Primary topology selection and conversion in short-segmented on-road charging system for electrical vehicles

In an on-road charging system for electric vehicles where short-segmented primary coils are energised one by one, a serious power slump occurs when a secondary coil is placed in the middle of two primary coils. This issue can be tackled by powering double segmented primary coils simultaneously. First, four circuit topologies are established based on different connections of double primary coils. Then, a method of flux linkage superposition is utilised to identify two effective topologies. Forward series connection topology is further identified as an optimal selection based on performance comparison. In addition, topology conversion points are figured out after a comparison between the curve of received power in the single primary coil model and that in the double primary coil model. Afterwards, the topology conversion strategy, that is conversion of primary circuit topologies and adjustment of source frequency, is proposed to restrain the power slump. Finally, experiments are carried out to verify the theoretical analysis including primary topology selection and conversion strategy. Results show that with the application of the topology conversion strategy, the received power rises from 9.6 to 18.7 W when the secondary coil is located in the middle of the two primary coils.