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K Gopakumar - One of the best experts on this subject based on the ideXlab platform.
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a switched capacitive filter based harmonic elimination technique by generating a 30 sided Voltage Space Vector structure for im drive
IEEE Transactions on Power Electronics, 2020Co-Authors: R Rakesh, K Gopakumar, L Umanand, Krishna Raj Ramachandran, Apurv Kumar Yadav, Kouki MatsuseAbstract:This paper proposes a novel polygonal Voltage Space Vector structure (SVS) having 30 sides, for a star-connected induction motor drive. The SVS eliminates the presence of harmonics up to 25th order from motor phase Voltage throughout the entire modulation range, providing a torque profile devoid of lower order pulsations. Linear modulation is extended till 99.63% of base speed without exceeding the motor phase Voltage rating. Topology consists of a dc-link fed primary inverter and two equal low Voltage modular capacitor fed secondary inverters. Here the harmonics generated by the primary inverter is canceled by the secondary inverter which acts as a switched capacitive filter. Detailed description of the SVS generation and timing calculations are provided in this paper. Effectiveness of the proposed scheme is validated using experimental results, inverter loss calculations, and harmonic analysis.
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an induction motor drive scheme generating twenty four sided Voltage Space Vector structure with linear modulation range near to base speed
European Conference on Power Electronics and Applications, 2017Co-Authors: Raj R Krishna, K Gopakumar, Mathews Boby, Mariusz Malinowski, Marek JasinskiAbstract:In this paper, a drive scheme generating 24-sided polygonal Voltage Space Vector structure using an inverter topology with single DC source is proposed. A 24-sided structure eliminates dominant low order phase Voltage harmonics including and up to seventeenth and nineteenth orders throughout the speed range including step operation. The power circuit has a two-level inverter and two low Voltage cascaded H-bridge cells fed with capacitors. The linear modulation range is extended to 99.42% of the base speed with such a polygonal structure. A reduced PWM switching sequence resulting in minimum pole Voltage transitions for the two-level inverter and shifting relatively higher frequency operation to low Voltage H-Bridge inverters feature the drive scheme for controlling losses.
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a 24 sided Voltage Space Vector based im drive with low order harmonic elimination for the full speed range
IEEE Transactions on Industrial Electronics, 2017Co-Authors: Krishna Raj R, K Gopakumar, Mathews Boby, Mariusz Malinowski, Marek JasinskiAbstract:This paper proposes an inverter topology to generate a 24-sided polygonal Voltage Space Vector structure for variable speed drives using a single dc source. The topology consists of a two-level inverter cascaded with two low-Voltage floating capacitor-fed H-bridge cells. The 24-sided structure eliminates harmonics up to and including seventeenth and nineteenth orders from phase Voltage output resulting in a smooth torque profile over the entire speed range. This structure also enhances the linear modulation range to 99.42% of the base speed. A reduced switching sequence based pulse width modulation technique achieves minimum pole Voltage transitions for the two-level inverter, thereby controlling switching losses. The lower order harmonics are eliminated by switching action of low-Voltage H-bridge cells. Experimental results, simulation studies on inverter losses, and harmonic performance validate the effectiveness of proposed drive scheme.
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fifth and seventh order harmonic elimination with multilevel dodecagonal Voltage Space Vector structure for im drive using a single dc source for the full speed range
IEEE Transactions on Power Electronics, 2017Co-Authors: Mathews Boby, Sumit Pramanick, K Gopakumar, Sudharshan R Kaarthik, Arun Rahul S, L UmanandAbstract:This paper presents a method for generating a multilevel dodecagonal Voltage Space Vector structure using a single dc source for induction motor drives. Multilevel dodecagonal structure combines the advantages of both multilevel and dodecagonal structures, and hence, generates low d v /d t phase Voltage along with the elimination of fifth- and seventh-order harmonics over the entire modulation range. This eliminates low-order harmonic currents and prevents the generation of sixth-order torque ripple in the motor. The topology used requires only one dc source making four-quadrant operation of the drive system simpler compared to previously proposed multilevel topologies generating dodecagonal Space Vector structures. The topology used consists of a three-level flying capacitor (FC) inverter cascaded with a capacitor fed H-bridge. The FC inverter operates at a lower switching frequency and the low-order harmonics are eliminated by the switching action of the cascaded H-bridge inverter. The capacitors in the cascaded H-bridge modules are maintained at a substantially smaller Voltage compared to the dc-link Voltage and are inherently balanced during the pulsewidth modulation operation. This results in low switching loss, in the FC inverter as well as in the cascaded H-bridge inverter. Experimental results are included to validate the operation of the topology and modulation scheme presented in this paper.
