다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The coexistence of ac and dc subgrids in a hybrid microgrid is likely given that modern distributed sources can either be ac or dc. Linking these subgrids is a power converter, whose topology should preferably be not too unconventional. This is to avoid unnecessary compromises to reliability, simplicity, and industry relevance of the converter. The desired operating features of the hybrid microgrid can then be added through this interlinking converter. To demonstrate, an appropriate control scheme is now developed for controlling the interlinking converter. The objective is to keep the hybrid microgrid in autonomous operation with active power proportionally shared among its distributed sources. Power sharing here should depend only on the source ratings and not their placements within the hybrid microgrid. The proposed scheme can also be extended to include energy storage within the interlinking converter, as already proven in simulation and experiment. These findings have not been previously discussed in the literature, where existing schemes are mostly for an ac or a dc microgrid, but not both in coexistence.

Autonomous Control of Interlinking Converters with Energy Storages in Hybrid AC-DC Microgrids

Multilevel inverters (MLIs) have gained increasing interest for advanced energy-conversion systems due to their features of high-quality produced waveforms, modularity, transformerless operation, voltage, and current scalability, and fault-tolerant operation. However, these merits usually come with the cost of a high number of components. Over the past few years, proposing new MLIs with a lower component count has been one of the most active topics in power electronics. The first aim of this article is to update and summarize the recently developed multilevel topologies with a reduced component count, based on their advantages, disadvantages, construction, and specific applications. Within the framework, both single-phase and three-phase topologies with symmetrical and asymmetrical operations are taken into consideration via a detailed comparison in terms of the used component count and type. The second objective is to propose a comparative method with novel factors to take component ratings into account. The effectiveness of the proposed method is verified by a comparative study.

Voltage Source Multilevel Inverters With Reduced Device Count: Topological Review and Novel Comparative Factors

The conventional three-level inverter suffers the limitation of voltage buck operation. In order to give both voltage buck and boost operation capability, the quasi-Z-source three-level T-type inverter (3LT $^2$ I) has been proposed. This paper further proposes a space vector modulation (SVM) scheme for the quasi-Z-source 3LT $^2$ I to reduce the magnitude and slew rate of common-mode voltage (CMV). By properly selecting the shoot-through phase, the shoot-through states are inserted within zero vector in order not to affect the active states and output voltage. Doing so, the CMV generated by the quasi-Z-source 3LT $^2$ I is restricted within one-sixth of dc-link voltage, and voltage boosting and CMV reduction can be simultaneously realized. In addition, high dc-link voltage utilization can be maintained. The proposed scheme has been verified in both simulations and experiments. Comparisons are conducted with the conventional SVM method and the phase-shifted sinusoidal PWM method.

A Space Vector Modulation Scheme of the Quasi-Z-Source Three-Level T-Type Inverter for Common-Mode Voltage Reduction

(57) Abstract: An induction machine (20) adapted to operate at variable speeds, including low speed and zero speed, comprises a polyphase stator and a squirrel cage rotor mounted within the stator. Wherein the stator comprises two separate stator windings (abc, xyz) and separate input terminals for each winding to enable drive power to be applied separately to the two windings. And the two windings have different numbers of poles with a ratio of 1: 3.

Drive of double stator winding induction machine

A single-stage high-voltage gain boost inverter is getting popularity in applications like solar photovoltaic, fuel cell, uninterruptible power system (UPS) systems, etc. Recently, single-stage voltage boost multilevel Z-source inverter (ZSI) and quasi-Z-source inverter (QZSI) have been proposed for dc–ac power conversion with improved power quality. Multilevel ZSI uses more number of high-power passive components in the intermediate network, which increase the system size and weight. Also, its input current is discontinuous in nature which is not desirable in some of the applications like fuel cell, UPS systems, hybrid electric vehicle, etc. In this paper, a continuous current input three-level LC -switching-based voltage boost neutral-point-clamped inverter is proposed, which uses comparatively less number of high-power passive components at the same time retains all the advantages of multilevel QZSI/ZSI. It is able to boost the input dc voltage and give required three-level ac output voltage in a single stage. Steady-state analysis of the proposed inverter is discussed to formulate the relationship between the input dc voltage and three-level ac output voltage. A unipolar pulse width modulation technique devised for the proposed inverter to eliminate first center band harmonics is also presented. The proposed converter has been verified by simulation in MATLAB Simulink as well as performing experiment with the help of a laboratory prototype.

A Three-Level LC -Switching-Based Voltage Boost NPC Inverter

In this paper, a fault-tolerant multiphase multilevel inverter (MPMLI) configuration is proposed based on the dual inverter concept. This configuration helps to improve the performance of pole–phase modulated multiphase induction motor (PPMMIM) drive in both normal and switch failure conditions. Comparing to the existing multilevel inverter topologies for multiphase induction motor (MIM) drives, the proposed MPMLI configuration requires less number of dc sources and power electronic devices. The proposed MPMLI configuration is able to sustain under various faulty conditions, which can improve the reliability of the system. In addition, dc-link utilization (DLU) in low-pole mode is improved by using space vector pulsewidth modulation (SVPWM). In high-pole mode, carrier-phase-shifted 3-Φ SVPWM is used for reducing the torque ripple. This MPMLI configuration produces a multilevel voltage profile across the effective phase in 3-phase 12-pole mode. By maintaining the V / f ratio constant, the proposed MPMLI-fed MIM drive facilitates a wide range of load torque with half of the rated speed in faulty condition. This advantage makes it suitable for traction and electric vehicle applications where reliability and wide range of torque–speed are the major concerns. The performance of proposed MPMLI-fed 5 hp, 9-φ PPMMIM drive is simulated by finite-element method (FEM) in ANSYS Maxwell 2-D and experimentally verified by laboratory prototype under normal and faulty conditions.

