LLC resonant converter control system and method

Abstract

The application relates to the technical field of circuits, and particularly discloses an LLC resonant converter control system and method, wherein the control system comprises three high-frequency inverters and a three-phase high-frequency transformer; the three high-frequency inverters are connected in parallel and have a phase difference of 120 degrees; the three-phase high-frequency transformer adopts Dy connection, and the primary side is connected in a triangle mode; and the secondary side is connected in a star mode. The technical scheme can solve the problem of harmonic hazards and improve stability.

Description

Technical Field

[0001] This invention relates to the field of circuit technology, and in particular to a control system and method for an LLC resonant converter. Background Technology

[0002] The LLC resonant converter is an improvement upon the LC resonant converter by adding a parallel resonant inductor. Compared to series and parallel LC resonant converters, it offers significant improvements in gain characteristics. Due to its excellent soft-switching performance, it can substantially reduce switching losses and has been successfully applied in various power supply products, making it an important pathway to achieving high-frequency power systems. Resonant converters possess advantages such as simple structure, high efficiency, and ease of magnetic integration, and are increasingly widely used in photovoltaics, new energy vehicles, and other fields.

[0003] In certain specific environments, resonant converters are required to have a wide range of output voltage and a wide range of constant power capability. Therefore, research on topological extensions of resonant converters has always been a hot topic in the industry. Functionally, a typical resonant converter topology can be divided into several main parts: a high-frequency inverter, mainly including a chopper and resonant network; a high-frequency transformer; a rectifier module, mainly with half-wave and full-wave rectification methods; a switching network responsible for the series-parallel switching of the rectifier module; a filter and load module; and an equivalent power supply.

[0004] The main design methods for high-frequency transformers are as follows:

[0005] like Figure 1 As shown, Scheme 1 involves multiple high-frequency transformers operating in parallel. The disadvantages of this scheme are: 1. High-frequency transformers have impedance differences, and multiple circuits connected in series and parallel exhibit different parasitic parameters. Therefore, the high-frequency inverter needs to simultaneously control voltage and current sharing, which is difficult. 2. Multiple transformers connected in parallel lead to increased circulating current and reduced efficiency due to impedance inconsistencies. 3. Due to the magnetizing current in the transformers, efficiency is low under light load conditions. 4. Output rectification introduces high-order harmonics, which damage the primary-side switching transistors and cause device failure.

[0006] like Figure 2 As shown, Scheme 2 involves multi-tap switching of the transformer. The disadvantages of this scheme are: 1. When the low-voltage tap of the transformer is working, the high-voltage tap is idle, resulting in low utilization and high cost. 2. During transformer tap switching, the leakage inductance changes, the ZVS condition changes, losses increase, and efficiency decreases. 3. During transformer tap switching, the resonant point shifts, increasing control difficulty. 4. Output rectification introduces high-order harmonics, which damage the primary-side switching transistors and cause device failure.

[0007] like Figure 3As shown, Option 3 uses a three-phase transformer with a Yy connection. The disadvantages of this option are: 1. Load imbalance can easily cause neutral point shift, leading to localized overheating, reduced efficiency, and in severe cases, affecting the overall stability of the module and causing shutdown. 2. While multiple transformer windings can be connected in series for each phase, this requires high consistency in transformer coil impedance, making large-scale transformer production difficult. 3. Output rectification introduces high-order harmonics, damaging the primary-side switching transistors and causing device failure.

[0008] As can be seen from the above typical design schemes, current mainstream design methods all rely on multi-channel series-parallel designs, which inevitably involve numerous semiconductor devices. The reliability of these semiconductor devices directly affects the stability of the module; if the topology design is poor, the failure of some devices will lead to catastrophic results.

[0009] Therefore, an LLC resonant converter control system and method are needed to solve the harmonic hazards and stability problems existing in the current scheme. Summary of the Invention

[0010] One of the objectives of this invention is to provide an LLC resonant converter control system that can solve harmonic hazards and improve stability.

