A bi-directional WPT cycloconverter system based on variable-topology bi-directional AC / AC

Abstract

The present invention discloses a bidirectional WPT AC-AC frequency conversion system based on a variable-topology bidirectional AC / AC system. The system comprises a variable-topology bidirectional AC / AC-1 unit, a wireless power transmission unit, and a variable-topology bidirectional AC / AC-2 unit, which are connected in sequence. The circuit has two energy transmission modes: forward energy transmission and reverse energy transmission. During forward energy transmission, the energy transmission path is: AB side → MN side of the variable-topology bidirectional AC / AC-1 unit → OP side of the wireless power transmission unit → variable-topology bidirectional AC / AC-2 unit → GH side; during reverse energy transmission, the energy transmission path is: GH side → OP side of the variable-topology bidirectional AC / AC-2 unit → MN side of the wireless power transmission unit → variable-topology bidirectional AC / AC-1 unit → AB side. The circuit of the present invention is capable of achieving efficient bidirectional wireless power transmission. Both the front and rear stages of the wireless power transmission circuit adopt a variable-topology bidirectional AC / AC solution to achieve a wireless power transmission frequency conversion output function, thereby improving system efficiency and reducing costs. The circuit is novel, reliable, and practical, and the control scheme is novel.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless power transmission, and in particular relates to a bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC. Background Art

[0002] Wireless power transmission frequency conversion circuits are widely used in rail transit, electric vehicles, mining, smart homes, and other fields. AC systems require power factor correction (PFC). Bridgeless PFC effectively improves system efficiency by eliminating the uncontrolled rectification stage. For AC input frequency conversion systems, direct AC / AC conversion eliminates the rectification stage, reducing costs while also significantly improving system efficiency. Utilizing both technologies significantly improves the efficiency of wireless power transmission frequency conversion circuits. Bidirectional wireless power transmission systems offer greater flexibility, enabling four-quadrant operation and expanding their application range. However, there are currently no reports of bidirectional wireless power transmission employing direct AC / AC PFC solutions using both the front and rear stages.

[0003] Existing AC input and output wireless power transmission solutions often involve diode-based power frequency rectification of the AC input, followed by power factor correction (PFC), followed by high-frequency inversion to excite the wireless power transmission transmitter coil. The wireless power transmission receiver coil receives the high-frequency AC, undergoes diode-based high-frequency rectification, and then undergoes inverter output to generate the power-frequency AC. Consequently, these existing solutions involve numerous steps and are inefficient. Summary of the Invention

[0004] The present invention provides a bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC, which is used to solve the technical problem of excessive AC-AC stages and low efficiency under the conditions of wireless power transmission technology. The present invention realizes bidirectional AC-AC energy transmission with fewer stages and higher efficiency.

[0005] The present invention provides a bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC, comprising a variable topology bidirectional AC / AC-1 unit, a wireless power transmission unit, and a variable topology bidirectional AC / AC-2 unit connected in sequence;

[0006] The variable topology bidirectional AC / AC-1 unit includes:

[0007] A first variable-topology LCL filter composed of a first inductor L11, a second inductor L12, and a first equivalent programmable capacitor C11. The first variable-topology LCL filter is composed of a fifth power electronic AC switch Q5 and a first capacitor C1 connected in series. The switching of the first equivalent programmable capacitor C11 is controlled by controlling the on and off of the fifth power electronic AC switch Q5, and the size of the first equivalent programmable capacitor C11 is adjusted by controlling the duty cycle of the fifth power electronic AC switch Q5.

[0008] a first bridge arm consisting of a first power electronic AC switch Q1 and a second power electronic AC switch Q2, wherein an intersection point between the first power electronic AC switch Q1 and the second power electronic AC switch Q2 is M; and

[0009] a second bridge arm formed by a third power electronic AC switch Q3 and a fourth power electronic AC switch Q4, wherein an intersection point between the third power electronic AC switch Q3 and the fourth power electronic AC switch Q4 is N;

[0010] One end of the first inductor L11 is connected to a first low-frequency AC The other end of the first inductor L11 is connected to point C, and point C is connected to one end of the first equivalent programmable capacitor C11, one end of the first power electronic AC switch Q1, and one end of the third power electronic AC switch Q3. Port B is connected to the other end of the first equivalent programmable capacitor C11 and one end of the second inductor L12, the other end of the second inductor L12 is connected to point D, and point D is connected to one end of the second power electronic AC switch Q2 and one end of the fourth power electronic AC switch Q4;

[0011] Furthermore, the variable-topology bidirectional AC / AC-2 unit includes:

[0012] a third bridge arm formed by a sixth power electronic AC switch S1 and a seventh power electronic AC switch S2, wherein an intersection point between the sixth power electronic AC switch S1 and the seventh power electronic AC switch S2 is O;

[0013] a fourth bridge arm formed by an eighth power electronic AC switch S3 and a ninth power electronic AC switch S4, wherein an intersection point between the eighth power electronic AC switch S3 and the ninth power electronic AC switch S4 is P; and

[0014] a second variable-topology LCL filter composed of a third inductor L21, a fourth inductor L22, and a second equivalent programmable capacitor C21; the second equivalent programmable capacitor C21 is composed of a tenth power electronic AC switch S5 and a second capacitor C2 connected in series; the switching of the second equivalent programmable capacitor C21 is controlled by controlling the on and off of the tenth power electronic AC switch S5; and the size of the second equivalent programmable capacitor C21 is adjusted by controlling the duty cycle of the tenth power electronic AC switch S5;

[0015] One end of the third inductor L21 is connected to the intersection E of the sixth power electronic AC switch S5 and the eighth power electronic AC switch S3, and the other end of the third inductor L21 is connected to the second low-frequency AC Point G is connected to one end of the second equivalent programmable capacitor C21, and the other end of the second equivalent programmable capacitor C21 is connected to one end of the seventh power electronic AC switch S2 and one end of the ninth power electronic AC switch S4 respectively. Point F is connected to one end of the fourth inductor L22, and the other end of the fourth inductor L22 is connected to the second low-frequency AC The port H point.

