Control method and system of V2G charging pile resonant converter

Abstract

The invention discloses a control method and system for a V2G charging pile resonant converter, and relates to the technical field of charging pile converters, and the method comprises the steps: constructing the structure of a resonant converter, and obtaining a working mode of the converter; in the control strategy, a power transmission model of the converter is constructed to obtain a relation between phase shift in the ports, phase shift between the ports and output power; and calculating a phase-shifting angle track under power factor optimization, and enabling the converter to output specified power through a phase-shifting controller. The converter is of a single-stage three-port structure, and power transmission of three working modes of V2G, G2V and H2L can be flexibly achieved. On the basis, due to the fact that the optimized modulation method considering the characteristics of the low current stress and the grid-side high power factor is used, the converter has the low current stress and the grid-side high power factor, the integration level and efficiency of the automobile charging pile are improved, and meanwhile flexible and efficient charging and discharging management of an electric vehicle battery is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of charging pile converters, and in particular to a control method and system for a V2G charging pile resonant converter. Background Art

[0002] In recent years, the electric vehicle industry has developed rapidly. New energy vehicles are connected to the power supply network through charging and battery replacement facilities, and a two-way interactive system of information flow and energy flow between new energy vehicles and the power supply network is constructed. The flexible adjustment ability of power batteries as controllable loads or mobile energy storage can be effectively exerted, providing important support for the efficient and economic operation of new power systems. The car charging device with V2G (Vehicle-to-Grid) function has received widespread attention. Traditional car charging piles usually consist of a two-stage structure, including an AC / DC front-stage structure with PFC (Power-Factor-Correction) function and a rear-stage DC / DC power conversion circuit. Due to the easy control of full-bridge PFC, full-bridge-based bidirectional PFC and its derivative topological structures are widely used in the front-stage circuit. In order to further reduce device stress and improve system power level, structures such as bridgeless PFC have been proposed and applied to the front-stage structure of the three-port converter, which improves the flexibility of power transmission, reduces the conduction loss of the converter, and can realize power transmission in multiple working modes of the charging pile power supply system. However, this PFC+DC / DC two-stage structure increases the complexity of the topological structure and limits the further improvement of power density.

[0003] Therefore, in order to realize a charging system with high power density and high grid-side power factor characteristics, the present invention designs a novel single-stage three-port converter, aiming to improve the integration of the automobile charging system and realize flexible and efficient charging and discharging management. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is: how to solve the problem that the existing PFC+DC / DC two-stage structure increases the complexity of the topological structure and limits the further improvement of the power density.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a control method for a V2G charging pile resonant converter, comprising: constructing a structure of a resonant converter to obtain a working mode of the converter; in a control strategy, by constructing a power transmission model of the converter, the relationship between the phase shift within a port, the phase shift between ports and the output power is obtained; the phase shift angle trajectory under power factor optimization is calculated, and the converter outputs a specified power through a phase shift controller.

[0007] As a preferred solution of the control method of a V2G charging pile resonant converter described in the present invention, wherein: the working modes of the converter include G2V mode, V2G mode and H2L mode; the G2V mode includes power flowing from the grid side to the power battery and the low-voltage side to charge the two batteries; the V2G mode includes power flowing from the power battery side to the grid side to inject the power battery energy back to the grid; the H2L mode includes power flowing from the power battery side to the low-voltage side, and the power battery supplies power to the low-voltage device or battery.

[0008] As a preferred solution of the control method of a V2G charging pile resonant converter described in the present invention, the power transmission model of the converter includes converting all the power transmission inductance and port parameters to the port 3 side winding to obtain a Y-shaped equivalent model with three ports in parallel, and the equivalent power transmission inductance L1', L2', L3 of port 1, port 2, and port 3 3eq It is expressed as:

[0009]

[0010] Among them, L1, L2, L3 are the power transmission inductors of port 1, port 2, and port 3 respectively, N1, N2, N3 are the turns of winding 1, 2, and 3 respectively, L k3 is the leakage inductance of the transformer converted to port 3, ω r is the converter resonant frequency, C r is the resonant capacitor; the Δ-shaped equivalent model is obtained through Y / Δ equivalent transformation, and the impedance in the Δ-shaped equivalent model of the converter is expressed as:

[0011]

[0012] Among them, L 13 * , L 23 * , L 12 * are the equivalent inductances between port 1 and port 3, port 2 and port 3, and port 1 and port 2 in the Δ-shaped equivalent model; when port 3 does not participate in the circuit operation, port 1 is converted to the port 2 side, and L1″ is the equivalent inductance converted to port 2, expressed as:

[0013]

[0014] Wherein, L1″ is the equivalent inductance converted to port 2.