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generation of higher number of Voltage levels by stacking inverters of lower multilevel structures with low Voltage devices for drives
IEEE Transactions on Power Electronics, 2017Co-Authors: Viju Nair R, Arun Rahul S, Sudharshan R Kaarthik, Abhijit Kshirsagar, K GopakumarAbstract:This paper proposes a new method of generating higher number of levels in the Voltage waveform by stacking multilevel converters with lower Voltage Space Vector structures. An important feature of this stacked structure is the use of low Voltage devices while attaining higher number of levels. This will find extensive applications in electric vehicles since direct battery drive is possible. The Voltages of all the capacitors in the structure can be controlled within a switching cycle using the switching state redundancies (pole Voltage redundancies). This helps in reducing the capacitor size. Also, the capacitor Voltages can be balanced irrespective of modulation index and load power factor. To verify the concept experimentally, a nine-level inverter is developed by stacking two five-level inverters and an induction motor is run using V/f control scheme. Both steady state and transient results are presented.
L Umanand - One of the best experts on this subject based on the ideXlab platform.
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a switched capacitive filter based harmonic elimination technique by generating a 30 sided Voltage Space Vector structure for im drive
IEEE Transactions on Power Electronics, 2020Co-Authors: R Rakesh, K Gopakumar, L Umanand, Krishna Raj Ramachandran, Apurv Kumar Yadav, Kouki MatsuseAbstract:This paper proposes a novel polygonal Voltage Space Vector structure (SVS) having 30 sides, for a star-connected induction motor drive. The SVS eliminates the presence of harmonics up to 25th order from motor phase Voltage throughout the entire modulation range, providing a torque profile devoid of lower order pulsations. Linear modulation is extended till 99.63% of base speed without exceeding the motor phase Voltage rating. Topology consists of a dc-link fed primary inverter and two equal low Voltage modular capacitor fed secondary inverters. Here the harmonics generated by the primary inverter is canceled by the secondary inverter which acts as a switched capacitive filter. Detailed description of the SVS generation and timing calculations are provided in this paper. Effectiveness of the proposed scheme is validated using experimental results, inverter loss calculations, and harmonic analysis.
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fifth and seventh order harmonic elimination with multilevel dodecagonal Voltage Space Vector structure for im drive using a single dc source for the full speed range
IEEE Transactions on Power Electronics, 2017Co-Authors: Mathews Boby, Sumit Pramanick, K Gopakumar, Sudharshan R Kaarthik, Arun Rahul S, L UmanandAbstract:This paper presents a method for generating a multilevel dodecagonal Voltage Space Vector structure using a single dc source for induction motor drives. Multilevel dodecagonal structure combines the advantages of both multilevel and dodecagonal structures, and hence, generates low d v /d t phase Voltage along with the elimination of fifth- and seventh-order harmonics over the entire modulation range. This eliminates low-order harmonic currents and prevents the generation of sixth-order torque ripple in the motor. The topology used requires only one dc source making four-quadrant operation of the drive system simpler compared to previously proposed multilevel topologies generating dodecagonal Space Vector structures. The topology used consists of a three-level flying capacitor (FC) inverter cascaded with a capacitor fed H-bridge. The FC inverter operates at a lower switching frequency and the low-order harmonics are eliminated by the switching action of the cascaded H-bridge inverter. The capacitors in the cascaded H-bridge modules are maintained at a substantially smaller Voltage compared to the dc-link Voltage and are inherently balanced during the pulsewidth modulation operation. This results in low switching loss, in the FC inverter as well as in the cascaded H-bridge inverter. Experimental results are included to validate the operation of the topology and modulation scheme presented in this paper.
