José Renes Pinheiro

Hybrid Multilevel Converters: Unified Analysis and Design Considerations

The concept of hybrid multilevel converters has been generalized for different arrangements of direct-current voltage levels, modulation strategies, topologies of series-connected cells, and/or semiconductor technologies to optimize the power processing of the overall system. Therefore, a given number of levels can be synthesized by several multilevel configurations, significantly increasing flexibility and complexity in the design of hybrid multilevel converters. However, a generalized design methodology to define the main parameters of these topologies for distinct design criteria has not yet been presented. To overcome this lack, this paper presents a comparative analysis among various hybrid multilevel topologies, and it proposes some design considerations for distinct applications. Consequently, this paper constitutes a useful basis for defining an adequate hybrid arrangement for any application

The three-level ZVS-PWM DC-to-DC converter

A novel high-frequency DC-to-DC power converter for high voltage and high power is introduced which features zero voltage switching (ZVS), operation at constant frequency, regulation by pulse width modulation (PWM), and low RMS current stress upon power switches. Its greatest attribute, in comparison with the full-bridge (FB-ZVS-PWM) converter, is that the voltage across the switches is half of the input voltage, This property is achieved due to the use of a three-level leg in place of the conventional two-switch leg. Operation, analysis, design procedure and example, and simulation are presented. A prototype operating at 100 kHz, rated at 600 V input voltage, and 1.5 kW output power and 25 A output current has been fabricated and successfully tested in the laboratory. The measured efficiency at full load was 93%. >

Wide load range three-level ZVS-PWM DC-to-DC converter

A new three-level ZVS-PWM DC-DC converter operating in a wide load range is introduced. It is used for high-voltage and high-power applications and has as its main features: zero-voltage-switching (ZVS) from no load up to full load, operation at constant frequency, regulation by pulse-width modulation (PWM), and low RMS current stress upon power switches. Its greatest attribute is that the voltage across the switches is half the value of the input voltage. A prototype operating at 100 kHz, rated at 600 V input voltage, 1.5 kW output power, and 25 A output current, has been fabricated and successfully tested in the laboratory. The principle of operation, theoretical analysis, design procedure, and an example, along with experimental results, are presented.<<ETX>>

Comparison of digital control techniques with repetitive integral action for low cost PWM inverters

This paper presents a comparison among digital control techniques with repetitive integral action applied to voltage-source PWM inverters. As a result of the repetitive integral action, these digital control schemes can reduce steady-state errors and distortions caused by unknown periodic disturbances, which usually result from the input source and output load. Moreover, these digital control schemes measure only the output voltage, decreasing the amount of sensors and the overall system cost. The control laws, stability analysis, common and distinguishing features of these control algorithms are discussed. Experimental results from a PWM inverter (110 V/sub RMS/, 1 kVA) controlled by a low cost microcontroller are presented to demonstrate the control techniques performance under different load conditions, output filters and command strategies.

A ZCT auxiliary commutation circuit for interleaved boost converters operating in critical conduction mode

This paper investigates a power-factor-corrector (PFC) circuit based on interleaved boost converters in critical conduction mode (C-DCM) with a zero current transition (ZCT) circuit. By using the interleaved converters technique, the input current ripple is minimized, and due to the operation in C-DCM, the main switches turn-on occurs naturally under zero current and the reverse recovery losses of the diodes are minimized. The use of auxiliary commutation circuits provides ZCT at main switches turn-off, minimizing the related turn-off losses. The command circuit of the converters has been implemented by using a single erasable programmable logic device (EPLD) EPM7128SLC84-15. Operating principles, theoretical analysis, design guidelines and a design example are described and verified experimentally by a 1.2 kW prototype. Finally, the measured losses in the PFC interleaved boost converters with and without the proposed ZCT commutation cell, as well as a previously published ZCT cell are presented and discussed.

Analysis and Design of a New High-Efficiency Bidirectional Integrated ZVT PWM Converter for DC-Bus and Battery-Bank Interface

This paper proposes a high-efficiency bidirectional integrated zero-voltage transition (iZVT) pulsewidth-modulation (PWM) converter for dc-bus and battery-bank interface. The proposed converter can operate as battery charger when the utility is within its acceptable voltage range and can supply energy to critical loads when the utility fails. The converter practically eliminates both low- and high-frequency current ripple on the batteries, thus maximizing battery life without penalizing the volume of the converter. Moreover, soft switching of all switches is achieved using the proposed integrated auxiliary commutation circuit (iACC). Just one iACC is used to provide soft-switching conditions for the three converters that compose the system: the preregulator (boost), the battery charger (bidirectional converter operating as a buck), and the backup converter (bidirectional converter operating as a boost). This auxiliary circuit has few components and low reactive energy, increasing the systems overall efficiency. Experimental results based on a 580-W prototype are presented to validate the analysis and the proposed design procedure and to demonstrate the performance of the proposed approach

Comparison of Neutral-Point-Clamped, Symmetrical, and Hybrid Asymmetrical Multilevel Inverters

This paper presents a comparison of three topologies of multilevel inverters applied to drive an induction motor of 500 kVA/4.16 kV rating. The multilevel inverters analyzed are the following: a neutral-point-clamped inverter, a symmetrical cascaded multilevel inverter, and a hybrid asymmetrical cascaded multilevel inverter. The performance indexes used in the comparison are total harmonic distortion, first-order distortion factor, second-order distortion factor, common-mode voltage, semiconductor power loss distribution, and heat-sink volume. The multilevel inverters are designed to present 99% efficiency at the nominal operating point, and the aforementioned performance indexes are compared for distinct values of amplitude modulation depth.

A high efficiency autonomous street lighting system based on solar energy and LEDs

This work presents an autonomous street lighting system based on solar energy as primary source, batteries as secondary source, and lighting emitting diodes (LEDs) as lighting source. This system is being presented as an alternative for remote localities, like roads and crossroads. Besides, it presents high efficiency, because all power stages are implemented in DC current. The design of LEDs fixture, in order to replace a 70 W high pressure sodium (HPS) lamp, is performed. This design takes into account the human eye response in scotopic conditions. LEDs driver and battery charger experimental results are presented. The battery charger presents three control modes: maximum power point tracker (MPPT) mode; constant current mode; and constant voltage mode. The control mode depends on the battery state (charged/discharged), and solar irradiance level.

Space vector modulation for voltage-source inverters: a unified approach

This paper presents a unified approach of the space vector modulation for voltage-source inverters. To demonstrate the proposed unified approach, five fundamental inverters topologies are analyzed: single-phase full-bridge, three-phase three-wire, three-phase four-wire, three-phase four-leg and three-phase three-level inverters. Switching vectors, separation and boundary planes in the inverter output space as well as decomposition matrices and possible switching sequences are derived for each one of these inverters. Experimental results are shown to validate the proposed unified approach.

Control strategy of an interleaved boost power factor correction converter

Power factor correction interleaved boost converters provide a reduction of the inductor volume and weight when compared with the conventional PFC boost converter. However, to achieve these benefits, proper current sharing and current ripple minimization must be ensured. This paper proposes a controller based on the Lyapunov-likelihood control technique for interleaved boost converters (IBC) that ensures output voltage regulation and proper current share for each boost cell. In addition, a switching logic scheme for the IBC is developed to guarantee the input current ripple minimization. Extensive simulations are presented to demonstrate the performance of the proposed control and switching logic scheme.