[0015] As a preferred solution of the control method of a V2G charging pile resonant converter described in the present invention, the relationship between the intra-port phase shift, the inter-port phase shift and the output power includes calculating the power transmission between different ports of the converter according to the equivalent port circuit and expressing it as follows:

[0016]

[0017] Among them, P xy is the power transmitted from port x to port y, f s is the switching frequency, V dc1 、V dc2 、v ac3 is the voltage of port 1, port 2, and port 3, n 21 is the turns ratio of port 2 to port 1, n 31 is the turns ratio of port 3 to port 1, n 32 is the turns ratio of port 3 to port 2, D 11 , D 22 is the phase shift angle between the bridge arms of port 1 and port 2 of the converter, D 13 , D 23 is the phase shift angle between ports 1, 2 and 3; the transmission power of each port is defined as:

[0018]

[0019]

[0020] Among them, P1, P2, and P3 are the transmission powers of port 1, port 2, and port 3 respectively.

[0021] As a preferred solution of the control method of a V2G charging pile resonant converter described in the present invention, wherein: the calculation of the phase shift angle trajectory under power factor optimization includes combining the transmission power to make the inductor current and the AC side voltage in phase during the switching cycle to achieve a high power factor, and the inductor current phase is affected by the bridge voltage ratio M between port 1 and port 3 13 、Port 1 bridge arm phase shift angle D 11 And the phase shift angle D between ports 1 and 3 13 Impact, M 13 It is expressed as:

[0022]

[0023] Among them, M 13 is the voltage ratio between the bridges at port 1 and port 3; we get M 23 、M 12 It is expressed as:

[0024]

[0025] Among them, M 23 is the bridge voltage ratio between port 2 and port 3, M 12 is the bridge voltage ratio between port 1 and port 3; if the inductor current is to be in phase with the AC side voltage, the following conditions must be met:

[0026]

[0027] The voltage and current on the AC side are in phase, and the variable values ​​are expressed as:

[0028]

[0029]

[0030] Among them, P N,13 The reference power for transmitting power from port 1 to port 3.

[0031] As a preferred solution of the control method of a V2G charging pile resonant converter described in the present invention, wherein: the G2V mode includes when the grid side supplies power to the power battery and the low-voltage equipment, the power of the V2G is reversely transmitted. For the power battery, at this time D 11 , D 12 Both are negative, and the absolute value is the same as in V2G mode. For low-voltage equipment, it is expressed as:

[0032]

[0033] P N,23 It is expressed as:

[0034]

[0035] Among them, P N,23 The reference power for transmitting power from port 2 to port 3.

[0036] As a preferred solution of the control method of a V2G charging pile resonant converter described in the present invention, wherein: the H2L mode includes charging the low-voltage device from the high-voltage power battery. In the H2L mode, there are three control variables, the phase shift angle D between the two DC bridge arms 11 , D 22 The phase shift angle D between the DC and AC ports 12 , D 23 Fixed to 0, by controlling D 13 That is to achieve the phase shift angle D 12 The indirect control is based on minimizing the peak value of the inductor current and satisfying the power demand as the constraint. The Lagrange multiplier method is used to find the extreme value. The objective function model is expressed as:

[0037] z=I Lmax (D11 ,D 22 ,D 13 ,D 23 )

[0038] condition:P 12 (D 11 ,D 22 ,D 13 ,D 23 )=P ref,12

[0039] Among them, z is the objective function, I Lmax is the peak current on inductor L2, P 12 is the power value flowing from port 1 to port 2 calculated by the power expression, P ref,12 is the power reference value, and the optimal solution of each control variable obtained by solving the model is expressed as:

[0040]

[0041] P N,12 It is expressed as:

[0042]

[0043] Among them, P N,12 The reference power for transmitting power from port 1 to port 2.

