The Experts below are selected from a list of 23775 Experts worldwide ranked by ideXlab platform
Alejandro G. Yepes - One of the best experts on this subject based on the ideXlab platform.
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Improvement in DC-Link Utilization With Reduced Current and Torque Deterioration for Five-Phase Drives by Combination of Circulating-Current Filters and Simple Carrier-Based PWM Based on Closed-Form Expressions
IEEE Transactions on Industrial Electronics, 2021Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoy, Hamid A. ToliyatAbstract:Multiphase drives offer important advantages over three-phase ones. With pulsewidth modulation (PWM), zero-sequence and $x$ – $y$ signals can be injected to enhance dc-Link Utilization (DLU). For example, in five-phase drives, for given dc-Link voltage, the fundamental is raised by $\text{23.1}\%$ . For sinusoidally distributed windings, although $x$ – $y$ currents increase losses, torque is unaffected. However, no simple carrier-based PWM methods based on closed-form expressions have been presented for this purpose so far. Most importantly, $x$ – $y$ currents may be unacceptably large, due to the small $x$ – $y$ impedance. This is particularly troublesome when high fundamental voltage is needed continuously. Applying square waveform instead of PWM raises the fundamental from $\text{23.1}$ to $\text{27.3}\%$ . Given the square-voltage distortion, filters with large $x$ – $y$ impedance were devised for this approach. However, some square-waveform harmonics map into the torque-producing plane without attenuation, generating torque ripple. This article proposes to use a simple carrier-based PWM method in five-phase drives combined with a circulating-current filter. The $x$ – $y$ voltages, which see large filter impedance, are exploited to achieve a high DLU similar to previous solutions, but without torque ripple or excessive $x$ – $y$ currents. Guidelines are given for designing the filter when used with the presented PWM strategy. Experimental results verify the proposal.
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IECON - Extension to Symmetrical and Asymmetrical n-Phase AC Drives of Simple Carrier-Based PWM for Prolonged High DC-Link Utilization
IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society, 2020Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoyAbstract:Recently, it was proposed to combine circulating-current (x-y) filters with a carrier-based pulsewidth-modulation (PWM) method, which injects harmonics in no-torque x-y subspaces (attenuated by the filter) of five-phase motors to achieve high dc-Link Utilization (DLU). The filter allows prolonged high DLU without overheating. Unlike square-wave switching, no torque ripple is introduced by the PWM. Compared with other PWM techniques capable of high-DLU operation (often called overmodulation), the one proposed for said filters is especially convenient because of its simplicity. However, it is unclear if this PWM method can be extended to machines of any phase number n and winding arrangement (symmetrical or asymmetrical). This paper extends this simple carrier-based PWM strategy to n-phase (symmetrical or asymmetrical) drives, and evaluates its behavior in terms of DLU. The improvement in DLU, compared with conventional PWM with zero-sequence injection, is considerable in most cases. Current distortion is negligible with suitable filter, and no torque ripple (unlike square-wave switching) is generated.
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Multifrequency Current Control for Multiphase Machines With Antiwindup, Distortion-Free Saturation and Full DC-Link Utilization
2018 IEEE Energy Conversion Congress and Exposition (ECCE), 2018Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoy, Hamid A. ToliyatAbstract:Multiphase drives offer important advantages over three-phase ones; e.g., lower per-phase rating and enhanced fault tolerance. For multiphase machines, multifrequency current control (MCC) is often required, e.g., for harmonic cancellation or injection. In certain situations, converter output voltage (OV) saturation (OVS) occurs, which can cause windup and additional OV distortion. For MCC, obtaining antiwindup and distortion-free OVS, with full dc-bus exploitation, entails extra complexity. Recent publications address this problem in three-phase and dual three-phase (treated as two independent three-phase) systems with one and two isolated neutrals, respectively. However, extending such solutions to drives of any phase number $n$ , winding arrangement (symmetrical or asymmetrical) and neutral configuration is not straightforward. This paper proposes a general MCC scheme, including antiwindup and distortion-free OVS with full dc-Link Utilization, for $n$ -phase machines with different winding arrangements (symmetrical or asymmetrical) and neutral configurations. Simulation results are provided.
Hamid A. Toliyat - One of the best experts on this subject based on the ideXlab platform.
