Pulse density modulation sequence design method and device for wireless power transmission

Abstract

The invention discloses a pulse density modulation sequence design method and device for wireless power transmission, and relates to the technical field of wireless power transmission, and the method comprises the steps: obtaining a modulation sequence period, determining a modulation step length based on the modulation sequence period, and setting an initial sequence for modulation density based on the modulation step length; extracting compensation topology, and calculating the minimum harmonic distortion rate of output current of the compensation topology when each modulation sequence is adopted under the same modulation density by taking the initial sequence as a starting point; and sorting the minimum harmonic distortion rates of all the output currents, and taking a sequence corresponding to a minimum value in the minimum harmonic distortion rates of the output currents as a modulation sequence under the modulation density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless power transmission, in particular to a pulse density modulation sequence design method and device for wireless power transmission. BACKGROUND

[0002] Magnetic coupling wireless power transmission technology is a relatively new power supply technology, which has many application scenarios in reality, such as consumer electronics products such as smart phones and smart watches, and daily travel tools such as electric vehicles and electric bicycles. Compared with traditional wired power supply technology, magnetic coupling wireless power transmission technology realizes energy transmission through a magnetic field, so it does not need to rely on cables, and has incomparable advantages over traditional wired power supply in terms of cost, convenience, safety, reliability, etc.

[0003] Pulse density modulation (PDM) is a technology that realizes power regulation by changing the density of pulses, and the density is represented by modulation density D in PDM. In a magnetic coupling wireless power transmission system, PDM is generally used for rectification at the receiving end. At present, there are mainly two methods for generating PDM modulated waves, one is based on a Delta-Sigma modulator, which only needs to take the modulation density as input and generates a PDM modulated wave using the internal inherent modulation rule, and the other is to artificially design a modulation sequence, although the accuracy and freedom of modulation can be higher, but more parameters need to be considered when designing, and there is still a lack of unified representation method. In addition, when the receiving end adopts PDM modulation for rectification, due to the modulation characteristics of PDM, the output voltage of the compensation system contains various frequency subharmonics (i.e. non-resonant frequency integer multiple harmonics) in addition to the high-order harmonics corresponding to the resonant frequency. The injection of these harmonics not only causes the compensation network current to oscillate, thereby reducing the reliability of system operation, but also increases system loss and reduces transmission efficiency. SUMMARY

[0004] To solve the problems mentioned in the background, the purpose of the present application is to provide a pulse density modulation sequence design method and device for wireless power transmission.

[0005] In the first aspect, the purpose of the present application can be achieved by the following technical solution: a pulse density modulation sequence design method for wireless power transmission, the method comprising the following steps:

[0006] Obtaining a modulation sequence period, determining a modulation step length based on the modulation sequence period, and setting an initial sequence for the modulation density based on the modulation step length;

[0007] Extracting a compensation topology, taking the initial sequence as a starting point, and calculating the minimum harmonic distortion rate of the output current of the compensation topology when each modulation sequence is used under the same modulation density;

[0008] The minimum harmonic distortion rates of all output currents are sorted, and the sequence corresponding to the minimum value in the minimum harmonic distortion rate of the output current is taken as the modulation sequence under the modulation density.

[0009] With reference to the first aspect, in some implementations of the first aspect, the method further includes that the parameters of the wireless power transmission system include:

[0010] One DC source V1, the primary side inverter composed of four field effect transistors Q 1 / 2 / 3 / 4 and the same four field effect transistors Q 5 / 6 / 7 / 8 composed of the secondary side rectifier, the double-sided LCC compensation topology, the DC filter capacitor C d , the load resistor R L , wherein R L , the double-sided LCC compensation topology is composed of a compensation inductor L 1f / 2f and its internal resistance R 1f / 2f , a coupling coil inductance L 1 / 2 and its internal resistance R 1 / 2 , a series compensation capacitor C 1 / 2 and its parasitic resistance R c1 / c2 , a parallel compensation capacitor C 1f / 2f and its parasitic resistance R c1f / c2f , R c1 , R1 are combined as R t , R c2 , R2 are combined as R r , i 1 / 2 / 3 / 4 is the compensation network current, and the working frequency of the primary side inverter is the resonance frequency f1, and the corresponding resonance period is t1=1 / f1.

