This paper presents generalized logic-based methods for intelligent fault diagnosis in power electronic converters based on correlation between faults and basic measurements. Fault recovery is then applied based on this correlation by using necessary signals and quantities from existing measurements. The main purpose of the proposed fault diagnosis methods is for power electronic systems to survive from fault conditions that could occur in various components, to cope with the notion of a smart grid and extend their lifetime. The proposed methods are online, i.e. real-time or near-real-time, and can be applied to any power electronic system. Existing intelligent control of power electronic systems along with various short- and open-circuit faults in major power electronic components are reviewed. Two methods are established to diagnose faults and engage redundancy for fault recovery with one method using combinational logic and another using fuzzy logic. In both methods, two quantities are observed for each of the measured signals: 1) the signal’s average value and 2) the signal’s RMS value. Total harmonic distortion (THD) is also used in some simulations but is not required in experimental implementation. A systematic methodology to reduce the number of measured quantities while maintaining effective diagnosis is introduced. A solar PV micro-inverter in stand-alone mode is used as an example testing platform for the proposed methods. A simulation model is experimentally validated and the effect of each fault on different voltage and current measurements are observed, then both methods are tested in simulation and hardware. Results show the ability of both methods to diagnose several faults in the inverter’s power stage along with their ability to engage redundancy for fault recovery.

This paper $^1$ proposes an unsupervised learning approach for fault prognosis of Silicon Carbide (SiC) MOSFETs. The proposed approach utilizes the changing trend of a device's voltage, current, temperature and other device characteristics with its degradation. The failure modes of semiconductors are reviewed along with existing methods for fault prognosis. The proposed approach is the first to address prognostics of SiC devices, and it can avoid the effects from system noise and data errors. It is not limited to offline analysis and is targeted at online implementation. It is easy to implement on standard digital platforms, and has fast computational speed. Offline data analysis is performed to verify the effectiveness of the proposed method, and a processor-in-the-loop system is used to verify its ability to perform online fault prognosis.

Since the introduction of mica paper and synthetic resin-based taping insulation for rotating-machines in 1950s, only evolutional improvements in their properties and processing have been made. Due to its challenging nature, much of recent insulation research has been focused on the aspect of reliability rather than performance enhancement. This paper presents the development and performance evaluation of a revolutionary nanostructured insulation in the manufacturing of large propulsion motors with game-changing torque density and payload efficiency for marine Next Generation Integrated Power System. It is demonstrated that nanostructured insulation based on 2D-platelet fillers could offer significant improvement over conventional insulation system in electrical, dielectric, thermal and mechanical properties. Optimal nanostructured insulation formation identified through a Design of Experiment study exhibits high thermal conductivity of $>0.8$ W/( $\text{m}\cdot \text{K}$ ), high breakdown strength of >40 kV/mm, low dielectric constant of less than 5.5 and low dielectric loss factor of less than 2.5% at 155°C. Voltage endurance tests on coupons with optimal formulation, in accordance with IEC 60343 standard, demonstrate satisfactory endurance life. Furthermore, a multi-physics finite-element-analysis model of the winding in a medium-voltage electric motor is established to perform electromagnetic and thermal analyses in ANSYS under various temperature boundary conditions. The study indicates a remarkable increase of 14% in torque handling capacity of a motor wound with proposed nanostructured insulation material when compared to an identical motor wound with conventional micaceous insulation.

This article proposes a model-based voltage quality analysis and optimization method for post-fault reconfigured N-level Neutral Point Clamped (NPC) inverter. It is found that the voltage quality of post-fault reconfigured multilevel inverters (MLIs) has significant degradation which could cause issues in critical applications. To analyze and solve the voltage quality problem, existing voltage quality and mathematical analyses of MLIs were reviewed. Significant limitations of existing voltage quality analysis methods and shortages of existing mathematical analysis were found. Thus, a suitable mathematical model of N-level NPC inverter is proposed in this article to accurately describe voltage quality of a reconfigured N-level NPC inverter. The mathematical model is validated by simulation and experimental results and used for voltage quality analysis. In addition, based on the accurate mathematical model and results of voltage quality analysis, an optimization method is proposed to alleviate the voltage quality degradation of post-fault reconfigured N-level NPC inverter. A five-level NPC inverter and a reconfiguration method were used as an example to illustrate the proposed optimization method. Experimental and simulation results validate the effectiveness of the proposed optimization method.

In this paper, power loss and cost models of power electronic converters based on converter ratings and datasheet information are presented. These models aid in creating rapid prototypes which facilitate the component selection process. Through rapid prototyping, users can estimate power loss and cost which are essential in design decisions. The proposed approach treats main power electronic components of a converter as building blocks that can be arranged to obtain multiple topologies to facilitate rapid prototyping. In order to get system-level power loss and cost models, two processes are implemented. The first process automatically provides minimum power loss or cost estimates and identifies components for specific applications and ratings; the second process estimates power losses and costs of each component of interest as well as the whole system. Two examples are used to illustrate the proposed approaches—boost and buck converters in continuous conduction mode. Achieved cost and loss estimates are over 93% accurate when compared to measured losses and real cost data. This research presents derivations of the proposed models, experimental validation of the models and demonstration of a user friendly interface that integrates all the models. Tools presented in this paper are expected to be very useful for practicing engineers, designers, and researchers, and are flexible and adaptable with changing or new technologies and varying component prices.

Large voltage transients due to power electronic inverters are one of the major factors influencing the insulation lifetime. This paper studies the effect of square voltage transients and switching frequency on insulation breakdown time based on series of voltage endurance tests. A medium-voltage power-electronics inverter testbed is built to stress Polyimide films Kapton HN with square waveforms at different frequencies. The voltage endurance test data is used to develop behavioral aging models and identify the effect of voltage transients and switching frequencies on insulation breakdown time. Results show a new correlation between switching frequency, insulation thickness, and voltage stress that have not been covered in the literature before.