Totally immersed power module and charging system

Abstract

The application discloses a full-immersion power module and a charging system, and relates to the technical field of charging. The power module comprises a PCBA assembly, the PCBA assembly is fully immersed in insulating cooling liquid, the PCBA assembly comprises a heating circuit, a temperature detection device and an AC / DC conversion circuit, the heating circuit comprises a heating unit and a switching unit; the heating unit is arranged between an alternating-current power supply and the AC / DC conversion circuit, the switching unit is connected with a controller of the charging system; the temperature detection device is used for detecting the temperature of the insulating cooling liquid; the controller is used for outputting a first control signal to the switching unit according to a preset strategy when the temperature of the insulating cooling liquid is less than a first temperature value; the switching unit is used for conducting the heating unit in response to the first control signal output by the controller; and the heating unit is used for heating the insulating cooling liquid in the case that the heating circuit works. Thus, the insulating cooling liquid is heated by the power module itself, and the problem of reduced reliability of the charging system caused by low temperature of the insulating cooling liquid is solved.

Description

Technical Field

[0001] This application relates to the field of charging technology, and in particular to a fully immersion power module and charging system. Background Technology

[0002] With the increasing popularity of electric vehicles, the performance and reliability requirements of high-power modules are becoming increasingly stringent. In the design of oil-based immersion liquid-cooled power modules, mineral oil and other highly insulating coolants are typically used. Their specific heat capacity is much higher than that of air, which can effectively dissipate heat. However, in low-temperature or ultra-low-temperature environments, the insulating coolant may cause new problems.

[0003] First, low temperatures increase the viscosity of the insulating coolant, increasing system circulation resistance and potentially causing excessively high local pressure, thus affecting the normal operation of the liquid cooling system. Second, when electronic components (such as electrolytic capacitors) operate for extended periods in low-temperature insulating coolant, their performance indicators (such as equivalent series resistance and capacitance) will significantly degrade. Directly initiating charging in such conditions may lead to a deterioration in output characteristics, affecting charging efficiency and even damaging the equipment. Furthermore, uneven heat dissipation within the module may cause localized overheating in low-temperature environments, further threatening system reliability. Summary of the Invention

[0004] The main objective of this application is to provide a fully submersible power module and charging system that solves the problem of reduced charging system reliability caused by low temperature of the insulating coolant by heating the insulating coolant within the power module itself.

[0005] To achieve the above objectives, this application provides a fully immersed power module, the power module including a PCBA assembly, the PCBA assembly being fully immersed in an insulating coolant, the PCBA assembly including a heating circuit, a temperature detection device, and an AC / DC conversion circuit, the heating circuit including a heating unit and a switching unit; The heating unit is disposed between the AC power supply and the AC / DC conversion circuit, and the switching unit is connected to the controller of the charging system. The temperature detection device is used to detect the temperature of the insulating coolant. The controller is used to output a first control signal to the switching unit according to a preset strategy when the temperature of the insulating coolant is less than a first temperature value. The switching unit is used to respond to the first control signal output by the controller and turn on the heating unit. The heating unit is used to heat the insulating coolant when the heating circuit is working.

[0006] Optionally, the PCBA assembly further includes an AC / DC conversion circuit connected to the heating unit. The switching unit is disposed in the AC / DC conversion circuit and is used to control the DC bus voltage of the AC / DC conversion circuit. The preset strategy includes: outputting a second control signal to the switching unit, and outputting the first control signal to the switching unit when the DC bus voltage reaches a first threshold; repeating the above steps when the DC bus voltage reaches a second threshold until the temperature of the insulating coolant reaches a second temperature value. The second control signal is used to control the switching unit to turn off, the first control signal is used to control the switching unit to close, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

[0007] Optionally, the PCBA assembly further includes an AC / DC conversion circuit connected to the heating unit. The switching unit is disposed in the AC / DC conversion circuit and is used to control the DC bus voltage of the AC / DC conversion circuit. The preset strategy includes: outputting a second control signal to the switching unit, and when it is determined that the DC bus voltage reaches a first threshold, outputting a pulse-type first control signal to the switching unit according to a preset duty cycle; when it is determined that the DC bus voltage reaches a second threshold, repeating the above steps until the temperature of the insulating coolant reaches a second temperature value; wherein the second control signal is used to control the switching unit to turn off, the first control signal is used to control the switching unit to close, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

