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This article evaluates the electromagnetic interference (EMI) caused by active neutral point clamped (ANPC) phase leg undergoing zero voltage switching (ZVS). ZVS, together with a high fundamental frequency operation is encountered in dual active bridge (DAB) converters. This allows ANPC phase leg to be operated in a different manner than its inverter counterpart. A comprehensive evaluation of four switching schemes for NPC/ANPC-DAB with regard to their EMI performance, voltage overshoot, and losses have been done. Switching state redundancies have been used to reduce the EMI of the ANPC phase leg. To further help in reduction of high frequency EMI and voltage overshoot, a low inductance busbar design has been presented for through-hole discrete devices. Finite element simulation and measurement results show a busbar inductance of 7.7 nH for long commutation loops. Finally, EMI performance (conducted and radiated) together with the busbar design has been experimentally validated for two of the most useful switching schemes. The switching schemes and the busbar design can boost adoption of NPC/ANPC-DAB by ensuring EMI compliance and improved efficiency without affecting the normal DAB operation or using additional hardware. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on current loop auto-tuning for self-commissioning of sensorless interior permanent magnet synchronous machine (IPMSM) drives. Well-tuned current controllers are essential for both high-performance operation and self-commissioning procedure. However, current controller design parameters, i.e., $L_{d}$ and $L_{q}$ , are not known at the beginning of the self-commissioning procedure where their estimation also has unique challenges. For example, an initial rotor position to determine the actual d- and q-axes is not known. Also, feedback controllers cannot be used in the estimation because they are not tuned yet. As a solution, this paper proposes a method to estimate the spatial inductance map by spatially scanning the motor via sinusoidal voltage injection in a controlled manner. Then it uses the estimated inductance values to tune the current controllers. The proposed method identifies $L_{d}$ and $L_{q}$ values using open-loop voltage injection without needing actual d- and q-axis positions. The whole procedure takes around a second. Practical considerations such as an automatic selection of the injection voltage, and digital control and dead-time effects are carefully addressed. The findings are experimentally verified on a 3-phase IPMSM drive. Furthermore, its applicability to different motor types is also demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents a practical procedure regarding inertia estimation and speed loop auto-tuning for sensorless interior permanent-magnet synchronous motor (IPMSM) drives. In many applications, well-tuned speed controller is essential to enable dynamic and stable drive operations. However, high-performance speed controller design requires system parameters such as inertia which are unknown at the beginning of drive commissioning. Manual trial-and-error tuning is unattractive due to its blind, lengthy, non-optimal, and potentially unsafe nature. On the other hand, model-based tuning through inertia estimation has unique challenges at this step of self-commissioning. Determining the test torque for a safe and reasonably short test in inertia estimation is a real practical problem because the total inertia can be in wide range in different mechanical systems. Furthermore, feedback controllers are not usable to automatically determine the test torque due to unknown motor parameters. As a solution, this paper proposes an automated test torque selection procedure. Then it identifies the inertia and lastly tunes the speed controller using the identified parameter. Overall, a fully automated speed-loop auto-tuning method is proposed which aims minimal operator involvement. The findings are experimentally verified on an IPMSM drive. In addition, the proposed method can easily be extended to different motor types and sensored or sensorless vector control strategies. [ABSTRACT FROM AUTHOR]

This paper presents a new least-mean-square (LMS) algorithm based deadtime compensation method to suppress the current distortion in permanent-magnet synchronous motor (PMSM) field-oriented control (FOC) drives. Compared to conventional average value compensations, the proposed method is robust to switching device parameter variations thanks to the online adaptation capability of the LMS algorithm. Similarly, the disturbance observer compensators are also immune to switching device parameter variations; however, varying motor parameters degrade their compensation performance. Without prior knowledge of switching device or motor parameters, the proposed method can directly reduce the deadtime current harmonics by generating compensation voltage references. In addition, the proposed method is easy to implement since it does not require voltage errors estimation or current harmonics extraction, which are necessary for disturbance observer and adaptive filter based methods. The proposed method is tested on a 2.5-kW voltage-source inverter PMSM drive controlled by an FOC algorithm. Its effectiveness is validated by both experimental results and spectrum analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a new dead-time compensation method for voltage-source inverters (VSIs) used in permanent-magnet synchronous motor (PMSM) drives. The proposed technique is developed based on the revised repetitive controller (RRC) to reduce current harmonics and distortion, which is essential to improve efficiency, rotor position observer performance at very low speed, and self-commissioning accuracy. This method significantly suppresses the sixth-order harmonics and its multiples in synchronous reference frame and reduces the current total harmonic distortion (THD) without depending on the precise current sampling especially in the zero-crossing region. Unlike in most average value theory or pulse based compensations, it does not require additional hardware. It is also shown that RRC-based compensation has better robustness against motor parameter variations than disturbance observer based methods and requires very low computational effort. Compared to other repetitive controllers (RC), the proposed RRC is dedicated for dead-time compensation and can easily be integrated because of its simpler structure. In addition, it can be conveniently activated or deactivated on the fly, which adds more flexibility to the control overall algorithm. The effectiveness of the proposed method is validated by theoretical analysis, spectrum analysis, as well as simulation and experimental results. [ABSTRACT FROM PUBLISHER]

The research on noninvasive incipient fault diagnosis of power converters is very critical to avoid strenuous periodic checkups and costly interruptions. In many of the research studies, on-state resistance of power MOSFETs is identified as the fault precursor, and suggested to be monitored online for prognosis. In this paper, a condition monitoring algorithm is proposed for power MOSFETs of interleaved converters and integrated with the conventional current loops. The proposed technique utilizes on-state resistance information of the switches to adjust the current reference of each interleaving leg. In addition, a pulse-width adjustment method is proposed to avoid one current sensor and current-control loop. With the proposed scheme, the thermal stress on the aged device can be reduced, and the overall lifetime of the converter can be extended. The proposed approach is verified on two-leg interleaved converters both in simulation and experimentally. [ABSTRACT FROM AUTHOR]

