Nayara B. de Freitas

Investigation of Three-Phase AC–DC–AC Multilevel Nine-Leg Converter

In this paper, a reversible multilevel nine-leg converter for three-phase applications is investigated. This topology can be applied in line voltage regulators, power factor correction devices, and uninterrupted power supplies. It is composed of three single-phase three-leg converters with a leg shared by both load and grid sides. Suitable modeling, a pulse-width modulation (PWM) strategy based on a vector approach, and a control system are developed. The proposed PWM and control strategies are suitable to balance the dc-link voltages and to optimize the harmonic distortion, reducing switching stress and power losses. The investigated configuration is compared with two conventional topologies, including a neutral-point-clamped converter and has demonstrated that it presents some advantages in terms of voltage rating of the power switches, harmonic distortion, and semiconductor losses. Computer simulations and experimental results have been carried in the same operation conditions to verify the validity of theoretical considerations.

Open-end multi-level six-phase machine drive system with three three-phase DC-link converters

A novel multi-level AC six-phase motor drive is developed in this paper. The scheme is based on three conventional 2-level three-phase voltage source inverters (VSIs) supplying the open-end windings of a dual three-phase motor (six-phase induction machine). The proposed inverter is capable of supply the machine with multi-level voltage waveforms. The developed system is compared with the conventional solution and it is demonstrated that the drive system permits to reduce the harmonic distortion of the machine currents, to reduce the total semiconductor losses and to decrease the power processed by converter switches. The system model and the Pulse-Width Modulation (PWM) strategy are presented. The experimental verification was obtained by using IGBTs with dedicated drives and a digital signal processor (DSP) with plug-in boards and sensors.

AC–DC–AC Single-Phase Multilevel Six-Leg Converter With a Reduced Number of Controlled Switches

This paper proposes two unidirectional single-phase ac–dc–ac converters with a reduced number of controlled switches composed of two three-leg converters connected in series. The proposed converters allow us to feed the load voltage with sinusoidal voltages with constant amplitude and frequency and to operate with sinusoidal grid current with a high power factor. The converters can then be used as uninterruptible power supplies and unified power quality conditioners for nonregenerative applications. The system model, space-vector pulse width modulation technique, and a complete control system are given. A method to regulate the dc-link voltages using the voltage vector redundancies is presented. The proposed topologies are compared with the conventional one in terms of operation range, capability to operate with a unity grid power factor, voltage harmonic distortions, semiconductor losses, and others characteristics. Simulation and experimental results in many operating conditions are provided to validate the feasibility of the system.

Open-end multilevel six-phase machine drive system with five three-leg converters

This paper proposes and investigates a multilevel ac six-phase motor drive. The system is composed of five isolated three-leg voltage source inverters feeding the open-end windings of an asymmetrical six-phase induction motor (SPIM), which is adequate to generate multilevel voltages for high-power systems with voltage rating restrictions. A simple space vector pulse-width modulation (PWM) based on three similar individual planes and its implementation by means of equivalent level-shifted PWM are presented. A space vector pattern with a high number of voltage vectors redundancies is obtained. These redundancies and the application sequence of the voltage vectors are selected to minimize the amount of changes in the switching states and to decrease the harmonic distortion of the generated voltages. The vector pattern of this optimal modulation is obtained by analyzing only one plane and applied in the same way to the three planes as if they were independent. The developed PWM techniques have low computational complexity and are suitable for low-cost hardware implementations. Simulation results are used to compare the proposed topology with a conventional configuration in terms of harmonic distortion and semiconductor losses. Experimental results demonstrate the feasibility of the proposed drive system.

Investigation of three-phase AC-DC-AC multilevel nine-leg converter

In this paper, a reversible multilevel nine-leg converter for three-phase applications is investigated. This topology can be applied in line voltage regulator, power factor correction (PFC) and uninterrupted power supplies (UPS). It is composed of three single-phase three-leg converters with a leg shared by both load and grid sides. Suitable modelling, a pulse-width modulation (PWM) strategy based on vector approach and a control system are developed. The proposed PWM and control strategies are suitable to balance the DC-link voltages and to optimize of the harmonic distortion, reducing switching stress and power losses. Simulation results are used to compare the studied configuration with a conventional solution in terms of harmonic distortion and semiconductor losses. Experimental results are presented to validate the theoretical considerations and were obtained by using IGBTs with dedicated drives and a digital signal processor (DSP) with appropriated plug-in boards and sensors.

Six-Leg Single-Phase to Three-Phase Converter

This paper investigates the utilization of two different six-leg configurations of single-phase to three-phase converters. One of the topologies is transformerless and the other is transformer-based. The drive systems provide both bidirectional power flow and power factor control. Pulsewidth modulation techniques for the converter control are discussed. Simulation and experimental results are provided to illustrate and compare the operation of the systems.

A Bridgeless Controlled Rectifier for Single Split-Phase Systems

An unidirectional single-phase three-wire rectifier is proposed in this paper. Such a proposed topology is composed of a non-controlled leg, two controlled legs and a capacitor bank. A suitable model and control strategy of the system, including a synchronization method, are proposed as well. The synchronization method, associated with the PWM strategy, imposes the grid currents to have the same phase angle of the generated voltages by rectifier. This method ensures sinusoidal grid currents and mitigate the zero-crossover distortions normally caused by the use of diodes. A comprehensive comparison with two conventional configurations is also presented in this paper. Simulation and experimental results are also presented for validation purposes.

Six-leg single-phase to three-phase converter

This paper investigates the utilization of two different six-leg configurations of single-phase to three-phase converters. One of the topologies is transformerless and the other is transformer based. The studied converters allow feeding the load voltage with sinusoidal voltages with constant amplitude and frequency, and to operate with sinusoidal grid current with high power factor. The system model and pulse-width modulation techniques for one of the topologies are given. Control strategies for both topologies are provided. The studied topologies are compared with the conventional in terms of dc-link specification, voltages harmonic distortions, semiconductor losses, and other characteristics. Simulation and experimental results are provided to illustrate the operation of the systems.

A bridgeless controlled rectifier for single split-phase systems

An unidirectional single-phase three-wire rectifier is proposed in this paper. Such topology is composed of a noncontrolled leg, two controlled legs, and a capacitor bank. A suitable model, pulse-width modulation, and control strategies of the system are proposed as well. The control strategy includes the synchronization method, in which it imposes the grid currents with the same phase angle of the voltages generated by the rectifier. This method ensures sinusoidal grid currents and mitigates the zero-crossover distortions normally caused by the use of diodes. A comprehensive comparison with two conventional configurations is also presented in this paper. Simulation and experimental results are also presented for validation purposes.

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.