Pad misalignments are almost inevitable in most inductive power transfer (IPT) systems. It tends to cause parameter variations and thus significantly affecting the performance of the IPT system. In this paper, a hybrid IPT system with misalignment tolerance using quadruple D quadrature pads (QDQPs) is proposed to tolerate x-, y-, z- and diagonal misalignments with load-independent output voltage, simplifying or even canceling control schemes. Besides, the proposed approach can restrict the increase of the primary current when the secondary side moves out of the operating region. Moreover, a new parametric design method is presented according to the misalignment characteristics of QDQPs. The method can limit the output voltage fluctuation to a certain range given a predetermined misalignment distance. A 3.5-kW prototype was built to verify the proposed hybrid IPT system. The primary and secondary coil sizes are both 400 mm×400 mm and the air gap is 150mm. Experimental results demonstrate that the proposed hybrid system can tolerate -150 mm to +150 mm x-misalignment, -150 mm to +150 mm y-misalignment, -20 mm to +35 mm z-misalignment, and -100mm to +100mm diagonal misalignment with load-independent output voltage. Within the predetermined mis-alignment range, the output voltage fluctuation is less than 5%.

Load-independent output characteristics of induc-tive power transfer (IPT) systems are increasingly popular in battery charging. This paper proposes a novel variable-parameter T-circuit (VT) for an IPT system charging a battery with constant current (CC) or constant voltage (CV) output. The VT can transfer a CC/CV input to a CC or CV output by using an ac switch and a passive component (inductor or capacitor). An IPT system with a VT for CC-CV charging can reduce the number of passive components and ac switches. Besides, the proposed VT merits more design freedom of charge current/voltage with the constraints imposed by the loosely coupled transformer parame-ters compared to that of the traditional one. In addition, there are three kinds of VTs for various IPT charging systems with differ-ent requirements. A 400-W laboratory-scale prototype with a 150mm air gap was built to verify the theoretical analyses. Both electronic load and lead-acid battery are utilized to verify the charging profile of the proposed method. The experimental re-sults of the IPT system indicate that the fluctuation of the charg-ing current in CC mode is less than 2%, and the change rate of charging voltage in CV mode is within 2.9%. The maximum overall efficiency 93.93% of the charging system is achieved from a dc 110V input to a dc 100V output.