[0044] Another object of the present invention is to provide a system of a control method for a V2G charging pile resonant converter, which can solve a control problem of a V2G charging pile resonant converter by constructing a control system for the V2G charging pile resonant converter.

[0045] To solve the above technical problems, the present invention provides the following technical solutions: a control system for a V2G charging pile resonant converter, comprising a construction module, a power relationship module and an output power module; the construction module is used to construct the structure of the resonant converter to obtain the working mode of the converter; the power relationship module is used to obtain the relationship between the phase shift within the port, the phase shift between the ports and the output power by constructing a power transmission model of the converter in the control strategy; the output power module is used to calculate the phase shift angle trajectory under power factor optimization, and the converter outputs a specified power through a phase shift controller.

[0046] A computer device includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the control method of a V2G charging pile resonant converter as described above are implemented.

[0047] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a control method for a V2G charging pile resonant converter as described above.

[0048] The beneficial effects of the present invention are as follows: Compared with the traditional two-stage two-port converter structure, the control method of the V2G charging pile resonant converter provided by the present invention is a single-stage three-port structure, which can flexibly realize the power transmission of the three working modes of V2G, G2V, and H2L. On this basis, due to the use of the invented optimized modulation method that takes into account the characteristics of low current stress and high power factor on the grid side, the converter has low current stress and high power factor on the grid side, while improving the integration and efficiency of the automobile charging pile, it realizes flexible and efficient charging and discharging management of the electric vehicle battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0050] Figure 1 A flow chart of a control method for a V2G charging pile resonant converter provided in the first embodiment of the present invention.

[0051] Figure 2 An isolated three-port bidirectional AC / DC converter topology diagram of a control method for a V2G charging pile resonant converter provided in the first embodiment of the present invention.

[0052] Figure 3 A schematic diagram of power transmission directions in various modes of a three-port converter of a control method for a V2G charging pile resonant converter provided in the first embodiment of the present invention.

[0053] Figure 4 A structural diagram of a control system of a V2G charging pile resonant converter provided in accordance with the second embodiment of the present invention.

[0054] Figure 5 A V2G mode key waveform diagram of a control method for a V2G charging pile resonant converter provided in the third embodiment of the present invention.

[0055] Figure 6 This is a key waveform diagram of the G2V mode of a control method for a V2G charging pile resonant converter provided in the third embodiment of the present invention.

[0056] Figure 7This is a key waveform diagram of the H2L mode of a control method for a V2G charging pile resonant converter provided in the third embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0058] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0059] Example 1, reference Figure 1 to Figure 3 , which is the first embodiment of the present invention, and this embodiment provides a control method for a V2G charging pile resonant converter, including: constructing a structure of a resonant converter to obtain a working mode of the converter; in a control strategy, by constructing a power transmission model of the converter, obtaining the relationship between the phase shift within a port, the phase shift between ports and the output power; calculating the phase shift angle trajectory under power factor optimization, and making the converter output a specified power through a phase shift controller.

[0060] S1. Construct the structure of the resonant converter and obtain the working mode of the converter.

[0061] The structure of the resonant converter: MOSFET switches S1-S4 and switches S5-S8 form two full-bridge circuits, switches S9-S 12 and half-bridge capacitor C f1 , C f2 The bidirectional half-bridge circuit consists of a three-winding transformer, inductors L1, L2, L3 between ports, and a resonant capacitor C r , leakage inductance L k .

[0062] like Figure 2 The three-port isolated bidirectional AC / DC converter topology is shown in FIG. 2. The two full-bridge circuits composed of switches S1-S4 and switches S5-S8, and the two full-bridge circuits composed of switches S9-S 12 and half-bridge capacitor C f1 , C f2 The bidirectional half-bridge circuit consists of a three-winding transformer (the three-winding turns ratio is N1:N2:N3), inter-port inductors L1, L2, L3, and a resonant capacitor C r , leakage inductance L k3 And the grid-side inductance L g .v T1 、v T2 、v T3Indicates the bridge arm voltage, ports 1-3 are connected to the power battery (voltage is expressed as V dc1 ), low voltage electrical devices (voltage is expressed as V dc2 ) and the power grid (voltage is represented by v ac3 ).

