Energy storage plays a fundamental role in balancing the power fluctuations induced by the distributed generation of renewable energy sources. In this scenario, electric vehicles can strongly contribute to exchange power with the grid through their on-board batteries. When the vehicle is parked, the battery can be discharged, injecting active power into the grid, provided that its state of charge will be restored before vehicle utilization. This paper presents a comprehensive step-by-step design of a wireless charger for a Vehicle-to-Home application. The design procedure begins from the constraints disposed by the Italian reference technical rules for Low Voltage utilities and by the standard SAE J2954 for Wireless Power Transfer for electric vehicles. The selection of the output power of the battery is followed by the power sizing of each stage of the bidirectional wireless charger.

The one-element resonant topologies of the wireless battery chargers (WBCs) for electric vehicles (EVs) are analyzed with the aim of giving both a thorough assessment and a comprehensive comparison of the performance of the topologies. The analysis is carried out in terms of the following performance indexes: efficiency versus power injected in the EV battery, power sizing factor of the supply inverter, power sizing factor of the transmitter and receiver coil set, current sizing factor of the supply inverter, and behavior under the extreme conditions of open- and short-circuited operation of the receiver. At first, the two topologies with series resonance of the receiver coil and series/parallel resonance of the transmitter coil are investigated and their performance indexes are formulated. Then, the investigation is extended to the two topologies with parallel resonance of the receiver coil and series/parallel resonance of the transmitter coil. Afterward, merits and limits of the topologies are discussed. Measurements obtained from series-series and series-parallel WBC setups are given that corroborate the theoretical findings.

The Smart Transformer (ST) is a power electronics-based transformer, which operates as grid-forming converter in the low voltage-fed grid. It synthesizes the voltage waveform with magnitude, phase and frequency independently from the main power system. If a meshed operation of the ST with a conventional transformer is required, to improve the power flow control and to control the voltage profile, the voltage waveforms between the two grids have to be synchronized. The switching under different voltage magnitude, phase or frequency, can lead to a large power in-rush. This work proposes a synchronization strategy that enables a seamless transition of the ST to parallel operations with conventional transformers. Differently from classical communication-based methods, this work addresses a more realistic implementation case with limited communication infrastructure. The ST relies only on local measurements and on its advanced control capability to determine the effective switch to parallel operations. The performance of the proposed strategy has been proved analytically and through simulations in a PLECS/MATLAB environment, and validated experimentally by means of Power-Hardware-In-Loop (PHIL) evaluation.

The paper deals with the wireless battery chargers (WBCs) of electric vehicles (EVs) and refers to a resonant WBC that utilizes a rectifier-chopper stage in the receiver side to control the charging current/voltage of the EV battery. Two topologies, namely series-series and series-parallel, are considered, and their performance in terms of efficiency and power sizing is investigated. Power sizing is formulated for both the power source and the coil coupling set. Instrumental in the investigation is the proper modeling of the rectifier-chopper stage. Data used for calculating the performance are obtained from a WBC setup for electric city-car. Comparison of the results reveal the overall convenience of the series-series topology.

Different phase-locked loop algorithms applied to three-phase grid voltages implement a closed control loop based on the Park transform to obtain the grid voltage instantaneous phase and frequency. When a single-phase grid voltage must be processed, one of the inputs of the Park transform is generated by a block that, starting from the available voltage, computes an additional signal with the same frequency of the grid voltage and ideally orthogonal to it. This paper introduces a novel method for the orthogonal signal generation and gives a detailed analysis of its functioning. Then, after sizing the control loop of the phase-locked loop, the paper considers different aspects relevant to implementation of the presented orthogonal signal generation and of the phase-locked loop on a digital signal controller, such as the finite numerical resolution, the memory usage and the computation time. Finally, the paper checks the comprehensive performance of the orthogonal signal generation and phase-locked loop pair by experimental tests and compares the obtained results with those available in the literature.

This paper addresses the optimization of the compensation networks of a wireless power transfer system. Optimization is performed by means of a genetic algorithm that looks for the reactances of the elements of the compensation networks that maximize the power transfer efficiency and the power transferred to the load. In addition, the algorithm selects the solutions that are less sensitive to the difference between the theoretical and actual reactances. The last part of the paper describes the prototypal setup used for the tests and supports the theoretical findings by reporting experimental results.