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Improvement in DC-Link Utilization With Reduced Current and Torque Deterioration for Five-Phase Drives by Combination of Circulating-Current Filters and Simple Carrier-Based PWM Based on Closed-Form Expressions
IEEE Transactions on Industrial Electronics, 2021Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoy, Hamid A. ToliyatAbstract:Multiphase drives offer important advantages over three-phase ones. With pulsewidth modulation (PWM), zero-sequence and $x$ – $y$ signals can be injected to enhance dc-Link Utilization (DLU). For example, in five-phase drives, for given dc-Link voltage, the fundamental is raised by $\text{23.1}\%$ . For sinusoidally distributed windings, although $x$ – $y$ currents increase losses, torque is unaffected. However, no simple carrier-based PWM methods based on closed-form expressions have been presented for this purpose so far. Most importantly, $x$ – $y$ currents may be unacceptably large, due to the small $x$ – $y$ impedance. This is particularly troublesome when high fundamental voltage is needed continuously. Applying square waveform instead of PWM raises the fundamental from $\text{23.1}$ to $\text{27.3}\%$ . Given the square-voltage distortion, filters with large $x$ – $y$ impedance were devised for this approach. However, some square-waveform harmonics map into the torque-producing plane without attenuation, generating torque ripple. This article proposes to use a simple carrier-based PWM method in five-phase drives combined with a circulating-current filter. The $x$ – $y$ voltages, which see large filter impedance, are exploited to achieve a high DLU similar to previous solutions, but without torque ripple or excessive $x$ – $y$ currents. Guidelines are given for designing the filter when used with the presented PWM strategy. Experimental results verify the proposal.
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Multifrequency Current Control for Multiphase Machines With Antiwindup, Distortion-Free Saturation and Full DC-Link Utilization
2018 IEEE Energy Conversion Congress and Exposition (ECCE), 2018Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoy, Hamid A. ToliyatAbstract:Multiphase drives offer important advantages over three-phase ones; e.g., lower per-phase rating and enhanced fault tolerance. For multiphase machines, multifrequency current control (MCC) is often required, e.g., for harmonic cancellation or injection. In certain situations, converter output voltage (OV) saturation (OVS) occurs, which can cause windup and additional OV distortion. For MCC, obtaining antiwindup and distortion-free OVS, with full dc-bus exploitation, entails extra complexity. Recent publications address this problem in three-phase and dual three-phase (treated as two independent three-phase) systems with one and two isolated neutrals, respectively. However, extending such solutions to drives of any phase number $n$ , winding arrangement (symmetrical or asymmetrical) and neutral configuration is not straightforward. This paper proposes a general MCC scheme, including antiwindup and distortion-free OVS with full dc-Link Utilization, for $n$ -phase machines with different winding arrangements (symmetrical or asymmetrical) and neutral configurations. Simulation results are provided.
Jesus Doval-gandoy - One of the best experts on this subject based on the ideXlab platform.
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Improvement in DC-Link Utilization With Reduced Current and Torque Deterioration for Five-Phase Drives by Combination of Circulating-Current Filters and Simple Carrier-Based PWM Based on Closed-Form Expressions
IEEE Transactions on Industrial Electronics, 2021Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoy, Hamid A. ToliyatAbstract:Multiphase drives offer important advantages over three-phase ones. With pulsewidth modulation (PWM), zero-sequence and $x$ – $y$ signals can be injected to enhance dc-Link Utilization (DLU). For example, in five-phase drives, for given dc-Link voltage, the fundamental is raised by $\text{23.1}\%$ . For sinusoidally distributed windings, although $x$ – $y$ currents increase losses, torque is unaffected. However, no simple carrier-based PWM methods based on closed-form expressions have been presented for this purpose so far. Most importantly, $x$ – $y$ currents may be unacceptably large, due to the small $x$ – $y$ impedance. This is particularly troublesome when high fundamental voltage is needed continuously. Applying square waveform instead of PWM raises the fundamental from $\text{23.1}$ to $\text{27.3}\%$ . Given the square-voltage distortion, filters with large $x$ – $y$ impedance were devised for this approach. However, some square-waveform harmonics map into the torque-producing plane without attenuation, generating torque ripple. This article proposes to use a simple carrier-based PWM method in five-phase drives combined with a circulating-current filter. The $x$ – $y$ voltages, which see large filter impedance, are exploited to achieve a high DLU similar to previous solutions, but without torque ripple or excessive $x$ – $y$ currents. Guidelines are given for designing the filter when used with the presented PWM strategy. Experimental results verify the proposal.
