Modeling method of bidirectional wireless power transmission system based on unified composite working mode

Abstract

The present invention is a modeling method for a bidirectional wireless power transmission system based on a unified composite working mode. The modeling method includes the following: taking the bidirectional wireless power transmission system with a bilateral LCC resonance topology as the object, and making a detailed division of the basic working stages of the system mode according to the different output levels of the bilateral H-bridges; when, the unified composite working mode Y of the system is denoted as PN / PO / PP / PO / ON / OO / OP / OO in the positive half cycle and NP / NO / NN / NO / OP / OO / ON / OO in the negative half cycle; when, the unified composite working mode Y<supgt;*< / supgt; of the system is denoted as PP / PO / PN / PO / OP / OO / ON / OO in the positive half cycle and NN / NO / NP / NO / ON / OO / OP / OO in the negative half cycle; obtaining the action time of each basic working stage of the unified composite working modes Y and Y<supgt;*< / supgt>; according to the physical structure of the bidirectional wireless power transmission system with bilateral LCC, combining the form of the unified composite working mode to obtain a unified discrete mathematical model equation, and completing the discrete modeling of the bidirectional wireless power transmission system.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a modeling method for a bidirectional wireless power transmission system based on a unified composite working mode. Background Art

[0002] The wireless power transmission system uses high-frequency alternating electromagnetic fields to transfer energy from one system to another without any physical connection. It has the advantages of safety, flexibility, long-distance transmission and easy maintenance, so it has attracted widespread attention from scholars at home and abroad. The bidirectional wireless power transmission (BWPT) system can realize the bidirectional flow of electric energy between the two systems, from the power grid to the vehicle, and from the vehicle to the power grid. Electric vehicles are used as energy storage devices to participate in the peak-shaving and valley-filling of the power grid with the Internet of Vehicles technology. While effectively solving the impact of electric vehicle charging on the power grid, it can also enhance the stability of the power grid, improve the quality of electricity, and increase the penetration rate of renewable energy. In addition, based on the bidirectional wireless power transmission system, electric vehicles can also be used as a power source to charge another electric vehicle or for home use.

[0003] Compared with the unidirectional wireless power transmission system, the bidirectional wireless power transmission system has more control and a complex system operation process. At present, the analysis of the bidirectional wireless power transmission system is mainly based on the two-port theory, and a mathematical model based on the fundamental wave is established. However, this model has problems such as low model accuracy and slow response speed in the analysis of system steady-state characteristics, soft switching characteristics and dynamic control. The modal analysis theory can show the actual working characteristics of the system to a great extent and realize the accurate analysis of the system. However, with the increase of the system control quantity, a large number of working modes will appear in the actual working process of the system, which greatly limits the use of modal analysis theory. It can be seen that it is very necessary to establish a unified mathematical model in a unified composite modal form to realize accurate modeling and analysis of the system. Summary of the invention

[0004] In order to solve the shortcomings of the above-mentioned prior art, the present invention proposes a modeling method for a two-way wireless power transmission system based on a unified composite working mode. The modeling method is in the form of a unified composite working mode, so as to comprehensively analyze all possible working modes of the system, simplify the analysis and modeling process of the system, and facilitate the accurate modeling and analysis of the system.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0006] The modeling method of a bidirectional wireless power transmission system based on a unified composite working mode of the present invention is characterized in that it comprises the following steps:

[0007] Step 1: According to the output voltage characteristics of the inverters on both sides of the bidirectional wireless power transmission system, the basic working stages of the system mode are divided in detail;

[0008] Step 2: Define the first switch tube S of the system leading bridge arm 11 The driving signal u G11 The positive and negative cycles of the system are distinguished by u G11 When it is high level, the system is defined as positive half cycle. G11 When the voltage level is zero, the system is defined as a negative half-cycle, and the output voltage waveforms of the H1 bridge and the H2 bridge show odd symmetry in positive and negative cycles. The working mode of the system is named in sequence according to the circuit stages that appear in the half-cycle.

[0009] exist When , the unified composite working mode Y of the system is recorded as PN / PO / PP / PO / ON / OO / OP / OO in the positive half cycle, and as NP / NO / NN / NO / OP / OO / ON / OO in the negative half cycle;

[0010] exist When the unified composite working mode Y * In the positive half cycle, it is recorded as PP / PO / PN / PO / OP / OO / ON / OO, and in the negative half cycle, it is recorded as NN / NO / NP / NO / ON / OO / OP / OO;

[0011] Among them, P represents the mode when the H-bridge outputs a positive level, N represents the mode when the H-bridge outputs a negative level, O represents the mode when the H-bridge outputs a zero level, and the " / " in the unified composite working mode represents the division of the basic working stage. The first letter before the " / " represents the output voltage of the H1 bridge, and the second letter represents the output voltage of the H2 bridge. is the external phase shift angle, i.e. S of the H2 bridge 21 The driving signal u of the tube G21 S relative to H1 bridge 11 The driving signal u of the tube G11 The phase shift angle between them; H1 bridge is the inverter bridge on the grid side, and H2 bridge is the inverter bridge on the battery side;

[0012] Get the unified composite working modes Y and Y * The duration of each basic work stage;

[0013] The above unified composite working modes Y and Y * According to the output voltage characteristics of the double-side inverters under different working conditions, the main working modes of the system are obtained. By analyzing the composition rules of the main working modes of the system, the specific forms and the action time of the basic composition stages are summarized;

[0014] Step 3: According to the physical structure of the bilateral LCC bidirectional wireless power transmission system, the state space model of each basic working stage is obtained, and a unified discrete mathematical model equation is obtained by combining the unified composite working modal form to complete the discrete modeling of the bidirectional wireless power transmission system.

[0015] The modeling method of a bidirectional wireless power transmission system based on a unified composite working mode described in the present invention is also characterized in that in step 1, the control variables of the system include the working frequency f, the internal phase shift angle α of the H1 bridge 1 、Internal phase shift angle α of H2 bridge 2 and the external phase shift angle of the H bridge on both sides The driving signals of the two switch tubes in the same bridge arm of the H1 bridge and the H2 bridge are complementary and the duty cycle is 50%. 12 The driving signal u of the tube G12 Relative to S 11 The driving signal of the tube is u G11 The phase shift angle is the internal phase shift angle α 1 、S of H2 bridge 22 The driving signal u of the tube G22 Relative to S 21 The driving signal u of the tube G21 The phase shift angle between is the internal phase shift angle α 2 、S of H2 bridge 21 The driving signal u of the tube G21 S relative to H1 bridge 11 The driving signal u of the tube G11 The phase shift angle between is the external phase shift angle The system power transmission direction is determined by control.

