Voltage Transients Mitigation in the DC Distribution Network of More/All Electric Aircrafts

The objective of this paper is to present a power conversion system, based on a bidirectional DC/DC converter, along with a supercapacitor bank, that mitigates the voltage transients that occur on the DC distribution network of More/All Electric Aircrafts. These transients, such as voltage sags and swells appear on the DC buses of on-board microgrids, mainly due to load variations and are classified according to the aircrafts electric power system standards. First, we shortly describe an aircraft distribution network, that is applicable to the most common actual aircraft architectures, then we present the proposed system, along with the bidirectional DC/DC converter design, the control technique and the supercapacitor bank sizing. Finally, we present simulation and experimental results that support the effectiveness of the proposed system to effectively compensate voltage transients, supporting the DC buses in dynamic conditions. Concluding, the proposed system provides high power quality and compliance with the respective power quality standards for aircraft microgrids

On the Injection of Sub/Inter-Harmonic Current Components for Active Anti-Islanding Purposes

Active anti-islanding schemes that are based on the injection of harmonic currents, such as the measurement of the impedance at a specific frequency or similar techniques, have been proposed for anti-islanding protection in photovoltaic (PV) systems due to their low impact on inverter active power, their fast detection response in island, and reduced non-detection zone (NDZ). Integer multiples of the fundamental frequency as well as sub/inter-harmonics have both been used for the implementation of those schemes. Although utilization of sub/inter-harmonics present significant advantages, they also present significant limitations. This work investigates those limitations, particularly the ones that are caused by the parallel operation of multiple inverters. In addition, the distortion effect that is caused in the output current of the widely used PV microinverters with pseudo dc-link (PV Pdc-MICs) is discussed and thoroughly analyzed. It is concluded that when the injection is performed asynchronously (without communication among the inverters) sub/inter-harmonics are unsuitable for utilization under the parallel operation of multiple inverters. It is worth noting that a strategy is proposed in the current work that retains the effectiveness of the harmonic injection scheme under the injection of integer multiples of fundamental frequency. On the other hand, the distortion effect that is caused by the sub/inter-harmonics on PV Pdc-MICs output current, has been evaluated as insignificant when harmonics are used for anti-islanding purposes. Finally, the theoretical/mathematical outcomes of this work are supported by simulation and experimental results

Flexible Interlinking Converter With Enhanced FRT Capability for On-Board DC Microgrids

In this paper, a flexible interlinking dc/dc converter with enhanced FRTC is proposed to satisfy the advanced requirements of modern on-board DC MGs; the topology uses a non-isolated switched capacitor-type multilevel converter in combination with a cascaded step up/down converter to facilitate the incorporation of various types of energy storage and/or production units in a DC MG. Overall, a high voltage conversion ratio between the dc bus of the MG and the power unit is achieved. The proposed configuration facilitates the CCM operation of both the power unit and the DC MG and it is characterized by bidirectional power flow capability, enhanced FRTC, zero switching losses for the multilevel converter, limited complexity of the control scheme (compared to the counterpart multilevel solutions) and low real-time communication demands, corresponding so to the increasing flexibility needs of the EMS of modern MGs. The mathematical analysis and the dynamic performance of the control scheme of the proposed topology concept are evaluated via MATLAB/Simulink simulations and real-time CHIL tests, with the use of a 1202 dSPACE platform and an external dsPIC30F4011 microcontroller

Current Trends in Electric Vehicle Charging Infrastructure; Opportunities and Challenges in Wireless Charging Integration

Nowadays, the imperative need for the reduction of Greenhouse Gas (GHG) emissions leads to the wider adoption of environmentally friendly transportation means. As a result, various policies underpinning the Electric Vehicle (EV) deployment are legislated globally, and several technical advances contributing to the electrification of the transportation sector are pursued. In this paper, a comprehensive overview of the current status of the infrastructure utilized for the realization of both conductive and contactless (wireless) charging of an EV battery is conducted. Furthermore, the issue of EV integration in conventional distribution networks, as well as in future power system architectures, is discussed in detail. Particular focus is given to wireless (i.e., inductive) charging. A detailed presentation of the respective standards and charging levels, as well as the magnetic couplers and the compensation network configurations, is carried out. Moreover, innovative concepts such as dynamic and quasi-dynamic wireless charging, as well as future challenges and opportunities, are presented and discussed. Finally, smart control and communication techniques applicable to EV charging are presented in the context of the future Internet of Energy (IoE) concept

Energy yield estimation of on-vehicle photovoltaic systems in urban environments

Greenhouse gases from the propulsion systems of road transportations constitute a significant obstacle to achieve the Paris Agreement objectives. Nowadays, the substitution of conventional internal combustion engines with electric motors, along with electrochemical storage systems are the leading efforts to reduce the use of fossil fuels in road transportations. However, their limited driving range and the long charging times are the main technical factors that hinder the development of electromobility. Thus, energy harvesters and regeneration systems are increasingly incorporated in road vehicles, in order to increase their driving range. In this context, Vehicle Integrated and Applied Photovoltaics (VIAPVs) constitute an attractive prospect. The electricity yield for VIAPVs depends strongly on the route, the shadings due to the urban environment, the applied Maximum Power Point (MPPT) algorithm and the traffic conditions. In this paper, four commonly used commercial MPPT algorithms are experimentally evaluated, regarding their ability to extract the maximum available power simulating realistic city routes. The results show notable discrepancies in the performance of the studied algorithms, between terrestrial and VIAPV applications, highlighting the impact of poor MPPT performance in terms of power generation in moving vehicles

Experimental study of a low-voltage PV cell-level DC/AC converter

Summarization: This paper focuses on the design of a low-voltage power converter for an on-chip PV cell-level inverter. Various topologies are discussed for the DC/DC stage, whereas the ZVS quasi-resonant boost and the synchronous boost are considered the most appropriate for this application. Both the aforementioned topologies are modeled and evaluated in terms of efficiency, by the aid of PSpice simulations. Due to requirements and limitations of the available 0.18 μm CMOS process technology, the synchronous boost is finally chosen as the most appropriate solution. As for the DC/AC stage, the H-bridge inverter configuration is selected, as a simple, compact and cost-effective solution. A prototype converter is designed and constructed with discrete components, so as to validate the functionality and performance of the proposed system. Finally, experimental results are presented, indicating the high efficiency that can be achieved.Παρουσιάστηκε στο: 2021 10th International Conference on Modern Circuits and Systems Technologie

Analysis, design and simulation of an on-chip DC/DC/AC conversion system for PV applications

Summarization: This paper presents the analysis and design procedure of a low voltage, reconfigurable, on-chip DC/DC - DC/AC power conversion system for PV applications. The whole work is carried out in the context of a novel smart PV system development, which is based on integrated PV cell inverters. Various power converter topologies are investigated in order the most appropriate for the DC/DC and DC/AC power stages to be selected. The synchronous boost DC/DC converter and the H-bridge inverter are the preferred solution, in terms of complexity, efficiency and cost. The specifications of the power conversion system are given, along with the theoretical analysis for the synchronous boost converter and H-bridge inverter operation. Moreover, the chip design process is presented, highlighting the design constraints and limitations obtained. Finally, in order the functionality of the above concept to be validated, PSpice simulations are carried out, indicating the high efficiency and low complexity of the proposed power conversion system.Παρουσιάστηκε στο: 5th Panhellenic Conference on Electronics and Telecommunication