A Fault-Tolerant Multilevel Inverter for Improving the Performance of a Pole–Phase Modulated Nine-Phase Induction Motor Drive

This paper presents a multilevel inverter (MLI) configuration for open-end-winding pole-phase-modulated-multiphase induction motor (PPMMIM) drives. The proposed MLI configuration consists of one nine-phase two-level inverter and three 3-Φ two-level inverters. In pole–phase modulation, increasing the number of poles decreases the number of phases that increases the space harmonics in air gap flux. Moreover, in high-pole mode of PPMMIM drives, two-level voltage supply causes the high torque ripple that degrades the performance of the drive. Usually, conventional MLIs are not preferred for reducing torque ripple, due to the capacitor-balancing issues and more number of semiconductor devices. To address these issues, the proposed MLI configuration effectively utilized the inherent availability of the three identical voltage coils in the high-pole mode for reducing the torque ripple. The 3-Φ carrier phase-shifted space vector pulse width modulation (SVPWM) is used for generating the multistep voltage across the effective phase in high-pole mode as well as for shifting the lower order harmonics to higher order frequencies. Moreover, in low-pole mode, the dc-link voltage utilization of the proposed MLI configuration is improved by 13.8% with third harmonic injected SVPWM as compared to conventional 9-Φ SVPWM. Another important feature of the proposed MLI configuration is its ability to supply the two-level voltage under fault conditions. This feature notably improves the reliability of the PPMMIM drive. The finite-element method model of 5-hp nine-phase PPMMIM is designed in ANSYS Maxwell 2-D and is cosimulated with the proposed MLI configuration in Simplorer environment. The effectiveness of the proposed MLI-fed 5-hp MIM drive is experimentally verified for the entire modulation range.

A Multilevel Inverter Configuration for an Open-End-Winding Pole-Phase-Modulated-Multiphase Induction Motor Drive Using Dual Inverter Principle

Presently single stage boost multilevel inverters are becoming more popular for power conversion in renewable energy systems, AC-DC hybrid microgrids etc. Usually in these boost inverter the voltage stress across the inverter leg switches as well as current through these switches are quite higher as compared to load ratings which increases the chances of inverter leg switch failure. In this paper a three level voltage source boost inverter is proposed to achieve rated three level AC output voltage in a single power conversion stage. It retains all the advantages of three level quasi Z- Source inverter by using less number of passive components in the intermediate network between DC source and inverter leg. Beside the inherent shoot through fault tolerant feature the proposed inverter is capable to operate in open circuit failure to give rated balanced AC voltage at load. The above advantages of the proposed single stage inverter make it suitable for low and medium power renewable energy applications where size, weight are main constraint and some of the critical loads are connected to the system. The proposed inverter is verified by simulation (in MATLAB Simulink) and experiment with the help of a laboratory prototype.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2017.0085

Fault tolerant three-level boost inverter with reduced source and LC count

The pole-phase modulated induction motor (PPMIM) drives facilitate the extended range of speed-torque characteristics, which is an essential requirement for traction and electric vehicle applications. For getting the wider speed-torque variations, $15-\Phi $ PPMIM drive is analyzed, which is capable to operate at 2-pole 15-phase, 6-pole 5-phase, and 10-pole 3-phase modes. In these pole-phase operations, in high-phase and low-pole mode of operation, the increment in the linear modulation range with space vector pulsewidth modulation (SVPWM) is not significant. In the low-phase and high-pole mode of operation, there will be higher torque ripples due to the higher magnitude of space harmonics. In this paper, these issues are addressed by using carrier phase-shifted SVPWM (CPS-SVPWM) and phase grouping concepts. In low-pole operation, the linear modulation is enriched by using conventional $3-\Phi $ SVPWM to drive 15-phase machine by appropriately reorganizing the phase winding connections. Similarly, in 6-pole 5-phase mode of operation, the linear modulation range of PPMIM drive is enriched by using $5-\Phi $ SVPWM. It is known that in high-pole mode of PPMIM drive operation, each effective phase is formed by the multiple number of equal voltage potential coils (EVPCs), which are electrically in phase. The carriers of these EVPCs per phase are phase shifted by an appropriate angle to minimize the harmonics in the effective phase voltage, which results in better torque ripple profile. In addition, the detailed comparison of three possible different CPS-SVPWMs is presented, with their pros and cons for selecting the proper carrier phase shift angle. The performance of the proposed scheme has been validated by ANSYS Maxwell two-dimensional as well as laboratory prototype on 5-hp, $15-\Phi $ PPMIM drive.

Sivakumar Keerthipati

Papers

A Three-Level LC -Switching-Based Voltage Boost NPC Inverter

A Fault-Tolerant Multilevel Inverter for Improving the Performance of a Pole–Phase Modulated Nine-Phase Induction Motor Drive

A Multilevel Inverter Configuration for an Open-End-Winding Pole-Phase-Modulated-Multiphase Induction Motor Drive Using Dual Inverter Principle

Fault tolerant three-level boost inverter with reduced source and LC count

Linear Modulation Range and Torque Ripple Profile Improvement of PPMIM Drives