[0016] In step 1: the voltage on the DC grid side is U dc , the battery side voltage is U bat , the inverter bridge on the grid side is H1 bridge, the inverter bridge on the battery side is H2 bridge, the H bridge outputs positive level in mode P, negative level in mode N, and zero level in mode O. Based on this, it can be obtained that in the entire working process of the two-way wireless power transmission system, all possible working stages are PN, PP, PO, NN, NP, NO, ON, OP and OO. Among them, when the system works in the PN stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is -U bat ; When the system works in the PP stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is U bat ; When the system works in the PO stage, the output voltage of the H1 bridge is U dc, the output voltage of H2 bridge is zero; when the system works in the NN stage, the output voltage of H1 bridge is -U dc , the output voltage of H2 bridge is -U bat ; When the system works in the NP stage, the output voltage of the H1 bridge is -U dc , the output voltage of H2 bridge is U bat ; When the system works in the NO stage, the output voltage of the H1 bridge is -U dc , the output voltage of H2 bridge is zero; when the system works in the ON stage, the output voltage of H1 bridge is zero, and the output voltage of H2 bridge is -U bat ; When the system works in the OP stage, the output voltage of the H1 bridge is zero, and the output voltage of the H2 bridge is U bat ; When the system works in the OO stage, the output voltage of the H1 bridge is zero and the output voltage of the H2 bridge is zero.

[0017] exist When the system's positive half-cycle unified composite working mode Y: PN / PO / PP / PO / ON / OO / OP / OO, the action time of each basic working stage is expressed as t n1 ,t n2 ,t n3 ,t n4 ,t n5 ,t n6 ,t n7 and t n8 Indicated by Y All possible working modes of the system in the composite control under the condition, for those working stages that do not appear in the actual working mode, their action time is considered to be zero;

[0018] Assume the operating frequency of the system is f s , then ω s =2πf s , the action time t of the basic working stage in the positive half-cycle unified composite working mode Y n1 ~t n8 And the system control variable operating frequency f, the internal phase shift angle α of the H1 bridge 1 、Internal phase shift angle α of H2 bridge 2 and the external phase shift angle of the H bridge on both sides The relationship between them is:

[0019] 1)t n1 The expression is:

[0020]

[0021] 2)t n2 The expression is:

[0022]

[0023] 3)t n3 The expression is:

[0024]

[0025] 4)t n4 The expression is:

[0026]

[0027] 5)t n5 The expression is:

[0028]

[0029] 6)t n6 The expression is:

[0030]

[0031] 7)t n7 The expression is:

[0032]

[0033] 8)t n8 The expression is:

[0034]

[0035] Similarly, in When the system's positive half-cycle unified composite working mode Y * :The action time of each basic working stage of PP / PO / PN / PO / OP / OO / ON / OO is expressed as t m1 ,t m2 ,t m3 ,t m4 ,t m5 ,t m6 ,t m7 and t m8 Indicates that through Y * express All possible working modes of the system in the composite control under the condition, for those working stages that do not appear in the actual working mode, their action time is considered to be zero; the positive half-cycle unified composite working mode Y * The action time t of the basic work stage m1 ~t m8 And the system control variable operating frequency f, the internal phase shift angle α of the H1 bridge 1 、Internal phase shift angle α of H2 bridge 2 and the external phase shift angle of the H bridge on both sides The relationship between them is:

[0036] 1)t m1 The expression is:

[0037]

[0038] 2)t m2 The expression is:

[0039]

[0040] 3)t m3 The expression is:

[0041]

[0042] 4)t m4 The expression is:

[0043]

[0044] 5)t m5 The expression is:

[0045]

[0046] 6)t m6 The expression is:

[0047]

[0048] 7)t m7 The expression is:

[0049]

[0050] 8)t m8 The expression is:

[0051]

[0052] The arrangement order and action time of each stage in the actual working mode of the system are closely related to the system control quantity. When the system works in mode I, the six main modes of the system can be obtained. The common point of these six modes is that they are composed of four working stages, namely PO / PP / PO / OO (mode I), PO / PP / OP / OO (mode II), PN / PO / PP / OP (mode III), PO / OO / OP / OO (mode IV), PN / PO / OO / OP (mode V) and PN / ON / OO / OP (mode VI). When the system works in mode I, When the system works in mode II, When the system works in mode III, When the system works in mode IV, When the system works in mode V, When the system works in mode VI,

[0053] Combining the order of each stage in Mode I to Mode VI, the analysis concludes that The unified composite working mode Y of the system is PN / PO / PP / PO / ON / OO / OP / OO, where t n1 ,t n2 ,t n3 ,t n4 ,t n5 ,t n6 ,t n7 and t n8 Represents the action time of each stage. Through mode Y, it can be expressed For all possible working modes of the system in the composite control under certain conditions, the action time of those working stages that do not appear in the actual working mode can be considered to be zero.

[0054] Combining the action time of each stage in mode I to mode VI, the action time t of the basic working stage in the unified composite working mode Y is obtained. n1 ~t n8 and system control variables f, α 1 , α 2 , The relationship between them.

[0055] exist The arrangement order and action time of each stage in the actual working mode of the system are closely related to the system control quantity. It can be obtained that the system consists of six main modes under different working conditions. The common point of these six modes is that they are composed of 4 working stages, namely PP / OP / OO / ON (mode VII), PP / PO / OO / ON (mode VIII), PP / PO / PN / ON (mode IX), PO / OO / ON / OO (mode X), PO / PN / ON / OO (mode XI) and PO / PN / PO / OO (mode XII). When the system works in mode VII, When the system works in mode VIII, When the system works in mode IX, When the system works in mode X, When the system works in mode XI, When the system works in mode XII,

[0056] Combining the order of each stage in Mode VII to Mode XII, the analysis and conclusion are as follows: The positive half-cycle unified composite working mode Y of the system *PP / PO / PN / PO / OP / OO / ON / OO, where t m1 ,t m2 ,t m3 ,t m4 ,t m5 ,t m6 ,t m7 and t m8 Represents the action time of each stage. * Can be expressed For all possible working modes of the system in the composite control under certain conditions, the action time of those working stages that do not appear in the actual working mode can be considered to be zero.

[0057] Combining the action time of each stage in mode VII to mode XII, the unified composite working mode Y is obtained. * The action time t of the basic work stage m1 ~t m8 and system control variables f, α 1 , α 2 , The relationship between them.

