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Tohid Rahimi
Key Laboratory of Power System Intelligent Dispatch and Control, School of Electrical Engineering, Shandong University, Ministry of Education, Jinan, China

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Journal article
Published: 16 July 2021 in IEEE Access
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In this paper, to solve the hard-switching operation problem and the lack of existing a bidirectional power flow path from output to the energy storage device of the conventional three-port converter, a new soft-switched bidirectional multi-port converter is proposed. A large number of switches, different power flow paths which vary in each operating mode, and changing the outputs and their power levels are some of the challenges to provide soft-switching conditions in multi-port converters. In the proposed converter, by changing the topology of the conventional three-port converter, the bidirectional power exchangeability between ports is provided. Moreover, a soft-switching cell is added, which can operate independently from the output power levels. Less number of components with low volume is one of the important features of this multi-port converter. Due to the soft-switching operation of the proposed converter, the size of passive components and heat-sink is reduced. In addition, by the use of coupled inductors in the soft-switching cell, only one magnetic core is used and thus, single-stage power conversion is achieved and conduction loss is reduced. In this paper, the converter operating modes are presented, and design considerations are discussed. Finally, a 200 W–200 V prototype is implemented, and the theoretical analysis is validated by the experimental results.

ACS Style

Rasoul Faraji; Lei Ding; Tohid Rahimi; Hosein Farzanehfard; Hossein Hafezi; Mohammad Maghsoudi. Efficient Multi-Port Bidirectional Converter With Soft-Switching Capability for Electric Vehicle Applications. IEEE Access 2021, 9, 107079 -107094.

AMA Style

Rasoul Faraji, Lei Ding, Tohid Rahimi, Hosein Farzanehfard, Hossein Hafezi, Mohammad Maghsoudi. Efficient Multi-Port Bidirectional Converter With Soft-Switching Capability for Electric Vehicle Applications. IEEE Access. 2021; 9 ():107079-107094.

Chicago/Turabian Style

Rasoul Faraji; Lei Ding; Tohid Rahimi; Hosein Farzanehfard; Hossein Hafezi; Mohammad Maghsoudi. 2021. "Efficient Multi-Port Bidirectional Converter With Soft-Switching Capability for Electric Vehicle Applications." IEEE Access 9, no. : 107079-107094.

Short communication
Published: 20 June 2021 in Case Studies in Thermal Engineering
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In many industrial applications, parallel connection of power semiconductor switches is widely used to achieve higher power levels and fault-tolerant operation. But there is a current imbalance between parallel connected switches in practical applications. In this research, the impact of unbalanced currents on the junction temperature and the reliability of parallel connected switches are quantified and analyzed. Markov based reliability model is developed for quantitative assessment of reliability for parallel switches under different current sharing. The Mean Time to Failure (MTTF) is calculated for different conditions to be used as reliability metric for comparison of various conditions. A sensitivity analysis is also presented to show the effect of parameter variation on the junction temperatures of devices and reliability of the system. At last, a downscaled setup has been built up and tested. Experimental results verify the theoretical analysis and confirm procedure. Also, junction temperatures of power semiconductor devices are measured using thermal camera.

ACS Style

Tohid Rahimi; Lei Ding; Armin Abadifard; Pedram Ghavidel; Masoud Farhadi; Rasoul Faraji. Unbalanced currents effect on the thermal characteristic and reliability of parallel connected power switches. Case Studies in Thermal Engineering 2021, 26, 101134 .

AMA Style

Tohid Rahimi, Lei Ding, Armin Abadifard, Pedram Ghavidel, Masoud Farhadi, Rasoul Faraji. Unbalanced currents effect on the thermal characteristic and reliability of parallel connected power switches. Case Studies in Thermal Engineering. 2021; 26 ():101134.

Chicago/Turabian Style

Tohid Rahimi; Lei Ding; Armin Abadifard; Pedram Ghavidel; Masoud Farhadi; Rasoul Faraji. 2021. "Unbalanced currents effect on the thermal characteristic and reliability of parallel connected power switches." Case Studies in Thermal Engineering 26, no. : 101134.