This paper proposes a new vector-based dead-time compensation method for three-level T-type converters. The origins and effects of the dead-time voltage errors are analyzed in detail for different switching commutations and load conditions. In order to eliminate the dead-time distortion in each phase, a dead-time error voltage vector is introduced to adjust the reference voltage vector depending on load current polarity. The proposed vector-based dead-time compensation scheme has several advantages. First, it can be applied to multilevel converters with any number of voltage levels using any modulation schemes. Second, the pulse loss issue which is common in conventional pulse-based compensation strategies can be eliminated. In addition, the pulse saturation can be mitigated by operating the converters in overmodulation regions. All of these advantages and effectiveness of the proposed vector-based dead-time compensation method are verified through both simulation and experimental studies. [ABSTRACT FROM AUTHOR]

In this article, online short-circuit estimation of permanent magnet synchronous motors (PMSMs) are presented, which is essential for postfault ac drive operations. For this purpose, initially, the PMSM model with interturn short-circuit fault (ITSC) is extended to cover motors with saliency. By utilizing ITSC model voltage equations and voltage reference equations, the amplitude and phase relationship between short-circuit current and the phase reference voltage is established. In the next step, second harmonics in the reference voltage and feedback current are used to extract the short-circuit current information. In order to efficiently use ac drive microcontroller bandwidth, the proposed short-circuit current estimation method is executed after the ITSC fault is detected, not continuously. Instead of running the proposed short-circuit current estimation continuously, it is reasonable to run it after an ITSC fault detection to efficiently use ac drive microcontroller bandwidth. Therefore, two intermediate steps, a simple ITSC fault detection and severity estimation algorithms are proposed as well. The proposed technique can estimate the fault current and severity without the knowledge of fault location and valid for all PM motors. The findings are experimentally tested using two PMSMs to demonstrate the effectiveness and practicability of the proposed estimation technique. [ABSTRACT FROM AUTHOR]

This paper presents the analysis of a performance-oriented electric motors diagnostics in modern energy conversion system. With increased demand for electrical energy in world industries, the population of energy conversion devices such as generators/motors has greatly increased. As emerging and not being a mature enough technology in the application of renewable energy conversion or electric-drive transportation, the protection and diagnosis of electric motors have been extensively studied for safety and reliability. Meanwhile, motor phase currents commonly involve random noise components generated by harsh energy system environments, low- and high-order harmonics interferences caused by power inverters and fast switching devices, and various other design imperfections. Therefore, it is quite challenging to model the overall noise content and eliminate the disturbance while detecting motor fault signatures. Due to the inherent random variation of motor noise statistics, the noise model and elimination strategy should also be adaptively updated according to instantaneous noise conditions through which detection can be done with predefined performance expectation. Several successful solutions in the literature have managed to perform a diagnosis under certain noise conditions; however, a detailed performance and adaptability analysis covering arbitrary noise variation has not been satisfactorily addressed. This paper mainly deals with performance oriented threshold design strategies for fault signature detection utilizing the noise statistics of the motor phase current signal. The proposed solution is generalized to cover arbitrary Gaussian noise variations and derive the optimal form of the threshold that satisfies user's prior detection quality expectations. The mathematical derivations are proved through statistical theory and the experimental verifications are performed by using a 3-hp motor setup. [ABSTRACT FROM PUBLISHER]

The reference frame theory constitutes an essential aspect of electric machine analysis and control. In this study, apart from the conventional applications, it is reported that the reference frame theory approach can successfully be applied to real-time fault diagnosis of electric machinery systems as a powerful toolbox to find the magnitude and phase quantities of fault signatures with good precision as well. The basic idea is to convert the associated fault signature to a dc quantity, followed by the computation of the signal's average in the fault reference frame to filter out the rest of the signal harmonics, i.e., its ac components. As a natural consequence of this, neither a notch filter nor a low-pass filter is required to eliminate fundamental component or noise content. Since the incipient fault mechanisms have been studied for a long time, the motor fault signature frequencies and fault models are very well-known. Therefore, ignoring all other components, the proposed method focuses only on certain fault signatures in the current spectrum depending on the examined motor fault. Broken rotor bar and eccentricity faults are experimentally tested online using a TMS320F2812 digital signal processor (DSP) to prove the effectiveness of the proposed method. In this application, only the readily available drive hardware is used without employing additional components such as analog filters, signal conditioning board, external sensors, etc. As the motor drive processing unit, the DSP is utilized both for motor control and fault detection purposes, providing instantaneous fault information. The proposed algorithm processes the measured data in real time to avoid buffering and large-size memory needed in order to enhance the practicability of this method. Due to the short-time convergence capability of the algorithm, the fault status is updated in each second. The immunity of the algorithm against non-ideal cases such as measurement offset errors and phase unbalance is theoretically and experimentally verified. Being a model-independent fault analyzer, this method can be applied to all multiphase and single-phase motors. [ABSTRACT FROM AUTHOR]

In this paper, a complete cross-correlation-based fault-diagnostic method is proposed for real-time digital-signal-processor (DSP) applications that cover both the fault-monitoring and decision-making stages. In practice, a motor driven by an inverter or utility line is run at various operating points where the frequency, amplitude, and phase of the fault signatures vary unexpectedly. These changes are considered to be one of the common factors that yield erroneous fault tracking and unstable fault detection. In this paper, the proposed algorithms deal with the ambiguities of line-current noise or sensor-resolution errors and operating-point-dependent threshold issues. It is theoretically and experimentally verified that a motor fault can be continuously tracked when the sensor errors are within a limited range through the adaptively determined threshold definition of noise conditions. The offline experiments are performed via Matlab using actual line-current data obtained by a data-acquisition system. These results are verified on a DSP-based motor drive in real time where drive sensors and a digital signal processor are employed both for motor-control and fault-diagnostic purposes. [ABSTRACT FROM AUTHOR]

