Marcelo Reyes

The use of renewable energy sources (RESs) together with energy storage systems (ESSs) allows for smoothing power variations, thus improving power backup capabilities and power quality in the electric power grid. These applications require power converters to transfer energy between the renewable generator or energy storage and the power grid. In any case, the control algorithm of the power converter requires the synchronization method to provide a correct estimation of the instantaneous voltage of the power grid. This work provides engineers and researchers with an accessible platform at a low cost (less than USD 100) and a methodology for the experimental validation of digital synchronization algorithms as a step before their implementation in grid-connected equipment. The methodology evaluates the performance of the digital algorithms when there are variations in amplitude, frequency, phase, and harmonic content in the emulated three-phase power grid, as well as the execution times (t_ex), while a digital platform emulates the electrical signals and generates reference signals for the evaluation. To illustrate this proposal, two synchronization algorithms—SRF-PLL and DSOGI-PLL with a low-pass filter—are implemented in a digital controller and tested. The evaluation tool confirms the algorithms’ performance and shows that the execution time of DSOGI-PLL is 91% longer than that of SRF-PLL, which is well known in the literature.

This work deals with the advances in implementing and using the Controller Area Network (CAN) to communicate power converters distributed in a Microgrid in Universidad del Bío-Bío, Chile. The objective is to allow the future implementation of a Secondary Control and Tertiary Control of the Microgrid, expanding the capability of the Laboratorio de Acondicionamiento y Conversión de Energía of Universidad del Bío-Bío (LACE-UBB) to test microgrid control strategies. The manuscript reviews the Microgrid implemented in Universidad del Bío-Bío, the implementation of the CAN bus among the different devices in the microgrid, focusing on the digital control platform used in the power converters, and a preliminary test to set the power converter references using the CAN bus.

In the present work, the performance of the Arduino Due and Delfino LaunchPad TMS320F28379D development boards are evaluated and compared,to be a guide for developers who must decide to migrate their application,or who must decide between both technologies at the beginning of their project. When considering the compatibility of their electrical levels for the connection of peripherals and differences in computing capacity. In particular, the execution time of mathematical operations and instructions of common use in the acquisition and processing of signals is evaluated usingavailable functions in C language. The work considers (i) the evaluation of the characteristics of hardware and development environments, (ii) the methodology for the evaluation of execution times, algorithms, and configuration considerations, (iii) case study and results, and (iv) performance comparison. The results show that basic mathematical operations with floating-point are executed 16 times faster when migrating from Arduino Due to Delfino LaunchPad.

AC-DC power conversion is an essential process in the industrial area at medium/high voltage levels for AC motor drives, conveyor belt systems, rolling mills, or others. The multilevel converters allow us to work at the voltage levels mentioned and give us a low harmonic content in the AC side of the system. However, these power conversion systems consist in their topology of an input transformer, which is sensitive to low order harmonic currents, generating saturation and increased losses. This work proposes a modulation scheme called Feedback Quantizer, applied to multi-cell active front-end rectifiers, aiming to obtain a focused mitigation of low-frequency current harmonics of the power cell. Furthermore, to ensure the stability of the DC voltage of each power cell, a control strategy consisting of nonlinear control, a first-order filter to the DC voltage reference, and a PI control will ensure stability and zero steady-state error at step input. The simulated results show the correct operation of the proposed scheme.

In this work, a comparative analysis of the performance and efficiency of the FCS-MPC and Modulation FBQ applied to an AFE active front rectifier is carried out. The above compares quality indicators of form in the input current of an AFE, THD, and WTHD rectifier. For efficiency, the conduction and commutation losses in the switches will be estimated to obtain a selection criterion between these two control methods, which will be based on the efficiency of the converter and the performance of the input current loop. The semiconductors losses are calculated by linear mathematical approximations, which depend on the operation point of the AFE rectifier and the switch parameters, which are obtained from the datasheet provided by the switch manufacturer, which for this work, IGBT IKW25T120 was selected. Finally, for the performance analysis, satisfactory simulation results were obtained.

Multi-cell converters are widely used in medium-voltage AC drives. This equipment is based on power cells that operate with low-voltage-rating semiconductors and require an input multipulse transformer. This transformer cancels the low-frequency current harmonics generated by the three-phase diode-based rectifier. Unfortunately, this transformer is bulky, heavy, expensive, and does not extend the existing power cell (three-phase rectifier—Direct Current (DC) voltage-link—single-phase inverter) to the transformer. In this study, a harmonic cancelation method based on finite control set-model predictive control (FCS–MPC), extending the power cell’s modularity to the input transformer. On the other hand, it considers treating the two disadvantages of the FCS–MPC: High switching frequency and spread spectrum. The details were developed in theory and practice to obtain satisfactory experimental results.

A control scheme based on finite control set ---model predictive (FCS-MPC) improved with a Feedback Quantizer is presented. The FCS-MPC is a control scheme popularly used in power converters because, among others, (i) the nonlinearities and constraints of the converter’s operation, are quickly considering, (ii) it uses the natural discrete operation of power converters, and (iii) the rapid response to changes in both references or disturbances. However, the variable switching frequency operation in model-based predictive control results in a spread harmonic spectrum, generating resonances or saturation in input transformers when used in active front-end (AFE) rectifiers. This paper proposes an improved FCS-MPC, using a feedback Quantizer applied in a multi-cell AFE rectifier. This above consists of a feedback modulation technique, which allows minimizing the low-frequency harmonics in the converter PWM voltage. Simulation results verify the performance of the proposal obtaining improved harmonic spectrum of both input current and PWM voltage waveforms of the converter.

Multilevel converters are widely used in medium voltage applications. One of the most popular topologies in this field is the 18 pulses diode rectifier, which uses a muItipuIse transformer that realizes a current harmonics cancelation that are generated by the three phase diode rectifiers. In this work an efficiency comparison of the aforementioned topology and a Multi-Cell Active-Front-End (AFE) Rectifier operating with Finite Control Set - Model Predictive Control is performed. This efficiency comparison is focused on the rectifier losses divided into two types. The first one is the semiconductors switching and conduction losses. The second one evaluates the transformer losses, which are studied under two criteria: copper losses (Standard IEEE C57.10-1998) and the K - Factor (Standard IEEE / ANSI C57.110). The results show that the diode based rectifier topology has lower semiconductors losses, while the topology based on AFE rectifiers has lower transformers losses and a less complex design. Indeed, a reduction of a 7.2% in copper losses is achieved in the transformer secondary with respect to a multi-pulse transformer secondary.

In the last decades, finite control set-model predictive control (FCS-MPC) has been extensively investigated. This control strategy uses the system model to determine the optimal input that minimizes a predefined cost function. This procedure is performed by evaluating the admissible inputs of the converter model. In order to achieve a proper performance of the control strategy, a small sampling time must be used. In practice, the computational effort and processing time are critical factors that depend directly on the number of admissible states of the topology. With the objective of reducing the execution time needed by the algorithm, it is possible to take advantage of the high degree of parallelism that can be obtained from a field-programmable gate array (FPGA). This paper deals with the implementation of FCS-MPC in an FPGA XC3S3500E to control a power cell of a cascaded half bridge (CHB) converter. The design is divided into subparts, called modules, which can be projected to control multiple cells using only one chip. In addition, with the aim to restrict the use of hardware to the available resources, the document presents a series of considerations related to the algorithm and its implementation. This paper presents a detailed guide with emphasis on the design and outlining of each module in order to reduce the developing times for researchers in the area of power converters.