the MMC-based rectifier should realize stable DC output voltage and accurate input current control. However, output DC-bus voltage sensors must be installed, which are costly and bulky. This paper presents a simple but effective control method for the MMC-based rectifier, removing the traditional output DC-bus voltage sensor. An accurate evaluation model of DC-bus voltage is developed as well as the implementing method. Meanwhile, a safe and fast pre-charging scheme is presented for the MMC-based rectifier without output voltage sensors. The fault-tolerant capability of the proposed method when the failure of the output DC-bus voltage sensor occurs is examined. Simulated and testing results demonstrate that the proposed method presents not only excellent steady-state and dynamic performance but also strong fault-tolerant capability. The proposed evaluation model for DC-bus voltage has a high accuracy with an error of less than 1%. Besides, the pre-charging time is less than 0.5 s using the proposed sensorless control.

Computer and experimental analysis of a reconfigurable staircase module-based multi-level inverter with fault tolerant capability

In the conventional multilevel inverters, occurrence of a fault in one or more power switches can cause abnormal changes in the output waveforms. Besides, increasing the applied power switches results to an increase in the possibility of fault on the power switches. Accordingly, providing a comprehensive structure with high fault-tolerant capability is one of the vital requirements and critical challenges. To tackle these issues, this study first presents and explores a new basic unit and staircase module (SM) and then extends and optimizes it to yield a reconfigurable multi-level inverter (MLI) with more levels and different goals. The proposed MLI can continue to operate when open-circuit faults in switches. This advantage of the proposed structure is achieved without any redundant legs or switches. For further investigation, a comparison is made in terms of the number of power switches, drivers, dc sources, and reliability between the proposed and similar structures. To control the output voltage levels, the strategy of fundamental frequency switching triggers the configured topology. The carrier signals are reconfigured under fault conditions based on levels to be generated by bypassing the faulted switch. The validity of the established MLI with its fault-tolerant capability is certified through both computer simulations using the MATLAB/Simulink platform and laboratory prototype implementations.

Experimental analysis of advanced control technique for a five‐phase direct matrix converter based on space vector PWM

AbstractThe multiphase matrix converter outperforms the conventional three‐phase system with higher fault tolerance capability and higher power control competency. This paper discusses the direct control based on different possible switching combinations of a three‐phase to five‐phase matrix converter (MC). The proposed control topology significantly reduces the switching commutations in a switching cycle when compared with its counterpart. The control is based on the modified space vector pulse width modulation (SVPWM) strategy. The proposed space vector scheme intelligently selects the voltage vectors to get the desired output characteristics with the least possible switching transitions in a switching cycle. Three possible cases exist in controlling space vectors based on their magnitude, the number of active switching vectors, and their commutations. The results for three different cases of SVPWM have been presented and compared. The total harmonic distortion (THD) obtained in the output is lower in case 2; however, it suffers from a higher common‐mode voltage (CMV). The scheme has been successfully implemented and verified in hardware.

Optimal intelligent fuzzy TID controller for an uncertain level process with actuator and system faults: Population-based metaheuristic approach

For the Conical Tow-Tank Non-Interacting Level (CTTNL) prototype system, this article discusses the design of an unique optimal fractional order TID controller employing a type-1 fuzzy set. To generate a linearized model transfer function for the nonlinear CTTNL process, local linearization around the equilibrium state was performed. This work compares the performance of a fuzzy tilted-integral-derivative (FTID) controller for the CTTNL system to a traditional proportional–integral–derivative (PID) controller. The parameters of the FTID controller were optimized using the Chicken Search Optimization (CSO) algorithm in this study, and those values were used to create a PID controller. Thereafter, the FTID and PID controllers’ performance is compared. The investigation shows that the FTID controller beats the PID controller in terms of IAE, ISE, ITAE, and ITSE integral errors. The suggested controller’s fault-tolerant performance was also assessed using the fault recovery time (Frt) parameter. The FTID controller outperforms traditional PID controllers in terms of transient and steady-state performance. The fault tolerance capabilities of the FTID controller will be tested on the CTTNL system in the future, using additive and multiplicative failures. Further research will include a comprehensive examination of robustness in the context of model parameter uncertainties.