[0011] To solve the above-mentioned technical problems, this application provides the following technical solution:

[0012] An LLC resonant converter control system includes three high-frequency inverters and a three-phase high-frequency transformer; the three high-frequency inverters are connected in parallel with a phase difference of 120 degrees; the three-phase high-frequency transformer adopts a Dy connection, with the primary side delta-connected and the secondary side star-connected.

[0013] The basic principles and beneficial effects of the scheme are as follows:

[0014] Compared to existing schemes one through three, this scheme uses a Dy connection for the high-frequency transformer, fundamentally solving the problem of third harmonics harming the primary-side switching transistors. Compared to scheme three, this scheme has a lower zero-sequence impedance for the high-frequency transformer, allowing it to continue operating even with phase loss or imbalance at the output, thus improving the reliability of the power module. Compared to schemes two and three, this scheme uses a delta connection on one side of the high-frequency transformer. When multiple high-frequency transformers are connected in series / parallel, the requirement for coil impedance consistency is lower, effectively reducing transformer costs and facilitating mass production. Compared to schemes one and two, this scheme uses a three-phase LLC control with a 120-degree phase difference, achieving natural current sharing in the topology, requiring only voltage equalization considerations, thus simplifying the control method.

[0015] In summary, because this solution uses a delta connection on the primary side, the harmonics caused by rectification or switching networks on the secondary side will circulate within the transformer windings and will not affect the switching transistors in the high-frequency inverter. This improves the isolation effect between the primary and secondary sides of the module and solves the problem of high-order harmonic hazards on the secondary side in principle.

[0016] Furthermore, it also includes a power supply, a switching network, and three rectifier modules;

[0017] The three-phase high-frequency transformer includes a first high-frequency transformer, a second high-frequency transformer, and a third high-frequency transformer;

[0018] Of the three high-frequency inverters, the first terminals of the first, second, and third high-frequency inverters are all connected to the positive terminal of the power supply, and the second terminals of the first, second, and third high-frequency inverters are all connected to the negative terminal of the power supply.

[0019] The third terminal of the first high-frequency inverter is connected to the first terminal on the primary side of the first high-frequency transformer and to the second terminal on the primary side of the third high-frequency transformer.

[0020] The third terminal of the second high-frequency inverter is connected to the first terminal on the primary side of the second high-frequency transformer.

[0021] The third terminal of the third high-frequency inverter is connected to the first terminal on the primary side of the third high-frequency transformer.

[0022] The second end of the primary side of the first high-frequency transformer is connected to the first end of the primary side of the second high-frequency transformer;

[0023] The second end of the primary side of the second high-frequency transformer is connected to the first end of the primary side of the third high-frequency transformer;

[0024] Both ends of the secondary side of the first high-frequency transformer are connected to the first rectifier module;

[0025] Both ends of the secondary side of the second high-frequency transformer are connected to the second rectifier module;

[0026] Both ends of the secondary side of the third high-frequency transformer are connected to the third rectifier module;

[0027] The first rectifier module, the second rectifier module, and the third rectifier module are all connected to a switching network.

[0028] Furthermore, it also includes a sampling module, a control module, and a cloud platform;

[0029] The sampling module is used to collect the current values ​​of the primary and secondary sides of the first, second, and third high-frequency transformers, respectively.

[0030] The control module is used to calculate the current imbalance based on the collected current value and adjust the high-frequency inverter according to the current imbalance.

[0031] The control module is also used to send the current value to the cloud platform.