[0058] The construction process of the unified discrete mathematical model equation is:

[0059] Step 3.1, the system structure is a bidirectional wireless power transmission system based on bilateral LCC resonance topology, and i 1 、u C1 、u Cp1 、i L1 、i L2 、u Cp2 、u C2 and i 2 is the state variable of the system, and its mathematical expression is:

[0060]

[0061] Where: i 1 is the current flowing through the series resonant inductor on the grid side; u C1 is the voltage of the parallel resonant capacitor on the grid side; u Cp1 is the voltage of the DC blocking capacitor in series on the grid side; i L1 is the current flowing through the magnetic coupling coil on the grid side; i L2 is the current flowing through the magnetic coupling coil on the battery side; u Cp2 is the voltage of the DC blocking capacitor connected in series on the battery side; u C2 is the voltage of the parallel resonant capacitor on the battery side; i 2 is the current flowing through the series resonant inductor on the battery side;

[0062] Step 3.2, based on the circuit structure of the bidirectional wireless power transmission system with bilateral LCC resonant topology, Y and Y * The positive half cycle consists of 8 basic working stages, and the negative half cycle also consists of 8 basic working stages. The positive and negative cycles are odd-symmetrical to each other. In the whole working process, it includes 16 working stages in sequence. A unified discrete time model is established. * Or Y each working stage write the mathematical expression of the state space is:

[0063] Among them, A s is the state matrix of the system, B s is the input control matrix of the system, P i Represents the basic working stage of the system. When the system works in the PN stage, P i =[1,-1] T ; During the PP stage, P i =[1,1] T ; During the PO phase, P i =[1,0] T ; During the NN stage, P i =[-1,-1] T ; In the NP stage, P i =[-1,1] T ; During the NO phase, P i =[-1,0] T ; During the ON phase, P i =[0,-1] T ; During the OP phase, P i =[0,1] T ; In the OO stage, P i =[0,0] T ; i represents the number of basic working stages in a cycle, and the input U of the system is written in matrix form, that is,

[0064] Step 3.3, use formula (23) to get the unified composite working mode Y * Or the discrete time model of the switching state points of each basic working stage of Y:

[0065]

[0066] Among them, U i =UP i In formula (23), when i=1, the x n0 is the state variable x of the system n , that is: x n0 =x n When i=16, the system works for one cycle and the xn16 is the state variable x of the system n+1 , that is: x n16 =x n+1 , x n represents the state variable of the system at the beginning of the nth cycle, x n+1 Represents the state variable of the system at the beginning of the n+1th cycle. n to x n+1 During this period, the system switches state variables to x n1 、x n2 , …, x n15 , κ n is an organic combination of the control variables of the system, that is f ni (x n(i-1) , κ n ) represents the iterated function; ψ i is the matrix related to the zero-state response of the system;

[0067] Step 3.4: Obtain the state variable x of the system at the beginning of the n+1th cycle from the iterative relationship in equation (23): n+1 The expression of the system is x when it is running in steady state n+1 =x n , and obtain the system state variable value x when the system is running stably nss The mathematical expression of is formula (26):

[0068] x nss =[I 0 -F(κ n )] -1 G(κ n ,U i ) (26)

[0069] In formula (26), F(κ n ) is the state matrix related to the initial state of the system, G(κ n , U i ) is the state matrix related to the system input; I 0 is the identity matrix;

[0070] Step 3.5, use equation (30) to get the expression of the output power of the double-sided H-bridge:

[0071]

[0072]

[0073] In formula (30), M i is the process variable matrix of the output power of the double-sided H-bridge, with a matrix dimension of 8×1, M i (k) is the matrix Mi The value of the kth position in , where: i = 1, 2, ..., 16; k = 1, 2, ..., 8; in formula (31), P H1 is the average power generated by the H1 bridge on the grid side in the nth cycle of the system, P H2 is the average power generated by the H2 bridge on the battery side in the nth cycle of the system; T s is the system working cycle.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] 1. The present invention takes the bidirectional wireless power transmission system with bilateral LCC resonant topology compensation as the object, takes the modal analysis theory as the basis, and divides the system into 9 basic working stages according to the characteristics of the output level of the bilateral H-bridge; according to the combination law of the main modes of the bidirectional wireless power transmission system under the composite control (frequency modulation plus hybrid phase shift), a unified composite modal form and the action time of each component stage of the composite modal are summarized, which reduces the workload and working time of the modal analysis and enhances the flexibility of the modal analysis. It is worth noting that the unified composite modal form in the present invention is obtained based on the most complex composite control. The arrangement order and action time of the component stages of the composite modal are closely related to the system control quantity, which can be reflected by the expression of the action time of each stage. Therefore, when the system is controlled, the control variables are f, α 1 , α 2 and When at least one of them is present, the composite working mode is also applicable.

[0076] 2. The present invention is based on a unified composite modal form. In the mathematical analysis process of the system, only a mathematical model needs to be established, which simplifies the modeling and analysis process and establishes a unified discrete time domain mathematical model of the two-way wireless power transmission system. The mathematical model can intuitively display the internal and external performance of the system in any operation process, while reducing the amount of calculation and ensuring the modeling accuracy.

[0077] 3. The mathematical model established by the present invention is based on the time domain state space equations ( The time domain construction starts with the differential equations of the simultaneous system, and then the state space model is established, and then the discrete time domain iterative equations are established), and a discrete time domain mathematical model of the two-way wireless power transmission system is established. All modeling and analysis processes are carried out in the time domain. Compared with the traditional frequency domain modeling analysis theory, the present invention has high accuracy in describing the dynamic characteristics of the system and predicting the steady-state characteristics when considering system parasitic parameters, system detuning and low power conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1It is a topological structure principle diagram of the present invention;

[0079] Figure 2 It is the switch control waveform of the BWPT system;

[0080] Figure 3a This is the circuit structure diagram when the system works in the PP stage;

[0081] Figure 3b This is the circuit structure diagram when the system works in the PN stage;

[0082] Figure 3c This is the circuit structure diagram when the system works in the PO stage;

[0083] Figure 3d It is the circuit structure diagram when the system works in the NP stage;

[0084] Figure 3e It is the circuit structure diagram when the system works in the NN stage;

[0085] Figure 3f This is the circuit structure diagram when the system works in the NO stage;

[0086] Figure 3g This is the circuit structure diagram when the system works in the OP stage;

[0087] Figure 3h This is the circuit structure diagram when the system works in the ON stage;

[0088] Figure 3i It is the circuit structure diagram when the system works in the OO stage;

[0089] Figure 4a It is the output voltage waveform of the double-sided H-bridge when the system working mode is PO / PP / PO / OO (referred to as mode I);

[0090] Figure 4b It is the output voltage waveform of the double-sided H-bridge when the system working mode is PO / PP / OP / OO (referred to as mode II);

[0091] Figure 4c It is the output voltage waveform of the double-sided H-bridge when the system working mode is PN / PO / PP / OP (referred to as mode III);

[0092] Figure 4d It is the output voltage waveform of the double-side H-bridge when the system working mode is PO / OO / OP / OO (referred to as mode IV);

[0093] Figure 4e It is the output voltage waveform of the double-sided H-bridge when the system working mode is PN / PO / OO / OP (referred to as mode V);

[0094] Figure 4f It is the output voltage waveform of the double-side H-bridge when the system working mode is PN / ON / OO / OP (referred to as mode VI);

[0095] Figure 5 It is the operation process of unified composite working mode Y;

[0096] Figure 6a It is the output voltage waveform of the double-side H-bridge when the system working mode is PP / OP / OO / ON (referred to as mode VII);

