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power-converters
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Model-based Reliability-Centered design of power electronics dominated microgrids
, Article 17th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2022, 12 June 2022 through 15 June 2022 ; 2022 ; 9781665412117 (ISBN) ; Blaabjerg, F ; Fotuhi Firuzabad, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
This paper proposes a model-based design approach for microgrids considering the aging of power electronic devices under different operating conditions. The proposed approach takes into account the physics of failure mechanisms in converter components as the failure prone devices in power systems. Furthermore, it considers the impacts of load profile on the aging of converter components and system performance. This approach facilitates accurate and optimized design of power electronic-based microgrids. According to this approach fragile links of power converters for a specified application can be identified. Moreover, the weakest converters based on their function in the microgrid can be...
Dissipation factor as a degradation indicator for electrolytic capacitors
, Article IEEE Journal of Emerging and Selected Topics in Power Electronics ; 2022 , Pages 1-1 ; 21686777 (ISSN) ; Peyghami, S ; Mokhtari, H ; Wang, H ; Blaabjerg, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Capacitors are one of the most critical components in power electronic converters, yet they are notoriously susceptible to failure. Avoiding unforeseen outages caused by capacitor failures is one of the most effective approaches to increase system availability. Therefore, a variety of methods have been proposed to monitor a capacitor health condition based on different degradation indicators. This paper proposes a new approach based on the accurate measurement of an electrolytic capacitor dissipation factor to detect its end-of-life. Since the dissipation factor is affected by both the capacitor resistance and capacitance simultaneously, it can provide more information about the health...
Hybrid modeling of quasi-resonant converters: A piecewise affine approach
, Article 13th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2022, 1 February 2022 through 3 February 2022 ; 2022 , Pages 448-454 ; 9781665420433 (ISBN) ; Tahami, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
DC-DC quasi-resonant converters (QRC) have the advantage of reducing switching losses and electromagnetic interference (EMI) which are the main disadvantages of high frequency power converters. The control and stabilization of these converters have always been a challenge. Traditionally, the dynamical model of the QRC is obtained using state space averaging followed by linearization about an operating point. The major flaw of this method is that state variables have large variations; thus, the linearized averaged model is not valid. Therefore, it is necessary to obtain a more precise model for the aim of stability analysis and controller design. Due to semiconductors switching, QRCs are...
Improved resonant converter for dynamic wireless power transfer employing a floating-frequency switching algorithm and an optimized coil shape
, Article IEEE Access ; Volume 10 , 2022 , Pages 56914-56924 ; 21693536 (ISSN) ; Tarzamni, H ; Tahami, F ; Kyyra, J ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
This paper offers a new EF-class converter for dynamic wireless power transfer application. The proposed high-frequency converter employs a floating-frequency switching algorithm to control the converter in a continuous frequency range, eliminate the requirement to any additional operational data from the secondary (receiver) side, accelerate the load impedance match while moving, maximize the transferred power rate, reduce charging interval and compensate power transfer tolerances. Moreover, an optimized super elliptical shape coil is designed to cope with lateral misalignment, enhance coil coupling, and increase efficiency. In the proposed converter, (i) soft switching is implemented to...
On-line condition monitoring system for dc-link capacitor of back-to-back converters using large-signal transients
, Article IEEE Journal of Emerging and Selected Topics in Power Electronics ; 2022 ; 21686777 (ISSN) ; Abdi, B ; Peyghami, S ; Mokhtari, H ; Blaabjerg, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
The increasing use of power electronic equipment and the importance of their continuous and correct operation have attracted remarkable attention to the condition monitoring of power electronic converters. Since capacitors are the leading cause of power electronic converters failure, this paper attempts to attain a solution to monitor the condition of the DC-link capacitor in a three-phase back-to-back converter using the stimulated measurable transients. The proposed method works based on the temporary change of switching logic and the measurement of the DC-link voltage and converter input phase current transients. By processing the measured signals, the capacitance of the capacitor is...