[0016] Furthermore, the first high frequency AC on one side of the wireless power transmission unit Connected to the MN of the variable topology bidirectional AC / AC-1 unit, the second high frequency AC on the other side of the wireless power transmission unit Connected to the OP of the variable topology bidirectional AC / AC-2 unit;

[0017] During forward energy transfer, that is, when energy is transferred from AB to GH, the variable-topology bidirectional AC / AC-1 unit performs power factor correction control while performing direct AC / AC conversion, and the wireless power transmission unit is used to transfer energy from MN to OP, and the variable-topology bidirectional AC / AC-2 unit performs direct AC / AC voltage and frequency conversion output on the GH side;

[0018] When energy is transferred in the reverse direction, that is, when energy is transferred from GH to AB, the variable-topology bidirectional AC / AC-2 unit performs power factor correction control while performing direct AC / AC conversion, and the wireless power transmission unit is used to transfer energy from OP to MN, and the variable-topology bidirectional AC / AC-1 unit performs direct AC / AC voltage and frequency conversion on the AB side output.

[0019] Furthermore, when energy is transferred in the forward direction, the fifth power electronic AC switch Q5 of the variable topology bidirectional AC / AC-1 unit is always disconnected, the first capacitor C1 is not connected to the circuit, and the first variable topology structure LCL filter is changed to a dual-inductor structure. The variable topology bidirectional AC / AC-2 unit converts the first high-frequency AC Converted into a second low frequency AC Output;

[0020] When energy is transferred in reverse, the tenth power electronic AC switch S5 of the variable topology bidirectional AC / AC-2 unit is always disconnected, the second capacitor C2 is not connected to the circuit, and the second variable topology structure LCL filter becomes a dual-inductor structure. When energy is transferred in reverse, the variable topology bidirectional AC / AC-1 unit converts the second high-frequency AC Convert to the first low frequency Output.

[0021] Furthermore, the operating conditions of the variable topology bidirectional AC / AC-1 unit include:

[0022] Working condition 1-1: is positive and The current flows from top to bottom;

[0023] Working conditions 1-2: is positive and The current flows from bottom to top;

[0024] Working conditions 1-3: is negative and The current flows from top to bottom;

[0025] Working conditions 1-4: is negative and The current flows from bottom to top;

[0026] Among them, working condition 1-1, working condition 1-2, working condition 1-3 and working condition 1-4 each have sub-working condition a: the first inductor L11 and the second inductor L12 are both charged, and sub-working condition b: the first inductor L11 and the second inductor L12 are both discharged;

[0027] Working condition 1-1-a sub-working condition: is positive, Q1 and Q2 are closed, L11 and L12 are positively charged; sub-condition 1-1-b of working condition: is positive, Q1 and Q4 are closed, L11 and L12 continue to discharge, Current from top to bottom; working condition 1-2-a sub-working condition: is positive, Q3 and Q4 are closed, L11 and L12 are positively charged; sub-condition 1-2-b: is positive, Q2 and Q3 are closed, L11 and L12 are discharged in the forward direction. Current from bottom to top; working condition 1-3-a sub-condition: If the voltage is negative, Q1 and Q2 are closed, and L11 and L12 are reversely charged; sub-condition 1-3-b: is negative, Q2 and Q3 are closed, L11 and L12 are discharged in reverse direction. Current from top to bottom; working condition 1-4-a sub-working condition: If the voltage is negative, Q3 and Q4 are closed, and L11 and L12 are reversely charged; sub-condition 1-4-b: is negative, Q1 and Q4 are closed, L11 and L12 are discharged in reverse direction. The current flows from bottom to top;

[0028] During forward energy transmission, the power factor correction and direct AC / AC conversion are performed by controlling the various operating conditions of the variable topology bidirectional AC / AC-1 unit, and the MN side of the wireless power transmission unit is stimulated.

[0029] Furthermore, the operating conditions of the variable topology bidirectional AC / AC-2 unit include:

[0030] Working condition 2-1: is positive and The current flows from top to bottom;

[0031] Working condition 2-2: is positive and The current flows from bottom to top;

[0032] Working conditions 2-3: is negative and The current flows from top to bottom;

[0033] Working conditions 2-4: is negative and The current flows from bottom to top;

[0034] Among them, working condition 2-1, working condition 2-2, working condition 2-3 and working condition 2-4 each have sub-working condition a: the third inductor L21 and the fourth inductor L22 are both charged, and sub-working condition b: the third inductor L21 and the fourth inductor L22 are both discharged;

[0035] Working condition 2-1-a sub-working condition: is positive, S1 and S2 are closed, L21 and L22 are positively charged; sub-condition 2-1-b: is positive, S1 and S4 are closed, L21 and L22 continue to discharge, Current from top to bottom; sub-condition 2-2-a: is positive, S3 and S4 are closed, L21 and L22 are positively charged; sub-condition 2-2-b: is positive, S2 and S3 are closed, L21 and L22 discharge in the forward direction. Current from bottom to top; sub-condition 2-3-a: When the voltage is negative, S1 and S2 are closed, and L21 and L22 are reversely charged; sub-condition 2-3-b: is negative, S2 and S3 are closed, L21 and L22 discharge in reverse direction. Current from top to bottom; working condition 2-4-a sub-condition: If the voltage is negative, S3 and S4 are closed, and L21 and L22 are charged in reverse; sub-condition 2-4-b: When the voltage is negative, S1 and S4 are closed, and L21 and L22 discharge in reverse direction; The current flows from bottom to top;

[0036] During reverse energy transmission, the power factor correction and direct AC / AC conversion are performed by controlling the switching of various working conditions of the variable topology bidirectional AC / AC-2 unit, and the OP side of the wireless power transmission unit is stimulated.

[0037] Furthermore, when energy is transferred in the forward direction, the variable topology bidirectional AC / AC-2 unit controls the duty cycle of the tenth power electronic AC switch S5 to program the size of the second equivalent programmable capacitor C21, and the second variable topology LCL filter is " The LCL filter is a capacitor-programmable LCL filter that is used to achieve active impedance matching under different load conditions.

[0038] Furthermore, when energy is transferred in the reverse direction, the variable topology bidirectional AC / AC-1 unit controls the duty cycle of the fifth power electronic AC switch Q5 to program the size of the first equivalent programmable capacitor C11. The first variable topology LCL filter is " The LCL filter is a capacitor-programmable LCL filter that is used to achieve active impedance matching under different load conditions.

