Wireless electric energy transmission system added with three-pole relay coil

Abstract

The invention provides a wireless electric energy transmission system added with a three-pole relay coil. The system comprises a power source module, an inversion module, a transmission coil module, a rectification module and a load. The power source module comprises an ideal voltage source; when the ideal voltage source is powered on, electric energy is converted into alternating current through the inversion module and input into a transmitting coil of the transmission coil module. In the transmission coil module, electric energy in a transmitting coil is transmitted to a receiving coil through a three-pole repeating coil, and meanwhile, part of electric energy is directly transmitted to the receiving coil from the transmitting coil; the alternating current of the receiving coil is converted into direct current through the rectifier module to supply power to a load. According to the invention, the leakage magnetic flux density of the charging area is reduced, so that considerable system transmission efficiency is ensured to be kept when the coil is subjected to plane dislocation, and a wireless power transmission system is enabled to have relatively high plane offset tolerance.

Description

Technical Field

[0001] The invention relates to the field of wireless power transmission, and in particular to a wireless power transmission system with a three-pole relay coil added. Background Art

[0002] Wireless power transmission technology is used in implantable medical devices, electric vehicle wireless charging and other fields due to its characteristics of no physical contact and high safety. At present, the most widely studied and applied wireless power transmission system is a two-coil system using two magnetic energy coil groups, and compensation capacitors are used on the transmitting side and the receiving side respectively to make the transmitting side and the receiving side work in a self-resonant state at the same time (Fu Wenzhen, Zhang Bo, Qiu Dongyuan. Design of wireless power transmission system based on resonant coupling [J]. Mechanical and Electrical Engineering, 2011, 28(06): 746-749.), so as to improve the transmission efficiency of the wireless power transmission system. However, the transmission performance of the two-coil transmission system is highly sensitive to the relative position of the transmitting coil and the receiving coil. Generally, the placement state in which the transmitting coil and the receiving coil are axially aligned is called the positive alignment state. At this time, the coupling coefficient between the coils is high and the system transmission performance is good. When the position of the receiving coil changes in the placement plane, the coupling coefficient between the coils decreases, and the coil current increases, resulting in reduced system efficiency and increased leakage flux density, which hinders the application and promotion of wireless power transmission technology. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of reduced system transmission efficiency and increased leakage flux density caused by the plane offset of the receiving coil in the current wireless power transmission system, and to provide a wireless power transmission system with an added three-pole relay coil. At the same time, through parameter design, the system has the characteristics of load-independent constant current output and zero phase difference between input voltage and input current.

[0004] In order to solve the above problems, the present invention proposes a wireless power transmission system with a three-pole relay coil added. A three-pole relay coil containing three sub-coils is used above the transmitting coil. When the receiving coil is offset, its mutual inductance with different relay coils changes differently. By designing the reactance of the relay coil, a larger current can flow through the relay coil with a larger mutual inductance with the receiving coil, and a relatively small current can flow through other relay coils, thereby reducing the loss caused by the parasitic resistance of the coil and reducing the leakage flux density around the charging area, thereby improving the system's anti-offset capability. At the same time, by designing the parameters of the reactance of the transmitting coil and the receiving coil, a load-independent constant current output and a zero phase difference between the input current and the input voltage are achieved, thereby ensuring the output stability and high power factor of the system.

[0005] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0006] A wireless power transmission system with a three-pole relay coil added, comprising a power source module, an inverter module, a transmission coil module, a rectifier module and a load; The power source module includes an ideal voltage source, which provides electric energy to the inverter module, the transmission coil module, the rectifier module and the load; When the ideal voltage source is powered on, the electric energy is converted into alternating current through the inverter module and input into the transmitting coil of the transmission coil module; in the transmission coil module, due to the electromagnetic coupling relationship between the transmitting coil, the three-pole relay coil and the receiving coil, the electric energy in the transmitting coil is transmitted to the receiving coil through the three-pole relay coil, and at the same time, part of the electric energy is directly transmitted from the transmitting coil to the receiving coil; the current intensity of the three sub-coils in the three-pole relay coil is positively correlated with the coupling strength between the sub-coils and the receiving coil; the alternating current of the receiving coil is converted into direct current through the rectifier module to supply energy to the load.

