LC/CL compensation topology and efficiency‐based optimisation method for wireless power transfer

Abstract

Wireless power transfer (WPT) has attracted a large amount of attention due to its inherent advantages such as convenience, safety, low maintenance, weather proof and so on. Compensation topology is crucial for WPT system due to its function of reducing reactive power and improving system efficiency. Series-series (SS) compensation topology is widely employed due to a simple structure and the characteristic of constant current output (CCO). However, it has three serious drawbacks: high-voltage stresses on compensation capacitors, poor CCO characteristic under practical situations and significant dependence on coupling coils. This study proposes LC/CL (primary inductor-capacitor and secondary capacitorinductor) compensation topology to eliminate aforementioned deficiencies of SS. The voltage stresses on compensation capacitors of LC/CL are much lower than those of SS. LC/CL also provides better CCO characteristics in imperfect scenarios. Load current of LC/CL compensated system only increases by 1.89% when the load is reduced by half. In contrast, the load current of SS compensated system increases by 6.87% with identical load reduction. An efficiency-based optimisation method is proposed for higher end-to-end efficiency as well. The validity of the optimisation is justified by both simulation and experiment. The efficiency of the optimised system is about 2% higher than that of a non-optimised system.

Simulation Model of a 2-kW IPT Charger with Phase-Shift Control: Validation through the Tuning of the Coupling Factor

“…One of the outstanding advantages of the SS topology for EV charging, which is not shared by any of the other three, is that the compensation capacitor on the transmitter side is independent of both the coupling factor and the load [9,14,15]. Despite some of the inherent problems of the SS topology, such as high voltages across the compensation capacitors or a drastic increase in the primary current if the secondary side is left open-circuited unintentionally [14,16], the SS topology is a usual choice when designing IPT-based EV chargers [10,14,[17][18][19][20][21][22][23]. It should be pointed out, however, that IPT chargers cannot currently compete with conductive chargers in terms of efficiency: while conductive chargers achieve an overall efficiency of above 90%, IPT chargers fall below that figure.…”

Control Scheme of a Bidirectional Inductive Power Transfer System for Electric Vehicles Integrated into the Grid

“…where the subscript 0 refers to the variable values at the operating point. From Figure 5, the battery voltage can be calculated as v b = V bm + R i i b and Equation (17) can, therefore, be written as:…”

“…Another advantage is a higher efficiency for a wide range of load currents [16]. On the other hand, the SS topology resembles a voltage source when the current through the primary circuit is kept constant [14], whereas it has a current-source behavior if the voltage on the primary side is maintained constant [17]. In this last case, an additional control scheme or protection circuit should be used to regulate the current through the primary winding in order to prevent overcurrents caused by the operation with low values of the secondary current, e.g., when the battery of the EV is charged in the constant-voltage mode [18].…”

Determining the Optimal Range of Coupling Coefficient to Suppress Decline in WPTS Efficiency Due to Increased Resistance With Temperature Rise

“…To improve the WPTS's efficiency, two compensation topologies named LC/S [4] and LC/CL [5] were proposed, the number of the coil turns, and the quality factor of the coils was optimized as well in [6]- [7]. Moreover, the performances of the square and circular coils in WPTS were investigated in [8], and the superiority of the square coil in improving system efficiency was revealed [8].…”