[0097] Figure 6b It is the output voltage waveform of the double-side H-bridge when the system working mode is PP / PO / OO / ON (referred to as mode VIII);

[0098] Figure 6c It is the output voltage waveform of the double-side H-bridge when the system working mode is PP / PO / PN / ON (referred to as mode IX);

[0099] Figure 6d It is the output voltage waveform of the double-sided H-bridge when the system working mode is PO / OO / ON / OO (referred to as mode X);

[0100] Figure 6e It is the output voltage waveform of the double-sided H-bridge when the system working mode is PO / PN / ON / OO (abbreviated as mode XI);

[0101] Figure 6f It is the output voltage waveform of the double-sided H-bridge when the system working mode is PO / PN / PO / OO (referred to as mode XII);

[0102] Figure 7 is the unified composite working mode Y * Operation process;

[0103] Figure 8 It is an iterative relationship diagram of state variables within a cycle. DETAILED DESCRIPTION

[0104] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0105] In this embodiment, a modeling method for a bidirectional wireless power transmission system based on a unified composite working mode is to take a bidirectional wireless power transmission system with a bilateral LCC resonant topology as an object, based on modal analysis theory, and according to the characteristics of the output voltage of the bilateral H-bridge under composite control, a unified composite modal form is obtained, and according to the time domain state space model of the bidirectional wireless power transmission system based on the bilateral LCC resonant topology, a unified discrete time domain mathematical model is established, so that the model can accurately describe the intrinsic and extrinsic characteristics of the system, and the modeling method includes the following steps:

[0106] Step 1: According to the output voltage characteristics of the inverters on both sides of the bidirectional wireless power transmission system, the basic working stages of the system mode are divided in detail:

[0107] The circuit structure of the bidirectional wireless power transmission system with bilateral LCC resonant topology is shown in the attached figure. Figure 1 As shown in the figure, the H-bridges on the DC grid side and the battery side are both composed of high-frequency fully controlled power devices, among which the H1 bridge on the DC grid side consists of four switch tubes S 11 ~S 14 The H2 bridge on the battery side consists of four switch tubes S 21 ~S 24 Composition: L f1 , C 1 , C p1 The grid-side compensation circuit is composed of L f2 , C 2 , C p2 The battery side compensation circuit is composed of the DC bus side and the battery side connected by a loosely coupled wireless energy transmission coil, where L 1 and L 2 are the self-inductance of the transmitting coil and the receiving coil respectively, and M is the mutual inductance between the transmitting coil and the receiving coil.

[0108] The switch control waveform of the system is shown in the attached figure. Figure 2 As shown; the control variables of the system include the operating frequency f, the internal phase shift angle α of the H1 bridge 1 、Internal phase shift angle α of H2 bridge 2 and the external phase shift angle of the H bridge on both sides The driving signals of the two switch tubes in the same bridge arm of the H1 bridge and the H2 bridge are complementary and the duty cycle is 50%. 12 The driving signal u of the tube G12 Relative to S 11 The driving signal of the tube is u G11 The phase shift angle is the internal phase shift angle α 1 、S of H2 bridge 22 The driving signal u of the tube G22 Relative to S 21 The driving signal u of the tube G21The phase shift angle between is the internal phase shift angle α 2 、S of H2 bridge 21 The driving signal u of the tube G21 S relative to H1 bridge 11 The driving signal u of the tube G11 The phase shift angle between is the external phase shift angle The power transmission direction of the system is determined by the external phase shift angle control.

[0109] Set the DC grid voltage to U dc , the battery side voltage is U bat , the inverter bridge on the grid side is H1 bridge, the inverter bridge on the battery side is H2 bridge, when the H bridge outputs a positive level, it is mode P, when it outputs a negative level, it is mode N, and when it outputs a zero level, it is mode O. By analyzing the working modes of the double-sided H bridges under composite control, it can be obtained that in the entire working process of the two-way wireless power transmission system, the possible working stages are PN, PP, PO, NN, NP, NO, ON, OP and OO. The circuit structure of each stage is shown in the attached figure. Figure 3a-Figure 3i shown.

[0110] When the system works in the PN stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is -U bat ; When the system works in the PP stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is U bat ; When the system works in the PO stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is zero; when the system works in the NN stage, the output voltage of H1 bridge is -U dc , the output voltage of H2 bridge is -U bat ; When the system works in the NP stage, the output voltage of the H1 bridge is -U dc , the output voltage of H2 bridge is U bat ; When the system works in the NO stage, the output voltage of the H1 bridge is -U dc , the output voltage of H2 bridge is zero; when the system works in the ON stage, the output voltage of H1 bridge is zero, and the output voltage of H2 bridge is -U bat ; When the system works in the OP stage, the output voltage of the H1 bridge is zero, and the output voltage of the H2 bridge is U bat ; When the system works in the OO stage, the output voltage of the H1 bridge is zero and the output voltage of the H2 bridge is zero.

[0111] Step 2: According to the output voltage characteristics of the double-side inverters under different working conditions, the main working modes of the system are obtained. By analyzing the composition rules of the main working modes of the system, a unified composite modal form and the action time of its basic composition stage are summarized:

[0112] As attached Figure 2 As shown, the H1 bridge switch tube S on the grid side 11 The driving signal u G11 The positive and negative cycles of the system are distinguished by u G11 When it is high level, the system is defined as positive half cycle. G11 When the voltage level is zero, the system is defined as a negative half cycle. The output voltage waveforms of the H1 bridge and the H2 bridge show odd symmetry in the positive and negative cycles. The working mode of the system is named in sequence according to the circuit stages that appear in the positive half cycle. The unified composite working mode analysis process of the system (in When the unified composite operating modal analysis refers to the composite mode Y, When the unified composite operating modal analysis refers to the composite mode Y * , mode I\II, etc. are the modes that may appear in the system during operation. The unified composite working modal analysis refers to the composite mode Y or Y * It is a hypothetical virtual mode derived through analysis and summary based on mode I\II, etc., to unify the composite working mode Y or Y * The action time of each basic working stage is closely related to the system control variables. By bringing in the working conditions to unify the composite working mode Y or Y * It can be simplified into mode I\II, etc.) as shown below:

[0113] exist When combined with Figure 2 It can be seen that in the positive half cycle of the system, PP, PN and PO can only appear at the output u of the H1 bridge. 1 =U dc When, that is, the interval [0, α 1 ]; OP, ON and OO can only appear at the H1 bridge output u 1 = 0, that is, the interval (α 1 ,π]. It can be concluded that in the unified composite working mode, PP, PN and PO must appear before OP, ON and OO. The arrangement order and action time of each stage in the actual working mode of the system are closely related to the system control quantity. Figure 4a ~Attached Figure 4f Demonstrated system in When the system works in mode I, it consists of six main modes under different working conditions. The common point of these six modes is that they are composed of four working stages, namely PO / PP / PO / OO (mode I), PO / PP / OP / OO (mode II), PN / PO / PP / OP (mode III), PO / OO / OP / OO (mode IV), PN / PO / OO / OP (mode V) and PN / ON / OO / OP (mode VI). When the system works in mode I, When the system works in mode II, When the system works in mode III, When the system works in mode IV, When the system works in mode V, When the system works in mode VI,

[0114] In the interval [0, α 1 ], the condition for the occurrence of PP is The conditions for the occurrence of PN are along with As the value of Figure 4c As shown in Figure 2, it can be seen that in the actual working mode, PN must appear before PP. The position and frequency of PO are relatively flexible. 1 ] appears at most twice, and the condition for appearing twice is α 1 >α 2 ,and Occurs once or zero times under other conditions, such as Figure 4a As shown, when PO appears twice, one appears before PP and the other appears after PP. Considering this special case, in the interval [0, α 1 ], the unified composite working mode Y composition is defined as PN / PO / PP / PO.