[0032] Furthermore, the sampling module is used to collect the current values ​​TA1, TA2 and TA3 on the primary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively, and is also used to collect the current values ​​TA4, TA5 and TA6 on the secondary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively;

[0033] The control module is used to calculate the three-phase current difference between TA4, TA5, and TA6;

[0034] Determine if the following conditions are met:

[0035] Condition 1: TA4>TA5>TA6, and TA4-TA6>TG1; TG1=TA4*S1;

[0036] Condition 2: TA2 > TA1 > TA3, and TA2 - TA3 > TG2; TG2 = TA2 * S1;

[0037] Condition 3: TA4-TA6>TG3; and TA4-TA6>TG3; TG3=TA4*S1;

[0038] Condition 4: TA2-TA3>TG4; and TA4-TA6>TG4; TG4=TA2*S2;

[0039] Where S1 is the first threshold and S2 is the second threshold;

[0040] If either condition one or condition two is met, it is determined that there is a current imbalance in the third high-frequency transformer; it is marked as a general fault; the control module also needs to reduce the PWM frequency of the third high-frequency inverter.

[0041] If condition three or condition four is met, it is marked as a serious fault of the third high-frequency transformer; determine whether TA2 exceeds the design rating. If it exceeds the design rating, the control module is also used to generate a shutdown command.

[0042] The control module is also used to send the current values ​​TA1, TA2, TA3, TA4, TA5 and TA6, as well as fault records, to the cloud platform.

[0043] Furthermore, the first high-frequency inverter includes MOSFET S1, MOSFET S2, and a first LLC circuit; the drain of MOSFET S1 is connected to the positive terminal of the power supply; the source of MOSFET S1 is connected to the drain of MOSFET S2, and the source of MOSFET S1 is also connected to one end of the first LLC circuit; the source of MOSFET S2 is connected to the negative terminal of the power supply; the other end of the first LLC circuit is connected to the first end of the primary side of the first high-frequency transformer and to the second end of the primary side of the third high-frequency transformer.

[0044] The second high-frequency inverter includes MOSFET S3, MOSFET S4, and a second LLC circuit; the drain of MOSFET S3 is connected to the positive terminal of the power supply; the source of MOSFET S3 is connected to the drain of MOSFET S4, and the source of MOSFET S3 is also connected to one end of the second LLC circuit; the source of MOSFET S4 is connected to the negative terminal of the power supply; the other end of the second LLC circuit is connected to the first end of the primary side of the second high-frequency transformer.

[0045] The third high-frequency inverter includes MOSFET S5, MOSFET S6, and a third LLC circuit; the drain of MOSFET S5 is connected to the positive terminal of the power supply; the source of MOSFET S5 is connected to the drain of MOSFET S6, and the source of MOSFET S5 is also connected to one end of the third LLC circuit; the source of MOSFET S6 is connected to the negative terminal of the power supply; the other end of the third LLC circuit is connected to the first end of the primary side of the third high-frequency transformer.

[0046] The second objective of this invention is to provide a control method for an LLC resonant converter, comprising the following steps:

[0047] Data acquisition steps: Collect the current values ​​of the primary and secondary sides of the first, second, and third high-frequency transformers respectively;

[0048] Analysis steps: Calculate the current imbalance based on the collected current values;

[0049] Adjustment steps: Adjust the high-frequency inverter according to the current imbalance;

[0050] Upload steps: Send the current value to the cloud platform.

[0051] Furthermore, the data collection steps specifically include:

[0052] The current values ​​TA1, TA2 and TA3 on the primary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer are collected respectively. They are also used to collect the current values ​​TA4, TA5 and TA6 on the secondary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively.

[0053] The specific analysis steps include:

[0054] Calculate the three-phase current difference between TA4, TA5, and TA6;

[0055] Determine if the following conditions are met:

[0056] Condition 1: TA4>TA5>TA6, and TA4-TA6>TG1; TG1=TA4*S1;

[0057] Condition 2: TA2 > TA1 > TA3, and TA2 - TA3 > TG2; TG2 = TA2 * S1;

[0058] Condition 3: TA4-TA6>TG3; and TA4-TA6>TG3; TG3=TA4*S1;

[0059] Condition 4: TA2-TA3>TG4; and TA4-TA6>TG4; TG4=TA2*S2;

[0060] Where S1 is the first threshold and S2 is the second threshold;

[0061] If either condition one or condition two is met, it is determined that there is a current imbalance in the third high-frequency transformer; it is marked as a general fault.

