Converter Components Research Articles

A Health-Oriented Control Strategy for DC-Link Capacitor in Direct Drive Wind Turbine Converter

As the weakest components of wind turbine converters, dc-link capacitor withstands high-frequency ripple currents from both rectifier and inverter. Traditional wind turbine control strategy does not consider the influence of the harmonic current generated by both side converters on the dc-link capacitor, and ignores the restriction on the reliability of direct-drive wind turbine converter. For the reason, this paper synthesized the wind turbine model and dc-link capacitor harmonic spectrum analytical approach to derive the connection between mission profile and harmonic spectrum. Regarding with the capacitor lifetime model, the optimal mapping from control strategy to mission profile, maximizing the service life of capacitor, was solved. With the proposed health-oriented control strategy, the core temperature of dc-link capacitor can be effectively reduced, which can increase the service life of capacitor, making the dc-link capacitor no longer the most fragile component in wind turbine converter and ultimately improving the reliability of converters.

Condition Monitoring of Power Electronic Systems Through Data Analysis of Measurement Signals and Control Output Variables

A major disadvantage of existing condition monitoring methods is the need for additional sensors and measuring equipment. In this work, this disadvantage is eliminated by completely avoiding additional hardware. Instead, software-based methods from the field of machine learning are used. Therefore, measurement signals and control output variables are utilized, which are acquired and processed in any power electronic system for the purpose of converter control. The publication focuses on two main converter components: power semiconductors and dc-link capacitor. For each component, the aging mechanisms that have been studied in the literature are explained. Based on the aging mechanisms, the degradation indicators are identified. Then, a converter model is built that allows the variation of degradation indicators in order to analyze their effects on the available dataset. These findings form the basis for mathematical models, which detects future failure mechanisms of this type during converter operation. The test setup must offer the possibility of generating reproducible failure cases in various components with the aid of additional failure equipment. Finally, failure mechanisms are intentionally introduced at the test bench in order to validate the methodology of the developed approach.

Design Optimization of Synchronous Buck Converter (SBC)

Abstract: Nowadays Switched-mode power converters are playing a significant role in the industries by providing higher efficiency for various applications. There are various applications that implement power supply and battery charge circuits for devices like smartphones, TVs, and various electronic devices When it comes to DC-DC Converters the most popular among the industries are buck converters and the efficient version of the buck converter is the Synchronous buck converter. The SBC steps down the voltage from higher to lower levels. Efficiency is a crucial parameter as the industry’s focus is on delivering greater performance devices. The power converter's design must be optimized to maximize performance to achieve customer expectations. As a result, a thorough understanding of the synchronous buck converter and how to properly select the circuit components is critical. The proposed work aims at optimizing the Synchronous Buck Converter components such as Inductors, Capacitors, and Resistors. The idea of this optimization study is to improve the performance of the converter and reduce power losses and cost-cutting. In this paper, the control mode considered is peak current mode control.

Towards Data-Driven Fault Diagnostics Framework for SMPS-AEC Using Supervised Learning Algorithms

The service life of aluminium electrolytic capacitors is becoming a critical design factor in power supplies. Despite rising power density demands, electrolytic capacitors and switching devices are the two most common parts of the power supply that age (deteriorate) under normal and diverse working conditions. This study presents a fault diagnostics framework integrated with long-term frequency for a switched-mode power supply aluminium electrolytic capacitor (SMPS-AEC). Long-term frequency condition monitoring (CM) was achieved using the advanced HIOKI LCR meter at 8 MHz. The data acquired during the experimental study can help to achieve the needed paradigm from various measured characteristics of the SMPS/power converter component to detect anomalies between the capacitors selected for analysis. The CM procedure in this study was bound by the electrical parameters—capacitance (Cs), equivalent series resistance (ESR), dissipation factor (DF), and impedance (Z)—-acting as degradation techniques during physical and chemical changes of the capacitors. Furthermore, the proposed methodology was carried out using statistical feature extraction and filter-based correlation for feature selection, followed by training, testing and validation using the selected supervised learning algorithms. The resulting assessment revealed that with increased data capacity, an improved performance was achieved across the chosen algorithms out of which the k-nearest neighbors (KNN) had the best average accuracy (98.40%) and lowest computational cost (0.31 s) across all the electrical parameters. Further assessment was carried out using the fault visualization aided by principal component analysis (PCA) to validate and decide on the best electrical parameters for the CM technique.