Flux Reversal Permanent Magnet Machines With Single-Layer Non-Overlapping Windings

Single-layer (SL) non-overlapping windings are applied to flux reversal permanent magnet (FPRM) machines, to extend the family of stator-PM machines. The machine topology and operating principle are introduced, and the general rules of symmetrical phase flux-linkages in machines with various slot/pole number combinations are found. The even order coil flux-linkage harmonics can be cancelled in the resultant phase waveforms due to opposite polarities of either magnets or coils. Moreover, based on finite element (FE) analysis, the FRPM machines with different rotor pole numbers, equipped with SL or double-layer (DL) windings, are comprehensively compared. The results reveal that compared to their DL counterparts, the FRPM machines with SL windings (FRPM-SL) exhibit similar torques and iron losses, as well as enhanced flux-weakening and fault-tolerant capabilities due to higher self-inductances but lower mutual-inductances. A pair of FRPM-SL prototype machines are manufactured and tested to validate the predictions.

Design and Analysis of a Five-phase Flux-Intensifying Fault-Tolerant Permanent-Magnet Motor With Active Sensorless Strategy Under Multimode Operation

In this paper, a new flux-intensifying fault-tolerant permanent magnet synchronous motor (FI-FTPMSM) is proposed to improve sensorless operating capacity under multimode operation including fault conditions. Most previous studies regarding fault-tolerant motors aim to improve fault-tolerant capability but suffer the saliency characteristic problem, which is unfavorable for sensorless control. In this study, an active sensorless strategy is developed by considering the sensorless operating capability under multimode operation in the motor design stage. Based on this novel idea, a new FI-FTPMSM with a high inverse saliency ratio is designed. By carefully choosing slot-pole combination, subtly setting <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis magnetic barrier shape, and improving air gap waveform, the superior inverse saliency characteristic is obtained, which effectively improves the dynamic and steady-state sensorless operating performance. Through simulation analysis and experimental tests, the rationality and validity of the proposed strategy are verified.

Disturbance Observer-Enhanced Adaptive Fault-Tolerant Control of a Quadrotor UAV against Actuator Faults and Disturbances

For a quadrotor unmanned aerial vehicle (UAV), this paper proposes an adaptive sliding mode control (SMC) strategy enhanced with a disturbance observer to attain precise trajectory and attitude tracking performance while compensating for the detrimental impacts of actuator faults and disturbances. First, an adaptive SMC strategy that utilizes an integral sliding surface is presented to enhance the fault-tolerance capabilities of the studied quadrotor UAV against actuator faults. In addition, a disturbance observer is further created to compensate for the disturbances. By integrating the proposed adaptive SMC strategy with the designed disturbance observer, both actuator faults and disturbances can be effectively accommodated. It was theoretically demonstrated that the system is stable while using the proposed adaptive fault-tolerant control strategy. The effectiveness and benefits of the proposed strategy is verified with comparative simulation results under different faulty scenarios.

Spacecraft Attitude Stabilization Control with Fault-Tolerant Capability via a Mixed Learning Algorithm

The issue of active attitude fault-tolerant stabilization control for spacecrafts subject to actuator faults, inertia uncertainty, and external disturbances is investigated in this paper. To robustly and accurately reconstruct actuator faults, a novel mixed learning observer (MLO) is explored by combining the iterative learning algorithm and the repetitive learning algorithm. Moreover, to guarantee robust spacecraft attitude fault-tolerant stabilization, by synthesizing the mixed learning algorithm with the sliding mode controller, a novel mixed learning sliding-mode controller (MLSMC) is designed based on the separation principle, in which the mixed learning algorithm is used to update composite disturbances online, including fault errors, inertia uncertainty, and external disturbances. Finally, a numerical example is provided to demonstrate the effectiveness and superiority of our proposed spacecraft attitude fault-tolerant stabilization control approach.

A Novel Conditional Connectivity and Hamiltonian Connectivity of BCube with Various Faulty Elements

BCube is one of the main data center networks because it has many attractive features. In practical applications, the failure of components or physical connections is inevitable. In data center networks in particular, switch failures are unavoidable. Fault-tolerance capability is one main aspect to measure the performance of data center networks. Connectivity, fault tolerance Hamiltonian connectivity, and fault tolerance Hamiltonicity are important parameters that assess the fault tolerance of networks. In general, the distribution of fault elements is scattered, and it is necessary to consider the distribution of fault elements in different dimensions. We research the fault tolerance of BCube when considering faulty switches and faulty links/edges that distribute in different dimensions. We also investigate the connectivity, fault tolerance Hamiltonian connectivity, and Hamiltonicity. This study better evaluates the fault-tolerant performance of data center networks.