[0063] The converter has three working modes: 1) G2V (Grid-to-Vehicle) mode: power flows from the grid side to the power battery and the low-voltage side to charge both batteries; 2) V2G (Vehicle-to-Grid) mode: power flows from the power battery side to the grid side, injecting power battery energy back into the grid; 3) H2L (High voltage-to-Lowvoltage) mode: power flows from the power battery side to the low-voltage side, and the power battery supplies power to the low-voltage device or battery.

[0064] like Figure 3 As shown in the figure, the transmission directions of the three power transmission modes of V2G, G2V, and H2L, where n 31 v T1 、n 32 v T2 、v T3 n 31 times the port 1 voltage, n32 times the port 2 voltage, and n32 times the port 3 voltage. 31 is the transformer turns ratio between port 3 and port 1, n 32 is the transformer turns ratio of port 3 to port 2.

[0065] S2. In the control strategy, by constructing a power transfer model of the converter, the relationship between the intra-port phase shift, the inter-port phase shift and the output power is obtained.

[0066] The power transmission inductance and port parameters are all converted to the winding on the port 3 side, and a Y-shaped equivalent model with three ports in parallel is obtained. The equivalent power transmission inductances L1′, L2′, L 3eq It can be expressed as:

[0067]

[0068] Among them, L1, L2, L3 are the power transmission inductors of port 1, port 2, and port 3 respectively, N1, N2, N3 are the turns of winding 1, 2, and 3 respectively, L k3 is the leakage inductance of the transformer converted to port 3, ω r is the converter resonant frequency, C r is the resonant capacitor.

[0069] Further through the Y / Δ equivalent transformation, the Δ-shaped equivalent model can be obtained. The impedance expression in the Δ-shaped equivalent model of the converter is as follows:

[0070]

[0071] Among them, L 13 * , L 23 * , L 12 * They are the equivalent inductances between port 1 and port 3, between port 2 and port 3, and between port 1 and port 2 in the Δ-shaped equivalent model.

[0072] In particular, when port 3 does not participate in the circuit operation, port 1 is converted to port 2, and L1″ is the equivalent inductance converted to port 2. The expression is as follows:

[0073]

[0074] Wherein, L1″ is the equivalent inductance converted to port 2.

[0075] In this converter, phase shift modulation is adopted. The circuits on ports 1 and 2 adopt a full-bridge structure, and the phase shift angle between the bridge arms is defined as D 11 (Phase shift angle of switch S4 relative to S1), D 22 (The phase shift angle of switch S8 relative to S5), while the circuit on the port 3 side adopts a bidirectional half-bridge structure, and there is a phase shift angle D between ports 1 and 2 13 (Phase shift angle of switch S9 relative to S1), D 23 (The phase shift angle of switch S9 relative to S5). Therefore, when power is transmitted between port 1 and port 3, and between port 2 and port 3, the adjustable variable is a phase shift angle between bridge arms (D 11 or D 22 ) and a port-to-port phase shift angle (D 13 or D 23 ), and when power is transmitted between port 1 and port 2, the adjustable variables include the phase shift angle between the two bridge arms (D 11 and D 22 ) and the phase shift angle between the two ports (D 13 and D 23 ), for which the variables are adjusted according to different modes.

[0076] The power transmitted between the converter ports is the integral of the product of the corresponding equivalent inductor current and voltage, which is a unified variable. The phase shift angle D between port 1 and port 2 is 12 (The phase shift angle of switch S5 relative to S1) is given by D 13 -D 23 Indicates that D 23 Set to zero, then control D 13 Realize phase shift between port 1 and port 2.

