Research On Inductive Power Transmission System Of Automatic Guided Vehicle Based On Z Impedance Network

The use of Automatic Guided Vehicles(AGV)has greatly improved the work efficiency of industries such as logistics and express delivery and harbor.Applying Inductive Power Transfer(IPT)technology to the AGV charging system can solve the problems of mechanical failure,aging,and electric sparks at the traditional contact charging connector,and provide AGVs with a way to get rid of sockets and realize unmanned.The convenient charging method improves the operation efficiency of the AGV system.Generally,the pickup coil installed on the AGV is close to the ground transmitting coil,and the coupling coefficient is high.Under such conditions,to meet the "low voltage and high current" requirements of AGV charging,the IPT system often works in a state where the current of the transmitting and receiving coils is unbalanced,and there are problems of high coil loss and low system efficiency.In addition,under low-voltage and high-current operation,the accidental open circuit or short circuit of the load will cause overvoltage or overcurrent,which may seriously damage the AGV and its power supply system.To this end,this paper proposes to introduce the Z impedance network into the resonance compensation circuit of the IPT system,and use the buck-boost gain characteristics and the anti-open/short-circuit characteristics of the Z impedance network to improve the charging efficiency and charging safety of the AGV inductive charging system.Firstly,based on the two-port mixed-parameter model of the Z-impedance network,this paper establishes two ideal transformer equivalent models of the Z-impedance network under different parameters,and derives and analyzes the corresponding relationship between the equivalent model parameters and the actual Z-impedance network parameters.Based on the equivalent model of Z impedance network,three IPT system compensation topologies based on Z impedance network,Z-S,S-Z,and LCL-Z,are proposed,and the input and output characteristics and opening and short circuit capabilities of the three topologies are analyzed and compared.Secondly,the first-order approximation method is used to derive the relationship between the equivalent load resistance,input voltage,transmission efficiency and transmission power of the S-Z compensation topology.Under the same output current condition,the transmission efficiency of S-Z,LCL-LCL and S-S three constant current output topologies,the relationship between the capacity of the passive components of the compensation network and the transmission power are compared and analyzed,and the loss distribution of the three topologies is compared and analyzed.The advantages of S-Z compensation topology is analyzed,too.Finally,the design method and control strategy of IPT system using S-Z topology to achieve low voltage and high current are proposed.Combined with the circuit and electromagnetic simulation results,a 480 W AGV induction charging experimental platform was designed and built,with a transmission efficiency of up to 90.08%.The transmission efficiency comparison experiment shows that the transmission efficiency of the S-Z topology is better than that of the LCL-LCL topology,especially when the system is lightly loaded,the transmission efficiency can be 13% higher than that of the LCL-LCL compensation topology.At the same time,the system load open circuit and short circuit conditions were simulated in the experiment,and the S-Z topology’s ability to resist open and short circuits was verified.