Andres O. Salazar

A bearingless method for induction machines

A bearingless induction motor system that uses standard windings is proposed. The theoretical assumptions are tested experimentally using a four-pole, two-phase machine without one mechanical bearing. The basic idea is the modulation of the stator winding currents to achieve positioning and rotary forces. Shaft deviations smaller than 0.5 mm at speeds of 4000 rpm are reached during the initial laboratory tests. >

Real time leak detection system applied to oil pipelines using sonic technology and neural networks

This work proposes a leak detection system using sonic technology, wavelet transform and neural networks to decompose and analyze pressure signals from oil pipelines in real time. The similarity between pressure and sound signals makes it possible to treat the first through digital filtering and wavelet decomposition together with a neural network to characterize and classify leak profiles. The leak detection system logic is embedded on 32 bit/150 MHz floating point DSPs. This system uses piezoresistive sensors, converters to the communication interface (Ethernet) and GPS devices, which are responsible for synchronizing reports and leak alarms. The DSPs code was written using ANSI C language.

A Wavelet Approach to Pipeline Leak Detection by Pressure Analysis

One of the most challenging tasks in an oil field is implementation of a software-based leak detection system on a multi-phase flow pipeline. When a leak occurs in a multi-phase flow pipeline, the flow cannot be measured with accuracy. So, none of the various pipeline leak detection methodologies can offer good performance on a multi-phase flow pipeline. This paper will discuss implementation of a leak detection system in a particular oil field using state-of-the-art signal processing techniques to apply to the data collected in a oil pipeline. This leak detection system is still in development and uses a more practical approach to the problem than traditional methods and was implemented on a PC under the Windows operating system. Windowing, joint time-frequency analysis and wavelets were considered to develop methods of detecting leaks by watching for the wavefront. The idea behind these techniques is to cut the signal of interest into several parts and then analyze the parts separately. It is impossible to know the exact frequency and the exact time of occurrence of the leak frequency in a signal. In other words, a leak signal can simply not be represented as a point in the time-frequency space. It is very important how one cuts the signal to implement the analysis. The wavelet transform or wavelet analysis is probably the most recent solution to overcome the shortcomings of the Fourier transform. The wavelet transforms are used to perform atomic decompositions of the pressure signal that comes from a single point of a pipeline. A number of time-frequency decompositions are attempted. What is expected of this decomposition is that it fits the perceptible changes in the pressure and then an Artificial intelligent System (AIS) decides if the variations in the signal are inherent (common-cause variations) or external to the process (failed instrument, occurrence of a leak, causes that are not part of the process). The AIS learns about continual changes in the pipeline. This is useful as pipeline operation always changes and instrument drift could occur over a long time period.Copyright

WINSS: A simulation tool of the IEEE 802.15.4 Standard for Network Simulator 2

Low-cost technology that can monitor a wide range of environments, Wireless Sensor Network (WSN) has become increasingly common and studies on it have increased a lot. Due to the cost and time required to deploy a WSN in physical environments, the network simulators, such as the popular Network Simulator 2 (NS-2), have been adopted for evaluation of WSNs. NS-2 is a widely accepted and used network simulation tool. The IEEE 802.15.4 wireless technology has been used for implementation of WSNs and NS-2 supports simulation of WSNs based on the IEEE 802.15.4 standard, but the execution of simulations on this standard may not be an easy task for new users. This paper presents WINSS (Wireless Network Sensor Simulator), a simulation tool of the IEEE 802.15.4 Standard for NS-2.

Hybrid fuzzy and robust controller applied to a DC-DC boost converter

This paper purposes a hybrid control method applied to a DC-DC Boost converter in order to maintain a constant output voltage and ensure the supply of good power quality to the load. The hybrid controller consists of a fuzzy supervisor which mixes control signals of two types of controllers: robust and fuzzy. Each one of these controllers has good performance in certain operational conditions. The supervisor determines the ideal proportion of the action provided by the controllers in each operational condition. The simulations show that fuzzy and robust control signals can be mixed to provide a good power quality to the load ensuring fast transient response and zero steady-state error due to input voltage and load variations.