[0039] The bidirectional WPT AC-AC frequency conversion system based on variable topology bidirectional AC / AC of the present application has the ability to realize bidirectional wireless power transmission. The front and rear stages of the wireless power transmission of the circuit of the present application both adopt a direct AC / AC solution to realize the wireless power transmission frequency conversion output function, thereby improving system efficiency and reducing costs. The circuit is novel, reliable, and practical, and the control scheme is novel. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0041] Figure 1 This is a block diagram of the multifunctional circuit structure of bidirectional bridgeless AC / AC wireless power transmission based on the present invention;

[0042] Figure 2This is a block diagram of the bidirectional WPT AC-AC frequency conversion system based on variable topology bidirectional AC / AC of the present invention;

[0043] Figure 3 Schematic diagram of the main circuit topology of the bidirectional WPT AC-AC frequency conversion system based on variable topology bidirectional AC / AC of the present invention;

[0044] Figure 4 This is a schematic diagram of the main circuit topology of the system when energy is transferred in the forward direction;

[0045] Figure 5 This is a schematic diagram of the main circuit topology of the system when energy is transferred in reverse;

[0046] Figure 6 This is the equivalent main circuit topology diagram of the time-varying bidirectional AC / AC-1 unit with forward energy transfer;

[0047] Figure 7 This is the working diagram of the variable topology bidirectional AC / AC-1 unit in the forward energy transfer mode 1-1, that is, the variable topology bidirectional AC / AC-1 unit is is positive, Working diagram when current flows from top to bottom (↓);

[0048] Figure 8 This is the working diagram of the variable topology bidirectional AC / AC-1 unit under the condition 1-2 of energy forward transfer, that is, the variable topology bidirectional AC / AC-1 unit under the condition is positive, Working diagram when the current flows from bottom to top (↑);

[0049] Figure 9 The schematic diagram of the working conditions 1-3 of the variable topology bidirectional AC / AC-1 unit in the forward energy transfer mode is shown in FIG. is negative, Working diagram when current flows from top to bottom (↓);

[0050] Figure 10 The schematic diagram of the working conditions 1-4 of the variable topology bidirectional AC / AC-1 unit in the forward energy transfer mode is shown in FIG. is negative, Working diagram when the current flows from bottom to top (↑);

[0051] Figure 11 The equivalent main circuit topology diagram of the bidirectional AC / AC-2 unit with time-varying topology for forward energy transfer;

[0052] Figure 12 The equivalent main circuit topology diagram of the bidirectional AC / AC-1 unit with time-varying topology for reverse energy transfer;

[0053] Figure 13 The equivalent main circuit topology of the bidirectional AC / AC-2 unit with time-varying topology for reverse energy transfer;

[0054] Figure 14 This is a schematic diagram of the working condition 2-1 of the variable topology bidirectional AC / AC-2 unit with reverse energy transfer, that is, the variable topology bidirectional AC / AC-2 unit is For positive, Working diagram when current flows from top to bottom (↓);

[0055] Figure 15 This is the working diagram of the variable topology bidirectional AC / AC-2 unit 2-2 when energy is transferred in reverse direction. For positive, Working diagram when current flows from bottom to top (↑);

[0056] Figure 16 The schematic diagram of the working condition 2-3 of the variable topology bidirectional AC / AC-2 unit when energy is transferred in reverse direction is shown. is negative, Working diagram when current flows from top to bottom (↓);

[0057] Figure 17 The schematic diagram of the working condition 2-4 of the variable topology bidirectional AC / AC-2 unit when energy is transferred in reverse direction is shown. is negative, Working diagram when current flows from bottom to top (↑);

[0058] Figure 18 This is a circuit diagram of the bidirectional WPT AC-AC frequency conversion system circuit based on the variable topology bidirectional AC / AC of the present invention when a power electronic AC switch based on MOSFET is used. DETAILED DESCRIPTION

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0060] Figure 1This is a block diagram of a multifunctional circuit structure for wireless power transmission based on bidirectional bridgeless AC / AC, which includes, in sequence, a low-frequency diode rectifier unit for rectifying low-frequency AC into DC, a power factor correction unit for achieving power factor correction, an inverter excitation unit for achieving high-frequency inverter excitation, a wireless power transmission unit for achieving wireless power transmission, a high-frequency diode rectifier unit for rectifying high-frequency AC into DC, a DC-DC unit for achieving voltage stabilization, and an inverter output unit.

[0061] The existing solution has many unit levels, high cost and low efficiency, while the circuit topology of the present invention is simple, low cost and high efficiency.

[0062] Figure 2 This is a block diagram of the bidirectional WPT AC-AC frequency conversion system based on variable topology bidirectional AC / AC of the present invention;

[0063] The present invention comprises three units connected in sequence: a variable topology bidirectional AC / AC-1 unit, a wireless power transmission unit, and a variable topology bidirectional AC / AC-2 unit;

[0064] The circuit of the present invention has two working conditions: forward energy transmission and reverse energy transmission. During forward energy transmission, the time-varying topology bidirectional AC / AC-1 unit completes power factor correction while realizing direct AC / AC excitation of the wireless power transmission unit. The wireless power transmission unit realizes wireless power transmission to transfer energy from MN to OP, and the variable topology bidirectional AC / AC-2 unit realizes direct AC / AC frequency conversion and voltage conversion output. During reverse energy transmission, the time-varying topology bidirectional AC / AC-2 unit completes power factor correction while realizing direct AC / AC excitation of the wireless power transmission unit. The wireless power transmission unit realizes wireless power transmission to transfer energy from OP to MN, and the variable topology bidirectional AC / AC-1 unit realizes direct AC / AC frequency conversion and voltage conversion output.

[0065] In the forward energy transfer, that is, the energy is transferred from the AB side Transmitted to GH side When the input end of the variable topology bidirectional AC / AC-1 unit is the AB side The output terminal MN of the variable-topology bidirectional AC / AC-1 unit is connected to the primary input terminal of the wireless power transmission unit. In this case, the primary input terminal of the wireless power transmission unit is MN. The secondary output terminal OP of the wireless power transmission unit is connected. The secondary output terminal OP of the wireless power transmission unit is connected to the input terminal of the variable-topology bidirectional AC / AC-2 unit. The output terminal of the variable-topology bidirectional AC / AC-2 unit is the system output of the forward energy transmission of the present invention, and outputs variable-voltage and variable-frequency AC.