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a multilevel inverter fed im drive with dodecagonal Voltage Space Vector structure using a single dc source with linear modulation range near to base speed
European Conference on Power Electronics and Applications, 2016Co-Authors: Mathews Boby, Sumit Pramanick, K Gopakumar, Arun S Rahul, L UmanandAbstract:A fifth and seventh order harmonic elimination scheme for IM drive with a multilevel dodecagonal Voltage Space Vector structure using a single DC source is proposed in this work. Single DC source requirement makes four quadrant operation of the drive system simpler compared to the multilevel do-decagonal structures presented in literatures before. The Space Vector structure consists of six concentric dodecagons, combining the advantages of multilevel operation as well as dodecagonal structure. The topology consists of a three-level flying capacitor (FC) inverter cascaded with a capacitor fed H-bridge (CHB) inverter. The FC inverter operating at high Voltage switches in a quasi-square wave mode whereas the CHB inverter operating at a lower Voltage switches at high frequency to remove the harmonics generated by the FC inverter. Switching losses are low, both in the FC and CHB inverters. Experiment results for open-loop V/f operation are included in this paper showing the effectiveness of the drive scheme.
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multilevel dodecagonal Voltage Space Vector structure generation for open end winding im using a single dc source
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Mathews Boby, Sumit Pramanick, K Gopakumar, Sudharshan R Kaarthik, Arun S Rahul, L UmanandAbstract:In this paper, a new inverter topology is proposed for generating a multilevel dodecagonal Voltage Space Vector structure for open-end winding induction motor (IM) using a single dc source. Dodecagonal Voltage Space Vector structure eliminates fifth- and seventh-order harmonic Voltages from phase Voltage output and hence eliminates the fifth- and seventh-order harmonic currents through the motor leading to removal of the dominant sixth-order torque ripple generation in the motor over the entire modulation range. Multilevel Space Vector structure generates output Voltage with better THD and low dv/dt. In the proposed topology, two three-level inverters drive an open-end winding IM, one inverter from each side. DC-link of primary inverter is from a dc source which delivers the entire active power, whereas the secondary inverter dc-link is maintained by a capacitor, which is self balanced during the inverter operation. The PWM scheme implemented ensures low switching frequency for primary inverter. Secondary inverter operates at a small dc-link Voltage. Hence, switching losses are small for both primary and secondary inverters. Experimental results show the elimination of fifth- and seventh-order harmonic Voltages over the entire modulation range, validating effectiveness of the proposed multilevel inverter scheme.
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a multilevel inverter system for an induction motor with open end windings
IEEE Transactions on Industrial Electronics, 2005Co-Authors: V T Somasekhar, K Gopakumar, K K Mohapatra, M R Baiju, L UmanandAbstract:In this paper, a multilevel inverter system for an open-end winding induction motor drive is described. Multilevel inversion is achieved by feeding an open-end winding induction motor with two two-level inverters in cascade (equivalent to a three-level inverter) from one end and a single two-level inverter from the other end of the motor. The combined inverter system with open-end winding induction motor produces Voltage Space-Vector locations identical to a six-level inverter. A total of 512 Space-Vector combinations are available in the proposed scheme, distributed over 91 Space-Vector locations. The proposed inverter drive scheme is capable of producing a multilevel pulsewidth-modulation (PWM) waveform for the phase Voltage ranging from a two-level waveform to a six-level waveform depending on the modulation range. A Space-Vector PWM scheme for the proposed drive is implemented using a 1.5-kW induction motor with open-end winding structure.
