M.B.R. Correa

Vector modeling and control of unbalanced electrical systems

In this paper a vector modeling approach is employed to represent the transient and steady-state behavior of unbalanced three-phase (three wires), unbalanced two-phase and single-phase systems containing PWM converters. In the case of the three-phase system, it is decomposed on dq components, by using an appropriate coordinate transformation, and then the vector model is obtained. While in the case of the single-phase system, a fictitious second single-phase system is introduced to obtain the vector model. From the vector model, two vector controllers in the direct and indirect synchronous reference frames are defined. The digital version of this controller in the stationary reference frame is also presented. Simulations and experimental results are presented for a VSI power converter system.

Independent voltage control for series connected six-phase and three-phase induction machines

A lot of relevant concepts related to series connection and independent control of multiphase machines supplied from a single current-controlled voltage source inverter have been recently demonstrated by some researchers. These previous evaluation give a great contribution to further improvements of multimachine series connected applications. Following the initial proposition, which includes an evaluation based on the general theory of electrical machines, this paper evaluates PWM schemes for two-motor series connected motor drive. The goal of this paper is to show how to achieve independent voltage control and to evaluate the switched voltage profile in the motors windings. Scalar and vector approach are addressed and, simulation and experimental results are shown to illustrate details discussed in the paper.

Control of the Single-Phase to Three-Phase Four-leg Converter for Constant Frequency Output Voltage

This paper proposes a control strategy to a reduced switch count single-phase to three-phase converter for constant frequency output voltage applications. The topology allows single-phase to three-phase power conversion for supply three-phase load. The control strategy is proposed to obtain the same voltage rating of a five-leg converter. The system can be used for applications in which the load operates with constant frequency. Pulse-width modulation techniques are developed, introducing the concept of local and general apportioning factor. Experimental and simulated results are presented

Sensorless IFOC for single-phase induction motor drive system

The widespread use of single-phase induction motor has motivated a lot of researchers to investigate alternatives to implement a single-phase induction motor drive (SPIMD) system with low and high performance capability. This paper presents a high performance SPIMD system by using a sensorless approach. This novelty helps reduce the total cost of the system throughout the elimination of the sensor and its instrumentations. In this paper the modelling that allows implement a sensorless SPIMD is presented. Simulation and experimental results show the feasibility of the approach

An application of genetic algorithm and fuzzy logic for the induction motor diagnosis

The aim of this paper is the diagnosis of signatures of rotor broken bars when the induction machine is fed by an unbalanced line voltage. These signatures are given by the complex spectrum modulus of the line current. In order to make the diagnostic, a genetic algorithm is used to keep the amplitude of all faulty lines. Moreover, the fuzzy logic approach allows us to conclude to the load level operating system as to inform the operator of the rotor fault severity. Experimental results proof the performance of this method under various load levels and various fault severities. The conclusion resulting from this study is highlighted and proves the efficiency of the suggested approach.

AC motor drives with a reduced number of switches and boost inductors

This paper presents two three-phase AC motor drives configurations with a reduced component count. The configurations were conceived to operate with a reduced number of switches and boost inductors. The drives provide both bidirectional power flow and power factor control. The paper presents the analysis and control strategy of the systems, including current and PWM voltage controllers. Experimental and simulation results are presented

An Accurate Model by Using the Legendre Polynomial Functions of a Dual Stator Induction Machine Dedicated to the Static Eccentricity Diagnosis

The induction machine takes a preponderant place in many industrial applications due to its low cost and to its robustness. Nowadays, there are several standard schemes for the control of that kind of machine. In order to release a power segmentation and to increase the reliability, many engineers suggest to use multi-phase supplies. Furthermore, they advocate the dual stator winding induction machine (DSWIM), in which the two three phase stator winding systems are shifted by any angle. The main purpose of our investigation is to propose two models of the DSWIM under static eccentricity by using two shapes of the air- gap function and their associated permeance functions. The first method uses a classical form of the air-gap function. The second one gives a novel expression of the air-gap function involving a Legendre polynomial development that is obtained thanks to a geometrical study of the permeance function. Simulated and experimental set-up will prove the effectiveness of both models by choosing the Motor Current Signature Analysis (MCSA) as the diagnosis tool.

A new approach to generate PWM patterns for four-switch three-phase inverters

This paper presents a new method to generate pulse width modulated signals to control four switch three phase inverters. The proposed method provides a simple scheme to select three or four vectors to synthesize the desired output voltage. The method is based on the so called space vector modulation but the paper also presents its scalar version. The paper presents a comparative study where the different vector combinations are investigated. The paper also discusses how the use of the wye and delta connections of the machine windings affects the implementation of the pulse width modulator. Simulation and experimental results are presented to corroborate the analytical developments.

Single-phase universal active power filter based on AC/AC converters

This paper presents four single-phase universal active power filters (UAPF) topologies with 4, 5, 6 and 7 legs. The proposed systems are based on AC/AC converters with two transformers. They are suitable to improve the harmonic distortion in the grid currents and a voltage compensation. The filter uses a combination of two series filters and one shunt filter sharing a single DC-link. The proposed active filters are capable of generating input and output voltages with low harmonic content and consists of low-power switches. The complete control system, including the PWM techniques based on vector approaches, is developed. Simulation and experimental results are shown for validation purposes.

A complex spectral analysis of the stator current dedicated to the defects monitoring of squirrel cage induction motors

Nowadays, the induction motor is an important element in industrial process in terms of safety and efficiency. In order to limit the cost induced by a defect, we have to make an early detection. Consequently, the earlier incipient faults will be detected the cheaper remediable faults will be. So, one of the widespread method to monitor the process is the spectral analysis of the stator current. Usually, the real fast Fourier transform (FFT) is used. Despite its waning achievement in regards of on-line methods, the complex FFT gives more information about the healthy state of the motor. So, a comparison of these two approaches in this paper will allow the users to better conclude or not to failure of the induction motor. Moreover, a sliding version of the discrete Fourier transform is conceivable even if the signal to analyse is real or complex. This technique is highly recommendable when updated spectrum is necessary at each sampling time. Experimental results show the efficiency of the complex FFT in comparison to the classical one.