[0066] In reverse energy transmission, energy is transferred from the GH side to the Transmitted to AB side When the input end of the variable topology bidirectional AC / AC-2 unit is the GH side The input terminal OP of the variable topology bidirectional AC / AC-2 unit is connected to the primary input terminal of the wireless power transmission unit. At this time, the primary input terminal of the wireless power transmission unit is OP; the secondary output terminal MN of the wireless power transmission unit is connected, and the secondary output terminal OP of the wireless power transmission unit is connected to the input terminal of the variable topology bidirectional AC / AC-2 unit. The output terminal AB of the variable topology bidirectional AC / AC-1 unit is the system output of the forward energy transmission of the present invention, and outputs variable voltage and variable frequency AC;

[0067] During forward energy transmission, the variable-topology bidirectional AC / AC-1 unit performs power factor correction while simultaneously achieving direct AC / AC conversion to complete variable-frequency high-frequency excitation on the MN side of wireless power transmission. At this time, the variable-topology bidirectional AC / AC-1 unit uses a power factor correction control algorithm while completing low-frequency / high-frequency AC / AC conversion. During forward energy transmission, the variable-topology bidirectional AC / AC-2 unit achieves high-frequency / low-frequency AC / AC voltage and frequency conversion on the GH side output.

[0068] During reverse energy transmission, the variable-topology bidirectional AC / AC-2 unit performs power factor correction while achieving direct AC / AC conversion to complete variable-frequency high-frequency excitation on the OP side of wireless power transmission. At this time, the variable-topology bidirectional AC / AC-2 unit uses a power factor correction control algorithm while completing low-frequency / high-frequency AC / AC conversion. During reverse energy transmission, the variable-topology bidirectional AC / AC-1 unit achieves high-frequency / low-frequency AC / AC voltage and frequency conversion on the AB side output.

[0069] Figure 3 Schematic diagram of the main circuit topology of the bidirectional WPT AC-AC frequency conversion system based on variable topology bidirectional AC / AC of the present invention;

[0070] The present invention comprises three units connected in sequence: a variable topology bidirectional AC / AC-1 unit, a wireless power transmission unit, and a variable topology bidirectional AC / AC-2 unit;

[0071] The variable-topology bidirectional AC / AC-1 unit includes:

[0072] A first variable-topology LCL filter composed of a first inductor L11, a second inductor L12, and a first equivalent programmable capacitor C11. The first variable-topology LCL filter is composed of a fifth power electronic AC switch Q5 and a first capacitor C1 connected in series. The switching of the first equivalent programmable capacitor C11 is controlled by controlling the on and off of the fifth power electronic AC switch Q5, and the size of the first equivalent programmable capacitor C11 is adjusted by controlling the duty cycle of the fifth power electronic AC switch Q5.

[0073] a first bridge arm consisting of a first power electronic AC switch Q1 and a second power electronic AC switch Q2, wherein an intersection point between the first power electronic AC switch Q1 and the second power electronic AC switch Q2 is M; and

[0074] a second bridge arm formed by a third power electronic AC switch Q3 and a fourth power electronic AC switch Q4, wherein an intersection point between the third power electronic AC switch Q3 and the fourth power electronic AC switch Q4 is N;

[0075] One end of the first inductor L11 is connected to a first low-frequency AC The other end of the first inductor L11 is connected to point C, and point C is connected to one end of the first equivalent programmable capacitor C11, one end of the first power electronic AC switch Q1, and one end of the third power electronic AC switch Q3. Port B is connected to the other end of the first equivalent programmable capacitor C11 and one end of the second inductor L12, the other end of the second inductor L12 is connected to point D, and point D is connected to one end of the second power electronic AC switch Q2 and one end of the fourth power electronic AC switch Q4;

[0076] The variable-topology bidirectional AC / AC-2 unit includes:

[0077] a third bridge arm formed by a sixth power electronic AC switch S1 and a seventh power electronic AC switch S2, wherein an intersection point between the sixth power electronic AC switch S1 and the seventh power electronic AC switch S2 is O;

[0078] a fourth bridge arm formed by an eighth power electronic AC switch S3 and a ninth power electronic AC switch S4, wherein an intersection point between the eighth power electronic AC switch S3 and the ninth power electronic AC switch S4 is P; and

[0079] a second variable-topology LCL filter composed of a third inductor L21, a fourth inductor L22, and a second equivalent programmable capacitor C21; the second equivalent programmable capacitor C21 is composed of a tenth power electronic AC switch S5 and a second capacitor C2 connected in series; the switching of the second equivalent programmable capacitor C21 is controlled by controlling the on and off of the tenth power electronic AC switch S5; and the size of the second equivalent programmable capacitor C21 is adjusted by controlling the duty cycle of the tenth power electronic AC switch S5;

[0080] One end of the third inductor L21 is connected to the intersection E of the sixth power electronic AC switch S5 and the eighth power electronic AC switch S3, and the other end of the third inductor L21 is connected to the second low-frequency AC Point G is connected to one end of the second equivalent programmable capacitor C21, and the other end of the second equivalent programmable capacitor C21 is connected to one end of the seventh power electronic AC switch S2 and one end of the ninth power electronic AC switch S4 respectively. Point F is connected to one end of the fourth inductor L22, and the other end of the fourth inductor L22 is connected to the second low-frequency AC Port H point.

[0081] The first high-frequency AC on one side of the wireless power transmission unit Connected to the MN of the variable topology bidirectional AC / AC-1 unit, the second high frequency AC on the other side of the wireless power transmission unit Connected to the OP of the variable topology bidirectional AC / AC-2 unit;

[0082] During forward energy transfer, that is, when energy is transferred from AB to GH, the variable-topology bidirectional AC / AC-1 unit performs power factor correction control while performing direct AC / AC conversion, and the wireless power transmission unit is used to transfer energy from MN to OP, and the variable-topology bidirectional AC / AC-2 unit performs direct AC / AC voltage and frequency conversion output on the GH side;

[0083] During reverse energy transfer, that is, when energy is transferred from GH to AB, the variable-topology bidirectional AC / AC-2 unit performs power factor correction control while performing direct AC / AC conversion, and the wireless power transmission unit is used to transfer energy from OP to MN, and the variable-topology bidirectional AC / AC-1 unit performs direct AC / AC voltage and frequency conversion output on the AB side;

