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Analysis and Control of a Modular MV-to-LV Rectifier based on a Cascaded Multilevel Converter
Iman-Eini, Hossein,Farhangi, Shahrokh,Khakbazan-Fard, Mahboubeh,Schanen, Jean-Luc The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.2
In this paper a modular high performance MV-to-LV rectifier based on a cascaded H-bridge rectifier is presented. The proposed rectifier can directly connect to the medium voltage levels and provide a low-voltage and highly-stable DC interface with the consumer applications. The input stage eliminates the necessity for heavy and bulky step-down transformers. It corrects the input power factor and maintains the voltage balance among the individual DC buses. The second stage includes the high frequency parallel-output DC/DC converters which prepares the galvanic isolation, regulates the output voltage, and attenuates the low frequency voltage ripple ($2f_{line}$) generated by the first stage. The parallel-output converters can work in interleaving mode and the active load-current sharing technique is utilized to balance the load power among them. The detailed analysis for modeling and control of the proposed structure is presented. The validity and performance of the proposed topology is verified by simulation and experimental results.
A Fault-Tolerant Control Strategy for Cascaded H-Bridge Multilevel Rectifiers
Iman-Eini, Hossein,Farhangi, Shahrokh,Schanen, Jean-Luc,Khakbazan-Fard, Mahboubeh The Korean Institute of Power Electronics 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.1
Reliability is an important issue in cascaded H-bridge converters (CHB converters) because they use a high number of power semiconductors. A faulty power cell in a CHB converter can potentially lead to expensive downtime and great losses on the consumer side. With a fault-tolerant control strategy, operation can continue with the undamaged cells; thus increasing the reliability of the system. In this paper, the operating principles and the control method for a CHB multilevel rectifier are introduced. The influence of various faults on the CHB converter is investigated. The method of fault diagnosis and the bypassing of failed cells are explained. A fault-tolerant protection strategy is proposed to achieve redundancy in the CHB rectifier. The redundant H-bridge concept helps to deal with device failures and to increase system reliability. Simulation results verify the performance of the proposed strategy.
Analysis and Control of a Modular MV-to-LV Rectifier based on a Cascaded Multilevel Converter
Hossein Iman-Eini,Shahrokh Farhangi,Mahboubeh Khakbazan-Fard,Jean-Luc Schanen 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.2
In this paper a modular high performance MV-to-LV rectifier based on a cascaded H-bridge rectifier is presented. The proposed rectifier can directly connect to the medium voltage levels and provide a low-voltage and highly-stable DC interface with the consumer applications. The input stage eliminates the necessity for heavy and bulky step-down transformers. It corrects the input power factor and maintains the voltage balance among the individual DC buses. The second stage includes the high frequency parallel-output DC/DC converters which prepares the galvanic isolation, regulates the output voltage, and attenuates the low frequency voltage ripple (2fline) generated by the first stage. The parallel-output converters can work in interleaving mode and the active load-current sharing technique is utilized to balance the load power among them. The detailed analysis for modeling and control of the proposed structure is presented. The validity and performance of the proposed topology is verified by simulation and experimental results.
A Fault-Tolerant Control Strategy for Cascaded H-Bridge Multilevel Rectifiers
Hossein Iman-Eini,Shahrokh Farhangi,Jean-Luc Schanen,Mahboubeh Khakbazan-Fard 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.1
Reliability is an important issue in cascaded H-bridge converters (CHB converters) because they use a high number of power semiconductors. A faulty power cell in a CHB converter can potentially lead to expensive downtime and great losses on the consumer side. With a fault-tolerant control strategy, operation can continue with the undamaged cells; thus increasing the reliability of the system. In this paper, the operating principles and the control method for a CHB multilevel rectifier are introduced. The influence of various faults on the CHB converter is investigated. The method of fault diagnosis and the bypassing of failed cells are explained. A fault-tolerant protection strategy is proposed to achieve redundancy in the CHB rectifier. The redundant H-bridge concept helps to deal with device failures and to increase system reliability. Simulation results verify the performance of the proposed strategy.
Najjar, Mohammad,Iman-Eini, Hossein,Moeini, Amirhossein,Farhangi, Shahrokh The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
This paper proposes an improved low frequency Selective Harmonic Mitigation-PWM (SHM-PWM) technique. The proposed method mitigates the low order harmonics of the output voltage up to the $50^{th}$ harmonic well and satisfies the grid codes EN 50160 and CIGRE-WG 36-05. Using a modified criterion for the switching angles, the range of the modulation index for non-linear SHM equations is improved, without increasing the switching frequency of the CHB converter. Due to the low switching frequency of the CHB converter, mitigating the harmonics of the converter up to the $50^{th}$ order and finding a wider modulation index range, the size and cost of the passive filters can be significantly reduced with the proposed technique. Therefore, the proposed technique is more efficient than the conventional SHM-PWM. To verify the effectiveness of the proposed method, a 7-level Cascaded H-bridge (CHB) converter is utilized for the study. Simulation and experimental results confirm the validity of the above claims.