[0008] Optionally, the PCBA assembly further includes an AC / DC conversion circuit connected to the heating unit. The switching unit is disposed in the AC / DC conversion circuit and is used to control the DC bus voltage of the AC / DC conversion circuit. The preset strategy includes: outputting a second control signal to the switching unit; and, when the DC bus voltage reaches a first threshold, outputting a pulsed first control signal to the switching unit according to a target duty cycle; and, when the DC bus voltage reaches a second threshold, repeating the above steps until the temperature of the insulating coolant reaches a second temperature value. The target duty cycle is dynamically adjusted based on a set voltage and the DC bus voltage. The second control signal is used to control the switching unit to turn off, the first control signal is used to control the switching unit to close, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

[0009] Optionally, the AC power supply includes three output terminals, and the heating unit includes three heating sub-units; one end of each heating sub-unit is connected to each of the output terminals respectively, and the other end of each heating sub-unit is connected to the AC / DC conversion circuit; each heating sub-unit includes a heating device and a controllable switch, the heating device and the controllable switch are connected in parallel, and the controllable switch is used to disconnect when the temperature of the insulating coolant is lower than a first temperature value, so as to conduct the branch where the heating device is located.

[0010] Optionally, the AC / DC conversion circuit is a Vienna circuit; the switching unit includes a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, and a ninth switch; the fourth switch and the fifth switch are connected in reverse series and then connected between the first switch and the midpoint of the DC bus; the sixth switch and the seventh switch are connected in reverse series and then connected between the second switch and the midpoint of the DC bus; the eighth switch and the ninth switch are connected in reverse series and then connected between the third switch and the midpoint of the DC bus.

[0011] Optionally, the switching unit includes a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, and a ninth switch; the fourth switch and the fifth switch are connected in series to both ends of the DC bus, the sixth switch and the seventh switch are connected in series to both ends of the DC bus, and the eighth switch and the ninth switch are connected in series to both ends of the DC bus; the other end of the first switch is connected between the fourth switch and the fifth switch, the other end of the second switch is connected between the sixth switch and the seventh switch, and the other end of the third switch is connected between the eighth switch and the ninth switch.

[0012] Optionally, the heating unit includes multiple heating sub-units, the switching unit includes at least one switching sub-unit, the heating sub-unit includes at least one heating device, and the switching sub-unit includes a switching tube; the heating devices are connected in series and / or in parallel, the first end of the switching tube is connected to the corresponding heating sub-unit, the second end of the switching tube is grounded, and the third end of the switching tube is connected to the controller.

[0013] Optionally, the preset strategy includes: continuously outputting the first control signal to the switching unit when the temperature of the insulating coolant is less than a third temperature value; and outputting the first control signal to the switching unit according to a target duty cycle when the temperature of the insulating coolant is greater than the third temperature value and less than a fourth temperature value; wherein the first control signal is used to control the switching unit to close, and the target duty cycle is dynamically adjusted based on the temperature of the insulating coolant and the fourth temperature value, wherein the first temperature value is greater than the third temperature value and less than the fourth temperature value.

[0014] Furthermore, to achieve the above objectives, this application also provides a charging system, including at least two power modules as described above, a controller, a power distribution device, and at least one charging interface; the power distribution device is connected to the controller, each of the power modules, and each of the charging interfaces respectively; the controller is connected to each of the power modules respectively; for any power module, the controller is used to receive the temperature of the insulating coolant output by the temperature detection device in the power module, and when the temperature of the insulating coolant is less than a first temperature value, outputs a first control signal to the switching unit of the heating circuit in the power module according to a preset strategy, the switching unit is used to respond to the first control signal output by the controller and turn on the heating unit, the heating unit is used to heat the insulating coolant when the heating circuit is working.

