Showing papers presented at "International Symposium on Industrial Electronics in 2003"

An interleaved boost DC-DC converter with large conversion ratio

Abstract: A new PWM dc-dc converter is introduced in which large voltage step-up ratios can be achieved without high duty-cycle, with low voltage and current stress and without transformer. The proposed circuit is an extension of the boost interleaved converter, incorporating a multistage capacitor multiplier. A simple nondissipative snubber can be used reducing the reverse recovery current of the diodes and also obtaining low turn-on and turn-off losses. The modularity of the structure allows the increment of the current, voltage and power levels, using the same range of components and maintaining high efficiency, only increasing the number of series and parallel stages. The paper gives a theoretical analysis, and experimental data on a 400 W example that was built and tested: 24 Vdc input, 200 Vdc output, and 40 kHz switching frequency. The measured performance agreed well with the theoretical predictions and the measured efficiency obtained is equal to 95% at full load.

Predictive DC voltage control of single-phase PV inverters with small DC link capacitance

Abstract: This paper proposes a novel control method for DC voltage in single-phase voltage-source inverters fed by constant-current or constant-power sources. The technique predicts the inverter power require to correct a DC voltage error within one fundamental AC cycle. This is based on the power balance between DC input and AC output, and the energy stored in the DC link capacitor. The fast response means a smaller capacitor can be used, and operation with a large double-line-frequency ripple on the DC bus is possible without causing distortion of the AC output current. This scheme is suitable for applications where substantial DC link buffer energy is unnecessary, e.g.: grid-connected photovoltaic generators. The reliability and lifetime of the inverter can be significantly improved if a non-electrolytic type capacitor is used. Experimental results are presented that verify the inverter operation.

p-q Theory power components calculations

Abstract: The "generalized theory of the instantaneous reactive power in three-phase circuits", proposed by Akagi et al., and also known as the p-q theory, is an interesting tool to apply to the control of active power filters, or even to analyze three-phase power system in order to detect problems related to harmonics, reactive power and unbalance. In this paper it will be shown that in three phase electrical systems the instantaneous power waveform presents symmetries if 1/6, 1/3, 1/2 or 1 cycle of the power system fundamental frequency, depending on the system being balanced or not, and having or not even harmonics (interharmonics and subharmonics are not considered in this analysis). These symmetries can be exploited to accelerate the calculations for active filters controllers based on the p-q theory. In the case of the conventional reactive power or zero-sequence compensation, it is shown that the theoretical control system dynamic response delay is zero.

Generalized geometric triangulation algorithm for mobile robot absolute self-localization

Abstract: Triangulation with active beacons is widely used in the absolute localization of mobile robots. The geometric triangulation algorithm allows the self-localization of a robot on a plane. However, the three beacons it uses must be "properly ordered" and the algorithm works consistently only when these beacons within the triangle form the robot. This paper presents an improved version of the algorithm, which does not require beacon ordering and works over the whole navigation plane except for a few well-determined lines where localization is not possible.

A control strategy for unified power quality conditioner

Abstract: This paper presents a control strategy for a unified power quality conditioner. This control strategy is used in three-phase three-wire systems. The UPQC device combines a shunt-active filter together with a series-active filter in a back-to-back configuration, to simultaneously compensate the supply voltage and the load current. Previous works presented a control strategy for shunt-active filter that guarantees sinusoidal, balanced and minimized source currents even if under unbalanced and/or distorted system voltages, also known as "sinusoidal fryze currents". Then, this control strategy was extended to develop a dual control strategy for series-active filter. Now, this paper develops the integration principles of shunt current compensation and series voltages compensation, both based on instantaneous active and non-active powers, directly calculated from a-b-c phase voltages and line currents. Simulation results are presented to validate the proposed UPQC control strategy.