[0084] When energy is transferred in the forward direction, the fifth power electronic AC switch Q5 of the variable topology bidirectional AC / AC-1 unit is always disconnected, the first capacitor C1 is not connected to the circuit, and the first variable topology structure LCL filter is changed to a dual-inductor structure. The variable topology bidirectional AC / AC-2 unit converts the first high-frequency AC Converted into a second low frequency AC Output;

[0085] When energy is transferred in the forward direction, the variable topology bidirectional AC / AC-2 unit controls the duty cycle of the tenth power electronic AC switch S5 to program the size of the second equivalent programmable capacitor C21. The second variable topology LCL filter is " Type "capacitor programmable LCL filter, used to meet active impedance matching under different load conditions;

[0086] When energy is transferred in reverse, the variable topology bidirectional AC / AC-1 unit controls the duty cycle of the fifth power electronic AC switch Q5 to program the size of the first equivalent programmable capacitor C11. The first variable topology LCL filter is " Type "capacitor programmable LCL filter, used to meet active impedance matching under different load conditions;

[0087] When energy is transferred in reverse, the tenth power electronic AC switch S5 of the variable topology bidirectional AC / AC-2 unit is always disconnected, the second capacitor C2 is not connected to the circuit, and the second variable topology structure LCL filter becomes a dual-inductor structure. When energy is transferred in reverse, the variable topology bidirectional AC / AC-1 unit converts the second high-frequency AC Convert to the first low frequency Output.

[0088] The wireless power transmission unit adopts a series-parallel topology, and can be used in any appropriate topology in practice, which is selected and designed according to actual needs;

[0089] The system of the present invention exhibits symmetry, including circuit topology symmetry and operating condition symmetry. Circuit topology symmetry: The variable-topology bidirectional AC / AC-1 unit is symmetrical with the variable-topology bidirectional AC / AC-2 unit, and the wireless power transmission is inherently symmetrical. Operating condition symmetry: Forward and reverse energy transmission are symmetrical.

[0090] Figure 4 This is a schematic diagram of the main circuit topology of the system when energy is transferred in the forward direction;

[0091] During forward energy transfer, energy is transferred from AB to GH. The fifth power electronic AC switch Q5 of the variable-topology bidirectional AC / AC-1 unit is always disconnected, the first capacitor C1 is not connected to the circuit, and the first variable-topology LCL filter is changed to a dual-inductor structure. The variable-topology bidirectional AC / AC-1 unit performs power factor correction while achieving direct AC-AC conversion from low-frequency AC to high-frequency AC, providing high-frequency excitation to the MN end of the wireless power transmission.

[0092] When energy is transferred in the forward direction, the tenth power electronic AC switch S5 of the variable topology bidirectional AC / AC-2 unit is controlled. By controlling the duty cycle of the tenth power electronic AC switch S5, the programmable control of the second equivalent programmable capacitor C21 is realized. The second variable topology LCL filter becomes The variable-topology bidirectional AC / AC-2 unit realizes direct AC-AC conversion of high-frequency AC into low-frequency AC output, and completes active impedance matching under different load conditions by controlling the second equivalent programmable capacitor C21.

[0093] Figure 5This is a schematic diagram of the main circuit topology of the system when energy is transferred in reverse;

[0094] During reverse energy transfer, energy is transferred from GH to AB. The tenth power electronic AC switch S5 of the variable-topology bidirectional AC / AC-2 unit is always disconnected, the second capacitor C2 is not connected to the circuit, and the second variable-topology LCL filter is changed to a dual-inductor structure. The variable-topology bidirectional AC / AC-2 unit completes power factor correction while achieving direct AC-AC conversion from low-frequency AC to high-frequency AC, providing high-frequency excitation to the OP end of the wireless power transmission.

[0095] When energy is transferred in reverse, the fifth power electronic AC switch Q5 of the variable topology bidirectional AC / AC-1 unit is controlled. By controlling the duty cycle of the fifth power electronic AC switch Q5, the programmable capacitance of the first equivalent programmable capacitor C11 is controlled. The first variable topology LCL filter becomes The variable-topology bidirectional AC / AC-1 unit realizes direct AC-AC conversion of high-frequency AC into low-frequency AC output, and completes active impedance matching under different load conditions by controlling the first equivalent programmable capacitor C11.

[0096] Figure 6 This is the equivalent main circuit topology diagram of the time-varying bidirectional AC / AC-1 unit with forward energy transfer;

[0097] During forward energy transfer, Q5 of the variable-topology bidirectional AC / AC-1 unit is always disconnected, and C1 is not connected to the circuit. The equivalent main circuit consists of L11, L12, and Q1 to Q4. Q1 and Q2 form one bridge arm with intersection M, and Q3 and Q4 form another bridge arm with intersection N. Preferably, L11 = L12.

[0098] The forward transmission time-varying topology bidirectional AC / AC-1 unit serves as the excitation source of the wireless power transmission unit and performs two functions at the same time: power factor correction and direct AC / AC excitation, that is, it is required to complete power factor correction control and direct AC / AC conversion control but does not necessarily require the realization of sinusoidal waveform output; the reverse transmission time-varying topology bidirectional AC / AC-1 unit realizes the high-frequency / low-frequency direct AC / AC conversion and frequency conversion AB side output.

[0099] Figure 7-10 The various operating conditions of the time-varying topology bidirectional AC / AC-1 unit with forward energy transfer are as follows:

[0100] Figure 7 This is the working diagram of the variable topology bidirectional AC / AC-1 unit in the forward energy transfer mode 1-1, that is, the variable topology bidirectional AC / AC-1 unit is is positive, Working diagram when current flows from top to bottom (↓);

[0101] Figure 7 (a) in is positive, Q1 and Q2 are closed, and L11 and L12 are charged in the positive direction; Figure 7 (b) in the is positive, Q1 and Q4 are closed, L11 and L12 continue to discharge, The current flows from top to bottom (↓).

[0102] Figure 8 This is the working diagram of the variable topology bidirectional AC / AC-1 unit under the condition 1-2 of energy forward transfer, that is, the variable topology bidirectional AC / AC-1 unit under the condition For positive, Working diagram when current flows from bottom to top (↑);

[0103] Figure 8 (a) in is positive, Q3 and Q4 are closed, and L11 and L12 are positively charged; Figure 8 (b) in the is positive, Q2 and Q3 are closed, L11 and L12 are discharged in the forward direction. The current flows from bottom to top (↑).