[0115] In the interval (α 1 ,π], the condition for the occurrence of OP is α 1 >α 2 hour and α 2 >α 1 hour The condition for ON to occur is α 2 >α 1 and along with As the value of Figure 4f As shown in Figure 2, we can know that in the actual working mode, ON must appear before OP. The position and frequency of OO are also flexible. 1 ,π] appears at most twice, and the condition for appearing twice is π-α 1 >α 2 ,and Occurs once or zero times under other conditions, such as Figure 4d As shown, when OO appears twice, one appears before OP and the other appears after OP. Considering this special case, in the interval (α 1 ,π], the unified composite working mode Y is defined as ON / OO / OP / OO.

[0116] Therefore, the composition of the unified composite working mode Y in the positive half cycle is PN / PO / PP / PO / ON / OO / OP / OO, where t n1 ,t n2 ,t n3 ,t n4 ,t n5 ,t n6 ,t n7 and t n8 Represent the action time of each stage respectively. According to the symmetry characteristics of the system, the composition of the unified composite working mode Y in the negative half cycle is NP / NO / NN / NO / OP / OO / ON / OO, and its action time is t n9 ,t n10 ,t n11 ,t n12 ,t n13 ,t n14 ,t n15 ,t n16 , at this time, the action time of each basic working stage in the negative half cycle is equal to the action time of each basic working stage in the positive half cycle, that is, t ni =t n(i+8) , i = 1, 2, ..., 8, and the following will only take the calculation of the positive half-cycle time as an example. Figure 5 The operation process of each basic working stage in the unified composite working mode Y in the whole cycle is shown. The arrows in the figure represent the operation order of each stage in the system cycle, which is divided into two parts: the positive half cycle and the negative half cycle. For example, the composition of mode Y in the positive half cycle is PN / PO / PP / PO / ON / OO / OP / OO, so the operation stage of the system in the positive half cycle is PN→PO→PP→PO→ON→OO→OP→OO, as shown in the attached figure. Figure 5 As shown, the operation process of the negative half cycle can be obtained by the same token.

[0117] Assume that the operating frequency of the system is f s , then ω s =2πf s , the running time of each stage in the unified composite working mode Y is as follows:

[0118] 1)t n1 :As attached Figure 4c , Attachment Figure 4e and attached Figure 4f As shown, PN is included in mode III, mode V and mode VI, and we can get ω s t n1 The maximum value of min{α 1 , α 2}, in Mode III and Mode V, In mode VI, ω s t n1=α 1 . Combined with the constraints of each mode, t n1 It is given by the following formula.

[0119]

[0120] 2)t n2 :As attached Figure 4a ~Attached Figure 4e As shown, here PO is the first PO in the unified composite working mode Y (the first one when one or two appear), and ω s t n2 The maximum value of min{α 1 ,π-α 2}, in Mode I and Mode II, In mode III, ω s t n2 =π-α 2 ; In mode IV, ω s t n2 =α 1 ; In mode V, Combined with the constraints of each mode, t n2 It is given by the following formula.

[0121]

[0122] 3)t n3 :As attached Figure 4a ~Attached Figure 4c As shown, PP is included in mode I, mode II and mode III, and we can get ω s t n3 The maximum value of min{α 1 , α 2}, in mode I, ω s t n3 =α 2 ; In Mode II and Mode III, Combined with the constraints of each mode, t n3 It is given by the following formula.

[0123]

[0124] 4)t n4 :As shown in the picture Figure 4a As shown, PO is included in mode I, which represents the second PO when two POs appear in the unified composite working mode Y. We can get ω s t n4 The maximum value of max{α 1 -α 2 ,0}, in mode I, Combined with the modal constraints, t n4 It is given by the following formula.

[0125]

[0126] 5)t n5 :As attached Figure 4f As shown, ON is included in mode VI, and we can get ω s t n5 The maximum value of max{α 2 -α 1 ,0}, in mode VI, Combined with the constraints of this mode, t n5 It is given by the following formula.

[0127]

[0128] 6)t n6 :As attached Figure 4d ~Attached Figure 4f As shown, OO is included in mode IV, mode V and mode VI. To unify the OO before OP in the composite working mode Y, we can get ω s t n6 The maximum value of min{π-α 1 ,π-α 2}. In Mode IV and Mode V, In the modal VI, ω s t n6 =π-α 2 . Combined with the constraints of each mode, t n6 It is given by the following formula.

[0129]

[0130] 7)t n7 :As attached Figure 4b ~Attached Figure 4f As shown, we can get ω s t n7 The maximum value of min{π-α 1 , α 2}, in mode II, In mode III, ω s t n7 =π-α 1 ; In mode IV, ω s t n7 =α 2 ; In Mode V and Mode VI, Combined with the constraints of each mode, t n7 It is given by the following formula.

[0131]

[0132] 8)t n8 :As attached Figure 4a ~Attached Figure 4d As shown, here OO is the OO after OP in the unified composite working mode Y and in mode I, we can get ω s t n8 The maximum value of min{π-α 1 ,π-α 2}. In mode I, ω s t n8 =π-α 1 ; In Mode II and Mode IV, Combined with the constraints of each mode, t n8 It is given by the following formula.

[0133]

[0134] exist When combined with Figure 2 It can be seen that in the positive half cycle of the system, PP, PN and PO must appear before OP, ON and OO. The arrangement order and action time of each stage in the actual working mode of the system are closely related to the system control quantity. Figure 6a ~Attached Figure 6f Demonstrated system in When the system works in mode VII, it consists of six main modes under different working conditions. The common point of these six modes is that they are composed of four working stages, namely PP / OP / OO / ON (mode VII), PP / PO / OO / ON (mode VIII), PP / PO / PN / ON (mode IX), PO / OO / ON / OO (mode X), PO / PN / ON / OO (mode XI) and PO / PN / PO / OO (mode XII). When the system works in mode VII, When the system works in mode VIII, When the system works in mode IX, When the system works in mode X, When the system works in mode XI, When the system works in mode XII,

[0135] In the interval [0, α 1 ], the condition for the occurrence of PP is The conditions for the occurrence of PN are along with As the value of PN increases, the position of PN in the mode will move to the left. Figure 6cAs shown in Figure 2, it can be seen that in the actual working mode, PP must appear before PN. The position and frequency of PO are relatively flexible. 1 ] appears at most twice, and the condition for appearing twice is α 1 >α 2 ,and Occurs once or zero times under other conditions, such as Figure 6f As shown, when PO appears twice, one appears before PN and the other appears after PN. Considering this special case, in the interval [0, α 1 ], the composite working mode Y * The composition is defined as PP / PO / PN / PO.

