Real-time coupling coefficient estimation and maximum efficiency control on dynamic wireless power transfer for electric vehicles

Abstract

Maximum efficiency control using a DC/DC converter on the secondary side can improve transmitting efficiency in dynamic wireless power transfer system for electric vehicles. However, the information of coupling coefficient has to be estimated to implement the control although coupling coefficient changes dynamically. In this paper, a simple method of coupling coefficient estimation with RLS (Recursive least squares) filter is proposed. Dynamics of WPT system is analyzed with transfer functions. Moreover, the modeling and the control method of DC/DC converter are introduced. The experimental results of real-time coupling coefficient estimation and maximum efficiency control are provided and they indicate the effectiveness of the proposed control in a real dynamic wireless power transfer system for EVs.

A Maximum Power Transfer Tracking Method for WPT Systems with Coupling Coefficient Identification Considering Two-Value Problem

“…Energies 2017, 10, 1665 2 of 13 parameters, such as coupling coefficient and load resistance [22,23]. Therefore, in order to achieve MPTT, the identification of these changing parameters is needed previously.…”

“…However, the equations require the information of the resonant currents on primary and secondary sides, which will increase the difficulty in practice. References [22,23] present a dynamical identification method of coupling coefficient, and it only need to measure the parameters on the secondary side. However, it needs to measure the RMS value of alternating currents, which will bring harmonic interference.…”

“…Since the load resistance of a practical WPT system varies with time, therefore using DC/DC converters to do the impedance matching is more suitable for the frequent load variations [19]. However, one thing about the impedance matching using DC/DC converters is that it cannot be realized when unknowing the parameters, such as coupling coefficient and load resistance [22,23]. Therefore, in order to achieve MPTT, the identification of these changing parameters is needed previously.…”

Secondary-side-only Control for High Efficiency and Desired Power with Two Converters in Wireless Power Transfer Systems

“…Past research described thoroughly how to model the converter by the state space averaging (27) (30) . Thus, in this paper the modeling process will be omitted.…”

“…This variation is introduced to prove the proposed control robustness. In both the conventional state-of-the-art efficiency control and the proposed one, the efficiency maximization is achieved with the equivalent load impedance optimization method, as explained in Section 2 and Section 4; this method is sound and it has been adopted in previous literature as (20)- (22) and (25)- (30) . In the figures, the instantaneous values are indicated by thin lighter lines while averaged values are represented by thicker dark lines.…”