[0007] Further, the inverter module includes a first capacitor, a second capacitor, a first bridge arm and a second bridge arm; The transmission coil module includes an electromagnetically coupled transmitting coil, a three-pole relay coil and a receiving coil. The electric energy in the transmitting coil is transmitted to the receiving coil via the three-pole relay coil. The transmitting coil is equivalent to a series circuit including the transmitting coil internal resistance, the transmitting coil inductance and the transmitting coil compensation capacitor (or an external inductor). The three-pole relay coil is equivalent to three series circuits including the relay coil internal resistance, the relay coil inductance and the relay coil compensation capacitor (or an external inductor). The receiving coil is equivalent to a series circuit including the receiving coil internal resistance, the receiving coil inductance and the receiving coil resonant capacitor (or an external inductor). The rectifier module includes a first diode, a second diode, a third diode, a fourth diode and a filter capacitor; The first capacitor and the second capacitor of the inverter module I are connected in series, the first bridge arm and the second bridge arm are connected in series, and the capacitor series branch, the bridge arm series branch and the ideal voltage source are connected in parallel; wires are drawn between the first capacitor and the second capacitor of the inverter module I, and between the first bridge arm and the second bridge arm, and are connected to two ends of the transmitting coil in the transmission coil module; The first diode and the second diode of the rectifier module are connected in series, the third diode and the fourth diode are connected in series, the filter capacitor, the load and the first diode and the second diode connected in series, and the third diode and the fourth diode connected in series are connected in parallel; wires are led out between the first diode and the second diode, and between the third diode and the fourth diode, respectively, and connected to the two ends of the receiving coil in the transmission coil module.

[0008] Furthermore, the three-pole relay coil is a circular structure formed by stacking three sub-coils; In the three-pole relay coil, the circular structure is divided at a central angle of 120° to form three sub-coil placement areas; the three sub-coils are fan-shaped and have the same shape and area; the three sub-coils are placed in the divided sub-coil placement areas respectively and overlap each other to achieve magnetic decoupling between any two sub-coils; Since the positions of the three sub-coils in the plane are different, the electromagnetic coupling strengths of the three sub-coils and the receiving coil are also different; in the process of transmitting electric energy to the receiving coil via the three-pole relay coil, the sub-coil with high coupling strength with the receiving coil flows with a larger current and transmits more electric energy, thereby realizing directional following of the magnetic field of the transmitting coil when the position of the receiving coil changes.

[0009] Furthermore, the three sub-coils in the three-pole relay coil each independently form a closed loop and are not connected to other modules.

[0010] Furthermore, the load is of purely resistive nature.

[0011] Furthermore, the first bridge arm and the second bridge arm are both composed of a switch tube and an anti-parallel diode.

[0012] Furthermore, the input impedance of the wireless power transfer system is a real number to achieve zero phase difference between input voltage and input current, which is achieved by setting the following parameters: When the parasitic resistance of all coils is ignored, the reactance of the receiving coil in the transmission coil module satisfies the relationship: ; Among them, the reactance of the sub-coils of the three-pole relay coil is , , , the reactance of the receiving coil is , is an imaginary unit, is the angular frequency, satisfying , is the system operating frequency; , They are the first The self-inductance and compensation capacitance of each sub-coil, , , are the self-inductance and compensation capacitance of the receiving coil respectively; the mutual inductance of the three-pole relay coil and the receiving coil is , , , The first The mutual inductance between the sub-coil and the receiving coil is .

[0013] Furthermore, the output current has a load-independent constant current characteristic, which is achieved by setting the following parameters: When the parasitic resistance of all coils is ignored, the reactance of the transmitting coil satisfies the relationship: , where the reactance of the transmitting coil is , , are the self-inductance and compensation capacitance of the transmitting coil respectively; the mutual inductance of the transmitting coil and the three-pole relay coil is , , , The first The mutual inductance between the sub-coil and the transmitting coil is .

[0014] Furthermore, if among all the coils in the transmission coil module, there is a coil whose calculated value of compensation capacitance is negative, the compensation capacitance of the coil is replaced by an external inductor, and the external inductor is connected in series with the coil, and according to Determine the value of the added inductor.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: In the present invention, the reactance of the three-pole relay coil affects the current distribution of the system. By setting the reactance value of the relay coil, the overall efficiency of the system can be optimized within the offset range of the receiving coil.