[0104] Figure 9 The schematic diagram of the working conditions 1-3 of the variable topology bidirectional AC / AC-1 unit in the forward energy transfer mode is shown in FIG. is negative, Working diagram when current flows from top to bottom (↓);

[0105] Figure 9 (a) in is negative, Q1 and Q2 are closed, and L11 and L12 are reversely charged; Figure 9 (b) in the is negative, Q2 and Q3 are closed, L11 and L12 are discharged in reverse direction. The current flows from top to bottom (↓).

[0106] Figure 10 The schematic diagram of the working conditions 1-4 of the variable topology bidirectional AC / AC-1 unit in the forward energy transfer mode is shown in FIG. is negative, Working diagram when current flows from bottom to top (↑);

[0107] Figure 10 (a) in is negative, Q3 and Q4 are closed, and L11 and L12 are reversely charged; Figure 10 (b) in the When the voltage is negative, Q1 and Q4 are closed, and L11 and L12 discharge in reverse direction; The current flows from bottom to top (↑).

[0108] During forward energy transmission, power factor correction and direct AC / AC conversion are achieved by controlling the various operating conditions of the variable topology bidirectional AC / AC-1 unit, and the excitation of the MN side of the wireless power transmission unit is realized. With input current In phase, because the forward transmission time-varying topology bidirectional AC / AC-1 unit also requires direct AC / AC excitation, switching frequency conversion control schemes such as hysteresis control are not suitable. Direct AC / AC conversion control does not require sinusoidal waveform output. The forward transmission time-varying topology bidirectional AC / AC-1 unit achieves high-frequency / low-frequency direct AC / AC conversion and frequency conversion on the AB side of the output.

[0109] Figure 11 The equivalent main circuit topology diagram of the bidirectional AC / AC-2 unit with time-varying topology for forward energy transfer;

[0110] Energy forward transfer time-varying topology bidirectional AC / AC-2 unit converts high frequency AC Converted to low frequency AC Output; control S1~S4 to complete direct AC-AC conversion, using direction-variable interactive rectification control, that is, In the positive half cycle, S1~S4 are rectified and controlled to make the output of port EF positive. In the negative half cycle, rectification control is implemented on S1~S4 to make the output of port EF negative;

[0111] The energy forward transfer time-varying topology bidirectional AC / AC-2 unit controls the duty cycle of S5 to achieve programmable size of the second equivalent programmable capacitor C21, and the filter becomes The LCL filter with programmable capacitor can meet the active impedance matching under different load conditions.

[0112] Figure 12 The equivalent main circuit topology diagram of the bidirectional AC / AC-1 unit with time-varying topology for reverse energy transfer;

[0113] Energy reverse transfer time-varying topology bidirectional AC / AC-1 unit converts high frequency AC Convert to low frequency Output; Q1~Q4 are controlled to complete direct AC-AC conversion, using direction-variable interactive rectification control, that is, In the positive half cycle, the rectification control is implemented on S1~S4 to make the output of port CD positive. In the negative half cycle, rectification control is implemented on S1~S4 to make the output of port CD negative;

[0114] The energy reverse transfer time-varying topology bidirectional AC / AC-1 unit controls Q5 and realizes the first equivalent programmable capacitor C11 programmable by controlling the duty cycle of Q5, and the filter becomes a capacitor programmable Type LCL filter to meet active impedance matching under different load conditions.

[0115] Figure 13 This is the equivalent main circuit topology diagram of the bidirectional AC / AC-2 unit with time-varying topology for reverse energy transfer.

[0116] When energy is transferred in the reverse direction, the variable-topology bidirectional AC / AC-2 unit realizes the excitation function of the wireless power transmission unit. The equivalent main circuit is composed of L11, L12 and S1 to S4. S1 and S2 form one bridge arm with the intersection point O, and S3 and S4 form another bridge arm with the intersection point P.

[0117] The reverse transmission time-varying topology bidirectional AC / AC-2 unit, as the excitation source of the wireless power transmission unit, completes two functions at the same time: power factor correction and direct AC / AC excitation, that is, it is required to complete power factor correction control and direct AC / AC conversion control but does not necessarily require the realization of sinusoidal waveform output; the forward transmission time-varying topology bidirectional AC / AC-2 unit realizes the high-frequency / low-frequency direct AC / AC conversion and frequency conversion GH-side output.

[0118] Figure 14-17 Schematic diagram of various operating conditions of the time-varying topology bidirectional AC / AC-2 unit with reverse energy transfer.

[0119] Figure 14 This is a schematic diagram of the working condition 2-1 of the variable topology bidirectional AC / AC-2 unit with reverse energy transfer, that is, the variable topology bidirectional AC / AC-2 unit is For positive, Working diagram when current flows from top to bottom (↓);

[0120] Figure 14 (a) in is positive, S1 and S2 are closed, and L21 and L22 are charged in the positive direction; Figure 14 (b) in the is positive, S1 and S4 are closed, L21 and L22 continue to discharge, The current flows from top to bottom (↓).

[0121] Figure 15 This is the working diagram of the variable topology bidirectional AC / AC-2 unit 2-2 when energy is transferred in reverse direction. For positive, Working diagram when current flows from bottom to top (↑);

[0122] Figure 15 (a) in is positive, S3 and S4 are closed, and L21 and L22 are charged in the positive direction; Figure 15 (b) in the is positive, S2 and S3 are closed, L21 and L22 discharge in the forward direction. The current flows from bottom to top (↑).

[0123] Figure 16 The schematic diagram of the working condition 2-3 of the variable topology bidirectional AC / AC-2 unit when energy is transferred in reverse direction is shown. is negative, Working diagram when current flows from top to bottom (↓);

[0124] Figure 16 (a) in is negative, S1 and S2 are closed, and L21 and L22 are charged in reverse; Figure 16 (b) in the is negative, S2 and S3 are closed, L21 and L22 discharge in reverse direction. The current flows from top to bottom (↓).