[0077] According to the equivalent port circuit, the power transfer expression between different ports of the converter can be calculated as follows:

[0078]

[0079] Among them, P xy is the power transmitted from port x to port y, f s is the switching frequency, V dc1 、V dc2 、v ac3 is the voltage of port 1, port 2, and port 3, n 21 is the turns ratio of port 2 to port 1, n 31 is the turns ratio of port 3 to port 1, n 32 is the turns ratio of port 3 to port 2, and the phase shift angle between the converter bridge arms is D 11 (Phase shift angle of switch S4 relative to S1), D 22 (The phase shift angle of switch S8 relative to S5). Ports 1 and 2 have a phase shift angle D between them. 13 (Phase shift angle of switch S9 relative to S1), D 23 (Phase shift angle of switch S9 relative to S5).

[0080] The expression that defines the transmission power of each port is:

[0081]

[0082] Among them, P1, P2, and P3 are the powers of port 1, port 2, and port 3 respectively. The expression is:

[0083]

[0084] S3. Calculate the phase shift angle trajectory under power factor optimization, and make the converter output a specified power through a phase shift controller.

[0085] In the application scenario of electric vehicle charging and discharging system, the key is to meet the three power transmission modes of V2G, G2V and H2L. In the V2G mode, power only flows from the power battery side to the grid side.

[0086] Combined with the power expression, the inductor current and the AC side voltage are kept in phase during the switching cycle to achieve a high power factor. The inductor current phase is affected by the bridge voltage ratio M between port 1 and port 3. 13 、Port 1 bridge arm phase shift angle D 11 And the phase shift angle D between ports 1 and 3 13 Impact, M 13 The expression is as follows:

[0087]

[0088] Among them, M 13 is the voltage ratio between the bridges at port 1 and port 3.

[0089] Similarly, we can get M 23 、M 12 expression:

[0090]

[0091] Among them, M 23 is the bridge voltage ratio between port 2 and port 3, M 12 is the bridge voltage ratio between port 1 and port 3. If the inductor current is to be in phase with the AC side voltage, the following relationship must be satisfied:

[0092]

[0093] The voltage and current on the AC side are in phase, and the variable values ​​under this condition can be obtained:

[0094]

[0095] Among them, P N,13 is the reference power for transmitting power from port 1 to port 3. The expression is as follows:

[0096]

[0097] In G2V mode, when the grid side supplies power to the power battery and low-voltage equipment, the power of V2G is transmitted in the reverse direction. For the power battery, D 11 , D 12 Both are negative, and the absolute value is the same as in V2G mode. For low-voltage equipment, the expression is as follows:

[0098]

[0099] P N,23 It is expressed as:

[0100]

[0101] Among them, P N,23 The reference power for transmitting power from port 2 to port 3.

[0102] In H2L mode, the high-voltage power battery charges the low-voltage equipment. In this mode, there are three control variables: the phase shift angle D between the two DC bridge arms 11 , D 22 The phase shift angle D between the DC and AC ports 12 To unify with the above control strategy, D 23 Fixed to 0, by controlling D 13That is to achieve the phase shift angle D 12 Indirect control. With the goal of minimizing the inductor current peak and the constraint of meeting the power demand, the Lagrange multiplier method is used to find the extreme value, and the model is as follows:

[0103] z=I Lmax (D 11 ,D 22 ,D 13 ,D 23 )

[0104] condition:P 12 (D 11 ,D 22 ,D 13 ,D 23 )=P ref,12

[0105] Among them, z is the objective function, I Lmax is the peak current on inductor L2, P 12 is the power value flowing from port 1 to port 2 calculated by the power expression, P ref,12 is the power reference value. Solving the model to obtain the optimal solution of each control variable is as follows:

[0106]

[0107] P N,12 It is expressed as:

[0108]

[0109] Among them, P N,12 The reference power for transmitting power from port 1 to port 2.

[0110] Example 2, reference Figure 4 , which is the second embodiment of the present invention, is different from the previous embodiment in that it provides a control system for a V2G charging pile resonant converter, including: a building module 100, a power relationship module 200 and an output power module 300.

[0111] The construction module 100 is used to construct the structure of the resonant converter and obtain the working mode of the converter.

[0112] The power relationship module 200 is used to obtain the relationship between the intra-port phase shift, the inter-port phase shift and the output power by constructing a power transmission model of the converter in the control strategy.