The integrity of electric motors in work and passenger vehicles can best be maintained by frequently monitoring its condition. In this paper, a signal processing-based motor fault diagnosis scheme is presented in detail. The practicability and reliability of the proposed algorithm are tested on rotor asymmetry detection at zero speed, i.e., at startup and idle modes in the case of a vehicle. Regular rotor asymmetry tests are done when the motor is running at a certain speed under load with stationary current signal assumption. It is quite challenging to obtain these regular test conditions for long-enough periods of time during daily vehicle operations. In addition, automobile vibrations cause nonuniform air-gap motor operation, which directly affects the inductances of electric motors and results in a noisy current spectrum. Therefore, it is challenging to apply conventional rotor fault-detection methods while examining the condition of electric motors as part of the hybrid electric vehicle (HEV) powertrain. The proposed method overcomes the aforementioned problems by simply testing the rotor asymmetry at zero speed. This test can be achieved at startup or repeated during idle modes where the speed of the vehicle is zero. The proposed method can be implemented at no cost using the readily available electric motor inverter sensors and microprocessing unit. Induction motor fault signatures are experimentally tested online by employing the drive-embedded master processor (TMS320F2812 DSP) to prove the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a digital signal processor-based phase-sensitive motor fault signature detection technique is presented. The implemented method has a powerful line current noise suppression capability while detecting the fault signatures. Because the line current of inverter-driven motors involve low-order harmonics, high-frequency switching disturbances, and the noise generated by harsh industrial environment, the real-time fault analyses yield erroneous or fluctuating fault signatures. This situation becomes a significant problem when the signal-to-noise ratio of the fault signature is quite low. It is theoretically and experimentally shown that the proposed method can determine the normalized magnitude and phase information of the fault signatures even in the presence of noise, where the noise amplitude is several times higher than the signal itself. Since it has low computational burden, the developed algorithm is embedded to the motor control program without degrading drive performance. Therefore, it is implemented without any additional cost using readily available drive processor and current sensors. [ABSTRACT FROM AUTHOR]

In this paper, the effects of inverter harmonics on motor current fault signatures are studied in detail. It is theoretically and experimentally shown that the fault signatures caused by the inverter harmonics are similar and comparable to those generated by the fundamental harmonic on the line current. Theoretically-derived extended relations including bearing fault, eccentricity, and broken rotor bar relations are found to match experimental results. Furthermore, it is observed and reported that the asymmetries on the rotor caused by broken rotor bars increase the amplitude of even harmonics. To confirm these claims, bearing, eccentricity, and broken rotor bar faults are tested and the line current spectrum of each faulty motor is compared with the healthy one. The proposed additional fault data are expected to contribute positively to the inverter-fed motor fault decision-making algorithms. [ABSTRACT FROM AUTHOR]

As one of the most promising techniques, magnetic flux-based condition monitoring of electrical machines, has gained significant traction in the past decade. One of the key enabling factor is the advancements in sensor technologies to measure both the airgap magnetic flux and stray magnetic flux around the motors with high accuracy. This study presents a comprehensive review of advances in flux sensors and the recent trends in magnetic flux-based diagnostic techniques for various faults and electrical machines. In this context, various magnetic sensor technologies suitable for measuring both the airgap flux and the stray magnetic flux are introduced. Each of the sensor technologies are discussed exhaustively, including their working principles and applications in electrical machine fault diagnostics. In the following sections, various flux-based diagnostic techniques are discussed for different types of common faults in various ac machines. Finally, the future trends are discussed briefly under the light of several applications and their impact. [ABSTRACT FROM AUTHOR]

This article presents an active neutral point clamped (ANPC)-based parallel dual-active bridge (DAB) architecture which combines dv/dt cancellation and power sharing in order to reduce electromagnetic interference (EMI) caused by common-mode (CM) current. High dv/dt associated with wide bandgap devices causes high CM current mainly due to parasitic capacitances. The corresponding conducted EMI can remarkably reduce the reliability of power converters and other onboard systems. This issue becomes worse due to higher dc bus voltage trend in electric vehicles (EV) and other dc systems. Conventional techniques struggle to provide attenuation in a wide frequency range. The problem can also be severe in soft-switched DAB converters as they operate at relatively higher frequencies. In this article, initially, an in-depth theoretical analysis is provided to understand the complimentary dv/dt events. Various factors causing nonideal dv/dt cancellation are discussed in detail together with possible solutions. Detailed experimental results are obtained from a 1100 V–150 V parallel DAB system including both the high and low voltage sides at different dv/dt rates. dv/dt cancellation at lowered dv/dt rates facilitated by power sharing and small snubbers provide up to 25 dBuA reduction in CM conducted EMI. A comparison with CM chokes is also presented to validate improved attenuation in a wide frequency range. [ABSTRACT FROM AUTHOR]

The temperature-sensitive electrical parameters (TSEPs) have been used in silicon carbide (SiC) mosfets junction temperature measurement for over-temperature protection and condition monitoring. However, the device aging can affect the TSEPs and thus leads to false ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement. In this article, the aging's impacts on various TSEPs are comprehensively investigated. Specifically, utilizing the dc power cycling test, both the gate oxide instability and package degradation are considered. Then the commercial devices with different structures are aged, and their temperature-dependent static and switching characteristics are evaluated at different aging cycles. Both the positive gate bias-induced threshold voltage shift and package degradation are observed, and their impacts on each TSEP are evaluated independently. Based on the evaluation results at various operating conditions, the temperature measurement errors due to different aging mechanisms are well summarized for each TSEP. From the dc power cycling test result, the package degradation's impact on TSEPs is found to be more significant than the gate oxide instability. It is pointed out that the aging's effect on TSEPs is an important factor that needs to be considered for accurate ${\boldsymbol{T}}_{\boldsymbol{j}}$ measurement in SiC mosfets. [ABSTRACT FROM AUTHOR]

