Ayslan Caisson Noroes Maia

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 multilevel converters based on three-leg converters

This paper presents ac-dc-ac multilevel converters for single-phase and three-phase applications obtained from the cascade of three-leg converters. Differently from the more usual series connection based configurations, like dc-ac modules in H-bridge multilevel configurations, the series connection arrangement treated in this work means in series connections of the ac-dc-ac modules. The converters are suitable to be used as either uninterrupted power supply (UPS) or unified power quality conditioner (UPQC) without isolation transformer. PWM and control strategies suitable to provide the balanced control of the dc-link capacitors and the optimization of the harmonic distortion and converter losses are proposed. Simulated and experimental results are presented to validate the theoretical considerations.

A New Three-Phase AC–DC–AC Multilevel Converter Based on Cascaded Three-Leg Converters

This paper proposes and investigates a new three-phase ac–dc–ac multilevel conversion system obtained from cascaded three-leg converters. Such configuration presents advantages in terms of reduced switch blocking voltages and consequently lower dc-link voltage rating. Operating principles, a pulse-width modulation (PWM) technique based on vector approach, and a control strategy are presented. The operation with different dc-link voltage values and a balancing method are discussed, and is supported by simulation and experimental results. The PWM technique is able to generate multilevel voltage waveforms, which permits reducing the switching frequency stress leading to reduced semiconductor losses. Simulation results are used to compare the proposed configuration with a conventional solution in terms of harmonic distortion and semiconductor losses. Experimental results demonstrate the feasibility of the studied converter, and were obtained by using a downscaled prototype with insulated gate bipolar transistors with dedicated drives and a digital signal processor with appropriated plug-in boards and sensors.

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.

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.

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.

Investigation of single-phase multilevel inverter based on series/parallel-connected H-bridges

This paper investigates a multilevel inverter composed of series/parallel-connected H-bridges. The presented structure can be used for applications in which is intended to use semiconductor switches with low voltage and low current rating. A comprehensive system model to control the circulating current, an overall control strategy to adjust the output voltage with constant magnitude and frequency, and a level-shifted PWM (LS-PWM) strategy based on a voltage vectors unidimensional and plane analysis are presented. The LS-PWM is capable of mitigating the low-frequency circulating current, thus generating multilevel voltage signal with low harmonic distortion, maximum number of levels, and low dv/dt. In addition, considering a wide range of values of voltages and currents and any power levels, the total converter losses are reduced compared with conventional multilevel converters. Two multilevel conventional inverters with same number of semiconductor switches are used for comparison. Simulation and experimental results demonstrate the feasibility of the studied converter.