Sudharshan R Kaarthik - One of the best experts on this subject based on the ideXlab platform.
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fifth and seventh order harmonic elimination with multilevel dodecagonal Voltage Space Vector structure for im drive using a single dc source for the full speed range
IEEE Transactions on Power Electronics, 2017Co-Authors: Mathews Boby, Sumit Pramanick, K Gopakumar, Sudharshan R Kaarthik, Arun Rahul S, L UmanandAbstract:This paper presents a method for generating a multilevel dodecagonal Voltage Space Vector structure using a single dc source for induction motor drives. Multilevel dodecagonal structure combines the advantages of both multilevel and dodecagonal structures, and hence, generates low d v /d t phase Voltage along with the elimination of fifth- and seventh-order harmonics over the entire modulation range. This eliminates low-order harmonic currents and prevents the generation of sixth-order torque ripple in the motor. The topology used requires only one dc source making four-quadrant operation of the drive system simpler compared to previously proposed multilevel topologies generating dodecagonal Space Vector structures. The topology used consists of a three-level flying capacitor (FC) inverter cascaded with a capacitor fed H-bridge. The FC inverter operates at a lower switching frequency and the low-order harmonics are eliminated by the switching action of the cascaded H-bridge inverter. The capacitors in the cascaded H-bridge modules are maintained at a substantially smaller Voltage compared to the dc-link Voltage and are inherently balanced during the pulsewidth modulation operation. This results in low switching loss, in the FC inverter as well as in the cascaded H-bridge inverter. Experimental results are included to validate the operation of the topology and modulation scheme presented in this paper.
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generation of higher number of Voltage levels by stacking inverters of lower multilevel structures with low Voltage devices for drives
IEEE Transactions on Power Electronics, 2017Co-Authors: Viju Nair R, Arun Rahul S, Sudharshan R Kaarthik, Abhijit Kshirsagar, K GopakumarAbstract:This paper proposes a new method of generating higher number of levels in the Voltage waveform by stacking multilevel converters with lower Voltage Space Vector structures. An important feature of this stacked structure is the use of low Voltage devices while attaining higher number of levels. This will find extensive applications in electric vehicles since direct battery drive is possible. The Voltages of all the capacitors in the structure can be controlled within a switching cycle using the switching state redundancies (pole Voltage redundancies). This helps in reducing the capacitor size. Also, the capacitor Voltages can be balanced irrespective of modulation index and load power factor. To verify the concept experimentally, a nine-level inverter is developed by stacking two five-level inverters and an induction motor is run using V/f control scheme. Both steady state and transient results are presented.
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multilevel dodecagonal Voltage Space Vector structure generation for open end winding im using a single dc source
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Mathews Boby, Sumit Pramanick, K Gopakumar, Sudharshan R Kaarthik, Arun S Rahul, L UmanandAbstract:In this paper, a new inverter topology is proposed for generating a multilevel dodecagonal Voltage Space Vector structure for open-end winding induction motor (IM) using a single dc source. Dodecagonal Voltage Space Vector structure eliminates fifth- and seventh-order harmonic Voltages from phase Voltage output and hence eliminates the fifth- and seventh-order harmonic currents through the motor leading to removal of the dominant sixth-order torque ripple generation in the motor over the entire modulation range. Multilevel Space Vector structure generates output Voltage with better THD and low dv/dt. In the proposed topology, two three-level inverters drive an open-end winding IM, one inverter from each side. DC-link of primary inverter is from a dc source which delivers the entire active power, whereas the secondary inverter dc-link is maintained by a capacitor, which is self balanced during the inverter operation. The PWM scheme implemented ensures low switching frequency for primary inverter. Secondary inverter operates at a small dc-link Voltage. Hence, switching losses are small for both primary and secondary inverters. Experimental results show the elimination of fifth- and seventh-order harmonic Voltages over the entire modulation range, validating effectiveness of the proposed multilevel inverter scheme.
