Reliability Of Converter Research Articles

Active Thermal Management Method for Output-Parallel DAB DC–DC Converters Under Parameter Mismatches and Asymmetrical Modulation

In OP-DAB converters, the asymmetrical phase-shift-modulation (PSM) and the mismatched parameters will result in the thermal imbalance, which leads to premature aging and failure. To suppress the thermal imbalance, an active thermal management consisted of an improved PSM and a reliability-based power divider (PD) is proposed. Firstly, a losses model based on double-phase-shift control is established to analyze the power losses and estimate the junction temperature. Secondly, the reason for the unbalanced thermal distribution under the asymmetrical PSM is studied, and a modulation cycle instead of the switching cycle is adopted in the modulation process to make targeted improvements. Thirdly, based on the estimated temperatures, the reliability-based PD is established by linking IGBT temperature and its failure rate, and the optimal power distribution coefficient is obtained to deal with the negative effect of the mismatched parameters. With the proposed active thermal management method, the thermal distribution become balanced, the converter reliability is increased. Besides, the proposed method does not bring bad effect on the electrical performance. Finally, all theoretical analysis and conclusions are verified based on a simulation example and a prototypic experiment.

Comprehensive reliability evaluation of three types of connection of DC–DC converters: single‐phase, two‐phase, and parallel input‐series output

AbstractWith the increasing use of power electronic converters, the reliability studies of these converters are essential. The most important factor in increasing the reliability of power converters is their structures. In this paper the reliability evaluation of a DC–DC converter with various connections including single‐phase, interleaved, and parallel‐input and series‐output (PISO) topologies is presented. In the first view, it seems that the interleave topology has high reliability, but considering the more presented detailed indexes, it is identified that the PISO structure has a higher reliability than the interleave structure. In this paper for better evaluation, the various topologies are considered which operate at full rated power and half power. To calculate the reliability of the converters the important parameters such as the thermal and electrical stresses of elements are considered. The Markov model is used to evaluate the reliability. In order to verify the presented studies and analysis, the DC–DC converters with single‐phase, interleaved, and PISO have been implemented. The experimental results show that the PISO topology has higher reliability.

An Intuitive and Noniterative Design Methodology for CLLC Chargers Employing Simplified Operation Modes Model

This paper mainly focuses on the simplified operation modes (SOM) model and resonant parameter design for the CLLC charger. Based on the mathematical and detailed operation waveform assumptions, the voltage gain model expressions and the operation mode boundaries are calculated directly, providing the high efficiency and high reliability of the CLLC converter. The proposed SOM model is more accurate in depicting the voltage gain compared with the conventional fundamental harmonic approximation (FHA) model. Moreover, the SOM model is more intuitive and has less computational complexity than the complicated and unsolvable time-domain model. As for the parameter design process, the inductance ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k$</tex-math></inline-formula> and characteristic impedance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Z_{0}$</tex-math></inline-formula> are selected instead of specific inductances and capacitances. Relying on the SOM model, a step-by-step parameter design methodology is studied, which avoids repetitive iterations and streamlines the procedure. The voltage gain range, efficiency, soft-switching operation, mode boundaries, and system stability are considered comprehensively and realized in this process. The simulations and experiments validate that the proposed SOM model is accurate, and the design methodology is straightforward through a 1-kW CLLC charger prototype with 97% peak efficiency.

Multi-Level Synthesis Gate Voltage Active Control Technology for Optimizing IGBT Switching Characteristics

Compared with the conducting and blocking steady-state processes, the voltage and current stress of IGBT become very higher in the turning-on and turning-off transient processes, and the instantaneous power loss increases significantly. The switching transient conditions greatly affect the reliability and stability of IGBT device and power converter. During the IGBT turning on process, the reverse recovery of the symmetrical bridge arm anti paralleled diode can cause additional turn-on loss and current peak overshoot. The gate voltage active control technology can effectively suppress current spike and reduce turn-on loss in the period from the initial opening time to Miller platform. The multilevel synthesis technology can adjust the gate voltage waveform and produce depression or bulge in the normal driving voltage waveform for a certain time. In this paper, the sensitive parameters of gate voltage active control, which affect the current overshoot, and turn-on loss of IGBT are studied based on the theoretical calculation and mathematical model. A multi-level synthesis gate voltage active control technology is proposed according to the principle of gate voltage active control. The relationship among the acting voltage amplitude, execution time, current peak and switching loss is studied. Considering the actual application conditions, the optimized active control scheme of gate voltage is designed. Finally, the switching characteristics test is carried out, the results verify that the proposed control technology can effectively reduce the current overshoot and turn-on loss in comparison with the conventional schemes.