[0136] In the interval (α 1 ,π], the condition for the occurrence of OP is α 1 <α 2 and The condition for ON to occur is α 1 <α 2 or α 2 <α 1 and along with As the value of ON increases, the position of ON in the mode will move to the left. Figure 6a As shown in Figure 2, we can know that in the actual working mode, OP must appear before ON. The position and frequency of OO are also flexible. 1 ,π] appears at most twice, and the condition for it to appear twice is Under other conditions, it appears once or zero times, as shown in the attached figure Figure 6d As shown, when it appears twice, one appears before ON and the other appears after ON. Considering this special case, in the interval (α 1 ,π], the unified composite working mode Y * The composition is defined as OP / OO / ON / OO.

[0137] Therefore, the unified composite working mode Y can be obtained * The composition in the positive half cycle is PP / PO / PN / PO / OP / OO / ON / OO, and it is assumed that the action time corresponding to each stage is t m1 ,t m2 ,t m3 ,t m4 ,t m5 ,t m6 ,t m7 ,t m8 According to the symmetry characteristics of the system, the unified composite working mode Y *The composition in the negative half cycle is NN / NO / NP / NO / ON / OO / OP / OO, and the corresponding action time of each stage is t m9 ,t m10 ,t m11 ,t m12 ,t m13 ,t m14 ,t m15 ,t m16 , the action time of the corresponding sequence in the positive half cycle and the negative half cycle is equal, that is, t mi =t m(i+8) ,i=1,2,…,8. attached Figure 7 Demonstrates the unified composite working mode Y * The arrows in the figure represent the operation sequence of each stage in the system cycle, which is divided into positive half cycle and negative half cycle.

[0138] Unified composite working mode Y * The running time of each stage in is shown below.

[0139] 1)t m1 :As attached Figure 6a ~Attached Figure 6c As shown, PP is included in mode VII, mode VIII and mode IX, and we can get ω s t m1 The maximum value of min{α 1 , α 2}, in mode VII, α 1 <α 2 ,when When s t m1 =α 1 ,when hour, In Modes VIII and IX, α 2 <α 1 ,when hour, Combined with the constraints of each mode, t m1 It is given by the following formula.

[0140]

[0141] 2)t m2 :As attached Figure 6b ~Attached Figure 6f As shown, PO here is the unified composite working mode Y * The first PO in (the first one when one or two appear), we can get ω s t m2 The maximum value of min{α 1,π-α 2}, in mode VIII, In Mode IX, ω s t m2 =π-α 2 ; In mode X, ω s t m2 =α 1 ; In Modes XI and XII, Combined with the constraints of each mode, t m2 It is given by the following formula.

[0142]

[0143] 3)t m3 :As attached Figure 6c , Attachment Figure 6e and attached Figure 6f As shown, PN is included in mode IX, mode XI and mode XII, and we can get ω s t m3 The maximum value of min{α 1 , α 2}, in Mode IX and Mode XI, In Mode XII, ω s t m3 =α 2 . Combined with the constraints of each mode, t m3 It is given by the following formula.

[0144]

[0145] 4)t m4 :As attached Figure 6f As shown, PO is included in mode XII, which represents the unified composite working mode Y * When two POs appear in the second PO, we can get ω s t m4 The maximum value of max{α 1 -α 2 ,0}, in mode XII, Combined with the modal constraints, t m4 It is given by the following formula.

[0146]

[0147] 5)t m5 :As attached Figure 6a As shown, OP is included in mode VII, and we can get ω s t m5 The maximum value of max{α 2 -α 1,0}, in mode VII, Combined with the constraints of this mode, t m5 It is given by the following formula.

[0148]

[0149] 6)t m6 :As attached Figure 6a , Attachment Figure 6b and attached Figure 6d As shown, OO is included in mode VII, mode VIII and mode X, which is a unified composite working mode Y. * The OO before ON in the middle can get ω s t m6 The maximum value of min{π-α 1 ,π-α 2}. In mode VII, ω s t m6 =π-α 2 ; In Mode VIII and Mode X, Combined with the constraints of each mode, t m6 It is given by the following formula.

[0150]

[0151] 7)t m7 :As attached Figure 6a ~Attached Figure 6e As shown, we can get ω s t m7 The maximum value of min{π-α 1 , α 2}, in Mode XII and Mode VIII, In Mode IX, ω s t m7 =π-α 1 ; In mode XI, In mode X, ω s t m7 =α 2 . Combined with the constraints of each mode, t m7 It is given by the following formula.

[0152]

[0153] 8)t m8 :As attached Figure 6d ~Attached Figure 6f As shown, OO here is the unified composite working mode Y * After ON in the middle and OO in modal XII, we can get ω s t m8The maximum value of min{π-α 1 ,π-α 2}. In modal X and modal XI, In Mode XII, ω s t m8 =π-α 1 . Combined with the constraints of each mode, t m8 It is given by the following formula.

[0154]

[0155] Step 3: According to the physical structure of the bilateral LCC bidirectional wireless power transmission system, the state space model of each basic working stage is obtained, and the unified discrete mathematical model equation is obtained by combining the unified composite modal form:

[0156] Two-way wireless power transmission system and The unified composite working modes are Y and Y * , we can get Y and Y * The positive half cycle consists of 8 basic working stages, and the negative half cycle also consists of 8 basic working stages. The positive and negative cycles are odd-symmetrical to each other. In the entire working process, sixteen working stages are included in sequence to establish a unified discrete time model.

[0157] In order to facilitate mathematical analysis, P i =[a,b] T The matrix of the form represents the basic working subcircuit, a represents the grid side, b represents the battery side, the input positive pressure is represented by "1", the input zero pressure is represented by "0", and the input negative pressure is represented by "-1", such as PP is [1,1] T ,ON is [0,-1] T , OO is [0,0] T In one working cycle, the state relationship iteration relationship of the 16 sub-phases is as shown in the attached figure. Figure 8 In order to make the established model able to express Y and Y * , here we make the following settings: i =t ni or mi , (i=1,2…,7,8), t i =t n(i-8) or m(i-8) , (i=9, 10..., 15, 16), in , bring in each operating sub-stage of Y and the corresponding action time t ni ;exist When Y * Each operating sub-stage and the corresponding action time t mi .

