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This paper presents a novel active power control scheme for SRMs that are used as S/G units at MEAs; the proposed method uses a vector-controlled SAF, facilitating the acceleration of the SRM during starter mode and the efficient power control of the SRG at various operational points during generator mode. Moreover, an energy storage unit is incorporated in the SAF, aiming at enhancing the SRM's starting torque production and taking full advantage of the SRG's energy generation capability, through the appropriate phases’ magnetization regulation that is imposed by the developed adaptive SAF vector control. In addition, the proposed scheme provides enhanced FRTC during both modes of operation. The mathematical analysis is verified through MATLAB/Simulink simulations, while the performance of the S/G concept under study is evaluated via real-time CHIL tests, with the use of the dSPACE 1202 (MicroLabBox) platform and the 16-bit dsPIC30F4011 microcontroller. [ABSTRACT FROM AUTHOR]

SRM is one of the most attractive electric machines to be used as a S/G in the future MEA thanks to its special physical characteristics that facilitate its direct coupling to the propulsive unit; however, the controllability of the SRG at different operational points, imposed by the specific application, is critical. In this article, a novel active power control scheme which uses a vector-controlled SAF is proposed, in order to efficiently drive the SRG in a wide set point range. Considering the highly non-linearity of the SRM operational behavior, an adaptive phases’ magnetization regulation is applied, aiming at taking full advantage of the SRG's energy production capability, in compliance with the MEA power system specifications and limitations. The mathematical analysis is verified through simulation results, while the SRG concept under study is validated via a RT CHIL implementation. [ABSTRACT FROM AUTHOR]

This paper investigates the wireless power transfer (WPT) system incorporation into dc microgrids applications. Emphasis is given on the mathematical analysis of the series–series (SS) WPT system for constant voltage source loading conditions that cannot be effectively described by the equivalent constant resistance model. For this reason, the complete harmonic analysis is considered in this paper in order to study the real operational characteristics of SS-WPT systems that interface to a dc bus. The proposed system interconnects a dc bus with various distributed energy sources, while the ability of constant power generation behavior of the proposed system is revealed and examined for various SS-WPT system parameters’ values, highlighting its advantageous characteristics for distributed energy exploitation. Additionally, the incorporation of the SS-WPT system in distributed energy sources exploitation offers reduced wiring complexity and installation flexibility. Experimental and simulation results are presented, validating the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper introduces a new cross-correlation anti-islanding detection scheme for module-integrated converters (MICs) with pseudo dc-link. The proposed scheme periodically injects a second-order harmonic current component of low magnitude (in open-loop mode) and evaluates grid response by means of correlation. The proposed scheme is highly reliable, providing nondetection-zone free operation, fast detection, and compliance with the relevant power quality and anti-islanding standards. Additionally, it excels in lower computational cost, reduced fault detection zone, and higher output power quality, compared to the referenced anti-islanding schemes that are compatible with MICs. Last but not least, it can be implemented in MIC platforms without requiring an output current sensor, being an easily upgradable solution in software level. A firm theoretical framework that considers both high penetration levels of PV systems and weak grid conditions is also included in this paper. The theoretical framework, as well as the effectiveness of the proposed scheme, is verified through extensive experimental results for various electrical-network parameters and nonlinear loading conditions. Finally, a comprehensive comparison between the proposed method and the most common anti-islanding techniques (compatible with MICs) is performed, leading to some valuable conclusions from MICs perspective. [ABSTRACT FROM AUTHOR]

This paper studies the significant impact of distributed-energy-resource (DER) inverters (which are connected to the same node) on anti-islanding protection of DER-installations. As it concerns the harmonic injection-based schemes, the induced harmonic voltage component that is provoked by each inverter is compromised, as synchronous injection (injection at the same time intervals) among the inverters cannot be reassured. Therefore, harmonic injection-based anti-islanding schemes will fail if the harmonic voltage component falls below a certain level. In this framework, a novel metric (i.e., the upgrade factor, UF) is introduced, indicating the supplementary power (of DERs) that can be installed in the same point of common coupling without compromising the effectiveness of the harmonic injection scheme. As this metric enables the evaluation of harmonic injection schemes prior to the future integration of DERs, it could be a substantial addendum into the relevant standards that evaluates the anti-islanding features of grid-tied DER-inverters. Finally, this paper proposes a technique (implemented in the software level), which maximizes UF and reassures the effectiveness of the harmonic injection schemes under the power variations of installed inverters. Extensive simulations and experimental tests have been conducted that verify the effectiveness of the proposed strategy under various penetration-levels and islanding-network conditions. [ABSTRACT FROM AUTHOR]

Over recent years, the output power of micro-inverters [module-incorporated inverter (MIC)] is progressively pushed to higher levels, following the current photovoltaic (PV) modules market trends. The interleaved Flyback inverter—under discontinuous conduction mode of operation (DCM)—is an appealing solution for PV applications which are based on MIC technology. This topology provides increased power level for distributed PV generation exploitation with simple control configuration, high efficiency, and reduced filter size. In this paper, the harmonic injection capability is incorporated into the interleaved Flyback inverter for the implementation of an active anti-islanding scheme. A suitable technical solution is proposed that bypasses the unfolding H-bridge, without affecting the active power generation of the inverter and without requiring any hardware modification. In addition, a mathematical model based on the instantaneous power balance theory is presented, being a powerful analysis tool for inverters operating under complete magnetic discharge such as the Flyback inverter (either conventional or interleaved) under DCM or boundary conduction mode of operation. The proposed model predicts accurately the steady-state operational behavior of the Flyback inverter under current harmonic injection, either in grid-tied or islanding operation. The proposed technical implementation method and mathematical model are verified through simulation and experimental results. Finally, an anti-islanding set-up based on the proposed harmonic injection technique is presented and implemented into the Flyback micro-inverter. The proposed set-up is verified through experimental results on various quality factor values, as well as for weak grid conditions. [ABSTRACT FROM AUTHOR]

During the last decade, autonomous residential photovoltaic (PV) systems have been widely installed, especially in remote areas (islands, rural territories, etc.), in an effort to produce electrical energy in a reliable and inexpensive manner. The appropriate design of a PV system and the compatibility of its power quality indices with national and international standards are crucial for efficient and economical autonomous operation of the system. To this direction, the critical parameters of a three-phase autonomous PV residential system are properly determined. Moreover, a new design methodology that meets the demanded standards and improves further the power quality is also introduced. Finally, an optimization algorithm is designed utilizing artificial intelligence techniques. The analytical results are corroborated by extensive simulation results and insightful discussions are provided demonstrating the efficiency of our proposed design. [ABSTRACT FROM PUBLISHER]