[0015] This application introduces a heating circuit into a fully immersion power module. When the current temperature of the insulating coolant is lower than a first temperature value, the controller outputs a first control signal to the switching unit in the heating circuit to turn on the heating circuit. Based on this, the heating unit in the heating circuit can heat the insulating coolant, thereby solving the problem of reduced reliability of the charging system caused by the low temperature of the insulating coolant. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the fully immersed power module according to an embodiment of this application; Figure 2 This is one of the partial circuit diagrams of the fully immersed power module according to an embodiment of this application; Figure 3 This is a partial circuit diagram of a power module as an example of this application; Figure 4 This is a second partial circuit diagram of the fully immersed power module according to an embodiment of this application; Figure 5 This is a partial circuit diagram of the fully immersed power module according to an embodiment of this application; Figure 6 This is one of the circuit diagrams of a fully immersed power module, as shown in this application. Figure 7 This is one of the control timing diagrams of the embodiments of this application; Figure 8 This is the second control timing diagram of an embodiment of this application; Figure 9 This is the third control timing diagram of the embodiments of this application; Figure 10 This is a block diagram of the PI control in an embodiment of this application; Figure 11This is a circuit diagram of a fully immersed power module according to an embodiment of this application; Figure 12 This is the second example of a fully immersed power module circuit diagram in this application; Figure 13 This is a schematic diagram of the charging system according to an embodiment of this application; In the diagram, 100 is the heating circuit; 110 is the heating unit; 120 is the switching unit; 200 is the temperature detection device; 300 is the input EMC module; 400 is the DC / DC conversion circuit; 510 is the power module; 520 is the controller; 530 is the power distribution device; and 540 is the charging interface.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] With the rapid development of fast charging technology for electric vehicles, the heat dissipation problem of high-power modules has become increasingly prominent. Oil-based immersion liquid cooling technology, due to its excellent insulation and heat dissipation capabilities, is gradually becoming an ideal solution for high-power-density charging systems. In this design, key electronic components of the power module (such as power semiconductors, magnetic components, and electrolytic capacitors) are directly immersed in insulating coolants such as mineral oil, utilizing the high specific heat capacity of the liquid to achieve efficient thermal management.

[0020] However, because immersion liquid-cooled power modules use a special insulating coolant with high insulation and high specific heat as the heat dissipation medium, its specific heat capacity is typically more than 10 times that of air. At normal operating temperatures, this insulating coolant can efficiently absorb the heat generated by the electronic components inside the module and transfer the heat to the outside through a circulation system for heat exchange, thus ensuring the stable operation of the module. Therefore, in low-temperature or ultra-low-temperature environments, this cooling system faces significant challenges: First, electronic devices operate continuously in low-temperature insulating coolant for a much longer time than they are exposed to air. This can cause serious degradation in the performance parameters of key components such as electrolytic capacitors (e.g., equivalent series resistance, capacitance). If the charging process is started directly at this time, the output characteristics will be significantly degraded, affecting the charging performance and even damaging the equipment.

[0021] Secondly, the viscosity of the insulating coolant increases dramatically at low temperatures, which not only significantly increases the operating pressure of the circulation system but may also reduce the fluidity of the insulating coolant, leading to poor local heat dissipation and overheating within the module. This necessitates that electronic components have more reliable low-temperature resistance, or that the insulating coolant be preheated to the appropriate operating temperature for the electronic components, thereby improving the adaptability and safety of immersion liquid-cooled power modules in low-temperature environments.

[0022] Currently, power modules employing efficient circuit architectures such as the Vienna topology or single-level power supply topology, while optimizing energy efficiency, are limited by their circuit characteristics in their ability to generate sufficient heat through their own losses. They can only rely on the inherent characteristics of the devices to withstand various low-temperature operating conditions, making effective preheating during the low-temperature startup phase difficult. Therefore, the requirements for the devices are relatively high, and cost and size cannot be controlled. Thus, there is an urgent need for a solution that can actively regulate the temperature of the insulating coolant in low-temperature environments to ensure the reliability and performance stability of the power module across the entire operating range.