[0158] The state space equations of the system are: State matrix A of bidirectional wireless power transmission system based on bilateral LCC s for:

[0159]

[0160] Where:

[0161]

[0162] The input control matrix B of the system s It is given by the following formula.

[0163]

[0164] The input of the system is written in matrix form, namely, matrix U, as shown in equation (20). Here, we assume that U i =UP i .

[0165]

[0166] In the present invention, take i 1 、u C1 、u Cp1 、i L1 、i L2 、u Cp2 、u C2 and i 2 is the state variable of the bidirectional wireless power transmission system based on bilateral LCC, that is:

[0167]

[0168] In formula (21): i 1 is the current flowing through the series resonant inductor on the grid side; u C1 is the voltage of the parallel resonant capacitor on the grid side; u Cp1 is the voltage of the DC blocking capacitor in series on the grid side; i L1 is the current flowing through the magnetic coupling coil on the grid side; i L2 is the current flowing through the magnetic coupling coil on the battery side; u Cp2 is the voltage of the DC blocking capacitor connected in series on the battery side; u C2 is the voltage of the parallel resonant capacitor on the battery side; i 2 is the current flowing through the series resonant inductor on the battery side.

[0169] In steady state, the value of the starting time of a cycle is x n , the value at the end time is x n+1 , when i=1, the x that appears n0At this time, the state variable of the system is x n , when i=16, the state variable of the system is x n+1 , x n represents the state variable of the system at the beginning of the nth cycle. n to x n+1 During this period, the system switches state variables to x n1 、x n2 , …, x n15 , let κ n is an organic combination of control variables of the bidirectional wireless power transmission system based on bilateral LCC, that is, By the attached Figure 8 It can be seen that state P i The duration of the i , let the time variable t∈(0, t i ), according to the solution form of the non-homogeneous state equation:

[0170]

[0171] The discrete time model of each switching state point can be obtained from the above formula as follows:

[0172]

[0173] In formula (23), f ni (x n(i-1) , κ n ) is an iterative function, which is:

[0174]

[0175] In the formula, when i=1, the x in formula (23) n0 is the state variable x of the system n , that is: x n0 =x n When i=16, the system works for one cycle and the x n16 is the state variable x of the system n+1 , that is: x n16 =x n+1 , x n represents the state variable of the system at the beginning of the nth cycle, x n+1 Represents the state variable of the system at the beginning of the n+1th cycle, I 0 is the unit matrix. In formula (24), i=1~8 represents the positive half cycle, and i+8 represents the negative half cycle; ψ i is the matrix associated with the zero-state response of the system.

[0176] Combined with Figure 8 As shown, the iterative relationship in formula (23) is:

[0177]

[0178] When the system is running in steady state x n+1 =x n , by bringing in the system operation conditions, the steady-state operating point during steady-state operation can be obtained:

[0179] x nss =[I 0 -F(κ n )] -1 G(κ n ,U i ) (26)

[0180] System working cycle T s =1 / f s , let T a u is the H1 bridge in one working cycle 1 =U dc The duration of u in the positive half cycle can be obtained. 1 =0 lasts for T s / 2-T a , so we can get:

[0181]

[0182] Here we take the following intermediate variables:

[0183]

[0184] F(κ n ) and G(κ n , U i ) is given by the following formula.

[0185]

[0186] Combined with formula (23), the switching state variable value x of the system at the switching state point in each operation stage can be calculated: ni (i=1,2,...,15), since the system operating waveform has odd symmetry in each half switching cycle, the corresponding transmission power of the system can be solved by analyzing the operating state of the system in the positive half cycle, because i 1 (t) = x 1 (t),i 2 (t) = x 8 (t), and the grid side is in stage P 1 , P 2 , P 3 and P 4 The battery side is in phase P 1 , P3 , P 5 and P 7 Output power. Here we take M i is x(t) in P i Internal pair i The time integral of , we get:

[0187]

[0188] In formula (30), M i It is the process variable matrix for calculating the output power of the H-bridge on both sides of the system. The matrix dimension is 8×1, M i (k) is the matrix M i The value of the kth position in , where: i = 1, 2, ..., 16; k = 1, 2, ..., 8, so we can get:

[0189]

[0190] In formula (31), P H1 is the average power generated by the H1 bridge on the grid side in the nth cycle of the system, P H2 is the average power emitted by the H2 bridge on the battery side in the nth cycle of the system;

[0191] Over the entire time scale, P H1 and P H2 It is always related to the state of the system in the nth cycle. The above formulas (23), (26), (30) and (31) constitute the discrete time domain mathematical model in this application.

[0192] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A modeling method for a bidirectional wireless power transmission system based on a unified composite working mode. It is characterized in that The modeling approach includes the following: Taking the bilateral LCC resonant topology bidirectional wireless power transmission system as the object, based on the modal analysis theory, according to the different output levels of the H-bridges on both sides, the basic working stages of the system modal are divided in detail; Define the first switch tube S of the system leading bridge arm 11 The driving signal u G11 The positive and negative cycles of the system are distinguished by u G11 When it is high level, the system is defined as positive half cycle. G11 When the voltage level is zero, the system is defined as a negative half-cycle, and the output voltage waveforms of the H1 bridge and the H2 bridge show odd symmetry in positive and negative cycles. The working mode of the system is named in sequence according to the circuit stages that appear in the half-cycle. exist When , the unified composite working mode Y of the system is recorded as PN / PO / PP / PO / ON / OO / OP / OO in the positive half cycle, and as NP / NO / NN / NO / OP / OO / ON / OO in the negative half cycle; exist When the unified composite working mode Y * In the positive half cycle, it is recorded as PP / PO / PN / PO / OP / OO / ON / OO, and in the negative half cycle, it is recorded as NN / NO / NP / NO / ON / OO / OP / OO; Among them, P represents the mode when the H-bridge outputs a positive level, N represents the mode when the H-bridge outputs a negative level, O represents the mode when the H-bridge outputs a zero level, and the " / " in the unified composite working mode represents the division of the basic working stage. The first letter before the " / " represents the output voltage of the H1 bridge, and the second letter represents the output voltage of the H2 bridge. is the external phase shift angle, i.e. S of the H2 bridge 21 The driving signal u of the tube G21 S relative to H1 bridge 11 The driving signal u of the tube G11 The phase shift angle between them; H1 bridge is the inverter bridge on the grid side, and H2 bridge is the inverter bridge on the battery side; Get the unified composite working modes Y and Y * The duration of each basic work stage; According to the physical structure of the bilateral LCC bidirectional wireless power transmission system, the state space model of each basic working stage is obtained. Combined with the unified composite working modal form, a unified discrete mathematical model equation is obtained to complete the discrete modeling of the bidirectional wireless power transmission system.