[0062] If condition three or condition four is met, mark it as a serious fault in the third high-frequency transformer; determine whether TA2 exceeds the design rating.

[0063] The adjustment steps specifically include:

[0064] In case of a general fault, reduce the PWM frequency of the third high-frequency inverter.

[0065] When TA2 exceeds the design rating, a shutdown command is generated;

[0066] The upload steps specifically include:

[0067] The current values ​​TA1, TA2, TA3, TA4, TA5, and TA6, along with the fault records, are sent to the cloud platform. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of an existing scheme for parallel operation of multiple high-frequency transformers;

[0069] Figure 2 This is a schematic diagram of multi-tap switching for an existing transformer.

[0070] Figure 3 This is a schematic diagram of the existing Yy connection method using a three-phase transformer;

[0071] Figure 4 This is a schematic diagram of an LLC resonant converter control system according to an embodiment;

[0072] Figure 5 This is a circuit diagram of an LLC resonant converter control system as an example. Detailed Implementation

[0073] The following detailed description illustrates the specific implementation method:

[0074] Example

[0075] like Figure 4As shown, an LLC resonant converter control system of this embodiment includes a power supply, a load, a switching network, three rectifier modules, three high-frequency inverters, and a three-phase high-frequency transformer.

[0076] Three high-frequency inverters are connected in parallel with a phase difference of 120 degrees. The three-phase high-frequency transformers are connected in a delta configuration on the primary side and a star configuration on the secondary side. Multiple taps can be connected in series on each phase transformer to increase the output power. The number of taps connected in series on each phase transformer can be designed according to the actual power requirement; in this embodiment, 1-6 taps are used.

[0077] The three-phase high-frequency transformer includes a first high-frequency transformer, a second high-frequency transformer, and a third high-frequency transformer;

[0078] Of the three high-frequency inverters, the first terminals of the first, second, and third high-frequency inverters are all connected to the positive terminal of the power supply, and the second terminals of the first, second, and third high-frequency inverters are all connected to the negative terminal of the power supply.

[0079] The third terminal of the first high-frequency inverter is connected to the first terminal on the primary side of the first high-frequency transformer and to the second terminal on the primary side of the third high-frequency transformer.

[0080] The third terminal of the second high-frequency inverter is connected to the first terminal on the primary side of the second high-frequency transformer.

[0081] The third terminal of the third high-frequency inverter is connected to the first terminal on the primary side of the third high-frequency transformer.

[0082] The second end of the primary side of the first high-frequency transformer is connected to the first end of the primary side of the second high-frequency transformer;

[0083] The second end of the primary side of the second high-frequency transformer is connected to the first end of the primary side of the third high-frequency transformer;

[0084] Both ends of the secondary side of the first high-frequency transformer are connected to the first rectifier module;

[0085] Both ends of the secondary side of the second high-frequency transformer are connected to the second rectifier module;

[0086] Both ends of the secondary side of the third high-frequency transformer are connected to the third rectifier module;

[0087] The first rectifier module, the second rectifier module, and the third rectifier module are all connected to a switching network, which is also connected to the load.

[0088] It also includes a sampling module, a control module, and a cloud platform.

[0089] The sampling module is used to collect the current values ​​TA1, TA2 and TA3 on the primary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively, and also to collect the current values ​​TA4, TA5 and TA6 on the secondary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively. In this embodiment, the first end of the primary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer is used as the sampling point for the current values ​​TA1, TA2 and TA3.

[0090] The control module is used to calculate the current difference between the three phases TA4, TA5, and TA6; it can also calculate the current imbalance.

