Showing papers by "V. Fernao Pires published in 2021"
TL;DR: In this paper, the authors proposed a new topology for a DC-DC converter with bipolar output and high voltage gain, which was designed with the aim to use only one active power switch.
Abstract: This paper introduces a new topology for a DC-DC converter with bipolar output and high voltage gain. The topology was designed with the aim to use only one active power switch. Besides the bipolar multiport output and high voltage gain this converter has another important feature, namely, it has a continuous input current. Due to the self-balancing bipolar outputs, the proposed topology is suitable for bipolar DC microgrids. Indeed, the topology balancing capability can achieve the two symmetrical voltage poles of bipolar DC microgrids. Furthermore, it is possible to create a midpoint in the output of the converter that can be directly connected to the ground of the DC power supply, avoiding common-mode leakage currents in critical applications such as transformerless grid-connect PV systems. The operating principle of the proposed topology will be supported by mathematical analysis. To validate and verify the characteristics of the presented topology, several experimental results are shown.
20 citations
TL;DR: Results show that the inclusion of storage devices near the prosumers’ PV systems is the recommended solution to enhance voltage stability and balance, and a significant reduction of active power losses in the LV network is observed.
Abstract: The ongoing increase of PhotoVoltaic (PV) microgeneration, pointing to high levels of penetration, can lead to the occurrence of overvoltages. Moreover, the inherent unbalanced nature of the LV distribution grid is a difficulty that must be considered when designing countermeasures. On the other hand, storage systems are suitable devices that can help the process of voltage control. This paper proposes a control system for a real-time energy management system, using Multi-Objective Particle Swarm Optimization (MOPSO) on a highly unbalanced LV distribution network, with batteries and a high share of PV. The purpose of the control system is the optimization of four objectives: Voltage Unbalance Factor (VUF), voltage deviation, active power losses and PV curtailment, wherein four scenarios were considered for assessment. This study is conducted using an unbalanced three-phase power flow algorithm. A comparison of residential and community storage is performed. The results show that the inclusion of storage devices near the prosumers’ PV systems is the recommended solution to enhance voltage stability and balance. Moreover, a significant reduction of active power losses in the LV network is observed.
13 citations
14 Jul 2021
TL;DR: In this paper, a DC-DC converter was proposed to supply a multilevel SRM drive in a bipolar DC microgrid, which was designed to avoid unbalances between the poles.
Abstract: 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.
6 citations
20 Jun 2021
TL;DR: In this paper, a DC-DC-AC micro-inverter topology for a photovoltaic kit able to address the previous scenario is proposed, which is capable of working in both isolated and parallel modes, with other kits.
Abstract: Taking into account the geographic location of some rural areas, it is not viable, due to technical or economical reasons, to connect certain villages to the electrical grid. Since access to energy is essential for human development, a DC-DC-AC micro-inverter topology for a photovoltaic kit able to address the previous scenario is proposed in this paper. This kit is capable of working in both isolated and parallel modes, with other kits. This solution is also adequate for a post-natural catastrophe scenario, given the power outages associated with these types of phenomena. Each kit consists of a photovoltaic module, an energy storage system and a DC-DC-AC micro-inverter. A control system for all the subsystems is also presented in this paper. Besides that, the management of the DC bus, taking into consideration the photovoltaic system and energy storage system is also proposed. All the theoretical analysis of this kit is detailed in the paper and confirmed through simulations.
4 citations
29 Jun 2021
TL;DR: In this paper, a DC-DC converter that allows to interlink these two DC microgrids is proposed, which is a non-isolated bidirectional DC-dc converter with bipolar and unipolar interfaces.
Abstract: DC microgrids are starting to become quite important in the actual context of electrical energy distribution grids. There are two main structures for these grids, the unipolar and the bipolar DC microgrids. In this paper, a DC-DC converter that allows to interlink these two DC microgrids is proposed. This converter is a non-isolated bidirectional DC-DC converter with bipolar and unipolar interfaces. The converter was designed to transfer energy between these microgrids and, at the same time, to support the balance of the bipolar DC microgrid. Moreover, the proposed converter is also able to operate as a standalone voltage balancer to support the bipolar DC microgrid. The converter also presents bidirectional buck-boost characteristics. Simulations and experimental results of the DC-DC converter operating in both directions will be provided. From the presented results, it will be possible to verify the capability of the converter to operate as interlink interface for both microgrids.
1 citations
27 Jan 2021
TL;DR: In this article, a new multilevel converter for the switched reluctance machine (SRM) with fault-tolerant capability is presented, which allows to maintain the drive at operation for both conditions of open circuit and short-circuit power semiconductor fault.
Abstract: Many critical systems require permanent operation even in a situation of a fault. In this way, electrical drives that are associated to these systems must have fault-tolerant capability. One of the machines that are used in many systems is the switched reluctance machine (SRM). To achieve the best performance with a wide speed range, multilevel converters are one of the adopted options. Thus, this paper presents a new multilevel converter for the SRM with fault-tolerant capability. The proposed solution allows to maintain the drive at operation for both conditions of open-circuit and short-circuit power semiconductor fault. Their operation in normal and fault-tolerant modes for the 8/ SRM is presented in detail. To verify the capability and operation modes of the proposed system several simulation tests will be presented.
1 citations
14 Jul 2021
TL;DR: In this paper, a hybrid powertrain comprised of a parallel configuration of aluminium-air fuel cells and ultracapacitors is proposed and evaluated, with a particular focus on efficiency and reliability, leading to the adoption of interleaved DC/DC converter topologies.
Abstract: Based on the metal-air fuel cell technology continuous improvements, a hybrid powertrain comprised of a parallel configuration of aluminium-air fuel cells and ultracapacitors is proposed and evaluated. Owing to the powertrain's expected advantages and limitations, suitable switching converters are proposed, with a particular focus on efficiency and reliability, leading to the adoption of interleaved DC/DC converter topologies, using wide-bandgap semiconductors. Further contribution is the developed strategy for the system's modulators and controllers, enabling fault-tolerant operation, while accounting for the different response times of the energy storage systems, allowing stable operation, with low voltage and current ripple and minimal total harmonic distortion.
06 Jul 2021
TL;DR: In this article, the authors focused on the control system for photovoltaic (PV) generators using three-phase triple inverters and designed a controller to allow the operation of the inverter in a way that it can extend support to the grid with ancillary services.
Abstract: 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.
14 Jul 2021
TL;DR: In this paper, the authors proposed a new integrated charger topology for open windings motor drive and battery charger, which 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.
Abstract: 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.
26 Sep 2021
TL;DR: In this article, a vector voltage modulator is proposed for the dual inverter multilevel converter in fault tolerant mode under an inverter open switch, and the capability of this modulator to function properly under an open switch is analyzed.
Abstract: The dual inverter multilevel converter is characterized by a elementary structure using two well-known three-phase bridge inverters supplied by two independent DC sources. However, it can be supplied only by a single DC source if one of the bridges uses just a floating DC capacitor. In this case the control is more complex since it is also required to ensure the capacitor voltage regulation. Besides this, if a fault in one of the switches is also considered, the operation of the converter in fault operation mode becomes even more complex. This paper presents a vector voltage modulator that in addition to track the reference of the output AC voltages, also allows the capacitor voltage regulation of the floating bridge. The capability of this modulator to function properly the converter in fault tolerant mode under an inverter open switch will also be analyzed. This analysis will allow to verify that the proposed control and modulation strategy presents inherent fault tolerant capability to open switch fault, since it does not require any fault detection algorithm or change in the control or modulation strategy. The capability and operation of the proposed vector voltage modulator will be verified through several simulation studies