A. Nogueiras

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.

Real-Time implementation of a SPLL for FACTS

This paper presents a real-time implementation of a software phase-locked loop (SPLL) for use within FACTS systems. The FACTS phase locked loops (PLLs) main characteristics and the disturbances impact over their performance are reviewed making special emphasis on the weak points of the usual three-phase trans-vector-type PLLs. These weak points are mainly slow response under low amplitude AC inputs and three-phase unbalances. Recently some alternatives, specially the adaptive SPLL, solved these typical trans-vector issues. However, the discrete implementation of adaptive SPLL in a programmable device like a microcontroller, a DSP or a FPGA seems very complex. In this work a double-loop SPLL has been developed with the aim of reducting the complexity of a discrete implementation and without losing performance with respect to the adaptive SPLL. The proposed double-loop SPLL has been implemented in real-time using Matlab/Simulink and the fast prototyping platform dSpace DS1103; its high performance and feasibility are shown in the simulation and real-time implementation sections

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

Fast lead-acid battery charge strategy

This paper discusses the fast charge strategy due to the fact that one of the limitations of the lead-acid batteries is the long charging time. The fast charge strategy uses two phases in order to reduce the charging time and obtain high performance without reducing the lifetime battery. In the first phase, constant high current is used and in the second phase current pulses controlled by a PID controller is used.

E-Learning Tool for dc Choppers

This work presents a software tool in order to facilitate the learning of the dc choppers. This tool consists of an integrated web-access set of multimedia animation-clips which present, in an interactive way, how the different dc choppers topologies work. The different topologies are classified depending on their quadrant operation and then the user can realize the circuits performance from the simplest class-A to the four quadrant operation class-E converter. To do this, all circuit parameters including load values, duty ratio, and frequency may be selected by the user. Moreover, the load includes an electromotive force (EMF) that allows understanding the energy flow between the source and the load and then, the quadrant operation. Other useful characteristic of the tool is the way in which the circuits are drawn because they can be shown as a bridge or in their simplest form in the case of only the essentials devices being shown. The information about the currents and voltages paths is dynamically presented with sliding rules over the graphs during simulations indicating the state of semiconductor switches by means of changing colours. The multimedia system includes documentation on all the subjects, showing basic concepts and equations, in pdf format and links to industrial manufacturers.

SPLL based control for active filter with reactive power compensation

This paper presents a single phase shunt active power filter with reactive power compensation. The employed control method combines the functionality of a feedforward active filter with the functionality of a shunt connected static compensator (STATCOM). Both to extract the load harmonic currents for active filtering and to measure the phase angles for reactive power compensation a novel software phase locked loop (SPLL) is employed. The SPLL architecture has two interconnected control loops, an amlitude controller and a phase angle controller, which provide a quick measure of amplitude, frequency and phase angle of the input signal, even for low amplitude signals. Moreover adaptive techniques employed in the SPLL make it quasi inmune to white noise and give it an excellent harmonics cancellation. The other features of the whole control as the current control loop, the dc-link capacitor controller and the reactive power compensation are widely explained too. Simulation and real time implementation results are presented to verify the performance of the model.

Multilevel multiphase space vector PWM algorithm applied to three-phase converters

Multilevel technology achieves high power ratings with voltage limited devices. Recently a new space vector pulse-width modulation algorithm for multilevel multiphase voltage source converters with low computational cost has been presented. This algorithm can be used with any number of phases; therefore, it can be also used with classical three-phase topologies. In this paper, the multiphase algorithm is particularized for three-phase converters and compared with an existing multilevel space vector modulation technique. Finally, the algorithm is implemented in a low cost FPGA and it is tested in laboratory with a real prototype by using a neutral point clamped inverter.