New direct power control of three-phase PWM boost rectifiers under distorted and imbalanced line voltage conditions

Abstract: The three-phase PWM boost rectifier is an interesting solution thanks to advantages as: bi-directional power flow, low harmonic distortion of line current, regulation of input power factor to unity, adjustment and stabilization of DC-link voltage. This paper proposes a new direct power control for this kind of converter using space vector modulation (DPC-SVM). The active and reactive power is used as the pulse width modulated (PWM) control variables instead of the three-phase line currents ever used. Moreover, line voltage sensors are replaced by virtual flux (VF) estimator. The theoretical principle of this method and the synthesis of the active and reactive power controllers are discussed. The steady state operation, dynamic results and behaviour under distorted and imbalanced line voltage conditions that illustrate the performance of the DRC-SVM are presented. It is shown that the proposed method exhibits several features as: simple tuning procedure of PI power controllers, good dynamic response, constant switching frequency and sinusoidal line current when supply voltage is non ideal. Simulation and experimental results have proven excellent performances and verify the validity of the proposed system.

A comparative evaluation of motor drive topologies for low-voltage, high-power EV/HEV propulsion systems

Abstract: The recent adoption of the 42 V powernet standard for the next generation of vehicles has focused substantial research effort into the design of electric machines for light hybrid vehicles. However, research investigating the merits of topology selection for this application has been sparse. This paper investigates the potential performance benefits, which could be realized by adopting a different inverter topology. This paper discusses the merits of delta-connected motors, bipolar inverters and cascaded inverters when compared to a standard inverter. The flexibility provided by adopting a non-standard topology can produce a better overall design when one or more of the design specifications are proving difficult to meet economically with the standard topology. As a particular design example, this paper shows that a cascaded inverter topology driving an open winding motor can increase the high-speed power density of an induction motor by 73%. For an interior permanent magnet motor, this paper shows that this topology can increase low speed torque by 9% and high-speed power by up to 300%.

Selective harmonic eliminated pulse-width modulation technique (SHE PWM) applied to three-level inverter/converter

Abstract: The main interest of this study has been granted to the selective harmonic eliminated pulse width modulation technique, SHE PWM, for the control of single-phase and three-phase full-bridge three-level inverters. This study makes for any angle number (even or odd) of switches that composes the inverter, for purpose of comparison with the results found for only odd number. We explain the resolution method procedure of the nonlinear equation systems in order to achieve the appropriate switching angles. The method of obtaining the best starting point is also described to overcome the problem of the choice of these points, which is one of most difficult tasks associated with the SHE PWM. Finally we validated the obtained results through some simulations by using MATLAB package.

Low-cost power quality monitor based on a PC

Abstract: This paper presents the development of a low-cost digital system useful for power quality monitoring and power management. Voltage and current measurements are made through Hall-effect sensors connected to a standard data acquisition board, and the applications were programmed in LabVIEW/spl trade/ , running on Windows in a regular PC. The system acquires data continuously, and stores in files the events that result from anomalies detected in the monitored power system. Several parameters related to power quality and power management can be analyzed through 6 different applications, named: "scope and THD", "strip chart", "wave shape", "sags and swells", "classical values" and "p-q theory". The acquired information can be visualized in tables and/or in charts. It is also possible to generate reports in HTML format. These reports can be sent directly to a printer, embedded in other software applications, or accessed through the Internet, using a Web browser. The potential of the developed system is shown, namely the advantages of virtual instrumentation, regarding to flexibility, cost and performance, in the scope of power quality monitoring and power management.

Analysis and software implementation of a robust synchronizing circuit PLL circuit

Abstract: This paper presents the analysis and software implementation of a robust synchronizing circuit - PLL circuit - designed for using in the controller of active power line conditioners. The basic problem consists in designing a PLL circuit that can track accurately and continuously the positive-sequence component at the fundamental frequency and its phase angle, even when the system voltage of the bus, to which the active power line conditioner is connected, is distorted and/or unbalanced. The fundaments of the PLL circuit are discussed. It is shown that the PLL can fail in tracking the system voltage during the startup, under some adverse conditions. Moreover, it is shown that oscillations caused by the presence of sub-harmonics can be very critical and can pull the stable point of operation synchronized to that sub-harmonic frequency. Oscillations at the reference input are also discussed, and the solution of this problem is presented. Finally, experimental and simulation results are shown and compared.

A radiation-hard phase-locked loop

Abstract: Phase-locked loops (PLLs) are often used as frequency multiplier for generating high frequency clock signals. In space application, however, performance of the normal PLL is degraded due to the radiation effects. In this paper, several aspects of a rad-hard PLL are investigated, including radiation effects, radiation hardening techniques, PLL building blocks and the overall performance. This circuit is developed using the Peregrine 0.50 /spl mu/m SOS/SOI process. The post-layout simulation result indicates that the circuit can be used to generate 100 M - I80 MHz programmable clock signal under radiation conditions with process, temperature and voltage variations. The maximum peak to peak jitter is less than 100 ps while the maximum lock-in time is less than 20 us under typical conditions.