[0016] The structural design and reactance value design of the three-pole relay coil improve the anti-offset capability of the wireless power transmission system. The sub-coils of the three-pole relay coil are distributed at different positions in the two-dimensional plane. Therefore, when the receiving coil is offset in the plane, the mutual inductance between it and the sub-coils of the three-pole relay coil has different change trends. The reactance value of the relay coil is designed with the goal of optimizing the overall efficiency of the system within the offset range of the receiving coil, so that the current of the sub-coil of the three-pole relay coil is adaptively adjusted according to the mutual inductance with the receiving coil. The sub-relay coil with a larger mutual inductance with the receiving coil flows through a larger current, and the other coils flow through a relatively small current, thereby improving the system efficiency and reducing the leakage flux density in the charging area. At the same time, the system has the characteristics of load-independent constant current output and zero phase difference between input current and input voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1a and Figure 1b 2 are different views of the coil arrangement structure in an embodiment of the present invention; Figure 2 is an equivalent circuit diagram of a wireless power transmission system with a three-pole relay coil added in an embodiment of the present invention; Figure 3a , Figure 3b is an equivalent circuit diagram of a system port in an embodiment of the present invention; Figure 4 A simplified circuit diagram of a wireless power transmission system with a three-pole relay coil added in an embodiment of the present invention; Figure 5a , Figure 5b A diagram showing the change of the three-pole relay coil and its mutual inductance and the effective value of the relay coil current within the offset range of the receiving coil in an embodiment of the present invention; Figure 6 A diagram showing a change in system power factor within a receiving coil offset range in an embodiment of the present invention; Figure 7 A diagram showing a change in DC output current when the load changes in an embodiment of the present invention; Figure 8a , Figure 8b It is a simulation diagram of the current waveform on the transmitting side of the system and the two-coil system of the present invention when the coils in the embodiment of the present invention are aligned; Figure 9a , Figure 9b It is a simulation diagram of the current waveform on the transmitting side of the system and the two-coil system of the present invention when the coil is extremely offset in the embodiment of the present invention; Fig.10 This is a diagram comparing the efficiency of a wireless power transmission system with a three-pole relay coil added and a two-coil system in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The specific implementation of the invention is further described below in conjunction with the accompanying drawings, but the implementation and protection of the invention are not limited thereto.

[0019] Example: A wireless power transmission system with a three-pole relay coil added, such as Figure 2 As shown, it includes a power source module, an inverter module I, a transmission coil module II, a rectifier module III and a load; The power source module includes an ideal voltage source , providing power to the inverter module I, the transmission coil module II, the rectifier module III and the load; When the ideal voltage source After power is turned on, the electric energy is converted into alternating current by the inverter module I and input into the transmitting coil of the transmission coil module II; Figure 1a , Figure 1bAs shown, in the transmission coil module II, due to the electromagnetic coupling relationship between the transmitting coil 2, the three-pole relay coil 3 and the receiving coil 1, the electric energy in the transmitting coil 2 is transmitted to the receiving coil 1 via the three-pole relay coil 3, and at the same time, part of the electric energy is directly transmitted from the transmitting coil 2 to the receiving coil 1; the current intensity of the three sub-coils in the three-pole relay coil is positively correlated with the coupling strength between the sub-coils and the receiving coil; the AC power of the receiving coil is converted into DC power by the rectifier module III to supply energy to the load.

