| Magnetic coupling wireless power transfer(WPT)is a technology that comprehensively applies electrical theory,power electronics technology,and control theory,and uses a magnetic field to transfer electrical power from the power grid or battery to electrical equipment in a non-electrical contact way.The magnetic coupler in the traditional WPT system is composed of a pair of circular or rectangular coils.When there is an angular or positional misalignment between the transmitter and receiver,it will reduce the system efficiency and even lead to the system can not work.To solve this problem,omnidirectional WPT technology came into being.Such technology has a good position and angle adaptability.The omnidirectional WPT systems can be classified into two-dimensional(2-D)and three-dimensional(3-D)omnidirectional WPT systems.To achieve high-performance omnidirectional WPT,the optimal design of the composite electromagnetic coupler and the control of omnidirectional magnetic field direction are two key issues.In the aspect of optimal design of electromagnetic coupler,according to the different magnetic field distribution dimensions generated by the omnidirectional magnetic transmitter,it can be classified into 2-D and 3-D omnidirectional magnetic transmitters.According to the different structures of the transmitter,it can be classified into 2-D planar and 3-D volumetric structures.The 2-D planar transmitter structure can save the installation space on the transmitting side,but most of these transmitters only have the 2-D omnidirectional magnetic transmitting ability.On the premise of using a planar singlecoil receiver,they can only realize 2-D omnidirectional WPT.The 3-D volumetric transmitter structure usually has the 3-D omnidirectional transmitting ability,but it occupies a large installation space.To make the magnetic coupler more compact,it is urgent to investigate a planar structure with 3-D omnidirectional transmitting ability.In the aspect of magnetic field direction control,rotating magnetic field and targeting magnetic field regulation are the main ways to realize an omnidirectional magnetic field.Most studies excite the current with a 90° phase difference in two orthogonal coils to generate a 2-D rotating magnetic field.Few works of literature investigate the relationship between the phase difference of excitation current,the uniformity of rotating magnetic field,and the stability of output voltage when the orientation of the receiver changes.In addition,most studies only realize the 2-D rotating magnetic field,and a planar singlecoil receiver can only realize the 2-D omnidirectional WPT.To realize 3-D omnidirectional WPT,it is urgent to investigate the 3-D rotating magnetic field and its control methods.The targeting magnetic field can reduce the magnetic leakage of the magnetic coupler and improve its efficiency.At present,there is no effective method to detect the orientation of the receiver and control method of the excitation current.It is urgent to study an effective control method for the targeting magnetic field.To solve the above problems,combined with the specific requirements of different applications,this thesis mainly focuses on the composite magnetic couplers and magnetic field control methods to realize high-performance omnidirectional WPT.The main research work is as follows:(1)An omnidirectional WPT system based on cylindrically curved coils and a 2-D rotating magnetic field.For the application of electrical equipment in cylindrical space,an omnidirectional WPT system based on cylindrically curved coils and a 2-D rotating magnetic field is proposed.To reduce the output voltage fluctuation when the receiver orientation changes,firstly,the circuit model of the system is established based on the three-phase LCC-S resonant compensation network.Then,the relationship between the system output voltage and the phase difference of mutual inductance and excitation current is deduced.The magnetic field mathematical model of cylindrically curved coils is established based on biotsavart’s law.Then,the relationship between the magnetic field distribution characteristics and the phase difference of excitation current is analyzed.The phase difference of excitation current is optimized from the perspective of 2-D rotating magnetic field uniformity,and the essence of the stable output voltage is revealed.Finally,the correctness of obtaining a uniform rotating magnetic field and stable output voltage by optimizing the phase difference of excitation current is verified by simulation and experiment.(2)An omnidirectional WPT system based on ring-dipole coils and a 3-D rotating magnetic field.For the application of strict volume limitation of the transmitter,the ringdipole coils with a 3-D omnidirectional transmitting ability and planar structure are proposed.To make the receiver located in any direction that can capture magnetic energy,the expression of the excitation current which can make the ring-dipole coils generate a3-D rotating magnetic field is given.On this basis,a 3-D rotating magnetic field control method based on phase-shift control of the three inverters is proposed.To reduce the output power fluctuation when the orientation of the receiver changes,the parameter design method of the ring-dipole coils and its magnetic coupler is given.Finally,the effectiveness of the proposed ring-dipole coils and its 3-D rotating magnetic field control method to realize 3-D omnidirectional WPT with a 2-D planar transmitter structure is verified by experiments.(3)Multiple receivers omnidirectional WPT system based on reticulated planar coils and a 3-D rotating magnetic field.For the application of multiple receivers,reticulated planar coils suitable for multiple receivers and with a 3-D omnidirectional transmitting capability are proposed.To make multiple receivers located in any direction that can capture magnetic energy,the influence of excitation current on the magnetic field distribution characteristics is studied.Then the excitation current expression that can make the reticulated planar coils generate a 3-D rotating magnetic field is given.On this basis,a 3-D rotating magnetic field control method based on phase-shift control of four inverters is proposed.To obtain a stronger and more uniform magnetic field distribution,the design method of the grid width is given.Finally,the effectiveness of the proposed reticulated planar coils and its 3-D rotating magnetic field control method to realize multiple receivers 3-D omnidirectional WPT with a 2-D planar transmitter structure is verified by experiments.(4)An omnidirectional WPT system based on composite planar coils and a targeting magnetic field.To improve the system efficiency,an omnidirectional WPT system based on composite planar coils and a targeting magnetic field is proposed.To realize high efficiency no matter how the orientation of the receiver,the excitation current calculation method of a targeting magnetic field generated by the composite planar coils is given.To realize the targeting magnetic field without using angle detection and communication links,the circuit model based on three independent inverters and LCC resonance compensation networks is established.Then,the relationship between the efficiency of the magnetic coupler,mutual inductance,and phase-shift angle is deduced.On this basis,a targeting magnetic field control method based on mutual inductance identification and phase-shift angle optimization is proposed.Finally,the effectiveness of the proposed targeting magnetic field control method to realize the magnetic field directional transmission and improve the efficiency is verified by experiments. |
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