[0091] Determine if the following conditions are met:

[0092] Condition 1: TA4>TA5>TA6, and TA4-TA6>TG1; TG1=TA4*S1;

[0093] Condition 2: TA2 > TA1 > TA3, and TA2 - TA3 > TG2; TG2 = TA2 * S1;

[0094] Condition 3: TA4-TA6>TG3; and TA4-TA6>TG3; TG3=TA4*S1;

[0095] Condition 4: TA2-TA3>TG4; and TA4-TA6>TG4; TG4=TA2*S2;

[0096] Wherein, S1 is the first threshold and S2 is the second threshold. The value of S1 ranges from 1% to 5%. In this embodiment, the value of S1 is 1% and the value of S2 is 20%.

[0097] If either condition one or condition two is met, it is determined that there is a current imbalance in the third high-frequency transformer; this is marked as a general fault. At this time, the neutral point of the three-phase high-frequency transformer composed of T1, T2, and T3 will deviate. The control module will also reduce the PWM frequency of the third high-frequency inverter to increase its output voltage, thus restoring the entire system to a balanced state. However, there is no need to stop the entire system; it can still operate normally. The PWM frequency adjustment range is determined based on the circuit design parameters. The frequency adjustment range of the LLC is determined by the combined values ​​of L, C, and Q within the circuit. In this embodiment, the frequency adjustment range is 50kHz-120kHz.

[0098] If condition three or condition four is met, it is marked as a serious fault of the third high-frequency transformer; at this time, it is equivalent to the system operating with a phase loss. At this time, the neutral point is seriously deviated. It is also determined whether TA2 exceeds the design rated value. If it exceeds the design rated value, the control module can also generate a shutdown command; the design rated value is determined according to the actual circuit design. In this embodiment, the design rated value is a current of 40A.

[0099] The control module is also used to send the current values ​​TA1, TA2, TA3, TA4, TA5, and TA6, as well as fault records, to the cloud platform. Fault records refer to marked general faults, severe faults in the third high-frequency transformer, etc.

[0100] Due to the symmetry of the three phases, this embodiment only describes one case; other cases can be easily deduced from this and will not be elaborated further. By modulating the output frequency difference of the PWM drive, the system continues to operate under unbalanced conditions and operates at reduced derating under phase loss conditions. Fault records are uploaded to the cloud platform, facilitating precise fault location after shutdown and enabling accurate equipment maintenance. Compared to traditional methods that only address serious faults such as machine failures after maintenance has occurred, this achieves intelligent maintenance and effectively improves the overall reliability of the system.

[0101] like Figure 5 As shown, specifically, the first high-frequency inverter includes MOSFET S1, MOSFET S2, and a first LLC circuit; the drain of MOSFET S1 is connected to the positive terminal of the power supply; the source of MOSFET S1 is connected to the drain of MOSFET S2, and the source of MOSFET S1 is also connected to one end of the first LLC circuit; the source of MOSFET S2 is connected to the negative terminal of the power supply; the other end of the first LLC circuit is connected to the first terminal of the primary side of the first high-frequency transformer and the second terminal of the primary side of the third high-frequency transformer; wherein the first LLC circuit includes an inductor L1 and a capacitor C1 connected in series;

[0102] The second high-frequency inverter includes MOSFET S3, MOSFET S4, and a second LLC circuit; the drain of MOSFET S3 is connected to the positive terminal of the power supply; the source of MOSFET S3 is connected to the drain of MOSFET S4, and the source of MOSFET S3 is also connected to one end of the second LLC circuit; the source of MOSFET S4 is connected to the negative terminal of the power supply; the other end of the second LLC circuit is connected to the first end of the primary side of the second high-frequency transformer; wherein, the second LLC circuit includes an inductor L2 and a capacitor C2 connected in series;

[0103] The third high-frequency inverter includes MOSFETs S5 and S6 and a third LLC circuit. The drain of MOSFET S5 is connected to the positive terminal of the power supply. The source of MOSFET S5 is connected to the drain of MOSFET S6, and the source of MOSFET S5 is also connected to one end of the third LLC circuit. The source of MOSFET S6 is connected to the negative terminal of the power supply. The other end of the third LLC circuit is connected to the first terminal of the primary side of the third high-frequency transformer. The third LLC circuit includes an inductor L3 and a capacitor C3 connected in series. In this embodiment, the MOSFETs are PMOS transistors.