Design and Analysis of an Intelligent Fire Detection System For Cargo Compartment of Aircraft

The fire detection system and fire warning are design features of an aircraft. The fire detection system protects the aircraft and passengers in case of actual fire during flight. But spurious fire warning during flight creates a panic situation in flight crews and passengers. The conventional fire alarm system of an aircraft is triggered by false signal. The artificial neural network has capability of fault tolerance and robust in nature. Its performance is dependent on its training, which is done on the real time data collected from the aircraft. Neural network based fire detection system provides real time surveillance, monitoring and automatic alarm. An intelligent fire detection system is developed based on artificial neural network in MATLAB using three inputs such as temperature, smoke density and CO concentration. This information helps in determining the probability of three representative of fire condition which is Fire, smoke and No fire. The simulated test results show that the identification error rates are very less. This greatly reduces leak check rates and false alarms. The neural network based fire detection system uses a variety of sensor data and improves the ability of system to adapt and accurately predict fires. It sends early alarm when the fire/smoke occurs and helps to reduce the spurious fire warning.

Predictive Control of Modular Multilevel Converters: Adaptive Hybrid Framework for Circulating Current and Capacitor Voltage Fluctuation Suppression

Modular multilevel converters (MMCs) are widely used in voltage-sourced, converter-based high-voltage DC systems due to their modular design, scalability, and fault tolerance capabilities. In MMCs, multi-variable control objectives can be employed by using model predictive control (MPC) due to its fast dynamic response and ease of implementation. Nonetheless, conventional MPC techniques for MMCs have shortcomings, including high computational requirements, poor circulating current, and capacitor voltage fluctuation suppression. First, this study proposes an adaptive MPC technique that adapts the number of candidate combinations to the steady and transient states, significantly reducing the computational burden. Second, an improved hybrid combination of an MPC with a proportional-resonance (PR) controller enhances the circulating current and capacitor voltage fluctuation suppression performance. According to the phase difference between the circulating current and the capacitor voltage, the circulating current and capacitor voltage can be suppressed at different times by changing the circulating current reference of the PR controller. The switching frequency can be reduced by using the PR controller’s output to adjust the input submodule number instead of changing the duty cycle. The proposed techniques were validated by simulations and experimental case studies with a three-phase grid-connected MMC.

An improved fault tolerant single phase five-level multilevel inverter

ABSTRACT Despite the numerous advantages of multilevel inverters over two-level inverter, their main limitation is the increase in component count as the level increases. The increase in component count and high failure rate of power semiconductor switches and capacitors tend to reduce the reliability of multilevel inverters. Thus, the ability of multilevel inverter to tolerate faults is an important factor to consider when choosing a multilevel inverter topology for safety-critical applications. In this regard, the current study presents a new single-source five-level fault-tolerant inverter based on switched capacitor with self-balancing capability. In the proposed inverter, the fault tolerance is achieved with the help of redundant legs. A simple fault reconfiguration strategy is proposed in the present study for the proposed inverter which can retain the number of levels in the output, power handling capacity and self-balancing of switched capacitor in the event of any single switch fault and the most of multi-switch fault scenarios. The simulation study and experimental results validate the suggested inverter’s fault tolerant capability under various fault scenarios. A comprehensive and detailed comparison study demonstrates the proposed fault resilient inverter’s superiority over the recently proposed fault tolerant multilevel inverter available in the literature.

Fault-tolerant capability of MMC with novel structure of middle submodules

Fault-tolerant capability of MMC with novel structure of middle submodules

Open-Winding Permanent Magnet Synchronous Generator for Renewable Energy—A Review

The open-winding permanent magnet synchronous machines (OW-PMSMs) have recently been gaining more attention because of their fault-tolerant capability and power quality comparable to a 3-level converter-driven system. This paper reviews the common configurations of OW-PMSM when used as a generator, highlighting its shortcomings and benefits. The OW-PMSM with a common DC bus was found to be a promising direct-drive generator solution for wind energy conversion (WEC) systems considering fault tolerance, DC bus utilization, and power quality when appropriate control algorithms are in place. The presence of the zero-sequence current is the key disadvantage of the common DC bus configuration. The review highlights the algorithms that have been proposed to suppress the zero-sequence current of the OW-PMSM under healthy and various fault conditions, especially the open-circuit fault of semiconductor switch. Shutting down remotely located wind turbines because of faults, until they can be repaired, may not make economic sense. The OW-PMSM can offer the opportunity, to run a WEC system even under fault conditions albeit with low output power. This paper will assess the literature gaps in the existing control techniques that prevent the extension via a comprehensive review.