Developed MPPT Algorithm for Photovoltaic Systems without a Voltage Sensor
Momayyezan, Milad,Iman-Eini, Hossein The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.6
This paper presents a study of maximum power point tracking (MPPT) for photovoltaic arrays with only one current sensor. Initially, a review of MPPT methods with only a current sensor is performed with extension for a variety of dc/dc converters. Furthermore, the same topology is developed to achieve better performance in the presence of sensor offset and environmental noise. The proposed method is robust, cost effective, and behaves well dynamically and in the steady state. After a theoretical analysis of presented approach, its validity and effectiveness are verified by simulation and experimental results.
Moeini, Amirhossein,Iman-Eini, Hossein,Najjar, Mohammad The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1
In this paper, the Selective Harmonic Mitigation-PWM (SHM-PWM) method is used in single-phase and three-phase Cascaded H-Bridge (CHB) inverters in order to fulfill different power quality standards such as EN 50160, CIGRE WG 36-05, IEC 61000-3-6 and IEC 61000-2-12. Non-equal DC link voltages are used to increase the degrees of freedom for the proposed SHM-PWM technique. In addition, it will be shown that the obtained solutions become continuous and without sudden changes. As a result, the look-up tables can be significantly reduced. The proposed three-phase modulation method can mitigate up to the 50th harmonic from the output voltage, while each switch has just one switching in a fundamental period. In other words, the switching frequency of the power switches are limited to 50 Hz, which is the lowest switching frequency that can be achieved in the multilevel converters, when the optimal selective harmonic mitigation method is employed. In single-phase mode, the proposed method can successfully mitigate harmonics up to the 50th, where the switching frequency is 150 Hz. Finally, the validity of the proposed method is verified by simulations and experiments on a 9-level CHB inverter.
Najjar, Mohammad,Iman-Eini, Hossein,Moeini, Amirhossein The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
In this paper an improved low frequency selective harmonic elimination-PWM (SHE-PWM) technique for Cascaded H-bridge (CHB) converters is proposed. The proposed method is able to eliminate low order harmonics from the output voltage of the converter for a wide range of modulation indices. To solve SHE-PWM equations, especially for low modulation indices, a modified method is used which employs either the positive or negative voltage polarities of H-bridge cells to increase the freedom degrees of each cell. Freedom degrees of the switching angles are also used to increase the range of available solutions for non-linear SHE equations. The proposed SHE methods can successfully eliminate up to $25^{th}$ harmonic from a 7-level output voltage by using just nine switching transitions or a 150 Hz switching frequency. To confirm the validity of the proposed method, simulation and experimental results have been presented.
Mohammad Najjar,Hossein Iman-Eini,Amirhossein Moeini,Shahrokh Farhangi 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
This paper proposes an improved low frequency Selective Harmonic Mitigation-PWM (SHM-PWM) technique. The proposed method mitigates the low order harmonics of the output voltage up to the 50<SUP>th</SUP> harmonic well and satisfies the grid codes EN 50160 and CIGRE-WG 36–05. Using a modified criterion for the switching angles, the range of the modulation index for non-linear SHM equations is improved, without increasing the switching frequency of the CHB converter. Due to the low switching frequency of the CHB converter, mitigating the harmonics of the converter up to the 50<SUP>th</SUP> order and finding a wider modulation index range, the size and cost of the passive filters can be significantly reduced with the proposed technique. Therefore, the proposed technique is more efficient than the conventional SHM-PWM. To verify the effectiveness of the proposed method, a 7-level Cascaded H-bridge (CHB) converter is utilized for the study. Simulation and experimental results confirm the validity of the above claims.
Mohammad Najjar,Hossein Iman-Eini,Amirhossein Moeini 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
In this paper an improved low frequency selective harmonic elimination-PWM (SHE-PWM) technique for Cascaded H-bridge (CHB) converters is proposed. The proposed method is able to eliminate low order harmonics from the output voltage of the converter for a wide range of modulation indices. To solve SHE-PWM equations, especially for low modulation indices, a modified method is used which employs either the positive or negative voltage polarities of H-bridge cells to increase the freedom degrees of each cell. Freedom degrees of the switching angles are also used to increase the range of available solutions for non-linear SHE equations. The proposed SHE methods can successfully eliminate up to 25<SUP>th</SUP> harmonic from a 7-level output voltage by using just nine switching transitions or a 150 Hz switching frequency. To confirm the validity of the proposed method, simulation and experimental results have been presented.