[0125] Figure 17 The schematic diagram of the working condition 2-4 of the variable topology bidirectional AC / AC-2 unit when energy is transferred in reverse direction is shown. is negative, Working diagram when the current flows from bottom to top (↑);

[0126] Figure 17 (a) in is negative, S3 and S4 are closed, and L21 and L22 are charged in reverse; Figure 17 (b) in the When the voltage is negative, S1 and S4 are closed, and L21 and L22 discharge in reverse direction; The current flows from bottom to top (↑).

[0127] During reverse energy transmission, power factor correction and direct AC / AC conversion are achieved by controlling the various operating conditions of the variable topology bidirectional AC / AC-2 unit, and the excitation of the OP side of the wireless power transmission unit is achieved. With reverse input current In phase, since the reverse transmission time-varying topology bidirectional AC / AC-2 unit also requires direct AC / AC excitation, variable frequency control schemes such as hysteresis control are not suitable. Direct AC / AC conversion control does not require sinusoidal waveform output. The forward transmission time-varying topology bidirectional AC / AC-2 unit achieves high-frequency / low-frequency direct AC / AC conversion and variable frequency GH-side output.

[0128] Figure 18 This is a schematic diagram of the main circuit topology of the system when energy is transferred in the forward direction;

[0129] During forward energy transfer, energy is transferred from AB to GH. Q5 of the variable-topology bidirectional AC / AC-1 unit is always disconnected, C1 is not connected to the circuit, and the first variable-topology LCL filter is changed to a dual-inductor structure. The variable-topology bidirectional AC / AC-1 unit completes power factor correction while achieving direct AC-AC conversion from low-frequency AC to high-frequency AC, providing high-frequency excitation to the MN end of the wireless power transmission.

[0130] When the energy is transferred in the forward direction, the S5 of the variable topology bidirectional AC / AC-2 unit is controlled, and the duty cycle of S5 is used to control the programmable value of the second equivalent programmable capacitor C21. The second variable topology LCL filter becomes The variable-topology bidirectional AC / AC-2 unit realizes direct AC-AC conversion from high-frequency AC to low-frequency AC output, and completes active impedance matching under different load conditions by controlling the equivalent programmable capacitor C21.

[0131] Figure 18 The present invention discloses a circuit in which a bidirectional WPT AC-AC frequency conversion system circuit based on a variable topology bidirectional AC / AC adopts a power electronic AC switch based on MOSFET.

[0132] While the wireless power transfer unit shown in the figure uses a series-parallel topology, any suitable topology can be used in practice, with the specific choice depending on actual needs. Q1-Q5 and S1-S5 are power electronic AC switches. MOSFET-based power electronic AC switches are preferred due to their low on-state voltage drop and easy-to-drive characteristics. Each shown in the figure is composed of two identical metal-oxide semiconductor field-effect transistors (MOSFETs) connected in reverse series, with the source of the top transistor connected to the drain of the bottom transistor. The drain of the top transistor and the source of the bottom transistor serve as the main current ports, and the gate drive control of the top and bottom transistors is separate.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC, characterized in that: It includes a variable topology bidirectional AC / AC-1 unit, a wireless power transmission unit, and a variable topology bidirectional AC / AC-2 unit connected in sequence; The variable topology bidirectional AC / AC-1 unit includes: A first variable-topology LCL filter composed of a first inductor L11, a second inductor L12, and a first equivalent programmable capacitor C11. The first variable-topology LCL filter is composed of a fifth power electronic AC switch Q5 and a first capacitor C1 connected in series. The switching of the first equivalent programmable capacitor C11 is controlled by controlling the on and off of the fifth power electronic AC switch Q5, and the size of the first equivalent programmable capacitor C11 is adjusted by controlling the duty cycle of the fifth power electronic AC switch Q5. a first bridge arm consisting of a first power electronic AC switch Q1 and a second power electronic AC switch Q2, wherein an intersection point between the first power electronic AC switch Q1 and the second power electronic AC switch Q2 is M; and a second bridge arm formed by a third power electronic AC switch Q3 and a fourth power electronic AC switch Q4, wherein an intersection point between the third power electronic AC switch Q3 and the fourth power electronic AC switch Q4 is N; One end of the first inductor L11 is connected to a first low-frequency AC The other end of the first inductor L11 is connected to point C, and point C is connected to one end of the first equivalent programmable capacitor C11, one end of the first power electronic AC switch Q1, and one end of the third power electronic AC switch Q3. Port point B is connected to the other end of the first equivalent programmable capacitor C11 and one end of the second inductor L12. The other end of the second inductor L12 is connected to point D. Point D is connected to one end of the second power electronic AC switch Q2 and one end of the fourth power electronic AC switch Q4.

2. A bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC according to claim 1, characterized in that: The variable topology bidirectional AC / AC-2 unit includes: a third bridge arm formed by a sixth power electronic AC switch S1 and a seventh power electronic AC switch S2, wherein an intersection point between the sixth power electronic AC switch S1 and the seventh power electronic AC switch S2 is O; a fourth bridge arm formed by an eighth power electronic AC switch S3 and a ninth power electronic AC switch S4, wherein an intersection point between the eighth power electronic AC switch S3 and the ninth power electronic AC switch S4 is P; and a second variable-topology LCL filter composed of a third inductor L21, a fourth inductor L22, and a second equivalent programmable capacitor C21; the second equivalent programmable capacitor C21 is composed of a tenth power electronic AC switch S5 and a second capacitor C2 connected in series; the switching of the second equivalent programmable capacitor C21 is controlled by controlling the on and off of the tenth power electronic AC switch S5; and the size of the second equivalent programmable capacitor C21 is adjusted by controlling the duty cycle of the tenth power electronic AC switch S5; One end of the third inductor L21 is connected to the intersection E of the sixth power electronic AC switch S5 and the eighth power electronic AC switch S3, and the other end of the third inductor L21 is connected to the second low-frequency AC Point G is connected to one end of the second equivalent programmable capacitor C21, and the other end of the second equivalent programmable capacitor C21 is connected to one end of the seventh power electronic AC switch S2 and one end of the ninth power electronic AC switch S4 respectively. Point F is connected to one end of the fourth inductor L22, and the other end of the fourth inductor L22 is connected to the second low-frequency AC The port H point.