[0011] With reference to the first aspect, in some implementations of the first aspect, the method further includes that the parameters of the wireless power transmission system satisfy the following formula condition:

[0012]

[0013] In formula (1), ω1 is the resonance angular frequency, and ω1=2πf1 in relation to f1.

[0014] With reference to the first aspect, in some implementations of the first aspect, the method further includes that the circuit of the double-sided LCC compensation topology is decomposed into two subsystems: subsystem 1, subsystem 2, and the subsystem m is only acted on by the voltage U m[n] , I mk[n] , wherein m=1 / 2, and k=1 / 2 / 3 / 4 is the compensation network current under the action of U m[n] , Z mk[n] is the input impedance of each stage of the compensation network, and Z ref1 / ref2The calculation formulas of the secondary side reflection impedance and the primary side reflection impedance are shown in formulas (2) and (3) respectively, and on this basis, I mk[n] The calculation method is shown in formula (4):

[0015]

[0016] In addition, I mk[n] And I 1[n] / 2[n] / 3[n] / 4[n] Satisfy the following relationship:

[0017]

[0018] In formulas (2), (3), and (4), ω [n] Indicates the angular frequency corresponding to the n-th harmonic phasor.

[0019] In combination with the first aspect, in some implementations of the first aspect, the method further comprises: the secondary side of the wireless power transmission system adopts PDM modulation, for the PDM modulation wave, on the basis of the modulation density D, the duty cycle T is defined, when PDM modulation is adopted, according to the modulation characteristics of PDM, the compensation of the network output voltage u2 can be divided into two stages: energy injection stage and free oscillation stage, in the energy injection stage, Q5, Q8 or Q6, Q7 in the rectifier are turned on at the same time, the primary side energy is transmitted to the load through the inverter, the compensation topology and the rectifier in turn, due to the clamping of the DC filter capacitor, u2 has positive and negative polarity in the energy injection stage, the polarity is related to i4, when i4 is positive, the polarity is negative, and vice versa, the polarity is positive; and in the free oscillation stage, Q5, Q7 or Q6, Q8 are turned on at the same time, and the load resistance is only the DC filter capacitor C d Power supply.

[0020] In combination with the first aspect, in some implementations of the first aspect, the method further comprises: the modulation sequence takes one non-zero half wave as the starting half wave of one PDM duty cycle, and defines it as the reference half wave, the reference half wave also has positive and negative polarity, and the offset step number Indicates the number of half wave periods t1 / 2 of the reference half wave ahead of the remaining half waves, for the half wave with an offset step number of The Fourier decomposition result of the half wave is shown in formulas (6) and (7);

[0021] Based on the superposition theorem, the amplitude and phase of any harmonic of any modulation sequence are obtained, but the size of the amplitude depends on V2, and V2 also depends on U 1[n] , U 2[n] , V2 is taken as an unknown quantity, and the amplitude and phase of I 24[n] in subsystem 2 are calculated first according to formula (4), and the amplitude and phase of I 14[n]The amplitude and phase of the output current of the compensation network in the original system are obtained by using phasor addition according to formula (5), the size of V2 is calculated by using formula (8) according to the principle of power conservation, and then the amplitude of I 4[n]

[0022]

[0023] In combination with the first aspect, in some implementations of the first aspect, the method further comprises: the minimum harmonic distortion rate of the output current is calculated by using the current total harmonic distortion rate formula shown in formula (9) under any modulation sequence, wherein, I base represents the amplitude of the current component corresponding to the resonant frequency, I h represents the harmonic current amplitude other than the resonant frequency;

[0024]

[0025] On the basis of knowing the PDM working period K·t1 / 2, the modulation step is 1 / K, so the modulation density can be x / K, wherein x=1, 2, 3,..., K, for each modulation density, the harmonic distortion rate of all modulation sequences under the modulation density is calculated, and the sequence with the minimum harmonic distortion rate is taken as the modulation sequence corresponding to the modulation density.

[0026] In a second aspect, to achieve the above object, the application discloses a pulse density modulation sequence design device for wireless power transmission, comprising:

[0027] A sequence setting module is configured to obtain a modulation sequence period, determine a modulation step based on the modulation sequence period, and set an initial sequence for the modulation density based on the modulation step.