DC-DC High-Step-Up Quasi-Resonant Converter to Drive Acoustic Transmitters

This paper proposes a quasi-resonant step-up DC-DC converter to provide the DC-link voltage for piezoelectric transmitters (PZETs). The resonance not only provides a soft-switching condition for the converter switches, but also helps to decrease the converter element sizes for marine applications. Operation modes of the proposed converter are discussed. The current and voltage of the converter components are derived analytically, and hence the converter gain is obtained. The performance of the proposed high-step-up, high-power density converter is examined through a comprehensive simulation study. The simulation results demonstrate the soft-switching operation and short transient time required for the converter to reach the reference output voltage. The converter output voltage remains unchanged when an inverter with a passive filter is placed at its output while supplying the PZET. The proposed DC-DC converter is prototyped to validate the converter gain and soft-switching operation experimentally. The converter gain and soft-switching results in simulation are well matched with those of the experimental tests. The converter efficiency in three different switching frequencies is obtained experimentally. The power density of the proposed topology is determined via the designing of a printed circuit board. The experimental results demonstrate the appropriate gain and efficiency of the converter in the tested power range.

Design Methodology Based on Prebuilt Components for Modular Multilevel Converters with Partial Integration of Energy Storage Systems

To provide ancillary services in HVDC applications, modular multilevel converters (MMCs) with integration of energy storage systems are a promising solution as they take advantage of the modularity and the controllability of the stored energy. In these solutions, an energy storage system is connected to the DC capacitor of a submodule (SM) to make an energy storage submodule (ES-SM). An MMC with partial integration (MMC-PIES) is an MMC with each arm made of a mix of SMs and ES-SMs. In this paper, we propose a novel design methodology for these converters considering they are built based on existing prebuilt submodules, while design methodologies in the literature consider the SM and ES-SM characteristics to be degrees of freedom. Therefore, the proposed approach is closer to an industrial standpoint and computes the minimum number of ES-SMs to comply with requirements. We also include a new optimization method for the circulating currents needed to balance the energy in the SM and ES-SM capacitors. Design scenarios are presented. The results show that the value of the DC capacitance and the current limitation of the switches highly influence the design, restricting the possible operating points. In addition, half-bridge ES-SMs seem to be a more promising solution than full-bridge ES-SMs, reducing the number of ES-SMs.

Energy Management System and Enhancement of Power Quality with Grid Integrated Micro-Grid using Fuzzy Logic Controller

A modern hybrid model is introduced, which is a combination of PV, Wind turbine, converter components to improve Microgrid (MG) operation, to improve system dependability, effective efficiency, which are fundamental qualities. In view of renewable energy Maximum Power Point Tracking (MPPT) is frequently applied to improve PV efficiency in which randomness, flexibility of solar energy because of changes in temperature. To achieve MPPT P&O rule, Incremental conductance (IC) methods are implemented in this manuscript. The design, execution of EMS with Fuzzy Logic Controller (FLC) for AC/DC microgrid is implemented. Apart from designing of EMS the power quality of MG is improved. It proposes analysis, control of storage devices. The FLC improves battery life and also will achieve desirable SoC. An FLC based EMS grid integrated MG is adopted, to mitigate power quality issues under nonlinear, unbalanced load conditions. The proposed model is executed by adopting MATLAB/SIMULINK

