Alfonso Lago

Comparison of the FPGA Implementation of Two Multilevel Space Vector PWM Algorithms

Multilevel converters can meet the increasing demand of power ratings and power quality associated with reduced harmonic distortion and lower electromagnetic interference. When the number of levels increases, it is necessary to control more and more switches in parallel. Field programmable gate arrays (FPGAs), with their concurrent processing capability, are suitable for the implementation of multilevel modulation algorithms. Among them, space vector pulsewidth modulation algorithms offer great flexibility to optimize switching waveforms and are well suited for digital implementation. In this paper, two algorithms, 2-D and 3-D, are analyzed and implemented in an FPGA. In order to carry out the implementation, both algorithms have been described in very high speed integrated circuit hardware description language, partly hand coded, and partly automatically generated using the system generator tool. Both implementations are compared in terms of implementation complexity and logic resources required. Finally, test results with a neutral-point-clamped inverter are presented.

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.

Shunt active power filter with harmonic current control strategy

This paper presents a single phase shunt active power filter for compensating the power factor and harmonics currents generated by two nonlinear loads, an AC controller with resistive load, and a rectifier with an inductive load. The topology of the filter is based on a single phase inverter with four IGBTs. The filter current is forced to follow a reference; this reference current must be the difference between the sinusoidal input current in phase with the sinusoidal voltage supplying the load and the load current; for calculating the reference current a frequency-independent method has been used. The calculus of the reference current and results of simulation are presented; finally experimental results obtained from a prototype confirm the feasibility of the proposed system.

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

Geometric Analysis and Manufacturing Considerations for Optimizing the Characteristics of a Twisted Pair

The geometry of a twisted pair largely determines its electrical characteristics. To improve and refine the value of these characteristics according to preset values, the optimization of the manufacturing processes requires comprehensive knowledge of twisted pair geometry and of how electrical magnitudes are affected by the construction features of the twisted pair. This paper studies the relation between the length of a twisted pair cable and the length of each of the wires that compose the cable, by analyzing concepts such as pitch angle and radius of the helix. In addition, it examines the deformations and irregularities that can occur in the twisted pair during the manufacturing process and their effects on the geometry of the twisted pair. Results showed in this paper are a part of a larger research project carried out in association with the R&D department of a cable manufacturing company, and these results are being applied into the design department of this company.

Four-dimensional space vector PWM algorithm for multilevel four-leg converters

Four-leg voltage-source converters provide an effective neutral connection in three-phase systems with neutral wire. They can be applied to inverters, rectifiers or active filters to control the neutral current caused by unbalanced or nonlinear loads as well as unbalanced sources. From the modulation point of view, the four-leg converters can be considered as four-phase systems. Hence, the modulation task can be carried out with a generic multiphase modulation algorithm. Recently, a novel space vector PWM technique for multilevel multiphase voltage-source converters has been presented. The four-dimensional space vector PWM algorithm for multilevel four-leg converters presented in this paper is the result of applying such technique to a four-phase converter. Finally, the algorithm is implemented in a low-cost FPGA and it is tested with a prototype by using a five-level cascaded full-bridge inverter.

An approach to real behaviour modeling for traction lead-acid batteries

At the present time, the batteries are the main obstacle in the race toward the total development of the electric vehicles. In this article we present a PSPICE model for lead-acid batteries of traction that represents an approach of the real behavior of these so that it can be analyzed directly from the PSPICE environment. This model is flexible and can be adjusted in function of the type of electrochemical battery.

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.