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Multilevel power converters
(2011-12-01)
Khomfoi, Surin
;
Tolbert, Leon M.
This chapter demonstrates the state of the art of multilevel power converter technology, discussing fundamental multilevel converter structures and modulation paradigms. A multilevel converter not only achieves high power ratings but also enables the use of renewable energy sources. A multilevel converter has several advantages over a conventional two-level converter that uses high switching frequency pulse width modulation (PWM). Multilevel converters produce smaller CM voltage and can draw input current with low distortion. Existing multilevel converters such as diode-clamped and capacitor-clamped multilevel converters can be derived from the generalized converter topology called P2 topology. To reduce the number of separate dc sources for high-voltage, high-power applications with multilevel converters, diode clamped or capacitor-clamped converters can be used to replace the full-bridge cell in a cascaded converter. Two multilevel converters can be connected in a back-to-back arrangement, and then the combination can be connected to the electrical system in a series-parallel arrangement. © 2011 Elsevier Inc. All rights reserved.
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A hybrid cascaded multilevel inverter application for renewable energy resources including a reconfiguration technique
(2010-12-20)
Khomfoi, Surin
;
Praisuwanna, Nattapat
;
Tolbert, Leon M.
A hybrid cascaded multilevel inverter application for renewable energy resources including a reconfiguration technique is developed. The objective of this research is to propose an alternative topology of hybrid cascaded multilevel inverter applied to a low voltage dc microgrid in telecommunication buildings. The modified PWM technique is also developed to reduce switching losses. Also, the proposed topology can reduce the number of required power switches compared to a traditional cascaded multilevel inverter. A possible reconfiguration technique after faulty condition is also discussed. PSIM (PowerSim) and Simulink/MATLAB are used to simulate the circuit operation and control signal. A 3-kW prototype is developed. The switching losses of the proposed multilevel inverter are also investigated. By using the modified PWM technique and reconfiguration method, the proposed hybrid inverter can improve system efficiency and reliability. The proposed inverter efficiency is 97% under tested condition. The results show that proposed hybrid inverter topology is a promising method for a low voltage dc microgrid interfacing with renewable energy resources. © 2010 IEEE.
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Multilevel Power Converters
(2010-01-01)
Khomfoi, Surin
;
Tolbert, Leon M.
This chapter demonstrates the state of the art of multilevel power converter technology, discussing fundamental multilevel converter structures and modulation paradigms. A multilevel converter not only achieves high power ratings but also enables the use of renewable energy sources. A multilevel converter has several advantages over a conventional two-level converter that uses high switching frequency pulse width modulation (PWM). Multilevel converters produce smaller CM voltage and can draw input current with low distortion. Existing multilevel converters such as diode-clamped and capacitor-clamped multilevel converters can be derived from the generalized converter topology called P2 topology. To reduce the number of separate dc sources for high-voltage, high-power applications with multilevel converters, diode clamped or capacitor-clamped converters can be used to replace the full-bridge cell in a cascaded converter. Two multilevel converters can be connected in a back-to-back arrangement, and then the combination can be connected to the electrical system in a series-parallel arrangement.
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Hybrid cascaded multilevel inverter with PWM control method
(2008-09-29)
Liu, Haiwen
;
Tolbert, Leon M.
;
Khomfoi, Surin
;
Ozpineci, Burak
;
Du, Zhong
A hybrid cascaded multilevel inverter with PWM method is presented in this paper. It consists of a standard 3-leg inverter (one leg for each phase) and H-bridge in series with each inverter leg. It can use only a single DC power source to supply a standard 3-leg inverter along with three full H-bridges supplied by capacitors. Multilevel carrier-based PWM method is used to produce a five-level phase voltage. The inverter can be used in hybrid electric vehicles (HEV) and electric vehicles (EV). A simulation model based on PSIM and MATLAB/SIMULINK is developed. An experimental 5 kW prototype inverter is built and tested. The results experimentally validate the proposed PWM hybrid cascaded multilevel inverter. ©2008 IEEE.
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Fault diagnosis and reconfiguration for multilevel inverter drive using AI-based techniques
(2007-12-01)
Khomfoi, Surin
;
Tolbert, Leon M.
A fault diagnostic and reconfiguration method for a cascaded H-bridge multilevel inverter drive (MLID) using artificial-intelligence-based techniques is proposed in this paper. Output phase voltages of the MLID are used as diagnostic signals to detect faults and their locations. It is difficult to diagnose an MLID system using a mathematical model because MLID systems consist of many switching devices and their system complexity has a nonlinear factor. Therefore, a neural network (NN) classification is applied to the fault diagnosis of an MLID system. Multilayer perceptron networks are used to identify the type and location of occurring faults. The principal component analysis is utilized in the feature extraction process to reduce the NN input size. A lower dimensional input space will also usually reduce the time necessary to train an NN, and the reduced noise can improve the mapping performance. The genetic algorithm is also applied to select the valuable principal components. The proposed network is evaluated with simulation test set and experimental test set. The overall classification performance of the proposed network is more than 95%. A reconfiguration technique is also proposed. The proposed fault diagnostic system requires about six cycles to clear an open-circuit or short-circuit fault. The experimental results show that the proposed system performs satisfactorily to detect the fault type, fault location, and reconfiguration. © 2007 IEEE.
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Elimination of harmonics in a five-level diode-clamped multilevel inverter using fundamental modulation
(2007-12-01)
Ozdemir, Sule
;
Ozdemir, Engin
;
Tolbert, Leon M.
;
Khomfoi, Surin
In this study, elimination of harmonics in a fivelevel diode-clamped multilevel inverter (DCMLI) has been implemented by using fundamental modulation switching. The proposed method eliminates harmonics by generating negative harmonics with switching angles calculated for selective harmonic elimination method. In order to confirm the proposed method, first Matlab/Simulink and FSIM simulation results are given. Then the proposed method is also validated by experiments with Opal-RT controller and a 10 kW threephase, five-level DCMLI prototype. © 2007 IEEE.
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Fault detection and reconfiguration technique for cascaded H-bridge 11-level inverter drives operating under faulty condition
(2007-12-01)
Khomfoi, Surin
;
Tolbert, Leon M.
A fault detection and reconfiguration technique for a cascaded H-bridge 11-level inverter drives during faulty condition is proposed in this paper. The ability of cascaded H-bridge multilevel inverter drives (MLID) to operate under faulty condition is also discussed. Output phase voltages of a MLID can be used as a diagnostic signal to detect faults and their locations. AI-based techniques are used to perform the fault classification. A neural network (NN) classification is applied to the fault diagnosis of a MLID system. Multilayer perceptron (MLP) networks are used to identify the type and location of occurring faults. The principal component analysis (PCA) is utilized in the feature extraction process to reduce the NN input size. The genetic algorithm (GA) is also applied to select the valuable principal components to train the NN. A reconfiguration technique is also developed. The developed system is validated with simulation and experimental results. The developed fault diagnostic system requires about 6 cycles (∼100 ms at 60 Hz) to clear an open circuit and about 9 cycles (∼150 ms at 60 Hz) to clear a short circuit fault. The experiment and simulation results are in good agreement with each other, and the results show that the developed system performs satisfactorily to detect the fault type, fault location, and reconfiguration. © 2007 IEEE.

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