2. The modeling method of the bidirectional wireless power transmission system based on the unified composite working mode according to claim 1, It is characterized in that The basic working stages of the system mode are divided in detail to obtain that in the entire working process of the two-way wireless power transmission system, all possible working stages are PN, PP, PO, NN, NP, NO, ON, OP and OO. When the system works in the PN stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is -U bat ; When the system works in the PP stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is U bat ; When the system works in the PO stage, the output voltage of the H1 bridge is U dc , the output voltage of H2 bridge is zero; when the system works in the NN stage, the output voltage of H1 bridge is -U dc , the output voltage of H2 bridge is -U bat ; When the system works in the NP stage, the output voltage of the H1 bridge is -U dc , the output voltage of H2 bridge is U bat ; When the system works in the NO stage, the output voltage of the H1 bridge is -U dc , the output voltage of H2 bridge is zero; when the system works in the ON stage, the output voltage of H1 bridge is zero, and the output voltage of H2 bridge is -U bat ; When the system works in the OP stage, the output voltage of the H1 bridge is zero, and the output voltage of the H2 bridge is U bat ; When the system works in the OO stage, the output voltage of the H1 bridge is zero and the output voltage of the H2 bridge is zero.

3. The modeling method of the bidirectional wireless power transmission system based on the unified composite working mode according to claim 1, It is characterized in that exist When the system's positive half-cycle unified composite working mode Y: PN / PO / PP / PO / ON / OO / OP / OO, the action time of each basic working stage is expressed as t n1 ,t n2 ,t n3 ,t n4 ,t n5 ,t n6 ,t n7 and t n8 Indicated by Y All possible working modes of the system in the composite control under the condition, for those working stages that do not appear in the actual working mode, their action time is considered to be zero; Assume the operating frequency of the system is f s , then ω s =2πf s , the action time t of the basic working stage in the positive half-cycle unified composite working mode Y n1 ~t n8 And the system control variable operating frequency f, the internal phase shift angle α of the H1 bridge 1 、Internal phase shift angle α of H2 bridge 2 and the external phase shift angle of the H bridge on both sides The relationship between them is: 1)t n1 The expression is: 2)t n2 The expression is: 3)t n3 The expression is: 4)t n4 The expression is: 5)t n5 The expression is: 6)t n6 The expression is: 7)t n7 The expression is: 8)t n8 The expression is: Similarly, in When the system's positive half-cycle unified composite working mode Y * :The action time of each basic working stage of PP / PO / PN / PO / OP / OO / ON / OO is expressed as t m1 ,t m2 ,t m3 ,t m4 ,t m5 ,t m6 ,t m7 and t m8 Indicates that through Y * express All possible working modes of the system in the composite control under the condition, for those working stages that do not appear in the actual working mode, their action time is considered to be zero; the positive half-cycle unified composite working mode Y * The action time t of the basic work stage m1 ~t m8 And the system control variable operating frequency f, the internal phase shift angle α of the H1 bridge 1 、Internal phase shift angle α of H2 bridge 2 and the external phase shift angle of the H bridge on both sides The relationship between them is: 1)t m1 The expression is: 2)t m2 The expression is: 3)t m3 The expression is: 4)t m4 The expression is: 5)t m5 The expression is: 6)t m6 The expression is: 7)t m7 The expression is: 8)t m8 The expression is:

4. The modeling method of the bidirectional wireless power transmission system based on the unified composite working mode according to claim 1, It is characterized in that The construction process of the unified discrete mathematical model equation is: Step 3.1, the system structure is a bidirectional wireless power transmission system based on bilateral LCC resonance topology, and i 1 、u C1 、u Cp1 、i L1 、i L2 、u Cp2 、u C2 and i 2 is the state variable of the system, and its mathematical expression is: Where: i 1 is the current flowing through the series resonant inductor on the grid side; u C1 is the voltage of the parallel resonant capacitor on the grid side; u Cp1 is the voltage of the DC blocking capacitor in series on the grid side; i L1 is the current flowing through the magnetic coupling coil on the grid side; i L2 is the current flowing through the magnetic coupling coil on the battery side; u Cp2 is the voltage of the DC blocking capacitor connected in series on the battery side; u C2 is the voltage of the parallel resonant capacitor on the battery side; i 2 is the current flowing through the series resonant inductor on the battery side; Step 3.2, based on the circuit structure of the bidirectional wireless power transmission system with bilateral LCC resonant topology, Y and Y * The positive half cycle consists of 8 basic working stages, and the negative half cycle also consists of 8 basic working stages. The positive and negative cycles are odd-symmetrical to each other. In the whole working process, it includes 16 working stages in sequence. A unified discrete time model is established. * Or Y each working stage write the mathematical expression of the state space is: Among them, A s is the state matrix of the system, B s is the input control matrix of the system, P i Represents the basic working stage of the system. When the system works in the PN stage, P i =[1,-1] T ; During the PP stage, P i =[1,1] T ; During the PO phase, P i =[1,0] T ; During the NN stage, P i =[-1,-1] T ; In the NP stage, P i =[-1,1] T ; During the NO phase, P i =[-1,0] T ; During the ON phase, P i =[0,-1] T ; During the OP phase, P i =[0,1] T ; In the OO stage, P i =[0,0] T ; i represents the number of basic working stages in a cycle, and the input U of the system is written in matrix form, that is, Step 3.3, use formula (23) to get the unified composite working mode Y * Or the discrete time model of the switching state points of each basic working stage of Y: Among them, U i =UP i In formula (23), when i=1, the x n0 is the state variable x of the system n , that is: x n0 =x n When i=16, the system works for one cycle and the x n16 is the state variable x of the system n+1 , that is: x n16 =x n+1 , x n represents the state variable of the system at the beginning of the nth cycle, x n+1 Represents the state variable of the system at the beginning of the n+1th cycle. n to x n+1 During this period, the system switches state variables to x n1 、x n2 , …, x n15 , κ n is an organic combination of the control variables of the system, that is f ni (x n(i-1) , κ n ) represents the iterated function; ψ i is the matrix related to the zero-state response of the system; Step 3.4: Obtain the state variable x of the system at the beginning of the n+1th cycle from the iterative relationship in equation (23): n+1 The expression of the system is x when it is running in steady state n+1 =x n , and obtain the system state variable value x when the system is running stably nss The mathematical expression of is formula (26): x nss =[I 0 -F(k n )] -1 G(k n ,U i ) (26) In formula (26), F(κ n ) is the state matrix related to the initial state of the system, G(κ n , U i ) is the state matrix related to the system input; I 0 is the identity matrix; Step 3.5, use equation (30) to get the expression of the output power of the double-sided H-bridge: In formula (30), M i is the process variable matrix of the output power of the double-sided H-bridge, with a matrix dimension of 8×1, M i (k) is the matrix M i The value of the kth position in , where: i = 1, 2, ..., 16; k = 1, 2, ..., 8; in formula (31), P H1 is the average power generated by the H1 bridge on the grid side in the nth cycle of the system, P H2 is the average power generated by the H2 bridge on the battery side in the nth cycle of the system; T s is the system working cycle.

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