Carlos Martinez-Penalver

Grid-synchronization methods for power converters

Grid synchronization is an important part in the control of grid-connected power electronic converters. The fundamental phase-angle at the point of common coupling should be tracked on-line in order to control energy transfers. Digital implementation allows to implement high performance algorithms, which are robust in the presence of power quality phenomena. However, different kinds of distortion cause a reduction of the effective bandwidth, and hence, affects to the transient response of the equipment. This paper reviews some of the highest performance algorithms for grid synchronization: phase locked loops (PLL), schemes based on synchronous reference frames (SRF) and digital filtering and finally, stochastic filtering based methods. The pros and cons of each one are assessed and some interesting techniques to enhance the dynamics are provided. The assessment in the presence of frequency deviations is analyzed in detail. The most significant techniques to provide a better frequency adaptation are enumerated and analyzed in the last section of this paper.

A Multi-Point Sensor Based on Optical Fiber for the Measurement of Electrolyte Density in Lead-Acid Batteries

This article describes a multi-point optical fiber-based sensor for the measurement of electrolyte density in lead-acid batteries. It is known that the battery charging process creates stratification, due to the different densities of sulphuric acid and water. In order to study this process, density measurements should be obtained at different depths. The sensor we describe in this paper, unlike traditional sensors, consists of several measurement points, allowing density measurements at different depths inside the battery. The obtained set of measurements helps in determining the charge (SoC) and state of health (SoH) of the battery.

E-learning system for power electronics converters

A multimedia and interactive system to help teaching power conversion techniques for AC/DC, DC/AC and AC/AC is described as a tool for both teachers and students. The tool include many different suitable topologies for the aforementioned power systems. In each different topology, the user can select among types of loads: resistive, inductive, capacitive and combinations. Firing angles and modulation schemes can also be selected to show different behavior of the topologies. Some values are selected by introducing the desired value, and remain fixed during simulations while other values can be dynamically adjusted with sliding rules during simulations. During the simulation the circulating current direction and the state of semiconductor switches is shown, by means of changing colors. The multimedia system includes documentation on all the subjects, showing basic concepts and equations, in pdf format and links to industrial manufacturers. One of the main contributions is that all the system is in Spanish language, becoming useful for classroom and laboratories duties without the need of translation. Once finished with the simulations, the students can auto evaluate themselves with an automated test set. This feature helps the students to establish the knowledge level acquired after employing the multimedia tool.

FPGA implementation of a fuzzy controller for automobile DC-DC converters

The design of synchronous multiphase DC-DC converters for automobile applications is now a very active field, because the automotive industry forecast that future power demands inside a car will oscillate between 2.5 kW and 3.5kW, keeping a dual system of 42/14V batteries. The design of controllers for the optimal behavior of such converters is a very delicate task. In this paper, an optimized fuzzy control algorithm has been developed to control a synchronous multiphase converter of 1.6kW. First, the fuzzy control algorithm is designed and verified, together with a non linear model of the converter power stage, by means of Matlab and Simulink. Then, the fuzzy controller hardware is developed through Xilinx System Generator for Simulink, and implemented in a Spartan 3 FPGA to achieve a real-time controller

A course on dc-to-dc converters towards the ECTS using the b-learning methodology

A b-learning methodology is applied to a dc-to-dc converters course. The environment is set up by means of joining in an e-learning Moodle platform lectures and emulation sessions, and an improved interface for an remote laboratory setup. Lectures are reduced to a set of few hours, favoring self study and tutoring sessions. Asynchronous access to theoretical lectures, emulators and remote laboratory increase the degrees of freedom between professors and students. A redesign of the interface of the server let professors and students interact with the experiments and the equipment in the remote laboratory by means of a queue / batch. The results of execution are measurements from programmable instrumentation, saved to be recover later as a report. Experience acquired with similar power electronic on previous courses has lead authors to create a test course of one semester duration on dc-to-dc converters^ with great success.

New algorithm for grid synchronization based on Fourier series

This paper presents a new digital open loop architecture as an alternative to Phase locked loops (PLLs) for grid synchronization. The system calculates in real time the Fourier coefficients of the input signal fundamental component using a heterodyning algorithm. Once the fundamental components are calculated the system can reconstruct the input fundamental signal and calculate its phase angle, frequency and amplitude. The measuring process of the Fourier components require to hlter even harmonic components internally generated; this process is made with a moving average comb filter (MVA) tuned for these even harmonics. The performance of the system is demonstrated with experimental results.