[0113] The output power module 300 is used to calculate the phase shift angle trajectory under power factor optimization, and enables the converter to output a specified power through a phase shift controller.

[0114] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0115] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0116] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0117] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0118] Example 3, reference Figure 5 to Figure 7 , which is the third embodiment of the invention, and which is different from the first two embodiments in that: it is used to verify and illustrate the technical effects adopted in the present invention in order to verify the real effects of this method.

[0119] like Figure 5 As shown in the figure, it is the key waveform of V2G mode. In V2G mode, the power battery discharges to the grid side to obtain the grid side current and voltage waveform. The grid side current and voltage are basically in phase. The square wave voltage on both sides of the converter resonant cavity and the waveform of the inductor current in the switching cycle are partially amplified. As shown in the figure, the inductor current and the grid side square wave voltage are in the same frequency and phase during the switching cycle, which verifies the high power factor control algorithm proposed in the invention.

[0120] like Figure 6 As shown, it is the key waveform of the G2V mode. The power grid supplies power to the high-voltage power battery and the low-voltage power device at the same time. The charging current ripples of port 1 and port 2 are 0.3A and 3.5A respectively. At the same time, the voltage and current on the grid side maintain the same frequency and phase, and it can still maintain a high power factor in the G2V working mode.

[0121] like Figure 7 As shown, it is the key waveform of H2L mode. In H2L mode, a low current stress wide soft switching range modulation strategy is adopted. It can be seen that port 1 is in a discharging state with a discharge ripple of 0.2A, and port 2 is in a charging state with a charging ripple of 0.8A. In addition, the key waveform is amplified during the switching cycle. It can be seen that through this control strategy, the inductor current can form a platform at zero current, which greatly reduces the current stress. At the same time, all switch tubes S1-S4 on the port 1 side realize ZVS, and all switch tubes S5-S8 on the port 2 side realize ZCS, which verifies the effectiveness of the optimization algorithm under H2L mode.

[0122] 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 preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A control method for a V2G charging pile resonant converter, characterized in that: include, Construct the structure of the resonant converter and obtain the working mode of the converter; In the control strategy, the power transmission model of the converter is constructed to obtain the relationship between the intra-port phase shift, the inter-port phase shift and the output power; The phase shift angle trajectory under power factor optimization is calculated, and the converter outputs the specified power through the phase shift controller.

2. A control method for a V2G charging pile resonant converter according to claim 1, characterized in that: The working modes of the converter include G2V mode, V2G mode and H2L mode; The G2V mode includes power flowing from the grid side to the power battery and the low voltage side, charging both batteries; The V2G mode includes power flowing from the power battery side to the grid side, injecting power battery energy back into the grid; The H2L mode includes power flowing from the power battery side to the low voltage side, and the power battery supplies power to the low voltage device or battery.

3. A control method for a V2G charging pile resonant converter as claimed in claim 2, characterized in that: The power transmission model of the converter includes converting all the power transmission inductance and port parameters to the port 3 side winding to obtain a Y-shaped equivalent model of three ports in parallel, and the equivalent power transmission inductances L1', L2', L3 of port 1, port 2 and port 3 are L1', L2', L 3eq It is expressed as, Among them, L1, L2, L3 are the power transmission inductors of port 1, port 2, and port 3 respectively, N1, N2, N3 are the turns of winding 1, 2, and 3 respectively, L k3 is the leakage inductance of the transformer converted to port 3, ω r is the converter resonant frequency, C r is the resonant capacitor; The Δ-shaped equivalent model is obtained through Y / Δ equivalent transformation. The impedance in the Δ-shaped equivalent model of the converter is expressed as: Among them, L 13 * , L 23 * , L 12 * are the equivalent inductances between port 1 and port 3, between port 2 and port 3, and between port 1 and port 2 in the Δ-shaped equivalent model; When port 3 does not participate in the circuit operation, port 1 is converted to port 2, and L1″ is the equivalent inductance converted to port 2, expressed as, Wherein, L1″ is the equivalent inductance converted to port 2.