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timing calculations for a general n level dodecagonal Space Vector structure using only reference phase Voltages
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Sudharshan R Kaarthik, Carlo Cecati, I NagyAbstract:Multilevel inverters with dodecagonal (12-sided polygon) Voltage Space Vector (SV) structures have advantages like extension of linear modulation range, elimination of fifth and seventh harmonics in phase Voltages and currents for the full modulation range including extreme 12-step operation, reduced device Voltage ratings, lesser dv/dt stresses on devices and motor phase windings resulting in lower EMI/EMC problems, and lower switching frequency—making it more suitable for high-power drive applications. This paper proposes a simple method to obtain pulsewidth modulation (PWM) timings for a dodecagonal Voltage SV structure using only sampled reference Voltages. In addition to this, a carrier-based method for obtaining the PWM timings for a general N-level dodecagonal structure is proposed in this paper for the first time. The algorithm outputs the triangle information and the PWM timing values which can be set as the compare values for any carrier-based hardware PWM module to obtain SV PWM like switching sequences. The proposed method eliminates the need for angle estimation, computation of modulation indices, and iterative search algorithms that are typical in multilevel dodecagonal SV systems. The proposed PWM scheme was implemented on a five-level dodecagonal SV structure. Exhaustive simulation and experimental results for steady-state and transient conditions are presented to validate the proposed method.
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a Voltage Space Vector diagram formed by nineteen concentric dodecagons for medium Voltage induction motor drive
IEEE Transactions on Industrial Electronics, 2015Co-Authors: Sudharshan R Kaarthik, K Gopakumar, Carlo Cecati, I NagyAbstract:In this paper, a multilevel dodecagonal Voltage Space Vector structure with nineteen concentric dodecagons is proposed for the first time. This Space Vector structure is achieved by cascading two sets of asymmetric three-level inverters with isolated H-bridges on either side of an open-end winding induction motor. The dodecagonal structure is made possible by proper selection of dc link Voltages and switching states of the inverters. The proposed scheme retains all the advantages of multilevel topologies as well as the advantages of dodecagonal Voltage Space Vector structure. In addition to that, a generic and simple method for calculation of pulsewidth modulation timings using only sampled reference values ( $v_\alpha$ and $v_\beta$ ) is proposed. This enables the scheme to be used for any closed-loop application such as Vector control. In addition, a new method of switching technique is proposed, which ensures minimum switching while eliminating the fifth- and seventh-order harmonics and suppressing the eleventh and thirteenth harmonics, eliminating the need for bulky filters. The motor phase Voltage is a 24-stepped waveform for the entire modulation range thereby reducing the number of switchings of the individual inverter modules. Experimental results for steady-state operation, transient operation, including start-up have been presented and the results of fast Fourier transform analysis is also presented for validating the proposed concept.
S. Srinivas - One of the best experts on this subject based on the ideXlab platform.
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design and development of a single cm filter for bearing current and ground current reduction in a dual two level inverter fed open end winding induction motor drive
IEEE International Conference on Power Electronics Drives and Energy Systems, 2016Co-Authors: J Kalaiselvi, S. SrinivasAbstract:A dual two-level inverter with an open-end winding induction motor can realise a three/four level Voltage Space Vector. High switching frequency coupled with the use of such multilevel inversion system can produce good motor drive performance. This however can generate immense machine shaft Voltage and bearing currents apart from large leakage ground currents that are deleterious to the motor drive system and add to the malfunctioning of many safety equipment. To circumvent the above problems, this work presents the design and development of a single common mode (CM) passive filter for the above power circuit. With the application of the suggested single CM filter, both the bearing currents and the common mode currents are successfully attenuated. The proposed CM filter requires less hardware compared to the use of two CM filters reported in the literature. Simulations using MATLAB/Simulink is used to demonstrate the efficacy of a single CM filter. Also, the single CM filter is experimentally verified with an open-end winding motor fed from two inverters on both sides.