An Open-Circuit Faults Diagnosis Method for MMC Based on Extreme Gradient Boosting

The diagnosis of open circuit faults is required for the reliability of modular multilevel converters (MMC) and the complex operating environment of MMC may cause missing data and external noise in signal detections, where some of the present open circuit fault detection methods can be disabled. This paper proposed a machine learning (ML) diagnosis strategy for open circuit faults in MMC based on extreme gradient boosting (XG-Boost). In this method, after data processing, the data segments composed of real-time capacitance voltage and current data are input into the trained XG-Boost multi-classification model for fault diagnosis without manually setting the empirical threshold, as is required in traditional change-of-rate-of-voltage-based diagnosis methods. This method has excellent robustness against external noise and missing data while better accuracy, higher speed and lower real-time calculation cost than existing ML-based methods are achieved. The effectiveness of the proposed method is verified by experiment results. It can diagnose the fault within 20ms with accuracy as high as 99.6&#x0025;, even under the interference of Gaussian (GS) noise and the capacitor voltage data missing.

Open-circuit fault detection of inverter fed PMSM for electrical powertrain applications

&lt;p&gt;This paper aims to enhance the reliability of power electronic converters fed&lt;br /&gt;permanent magnet synchronous machine for electrical powertrain applications.&lt;br /&gt;Many faults like open circuit may affect the power converter and quickly lead to&lt;br /&gt;a decline in supplied power quality and all the power train components behavior.&lt;br /&gt;In this framework, this paper proposes an open circuit fault detection scheme for&lt;br /&gt;inverters. First, the dynamic models of the powertrain subsystems were developed.&lt;br /&gt;In fact, all the mathematics models of the motor, inverter, power converter,&lt;br /&gt;battery and charger are presented. Then, a detection scheme of open-circuit fault&lt;br /&gt;in inverter/motor. The control schemes were elaborated based on current analysis&lt;br /&gt;method. The diagnosis strategy under discontinuous switch-ing dynamics of&lt;br /&gt;the DC/AC inverter is proposed.&lt;/p&gt;

A Non-Isolated Multiport Converter for E-Vehicle Applications

The necessity to reduce the risks in the environmental pollution has paved way for the options that help in minimizing it. Electric vehicle is one such option and the most evolving means in this field. The EV system in order to achieve a high peak requires multiple sources to be integration. So, a bidirectional buck boost DC to DC converter with four port is realized in this research for integration of many sources instead of using dedicated converter. This non isolated multi-port converter with compact size, minimum number of components and simple controlstructure enhances converter reliability and makes it more economical. This converter has the ability to accommodate energy sources with varying current and voltage characteristics. This converter has two input ports the DC supply &amp; the Batteryas well as two output ports motor and auxiliary loads. This multi-port converter exhibits bidirectional power flow capability during the regenerative braking of an E-Vehicle. The converter employs three switches to control the flow of power. The article aims in studying the performance of the controller structure used in regulating the flow in power of energy sources and analyses its dynamic as well as the steady state characteristics. The design is validated using MATLAB Simulink tool to ensure its performance.

Reliability Analysis of Multi-Level PFC Converter-Based Charger for Light EV Charging Application

Electric vehicle (EV) charging architectures with two stages consist of rectification and a DC–DC conversion stage. Multi-level rectifiers are emerging as better alternatives in the rectification stage of EV charging applications. As they possess minimum voltage stress on switches, better harmonic profile at the grid side, lower dv/dt stress, and higher voltage capability. In this article, a five-level rectifier in conjunction with a phase shift full bridge converter is implemented for EV charging applications. The rectifier has the inherent capacitor voltage balancing capability and maintains unity power factor at the source side under varieties of operating conditions. The reliability of power electronic converters can be estimated by accessing the reliability of each component in converters. To establish the suitability of the implemented system for real-time EV charging applications, comprehensive performance analysis has been carried out including reliability assessment, the impact of parametric variations on reliability, calculation of losses and efficiency. The battery charger is mathematically modeled and validated experimentally in laboratory. The comparative analysis of the rectifier with state-of-the-art literature has been also carried out.