[0020] In this embodiment, the inverter module I includes a first capacitor , the second capacitor , the first bridge arm and the second bridge arm ; like Figure 2 As shown, the transmission coil module II includes an electromagnetically coupled transmitting coil, a three-pole relay coil and a receiving coil. The electric energy in the transmitting coil is transmitted to the receiving coil via the three-pole relay coil; the transmitting coil is equivalent to the transmitting coil internal resistance , Transmitter coil inductance and transmitter coil compensation capacitor (or external inductor) series circuit, the three-pole relay coil is equivalent to three relay coils including the internal resistance , Relay coil inductance and relay coil compensation capacitor (or external inductor) series circuit, the receiving coil is equivalent to the receiving coil internal resistance , receiving coil inductance and the receiving coil resonant capacitor (or an external inductor) series circuit; The rectifier module III includes a first diode , the second diode , the third diode , the fourth diode and filter capacitors ; The first capacitor of inverter module I and the second capacitor Series, first bridge arm and the second bridge arm Series connection, capacitor series connection branch, bridge arm series connection branch and ideal voltage source Parallel connection; the first capacitor of inverter module I , the second capacitor Between, and the first bridge arm and the second bridge arm Lead wires are respectively led out between the two ends of the transmitting coil in the transmission coil module II; The first diode of rectifier module III and the second diode The third diode in series and the fourth diode Series, filter capacitor ,load and the first diode in series , the second diode , and a third diode in series , the fourth diode Parallel connection; first diode , the second diode between, and the third diode , the fourth diode Lead wires are respectively connected to the two ends of the receiving coil in the transmission coil module II.

[0021] In this embodiment, the three-pole relay coil is a circular structure formed by stacking three sub-coils, which are stacked above the transmitting coil; like Figure 1b As shown, in the three-pole relay coil, the circular structure is divided at a central angle of 120° to form three sub-coil placement areas; the first sub-coil 301, the second sub-coil 302 and the third sub-coil 303 are fan-shaped, and have the same shape and area; the first sub-coil 301, the second sub-coil 302 and the third sub-coil 303 are respectively placed in the divided sub-coil placement areas, and are placed overlapping each other to achieve magnetic decoupling between any two sub-coils; Since the positions of the three sub-coils in the plane are different, the electromagnetic coupling strengths of the three sub-coils and the receiving coil are also different; in the process of transmitting electric energy to the receiving coil via the three-pole relay coil, the sub-coil with high coupling strength with the receiving coil flows with a larger current and transmits more electric energy, thereby realizing directional following of the magnetic field of the transmitting coil when the position of the receiving coil changes.

[0022] Furthermore, the three sub-coils in the three-pole relay coil each form a closed loop independently and are not connected to other modules. The load is purely resistive. The first bridge arm and the second bridge arm They are all composed of a switching tube and an anti-parallel diode.

[0023] like Figure 3a , Figure 3b As shown, the output port of the inverter module is 11', and the input port of the rectifier module is 22'. The input terminal of the transmission coil module is connected to port 11', and the output terminal is connected to port 22'. Using the fundamental wave analysis method, the DC input voltage With inverter output voltage Satisfy the relationship (effective value, RMS), rectified input voltage With load DC output voltage across the Satisfy the relationship (RMS), the network on the right side of port 22' is equivalent to a resistor , satisfying the following formula: , is the output power. Considering the above equivalent substitution, we get Figure 4 Simplified circuit diagram of the system.

[0024] Since the three sub-coils in the three-pole relay coil have the same structure, it is assumed that their reactances are equal and are expressed as , the mutual inductance between them and the transmitting coil is also approximately equal, expressed as The parasitic resistance of the coil is small and is ignored in the derivation of the equation. When the receiving coil is aligned, according to the requirements of zero input phase angle and constant current output, the reactance of the receiving coil and the transmitting coil respectively satisfy the relationship , When the receiving coil is Figure 1b When the XY plane is offset, the mutual inductance between the transmitting coil and the sub-coil does not change, so the constant current output condition can still be met. The mutual inductance between the three-pole relay coil and the receiving coil changes due to the offset of the receiving coil, some mutual inductance increases, some decreases, and the zero input phase angle condition cannot be fully met, and there is a small range of deviation.

[0025] When the receiving coil is aligned, the current of the sub-coil of the three-pole relay coil is ,in , so the relative magnitudes of the sub-coil currents are consistent with the relative magnitudes of the mutual inductances between them and the receiving coil. Figure 1b When the XY plane is offset in a certain direction, the sub-coil closer to it and with greater mutual inductance flows with a larger current, and vice versa, a relatively small current flows, thereby achieving directional following of the magnetic field and reducing coil loss. At the same time, the current of the transmitting coil satisfies , it can be seen that the reactance of the sub-coil It is positively correlated with the current amplitude of the transmitting coil and negatively correlated with the current amplitude of the sub-coil. The system efficiency is expressed as , so for a specific output current, as As the value of reactance increases, the system efficiency increases first and then decreases. There is a value of reactance that maximizes the system efficiency.