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theoretical and experimental analysis for current in a dual inverter fed open end winding induction motor drive with reduced switching pwm
IEEE Transactions on Industrial Electronics, 2013Co-Authors: S. Srinivas, Ramachandra K SekharAbstract:A dual two-level Voltage source inverter (VSI) can synthesize a three-level Voltage Space Vector employing an open-end winding induction motor. Space-Vector-based pulsewidth modulation (PWM) variants for this dual VSI are proposed in this paper that offer the dual advantage of limiting the switching power loss to a single VSI at all instants and also reducing the switching commutations in the dual VSI by 50%. The influence of different error volt seconds (affected with different PWM variants) on the motor phase current in the dual VSI is critically analyzed. To this end, two analytical approaches (one using error-Voltage trajectory information and the other using switching state information of the dual VSI) are also proposed in this paper to predict the current trajectory and the ripple content in the drive system. Expressions for rms ripple current are developed with different PWM variants. The efficacy of the proposed analytical approaches to predict the current trajectory and the ripple content is confirmed from the experimental results. All the PWM variants are first simulated using MATLAB and verified experimentally by conducting tests on a three-phase open-end winding induction motor drive controlled with volts per hertz control. The implementation of the PWM algorithms only requires instantaneous magnitudes of three-phase reference Voltages and completely avoids the sector identification and lookup tables.
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theoretical and experimental analysis for current in a dual inverter fed open end winding induction motor drive with reduced switching pwm
IEEE Transactions on Industrial Electronics, 2013Co-Authors: S. Srinivas, Ramachandra K SekharAbstract:A dual two-level Voltage source inverter (VSI) can synthesize a three-level Voltage Space Vector employing an open-end winding induction motor. Space-Vector-based pulsewidth modulation (PWM) variants for this dual VSI are proposed in this paper that offer the dual advantage of limiting the switching power loss to a single VSI at all instants and also reducing the switching commutations in the dual VSI by 50%. The influence of different error volt seconds (affected with different PWM variants) on the motor phase current in the dual VSI is critically analyzed. To this end, two analytical approaches (one using error-Voltage trajectory information and the other using switching state information of the dual VSI) are also proposed in this paper to predict the current trajectory and the ripple content in the drive system. Expressions for rms ripple current are developed with different PWM variants. The efficacy of the proposed analytical approaches to predict the current trajectory and the ripple content is confirmed from the experimental results. All the PWM variants are first simulated using MATLAB and verified experimentally by conducting tests on a three-phase open-end winding induction motor drive controlled with volts per hertz control. The implementation of the PWM algorithms only requires instantaneous magnitudes of three-phase reference Voltages and completely avoids the sector identification and lookup tables.
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an improved pwm for a dual two level inverter fed open end winding induction motor drive
International Conference on Electrical Machines, 2010Co-Authors: K Ramachandrasekhar, Shravan Mohan, S. SrinivasAbstract:Three-level Voltage Space Vector can be synthesized using a dual two-level inverter scheme employing open-end winding induction motor drive. Owing to the advantages this configuration offers over the other popular three-level inverter configurations, many PWM control strategies have been proposed. Towards this end, alternate sub-hexagonal center PWM switching scheme was presented recently that employs each of the two-level inverters as clamping and switching inverters. In this paper, an improved PWM switching scheme is proposed that is aimed at further reducing the number of switching commutations in the dual-inverter. It is attempted to reduce the switching commutations in the dual-inverter especially during the changeover of inverters roles from clamping to switching inverter and vice versa in the entire cycle of the supply. A significant 50% reduction in the number of switching commutations in the dual-inverter is achieved with the use of the proposed PWM scheme. The implementation of the PWM scheme neither requires any look-up tables nor sector identification while it only requires the magnitudes of instantaneous three phase reference Voltages. The improved PWM scheme is first simulated and verified experimentally by driving the dual-inverter fed open-end winding induction motor by employing V/f control.
K Sivakumar - One of the best experts on this subject based on the ideXlab platform.