The dynamic on-resistance in gallium nitride (GaN) devices is problematic as it can impair the converter's efficiency due to the increased conduction loss. In this paper, the hard-switching transient's effect on the dynamic on-resistance is, for the first time, evaluated experimentally on a commercial high-voltage GaN high electron mobility transistor. A new ${R_{{\rm{dyn}} - {\rm{ds}},{\rm{on}}}}$ measurement circuit with fast sensing speed is designed, and an accurate measurement of ${R_{{\rm{dyn}} - {\rm{ds}},{\rm{on}}}}$ can be realized experimentally within 49.6 ns after the device's current reaches to the load current. A double-pulse-test setup is designed to comprehensively evaluate the switching transient's effect on ${R_{{\rm{dyn}} - {\rm{ds}},{\rm{on}}}}$ under different operating conditions. From the experimental results, it is found that the turn-on and turn-off gate resistance have a significant impact on the dynamic on-resistance whereas the cross-talk effect on ${R_{{\rm{dyn}} - {\rm{ds}},{\rm{on}}}}$ is negligible. Specifically, at 400 V/25 A, more than 27% (28.2%) increase in ${R_{{\rm{dyn}} - {\rm{ds}},{\rm{on}}}}$ is observed when the external turn-on (turn-off) gate resistance increases from 0 to 20 Ω. Detailed discussion and quantitative analysis are provided to explain the experimental results. In terms of the turn-on process, it is concluded that the ${R_{{\rm{dyn}} - {\rm{ds}},{\rm{on}}}}$ variation is mainly caused by the different numbers of generated hot electrons. For the turn-off transient, it is confirmed the variation of drain current at different dv/dt slew rate leads to the ${R_{{\rm{dyn}} - {\rm{ds}},{\rm{on}}}}$ difference. [ABSTRACT FROM AUTHOR]

This paper presents a novel method to estimate the number of shorted turns in a permanent magnet synchronous machine (PMSM) following the detection of interturn short-circuit (ITSC) fault and its location. In this proposed method, PMSM is excited through a low sinusoidal voltage at standstill condition to obtain the winding resistance and synchronous inductance by current response. It is shown that the ITSC fault introduces variation in the current response, which can be used to calculate the number of shorted turns under zero fault resistance assumption. Using this practical procedure, the fault severity can be estimated directly in a straight-forward manner. In other words, the severity estimation for a given machine can be done without complex machine modeling or experiments on ITSC prototype with multiple taps. The findings in this paper are essential for a comprehensive solution including fault mitigation algorithms and postfault operations. In order to verify the findings, a three-phase equivalent circuit model supported by finite element analysis results is used to take saturation and space harmonics into account. In addition, experimental results are presented to demonstrate the validity and practicability of the severity estimation. [ABSTRACT FROM AUTHOR]

Today, power conversion in automotive industry depends heavily on the reliable operation of insulated-gate bipolar transistors (IGBTs). Condition monitoring of IGBTs and reporting imminent faults to driver dashboard are critical for avoiding any fatal accidents. In this study, first, a comprehensive comparison is carried out between on-state collector–emitter drop ($V_{ce,on}$) with gate threshold voltage (Vth), as two reliable aging precursors. In order to enrich current understanding of IGBT aging prognosis, accelerated aging methods are applied under a wide variety of thermal stresses. Aging mechanisms and physical phenomena responsible for variation in both $V_{ce,on}$ and Vth have been methodically investigated. These explanations are also supported by detailed failure analysis. Based on the extensive result sets for tested samples from different manufacturers with different structural types, it is found that $V_{ce,on}$ show different trends at different stress levels, whereas under the same test conditions Vth provides more consistent and robust state-of-health information. Finally, an example experiment has been performed in which continuous $V_{ce,on}$ measurements coupled with Vth information has been used to provide more insight about the device aging as well as faults in an automobile's sub-systems. [ABSTRACT FROM AUTHOR]

In-circuit frequency response measurement of power converters enables verification of the control loop and periodic measurement during normal operation of the converter. This enables addition of diagnostics and monitoring functions without additional cost. The disturbance injected for frequency response measurement causes output of the converter to be disturbed, which is undesirable during normal converter operation. This paper presents an auto injection control algorithm by which the disturbance amplitude is controlled while maintaining good measurement fidelity. A voltage source inverter is selected as a case study to test the proposed algorithm, in which both current and voltage loop are verified using in-circuit frequency response analysis measurement. [ABSTRACT FROM PUBLISHER]

This paper presents a comprehensive analysis of permanent magnet synchronous machine stator winding impedance variation in inter-turn short-circuit and eccentricity faults. The phase impedances are monitored through an extended self-commissioning procedure at the standstill mode before or after operation, and hence are agnostic to well-known issues caused by transients, load/speed level, or controller coefficient dependency. Moreover, the effect of stator iron core saturation on the electrical parameters is analyzed in depth. In order to distinguish the inter-turn shorts from the eccentricity fault which exhibits similar behaviors, a classification algorithm based on the saturation effect is introduced and analyzed on the machines with different pole-slot combinations. Both two-dimensional finite element analysis simulation and experimental test results are provided to show the efficacy of this analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a study on the topology-dependent magnet defect fault signatures in permanent-magnet motors. A new analytical approach is introduced to characterize the fault signatures in stator back electromotive force (EMF) and current waveforms using magnetic equivalent circuit. Stator winding configuration, winding connection type and location of damaged rotor magnets are some of the physical properties affecting the fault signature characteristics. Several cases with different number of pole and slot are investigated through the proposed method. In addition, different winding connections (including star and delta connection), different winding configurations (including single and double layer, fractional and full coil pitch), and different magnet defect number and location are scrutinized. It is shown that there are some cases exhibiting different fault patterns than the ones obtained through well-known fault models defined in the literature. It is essential to take these discrepancies into account in order to avoid false alarms. In addition, it is observed that some of the fault signatures show up in the stator back EMF spectrum but not in the current spectrum due to location and severity of magnet defect, and design specs. Comparative 2-D finite-element simulations and experimental results justify the theoretical magnet defect fault analysis and show the efficacy of the proposed approach. [ABSTRACT FROM PUBLISHER]

