A PC-based low cost impedance and gain-phase analyzer
Abstract In this paper, we present a practical and inexpensive impedance/gain-phase analyzer (IGPA), which is very useful in the design of electronic circuits. This instrument allows the Bode diagram of any network or electronic circuit with an input and an output to be obtained, even though this implementation was not previously known. It can also obtain the module and phase diagrams of any impedance separately. The device under test (DUT) is connected to a personal computer (PC) via the parallel port by means of an electronic circuit implemented for this purpose. The results are shown on the screen of the PC and can be accessible for use in any further operation. The instrument operates i…
Development details and performance assessment of a Wind Turbine Emulator
This paper describes an experimental platform to emulate the static and dynamic behavior of real Wind Energy Conversion Systems (WECS). The Wind Turbine Emulator (WTE) consists of two coupled 1.5 kW squirrel-cage induction machines. The WTE calculations are performed on a PC and a DSP, both connected via USB. The total torque applied to the WTE motor is the difference of the scaled wind mechanical torque calculated on the PC, and the turbine inertia torque calculated on the DSP. An improved WTE shaft speed derivative has been used for the inertia torque calculation, which provides better results in terms of attenuation of the high-frequency harmonics present in the generator speed acquisiti…
Design of a virtual instrument for water quality monitoring across the Internet
Abstract This article presents the design of a new distributed and multi-platform system for water quality monitoring, enhanced with powerful Internet capabilities. The measured variables are temperature, turbidity, pH, dissolved oxygen, and electrical conductivity. The signal-conditioning block has been simplified through the use of software routines for thermal compensation, hence, reducing the cost and dimensions. The system offers a wide variety of Internet capabilities, like e-mail alarm notifications, automatic storage of measured data in a remote machine via the FTP protocol, dynamic generation of HTML reports, real time graphs, and indicators visible from a remote web browser, etc. …
Control circuit design of the L-LC resonant inverter for induction heating
In this article, the frequency variation control strategy for an induction heating L-LC resonant inverter is analyzed. The control consists of three loops, which are analyzed and reduced to their corresponding small-signal block diagrams. From these diagrams, the optimal structure of the compensation network and the design boundaries for first order closed-loop response are derived. The special case of phase limitation is analyzed because it is unstable in open-loop operation. Finally the implementation of the control circuit is described and experimental results are shown.
Parameterizing non-linear magnetic cores for PSpice Simulation
Abstract. In this paper the main Jiles & Atherton parameters of a magnetic material, according to their particular working condition (mainly frequency, temperature and waveform) are calculated by means of a systematic procedure that use PSpice and MathCad. The modelled magnetic material is used for power electronics circuit simulation, which uses magnetic materials, working at frequencies in the region of kH, to construct transformers and inductors. Magnetic materials are the most critical components in electronics simulators due to their nonlinear behaviour and the accuracy in the simulation can only be obtained through a proper magnetic material modelling. This paper examines the modellin…
A novel four-quadrant power supply for low-energy correction magnets
Abstract This paper describes an efficient power supply to feed low-energy correction magnets in particle accelerator applications, where a controlled current with trapezoidal profile and four-quadrant operation is needed. The selected design is based on an AC–DC matrix converter topology, which uses the Space Vector Modulation (SVM) technique to obtain a near unity power factor at the AC input and output DC current regulation. This topology allows performing high-frequency isolation, while four-quadrant operation is maintained, and reducing volume and weight as compared with the classical thyristor (SCR)-based technology. Control tasks are implemented on an all-digital control card: output…
A New Generalized Robust Predictive Current Control for Grid-Connected Inverters Compensates Anti-Aliasing Filters Delay
In this paper, a new predictive control for grid-connected inverters is presented, which provides the best performance in terms of transient response and stability margins when analog filters in current sensing circuits are used. These filters are necessary to avoid aliasing in the A/D conversion process, which causes an important ripple on injected current into the grid and increases the total harmonic distortion. However, predictive controls are very sensitive to delays on the acquisitions, so when such anti-aliasing filters are used a reduction of stability margins is produced and the transient response is affected. The proposed predictive control allows to compensate the effect of the f…
Wind Turbine Generation System With Optimized DC-Link Design and Control
This paper presents an optimized capacitance design for the dc link of a back-to-back converter for wind turbine power generation. The design method combines switching ripple and dynamic specifications to give the smallest possible dc-link capacitance and the required proportional-integral compensator for the voltage regulation. Furthermore, a novel concept to globally manage the on/off switching of back-to-back power subconverters, based on a finite-state machine, is presented. The proposed management system keeps control of the dc-link voltage for proper operation of both subconverters regardless of wind or grid conditions.
Guidelines for the design and implementation of the ARPCC control applied to grid-connected converters
Abstract This paper presents implementation details of the adaptive robust predictive current control (ARPCC) applied to a grid-connected converter, such as feed-forward cancellation protocol, the selection of the observer gain and adaptive parameters or the sampling options, needed to get the best performance of this control. The feed-forward term cancellation permits to achieve a very low harmonic distortion in current waveforms when the voltage sensing circuits are well calibrated. A detailed gain adjustment protocol of the voltage sensing circuits is presented in this paper. Moreover, a control design procedure based on the observer gain L o boundaries and the adaptive parameters has be…
DSP Implementation for Measuring the Loop Gain Frequency Response of Digitally Controlled Power Converters
This paper presents a method for measuring the loop gain frequency response of digitally controlled power converters, without the need of any expensive measurement equipment such as frequency response analyzers (FRA). The method is based on the traditional perturbation and measurement scheme. The perturbation is internally synthesized by the DSP and applied as pulse-width modulation to the converter. The loop input and output data are sent to a PC via universal serial bus, which performs online the DFT of sent data. The perturbation amplitude is varied with frequency to improve signal-to-noise ratio of measurements. The number of cycles used to perform discrete Fourier transform calculation…
Obtaining the electrical model of a power transformer by means of finite element software
Abstract. The behaviour of transformers and inductors working at high-frequencies and high power density can dramatically differ from the ideal or low-frequency operation. Their performance is very dependent on the magnetic material, operating frequency and physical construction. In this paper, finite element analysis (FEA) is used to obtain an accurate characterization of the electromagnetic behaviour of these magnetic components.
An Adaptive Robust Predictive Current Control for Three-Phase Grid-Connected Inverters
This paper presents an adaptive robust predictive current control (RPCC) for grid-connected three-phase inverters that exhibit zero steady-state current error. The error correction is achieved by means of an adaptive strategy that works in parallel with the deadbeat algorithm, therefore preserving the typical fast response of the predictive law. The resulting control adapts to any particular L or LCL filter by estimation of the resistive part of the filter. As a variety of the RPCC class of control, it offers the best tradeoff between robustness and speed. © 2009 IEEE.
Series and parallel resonant inverters for induction heating under short-circuit conditions considering parasitic components
Series and parallel resonant inverters are the common structures in high power industrial generators for induction heating applications. In practical working conditions, short-circuit of the heating coil is very common, normally producing overvoltages that can damage the power transistors of the inverter if no special precautions are taken. The aim of the paper is to show the mechanism of how overvoltages are generated under short-circuit conditions of the heating coil for series and parallel inverters.
Design considerations for transformerless series resonant inverters for induction heating
The aim of the paper is to present some preliminary ideas in order to overcome the output transformer in series resonant inverters for induction heating applications. By adding a third reactive element to the conventional two element resonant inverter, the output matching transformer can be eliminated, allowing accommodation of the resonant frequency and load with the only drawback being the need for an overdimensioning of the output capacitor bank, and benefiting from inherent short-circuit protection.