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IECON - Extension to Symmetrical and Asymmetrical n-Phase AC Drives of Simple Carrier-Based PWM for Prolonged High DC-Link Utilization
IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society, 2020Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoyAbstract:Recently, it was proposed to combine circulating-current (x-y) filters with a carrier-based pulsewidth-modulation (PWM) method, which injects harmonics in no-torque x-y subspaces (attenuated by the filter) of five-phase motors to achieve high dc-Link Utilization (DLU). The filter allows prolonged high DLU without overheating. Unlike square-wave switching, no torque ripple is introduced by the PWM. Compared with other PWM techniques capable of high-DLU operation (often called overmodulation), the one proposed for said filters is especially convenient because of its simplicity. However, it is unclear if this PWM method can be extended to machines of any phase number n and winding arrangement (symmetrical or asymmetrical). This paper extends this simple carrier-based PWM strategy to n-phase (symmetrical or asymmetrical) drives, and evaluates its behavior in terms of DLU. The improvement in DLU, compared with conventional PWM with zero-sequence injection, is considerable in most cases. Current distortion is negligible with suitable filter, and no torque ripple (unlike square-wave switching) is generated.
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Multifrequency Current Control for Multiphase Machines With Antiwindup, Distortion-Free Saturation and Full DC-Link Utilization
2018 IEEE Energy Conversion Congress and Exposition (ECCE), 2018Co-Authors: Alejandro G. Yepes, Jesus Doval-gandoy, Hamid A. ToliyatAbstract:Multiphase drives offer important advantages over three-phase ones; e.g., lower per-phase rating and enhanced fault tolerance. For multiphase machines, multifrequency current control (MCC) is often required, e.g., for harmonic cancellation or injection. In certain situations, converter output voltage (OV) saturation (OVS) occurs, which can cause windup and additional OV distortion. For MCC, obtaining antiwindup and distortion-free OVS, with full dc-bus exploitation, entails extra complexity. Recent publications address this problem in three-phase and dual three-phase (treated as two independent three-phase) systems with one and two isolated neutrals, respectively. However, extending such solutions to drives of any phase number $n$ , winding arrangement (symmetrical or asymmetrical) and neutral configuration is not straightforward. This paper proposes a general MCC scheme, including antiwindup and distortion-free OVS with full dc-Link Utilization, for $n$ -phase machines with different winding arrangements (symmetrical or asymmetrical) and neutral configurations. Simulation results are provided.
K Sivakumar - One of the best experts on this subject based on the ideXlab platform.
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pole phase modulated multiphase induction motor drive with reduced torque ripple and improved dc Link Utilization
IEEE Transactions on Power Electronics, 2017Co-Authors: B Umesh, K SivakumarAbstract:Wider speed and torque range is one of the major requirements of high-power propulsion and traction applications. Pole-phase modulation (PPM) of multiphase induction motors provide extended speed-torque range without the need of oversizing the motor rating. Particularly, PPM of nine-phase IM gives four-pole and 12-pole mode of operations with wider speed and torque variations. But in three-phase (3-φ) 12-pole mode higher torque ripple degrades the performance of drive system. Further, in nine-phase (9-φ) four-pole mode the extra dc Link Utilization (DLU) using 9-φ space vector pulse width modulation (SVPWM) is very less compared to the 3-φ SVPWM. Possible techniques to improve DLU by adding third harmonic order offset value to the sine references introduce dominant lower order harmonic currents in to the phase windings. To address these problems, this paper proposes a multilevel voltage generation technique using an auxiliary 3-φ two-level inverter for reducing high torque pulsations during starting. Compared to the conventional multilevel inverters, the proposed multilevel inverter scheme gives the same number of voltage levels with considerably less device count. In addition, this paper also proposes a simple and effective phase grouping method to avoid dominant lower order harmonic currents into the phase windings while improving the DLU of four-pole operation. The proposed performance improvement technique for PPM of 9-φ IM is simulated in ANSYS Maxwell two-dimensional and Simplorer environment. A prototype of 5-hp 9-φ IM drive controlled using SPARTAN 6 FPGA board is developed for validating the proposed performance improvement methods experimentally.