In this paper, a motor specific fault severity assessment method is proposed to calculate the amplitude of magnet defect fault signatures in the stator current and back-electromotive force (EMF) through machine and controller parameters of permanent magnet synchronous motor (PMSM) drive. A detailed mathematical analysis is developed based on the linear model of PMSM to predict the behavior of fault signatures in motor variables at various operating points. In order to understand and decouple the effects of motor controllers and operating points, the derivations are further extended to clarify the effects of current loop gains. Under the light of findings, the fault severity impact on the current and back-EMF fault signatures is investigated exhaustively. For this purpose, the fault intensity imposed to a motor is increased in four steps by removing 25% of one magnet at each step. Throughout each fault level, the changes in the corresponding spectrums are analyzed, which provides an essential information to design accurate threshold to minimize false alarms. The theoretical derivations are validated through comparative finite element analysis (FEA) simulations and experiments. [ABSTRACT FROM PUBLISHER]

This paper deals with the discernment of broken magnet and static eccentricity faults in permanent magnet synchronous motors through the stator phase current. Broken magnet and static eccentricity faults exhibit very similar fault patterns in back-electromotive force (emf) and flux spectrums. Therefore, it is essential to separate these faults from each other for a true diagnosis. In this study, stator emf and phase current waveforms are analyzed in detail to identify the discerning components and characterize their dynamic behaviors. Two-dimensional time-stepping finite-element simulations and experimental results show that the fault classification process can be implemented by using fault-dependent in-phase current fault signatures. [ABSTRACT FROM PUBLISHER]

The research on noninvasive incipient fault diagnosis of power converters is very critical to avoid strenuous periodic check-ups and costly interruptions. Thermal cycling is one of the main techniques to accelerate the package-related failure progress. In this paper, first, a custom designed accelerated aging platform that can expose multiple discrete power MOSFETs to thermal stress simultaneously is introduced. Based on the collected experimental data, the variation of the on-state resistance is identified as the failure precursor, and an exponential degradation model that fits successfully with the experimental data are developed. The remaining useful lifetime (RUL) of degraded power MOSFETs is estimated through classical least-squares algorithm run on experimental data filtered by Kalman Filter which deals with the measurement noise and model uncertainties. The essential advantage of the proposed method is that it does not require junction temperature information. The RUL estimation with limited field data is demonstrated on a number of experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, magnet defect faults and their corresponding reflections on permanent-magnet (PM) motor stator variables are investigated. An analytical approach based on a partitioned magnetic equivalent circuit is developed to determine the influence of magnet defect faults on PM motor variables. Due to the flexibility of the proposed method, the effect of each rotor magnets on each stator coil can be calculated to obtain the induced back electromotove force under faulty cases and observe the fault-related signatures in the frequency spectrum. The proposed tool significantly reduces the computational burden and provides sufficient accuracy, which significantly eases to simulate several magnet fault scenarios and examine detailed topology dependence relations in shorter time. Different cases, including various numbers and locations of defected magnets, winding configurations, and crack direction effects, are studied to understand the magnet defect influences comprehensively. The experiments and simulations are carried out at different speeds and load conditions to fully characterize the fault signatures. Comparative 2-D finite-element simulations and experimental results justify the theoretical magnet defect fault analysis and show the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a new space vector pulsewidth modulation scheme to reconstruct phase currents using neutral-point current sensing in three-level T-type converters (TLTTCs). For this purpose, zero vector and offset vectors are replaced with complementary active vectors. These active vectors do not affect the resultant output voltage and the voltage balance at the neutral point of TLTTCs. Hence, the pulsewidths of corresponding active vectors can be adjusted even at low speeds without much additional switching losses and low-frequency noise in the inverter. The modified switching patterns can easily be generated without significant computational complexity. The proposed method is experimentally verified using Texas Instruments TMS320F28335 and Spartan 6 controllers, on a custom designed T-type converter based on Fuji IGBT modules. [ABSTRACT FROM PUBLISHER]

Power electronics solutions based on multiple converter configurations offer cost-effective solutions by integrating a number of components at input or output power stages. This paper proposes a new multiinput isolated three-level converter for renewable and sustainable energy systems adopting high dc link voltage. Multiple dc sources are integrated to the three-level dc/dc converter before the isolation stage, resulting in reduced part-count, determining dc link voltage level and allowing flexibility in transformer design. The proposed architecture eliminates two boost switches which are present in the two-stage counterpart. The input inductors are operated in discontinuous conduction mode; thus, power can be shared between input sources through proper selection of input inductors. A low voltage prototype has been designed to serve as a proof of concept. [ABSTRACT FROM PUBLISHER]

This article evaluates silicon carbide (SiC) mosfet’s reliability and ruggedness comprehensively between two widely employed device package types: common source and Kelvin source. Multiple accelerated lifetime tests are conducted to comprehensively investigate SiC mosfet’s reliability at both package and die levels. Specifically, a conventional high electric field test is applied to induce gate oxide degradation, whereas package degradation is investigated by the widely adopted power cycling test. To mimic gate oxide degradation patterns closer to realistic cases, an active channel gate bias test is proposed in this study, and a fair comparison is made regarding the device's degradation pattern in the conventional high electric field test. Throughout accelerated lifetime tests, devices’ electrical parameters, consumable lifetime, and end-of-life failure modes are comprehensively evaluated. For ruggedness comparison, a single-shot short-circuit test is conducted on both common-source and Kelvin-source packaged devices with the same die technique and configuration. Other than analytical discussions with experimental waveforms, failure analysis is also conducted to investigate the device's failure mode and root cause. In respect of experimental results in accelerated lifetime tests and short-circuit tests, the existence of the common-source inductance and resistance may mitigate the electrothermal stress applied on the chip with lower gate–source voltage under load current and results in mitigated device instability and longer consumable lifetime. [ABSTRACT FROM AUTHOR]