Furling control for small wind turbine power regulation

Abstract: In this paper, we analyze the steady-state performance and the impact on the power system of the dynamics of small wind turbines with power regulation based on furling control. Using an example of battery charging wind turbine system, we develop its model. In this model, we introduce damping as a component of the restraining moment. This is a novel concept that is not used in the current wind turbine designs. To investigate the merit of this concept, we perform a simulation study using the RPM-Sim simulator. The study shows that such damping improves the response but we should consider a trade-off between maximizing the wind power capture and minimizing the fatigue damage effects that result from the bang-bang operation. Then, we study the battery charging system with the peak power tracker (PPT). Finally, we present a simulation study of two utility-connected wind turbine systems with furling. We considered the operation of the system without and with the PPT. In the first case study, we use the gain of a DC/DC converter to implement the peak power tracking. In the second case study, we eliminate the DC/DC converter.

Intermittent failure diagnosis in industrial processes

Abstract: Intermittent failure diagnosis based on discrete event system (DES) in industrial processes is studied. Intermittent failures are defined as failures that can automatically recover once they have occurred. In this paper this sort of failures are modeled and some characteristic parameters are defined. The original approach to diagnose permanent failures is revisited and extended in order to include new diagnosis skills in the diagnosers. The developed methodology is applied to a classical industrial subprocess system composed by a pump and a valve. The developed diagnoser and this example are simulated in Matlab, employing Simulink for the continuous model and stateflow for the DES diagnoser.

Sliding mode control for DC/DC converters: a new sliding surface

Abstract: In this paper a controller based on the variable structure theory is analyzed: the sliding mode control. The sliding mode control was proposed to control dc/dc converters, due to the good characteristics introduced to the complete system. In order to regulate the output voltage, the sliding mode control require a current loop in order to assure the stability of the system, the inclusion of this extra loop increases the cost. This paper presents an alternative method to obtain the good characteristics of the control strategy without the use of current sensors.

Harmonic voltage reduction using a series active filter under different load conditions

Abstract: This paper proposes a series active filter using a simple control technique. The series active filter reduces the terminal harmonic voltages, supplying linear or even non-linear loads with a good quality voltage waveform. The operation principle, control strategy and theoretical analysis of the active filter are presented. These aspects were proven by the results of numerical simulations. Experimental results of the series active filter demonstrated its good performance under different load conditions.

Power electronics for power quality improvements

Abstract: Control of most of the industrial loads is mainly based on semiconductor devices, which causes such loads to be more sensitive against power system disturbances. Thus, the power quality problems have gained more interest recently. This paper presents a review of some the disturbances, on the source side that may cause problems on the load side. Focus is given on problems associated with voltage dips as voltage dips have been reported to be the most severe problems to industrial loads. Solutions towards such problems using power electronics equipment are explored.

A new modular hybrid power system

Abstract: This paper presents a new modular hybrid power system incorporating photovoltaic and small scale wind generators connected to an AC bus. The system is based on voltage source inverters using both current control and voltage control. Preliminary experimental and simulation results are included.

Bipolar reference for PWM control of a single-phase shunt hybrid power filter

Abstract: In this paper, a new bipolar reference control is applied to a single-phase shunt hybrid power filter (SPSHPF). It is implemented with pulse width modulation, PWM, in order to compensate harmonics and reactive power generated by non-linear loads. This method uses a residual signal constructed from the comparison between the supply current and its desired value. The SPSHPF includes power factor correction capacitor connected in series with a transformer. A single-phase current controlled voltage source inverter feeds the primary winding of the transformer. The PWM control technique adopted is based on two comparisons of a triangular high frequency carrier signal and the source harmonic current. This harmonic signal namely +/spl thetav/ and its negative value -/spl thetav/ are used, at the same instant, in the comparison process to generate the gate signals of the semi-conductor devices. By using the averaging technique, a direct consequence of this proposed PWM control is that the transfer function of the SPSHPF becomes a pure gain. Simulation results using power system blockset toolbox PSB of Matlab verified the effectiveness of the proposed control algorithm.