Journal article
Published: 19 May 2021 in IEEE Access
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Due to the high penetration of renewable energy resources in microgrids (MGs), the grid inertia becomes low which leads to the grid to be vulnerable to large disturbances. The energy storage devices can play an important role to enhance the inertia of MGs. However, due to the high investment cost of storages or their dp/dt limitation, the installed energy storages cannot cover the challenge of high df/dt . A prominent solution to solve the problem is to use the inertia response of the wind generators. However, relatively high second frequency nadir is the main drawback of using the inertia response of the wind generators which may impose an extensive disturbance to MGs. Accordingly, a coordinated operation strategy for MGs between wind generator and hybrid energy storage (HES) system is proposed in this paper. In addition, to improve the inertia response of the MG; providing high-quality communication infrastructures with low delay and increasing the Ultracapacitor capacity have been paid attention. In this paper, the costs of the installed Ultracapacitor and quality of communication services are defined as the operation cost. Guaranteeing enough frequency damping for the MG with low operation cost are two conflict objectives. Therefore, a multi-objective optimization method is used to set the controllers’ values and reduce the operation cost. The results confirmed that the effectiveness of the proposed strategy to control hybrid power storage in coordination with the wind generator and the frequency recovery process is improved. Also, employing the optimum values guaranteed the frequency damping effectively with low operation cost. The Integral Absolute Error (IAE) value and operation cost are reduced by 13.6% and 32%, respectively. Also, the simulation results show that the maximum MG frequency deviation and maximum df/dt is well compatible with different standards in the presence of load perturbations and different wind speeds.

ACS Style

Tohid Rahimi; Lei Ding; Mostafa Kheshti; Rasoul Faraji; Josep M. Guerrero; Gibran David Agundis Tinajero. Inertia Response Coordination Strategy of Wind Generators and Hybrid Energy Storage and Operation Cost-Based Multi-Objective Optimizing of Frequency Control Parameters. IEEE Access 2021, 9, 74684 -74702.

AMA Style

Tohid Rahimi, Lei Ding, Mostafa Kheshti, Rasoul Faraji, Josep M. Guerrero, Gibran David Agundis Tinajero. Inertia Response Coordination Strategy of Wind Generators and Hybrid Energy Storage and Operation Cost-Based Multi-Objective Optimizing of Frequency Control Parameters. IEEE Access. 2021; 9 ():74684-74702.

Chicago/Turabian Style

Tohid Rahimi; Lei Ding; Mostafa Kheshti; Rasoul Faraji; Josep M. Guerrero; Gibran David Agundis Tinajero. 2021. "Inertia Response Coordination Strategy of Wind Generators and Hybrid Energy Storage and Operation Cost-Based Multi-Objective Optimizing of Frequency Control Parameters." IEEE Access 9, no. : 74684-74702.

Journal article
Published: 28 April 2021 in IEEE Access
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In this paper, a new high efficiency soft-switching non-isolated three-port converter (TPC) is proposed. In the conventional TPC, three switches are required to process power in different directions between inputs and output. Providing soft-switching condition for all switches using a low number of auxiliary components is a challenging task. In this paper, the conventional TPC topology is modified by changing its structure and adding a simple auxiliary circuit such that all switches operate under soft-switching condition in all operating modes. To reduce the volume of the converter, the magnetic components are integrated using a coupled inductor in the auxiliary soft-switching cell. In this paper, various converter operating modes are presented, and design considerations are discussed. Finally, a prototype 200 W, 100 V converter is implemented in the laboratory, and the theoretical analysis is validated by the experimental results.

ACS Style

Rasoul Faraji; Lei Ding; Tohid Rahimi; Mostafa Kheshti; Rabiul Islam. Soft-Switched Three-Port DC-DC Converter With Simple Auxiliary Circuit. IEEE Access 2021, 9, 66738 -66750.