Multilevel converters have been well studied for high-voltage high-power renewable energy applications. Owing to the multibranch structure, these converters can be operated under fault conditions in case of a loss of a branch or voltage cell. In this regard, this paper proposes a new active fault-tolerant space vector pulsewidth modulation strategy for single-phase faults in three-phase multilevel converters. The proposed modulation strategy treats the multilevel converter as a two-level converter by introducing an offset vector. A generalized approach is proposed to search for the offset vector and to adjust the modulation of the converter online under different fault operation conditions. Several short- and open-circuit faults have been demonstrated on a seven-level hybrid input-switched converter to prove the effectiveness of the proposed fault-tolerant scheme. [ABSTRACT FROM PUBLISHER]

For low-cost isolated ac/dc power converters adopting high-voltage dc-link, research efforts focus on single-stage multilevel topologies. This paper proposes a new single-stage three-level isolated ac/dc PFC converter for high dc-link voltage low-power applications, achieved through an effective integration of ac/dc and dc/dc stages, where all of the switches are shared between two operations. With the proposed converter and switching scheme, input current shaping and output voltage regulation can be achieved simultaneously without introducing additional switches or switching actions. In addition, the middle two switches are turned on under zero current in discontinuous conduction mode operation, and the upper and bottom switches are turned on under zero voltage. Due to the flexible dc-link voltage structure, high power factor can be achieved at high line voltage. A 500 W/48 V prototype is designed to serve as the proof of concept, which exhibits 90.8% peak efficiency at low input line voltage. [ABSTRACT FROM AUTHOR]

Negative rail current sensing with the conventional space vector pulsewidth modulation (SVPWM) scheme imposes several challenges, particularly at low speeds and sector boundaries, where the pulsewidths of active vectors become narrow while the dc negative rail current becomes zero in null vectors (111) or (000). This paper presents a new SVPWM scheme by replacing null vectors with complementary active vectors such that the added vectors effectively cancel out each other, and the applied resultant voltage remains the same as in the conventional SVPWM. Hence, the pulsewidths of active vectors can be increased at low speeds without introducing additional switching losses, adding switching complexity, or introducing low frequency noise to the waveforms. Moreover, the proposed scheme reduces the system error caused by the deadtime of the switches with enlarged pulsewidths, enabling low-speed drive. The proposed technique is experimentally verified using a TMS320F28035 (Piccolo) microcontroller. [ABSTRACT FROM PUBLISHER]

Load variation along with static and dynamic eccentricities degrees is one of the major factors directly affecting the dynamic behaviors of eccentricity signatures as observed in the current spectrum of induction motors. Without taking the effect of load variation into consideration precisely, the change in the static and dynamic related fault signature amplitudes provides misleading information where the eccentricity degree and the load level exhibit similar effects in the current spectrum. In this paper, we address all these factors in a unified framework by analyzing various combinations both theoretically and experimentally. For this purpose, the time-stepping finite element method (TSFEM)-based, load-level-independent method is proposed to determine the static and dynamic eccentricities degrees individually. [ABSTRACT FROM AUTHOR]

In a three-phase squirrel-cage induction motor, eccentricity is a common fault that can make it necessary to remove the motor from the production line. However, because the motor may be inaccessible, diagnosing the fault is not easy. We have developed a time-stepping finite-element method (FEM) that identifies mixed eccentricity (a combination of static and dynamic) by analysis, without direct access to the motor. The method overcomes the difficulty of applying FEMs to transient behavior. It simulates the spectrum of the line current of a production-line motor and compares it to the spectrum of a known healthy motor to detect eccentricity. Agreement between the simulation and actual measurements of eccentricity is good. [ABSTRACT FROM AUTHOR]

Gate-oxide degradation has been one of the major reliability challenges of SiC MOSFETs and should be monitored carefully to avoid unexpected power converter failures. Various precursors have been introduced in the literature for gate-oxide degradation monitoring. However, those proposed precursors are temperature dependent and it is highly challenging to eliminate temperature effects. In this article, two new temperature-independent precursors (Miller capacitance and gate–source capacitance changes) are proposed for gate-oxide degradation monitoring of SiC MOSFETs. During the accelerated aging tests under high electric field and high temperature, a consistent change in Miller capacitance and gate–source capacitance is reported for both common source and Kelvin source SiC MOSFETs. Also, the temperature sensitivity of each precursor is investigated. The proposed precursors enable the monitoring of gate-oxide degradation without decoupling the impact of package degradation. Based on the findings, a simple early warning in situ circuit is proposed to monitor gate-oxide aging. A comprehensive precursor comparison is provided to show the merits of the proposed precursors. Finally, the experimental results are presented to validate the efficacy of the in situ monitoring circuit. [ABSTRACT FROM AUTHOR]

In this article, a new high-frequency PMSM model is derived in order to obtain accurate absolute inductance and inductance saturation profile. Compared to traditional PMSM models, the proposed high-frequency model includes the components of high-frequency resistance and inductance derivative relative to current. Through this model, the difference between differential and absolute inductances is discussed in detail and the impact of high-frequency resistance on the inductance estimation is analyzed. In the next step, another method is proposed to decouple and eliminate the effect of high-frequency resistance from the composite inductance. It is shown that this approach yields highly precise absolute inductance measurement and remarkably reduces the effect of inductance derivative relative to current. These findings help to evaluate the saturation more accurately which is essential for robust observer and controller design. Finally, the effectiveness of proposed scheme is experimentally verified using SPMSM and IPMSM. [ABSTRACT FROM AUTHOR]

This article proposes a new complete condition monitoring method which can independently monitor both the threshold voltage drift and the packaging degradation accurately by monitoring only the reverse body diode voltage drop at different gate bias levels. The SiC MOSFETs are aged through an accelerated aging method and the corresponding changes in electrical parameters are periodically measured to assess their correlation with the state of the device's health. It has been revealed that the on-state resistance reveals the combination of gate oxide and package-related degradation while the threshold voltage mainly depicts gate oxide-related issues. Unlike these two parameters, the body diode voltage drop is found to independently indicate the state of device health both for package and gate oxide. This is caused by a unique secondary conduction mode of SiC MOSFETs in third-quadrant operation which is clearly disclosed with transition boundaries by a proposed body diode transfer characterization curve. In order to have a detailed condition information of the device with a simple circuit, monitoring the reverse body diode voltage drop at 0 and $-$ 5 V gate bias is proposed. The proposed condition monitoring method is implemented on a gate drive circuit and experimental results are given for two artificially degraded devices. The experimental results confirm that the proposed method can independently monitor both the gate oxide and packaging degradations accurately by monitoring a single precursor parameter. The proposed method can be integrated into the gate driver or converter itself to monitor SiC devices. [ABSTRACT FROM AUTHOR]