[0026] Then, consider the effect of the change in mutual inductance between the three-pole relay coil and the receiving coil caused by the offset of the receiving coil on the efficiency. After taking the derivative of the current expression with respect to the offset distance, it can be seen that when When a smaller value is taken, the decrease in system efficiency caused by the offset of the receiving coil can be reduced by reducing the increase in the current of the transmitting coil and reducing the increase in the current of the sub-coil with a lower coupling coefficient with the receiving coil. The increase in system efficiency when the receiving coil is aligned First rise and then fall, and the system efficiency when the coil is offset is about Therefore, the value of the sub-coil reactance should be determined with the goal of optimizing the overall system efficiency within the design range.

[0027] In this embodiment, the input impedance of the wireless power transmission system is is a real number to achieve zero phase difference between input voltage and input current, which is achieved by setting the following parameters: When the parasitic resistance of all coils is ignored, the reactance of the receiving coil in the transmission coil module II satisfies the relationship: ; Among them, the reactance of the sub-coils of the three-pole relay coil is , , , the reactance of the receiving coil is , is an imaginary unit, is the angular frequency, satisfying , is the system operating frequency; , They are the first The self-inductance and compensation capacitance of each sub-coil, , , are the self-inductance and compensation capacitance of the receiving coil respectively; the mutual inductance of the three-pole relay coil and the receiving coil is , , , The first The mutual inductance between the sub-coil and the receiving coil is .

[0028] In this embodiment, the output current has a load-independent constant current characteristic, which is achieved by setting the following parameters: When the parasitic resistance of all coils is ignored, the reactance of the transmitting coil satisfies the relationship: , where the reactance of the transmitting coil is , , are the self-inductance and compensation capacitance of the transmitting coil respectively; the mutual inductance of the transmitting coil and the three-pole relay coil is , , , The first The mutual inductance between the sub-coil and the transmitting coil is .

[0029] If the calculated value of the compensation capacitance of a coil among all the coils in the transmission coil module II is negative, the compensation capacitance of the coil is replaced by an external inductor. , the external inductor In series with the coil, and according to Determine the external inductor The value of .

[0030] In one embodiment, at a known output power , output current , Operating frequency , Transmitter coil inductance and resistor , three-pole relay coil inductance and resistor ( ), receiving coil inductance and resistor , the mutual inductance of the transmitting coil and the three-pole relay coil ( ), the mutual inductance of the transmitting coil and the receiving coil ( Indicates that the receiving coil is Figure 1b The position on the XY plane, , in meters), the mutual inductance of the receiving coil and the three-pole relay coil ( ) under the conditions: (1) First, according to (RMS), Calculate the equivalent load and AC side output current.

[0031] (2) Based on the mutual inductance data when the receiving coil is aligned, the initial value , step length greater than 0 Search for the best value Each The values ​​are based on the constant current output conditions. and zero input phase angle condition Sure and Then the system efficiency is calculated based on the circuit equation Since system efficiency increases with The increase of first rises and then falls, so the search is stopped after the maximum efficiency is achieved, and the .

[0032] (3) Considering the offset of the receiving coil, the initial value , step size less than 0 Search for the best value Each The value is determined according to the constant current output condition and zero input phase angle condition. and With the value of The system efficiency when the coil is aligned is reduced. The system efficiency at the extreme deflection of the coil increases first and then decreases. ( , Indicates the different offset positions of the receiving coil, is the weight, which indicates the importance of the system efficiency at this offset position) to obtain the overall system efficiency. The decline, First increase, then decrease, so stop searching after achieving the maximum comprehensive efficiency and record and , ,Depend on Calculate the value of the compensation capacitor. If the result is negative, Calculate the value of the added inductor.