[0104] The circuit structures of the first rectifier module D1, the second rectifier module D2, and the third rectifier module D3 are the same. Taking the first rectifier module D1 as an example, it includes four diodes, which are referred to as the first diode, the second diode, the third diode, and the fourth diode in sequence.

[0105] The positive terminal of the first diode is connected to the negative terminal of the second diode, and the connection point is marked as terminal A. The positive terminal of the third diode and the negative terminal of the fourth diode are connected, and the connection point is marked as terminal B.

[0106] The cathode of the first diode is connected to the cathode of the third diode, and the connection point is denoted as terminal C. The anode of the second diode is connected to the anode of the fourth diode, and the connection point is denoted as terminal D.

[0107] The switching network includes a capacitor C; the two ends of capacitor C are connected to the first and second ends of the load, respectively.

[0108] The first end of the secondary side of the first high-frequency transformer T1 is connected to the A end of the first rectifier module D1; the second end of the secondary side of the first high-frequency transformer T1 is connected to the B end of the first rectifier module D1.

[0109] The first end of the secondary side of the second high-frequency transformer T2 is connected to the A end of the second rectifier module D2; the second end of the secondary side of the second high-frequency transformer T2 is connected to the B end of the second rectifier module D2.

[0110] The first end of the secondary side of the third high-frequency transformer T3 is connected to the A end of the third rectifier module D3; the second end of the secondary side of the third high-frequency transformer T3 is connected to the B end of the third rectifier module D3.

[0111] The C terminal of the first rectifier module D1 is connected to the first terminal of the load, the D terminal of the first rectifier module D1, the C terminal of the second rectifier module D2, the D terminal of the second rectifier module D2, the C terminal of the third rectifier module D3, the D terminal of the third rectifier module D3, and the second terminal of the load. In this embodiment, the C terminals of the first rectifier module, the second rectifier module, and the third rectifier module are used as sampling points for current values ​​TA4, TA5, and TA6.

[0112] In this embodiment, the DC power supply provides the bus voltage, and the MOSFETs S1-S6 are switched by chopping according to specific logic to output three-phase AC voltages with a phase difference of 120°. The voltages pass through the LLC circuit, through the high-frequency transformers T1-T3, and through the full-bridge rectifier modules D1-D3 to be rectified into DC voltages, which are then filtered and output to the load.

[0113] With a 120° phase difference, the vector sum of the three-phase voltage signals within T1, T2, and T3 is zero, thus achieving a natural current sharing effect and reducing control difficulty. The harmonics generated by the secondary-side diode rectification are coupled to the primary side through the high-frequency transformer. Since the primary side is connected in a delta configuration, the harmonics will circulate within the T1-T2-T3 coils and will not harm the MOSFETs S1-S6 via the LLC circuit.

[0114] Assuming a problem occurs in the D1 rectifier module, causing an interruption in the T1 output, the Dy connection consisting of T1-T2-T3 can still work normally, with the output power reduced to 2 / 3 of full load. It will not cause a shutdown due to imbalance or phase loss in T1-T2-T3.

[0115] Even if the impedance difference between T1, T2, and T3 is large, meaning the module becomes an unbalanced three-phase load, it can still work normally.

[0116] Based on the above-described LLC resonant converter control system, this embodiment provides an LLC resonant converter control method, including the following:

[0117] Data collection steps:

[0118] The current values ​​TA1, TA2 and TA3 on the primary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer are collected respectively. They are also used to collect the current values ​​TA4, TA5 and TA6 on the secondary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively.