[0028] A compensation module is configured to extract a compensation topology, and calculate the minimum harmonic distortion rate of the output current of the compensation topology under each modulation sequence at the same modulation density, starting from the initial sequence.

[0029] A sequence design module is configured to sort all the minimum harmonic distortion rates of the output current, and take the sequence corresponding to the minimum value in the minimum harmonic distortion rate of the output current as the modulation sequence under the modulation density.

[0030] In another aspect of the application, to achieve the above object, a terminal device is disclosed, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, the memory stores a computer program capable of running on the processor, and when the processor loads and executes the computer program, the pulse density modulation sequence design method for wireless power transmission as described above is adopted.

[0031] ​In still another aspect of the present application, in order to achieve the above object, a computer readable storage medium is disclosed, wherein the computer readable storage medium stores a computer program, and the computer program is loaded and executed by a processor, and the computer program adopts the pulse density modulation sequence design method for wireless power transmission as described above.

[0032] Advantages of the present application:

[0033] The present application can significantly reduce the output current harmonics of the compensation network, thereby reducing the ripple size, only controlling the secondary side, and using the zero-crossing point of the fundamental component of the compensation network output current as the commutation reference for the control signal of the secondary side, and using the superposition theorem and the Fourier decomposition combination method to realize the fast calculation of the harmonic voltage phasor. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0035] Figure 1 is a schematic diagram of the method of the present application;

[0036] Figure 2 is a schematic diagram of the magnetic coupling wireless power transmission system based on the double-sided LCC topology of the present application;

[0037] Figure 3 is a simplified equivalent circuit schematic diagram of the double-sided LCC topology of the present application;

[0038] Figure 4 is a decomposition schematic diagram of the simplified equivalent circuit of the double-sided LCC topology of the present application;

[0039] Figure 5 is a schematic diagram of the PDM modulation characteristics of the present application;

[0040] Figure 6 is a schematic diagram of the device structure of the present application.

[0041] Figure 7 is an implementation effect diagram of the present application. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort are within the scope of protection of the present application.

[0043] Embodiment one:

[0044] As Figure 1 shown, the pulse density modulation sequence design method for wireless power transmission, the method comprises the following steps:

[0045] S101: Obtain a modulation sequence period, determine a modulation step length based on the modulation sequence period, and set an initial sequence for the modulation density based on the modulation step length;

[0046] The parameters of the wireless power transmission system applied in the application include:

[0047] A DC source V1, a primary side inverter composed of four field effect transistors Q 1 / 2 / 3 / 4 , and a same four field effect transistors Q 5 / 6 / 7 / 8 composed of a secondary side rectifier, a double-sided LCC compensation topology, a DC filter capacitor C d , and a load resistor R L , wherein R L has a voltage V2 across it, the double-sided LCC compensation topology is composed of a compensation inductor L 1f / 2f , an internal resistance R 1f / 2f of the compensation inductor L 1 / 2 , an internal resistance R 1 / 2 of the compensation inductor L 1 / 2 , a series compensation capacitor C c1 / c2 and a parasitic resistance R 1f / 2f of the series compensation capacitor C c1f / c2f , a parallel compensation capacitor C c1 and a parasitic resistance R t of the parallel compensation capacitor C c2 , R r , R2 are combined into R 1 / 2 / 3 / 4 , i m[n] is the compensation network current, the working frequency of the primary side inverter is the resonance frequency f1, and the corresponding resonance period is t1=1 / f1.

[0048] The parameters of the wireless power transmission system satisfy the following formula conditions:

[0049]

[0050] In formula (1), ω1 is the resonance angular frequency, and ω1=2πf1 in relation to f1.

[0051] The circuit of the double-sided LCC compensation topology is decomposed into two subsystems: subsystem 1 and subsystem 2, and subsystem m is only affected by the voltage U mk[n] , I m[n] , wherein m=1 / 2, k=1 / 2 / 3 / 4 is the compensation network current under the action of U mk[n]To compensate for the input impedance at each level of the network, Z ref1 / ref2 The reflected impedance of the secondary side and the reflected impedance of the primary side are calculated respectively, and the calculation formulas are shown in equations (2) and (3) respectively. On this basis, I mk[n] The calculation method is shown in equation (4):

[0052]

[0053]

[0054] In addition, I mk[n] And I 1[n] / 2[n] / 3[n] / 4[n] Satisfy the following relationship:

[0055]

[0056] In equations (2), (3), and (4), ω [n] Indicates the angular frequency corresponding to the n-th harmonic phasor.