A new complete non-linear simulation model of a buck DC-DC converter

A complete model of a switch-mode buck DC-DC converter was developed in order to fully describe the three most important characteristics of the system: small-signal model, transient simulation and start-up. Due to the inherent nonlinear nature of the switch-mode converter, the new model created with MATLAB and SIMULINK is nonlinear. The model recreates the behaviour of the PWM modulator and the switch (the transistor plus the diode) in the converter in a switched nonlinear way. Using only one model, with the values of the output filter components and some functional data from the control block, it is possible to obtain transient simulations for load changes, a start-up transient simulation and Bode plots for three different transfer functions: input-to-output, control-to-output and reference-to-output. As an example, this last transfer function is shown.

Design, Analysis and Modeling of an Optimized Fuzzy Control Algorithm for Synchronous Multiphase DC-DC Converters in Automotive Applications

The design of synchronous multiphase DC-DC converters allows improvements of the characteristics of high power systems. The automotive industry forecast that future power demands inside a car will oscillate between 2.5 kW and 3.5kW, keeping a dual system of 42/14V batteries. In this paper, an optimized fuzzy control algorithm has been developed to control a synchronous multiphase converter of 1.6kW for dual voltage architecture in future vehicle applications. The proposed optimized fuzzy control algorithm is analyzed and simulated together with a non lineal model of the power stage, by means of Matlab and Simulink. This simulation platform also integrates tools for a future implementation of the controller embedded in a FPGA. The main contribution of this work is the implementation of an optimized fuzzy algorithm of control that can be used independently of the number of phases of the converter, making it suitable to be applied in a wide range of high power applications. This algorithm has been designed having in mind the goal of developing a real-time FPGA-based controller, so the complexity has been reduced to a minimum. Hybrid vehicles, aerospace and naval industry power systems can also benefit from the development of this algorithm.

Density measurement into lead-acid batteries with multipoint optical fiber sensor

There are numerous applications for the use of leadacid batteries: automotive applications, telecommunications, UPS, remote-area power-supply systems, etc. Modern energy-storage applications require higher reliability than has been demanded in the past; in addition, systems have been developed for monitoring and managing the batteries so as to achieve duty in service. For determination of battery state, it is necessary to know the state of charge (SOC) and the state of health (SOH), one of the physical parameters with information about the SOC is the electrolyte density. An electrolyte density sensor must be able to measure the electrolyte density at different places because the battery-density varies with location. This paper presents a plastic optical fiber sensor developed for measuring in real time the electrolyte density into lead-acid batteries. The sensor measures the density at four different heights. The environment in the batteries that use an electrolyte with Sulfuric Acid (H2SO4) at an elevated temperature during the use process is very hard and the accuracy of the density readout must be maintained through the useful life of the vehicle. We have done an accelerated test to check the reliability sensor. The test duration was over one calendar year (9,552 hours) using a sensor with four optical fibers. For the test, the electrolyte acid density was set to 35%, and the temperature to 70 degrees Celsius. An electronic system for emission and detection of light collected data periodically to assess the transmission loss in the fibers as they aged. In this paper we present the test results.

Methodology to Obtain the Voltage-Dependent Parameters of a Fourth-Order Supercapacitor Model With the Transient Response to Current Pulses

In order to design power circuits including supercapacitors, a model that responds as closely as possible to results in actual tests, in both fast and slow transients, is required. The network of the parallel RC branches model is widely used to justify the electrical behavior of supercapacitors. In that model, in order to achieve a good fitting between simulation and actual transient responses, the interdependence among the parameters, as well as their voltage dependence, must be considered. This study presents a method to deduce the parameters of the RC network model through the transient response of the supercapacitor including theirs voltage dependence. The methodology considers that the electrical charge provided to the device in the current pulses is not only injected in the fastest branch, but also is simultaneously distributed toward the slower branches. A set of tests have been carried out through the whole voltage range of the device in such a way that in each one the parameters can be considered constant. Then, with the obtained series of values for each parameter, their voltage dependence has been deduced through linear regression. Practical results of a fourth-order model with voltage-dependent parameters are presented and compared with simulations.