Impact of Coil Misalignment in Data Transmission over the Inductive Link of an EV Wireless Charger

Abstract

The penetration rate of electric vehicles (EVs) will experience a relative increment in the future, so easy to use ways to recharge will be demanded. In this sense, wireless charging represents a safe charging method that minimises user intervention. In a similar way to conductive charge, wireless charging requires some information exchange between the charger primary side and secondary side (battery) for safety and operational reasons. Thus, wireless chargers depend on a communication system for their controlled and correct operation. This paper analysed the communication performance of a wireless EV charger in which the communiction device is part of the wireless power transfer system. Particularly, this work studies how the communication system reacts to power coil displacements, which commonly occur in their conventional performance. The results show that the compensation topology selected to ensure the resonant operation clearly impacts on the communication performance. In particular, the theoretical model and the simulation results demonstrate that the asymmetrical compensation topologies are more stable in terms of the wireless communication channel capacity.Energies 2018, 11, 538 2 of 11 For this information exchange, wired communication is advised against, as it will eliminate the main benefits reported by the wireless chargers. Several wireless-based communication techniques have been proposed as alternatives. The more straightforward strategy consists of opting for some commercial wireless modules, which could be inserted in the primary and secondary sides. Coordination between the modules and some security drawbacks are the main concerns which could make this solution inoperative [7]. To obtain more reliable communication, these solutions can be complemented, or even avoided, by using the same wireless link that is involved with the wireless charger.Several papers have been published regarding the use of the coils for the simultaneous transmission of data and power in EV wireless chargers. In [8], the authors designed a scheme where both data and power are transmitted at the same time. Specifically, data and power are generated at different frequencies (1.6 MHz and 22.4 kHz, respectively). A similar scheme was published in [9]. Both schemes are complex to implement, as they have to add high-frequency data communication modules, extra coils and filters to separate the power and data processing accordingly. As demonstrated in [10,11], additional costs can be avoided if the power converters employed to create the high-frequency signal generate the data signal too. According to this strategy, data and power are transmitted at the same frequency. The work in [10] included experimental results which show how this kind of combination is feasible for a 700-W wireless charger operating at 22 kHz. In fact, the spectrum of the data signal is centered at the frequency in which the wireless charger resonates. On the other hand, the data protocol is based on the BFSK (Binary Frequency Shift Keying).As demonstrated ...

Simultaneous Wireless Power and Data Transfer for Electric Vehicle Charging: A Review

“…The effects of misalignments on power transmission have been widely studied, but it should be noted that the misalignment between coils also directly affects the bandwidth of the data system. As indicated in [129], vertical misalignment affects the communication capacity of the channel more than horizontal misalignment. Nevertheless, the bandwidth alteration is not only related to the direction of misalignment, but also to the compensation system used.…”

SS and LCC–LCC in Simultaneous Wireless Power and Data Transfer: A Comparative Analysis for SAE J2954-Compliant EVs

“…To the best of authors' knowledge, no comparative study has been carried out to analyze the performance of these two main technologies in terms of data transmission. In particular, it is useful for the designers to investigate how the data transfer performs when there is a coil misalignment, which is a typical operation of EV wireless charger [16]. In fact, SAE J2954 establishes that misalignment could occur in three axes (X, Y , Z) and sets maximum conditions for each of them.…”

Mutual Inductance Estimation Using an ANN for Inductive Power Transfer in EV Charging Applications

“…Every inductive power transfer (IPT) system has limitations in terms of dependence on the coupling factor of the magnetic couplers. According to the Faraday law of electromagnetic induction, the induced voltage on the receiver pad depends on the rate of change in the magnetic flux that traverses it [1]. Generally, the coupling factor decreases from the nominal operating conditions when a misalignment between the transmitter and receiver pads occurs.…”