Obtaining the magnetic characteristics of an 8/6-switched reluctance machine: FEM analysis and experimental tests

Abstract: This paper describes the step-by-step procedure for modeling an 8/6 switched reluctance machine. Starting from establishing the geometry of the machine, a finite element modeling approach is initially developed to compute the flux linkage/current/rotor position relationship extracting proper and mutual inductances, also its torque and field distribution characteristics. Experimental tests are performed to obtain the magnetic characteristics of the machine, comparing, correcting, and discussing the results obtained with those of FEM analysis.

Application of image processing techniques in the characterization of plant leafs

Abstract: The number of applications using machine vision and digital image processing techniques in the agricultural sector is increasing rapidly. These applications include land/aerial remote sensing of crops, detection and recognition of pathological stress conditions, shape and color characterization of fruits, among many other topics. In fact, quantification of the visual properties of horticultural products and plants can play an important role to improve and automate agricultural management tasks. In this paper, is described a plant leaf characterization system based on a personal computer. This system uses a digital scanner to acquire leaf images with a resolution of 150 dpi. These images are afterwards processed in order to compute some leaf characteristic parameters, such as: leaf area and perimeter, existence of holes, width and length. With the implemented algorithms the errors between the measurements and the real values were typically less than /spl mnplus/3% and /spl mnplus/2.5% for the area and linear measurements, respectively. These tests and results were realized using sets of known size images and leaf images that were measured with the proposed system and with a commercial calibrated leaf area system LiCor from Delta-T devices.

Remote laboratory

Abstract: Remote laboratory implements an environment monitoring system via Internet. In the monitored environment, a luminosity sensor that is connected to an analog/digital converter (ADC) is installed. This ADC is linked to an "intelligent module" that contains an Ethernet chip, capable of establishing a TCP/IP communication. Data are acquired from AD converter and sent via TCP/IP LAN to a data base server, that aided by specific programs developed in open language, manipulate and publish them on a common HTML - hyper text mark-up language - browser when on demand of a client.

Integration of field devices using field device tool (FDT) on the basis of electronic device descriptions (EDD)

Abstract: In future, the integration of field devices can realized vendor-independent on the basis of field device tool (FDT) specification of the ZVEI and the PNO. Today, business and presentation logic of field devices are represented in electronic device descriptions (EDD). This paper demonstrates the basic concepts of FDT. Furthermore it is shown how the investment done in electronic device descriptions can be saved by applying device models and by re-using software components of existing commissioning tools.

Current issues on high-power cycloconverter - fed gearless motor drives for grinding mills

Abstract: Mining operations are facing the challenge of competitiveness because of low metal prices and operating costs. The only way to solve the problem is applying new design concepts in management, process operation, RD reliability and availability; operation within weak networks; power quality and harmonics control; process and knowledge-based instrumentation; mechanical and mechatronics aspects. Based on actual cases of application, the main constructive and operation aspects are described and the open problems for improving reliability and availability are discussed.

Wavelet analysis of partial discharges acoustic waves obtained using an optical fibre interferometric sensor for transformer applications

Abstract: The main problem in power transformers is the degradation of the isolation, and partial discharges are a major contribution to this shortcoming. Partial discharges inside medium and high power transformers generate ultrasonic pressure waves which are detected, in this work, with an optical fibre interferometric sensor. The Mach-Zehnder interferometric sensor implemented, for the detection of partial discharges inside power transformers, is described. This sensor allows a high level sensitivity to be achieved for the typical small pressure variations created by partial discharges. Wavelet analysis is used to identify the acoustic patterns instead of more commonly used Fourier analysis. Acoustic signals contain numerous non-stationary or transitory characteristics that Fourier analysis does not allow them to be obtained: when transforming to frequency domain, temporal information disappears. It is possible to state when a particular event took place. The wavelet analysis helps to solve this problem. Some of the results of which are presented here. These results are compared to those obtained with piezoelectric acoustic sensors, when looking for the best wavelet application, showing good agreement between both methods. We have obtained clear signal between 15-17 kHz and, for the first time, wavelet analysis has provided a tool to identify the shape of the acoustic waves associated to partial discharges.