[0057] S102: Extract the compensation topology, take the initial sequence as the starting point, and calculate the minimum harmonic distortion rate of the compensation topology output current when each modulation sequence is used under the same modulation density;

[0058] S103: Sort the minimum harmonic distortion rates of all output currents, and take the sequence corresponding to the minimum value in the minimum harmonic distortion rate of the output current as the modulation sequence under the modulation density.

[0059] Further, in Figure 2 The secondary side of the system shown in uses PDM modulation. For the PDM modulation wave, the working period T is defined on the basis of the modulation density D, and the period is equal to K / 2 resonance periods t1, as shown in Figure 5 When PDM modulation is used, according to the modulation characteristics of PDM, the compensation network output voltage u2 can be divided into two stages: energy injection stage and free oscillation stage. In the energy injection stage, Figure 2 Q5, Q8 or Q6, Q7 in the rectifier are simultaneously turned on, and the primary side energy is transmitted to the load through the inverter, the compensation topology, and the rectifier in turn. Due to the clamping of the DC filter capacitor, u2 has positive and negative polarity in the energy injection stage, and the specific polarity depends on i4. According to Figure 2 As shown in i4 reference direction, when i4 is positive, the polarity is negative, and vice versa, the polarity is positive; and in the free oscillation stage, Q5, Q7 or Q6, Q8 are simultaneously turned on, and the load resistance is only provided by the DC filter capacitor C d Power supply.

[0060] Further, for any modulation sequence (modulation density is not zero), such as Figure 5As shown, one non-zero half-wave is taken as the starting half-wave of a PDM working period and defined as a reference half-wave, which also has positive and negative polarities. Then, the offset step number is defined The number of half-wave periods (t1 / 2) in which the reference half-wave is ahead of the remaining half-waves is indicated. At this time, for a half-wave with an offset step number of in a working period, the Fourier decomposition result is shown in equations (6) and (7). Based on the superposition theorem, the amplitude and phase of any harmonic of any modulation sequence can be calculated, but the amplitude depends on V2, and V2 depends on U 1[n] , U 2[n] at the same time, so it cannot be directly obtained. Therefore, V2 is taken as an unknown quantity, and the amplitude and phase of I 24[n] in subsystem 2 and the amplitude and phase of I 14[n] in subsystem 1 are calculated based on equation (4). According to equation (5), the n-th harmonic phasor of the compensation network output current in the original system is obtained by using phasor addition. Without considering the on-resistance of the switch tube and the parasitic resistance of the DC filter capacitor, the size of V2 is calculated based on the power conservation principle using equation (8), and the amplitude of I 4[n] is obtained.

[0061]

[0062] Further, the harmonic distortion rate of i4 under any modulation sequence is calculated using the current total harmonic distortion rate formula shown in equation (9), where I base represents the amplitude of the current component corresponding to the resonant frequency, and I h represents the harmonic current amplitude other than the resonant frequency.

[0063]

[0064] Further, based on the above calculation method for the harmonic distortion rate of the compensation network output current under any modulation sequence, the design of the modulation sequence is started. First, based on the known PDM working period K·t1 / 2, the modulation step is taken as 1 / K, so the modulation density can be taken as x / K (X=1, 2, 3,..., K). For each modulation density, the harmonic distortion rate of all modulation sequences at this density is calculated, and the sequence with the minimum harmonic distortion rate is taken as the modulation sequence corresponding to this modulation density.

[0065] Specifically, the following embodiments are used to further illustrate the present application:

[0066] The method is suitable for any compensation topology, but the compensation network parameters need to be known in advance, including the self-inductance and internal resistance of the coupling coil, the capacitance value and parasitic resistance of the compensation capacitor, and the inductance value and internal resistance of the compensation inductor. When calculating the harmonic distortion rate of the output current of the compensation topology, the method needs to calculate the magnitude and phase of each harmonic voltage contained in the PDM modulation wave of different sequences. To solve the problem of large number of modulation sequences under the same modulation density and difficult to calculate, the method uses the combination of superposition theorem and Fourier decomposition to realize the fast calculation of harmonic voltage phasor.