Development and implementation of WSN embedded systems units to be applied on Plunger Lift oil elevation method

The Wireless Sensor Network (WSN) methods applied on the oil elevation unit present as a technical-scientific demand growing area, in view of the improvements that can be carried forward to existing processes. This work has a main objective to present the development of embedded systems dedicated to a wireless sensor network based on IEEE 802.15.4 standard, which applies the Zigbee protocol between sensors, actuators and the PLC (Programmable Logic Controller), providing low cost, low power consumption, reliability and easy installation and maintenance, solving the problems present in the deployment and maintenance of current physical communication units based on oil elevation units that uses Plunger Lift method. Embedded systems developed for that application is responsible for interpreting the information from sensors and actuators to control the standard devices as well, as using the Modbus protocol to make this network becomes transparent to the PLC, responsible for being controlling the production and delivery information to a supervisory.

Experimental analysis of a series resonant converter for a plasma inertization plant

This article showed a DC-AC converter series resonant (CSR) operating high frequency, using IGBTs and soft-switching technique (Zero Voltage Switching — ZVS). This full-bridge converter composed of four identical parallel modules operating at 100 kHz to get 400kHz as a final frequency in the output. Operating principles, experimental analyses are described, which enables the experimental assembly of the series resonant converter in the plant.

Proposal of a AC/DC converter with unitary power factor for a thermal plasma torch system

This paper describes the project development and the construction of a 50 kW AC/DC PWM power supply with power factor correction for use with plasma inertization plant. The main power circuitry is built on a industrial IGBTs three-phase bridge rectifier module configured in a boost regulator topology and supplies by means of an electronic chopper, the 850 Vdc link. To attend the Brazilian electrical standard with regard to power factor and harmonic current injection in the electrical line, this power supply is provided of a power factor correction using a space-vector PWM. All the control was implemented in a TMS320LF2812A Evaluation Module (EVM). A remote PC microcomputer using a man-machine interface was connected to the DSP in order to supervise the parameters of the system.

Adaptive Wavelet Coding Applied in a Wireless Control System

Wireless control systems can sense, control and act on the information exchanged between the wireless sensor nodes in a control loop. However, the exchanged information becomes susceptible to the degenerative effects produced by the multipath propagation. In order to minimize the destructive effects characteristic of wireless channels, several techniques have been investigated recently. Among them, wavelet coding is a good alternative for wireless communications for its robustness to the effects of multipath and its low computational complexity. This work proposes an adaptive wavelet coding whose parameters of code rate and signal constellation can vary according to the fading level and evaluates the use of this transmission system in a control loop implemented by wireless sensor nodes. The performance of the adaptive system was evaluated in terms of bit error rate (BER) versus Eb/N0 and spectral efficiency, considering a time-varying channel with flat Rayleigh fading, and in terms of processing overhead on a control system with wireless communication. The results obtained through computational simulations and experimental tests show performance gains obtained by insertion of the adaptive wavelet coding in a control loop with nodes interconnected by wireless link. These results enable the use of this technique in a wireless link control loop.

One Cycle Control applied to a stand-alone photovoltaic system for DC microgrid applications

Distributed Energy Resources (DER) are the basic units for storage and distribution in Microgrids. A DER unit can be of a hybrid type including a primary energy source (distributed generation - DG) and storage (distributed storage - DS). A hybrid type unit is proposed in this paper. The unit consists of a dc-dc buck-boost converter that tracks the maximum power supplied by a photovoltaic panel, a dc-dc boost converter that regulates the voltage of the microgrid dc bus and a bidirectional dc-dc buck-boost converter that controls the power flow in the unit, charging or discharging a battery bank. The control of these converters must consider the battery protection against voltage surges and transients, so as the protection of the loads connected to the dc bus, when the battery supplies the energy stored. The One-Cycle Control (OCC) technique has been used jointly the switching converters to allow fast response to transients, no overshoots and zero steady state error. The objective of this work is to use OCC technique in the controller of these converters in order to quickly track down the maximum power point, charge the battery bank when they are discharged, and to supply the battery energy to the loads when necessary, ensuring protection to the battery and to the loads connected to the microgrid.