Analysis of the grid side behavior of a LCL-filter based three-phase active rectifier

Abstract: Three-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue or if there are other loads connected to the same point of common coupling (PCC), and sensitive to the harmonics produced by the switching of the converter, an LCL-filter has to be used. This kind of solution has been studied in theory but its sensitivity to the values of the LCL-filter passive elements employed, to the grid side stiffness and to the parameters of the controller has never been detailed. In this paper the experimental results of an LCL-filter-based three-phase active rectifier are analyzed with the circuit theory approach. A "virtual circuit" is synthesized in role of the digital controller and of the feedback filters to have a homogenous model that allows a sensitivity analysis, which is rigorous and straightforward for the industry.

Adaptive sliding-mode observer for field oriented sensorless control of SPMSM

Abstract: This paper proposes a new scheme to guarantee speed sensorless control and optimal field orientation of surface permanent magnet synchronous motors (SPMSMs) even if parameter deviations occur and initial rotor position is unknown. A novel adaptive sliding-mode observer is used for field oriented speed sensorless control. First the induced e.m.f. components are observed using the sliding-mode technique with an adaptive switching gain. Then a low-pass filter with an adaptive amplitude compensator, that works as derivative observer, is used to get rid of the chattering noise of estimated e.m.f. components and to calculate rotor speed and position. The current components in rotor reference frame are estimated from the active and reactive electromagnetic torques calculated in both the stationary reference frame and the estimated rotor one. The latter is also used as control reference frame. Inverter, filters and observer cause unavoidable and unpredictable time-delay in rotor position estimation, so that the control reference frame is delayed as to the actual rotor one. As a consequence, field orientation and maximum torque/current ratio do not occur when the desired field oriented current references are imposed in the control reference frame. An original field orientation PI controller is used to provide the appropriate current references in the control reference frame. Test results are presented to prove the approach effectiveness.

Analysis of SRM drives behaviour under the occurrence of power converter faults

Abstract: This paper presents an analysis of the switched reluctance motor dynamic operation under power converter fault conditions. Open- and short-circuit faults in the converter power switches are considered. Normal operating results are also included, as a reference. Time-domain waveforms of the phase currents, electromagnetic torque, power converter supply current and mechanical speed are presented and discussed as well as the spectral analysis of the power converter supply current and electromagnetic torque. The paper also presents a switched reluctance motor model, used for the power converter fault analysis simulation studies.

A new model for tubular fluorescent lamps operated at high frequencies for dimmable applications

Abstract: This paper presents a new static model for tubular fluorescent lamps (T12 bulb) operated at high frequencies. The main goal of this paper is to investigate the effects of ambient temperature and nominal switching frequency of operation in the static characteristics of tubular fluorescent lamps. The methodology for obtaining the model is based on several two-dimensional mathematical regressions, used to provide the behavior of the fluorescent lamp according to different independent variables, namely: power processed through the lamp and ambient temperature. In addition, the proposed model can be easily converted to a lamp equivalent resistance model, which can be useful for ballast designers. Finally, the curves obtained using the new model are compared to the correspondent experimental data, in order to verify the accuracy of the proposed methodology.

Next generation integrated development of automation control code in TORERO

Abstract: Industrial control technology experiences a strong trend towards distributed systems. This leads to the distribution of formerly physically centralised hardware and software into smaller units, which are distributed within the automation system. From the software point of view, a major state-of-the-art technology for this is the international standard IEC 61499, for which however wide spread applications do not exist. In addition, Internet related technologies also have to be considered, to enhance the overall system performance. Related to these topics diverse proposals created by different organisations exist, which specify a future way of building industrial automation applications. All these approaches have the common modeling paradigm of programming distributed applications by connecting the function blocks in a "system editor". The function blocks for the single distributed units need to be programmed in a specific editor which is device specific. The overall system functionality thus can only be programmed as relationships of already existing function blocks. Within the IST initiative of the European Commission, the funded research project TORERO aims at specifying both an integrated development environment (IDE) and an architectural platform on specific devices which together allow for the distribution of (central) control functions.

Design and implementation of a low cost sine wave inverter

Abstract: This paper proposes a systematic procedure for designing a single-phase H-bridge inverter. It includes mathematical calculations, computer simulations and experimental verification on a scaled down prototype inverter.