[0067] Embodiment two: in order to achieve the above purpose, as shown in the embodiment one, based on the basis of the embodiment one, the application discloses a pulse density modulation sequence design device for wireless power transmission, comprising: Figure 6 The sequence setting module 11 is used for obtaining a modulation sequence period, determining a modulation step length based on the modulation sequence period, and setting an initial sequence for the modulation density based on the modulation step length.

[0068] The compensation module 12 is used for extracting a compensation topology, taking the initial sequence as a starting point, and calculating the minimum harmonic distortion rate of the output current of the compensation topology under the same modulation density when using each modulation sequence.

[0069] The sequence design module 13 is used for sorting all the minimum harmonic distortion rates of the output current, and taking the sequence corresponding to the minimum value in the minimum harmonic distortion rate of the output current as the modulation sequence under the modulation density.

[0070] Based on the same inventive concept, the application further provides a computer device, which comprises one or more processors and a memory for storing one or more computer programs; the program comprises program instructions, and the processor is used for executing the program instructions stored in the memory. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are used for implementing one or more instructions, and are specifically used for loading and executing one or more instructions in the computer storage medium to realize the above method.

[0071]

[0072] ​It should be further noted that based on the same inventive concept, the present application further provides a computer storage medium, which stores a computer program, and the computer program is run by a processor to execute the above method. The storage medium can adopt any combination of one or more computer readable media. The computer readable medium can be a computer readable signal medium or a computer readable storage medium. The computer readable storage medium may, for example, but is not limited to, an electrical, magnetic, optical, electrical, magnetic, infrared, or semiconductor system, device or apparatus, or any combination thereof. More specific examples (non-exhaustive list) of the computer readable storage medium include: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present application, the computer readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, device or apparatus.

[0073] In the description of the present application, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

[0074] The basic principles, main features and advantages of the present disclosure are shown and described above. It should be understood by those skilled in the art that the present disclosure is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present disclosure. Without departing from the spirit and scope of the present disclosure, various changes and improvements can be made to the present disclosure, and these changes and improvements all fall within the scope of the claimed present disclosure.

Claims

1. A method for pulse density modulation sequence design for wireless power transfer, characterized by, The method comprises the following steps: The method comprises the following steps: The compensation topology is extracted, and the minimum harmonic distortion rate of the output current of the compensation topology under the same modulation density and each modulation sequence is calculated from the initial sequence as a starting point. The minimum harmonic distortion rate of all output currents is sorted, and the sequence corresponding to the minimum value in the minimum harmonic distortion rate of the output current is taken as the modulation sequence under the modulation density.

2. The method of claim 1, wherein, The parameters of the wireless power transmission system include: A DC source V1, a primary side inverter composed of four field effect transistors Q 1 / 2 / 3 / 4 and a secondary side rectifier composed of the same four field effect transistors Q 5 / 6 / 7 / 8 , a double-sided LCC compensation topology, a DC filter capacitor C d , a load resistor R L , wherein R L has a voltage of V2 across its two ends, the double-sided LCC compensation topology is composed of a compensation inductor L 1f / 2f and its internal resistance R 1f / 2f , a coupling inductor L 1 / 2 and its internal resistance R 1 / 2 , a series compensation capacitor C 1 / 2 and its parasitic resistance R c1 / c2 , a parallel compensation capacitor C 1f / 2f and its parasitic resistance R c1f / c2f , R c1 , R1 are combined into R t , R c2 , R2 are combined into R r , i 1 / 2 / 3 / 4 is the compensation network current, the working frequency of the primary side inverter is the resonance frequency f1, and the corresponding resonance period is t1=1 / f1.

3. The method of claim 2, wherein, The parameters of the wireless power transmission system satisfy the following formula condition: In formula (1), ω1 is the resonance angular frequency, and ω1=2πf1 is related to f1.

