Victor F. M. B. Melo

AC-DC-AC six-phase machine drive system based on single-phase bridge converters

This paper presents an ac-dc-ac reversible six-phase machine drive system. It is composed of single-phase bridge converters connected in series in the grid side and single-phase bridge converters connected at the machine phase terminals. The proposed topology eliminates the input isolation transformers and reduces the power processed by converter switches and the harmonic distortion in the grid side. The model and the control strategy have been developed. Simulation and experimental results are presented.

Six-Phase Machine Conversion System With Three- and Single-Phase Series Converters

This paper presents two conversion systems based on the association of a six-phase machine (SPM) with an electrical grid by means of three- and single-phase converters. The machine is composed of two three-phase groups. One of them provides the power to the three-phase converter, and the other provides the power to the single-phase converters, in an open-end winding connection (see Fig. 2). The first conversion system is composed of bidirectional switches and can be used with induction or permanent-magnet synchronous machines. The second system is partially reversible since the single-phase converters are also composed of diodes and is more indicated for permanent-magnet synchronous machines. Furthermore, the proposed configurations do not use transformers and generate multilevel voltage at the grid-side converter with amplitude higher than that of the machine side, permitting one to reduce the transmission I2R losses. The complete analysis of the systems, including the pulsewidth- modulated techniques, is presented. Simulation and experimental results are also presented.

Active Power Line Conditioner based on Modular Multilevel Cascade Converter - Double-Star Chopper-Cells

In this paper an Active Power Line Conditioner (APLC) is proposed based on a Modular Multilevel Cascade Converter (MMCC) - Double Star Chopper Cells (DSCC) topology. A higher-voltage, low-switching frequency IGBT converter is used to achieve harmonic minimization. Compared to the conventional APLC topology, the proposed approach employs lower DC-link voltage, lower voltage in the power devices, flexible output voltage level, fault protection, less prone to noise, loss reduction, among others features considered in this work. Experimental results show that the proposed active power filter topology is capable of minimizing load harmonics and compensating reactive power at the Point of Commom Coupling (PCC).

Hybrid open-end and NPC AC six-phase machine drive systems

This paper presents two machine drive system based on a six-phase machine (SPM) and three-leg converters. The machine is composed of two three-phase groups. For the first configuration, one of the groups is connected to a three-leg converter and the other is connected to other two three-leg converters in an open-end winding configuration (see Fig. 4). For the second configuration, one of the groups is connected to a three-leg converter (similar to first one) and the other group is connected to a three-level NPC converter (see Fig. 5). Since the machine two groups are fed differently, the system topology is considered to be hybrid. The purpose of these topologies is to be an alternative configuration, being midway between the conventional six-leg inverter system (see Fig. 1) and the NPC six-leg inverter system (see Fig. 2) and Conventional twelve-leg Open-end inverter system (see Fig. 3). Compared with the conventional six-leg system, the proposed systems permits reducing the power processed by the semiconductor switches and their ratings, the dc-link voltage and the harmonic distortion. On the other hand, the proposed systems constitute less complex alternatives, compared with the open-end and NPC counterparts (see Fig. 3). PWM and control strategies are discussed. Simulation and experimental results are also presented.

Six-phase open-end machine conversion system with reduced number of controlled components

This paper presents two six-phase open-end machine conversion systems. They are composed of three three-leg converters connected in series to a six-phase machine with open terminals, in an open-end winding connection. The converters use diodes to replace controlled switches, making the conversion system non-reversible and with a reduced number of controlled components. In this case, the machine must work always as a generator. A study concerning harmonic distortion and semiconductor losses is carried out. PWM and control strategies are developed. Simulation and experimental results in order to test these strategies are presented.

AC-DC-AC nine-phase machine drive system based on H-bridges and three-leg converters

This paper presents an ac-dc-ac reversible nine-phase machine drive system. The grid side converter is composed of Y-connected single-phase bridges. As the machine is composed of three three-phase groups, a three-leg converters are connected separately to each group. The topology does not make use of input isolation transformers and reduces the power processed by converter switches when compared to that of conventional two-level converter. Moreover, harmonic distortion in voltages generated by the grid side converter is reduced when compared to conventional two-level converter. The model and the control strategy have been developed. Simulation and experimental results are also presented.

Hybrid Dual and NPC Six-Phase Drive Systems

This paper presents two hybrid six-phase machine drive systems. The topologies are considered to be hybrid because two three-phase groups of the machine are fed by different types of converters. The purpose of these topologies is to be alternative configurations, being midway between the conventional six-leg two-level (2L) inverter, composed of 12 switches, and more complex structures, such as the six-leg three-level neutral point clamped (3L-NPC) inverter, composed of 24 switches and 12 clamping diodes, or the conventional 12-leg dual inverter, composed of 24 switches. One of the hybrid topologies is composed of 18 switches and the other is composed of 18 switches and 6 clamping diodes. A comparative study of harmonic distortion, semiconductor losses, and machine torque ripple is performed. Compared with the conventional 2L inverter, the proposed systems provide better performance in terms of harmonic distortion, overall semiconductor losses, and machine torque ripple and are less complex than dual and NPC inverters. Pulse width modulation (PWM) strategy is discussed and simulated. A modification in PWM strategy of the hybrid configurations is performed in order to obtain similar torque ripple to the cases when dual and 3L-NPC converters are used, even with lower number of semiconductor devices. Experimental results are also presented in order to validate the PWM strategy.

Open-end nine-phase machine conversion systems

This paper presents four nine-phase drive systems. A nine-phase machine is connected to four converters in an open-end winding arrangement, with one of the converters being shared by all machine groups. Because of the shared converter, the structures are only applied for machines with α = 0°. A PWM strategy is discussed in order to reduce machine torque ripple. Simulation and experimental results are performed to validate the theoretical approach.

Six-leg single-phase multilevel rectifier-inverter: PWM strategies and control

This paper discusses a rectifier inverter composed of two three-leg converters with equal and unequal dc-links voltages connected in series. The operation with equal dc-links voltages divides equally the voltages in each converter. On the other hand, the operation with unequal dc-links voltages increases the number of voltage levels and contributes to reduce harmonic distortion and power losses. Space-vector and level-shifted techniques are discussed. The balance of separated dc sources using redundant voltage vectors is addressed in this paper. A closed-loop controller is used to control the average value of the dc voltages. Simulation results compare power losses and harmonic distortion of three-leg and six-leg topologies. Experimental results are provided to validate the feasibility of the system.

AC drive systems based on six-phase machine with three neutrals

This paper presents an AC drive system based on six-phase machine with three neutrals. The machine side converter has nine power legs and can be connected to the grid through one single DC-link or three isolated DC-links. Compared with the conventional back-to-back AC six-phase machine drive system, the proposed drive system permits reducing the DC-link voltages, eliminating step-up transformer, and the voltage at the grid side converter has higher amplitude than that of the machine side, reducing the transmission I2R losses. The system model and PWM strategy are presented and experimental results demonstrate the feasibility of the system.