Italo Roger F. M. P. da Silva

Hybrid multilevel inverter system for Open-End Winding (OEW) induction motor drive based on Double-Star Chopper-Cells (DSCC) converter

This paper proposes a hybrid multilevel topology for Open-End stator Winding (OEW) induction motor drive based on Modular Multilevel Cascade Inverter (MMCI) with Double-Star Chopper-Cells (DSCC) and 2-Level Voltage Source Inverter (2L-VSI). An efficient Voltage Reference Technique is proposed to generate the pole voltages of both inverters. As a result, the DSCC inverter is commanded in high-switching frequency, while the 2L-VSI operates at the fundamental frequency. A voltage-balancing control of the floating DC capacitors of the DSCC is presented to ensure the energy balance. At last, to investigate the proposed system and control strategy, experimental results are presented.

Single-Phase AC–AC Double-Star Chopper Cells (DSCC) Converter Without Common DC-Link Capacitor

This paper presents a single-phase AC-AC converter based on Modular Multilevel Cascade Converter (MMCC) with Double-Star Chopper-Cells (DSCC). This structure is composed by three DSCC-legs, the middle leg is shared, and also it does not present a common DC-link capacitor. It is suitable for regenerative low-power AC-AC conversion. The voltage-balancing control is presented to regulate the floating DC capacitor voltages. Furthermore, a grid current and terminal load voltage control is presented to correct the Power Factor (PF) and to ensure sinusoidal waveforms. Details about a designed 16-SM prototype are also presented. The experimental results allow validating the control strategies and the effectiveness of the proposed structure.

Hybrid Modular Multilevel DSCC Inverter for Open-End Winding Induction Motor Drives

This paper proposes a hybrid modular multilevel drive system based on a modular multilevel cascade inverter (MMCI) with double-star chopper cells (DSCC) and a two-level (2L) inverter to feed three-phase induction motors with open-end windings (OEWs). The proposed system is an alternative for high-speed motor drives based on a small-scale DSCC topology. A voltage reference technique is presented based on the analysis of the degrees of freedom of the system for generating the output voltage references, considering any voltage ratios of the dc links. The proposed system is evaluated in a symmetric scenario, in which the dc-link voltages are equal. Thus, the 2L inverter is set up to operate at the fundamental frequency, while the DSCC inverter synthesizes the output voltage references from high-quality waveform with a significant number of voltage levels. Experimental results obtained from a downscaled 10-kVA 380-V prototype driving a full loaded 3.7-kW OEW induction motor are provided to verify the viability of the proposed system.

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).

Unidirectional rectifier based on hybrid modular multilevel cascade converter — Double-star chopper-cells

In this paper a hybrid topology of Modular Multilevel Cascade Converter (MMCC) - Double-Star Chopper-Cells (DSCC) is proposed. This configuration is applied as a unidirectional controlled single-phase rectifier, wherein one of the converter legs is composed by diodes instead of the submodules (SMs) connections. In order to ensure the energy balance among the local SM capacitors, a voltage balancing control strategy is also presented. Besides, a grid current control strategy associated to a method that eliminates zero-crossing distortion caused by the diode leg is proposed, resulting in a power-factor correction (PFC) and a sinusoidal grid current. Experimental results are presented and allow validating the control strategies.

Hybrid single-phase AC-AC Double-Star Chopper-Cells (DSCC) converters with modulation and dc-link voltage ripple improvement

The effects of high-frequency modulation applied to Modular Multilevel Cascade Converter (MMCC) with Double-Star Chopper-Cells (DSCC) can produce high-frequency components across the arm inductors, which are reflected in the DC-link when no common DC-link capacitor is used. The switch-count reduction can be a cost-effective solution in processes of power conversion. This work presents two hybrid single-phase AC-AC DSCC converters based on Voltage Reference Techniques (VRTs), in which can also lower the DC-link voltage ripple using Pulse-Width Modulation (PWM) with Phase-Shifted Carriers (PSCs) on the conventional modular topology. Simulated and experimental results are presented to validate the proposed techniques and topologies.

Multilevel Reduced Controlled Switches AC–DC Power Conversion Cells

This paper presents multilevel ac–dc single-phase power conversion cells for applications in which the regenerative operation is either not required or prohibited. The ac primary power source is a single phase from a permanent magnet generator or from an electrical grid. The cells are composed of two h-bridges in cascade: 1) an unidirectional high-voltage h-bridge with two controlled switches; and 2) two power diodes, processing the active power, and a low-voltage h-bridge with four controlled switches and a floating capacitor. These cells can be part of multiphase systems, in which it is required one cell for each phase. Some examples of application for three-phase systems are given, exploring different ways of connection between the single-phase cells. Simulation and experimental results regarding the proposed cells and conventional h-bridge based ac–dc converters are shown for validation and comparison purposes.

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.

Low-power energy generation systems for two-phase PM machine with reduced-switch-count controlled switches

This paper presents two power generation systems with a two-phase permanent magnet (PM) synchronous machine associated to a rectifier with small number of controlled switches. The topologies have as main purpose converting wind energy into electrical energy for low power applications, providing a great potential to be used in urban areas. They can be used in applications connected to the grid or in the stand-alone mode or feeding a micro grid. Compared with two three-phase generation systems that use reduced number of controlled switches, the proposed topologies permit obtaining sinusoidal machine currents, with low harmonic distortion, using a smaller number of controlled switches. Simulation and experimental results also are presented.

Hybrid nine-level single-phase inverter based on modular multilevel cascade converter

This paper presents a hybrid single-phase inverter based on a modular multilevel cascade converter (MMCC) with double-star chopper cells (DSCC). The proposed inverter is constituted by one five-level (5L) DSCC leg and one two-level (2L) leg, providing a nine-level voltage at its output. For this, a hybrid modulation technique is employed, allowing the DSCC leg to operate at the switching frequency and the 2L leg to operate at the fundamental frequency, which reduces switching losses. Compared to other nine-level cascaded H-bridge inverters, the proposed topology requires only one isolated voltage source and generates less losses in the semiconductors. At last, to investigate the proposed system and control strategy, simulation and experimental results are presented.