4. The method of claim 3, wherein, The circuit of the double-sided LCC compensation topology is decomposed into two subsystems: subsystem 1, subsystem 2, and subsystem m is only a voltage U m[n] Effect, I mk[n] Wherein, m = 1 / 2, k = 1 / 2 / 3 / 4 is the compensation network current under the action of U m[n] Z mk[n] The input impedance of each stage of the compensation network, Z ref1 / ref2 The reflected impedance of the secondary side and the reflected impedance of the primary side, respectively, and the calculation formulas are shown in formulas (2) and (3), respectively, on the basis of which, I mk[n] The calculation method is shown in formula (4): Further, I mk[n] With I 1[n] / 2[n] / 3[n] / 4[n] satisfies the following relationship: In formula (2), (3), (4), ω [n] denotes the angular frequency corresponding to the n-th harmonic phasor.

5. The method of claim 4, wherein, The secondary side of the wireless power transmission system adopts PDM modulation, and for the PDM modulation wave, a duty cycle T is defined on the basis of a modulation density D. When PDM modulation is adopted, according to the modulation characteristics of PDM, the compensation network output voltage u2 can be divided into two stages: an energy injection stage and a free oscillation stage. In the energy injection stage, Q5, Q8 or Q6, Q7 in the rectifier are simultaneously turned on, and the energy of the primary side is transmitted to the load in sequence through the inverter, the compensation topology and the rectifier. Due to the clamping of the DC filter capacitor, u2 has positive and negative polarities in the energy injection stage, and the polarity is related to i4. When i4 is positive, the polarity is negative, and vice versa. In the free oscillation stage, Q5, Q7 or Q6, Q8 are simultaneously turned on, and the load resistance is only the DC filter capacitor C d is supplied with power.

6. The method of claim 1, wherein, The modulation sequence takes a non-zero half-wave as a starting half-wave of a PDM working period and defines it as a reference half-wave, which also has two polarities, positive and negative, and further defines the offset step number The number of half-wave periods t1 / 2 in which the reference half-wave is ahead of the remaining half-waves, for a working period in which the offset step number is The Fourier decomposition result of the half-wave is shown in formula (6) and (7). Based on the superposition theorem, the amplitude and phase of any harmonic of any modulation sequence are obtained, but the amplitude depends on V2, which in turn depends on U 1[n] , U 2[n] , V2 is taken as an unknown quantity, the amplitude and phase of I 24[n] in subsystem 2 and the amplitude and phase of I 14[n] in subsystem 1 are calculated according to formula (4), the n-th harmonic phasor of the compensation network output current in the original system is obtained by using phasor addition according to formula (5), the value of V2 is calculated according to the principle of power conservation by using formula (8), and the amplitude of I 4[n] is obtained.

7. The method of claim 1, wherein, The minimum harmonic distortion rate of the output current is calculated using the total harmonic distortion rate formula shown in equation (9) to calculate the harmonic distortion rate of i4 using an arbitrary modulation sequence, where I base represents the amplitude of the current component corresponding to the resonance frequency, I h represents the amplitude of the harmonic current other than the resonance frequency; On the basis of the known PDM working period K·t1 / 2, the modulation step is taken as 1 / K, so the modulation density can be taken as x / K, wherein x=1, 2, 3,..., K. For each modulation density, the harmonic distortion rate of all modulation sequences under the modulation density is calculated, and the sequence with the minimum harmonic distortion rate is taken as the modulation sequence corresponding to the modulation density.

8. Apparatus for designing a pulse density modulation sequence for wireless power transfer, employing the method for designing a pulse density modulation sequence for wireless power transfer according to any one of claims 1 to 7, characterized in that Comprise: The sequence setting module is used for obtaining the modulation sequence period, determining the modulation step based on the modulation sequence period, and setting the initial sequence based on the modulation step. The compensation module is used for extracting the compensation topology, and calculating the minimum harmonic distortion rate of the output current of the compensation topology under the same modulation density and each modulation sequence from the initial sequence as a starting point. The sequence design module is used for sorting the minimum harmonic distortion rate of all output currents, and taking the sequence corresponding to the minimum value in the minimum harmonic distortion rate of the output current as the modulation sequence under the modulation density.

9. A terminal device comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that, The memory stores a computer program capable of running on the processor, and the processor loads and executes the computer program.

10. A computer-readable storage medium having stored therein a computer program, characterized in that, The computer program is loaded and executed by the processor, and the pulse density modulation sequence design method for wireless power transmission in any one of claims 1-7 is adopted.

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