Online junction temperature (Tj) measurement enables robust power converter operations by providing overtemperature protection and condition monitoring of the power devices. For SiC MOSFETs, the real-time (Tj) information is especially critical as limited field data are available regarding the reliability. In this article, utilizing the turn-on delay time as temperature sensitive electrical parameter, an online (Tj) measurement is realized through an intelligent gate drive. Specifically, the turn-on delay time is translated into the pulsewidth of a digital signal through the conditioning/logic circuits. During (Tj) measurements, the adjustable gate resistance circuit is activated to improve the measurement sensitivity beyond 600 ps/°C. Using the high-resolution capture module (300-ps resolution) in the system microcontroller, this pulsewidth is measured and then converted to junction temperature with a resolution of <0.5 °C. A prototype is built to validate the online (Tj) measurement method. The switching test results show that the circuit is able to precisely measure Td,on and offers a good linearity/sensitivity for (Tj) estimation. In the continuous operation, the junction temperature of a decapsulated device using an infrared camera and (Tj) obtained from the circuit match well with <1 °C difference under various operating conditions. In addition, the gate-oxide degradation's impact on Td,on is considered for SiC MOSFETs, and an aging compensation scheme is discussed to maintain the measurement accuracy throughout the device's lifetime. It is shown that the proposed circuit provides an accurate real-time (Tj) measurement for SiC MOSFETs, which can be deployed to improve the power converters’ reliability. [ABSTRACT FROM AUTHOR]

Early diagnosis of interturn short circuit (ITSC) fault is essential to prevent catastrophic electrical machine failures. Along with the detection, locating the faulty winding at its incipient stage is also critical to reduce the outage duration and operation losses. This article proposes a practical method to detect the ITSC fault and locate the faulty winding in permanent magnet synchronous motors (PMSMs) through stray magnetic flux monitoring. It is shown that relying on the fundamental stray flux component can potentially underperform at certain operating conditions leading to fault negative error. To compensate this shortcoming, the third harmonic component of stray flux is comprehensively analyzed and proposed as a complementary ITSC fault indicator. Furthermore, its reliability over the wide range of motor operation is verified to eliminate potential fault negative errors. It is also shown that the proposed method is independent of the fault severity which is a major advantage for practical applications. The findings are supported through 2-D-FEA PMSM drive system simulations and experiments under two different fault severity cases. [ABSTRACT FROM AUTHOR]

This paper presents an silicon carbide (SiC) MOSFET health condition monitoring method based on the switching transient measurements. Specifically, the device's turn-on time is used as the aging precursor, and a detection circuit is developed with picosecond resolution to detect the variations of the turn-on time. For this purpose, power cycles with constant junction temperature swings are applied on sample devices to accelerate their thermally triggered degradation. Over the aging process, device parameters are measured periodically using automated curve tracer to observe degradation-related changes. Also, a double pulse tester is used to evaluate devices’ switching transient changes throughout aging. Based on these results, both the theoretical discussions and experimental results imply that device turn-on time is a viable aging precursor and can be used to monitor device health at system start-up. High-resolution capture module of readily available system microcontroller is employed to measure the turn-on time through a simple auxiliary interface circuit on a buck converter. Experimental results show that onboard device aging can successfully be achieved during systems start-up in the order of microseconds. [ABSTRACT FROM AUTHOR]

In this article, an in situ SiC mosfet degradation monitoring method using readily available converter sensors is presented. Device's drain-source resistance in saturation and ohmic regions are employed as aging precursors to, respectively, indicate die and package-related degradations. The presented findings in this article are essential for low-cost and practical early warning systems in power electronics applications. To verify the effectiveness of the proposed method, a number of power-cycling tests are conducted to analyze aging process and fatigue mechanism. Device static parameters are measured throughout accelerated aging tests and the physical causes behind them are discussed in detail. It is shown that the drain-source resistance within saturation region at low gate bias can be used to indicate die-related degradation. Similarly, at full positive gate bias, device on-state drain-source resistance can be used to detect package-related degradation. In order to find out optimal variables such as applied gate bias, pulse duration, etc., a comprehensive single pulse test is conducted and the results are reported. Finally, the proposed degradation monitoring method is experimentally validated in the context of a three-phase inverter considering different sensor configurations and load types. [ABSTRACT FROM AUTHOR]

This paper addresses a simple and computationally efficient dynamic model for brushless permanent magnet (PM) motors under PM demagnetization faults. The impact of stator slots and spatial disposition of the windings are taken into account to improve the accuracy of a lumped-parameter $abc$ model. This model is suitable for tracking the dynamic behavior of fault components, as it can be accompanied by any control scheme and/or be used for model-based fault detection schemes. In addition, parameters of this model can be automatically tuned by an optimization process in the offline phase of the healthy machine. Finite-element simulations are carried out for proving the effectiveness of the proposed model. Verification is done in both time and frequency domains for four PM motors with different rotor and stator configurations. The simulation results are experimentally verified. [ABSTRACT FROM AUTHOR]