[0033] In one embodiment, according to the above design steps, a wireless power transmission system example with a three-pole relay coil is given and compared with a two-coil system. The system parameters are shown in Table 1. Known: Output power , DC output current , operating frequency , the self-inductance of the transmitting coil ,resistance , the self-inductance of the three-pole relay coil ,resistance , the self-inductance of the receiving coil ,resistance Since the three-pole relay coil has a certain symmetry, without loss of generality, we select Figure 1b The OX1 and OX2 directions are used as the receiving coil offset directions for testing. Within the 60mm offset range, the mutual inductance value is obtained using simulation software, and the relationship between the coil mutual inductance and the receiving coil offset is obtained by curve fitting, as shown in Table 2. Other parameter values ​​can be designed according to the following steps: a. Current effective value (RMS) , equivalent resistance .

[0034] b. When the coil is aligned, and Under the conditions of The initial value and step size greater than 0 Searching for the coil parameters that optimize the system efficiency, the result is .

[0035] c. The receiving coil Figure 1b When the OX1 and OX2 directions are offset, and Under the conditions of The initial value and step size less than 0 , search for equivalent efficiency ( , taking 50 sets of mutual inductance data in the OX1 and OX2 directions respectively) the coil parameters with the highest value are: , , ,according to (or ) Calculate the compensation capacitance or inductance of the coil as , , , .

[0036] Table 1 System coil parameters

[0037] Table 2 System coil mutual inductance fitting values

[0038] Based on the above parameters, the relationship between the mutual inductance between the three-pole relay coil and the receiving coil and the sub-coil current (RMS) is simulated and verified. Figure 5a and Figure 5b The receiving coil is Figure 1b When moving in the OX1 direction and the OX2 direction, the mutual inductance of the three-pole relay coil and the receiving coil and the effective value of the sub-coil current, the relative size of the current between the sub-coils is consistent with the relative size of the mutual inductance between them and the receiving coil, thereby realizing adaptive current distribution.

[0039] Figure 6 The power factor of the system is shown when the receiving coil moves in the OX1 direction and the OX2 direction. Even when the coil is offset, the power factor of the system remains stable at around 0.89. The deviation between the simulation results and the theoretical analysis mainly comes from the deviation of the fundamental wave approximation method used in the analysis process. Figure 7 The figure shows the change of output current when the load resistance changes under the condition that the receiving coil is aligned and offset by 60mm in the OX1 direction. It can be seen from the figure that the load current changes by less than 4% within the range of ±25% load resistance change.

[0040] The wireless power transmission system with the addition of a three-pole relay coil is compared with a two-coil system (the outer diameter and number of turns of the transmitting coil are the same as those of the three-pole relay coil, and the radius and number of turns of the receiving coil remain the same). Figure 8a and Figure 8b They are respectively the simulation waveforms of the transmitting-side current of the system with the three-pole relay coil added and the two-coil system when the coils are aligned. At this time, the current amplitudes of the three-pole relay coil and the transmitting coil of the two-coil system are close. Figure 9a and Figure 9b The following are the simulated waveforms of the transmitting side current of the system with a three-pole relay coil added and the two-coil system when the receiving coil is offset by 60mm. The effective value of the transmitting coil current of the two-coil system is about 15.2A, while the effective values ​​of the current of the three-pole relay coil are 15.7A, 12A, and 12A respectively. Therefore, it can be seen that the system with a three-pole relay coil realizes the adaptive distribution of coil current through the design of the coil structure. The relay coil with greater mutual inductance with the receiving coil flows through a larger current, thereby significantly reducing the current of the relay coil with weaker coupling with the receiving coil, and improving the system efficiency. The system efficiency comparison results are shown in Fig.10 A vertical test plane was placed 0.2m away from the center line of the system in the opposite direction of the receiving coil offset, and the leakage flux density of the system of the present invention and the two-coil system under this current distribution was simulated and compared. The results show that the maximum leakage flux density of the system of the present invention is about 112uT, and the maximum leakage flux density of the two-coil system is 120uT, and the average density of the former is smaller than that of the latter.

Claims

1. A wireless power transmission system with a three-pole relay coil added, It is characterized in that It includes a power source module, an inverter module (I), a transmission coil module (II), a rectifier module (III) and a load; The power source module includes an ideal voltage source ( ), providing power to the inverter module (I), the transmission coil module (II), the rectifier module (III) and the load; When the ideal voltage source ( ) is powered on, the electric energy is converted into alternating current by the inverter module (I) and input into the transmitting coil of the transmission coil module (II); in the transmission coil module (II), the electric energy in the transmitting coil is transmitted to the receiving coil via the three-pole relay coil, and at the same time, part of the electric energy is directly transmitted from the transmitting coil to the receiving coil; the alternating current of the receiving coil is converted into direct current by the rectifier module (III) to supply energy to the load.

