Armando Cordeiro

A Speed Controller for a Two-Winding Induction Motor Based on Diametrical Inversion

The objective is to control the speed of a single- or two-phase induction motor using diametrical inversion (DI) of the stator voltages. DI is a particular reversal of the sequence phases characterized by replacement of the voltage phasor by another that is diametrically opposed to it and rotating in the opposite direction. Every DI is provoked by a change in the sign of the simplest switching function (speed error) of a sliding mode. These changes cause jumps of 180° of the stator voltage phasor and successive discontinuities of its angular velocity. The main and auxiliary windings are always connected, the speed-error sign decides the rotating field direction, and so, the actual rotor velocity can be reduced (braked) or increased (accelerated). The motor is fed by a rectifier associated with a three-phase inverter. The common point of the windings is connected to the inverters middle leg, which is switched at high frequency with a duty cycle of 50%. The core of the drive command is a 16-b dsPIC device, which receives the speed-error sign and generates the appropriate pulsewidth modulated signals to the three-phase inverter. Matlab/Simulink simulation and experimental results showed a good performance of the speed controller based on the DI.

Fault-tolerant design of a classical voltage-source inverter using z-source and standby redundancy

This paper proposes modifications of the classical two-level three-phase voltage-source inverter topology structure with the aim of increasing its reliability to safety-critical applications. This solution intends to achieve fast changing and “soft” commutation between main and redundant branches through the combination of mechanical commutators and power devices. Also, important modifications in the power supply stage will allow to withstand severe short-circuit conditions. With those modifications, the energy processing capability can be maintained for most common failure modes. Several aspects of failure modes, detection and isolation processes within voltage-source inverters are also discussed regarding the requirements of safety related applications. Experimental results from a prototype are included to confirm the validity of the proposed solution.

Quasi-Z-Source Inverter With a T-Type Converter in Normal and Failure Mode

This paper presents a three-phase multilevel quasi-Z-source inverter (qZSI) topology operating in normal and fault-tolerant operation mode. This structure is composed by two symmetrical quasi-Z-source networks and a three-phase T-type inverter. Besides the intrinsic advantages of multilevel voltage source inverters, the proposed structure is also characterized by their semiconductor fault tolerance capability. This feature is only obtained through changes on the modulation scheme after the semiconductor fault and does not require additional extra-phase legs or collective switching states. In certain fault types, the reduction of the output power capacity will be compensated by the boost characteristic of the qZSI. The fault-tolerant behavior of the proposed topology is demonstrated by several simulation results of the converter in normal and fault condition. To validate the characteristics of this multilevel qZSI, an experimental prototype was also built to experimentally confirm the results.

Anti-slip wheel controller drive for EV using speed and torque observers

A wheel slip controller of an electric vehicle with two independent rear wheel drives is presented. The vehicle dynamic model and the proposed torque controller for the DC motors are also presented. The speed and torque observer solution proportionate the necessary external torque estimation to the anti-slip wheel controller. The wheel slip is based on the comparison of the real vehicle velocity and the estimated velocity given by the speed observer.

Detection and Diagnosis Solutions for Fault-Tolerant VSI

This paper presents solutions for fault detection and diagnosis of two-level, three phase voltage-source inverter (VSI) topologies with IGBT devices. The proposed solutions combine redundant standby VSI structures and contactors (or relays) to improve the fault-tolerant capabilities of power electronics in applications with safety requirements. The suitable combination of these elements gives the inverter the ability to maintain energy processing in the occurrence of several failure modes, including short-circuit in IGBT devices, thus extending its reliability and availability. A survey of previously developed fault-tolerant VSI structures and several aspects of failure modes, detection and isolation mechanisms within VSI is first discussed. Hardware solutions for the protection of power semiconductors with fault detection and diagnosis mechanisms are then proposed to provide conditions to isolate and replace damaged power devices (or branches) in real time. Experimental results from a prototype are included to validate the proposed solutions.

Combining mechanical commutators and semiconductors in fast changing redundant inverter topologies

This paper presents some solutions for fast changing and “soft” commutation between main and redundant branches in fault-tolerant inverter topologies through the combination of mechanical commutators and semiconductors. The present study deals with redundant two-level three-phase voltage-source inverters. Experimental results confirm the validity of the proposed solutions.

Fault-tolerant design for a three-level neutral-point-clamped multilevel inverter topology

This paper presents a modified topology of the neutral-point-clamped inverter suitable to increase the converter reliability in safety-critical applications. With the proposed scheme, the energy processing capacity can be maintained even for multiple failure modes. Its fault-tolerant ability results from redundancy of power devices and from modifications in the control strategy. The theoretical validity of the proposed solution is confirmed by simulation results.

Power electronics didactic modules for direct current machine control

Several didactic modules for an electric machinery laboratory are presented. The modules are dedicated for DC machinery control and get their characteristic curves. The didactic modules have a front panel with power and signal connectors and can be configurable for any DC motor type. The three-phase bridge inverter proposed is one of the most popular topologies and is commercially available in power package modules. The control techniques and power drives were designed to satisfy static and dynamic performance of DC machines. Each power section is internally self-protected against misconnections and short-circuits. Isolated output signals of current and voltage measurements are also provided, adding versatility for use either in didactic or research applications. The implementation of such modules allowed experimental confirmation of the expected performance.

A phasor speed control of a single or two phase induction motor

This paper is focused on the speed control of a single or two phase induction motor using a diametrical inversion (DI) of the stator voltages. The changes in the speed error sign are responsible for each DI which inverts the stator voltage phasor and its angular velocity. The main and the auxiliary windings are always connected and thus the speed error sign allows to determinate the rotating field direction. The motor is fed by a rectifier associated with a three-phase inverter. The core of the drive command its a 16-bit dsPIC device, which receives the speed error sign and generate the appropriate PWM reference voltages signs to the three-phase inverter. Simulation and experimental results allow assume a good performance.

A Microcontroller Sensorless Speed Control of a Direct Current Motor

It is described a sensorless direct current motor drive. The speed was controlled using sliding mode with a first- order differential equation based on the speed error. The result of the switching function was integrated with a current limitation using a logic equation. The current limitation assures the machine protection and the output of the logic block is the signal of the voltage to apply on the motor armature. Instead to measure the rotor speed it was analytically inferred an external torque and speed observer. The motor is fed by a classic insulated gate bipolar transistor converter module. All gating signals for power switches are determined at every sample instant by a single microcontroller, which collects information and analyze voltage and current data from the motor to perform the necessary speed and torque estimation.