AMA Style

Rasoul Faraji, Lei Ding, Tohid Rahimi, Mostafa Kheshti, Rabiul Islam. Soft-Switched Three-Port DC-DC Converter With Simple Auxiliary Circuit. IEEE Access. 2021; 9 ():66738-66750.

Chicago/Turabian Style

Rasoul Faraji; Lei Ding; Tohid Rahimi; Mostafa Kheshti; Rabiul Islam. 2021. "Soft-Switched Three-Port DC-DC Converter With Simple Auxiliary Circuit." IEEE Access 9, no. : 66738-66750.

Journal article
Published: 14 December 2020 in IEEE Transactions on Power Electronics
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Employing interleaved techniques in dc-dc converters provides fault-tolerant capability to the faulted switches of the converter. In the case of one phase failure, the other phases can continue operating. However, in interleaved topologies, if the output power is maintained at the desired constant value for post-fault conditions, there is a saturation risk of inductors. In this letter, a post-fault reconfiguration process for the three-phase interleaved dc-dc converter is proposed, which guarantees the operation of the inductor without saturation risk after power switch failures. The reconfiguration steps do not require isolating the inductor of the corresponding faulty phase. Experimental results of the presented converter verify the operation of the inductor without saturation and the effectiveness of the proposed strategy.

ACS Style

Tohid Rahimi; Lei Ding; Rasoul Faraji; Mostafa Kheshti; Josep Pou. Performance Improvement of a Three-Phase Interleaved DC–DC Converter Without Requiring Antisaturation Control for Postfault Conditions. IEEE Transactions on Power Electronics 2020, 36, 7378 -7383.

AMA Style

Tohid Rahimi, Lei Ding, Rasoul Faraji, Mostafa Kheshti, Josep Pou. Performance Improvement of a Three-Phase Interleaved DC–DC Converter Without Requiring Antisaturation Control for Postfault Conditions. IEEE Transactions on Power Electronics. 2020; 36 (7):7378-7383.

Chicago/Turabian Style

Tohid Rahimi; Lei Ding; Rasoul Faraji; Mostafa Kheshti; Josep Pou. 2020. "Performance Improvement of a Three-Phase Interleaved DC–DC Converter Without Requiring Antisaturation Control for Postfault Conditions." IEEE Transactions on Power Electronics 36, no. 7: 7378-7383.

Journal article
Published: 26 May 2019 in Energies
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Frequency stability is an important issue for the operation of islanded microgrids. Since the upstream grid does not support the islanded microgrids, the power control and frequency regulation encounter serious problems. By increasing the penetration of the renewable energy sources in microgrids, optimizing the parameters of the load frequency controller plays a great role in frequency stability, which is currently being investigated by researchers. The status of loads and generation sources are received by the control center of a microgrid via a communication system and the control center can regulate the output power of renewable energy sources and/or power storage devices. An inherent delay in the communication system or other parts like sensors sampling rates may lead microgrids to have unstable operation states. Reducing the delay in the communication system, as one of the main delay origins, can play an important role in improving fluctuation mitigation, which on the other hand increases the cost of communication system operation. In addition, application of ultra-capacitor banks, as a virtual inertial tool, can be considered as an effective solution to damp frequency oscillations. However, when the ultra-capacitor size is increased, the virtual inertia also increases, which in turn increases the costs. Therefore, it is essential to use a suitable optimization algorithm to determine the optimum parameters. In this paper, the communication system delay and ultra-capacitor size along with the parameters of the secondary controller are obtained by using a Non-dominated Sorting Genetic Algorithm II (NSGA-II) algorithm as well as by considering the costs. To cover frequency oscillations and the cost of microgrid operation, two fitness functions are defined. The frequency oscillations of the case study are investigated considering the stochastic behavior of the load and the output of the renewable energy sources.

ACS Style

Gholam Ali Alizadeh; Tohid Rahimi; Mohsen Hasan Babayi Nozadian; Sanjeevikumar Padmanaban; Zbigniew Leonowicz. Improving Microgrid Frequency Regulation Based on the Virtual Inertia Concept while Considering Communication System Delay. Energies 2019, 12, 2016 .