Mites as a Potential Path for Ce-Ti Exposure of Amphibians

Despite the documented effects on human and animal health, particles smaller than 0.1 µm in diameter found in soils, sediments, and the atmosphere remain unregulated. Yet, cerium and titanium oxide nanoparticles associated with traffic increase mortality, cause behavioral changes, and inhibit the growth in amphibians. Mites of the genus Hannemania spend their early stages in the soil before becoming exclusive parasites of amphibians. Unlike other mites, Hannemania is found inside the epidermis of amphibians, thus facilitating the intake of particles, and leading to direct and chronic exposure. To better understand this exposure path, we sampled amphibians hosting mites in a river potentially polluted by traffic sources. Particles collected from mites were studied by scanning electron microscopy and Raman spectroscopy while sediment samples were analyzed for total metal content by portable X-ray fluorescence. Our results indicate that sediment samples showed significant correlations between elements (Zr, Mn, Ti, Nb, Fe) often associated with components in catalytic converters and a level of Zr that exceeded the local geochemical background, thus suggesting an anthropic origin. Furthermore, particles adhered to mites exhibited the characteristic Raman vibrational modes of ceria (CeO2, 465 cm−1), ceria-zirconia (CeO2-ZrO2, 149, 251, and 314 cm−1), and rutile (TiO2, 602 cm−1), pointing out to the deterioration of catalytic converters as the most likely source. This research highlights both the importance of unregulated catalytic converters as a source of ultrafine Ce-Ti particle pollution and the role of sub-cutaneous mites as a vector of these particles for amphibian exposure.

Robust three-phase state estimation for PV-Integrated unbalanced distribution systems

As the increasing penetration of renewable energy brings uncertainty and fluctuation into the operating conditions of distribution systems, distribution system state estimation (DSSE) needs to track not only the state of the network, but also the state of the renewable energy sources robustly and under unbalanced conditions. Aiming at delivering comprehensive situational awareness of distribution systems hosting solar photovoltaic (PV) power plants, this paper proposed a joint state estimation model for unbalanced distribution systems integrated with single-phase and three-phase PV power plants, as well as an extended weighted least absolute value (EWLAV) estimation algorithm for handling simultaneous measurement errors and control input errors. The proposed state estimation model considers various loss components of single-phase and three-phase power electronic converters, and is applicable to general unbalanced conditions including unbalanced phasing and parameters of distribution lines, PV power plants, and loads. The proposed EWLAV algorithm leverages sparse l1 optimization principles and can identify and suppress the gross errors in both measurements and converter control inputs. Simulation results show that the developed model can reliably reflect the characteristics of three-phase unbalanced distribution networks and PV plants, and the EWLAV algorithm produces unbiased results under simultaneous measurement errors and control input errors, which conventional estimators such as the weighted least squares (WLS) and weighted least absolute values (WLAV) cannot achieve.

Evaluating the properties of impulse signals transmitted over circuits with distributed and lumped parameters

The dependability of the ABTC-MSh automatic block system entirely depends on the functional safety and operational stability of its component devices, most of which operate in pulse mode. One of the key components of pulse signal converters is various transformers and chokes, whose calculation and development is, in practice, often difficult due to insufficient consideration of stray parameters and operational specificity of such electromagnetic systems when the core is magnetized. The paper estimates the results of coordination of the transformer’s electrical characteristics with the load impedance and that of the pulse signal source suitable for analysing and constructing signal-shaping networks and delay lines based on lumped elements. Aim. The aim of the work is to substantiate an engineering technique for calculating the duration of the leading edge of a signal in the process of setting its level at the output of the forming circuit of a pulse transformer when matching with loads and estimating the delay time for switching on the actuator at a given response threshold, depending on the parameters of the second-order circuit, which is often used as a feedback element of pulse converters and auto-regulation systems. Methods. The time characteristics and pulse form are determined for a transformer whose equivalent circuit corresponds to the item’s operation in high frequencies and takes into account the stray parameters normalized to to the primary side. The output signal function is described in accordance with the linear electric circuit theory in operator form and, after a series of Laplace transformations, the generalized expression of the transmission factor is reduced to a standard form for a second-order circuit. The analytical solution was found by determining the values of the zeros and poles of the function on the plane of complex numbers as roots of quadratic equations expressed in terms of the coefficient of circuit damping. Graphs of the field dependences of the processes of establishing the pulse amplitude at the output of the forming circuit and the proportions of the amplitude outlier on the attenuation coefficient are given for various ratios of the coefficients of matching the transformer wave resistance with the load impedances and the pulse signal source. Point estimates of the pulse edge duration are made using the Mathcad programming function and taking into account the dimension of TRUE/FALSE matrices that reflect the transition from zero to one. This allows proposing linear approximations of the duration dependences within the given interval with a single inflection point that corresponds to the condition of complete matching of all resistances. Information is provided on the deviation of the approximation from the calculated data, the delay time of the actuator by the threshold. It is also discussed whether it is admissible to represent distributed parameters in the form of lumped elements while implementing artificial delay lines and higher-order circuits. Results. Conclusions. The specified problem is resolved by defining a unique calculated dependence that associates the signal edge duration to the transmission coefficient of the examined second-order circuit. The validity of the method for dependence deduction is based on describing the output signal of a pulse transformer in a general form, subsequent analysis of the expression and deduction of an accurate analytical solution, taking into account the primary stray parameters of the transformer and load values.