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a four level inversion scheme for a 6 n pole open end winding induction motor drive for an improved dc Link Utilization
IEEE Transactions on Industrial Electronics, 2014Co-Authors: V.t. Somasekhar, Barry Venugopal Reddy, K SivakumarAbstract:In this paper, a new power-circuit configuration for four-level inversion with an open-end winding induction motor is proposed. This configuration is suitable for an induction motor with 6 n (n = 1, 2,...) number of poles. Two isolated dc power supplies, each rated for one third of the total dc-Link voltage, are sufficient to realize this four-level inverter scheme. It is shown that it is possible to produce a voltage vector of 1-p.u. magnitude with a total dc-Link voltage of 0.66 p.u., indicating that the dc-Link Utilization is enhanced by a factor of 33% with this power-circuit configuration. In the proposed power circuit, the zero-sequence current is arrested as the motor phase windings of the open-end winding induction motor are segmented into two separate groups in the ratio of 2 : 1, with one end of each group forming an isolated neutral point. Each phase group is then powered by two individual two-level inverters with two separate dc-power supplies with a common negative rail. The existence of this common negative rail is the principal cause of an increased dc-bus Utilization. A simple decoupled space-vector pulsewidth modulation is adequate to control both of these inverters, which further demonstrates the simplicity of the drive control.
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A Four-Level Inversion Scheme for a 6 $n$ -Pole Open-End Winding Induction Motor Drive for an Improved DC-Link Utilization
IEEE Transactions on Industrial Electronics, 2014Co-Authors: V.t. Somasekhar, Barry Venugopal Reddy, K SivakumarAbstract:In this paper, a new power-circuit configuration for four-level inversion with an open-end winding induction motor is proposed. This configuration is suitable for an induction motor with 6 n (n = 1, 2,...) number of poles. Two isolated dc power supplies, each rated for one third of the total dc-Link voltage, are sufficient to realize this four-level inverter scheme. It is shown that it is possible to produce a voltage vector of 1-p.u. magnitude with a total dc-Link voltage of 0.66 p.u., indicating that the dc-Link Utilization is enhanced by a factor of 33% with this power-circuit configuration. In the proposed power circuit, the zero-sequence current is arrested as the motor phase windings of the open-end winding induction motor are segmented into two separate groups in the ratio of 2 : 1, with one end of each group forming an isolated neutral point. Each phase group is then powered by two individual two-level inverters with two separate dc-power supplies with a common negative rail. The existence of this common negative rail is the principal cause of an increased dc-bus Utilization. A simple decoupled space-vector pulsewidth modulation is adequate to control both of these inverters, which further demonstrates the simplicity of the drive control.
Haruhisa Hasegawa - One of the best experts on this subject based on the ideXlab platform.
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Parallel video streaming optimizing network throughput
Computer Communications, 2011Co-Authors: Noriaki Kamiyama, Ryoichi Kawahara, Tatsuya Mori, Shigeaki Harada, Haruhisa HasegawaAbstract:In the Internet, video streaming services, in which users can enjoy videos at home, are becoming popular. Video streaming with high definition TV (HDTV) or ultra high definition video (UHDV) quality will be also provided and widely demanded in the future. However, the transmission bit-rate of high-quality video streaming is quite large, so generated traffic flows will cause Link congestion. In the Internet, routes that packets take are determined using static Link weights, so the network productivity, i.e., the maximum achievable throughout by the network, is determined by the capacity of a bottleneck Link with the maximum Utilization, although Utilizations of many Links remain low level. Therefore, when providing streaming services of rich content, i.e., videos with HDTV or UHDV quality, it is important to flatten the Link Utilization, i.e., reduce the maximum Link Utilization. We propose that ISPs use multiple servers to deliver rich content to balance the Link Utilization and propose server allocation and server selection methods for parallel delivery. We evaluate the effect of parallel delivery using 23 actual commercial ISP networks.
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NOMS - Impact of topology on parallel video streaming
2010 IEEE Network Operations and Management Symposium - NOMS 2010, 2010Co-Authors: Noriaki Kamiyama, Ryoichi Kawahara, Tatsuya Mori, Shigeaki Harada, Haruhisa HasegawaAbstract:Video streaming with HDTV or UHDV quality will be provided and widely demanded in the future. However, the transmission bit-rate of high-quality video streaming is quite large, so generated traffic flows will cause Link congestion. Therefore, when providing streaming services of rich content, it is important to flatten the Link Utilization, i.e., reduce the maximum Link Utilization. To achieve this goal, parallel video streaming in which ISPs use multiple servers to deliver rich content is effective. However, the effect of parallel video streaming depends on the network topology and Link capacities. In this paper, we investigate the impact of network topologies on the effect of parallel video streaming using 23 actual commercial ISP networks, when optimally designing server locations and optimally selecting servers.