Investigation of Off-State Stress Induced Degradation of SiC MOSFETs Under Short-Circuit Condition

Investigation of SiC MOSFETs short-circuit (SC) degradation mechanism is critical to improve the overall reliability of power converters. At present, research on the SiC MOSFETs degradation mechanism mainly focuses on the on-state phase of the SC period. While, ruggedness of SiC MOSFETs in the off-state phase of short-circuit tests (SCTs) were neglected. In this paper, SiC MOSFETs degradation mechanism in the off-state phase of SCTs are investigated comprehensively. Specifically, distribution and magnitude of electrothermal stress of devices under test (DUTs) in the off-state phase of SCTs are analyzed by TCAD simulation. Which reveals two important phenomena: i) the device will suffer from long-term high temperature and high electric field stress in the off-state phase when negative turn-off gate voltage (Vgs-off) is applied; ii) high hole current in the channel region will last for several microseconds after the device is turned off. The observed SiC MOSFETs degradation in the off-state phase of SCTs is then proved by experiments, through which, the excessively low Vgs-off can reduce the SC capability of SiC MOSFETs is concluded. Moreover, the degradation results of static parameters of SiC MOSFETs are presented and the degradation mechanism is analyzed in detail.

Reliability of Marine Energy Converters

The oceans cover 71% of Earth’s surface and are an enormous source of renewable energy which comes from tides, waves, ocean currents, and salinity and temperature differences [...]

Shared Redundancy Strategy to Improve the Reliability and Fault-Tolerant Capability of Modular Multilevel Converter

Utilizing redundant sub-modules is a well-known strategy to improve the reliability and fault-tolerant capability of the modular multilevel converter (MMC). Redundancy-based fault-tolerant strategy makes it possible to restore the full performance of the converter in the post-fault condition. The main drawback of this strategy is the high cost. In this configuration, each redundant sub-module (RSM) can only be utilized in a specific arm and it cannot be used in other arms. This limitation leads to inefficient utilization of the RSMs in conventional MMC. This paper proposes a shared redundancy strategy which allows RSMs to be used either in upper or lower arms. The derived reliability models in various case studies illustrate that proposed strategy significantly improves the reliability and useful lifetime of MMC. To investigate the effectiveness of the proposed strategy, simulation and experimental results are provided.

Degradation Behavior and Mechanism of Metalized Film Capacitor Under Ultrahigh Field

Metalized film capacitor degradation under ultrahigh electric fields is crucial for the reliability of voltage source converter (VSC)-HVDC systems. In the present study, systematic investigations were performed that metalized film capacitors were aged under the dc electric field ranging from 300 to 400 kV/mm. Results showed that under moderate electric field, the capacitance reduction of sample capacitors presented two stages with different decay rates. With the increase of the electric field, the rapid degradation occurred immediately on the starting of the aging process, suggesting a voltage threshold determining the capacitors’ stability. In addition, the degradation mechanisms of both metalized films and biaxial oriented polypropylene (BOPP) base films were investigated by statistical analysis and structural experiments. Below the voltage threshold, more shallow traps were generated and the activation energy of molecular motions was reduced due to PP molecules scissions, resulting in the decrease of breakdown strength (BDS) of BOPP films. While above the voltage threshold, the accelerated failure could be attributed to two main causes: the fast breakdown of originally formed weak points and the dramatically increased self-healing area. The study can contribute to the design and evaluation of dc-link capacitors both experimentally and theoretically.

