Instituto de Engenharia de Sistemas e Computadores, Investigação e Desenvolvimento em Lisboa

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Publications

IOb-Cache: a high-performance configurable open-source cache

Publication . Roque, João, V.; Lopes, João D.; Véstias, Mário; De Sousa, Jose

sorts of open-source implementations of peripherals and other system-on-chip modules. Despite the recent advent of open-source hardware, the available open-source caches have low configurability, limited lack of support for single-cycle pipelined memory accesses, and use non-standard hardware interfaces. In this paper, the IObundle cache (IOb-Cache), a high-performance configurable open-source cache is proposed, developed and deployed. The cache has front-end and back-end modules for fast integration with processors and memory controllers. The front-end module supports the native interface, and the back-end module supports the native interface and the standard Advanced eXtensible Interface (AXI). The cache is highly configurable in structure and access policies. The back-end can be configured to read bursts of multiple words per transfer to take advantage of the available memory bandwidth. To the best of our knowledge, IOb-Cache is currently the only configurable cache that supports pipelined Central Processing Unit (CPU) interfaces and AXI memory bus interface. Additionally, it has a write-through buffer and an independent controller for fast, most of the time 1-cycle writing together with 1-cycle reading, while previous works only support 1-cycle reading. This allows the best clocks-per-Instruction (CPI) to be close to one (1.055). IOb-Cache is integrated into IOb System-on-Chip (IOb-SoC) Github repository, which has 29 stars and is already being used in 50 projects (forks).

2021-07-21Journal article

Open access

Electric vehicle integrated battery charger for an AC drive with open windings

Publication . Fernão Pires, V.; Cordeiro, Armando; Foito, Daniel; Silva, J. F.

Merging of electric vehicle (EV) charging converter within the EV motor drive allows to minimize the charging system regarding volume, weight, and cost. Thus, several integrated battery charger topologies have been presented for well known drives. However, very few works have been addressed for open windings motor drives. This work is focused on open windings motor drives and battery charger types, proposing a new integrated charger topology. The proposed solution avoids the extra three-phase power factor corrector (PFC) and provides bidirectional power flow, allowing the vehicle batteries to operate also as a grid storage system. Some terminals of the motor open windings are connected to a three-phase inverter supplied by the batteries while the remaining terminals are connected to a three-phase inverter with a floating capacitor. The proposed EV battery charger will be verified and tested by several simulation results.

2021-08-10Conference object

Restricted access

Distributed and decentralized orchestration of containers on edge clouds

Publication . Pires, André; Simão, José; Veiga, Luís

Cloud Computing has been successful in providing substantial amounts of resources to deploy scalable and highly available applications. However, there is a growing necessity of lower latency services and cheap bandwidth access to accommodate the expansion of IoT and other applications that reside at the internet's edge. The development of community networks and volunteer computing, together with the today's low cost of compute and storage devices, is making the internet's edge filled with a large amount of still underutilized resources. Due to this, new computing paradigms like Edge Computing and Fog Computing are emerging. This work presents Caravela a Docker's container orchestrator that utilizes volunteer edge resources from users to build an Edge Cloud where it is possible to deploy applications using standard Docker containers. Current cloud solutions are mostly tied to a centralized cluster environment deployment. Caravela employs a completely decentralized architecture, resource discovery and scheduling algorithms to cope with (1) the large amount of volunteer devices, volatile environment, (2) wide area networks that connects the devices and (3) nonexistent natural central administration.

2021-09Journal article

Restricted access

A DC-DC converter for bipolar DC microgrids with voltage balance capability to supply a multilevel SRM drive

Publication . Fernão Pires, V.; Foito, Daniel; Pires, A. J.; Cordeiro, Armando; Martins, J. F.

In this work it is proposed a DC-DC converter to supply a multilevel Switched Reluctance Machine (SRM) drive. The proposed converter was designed to be integrated in a bipolar DC microgrid. Usually, this kind of microgrid requires a support to avoid unbalances between the poles. Thus, the proposed converter also integrates voltage balance capabilities allowing the required support to the bipolar DC microgrid. Besides that, the converter can also supply the drive using only one of the poles. The behavior and operating modes of the converter will be described in detail. Several simulation tests will also be provided. From these tests, the behavior and the several operation modes of the DC-DC as well as the multilevel SRM drive supplied by this converter will also be presented and analyzed.

2021-08-10Conference object

Restricted access

Control of PV distributed systems based on three-phase triple inverters to support grids with unbalanced loads

Publication . Fernão Pires, V.; Foito, Daniel; Cordeiro, Armando; Silva, J. Fernando

This paper is focused on the control system for photovoltaic (PV) generators using three-phase triple inverters. These inverters allow for a distributed PV system, and at the same time, they provide AC multilevel operation. The proposed controller is designed to allow the operation of the inverter in a way that it can extend support to the grid with ancillary services. One of the ancillary services that the three-phase triple inverter can support is the injection of unbalanced currents in order to eliminate or attenuate grid load unbalances. Therefore, the proposed topology will be extended to accommodate four wires. The capability of the system to support the grid with ancillary services, especially the compensation of unbalanced loads, the four-wire multilevel topology operation and the proposed controller will be verified through several simulation tests.

2021-09-15Conference object

Restricted access