AMA Style

Gholam Ali Alizadeh, Tohid Rahimi, Mohsen Hasan Babayi Nozadian, Sanjeevikumar Padmanaban, Zbigniew Leonowicz. Improving Microgrid Frequency Regulation Based on the Virtual Inertia Concept while Considering Communication System Delay. Energies. 2019; 12 (10):2016.

Chicago/Turabian Style

Gholam Ali Alizadeh; Tohid Rahimi; Mohsen Hasan Babayi Nozadian; Sanjeevikumar Padmanaban; Zbigniew Leonowicz. 2019. "Improving Microgrid Frequency Regulation Based on the Virtual Inertia Concept while Considering Communication System Delay." Energies 12, no. 10: 2016.

Journal article
Published: 27 December 2018 in Applied Sciences
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Interleaved dc-dc converters in sensitive applications necessitate an enhanced reliability. An interleaved converter equipped with redundant components can fulfill the reliability requirements. Mean Time to Failure (MTTF), as a reliability index, can be used to evaluate the expected life span of the mentioned converters. The Markov model is a helpful tool to calculate the MTTF in such systems. Different scientific reports denote different failure rates with different weight for power elements. Also, in reliability reports, failure rates of active and passive components are uncertain values. In order to approximate the failure rates fuzzy-logic-based Markov models are proposed in this paper. Then it is used to evaluate the MTTF of an interleaved multi-phase dc-dc converter, which is equipped with parallel and standby switch configurations. For the first time, fuzzy curves for MTTFs of the converters and 3D reliability function are derived in this paper. The reliability analyses give an insight to find the appropriate redundant-switch configurations for interleaved dc-dc converters under different conditions. Simulation and experimental results are provided to lend credence to the viability of the studied redundant-switch configurations in interleaved dc-dc boost converter.

ACS Style

Tohid Rahimi; Hossein Khoun Jahan; Frede Blaabjerg; Amir Sajjad Bahman; Seyed Hossein Hosseini. Fuzzy-Logic-Based Mean Time to Failure (MTTF) Analysis of Interleaved Dc-Dc Converters Equipped with Redundant-Switch Configuration. Applied Sciences 2018, 9, 88 .

AMA Style

Tohid Rahimi, Hossein Khoun Jahan, Frede Blaabjerg, Amir Sajjad Bahman, Seyed Hossein Hosseini. Fuzzy-Logic-Based Mean Time to Failure (MTTF) Analysis of Interleaved Dc-Dc Converters Equipped with Redundant-Switch Configuration. Applied Sciences. 2018; 9 (1):88.

Chicago/Turabian Style

Tohid Rahimi; Hossein Khoun Jahan; Frede Blaabjerg; Amir Sajjad Bahman; Seyed Hossein Hosseini. 2018. "Fuzzy-Logic-Based Mean Time to Failure (MTTF) Analysis of Interleaved Dc-Dc Converters Equipped with Redundant-Switch Configuration." Applied Sciences 9, no. 1: 88.

Research article
Published: 21 June 2018 in Transactions of the Institute of Measurement and Control
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This paper focuses on the reliability improvement of a three-phase interleaved DC-DC boost converter'. In this paper, a new reconfiguration and switching strategy is proposed. The basic principle of the proposed strategy is bypassing the faulty phase (faulty switch), thus, the other phases can share the responsibility of the faulty phase. Meanwhile, three redundant structures consisting of parallel, standby and series configurations of power switches are considered, which can improve the reliability of the converter. This paper uses Markov chain method to evaluate the reliability of the system. The feasibility of the proposed switching and fault management strategies are verified by simulation and experimental results.

ACS Style

Tohid Rahimi; Seyed Hossein Hosseini; Mehran Sabahi; Gevork B. Gharehpetian; Mehdi Abapour. Reliability evaluation of a fault-tolerant three-phase interleaved DC-DC boost converter. Transactions of the Institute of Measurement and Control 2018, 41, 1278 -1289.

