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In inductive power transfer (IPT) systems, misalignment and wide load range can lead to high current and control complexity. This can affect the performance of high-power systems. In this article, a method to minimize converter and primary resonant circuit currents based on an asymmetrical factor is proposed to improve IPT system performance over wide misalignment and load ranges. The proposed asymmetrical factor incorporates two design variables: an asymmetrical voltage factor and an asymmetrical compensation factor. These help to minimize current from two perspectives. First, they tend to redistribute zeroes and poles for power versus frequency characteristics. The power characteristic can be asymmetrical and monotonic over the working switching frequency range. Second, the input impedance angle can become insensitive to coupling factor and to load by adjusting the frequency that corresponds to the minimum input impedance angle. The current increases by only 15% over a 2:1 coupling coefficient variation range at rated load. Analysis and design guidelines are presented for the proposed method. A 2.1-kW prototype has been prepared to verify the approach.

Inductive power transfer (IPT) technology uses large resonant inductors as compensation components. In this article, a spatially nested magnetic integration method is proposed to integrate discrete inductors into an IPT transformer structure. Unipolar transformer coils are employed and are decoupled orthogonally from a nested solenoidal inductance coil for various misalignment cases. The variations of the coupling coefficients and the magnetic flux density distribution are presented with the three-dimensional finite-element modeling tool. An LCC series compensation circuit is selected to implement the proposed method with an optimal efficiency design. A 4-kW prototype with a 160 mm airgap is implemented to demonstrate the validity of the proposed method. The experimental results show that the compact structure retains the outstanding performance and avoids significant cross coupling for lateral, vertical, and axial misalignment. The maximum conversion efficiency of the proposed system is 96.7% at full output power and stays above 91.6% throughout the misalignment range.

Inductive power transfer (IPT) technology is useful for electric vehicle (EV) charging because of safe, flexible, and convenient features. In this paper, an integrated IPT system design employing variable inductor control is proposed to achieve a target constant current (CC) and constant voltage (CV) battery charging profile with misalignment tolerance. The system is implemented under a fixed switching frequency in both CC and CV modes. Soft switching of the primary inverter can be achieved over the entire charging process and allowed misalignment range without additional switches or dc–dc converters. Theoretical circuit analysis and the system design process are presented. A 3.3-kW prototype is implemented with a 210-mm air gap to demonstrate the validity of the proposed method. Experimental results show that the target CC and CV charging profile can be achieved by adjusting the variable inductor with up to 120 mm of lateral and 300 mm of vertical misalignment. The maximum efficiency of the proposed system is 96.1% at full output power and stays above 95% throughout CC operation.

Inductive power transfer (IPT) system which has advantages of safety, convenience, and flexibility is attractive in battery charging applications. Constant current/constant voltage (CC/CV) charging profile is important to extent the lifetime and improve the performance of the battery. This paper proposes compensation topologies with additional shunt inductor added to the primary or secondary side on the basis of series/series (S/S) compensation, and load-independent CC/CV outputs with near zero phase angel (ZPA) between the input voltage and current can be achieved at two different frequencies. The proposed topologies can reduce passive component counts compared with conventional topologies which have the above characteristics. The nature of gyrator provides a simple way to analyze the characteristics of resonant topologies. In addition, the design freedom can be increased. A 2kW prototype is set up to verify the performance of the system. Frequency can be fine-tuned to improve output accuracy in CV mode, and help maintain high efficiency in CC mode. Experimental results show that zero voltage switching (ZVS) can be achieved over the entire charging process, and the achievement of near ZPA is conductive for high efficiency. In CC mode, the efficiency stays above 95%, and the peak value is 95.5%.

In inductive power transfer (IPT) applications, load-independent constant current (CC) charging and constant voltage (CV) charging has become more popular. In a high-order resonant network in IPT systems, there are usually multiple resonant frequencies. Through parameter design, Realizing both the load-independent voltage and current transfer characteristics in the same circuit is possible. In this paper, a gyrator-based converting-splitting method is proposed to realizing CC/CV charge under the zero-phase angle (ZP A) condition for the primary inverter without additional switches. In this method, the circuit model is split into several gyrators after impedance conversion. Soft switching of primary inverters can be achieved over the entire charge process. The system design is experimentally verified on a 2.8 kW prototype of LCC-S compensated IPT system. The efficiency of the LCC-S compensated IPT system is up to 96.3% and 98.4% when the IPT system operating at resonant frequencies that achieve CC output and CV output, respectively.

To minimize primary current and enhance the misalignment tolerance of inductive power transfer systems under wide load range, this paper proposes an asymmetric parameter design method in the series-parallel (S-P) compensated topology with constant current (CC) output. The asymmetric parameters include asymmetric power transfer ratio and asymmetric compensation factor, which aims to redistribute the zeros and poles of system. With this asymmetric parameter design method, the IPT system can be made to achieve an asymmetric and monotonic power characteristic, as well as an input impedance angle that is insensitive to coupling and to load. Meanwhile, global ZVS conditions for primary inverter are always ensured. The experimental results show that the variation in primary current is 10% at rated load within the coupling coefficient range of 0.2~0.3.

Inductive power transfer (IPT) system for electric vehicle battery charging has many advantages over the traditional plug-in system. EV battery can be regarded as a wide range load according to the charging profile. The charging process requires constant current (CC) stage and constant voltage (CV) stage. The charging profile for IPT system is influenced by inductively coupled transformer, compensation structure and operating frequency. This paper proposes an IPT topology which naturally obtains CC and CV output functions simultaneously without increasing the complexity of control system. The system switches between the two charging modes in succession along with the change of load condition. It operates under the CC mode when the load resistance is small, which corresponds to the beginning of battery charging state. With the increase of load resistance, it switches to CV mode at a load turning point after which the battery is under the state of cutoff voltage. As the system is completely compensated, zero phase angle input is achieved during the entire charging process, which realizes soft switching for the entire load range. A fixed frequency control method is used to adjust the output accurately. The experimental IPT system is established to verify the theoretical analysis.

Aiming at the bad performance of EMI filter in the high frequency band, the non-ideal factors of common-mode chokes and the limitations of the existing high-frequency model are summarized. Considering the frequency characteristics of core material and the influence of parasitic capacitance, an improved cascaded Foster network model is established, and then the common-mode and differential-mode high-frequency equivalent circuits of EMI filter in lS0kHz-30MHz are developed. Furthermore, an EMI filter design method based on the optimization of the impedance characteristics of common- mode chokes is proposed. An experiment is carried out to verify the method by an 1.2SkW Boost PFC prototype. Results indicate that the device with the proposed EMI filter can pass the conducted EMI test successfully, and the design scheme can provide effective guidance for the remediation of conducted electromagnetic interference.