4. A control method for a V2G charging pile resonant converter as claimed in claim 3, characterized in that: The relationship between the intra-port phase shift, the inter-port phase shift and the output power includes calculating the power transfer between different ports of the converter based on the equivalent port circuit and expressing it as: Among them, P xy is the power transmitted from port x to port y, f s is the switching frequency, V dc1 、V dc2 、v ac3 is the voltage of port 1, port 2, and port 3, n 21 is the turns ratio of port 2 to port 1, n 31 is the turns ratio of port 3 to port 1, n 32 is the turns ratio of port 3 to port 2, D 11 , D 22 is the phase shift angle between the bridge arms of port 1 and port 2 of the converter, D 13 , D 23 is the phase shift angle between ports 1, 2 and 3; The transmission power of each port is defined as: Among them, P1, P2, and P3 are the transmission powers of port 1, port 2, and port 3 respectively.

5. A control method for a V2G charging pile resonant converter as claimed in claim 4, characterized in that: The calculation of the phase shift angle trajectory under power factor optimization includes combining the transmission power to make the inductor current and the AC side voltage in phase during the switching cycle to achieve a high power factor, and the inductor current phase is affected by the bridge voltage ratio M between port 1 and port 3. 13 、Port 1 bridge arm phase shift angle D 11 And the phase shift angle D between ports 1 and 3 13 Impact, M 13 It is expressed as, Among them, M 13 is the voltage ratio between the bridges at port 1 and port 3; Get M 23 、M 12 It is expressed as, Among them, M 23 is the bridge voltage ratio between port 2 and port 3, M 12 is the bridge voltage ratio between port 1 and port 3; If the inductor current is to be in phase with the AC side voltage, then the following conditions must be met: The voltage and current on the AC side are in phase, and the variable values ​​are expressed as: Among them, P N,13 The reference power for transmitting power from port 1 to port 3.

6. A control method for a V2G charging pile resonant converter as claimed in claim 5, characterized in that: The G2V mode includes the reverse transmission of V2G power when the grid side supplies power to the power battery and low-voltage equipment. For the power battery, D 11 , D 12 All are negative, and the absolute value is the same as that in V2G mode. For low-voltage equipment, it is expressed as, P N,23 It is expressed as, Among them, P N,23 The reference power for transmitting power from port 2 to port 3.

7. A control method for a V2G charging pile resonant converter as claimed in claim 6, characterized in that: The H2L mode includes charging the low-voltage device from the high-voltage power battery. In the H2L mode, there are three control variables: the phase shift angle D between the two DC bridge arms. 11 , D 22 The phase shift angle D between the DC and AC ports 12 , D 23 Fixed to 0, by controlling D 13 That is to achieve the phase shift angle D 12 The indirect control is based on minimizing the peak value of the inductor current and satisfying the power demand as the constraint. The Lagrange multiplier method is used to find the extreme value. The objective function model is expressed as: z=I Lmax (D 11 ,D 22 ,D 13 ,D 23 ) condition:P 12 (D 11 ,D 22 ,D 13 ,D 23 )=P ref,12 Among them, z is the objective function, I Lmax is the peak current on inductor L2, P 12 is the power value flowing from port 1 to port 2 calculated by the power expression, P ref,12 is the power reference value, and the optimal solution of each control variable obtained by solving the model is expressed as: P N,12 It is expressed as, Among them, P N,12 The reference power for transmitting power from port 1 to port 2.

8. A system using a control method of a V2G charging pile resonant converter as claimed in any one of claims 1 to 7, characterized in that: It comprises a construction module (100), a power relationship module (200) and an output power module (300); The construction module (100) is used to construct the structure of a resonant converter and obtain the working mode of the converter; The power relationship module (200) is used to obtain the relationship between the intra-port phase shift, the inter-port phase shift and the output power by constructing a power transmission model of the converter in the control strategy; The output power module (300) is used to calculate the phase shift angle trajectory under power factor optimization, and enables the converter to output designated power through a phase shift controller.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a method for controlling a V2G charging pile resonant converter according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a control method for a V2G charging pile resonant converter according to any one of claims 1 to 7 are implemented.

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