Auxiliary Power Supplies for High-Power Converter Submodules: State of the Art and Future Prospects

Recent developments in medium-voltage (MV) silicon and silicon carbide (SiC) power semiconductor devices are challenging state-of-the-art converter and auxiliary power supply (APS) designs. The APS is an important converter component, which energizes the gate-drive units and, therefore, has an influence on the overall reliability and efficiency of the converter system. There has, however, been comparably little research on how the APS of high-power converter submodules can be realized, in particular, for high-voltage applications. New, or improved, solutions may build on state-of-the-art topologies in the near future, but utilize MV SiC technology in the APS circuit itself to enable improved efficiency, reliability, simplicity, and compactness. Externally-fed APS concepts could provide several further advantages. Their various benefits on converter and system level may enable them to be a competitive solution for future APS concepts. Especially, light-based power supply systems are considered most useful since they offer extreme voltage isolation capability and immunity to electromagnetic interference. This article presents a review of the wide range of solutions for APSs, possible implementation options, and the most important design considerations. The different solutions are evaluated in a qualitative fashion, providing an overview of available APS concepts with regard to the requirements for high-power converter applications.

Developing a Generalized Multi-Level Inverter with Reduced Number of Power Electronics Components

Reducing the number of components of power electronic converters has been an important research topic over the past few decades. This paper introduces a new structure for a multi-level inverter based on reduced switch basic modules. The proposed basic module requires fewer switches and auxiliary devices. In addition, a lesser number of on-state switches for the synthesis of each voltage level results in less conduction losses, which enhances the converter efficiency. The proposed structure is capable of being implemented in both symmetrical and asymmetrical topologies. This is a merit feature for the proposed topology, which produces high voltage levels with a limited number of elements. The proposed structure is controlled using the fundamental frequency control scheme. The proposed basic module consists of six unidirectional switches and five DC voltage sources, generating five positive voltage levels. The performance of the recommended topology is analyzed from the various circuitry parameters, and a comprehensive comparison carried out with similar recent structures. The presented comparison reveals the advantage of the recommended inverter from different aspects of the circuitry parameters. The suggested structure is simulated using Matlab/Simulink software, and its performance is validated using a laboratory prototype. The results are reported for various steady-state and dynamic conditions.