[0119] The specific analysis steps include:

[0120] Calculate the three-phase current difference between TA4, TA5, and TA6;

[0121] Determine if the following conditions are met:

[0122] Condition 1: TA4>TA5>TA6, and TA4-TA6>TG1; TG1=TA4*S1;

[0123] Condition 2: TA2 > TA1 > TA3, and TA2 - TA3 > TG2; TG2 = TA2 * S1;

[0124] Condition 3: TA4-TA6>TG3; and TA4-TA6>TG3; TG3=TA4*S1;

[0125] Condition 4: TA2-TA3>TG4; and TA4-TA6>TG4; TG4=TA2*S2;

[0126] Where S1 is the first threshold and S2 is the second threshold;

[0127] If either condition one or condition two is met, it is determined that there is a current imbalance in the third high-frequency transformer; it is marked as a general fault.

[0128] If condition three or condition four is met, mark it as a serious fault in the third high-frequency transformer; determine whether TA2 exceeds the design rating.

[0129] The adjustment steps specifically include:

[0130] In case of a general fault, reduce the PWM frequency of the third high-frequency inverter and increase the output voltage of the third high-frequency inverter.

[0131] When TA2 exceeds the design rating, a shutdown command is generated;

[0132] The upload steps specifically include:

[0133] The current values ​​TA1, TA2, TA3, TA4, TA5, and TA6, along with the fault records, are sent to the cloud platform.

[0134] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A control system for an LLC resonant converter, characterized in that, It includes three high-frequency inverters and a three-phase high-frequency transformer; the three high-frequency inverters are connected in parallel with a phase difference of 120 degrees; the three-phase high-frequency transformer adopts a Dy connection, with the primary side delta-connected and the secondary side star-connected; It also includes a power supply, a switching network, and three rectifier modules; The three-phase high-frequency transformer includes a first high-frequency transformer, a second high-frequency transformer, and a third high-frequency transformer; Of the three high-frequency inverters, the first terminals of the first, second, and third high-frequency inverters are all connected to the positive terminal of the power supply, and the second terminals of the first, second, and third high-frequency inverters are all connected to the negative terminal of the power supply. The third terminal of the first high-frequency inverter is connected to the first terminal on the primary side of the first high-frequency transformer and to the second terminal on the primary side of the third high-frequency transformer. The third terminal of the second high-frequency inverter is connected to the first terminal on the primary side of the second high-frequency transformer. The third terminal of the third high-frequency inverter is connected to the first terminal on the primary side of the third high-frequency transformer. The second end of the primary side of the first high-frequency transformer is connected to the first end of the primary side of the second high-frequency transformer; The second end of the primary side of the second high-frequency transformer is connected to the first end of the primary side of the third high-frequency transformer; Both ends of the secondary side of the first high-frequency transformer are connected to the first rectifier module; Both ends of the secondary side of the second high-frequency transformer are connected to the second rectifier module; Both ends of the secondary side of the third high-frequency transformer are connected to the third rectifier module; The first rectifier module, the second rectifier module, and the third rectifier module are also connected to a switching network; It also includes a sampling module, a control module, and a cloud platform; The sampling module is used to collect the current values ​​of the primary and secondary sides of the first, second, and third high-frequency transformers, respectively. The control module is used to calculate the current imbalance based on the collected current value and adjust the high-frequency inverter according to the current imbalance. The control module is also used to send the current value to the cloud platform; The sampling module is used to collect the current values ​​TA1, TA2 and TA3 on the primary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively, and is also used to collect the current values ​​TA4, TA5 and TA6 on the secondary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively. The control module is used to calculate the three-phase current difference between TA4, TA5, and TA6; Determine if the following conditions are met: Condition 1: TA4 > TA5 > TA6, and TA4 - TA6 > TG1; TG1 = TA4 * S1; Condition 2: TA2 > TA1 > TA3, and TA2 - TA3 > TG2; TG2 = TA2 * S1; Condition 3: TA4-TA6>TG3; and TA4-TA6>TG3; TG3=TA4*S1; Condition 4: TA2-TA3>TG4; and TA4-TA6>TG4; TG4=TA2*S2; Where S1 is the first threshold and S2 is the second threshold; If either condition one or condition two is met, it is determined that there is a current imbalance in the third high-frequency transformer; it is marked as a general fault; the control module also needs to reduce the PWM frequency of the third high-frequency inverter. If condition three or condition four is met, it is marked as a serious fault of the third high-frequency transformer; it is also used to determine whether TA2 exceeds the design rating. If it does, the control module is also used to generate a shutdown command. The control module is also used to send the current values ​​TA1, TA2, TA3, TA4, TA5 and TA6, as well as fault records, to the cloud platform.