Charging Infrastructure and Grid Integration for Electromobility

Electric vehicle (EV) charging infrastructure will play a critical role in decarbonization during the next decades, energizing a large share of the transportation sector. This will further increase the enabling role of power electronics converters as an energy transition technology in the widespread adoption of clean energy sources and their efficient use. However, this deep transformation comes with challenges, some of which are already unfolding, such as the slow deployment of charging infrastructure and competing charging standards, and others that will have a long-term impact if not addressed timely, such as the reliability of power converters and power system stability due to loss of system inertia, just to name a few. Nevertheless, the inherent transition toward power systems with higher penetration of power electronics and batteries, together with a layer of communications and information technologies, will also bring opportunities for more flexible and intelligent grid integration and services, which could increase the share of renewable energy in the power grid. This work provides an overview of the existing charging infrastructure ecosystem, covering the different charging technologies for different EV classes, their structure, and configurations, including how they can impact the grid in the future.

UGF-based signature reliability for solar panel k-out-of-n- multiplex systems

PurposeThe purpose of this paper is to evaluate the reliability and signature reliability of solar panel k-out-of-n-multiplex system with the help of universal generating function.Design/methodology/approachEnergy scarcity and global warming issues have become important concerns for humanity in recent decades. To solve these problems, various nations work for renewable energy sources (RESs), including sun, breeze, geothermal, wave, radioactive and biofuels. Solar energy is absorbed by solar panels, referred to as photovoltaic panels, which then transform it into electricity that can be used to power buildings or residences. Remote places can be supplied with electricity using these panels. Solar energy is often generated using a solar panel that is connected to an inverter for power supply. As a result, a converter reliability evaluation is frequently required. This paper presents a study on the reliability analysis of k-out-of-n systems with heterogeneous components. In this research, the universal generating function methodology is used to identify the reliability function and signature reliability of the solar array components. This method is commonly used to assess the tail signature and Barlow-Proschan index with independent and identically distributed components.FindingsThe Barlow-Proschan index, tail signature, signature, expected lifetime, expected cost and minimal signature of independent identically distributed are all computed.Originality/valueThis is the first study of solar panel k-out-of-n-multiplex systems to examine the signature reliability with the help of universal generating function techniques with various measures.

An improved method to sub‐module voltage balancing in modular multilevel converters with two voltage sensors

SummaryThe modular multilevel converter (MMC) is an innovative structure that has expanded the usage of multilevel converters (MLCs) in the electrical industry. Since the MMC initially required a large number of sensors to manage the capacitor voltages, various studies have been done to reduce their number to improve the converter's reliability and reduce construction costs. In this paper's proposed method, merely two voltage sensors are used to balance the converter's capacitor voltages, and voltages are estimated using the exponentially weighted recursive least square (RLS) method in each sampling time. Also, the estimated voltages are sorted according to the capacitor current sign determined by the voltage sensors, and the current sensors are entirely eliminated. Furthermore, three cases for compensating the capacitor estimated voltages are presented, and the last case proposes the sub‐module force algorithm (SFA) for system protection. The efficacy of the proposed method has been assessed via simulation and experimental implementations.

Evaluation of super-twisting SMC and NSC combination for power control in multi-source renewable power generation system

This work is based on the evaluation of a super-twisting sliding mode controller for power control in an isolated multi-source renewable generation system. The hybrid multi-source system taken into consideration, in this case, is made up of three different generation units. The main generation unit is a 22kW micro-hydro system with a self-excited induction generator. To this, a 7.5kW doubly fed induction generator-based wind energy conversion system is integrated. An 18kW solar PV system connected to a battery energy storage system is connected at the dc-link. All the above systems are integrated through a bidirectional nine-switch converter. The autonomous hybrid system's power control is solely done by the nine-switch converter. In this work, efforts have been made to combine the robustness and accuracy of super-twisting sliding mode controllers with the reliability and flexibility of the nine-switch converters. The performance evaluation of the above combination is done with various load and source side disturbances. The system's uninterrupted power supply capability has also been examined in this work. Using the MATLAB environment, the system's performance is evaluated, examined, and the same has been verified using an OPAL-RT 4510 real-time simulator.

