A Low-Voltage and High-Current Inductive Power Transfer System With Low Harmonics for Automatic Guided Vehicles

This paper proposes the series-series compensation topology to realize a low-voltage and high-current inductive power transfer system (IPT) for the automatic guided vehicles (AGVs). Since the height of the AGV chassis is in the tens of mm, the coupling coefficient is close to 1, resulting in a tightly coupled IPT system. This paper has three main contributions. First, it reveals that the high-order harmonic currents in a tightly coupled IPT system could be very significant. Second, it quantifies the impact of the high-order harmonic currents on the efficiency, which shows the efficiency can be reduced. Third, it proposes an effective method to design the parameters in order to reduce the harmonics and maintain high efficiency. Aiming at the charging of AGVs, a prototype is constructed. The magnetic coupler size is 220 mm x 220 mm x 10 mm. When the airgap is 10 mm, it achieves 1.8-kW power transfer with a dc-dc efficiency of 89.9% from a 400-V dc source to a 24-V dc load, and the charging current is 74 A. When the airgap varies from 5 mm to 15 mm, the power variation is within +/- 350W, and the efficiency is not affected. The fast Fourier transform analysis of the experimental currents also validates the theoretical analysis and the simulation results.