2. A wireless power transmission system with a three-pole relay coil added according to claim 1, It is characterized in that The inverter module (I) includes a first capacitor ( )、Second capacitor( )、First bridge arm( ) and the second bridge arm ( ); The transmission coil module (II) includes an electromagnetically coupled transmitting coil, a three-pole relay coil and a receiving coil, and the electric energy in the transmitting coil is transmitted to the receiving coil via the three-pole relay coil; The rectifier module (III) includes a first diode ( )、The second diode( )、The third diode( )、The fourth diode( ) and filter capacitors ( ); The first capacitor of the inverter module (I) ) and the second capacitor ( ) in series, the first bridge arm ( ) and the second bridge arm ( ) in series, capacitor series branch, bridge arm series branch and ideal voltage source ( )in parallel; The first capacitor of the inverter module (I) )、Second capacitor( ) and the first bridge arm ( ) and the second bridge arm ( ) are connected with two ends of the transmitting coil in the transmission coil module (II); The first diode of the rectifier module (III) ) and the second diode ( ) in series, the third diode ( ) and the fourth diode ( ) in series, filter capacitor ( ),load( ) and the first diode in series ( )、The second diode( ), and a third diode in series ( )、The fourth diode( ) in parallel; the first diode ( )、The second diode( ) between the diodes, and the third diode ( )、The fourth diode( ), and lead wires are connected to the two ends of the receiving coil in the transmission coil module (II).

3. A wireless power transmission system with a three-pole relay coil added according to claim 2, It is characterized in that The three-pole relay coil is a circular structure formed by stacking three sub-coils; In the three-pole relay coil, the circular structure is divided at a central angle of 120° to form three sub-coil placement areas; The three sub-coils are fan-shaped and have the same shape and area. The three sub-coils are placed in the divided sub-coil placement areas respectively and overlap each other to achieve magnetic decoupling between any two sub-coils.

4. A wireless power transmission system with a three-pole relay coil added according to claim 3, It is characterized in that The three sub-coils in the three-pole relay coil each form a closed loop independently and are not connected to other modules.

5. A wireless power transmission system with a three-pole relay coil added according to claim 1, It is characterized in that The load is purely resistive.

6. A wireless power transmission system with a three-pole relay coil added according to claim 2, It is characterized in that The first bridge arm ( ) and the second bridge arm ( ) are both composed of a switching tube and an anti-parallel diode.

7. A wireless power transmission system with a three-pole relay coil added according to claim 2, It is characterized in that When the parasitic resistance of all coils is ignored, the reactance of the receiving coil in the transmission coil module (II) satisfies the relationship: ; Among them, the reactance of the sub-coils of the three-pole relay coil is , , , the reactance of the receiving coil is , is an imaginary unit, is the angular frequency, satisfying , is the system operating frequency; , They are the first The self-inductance and compensation capacitance of each sub-coil, , , are the self-inductance and compensation capacitance of the receiving coil respectively.

8. A wireless power transmission system with a three-pole relay coil added according to claim 7, It is characterized in that The mutual inductances of the three-pole relay coil and the receiving coil are , , , The first The mutual inductance between the sub-coil and the receiving coil is .

9. A wireless power transmission system with a three-pole relay coil added according to claim 2, It is characterized in that When the parasitic resistance of all coils is ignored, the reactance of the transmitting coil satisfies the relationship: , where the reactance of the transmitting coil is , , are the self-inductance and compensation capacitance of the transmitting coil respectively; the mutual inductance of the transmitting coil and the three-pole relay coil is , , , The first The mutual inductance between the sub-coil and the transmitting coil is .

10. A wireless power transmission system with a three-pole relay coil added according to any one of claims 7 to 9, It is characterized in that If among all the coils in the transmission coil module (II), there is a coil whose calculated compensation capacitance is negative, the compensation capacitance of the coil is replaced by an external inductor ( ), the external inductor ( ) in series with the coil and according to Determine the external inductor ( ) value.

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