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a nine level inverter topology for medium Voltage induction motor drive with open end stator winding
IEEE Transactions on Industrial Electronics, 2013Co-Authors: P P Rajeevan, K Gopakumar, K Sivakumar, C Patel, Haitham AburubAbstract:A new scheme for nine-level Voltage Space-Vector generation for medium-Voltage induction motor (IM) drives with open-end stator winding is presented in this paper. The proposed nine-level power converter topology consists of two conventional three-phase two-level Voltage source inverters powered by isolated dc sources and six floating-capacitor-connected $H$ -bridges. The $H$ -bridge capacitor Voltages are effectively maintained at the required asymmetrical levels by employing a Space Vector modulation (SVPWM) based control strategy. An interesting feature of this topology is its ability to function in five- or three-level mode, in the entire modulation range, at full-power rating, in the event of any failure in the $H$ -bridges. This feature significantly improves the reliability of the proposed drive system. Each leg of the three-phase two-level inverters used in this topology switches only for a half cycle of the reference Voltage waveform. Hence, the effective switching frequency is reduced by half, resulting in switching loss reduction in high-Voltage devices. The transient as well as the steady-state performance of the proposed nine-level inverter-fed IM drive system is experimentally verified in the entire modulation range including the overmodulation region.
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a hybrid multilevel inverter topology for an open end winding induction motor drive using two level inverters in series with a capacitor fed h bridge cell
IEEE Transactions on Industrial Electronics, 2010Co-Authors: K Sivakumar, Rijil Ramchand, Chintan Patel, Anandarup Das, K GopakumarAbstract:In this paper, a new five-level inverter topology for open-end winding induction-motor (IM) drive is proposed. The open-end winding IM is fed from one end with a two-level inverter in series with a capacitor-fed H-bridge cell, while the other end is connected to a conventional two-level inverter. The combined inverter system produces Voltage Space-Vector locations identical to that of a conventional five-level inverter. A total of 2744 Space-Vector combinations are distributed over 61 Space-Vector locations in the proposed scheme. With such a high number of switching state redundancies, it is possible to balance the H-bridge capacitor Voltages under all operating conditions including overmodulation region. In addition to that, the proposed topology eliminates 18 clamping diodes having different Voltage ratings compared with the neutral point clamped inverter. On the other hand, it requires only one capacitor bank per phase, whereas the flying-capacitor scheme for a five-level topology requires more than one capacitor bank per phase. The proposed inverter topology can be operated as a three-level inverter for full modulation range, in case of any switch failure in the capacitor-fed H-bridge cell. This will increase the reliability of the system. The proposed scheme is experimentally verified on a four-pole 5-hp IM drive.
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a combination of hexagonal and 12 sided polygonal Voltage Space Vector pwm control for im drives using cascaded two level inverters
IEEE Transactions on Industrial Electronics, 2009Co-Authors: K Sivakumar, Rijil Ramchand, C Patel, K GopakumarAbstract:This paper proposes a multilevel inverter configuration which produces a hexagonal Voltage Space Vector structure in the lower modulation region and a 12-sided polygonal Space Vector structure in the overmodulation region. A conventional multilevel inverter produces 6n plusmn 1 (n = odd) harmonics in the phase Voltage during overmodulation and in the extreme square-wave mode of operation. However, this inverter produces a 12-sided polygonal Space Vector location, leading to the elimination of 6n plusmn 1 (n = odd) harmonics in the overmodulation region extending to a final 12-step mode of operation with a smooth transition. The benefits of this arrangement are lower losses and reduced torque pulsation in an induction motor drive fed from this converter at higher modulation indexes. The inverter is fabricated by using three conventional cascaded two-level inverters with asymmetric dc-bus Voltages. A comparative simulation study of the harmonic distortion in the phase Voltage and associated losses in conventional multilevel inverters and that of the proposed inverter is presented in this paper. Experimental validation on a prototype shows that the proposed converter is suitable for high-power applications because of low harmonic distortion and low losses.