In Situ Diagnosis of Multichip IGBT Module Wire Bonding Faults Based on Collector Voltage Undershoot

Condition monitoring of insulated gate bipolar transistor (IGBT) modules is an effective way to improve the transient performance and reliability of modular multilevel converters (MMC). This article proposes a novel bond wire failure monitoring method for the multichip IGBT modules in the MMC half-bridge submodule (SM) structure. The collector voltage undershoot <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CA(np)</sub> of the complementary IGBT switch is measured during the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> switching transition of the controlled IGBT switch. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CA(np)</sub> is sensitive to the induced voltage over the stray inductance of the IGBT bond wires and provides high sensitivity as a health indicator. The non-intrusive measurement technique is demonstrated using a half-bridge circuit during the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> transition of the controlled IGBT, while its complementary switch (i.e., the device under test) is in the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> state. Theoretical analysis and experimental results show that the parametric drift due to wire bonding failures can be effectively monitored with high specific relative sensitivity and granularity. To ensure its effectiveness in practical applications, the influence of load current, SM capacitor voltage, and junction temperature is discussed. In addition, a readout circuit is designed featuring the integrated desaturation detection and voltage peak detection, which offers both the short-term overcurrent fault protection and long-term bond wire aging monitoring functions.

A Unified Open-Circuit-Fault Diagnosis Method for Three-Level Neutral-Point-Clamped Power Converters

Fast and accurate fault diagnosis is important to enhance the reliability of power converters. Since both open-circuit faults in insulated gate bipolar translator (IGBTs) and diodes deteriorate power quality, diagnosis methods only focusing on IGBT failures are easily disturbed by diode failures. In this work, we propose a unified effective residual-based open-circuit fault diagnosis method for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">all</i> semiconductor devices including IGBTs, clamping diodes, and freewheeling diodes in three-level neutral-point-clamped power converters. The voltage and current residuals are calculated from the mismatches between the actual current path and the estimated one, requiring <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">solely</i> the already existing current measurement of the system. By analyzing the variation of the voltage and current residuals in all open-circuit failure cases, the proposed diagnosis method can locate the faulty switch within several sampling periods, i.e., less than 1 ms. Finally, the proposed diagnosis method is incorporated in the model predictive current control framework. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Both</i> experimental <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">and</i> hardware-in-the-loop results confirm the effectiveness and robustness of the proposed diagnosis method at various operation scenarios.

Fault diagnosis of power converters in a grid connected photovoltaic system using artificial neural networks

Introduction. The widespread use of photovoltaic systems in various applications has spotlighted the pressing requirement for reliability, efficiency and continuity of service. The main impediment to a more effective implementation has been the reliability of the power converters. Indeed, the presence of faults in power converters that can cause malfunctions in the photovoltaic system, which can reduce its performance. Novelty. This paper presents a technique for diagnosing open circuit failures in the switches (IGBTs) of power converters (DC-DC converters and three-phase inverters) in a grid-connected photovoltaic system. Purpose. To ensure supply continuity, a fault-diagnosis process is required throughout all phases of energy production, transfer, and conversion. Methods. The diagnostic approach is based on artificial neural networks and the extraction of features corresponding to the open circuit fault of the IGBT switch. This approach is based on the Clarke transformation of the three-phase currents of the inverter output as well as the calculation of the average value of these currents to determine the exact angle of the open circuit fault. Results. This method is able to effectively identify and localize single or multiple open circuit faults of the DC-DC converter IGBT switch or the three-phase inverter IGBT switches.

Fault Management Techniques to Enhance the Reliability of Power Electronic Converters: An Overview

The reliability of power electronic converters is a major concern in industrial applications because of using prone-to-failure elements such as high-power semiconductor devices and electronic capacitors. Hence, designing fault-tolerant inverters has been of great interest among researchers in both academia and industry over the last decade. Among the three stages of fault management, compensating the fault is the most important and challenging part. The techniques for fault compensation can be classified into three groups: hardware redundancy methods which use extra switches, legs, or modules to replace the faulty parts directly or indirectly, switching states redundancy methods which are about omitting and replacing the impossible switching states, and unbalance compensation including the techniques to compensate for the unbalances in the system caused by a fault. In this paper, an overview of fault-tolerant inverters is presented. A classification of fault-tolerant inverters is demonstrated and major cases in each of its categories are explained.