Parametric analysis of the effects of blade exit angle on the cavitation characteristics in a hydraulic torque converter

Hydraulic torque converters are prone to cavitation due to their high impeller rotational speeds and their complex three-dimensional flow characteristics. Since the blades are the core components of torque converters, the shapes of the blades are important to the hydraulic performance and cavitation characteristics. Different cavitation computational fluid dynamics (CFD) models for a torque converter were developed to simulate the internal cavitation flow for different pump and turbine blade exit angles, and the influence of the blade angles on the cavitation characteristics and cavitation flow field in the torque converter was investigated. Experimental prototypes were produced and tested for verification. The results indicate that the pump and turbine blade exit angles had significant effects on the cavitation number of the torque converter. Increasing the pump and turbine blade exit angles promotes the generation and intensification of cavitation, resulting in severe changes in the shapes and locations of the cavitation bubbles due to changes in the fluid impact angles. Additionally, cavitation is quickly suppressed and the performance is improved when the blade exit angles are reduced within an appropriate range, in particular, that of the turbine blade. These research results can provide guidance for the design of a high-performance hydraulic torque converter cascade system and the suppression of cavitation for practical engineering applications.

Design and analysis of an input‐series quasi‐resonant flyback high‐voltage SMPS based on an integrated transformer

An input-series quasi-resonant (QR) flyback high-voltage switching mode power supply (SMPS) based on an integrated transformer has been designed and analysed. It is capable of converting a high DC input voltage to lower DC voltage to power the control components of high-power converters in a DC microgrid. An integrated transformer, combined with identical duty cycle control, is adopted to achieve automatic equalization of the series modules effectively even without employing any voltage or current equalization control strategy, of which effect is analysed theoretically. The design of the control system, based on QR flyback SMPS is given, which is implemented by peak current control, and a DCM small-signal model for the designed SMPS is established, which indicates that the system has high stability and accuracy to ensure normal operation across a broad range of input voltages. Finally, the validity of the theoretical analysis and the proposed method is demonstrated by the development of a 48 W SMPS experimental prototype, which is composed of three input-series modules. The overall efficiency of the prototype has been improved due to the adoption of QR. The proposed design and analysis methods can be extended to other input-series isolated DC/DC topologies.

The application of the spectral domain modeling to the power take-off sizing of heaving wave energy converters

The power take-off (PTO) system is a main component in wave energy converters (WECs), and it accounts for a notable proportion in the total cost. Sizing the PTO capacity has been proven to be significant to the cost-effectiveness of WECs. In the numerical modeling, the PTO size is normally represented by a force constraint. Therefore, to accurately evaluate the power performance of WECs with various PTO sizes, it is necessary to take the PTO force limitation, a nonlinear effect, into consideration. In this paper, a computationally-efficient spectral domain model of the PTO force saturation is developed for a heaving point absorber, and the nonlinear term is included by statistical linearization. For comparison, a frequency domain and nonlinear time domain model are implemented, and the developed spectral model is verified with the results of the nonlinear time domain model. Compared with the frequency domain model, the spectral domain model remarkably reduces the relative errors in predicting the power performance of WECs with force constraints, while the computational demand is much lower than the nonlinear time domain model. Furthermore, a case study is conducted to size the PTO capacity for reducing the levelized cost of energy (LCOE) in a chosen wave site. Three different numerical models are applied respectively. The frequency domain model could lead to a misestimate of the optimal PTO capacity, with a maximum relative error on the prediction of the annual energy production (AEP) of 24%. In contrast, the spectral domain model indicates the same optimal PTO size with the time domain modeling, and its relative errors on the prediction of the AEP are within 4.3%.

Input Small-Signal Characteristics of Selected DC–DC Switching Converters

The main goal of this study was to derive small-signal models of the input characteristics of buck, boost, and flyback converters working in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The models presented in the paper were derived using the separation of variables approach and included the parasitic resistances of all converter components. The paper features a discussion about the limitations of the model accuracy. The presented characteristics were obtained by calculation and verified by measurements. The input characteristics of converters are essential in the design of converters used in Power Factor Correction systems as well as in maximum power point tracking systems (MPPT).