AMA Style

Tohid Rahimi, Seyed Hossein Hosseini, Mehran Sabahi, Gevork B. Gharehpetian, Mehdi Abapour. Reliability evaluation of a fault-tolerant three-phase interleaved DC-DC boost converter. Transactions of the Institute of Measurement and Control. 2018; 41 (5):1278-1289.

Chicago/Turabian Style

Tohid Rahimi; Seyed Hossein Hosseini; Mehran Sabahi; Gevork B. Gharehpetian; Mehdi Abapour. 2018. "Reliability evaluation of a fault-tolerant three-phase interleaved DC-DC boost converter." Transactions of the Institute of Measurement and Control 41, no. 5: 1278-1289.

Research article
Published: 28 March 2016 in Advances in Materials Science and Engineering
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In the BLDC motor-drive system, the leakage current from a motor to a ground network and existence of high-frequency components of the DC link current are the most important factors that cause conducting interference. The leakage currents of the motors, flow through common ground, will interfere with other equipment because of the high density of electrical and electronic systems in the spacecraft and aircrafts. Moreover, generally there are common DC buses in the mentioned systems, which aggravate the problem. Function of the electric motor causes appearance of the high-frequency components in the DC link current, which can interfere with other subsystems. In this paper, the analysis of electromagnetic noise and presentation of the proposed method based on the frequency spectrum of the DC link current and the leakage current from the motor to the ground network are done. The proposed method presents a new process based on the filtering method to overcome EMI. To cover the requirement analysis, the Maxwell software is used.

ACS Style

Navid Mousavi; Tohid Rahimi; Homayoun Meshgin Kelk. Reduction EMI of BLDC Motor Drive Based on Software Analysis. Advances in Materials Science and Engineering 2016, 2016, 1 -9.

AMA Style

Navid Mousavi, Tohid Rahimi, Homayoun Meshgin Kelk. Reduction EMI of BLDC Motor Drive Based on Software Analysis. Advances in Materials Science and Engineering. 2016; 2016 ():1-9.

Chicago/Turabian Style

Navid Mousavi; Tohid Rahimi; Homayoun Meshgin Kelk. 2016. "Reduction EMI of BLDC Motor Drive Based on Software Analysis." Advances in Materials Science and Engineering 2016, no. : 1-9.

Conference paper
Published: 01 February 2015 in The 6th Power Electronics, Drive Systems & Technologies Conference (PEDSTC2015)
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In this paper, different methods to overcome electromagnetic interference (EMI) result from DC-DC converter, are discussed. Hard, soft and soft-chaotic switching is simulated and EMI spectrums at all of switching type are analyzed. These switching methods are applicable in satellite EPS. But high reliability and low EMI features are two important factors for satellite application so it is essential to the researchers introduce high reliability and low EMI satellite EPS. In this paper, a high reliability EPS topology is selected and a new high reliability and low ripple boost converter are introduced that are using in EPS structure. The proposed converter has high reliability and low ripple input current but cannot reduce EMI in high frequency effectively.

ACS Style

Tohid Rahimi; S. Hossein Hosseini. EMI consideration of high reliability electrical power subsystem (EPS) of satellite. The 6th Power Electronics, Drive Systems & Technologies Conference (PEDSTC2015) 2015, 412 -417.

AMA Style

Tohid Rahimi, S. Hossein Hosseini. EMI consideration of high reliability electrical power subsystem (EPS) of satellite. The 6th Power Electronics, Drive Systems & Technologies Conference (PEDSTC2015). 2015; ():412-417.

Chicago/Turabian Style

Tohid Rahimi; S. Hossein Hosseini. 2015. "EMI consideration of high reliability electrical power subsystem (EPS) of satellite." The 6th Power Electronics, Drive Systems & Technologies Conference (PEDSTC2015) , no. : 412-417.