A hybrid control approach for LLC resonant converter
, Article 12th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2021, 2 February 2021 through 4 February 2021 ; 2021 ; 9780738111971 (ISBN) ; Tahami, F ; Barzkar, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this paper, a novel hybrid control approach is proposed to control the LLC resonant converter. Since the converter consists of both continuous variables and logical variables, it is intrinsically hybrid. Apart from that, because of fast dynamics of the converter and the fact that there is no closed form solution for discontinuous conduction modes (DCM), modeling and control of the LLC resonant converter is still a challenge. In the authors' previous work, a systematic model was proposed for the converter, the direct piecewise affine model. In this paper, an appropriate controller based on the proposed model is represented and the design procedure is discussed in details; the block diagram...
Simple innovative method for online condition monitoring of IGBTs in back-to-back converters
, Article 12th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2021, 2 February 2021 through 4 February 2021 ; 2021 ; 9780738111971 (ISBN) ; Mokhtari, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
The reliability of power electronic based converters has become increasingly important due to their wide-spread use in industry. An effective method to increase the availability of converters is to use condition monitoring systems for planning scheduled maintenances. This paper provides a method to monitor the condition of IGBTs in a back-to-back converter based on their on-state voltage measurement. Using the proposed system adds limited number of elements to the circuit but can be implemented independent from the converter. Considering the converter topology has made the proposed method applicable for condition monitoring of switches in different back-to-back converters. This advantage...
Design and implementation of an ADC-based real-time simulator along with an optimal selection of the switch model parameters
, Article Electrical Engineering ; Volume 103, Issue 5 , 2021 , Pages 2315-2325 ; 09487921 (ISSN) ; Zolghadri, M. R ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
The method for modeling switching converters plays a key role in real-time simulators. Associate discrete circuit (ADC) modeling technique is a commonly used method for modeling the switching converter. However, the optimal selection of the ADC-based switch model parameters has great importance in the accuracy of the real-time simulator. In this paper, the design of a real-time simulator for a switching power converter has been done, in which a novel method for detecting optimum values of the switch model parameters has been expressed. Particle swarm optimization (PSO) algorithm is used to find these optimum values using state-space analysis of the modeled circuit in the z-domain. The...
A new high step-up interleaved LLC converter
, Article 12th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2021, 2 February 2021 through 4 February 2021 ; 2021 ; 9780738111971 (ISBN) ; Beiranvand, R ; Zolghadri, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this study, a new LLC resonant converter for high-voltage high-power applications is introduced. The introduced power converter is a two-phase interleaved full-bridge based that uses a transformer with secondary and tertiary windings to obtain higher output voltage. Zero voltage switching (ZVS) at MOSFETs turn on and zero current switching (ZCS) for all the output diodes at turn off are achieved for a wide range of input voltage (100 V-200 V) and output power (200 W-1500 W) variations. Simulation results show a 95% peak efficiency. © 2021 IEEE
Reliability evaluation in microgrids with non-exponential failure rates of power units
, Article IEEE Systems Journal ; Volume 14, Issue 2 , 2020 , Pages 2861-2872 ; Fotuhi Firuzabad, M ; Blaabjerg, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This article explores the impacts of non-exponentially distributed failures on reliability of microgrids. Failure rate of some components such as power electronic converters is not constant, while they play a major role in microgrids. Consequently, their failure characteristics will affect the microgrid reliability. Hence, the conventional reliability evaluation approaches based on mean time to failure may introduce inaccurate inputs for decision making in planning and operation of microgrids. In this article, different approaches are employed for evaluating the reliability of microgrids with non-constant failure rates. The obtained results indicate that the system reliability remarkably...