3. The bidirectional WPT AC-AC frequency conversion system based on variable topology bidirectional AC / AC according to claim 2 is characterized in that: The first high-frequency AC on one side of the wireless power transmission unit Connected to the MN of the variable topology bidirectional AC / AC-1 unit, the second high frequency AC on the other side of the wireless power transmission unit Connected to the OP of the variable topology bidirectional AC / AC-2 unit; During forward energy transfer, that is, when energy is transferred from AB to GH, the variable-topology bidirectional AC / AC-1 unit performs power factor correction control while performing direct AC / AC conversion, and the wireless power transmission unit is used to transfer energy from MN to OP, and the variable-topology bidirectional AC / AC-2 unit performs direct AC / AC voltage and frequency conversion output on the GH side; When energy is transferred in the reverse direction, that is, when energy is transferred from GH to AB, the variable-topology bidirectional AC / AC-2 unit performs power factor correction control while performing direct AC / AC conversion, and the wireless power transmission unit is used to transfer energy from OP to MN, and the variable-topology bidirectional AC / AC-1 unit performs direct AC / AC voltage and frequency conversion on the AB side output.

4. The bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC according to claim 2 is characterized in that: When energy is transferred in the forward direction, the fifth power electronic AC switch Q5 of the variable topology bidirectional AC / AC-1 unit is always disconnected, the first capacitor C1 is not connected to the circuit, and the first variable topology structure LCL filter is changed to a dual-inductor structure. The variable topology bidirectional AC / AC-2 unit converts the first high-frequency AC Converted into a second low frequency AC Output; When energy is transferred in reverse, the tenth power electronic AC switch S5 of the variable topology bidirectional AC / AC-2 unit is always disconnected, the second capacitor C2 is not connected to the circuit, and the second variable topology structure LCL filter becomes a dual-inductor structure. When energy is transferred in reverse, the variable topology bidirectional AC / AC-1 unit converts the second high-frequency AC Convert to the first low frequency Output.

5. The bidirectional WPT AC-AC frequency conversion system based on variable topology bidirectional AC / AC according to claim 1 is characterized in that: The operating conditions of the variable topology bidirectional AC / AC-1 unit include: Working condition 1-1: is positive and The current flows from top to bottom; Working conditions 1-2: is positive and The current flows from bottom to top; Working conditions 1-3: is negative and The current flows from top to bottom; Working conditions 1-4: is negative and The current flows from bottom to top; Among them, working condition 1-1, working condition 1-2, working condition 1-3 and working condition 1-4 each have sub-working condition a: the first inductor L11 and the second inductor L12 are both charged, and sub-working condition b: the first inductor L11 and the second inductor L12 are both discharged; Working condition 1-1-a sub-working condition: is positive, Q1 and Q2 are closed, L11 and L12 are positively charged; sub-condition 1-1-b of working condition: is positive, Q1 and Q4 are closed, L11 and L12 continue to discharge, Current from top to bottom; working condition 1-2-a sub-working condition: is positive, Q3 and Q4 are closed, L11 and L12 are positively charged; sub-condition 1-2-b: is positive, Q2 and Q3 are closed, L11 and L12 are discharged in the forward direction. Current from bottom to top; working condition 1-3-a sub-condition: If the voltage is negative, Q1 and Q2 are closed, and L11 and L12 are reversely charged; sub-condition 1-3-b: is negative, Q2 and Q3 are closed, L11 and L12 are discharged in reverse direction. Current from top to bottom; working condition 1-4-a sub-working condition: If the voltage is negative, Q3 and Q4 are closed, and L11 and L12 are reversely charged; sub-condition 1-4-b: is negative, Q1 and Q4 are closed, L11 and L12 are discharged in reverse direction. The current flows from bottom to top; During forward energy transmission, the power factor correction and direct AC / AC conversion are performed by controlling the various operating conditions of the variable topology bidirectional AC / AC-1 unit, and the MN side of the wireless power transmission unit is stimulated.

6. The bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC according to claim 2, characterized in that: The operating conditions of the variable-topology bidirectional AC / AC-2 unit include: Working condition 2-1: is positive and The current flows from top to bottom; Working condition 2-2: is positive and The current flows from bottom to top; Working conditions 2-3: is negative and The current flows from top to bottom; Working conditions 2-4: is negative and The current flows from bottom to top; Among them, working condition 2-1, working condition 2-2, working condition 2-3 and working condition 2-4 each have sub-working condition a: the third inductor L21 and the fourth inductor L22 are both charged, and sub-working condition b: the third inductor L21 and the fourth inductor L22 are both discharged; Working condition 2-1-a sub-working condition: is positive, S1 and S2 are closed, L21 and L22 are positively charged; sub-condition 2-1-b: is positive, S1 and S4 are closed, L21 and L22 continue to discharge, Current from top to bottom; sub-condition 2-2-a: is positive, S3 and S4 are closed, L21 and L22 are positively charged; sub-condition 2-2-b: is positive, S2 and S3 are closed, L21 and L22 discharge in the forward direction. Current from bottom to top; sub-condition 2-3-a: When the voltage is negative, S1 and S2 are closed, and L21 and L22 are reversely charged; sub-condition 2-3-b: is negative, S2 and S3 are closed, L21 and L22 discharge in reverse direction. Current from top to bottom; working condition 2-4-a sub-condition: If the voltage is negative, S3 and S4 are closed, and L21 and L22 are charged in reverse; sub-condition 2-4-b: When the voltage is negative, S1 and S4 are closed, and L21 and L22 discharge in reverse direction; The current flows from bottom to top; During reverse energy transmission, the power factor correction and direct AC / AC conversion are performed by controlling the switching of various working conditions of the variable topology bidirectional AC / AC-2 unit, and the OP side of the wireless power transmission unit is stimulated.

7. The bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC according to claim 2, characterized in that: When energy is transferred in the forward direction, the variable topology bidirectional AC / AC-2 unit controls the duty cycle of the tenth power electronic AC switch S5 to program the size of the second programmable capacitor C21. The second variable topology LCL filter is " The LCL filter is a capacitor programmable type that is used to achieve active impedance matching under different load conditions.

8. The bidirectional WPT AC-AC frequency conversion system based on a variable topology bidirectional AC / AC according to claim 2, characterized in that: When energy is transferred in the reverse direction, the variable topology bidirectional AC / AC-1 unit controls the duty cycle of the fifth power electronic AC switch Q5 to program the size of the first programmable capacitor C21. The first variable topology LCL filter is " The LCL filter is a capacitor-programmable LCL filter that is used to achieve active impedance matching under different load conditions.

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