Fault Diagnosis for Power Transistors in a Converter of Switched Reluctance Motors Based on Current Features

Fault diagnosis technique is necessary for high reliability system. For switched reluctance motor, asymmetric half bridge converter is the most commonly used. The transistor is the most fragile component in converters. To the transistor in asymmetric half bridge converter, a fault diagnosis method is proposed in this paper. When faults of transistors occur, the conducting loop will be changed. The current slope can reflect the change of the conducting loop. Through reconfiguring current sensors, the sign of the measurements will reverse with the change of the conducting loop. By the current slope and the sign of the measurements, present conducting loop is determined. The changes and the fault types are one-to-one correspondence. Therefore, the fault type is known. Conditions that may lead to misdiagnosis are illustrated and avoided in online execution. Comparisons of the proposed fault diagnosis method and relevant existing methods are made according to the cost, the response speed, the application scope and so on. The proposed fault diagnosis method is demonstrated under all possible fault types of the transistor by simulations and experiments, which validates effectiveness of it.

Resilient Control Of A Wave Energy Converter under PTO Fault Conditions

Due to ocean wave resource characteristics, wave energy converter (WEC) components are required to bear peak loads (i.e., torques, forces, and powers) that can cause component degradation and breakdown. In addition, any failure of a switching element (MOSFET or IGBT) in the power electronics drive for the Power Take-Off (PTO), or a malfunction of a pump or hose in the hydraulics can cause a PTO failure. In this study, a wave energy converter with two PTOs is designed to simulate the condition where one of the PTOs may fail to operate. A Reinforcement Learning (RL) based control strategy is proposed to deal with PTO failures since they are model-free algorithms and can adapt their policy to a changing environment. Results prove the adaptability of the proposed control model to the condition where one PTO fails to generate power. In winter sea conditions, before the fault, the WEC with two PTOs generates 255.1 kW and at the time of 9.9 104 s, the PTO fault happens and the mean power drops to 223.4 kW. After fault, the RL-based control retrains its policy and generates 247.3 kW

Power Density Boosting Techniques for Reconfigurable Integrated Modular Motor Drives

The electric drive power density and fault tolerance capability are of fundamental importance in many applications such as aerospace and traction applications. The modularization and the physical integration of the electric motor and the power converter components can lead to a high power density and a high fault tolerance drive system. The power density of a highly modular and integrated drive based on an axial flux permanent magnet synchronous machine and GaN converter is investigated in this paper. Several power density boosting techniques are provided and investigated using CFD simulations. These techniques incorporate optimization of the converter topology, the geometry of the shared cooling structure of the electric machine and the power converter and optimal selection of the materials in the path of heat transfer from the machine and the power converter to the cooling ambient. The power density of the reference integrated design is increased from 1.12 kW/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$l$</tex-math></inline-formula> to 2.14 kW/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$l$</tex-math></inline-formula> . The CFD computations are validated by extensive measurements on a modular integrated setup.

Reliability Evaluation of Isolated Buck-Boost DC-DC Series Resonant Converter

This paper investigates the reliability of an isolated buck-boost DC-DC converter (IBBC) based on the configuration of a series resonant converter (SRC). Two approaches are employed to predict the IBBC reliability, which are based on the MIL-HDBK-217F handbook and FIDES guide. The latter approach can take into account how the failure rate of the converter components based on the physics of failure is influenced by a varying yearly mission profile. To do this, the thermal loading of each IBBC component is obtained, taking into account the photovoltaic (PV) mission profile of the solar irradiance and ambient temperature. In such a case, the PV module is operating at the maximum power point (MPP) and the IBBC transfers this power into the DC microgrid (MG). Second, the component-level failure rate is calculated with both reliability assessment approaches, to evaluate the converter-level failure rate. Therefore, the converter reliability can be defined while taking the serial reliability connection of the converter components into account. The reliability analysis is carried out using a cloud Python engine installed and running in a Google Colaboratory notebook. The results indicate that the primary semiconductors are the most vulnerable component in the IBBC. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$B_{10}$</tex-math></inline-formula> lifetime of the case-study IBBC calculated using the MIL-HDBK-217F and FIDES approaches is 14.80 and 23.20 years, respectively. This indicates that, when compared to the methodology from the MIL-HDBK-217F handbook, the approach from the FIDES guide can provide a more accurate prediction for the IBBC lifespan considering the real field mission profile.