Extending protection selectivity in low voltage DC microgrids using compensation gain and artificial line inductance
, Article Electric Power Systems Research ; Volume 188 , 2020 ; Vahidi, B ; Razani, R ; Nafisi, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Vulnerability of power electronic converters in DC microgrids in case of fault occurrence in DC cables necessitates using a fast fault detection and isolation scheme. In this paper, a modified, fast and selective protection scheme has been presented, which provides the required tripping of low voltage DC (LVDC) microgrids. This protection scheme has been developed based on the natural characteristics of the fault current, in which the first and second derivatives of the fault current have been employed to define thresholds for discriminating between faulted and non-faulted situations. To enhance fault detection capability of the protection scheme, definition of thresholds have been improved...
Analysis and reliability evaluation of a high step-up soft switching push-pull DC-DC converter
, Article IEEE Transactions on Reliability ; Volume 69, Issue 4 , 2020 , Pages 1376-1386 ; Babaei, E ; Panahandeh Esmaeelnia, F ; Dehghanian, P ; Tohidi, S ; Bannae Sharifian, M. B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
In this article, a new soft switching isolated push-pull dc-dc converter using a three-winding transformer is proposed. The proposed hybrid resonant and pulse width modulated converter employs a conventional push-pull structure in the primary side, a voltage doubler in the secondary side, and a bidirectional switch besides the transformer, altogether help offering a high efficiency over a wide range of input and output voltage signals with an unsophisticated fixed-frequency control mechanism. The primary-side switches are commutated under zero voltage switching with low switching current and the secondary-side diodes are commutated under zero current switching. In this article, we first...
An Extremely low ripple high voltage power supply for pulsed current applications
, Article IEEE Transactions on Power Electronics ; Volume 35, Issue 8 , 2020 , Pages 7991-8001 ; Mohsenzade, S ; Hadizade, A ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This article describes the development of an 18 kV, 30 kW power supply for a pulsed current load with the maximum current of 20 A and a di/dt equal to 100 A/μs. The achieved output ripple is less than 0.01%. In such a high level of precision, the most important issues are considerable difference between the instantaneous and average output powers, as well as insufficient reaction speed of the converter to the fast load change. Very low level of the voltage feedback and its sensitivity to the noise. The first issue necessitates a notable overdesign of the converter switches if the output voltage precision is dedicated to the converter. The second issue raises the problems relevant to...
Reinforcing fault ride through capability of grid forming voltage source converters using an enhanced voltage control scheme
, Article IEEE Transactions on Power Delivery ; Volume 34, Issue 5 , 2019 , Pages 1827-1842 ; 08858977 (ISSN) ; Mokhtari, H ; Ghasemi, M. A ; Blaabjerg, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Medium power distributed energy resources (DERs) are commonly connected to medium voltage distribution systems via voltage source converters (VSCs). Several guidelines and standards have been developed to establish the needed criteria and requirements for DERs interconnections. In this respect, it is preferred to reinforce the VSC fault ride through (FRT) capability, which considerably minimizes the DG outage period and reconnection time and results in a resilient system against short circuits. Considering the significant number of asymmetrical faults in distribution systems, the VSC response in such conditions must be investigated, and consequently, its FRT capability must be reinforced. In...
Failure mode, effects and criticality analysis (FMECA) in power electronic based power systems
, Article 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe, 3 September 2019 through 5 September 2019 ; 2019 ; 9789075815313 (ISBN) ; Davari, P ; F. Firuzabad, M ; Blaabjerg, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Power electronics is becoming an underpinning technology for modern power systems. Power converters are increasingly used in various applications implying different levels of importance in power systems. Hence, optimal decision-making for manufacturing, control, operation and maintenance of them requires understanding of their importance in the power systems. Furthermore, identifying the converters importance may be beneficial for simplifying the system-level reliability modeling in a large Power Electronic based Power Systems (PEPSs). Thereby, a Failure Mode, Effects and Criticality Analysis (FMECA) approach is proposed in this paper in order to figure out the importance of converters in...