This paper presents a generic analytical tool to diagnose and classify faults in permanent magnet synchronous motors. The proposed method deploys wavelet transform to extract features for fault diagnosis, which provides a framework for studying nonstationary trends. Analyzing the stator current with wavelet raises a challenge since the energy of fundamental component spreads over different scales in the decomposition. An adaptive filter is used to estimate and remove the fundamental component in stator current. This filter predicts the main harmonic by processing the measured current data in real-time without any speed feedback. The proposed filter is designed in a way that it does not affect or suppress fault related harmonics. The estimation accuracy and convergence rate of this filter is tested and reported by error bounds, which exhibit an acceptable robustness. The validity of the proposed fault diagnosis approach is verified by finite element simulations and experimental results. The effectiveness of this algorithm is tested using two case studies including broken magnet and eccentricity faults. An average accuracy above 96% is obtained using experimental and simulation data. It is proven that the filtering scheme increases the overall accuracy of fault diagnosis. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) power mosfets are promising alternatives to Si devices in high-voltage, high-frequency, and high-temperature applications. The rapid and widespread deployment of SiC devices raises long-term reliability concerns, particularly for mission and safety critical systems due to limited field data and potential uncertainties. Therefore, it is essential to investigate progressive degradations and parameter shifts in SiC devices to develop system integrated degradation monitoring tools for self-monitoring converters, which can recognize failure precursors at the earliest stage and prevent catastrophic failures. This paper presents a comprehensive long-term reliability analysis of commercially available SiC mosfets under high temperature operation and high temperature swing, degradation related key precursors, and possible causes behind them. For this purpose, discrete SiC devices are power cycled and all datasheet parameters are recorded at certain intervals with the aid of the curve tracer. Variation of electrical parameters throughout the tests is presented in order to assess their correlation with the aging/degradation state of the switch. Among them, gate oxide charge trapping related threshold voltage drift and corresponding on state resistance variation has been observed for all samples. For some samples, bond wire heel cracking is found to be the root cause of sudden on state resistance and body diode voltage increases. The discussions regarding aging precursors are supported by failure analysis obtained through the decapsulation of failed devices. Finally, the findings are evaluated in order to define the suitability of electrical parameters as an aging precursor parameter under the light of practical implementation related issues. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on degradation monitoring of silicon carbide mosfets and proposes an early warning method to detect aging. The proposed plug-in tool can be integrated to smart gate drivers or directly to power converters. During the accelerated aging tests (power cycling within safe operating area), several electrical parameters are monitored to find out critical signatures and precursors of failure. Among those, gate leakage current is identified as the most practical precursor, which exhibits consistent changes in all aged devices and is relatively easy to monitor. Due to its simple scheme and low cost, it can potentially be embedded into commercial gate drivers featuring improved reliability options. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of short-circuit current behavior during interturn short-circuit faults in permanent magnet synchronous machines (PMSMs) by considering the short-circuit contact resistance. For this purpose, an finite element analysis (FEA)-based equivalent circuit model is developed to understand the circulating current behavior in the shorted turns. Various fault resistance and number of shorted turn combinations are examined at different torque and speed levels. To include saturation due to high fault currents, the inductance matrix of faulty machine is created in FEA environment and incorporated into the equivalent circuit model as four-dimensional lookup tables. In order to take loop responses into account, the model is controlled through field oriented control (FOC) with closed speed and current loops. An experimental setup is built to verify the simulation results using a PMSM with several winding taps. It is shown that the experimental results and the simulations are quite consistent with each other. The findings from this study are essential to predict fault severity, develop mitigation techniques and determine the safe operating area for faulty machines. [ABSTRACT FROM AUTHOR]

Discrete package insulated gate bipolar transistor (IGBT) devices are a popular choice for low-power converters. Although IGBT power modules used in high-power applications have recently been studied in the literature, there are major knowledge gaps regarding reliability and lifetime estimation of discrete devices. In this paper, on-state collector–emitter voltage drop $(V_{{\rm{ce}},{\rm{on}}})$ variations are characterized for discrete IGBT devices exposed to cyclic thermal stresses. Variations in $V_{{\rm{ce}},{\rm{on}}}$ are carefully identified and classified depending on different aging mechanisms, stress levels, and device structures. A probabilistic framework for remaining useful lifetime (RUL) estimation based on the knowledge obtained by accelerated aging experiments for real-time RUL estimation has been proposed. Specifically, the proposed model uses Gaussian process regression (GPR) for applying a Bayesian inference (BI) on RUL estimation of the device under test. Using BI reduces the uncertainty associated with RUL estimation and leads to more accurate results. This concept is also tested by comparing the classical maximum-likelihood estimation and GPR estimation results with the ones obtained by accelerated aging tests. [ABSTRACT FROM PUBLISHER]

This paper presents a detailed magnet defect fault detection analysis through fluxgate sensors by monitoring the leakage flux around permanent magnet synchronous motors. The flux spectra of electric machines contain direct and most critical information to monitor and characterize magnet defect faults and their progressions. In the mainstream diagnosis techniques based on phase current and back-EMF analysis, the fault corresponding signature characteristics may vary and cause misleading results depending on motor topology, winding configuration, number and location of defective magnets, and controller parameters. In this paper, it is shown that leakage flux analysis provides some superior results for magnet defect diagnosis. For this purpose, the fault patterns in the leakage flux spectrum are exhaustively analyzed at different torque/speed profiles. Simulation and experimental results show that the deployment of a direction sensitive fluxgate sensor in magnet defect fault detection yields very promising results both in time and frequency domain analyses. [ABSTRACT FROM AUTHOR]

The efforts for more reliable power conversion systems have been gaining momentum in recent years. The majority of the studies concerning reliability of power switches focus on the package-related failures, mainly caused by the cyclic thermal stress. The basic failure precursor for this type of stress has been identified as increased on-state resistance for power MOSFETs in the recent literature. On-state resistance monitoring during converter operation is a challenging and costly task as it requires current and voltage sensing circuits, which can block the high voltage across the switch during off-state to protect the measurement or control unit. This paper proposes a software frequency response analysis method to determine the health status of high-voltage power MOSFETs with high on-state resistance. This is achieved by analyzing and evaluating the variation in the plant model at double pole frequency using the same DSP that is used for control purposes. The proposed concept is analyzed for boost converter; however, it can be used to detect the on-state resistance variation in other types of converters operating in continuous condition mode (CCM). The proposed algorithm is embedded in a low cost DSP and experimentally verified on a dc/dc boost converter. [ABSTRACT FROM AUTHOR]