2. The LLC resonant converter control system according to claim 1, characterized in that: The first high-frequency inverter includes MOSFET S1, MOSFET S2, and a first LLC circuit; the drain of MOSFET S1 is connected to the positive terminal of the power supply; the source of MOSFET S1 is connected to the drain of MOSFET S2, and the source of MOSFET S1 is also connected to one end of the first LLC circuit; the source of MOSFET S2 is connected to the negative terminal of the power supply; the other end of the first LLC circuit is connected to the first end of the primary side of the first high-frequency transformer and to the second end of the primary side of the third high-frequency transformer. The second high-frequency inverter includes MOSFET S3, MOSFET S4, and a second LLC circuit; the drain of MOSFET S3 is connected to the positive terminal of the power supply; the source of MOSFET S3 is connected to the drain of MOSFET S4, and the source of MOSFET S3 is also connected to one end of the second LLC circuit; the source of MOSFET S4 is connected to the negative terminal of the power supply; the other end of the second LLC circuit is connected to the first end of the primary side of the second high-frequency transformer. The third high-frequency inverter includes MOSFET S5, MOSFET S6, and a third LLC circuit; the drain of MOSFET S5 is connected to the positive terminal of the power supply; the source of MOSFET S5 is connected to the drain of MOSFET S6, and the source of MOSFET S5 is also connected to one end of the third LLC circuit; the source of MOSFET S6 is connected to the negative terminal of the power supply; the other end of the third LLC circuit is connected to the first end of the primary side of the third high-frequency transformer.

3. A control method for an LLC resonant converter, using the system described in claim 1, characterized in that, Includes the following steps: Data acquisition steps: Collect the current values ​​of the primary and secondary sides of the first, second, and third high-frequency transformers respectively; Analysis steps: Calculate the current imbalance based on the collected current values; Adjustment steps: Adjust the high-frequency inverter according to the current imbalance; Upload steps: Send the current value to the cloud platform.

4. The LLC resonant converter control method according to claim 3, characterized in that: The specific steps for data collection include: The current values ​​TA1, TA2 and TA3 on the primary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer are collected respectively. They are also used to collect the current values ​​TA4, TA5 and TA6 on the secondary side of the first high-frequency transformer, the second high-frequency transformer and the third high-frequency transformer respectively. The specific analysis steps include: Calculate the three-phase current difference between TA4, TA5, and TA6; Determine if the following conditions are met: Condition 1: TA4 > TA5 > TA6, and TA4 - TA6 > TG1; TG1 = TA4 * S1; Condition 2: TA2 > TA1 > TA3, and TA2 - TA3 > TG2; TG2 = TA2 * S1; Condition 3: TA4-TA6>TG3; and TA4-TA6>TG3; TG3=TA4*S1; Condition 4: TA2-TA3>TG4; and TA4-TA6>TG4; TG4=TA2*S2; Where S1 is the first threshold and S2 is the second threshold; If either condition one or condition two is met, it is determined that there is a current imbalance in the third high-frequency transformer; it is marked as a general fault. If condition three or condition four is met, mark it as a serious fault in the third high-frequency transformer; determine whether TA2 exceeds the design rating. The adjustment steps specifically include: In case of a general fault, reduce the PWM frequency of the third high-frequency inverter. When TA2 exceeds the design rating, a shutdown command is generated; The upload steps specifically include: The current values ​​TA1, TA2, TA3, TA4, TA5, and TA6, along with the fault records, are sent to the cloud platform.

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