A robust short-circuit fault diagnosis for high voltage DC power supply based on multisensor data fusion
, Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; 2019 , Pages 659-664 ; 9781538692547 (ISBN) ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Short-circuit fault (SCF) detection is mandatory in a high voltage DC power supply (HVPS) to prevent fatal damage. The majority of converters employ a single sensor to detect the SCF. This attribute increases the interference vulnerability of the fault detection (FD) system in the presence of noise. Therefore, miss detections and false alarms are possible to occur. Miss detections and false alarms are harmful catastrophes in most applications. A commonly used method to suppress the noise impacts is using a low-bandwidth low-pass filter. However, the use of the low-bandwidth low-pass filter reduces the speed of FD due to the filter delay. This paper proposes a fast FD algorithm based on...
A high voltage variable inductor LCC resonant converter with high power factor over wide load range
, Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; 2019 , Pages 279-284 ; 9781538692547 (ISBN) ; Ayoubi, R ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
High voltage power supplies (HVPS) are widely used to supply vacuum tubes. Regarding to their high efficiency, resonant converters are a choice of HVPS structure. In this application, HVPS is faced with wide variation of the load power. On the other hand, output voltage regulation over wide load range is essential. However, there are several problems dealing with resonant converters such as output voltage regulation and low-efficient performance in a light load. In this paper, a control scheme for a series-parallel resonant converter is presented. This scheme regulates the output voltage of the converter over load variation range. A variable inductor placed as the series inductor in the...
A fault-tolerant strategy for three-phase dual active bridge converter
, Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; 2019 , Pages 253-258 ; 9781538692547 (ISBN) ; Noroozi, N ; Zolghadri, M. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Due to several advantages, three-phase Dual Active Bridge (DAB) converter is widely used in numerous applications nowadays. On the other hand, this converter is very vulnerable to Transistor Open-Circuit Fault (TOCF). Therefore, a fault-tolerant (FT) scheme has been proposed in this paper to solve the problem. First, normal and faulty conditions are investigated, and according to the results, a fault-diagnosis (FD) approach is introduced. Using the outcomes of FD unit, a new post-fault strategy is proposed for the converter. The FD method is based on the DC component of transformer phase currents, and the basis of FT technique is shedding the faulty phase. Some benefits of the proposed...
A Comprehensive Time-domain-based Optimization of a High-Frequency LLC-based Li-ion Battery Charger
, Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; 2019 , Pages 415-420 ; 9781538692547 (ISBN) ; Tahami, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
The LLC resonant converter, as a promising solution for battery charger applications, has the ability to adjust its output voltage during Constant Current and Constant Voltage modes in the charging profile. However, its operation mode changes as switching frequency changes. Therefore, for efficiency-oriented optimizations in battery charger applications, the one-pointed efficiency is not an appropriate objective. To this end, in this paper, a multi-pointed averaged efficiency is considered for optimization along with the transformer volume. Another factor of a proper design for a wide output range LLC is the converter peak voltage gain that is calculated based on an accurate method. The...
Enhanced hybrid modular multilevel converter with improved reliability and performance characteristics
, Article IEEE Transactions on Power Electronics ; Volume 34, Issue 4 , 2019 , Pages 3139-3149 ; 08858993 (ISSN) ; Ravanji, M. H ; Parniani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This paper proposes an enhanced hybrid modular multilevel converter (MMC), which utilizes a combination of half-bridge submodules (HBSM) and at least one full-bridge submodule (FBSM). In the proposed structure, FBSMs work with half of the HBSMs nominal voltage in each arm. Due to the presence of FBSMs, HBSMs switching frequency drops significantly, which reduces the converter power loss compared to half-bridge based MMCs. Furthermore, because of redundant FBSMs, (2N + 1)-modulation can be employed to generate the output voltage without increasing the circulating current, thus, the converter performance is improved notably. Besides, with the redundant FBSMs, the converter can continue its...