[0023] Based on this, the present application provides a fully immersion power module and charging system. By utilizing the power module's own structure or by adding an additional heating circuit to the power module, and by controlling the controller to heat the insulating coolant using the power module's own structure or the additional heating circuit when the current temperature of the insulating coolant is lower than a first temperature value, the problem of reduced charging system reliability caused by low temperature of the insulating coolant is solved.

[0024] To facilitate understanding, the overall hardware structure of the fully immersive power module will be described in detail below.

[0025] Figure 1 This is a schematic diagram of the structure of the fully immersed power module according to an embodiment of this application, as shown below. Figure 1 As shown, the fully submersible power module mainly consists of a sealed housing, a complete PCBA assembly, a high-insulation coolant, and inlet / outlet ports.

[0026] The sealed housing forms a completely airtight cavity, ensuring no leakage of the insulating coolant. The PCBA assembly contains all power electronic devices and control circuits, all of which are immersed in high-insulation coolant for direct heat dissipation. Temperature detection devices are installed at both the inlet and outlet ports. These devices can interact in real time with the external cold source control system via communication protocols such as CAN, 485, or 232 to control the circulation of the insulating coolant. The inlet and outlet ports employ a specially designed check valve structure to effectively prevent backflow of the insulating coolant, ensuring unidirectional circulation.

[0027] The working principle of this fully submersible power module is as follows: When the power module is in operation, the heat generated by the power devices is directly absorbed by the surrounding insulating coolant, causing the temperature of the insulating coolant to gradually rise. A built-in temperature detection device collects the temperature data of the insulating coolant in real time. When the temperature reaches a certain threshold, the charging system controller activates the external cold source circulation device. At this time, the high-temperature insulating coolant is pumped out of the power module's cavity, while the low-temperature insulating coolant, after being processed by the external cooling system, is injected into the cavity, forming a closed-loop heat exchange. The discharged high-temperature insulating coolant is cooled by the external heat dissipation device and then re-enters the circulation system, continuously providing cooling for the power module.

[0028] This dynamic temperature control mechanism ensures that power devices always operate within their optimal temperature range and enables efficient recycling of the insulating coolant, significantly improving the heat dissipation efficiency and operational reliability of the charging system. The entire process is automated through the charging system's controller, which can dynamically adjust the flow rate and circulation frequency of the insulating coolant according to actual operating conditions to achieve optimal thermal balance.

[0029] Referring to the overall structure of the fully immersed power module described above, the internal circuit structure and control strategy of the fully immersed power module in this application embodiment (i.e., the PCBA assembly part described above) will be described in detail below.

[0030] Figure 2 This is one of the partial circuit diagrams of the fully immersed power module according to an embodiment of this application, such as... Figure 2 As shown, the PCBA components in the power module may include a heating circuit 100, a temperature detection device 200, and an AC / DC conversion circuit. The heating circuit 100 includes a heating unit 110 and a switching unit 120.

[0031] The heating unit 110 is located between the AC power supply and the AC / DC conversion circuit, and the switching unit 120 is connected to the controller of the charging system. The temperature detection device 200 is used to detect the temperature of the insulating coolant. When the temperature of the insulating coolant is lower than a first temperature value, the controller outputs a first control signal to the switching unit 120 according to a preset strategy. The switching unit 120 responds to the first control signal output by the controller and turns on the heating unit 110. The heating unit 110 is used to heat the insulating coolant when the heating circuit 100 is working.

[0032] First, it should be noted that the power module in this embodiment is fully immersed in the insulating coolant, which can be any highly insulating and high specific heat liquid such as mineral oil that can be used for cooling.

[0033] Understandably, the circuit structure of a power module typically consists of a front-end AC / DC converter circuit and a rear-end DC / DC converter circuit. The AC / DC converter circuit converts the input three-phase mains power (i.e., Figure 2 The A, B, and C phases of the converter are rectified to approximately ±420V DC, with a total voltage of 840V. The output is further regulated and filtered by a large-capacity electrolytic capacitor. The DC / DC converter circuit converts the output through two or more LLC resonant cavities. At the output end, a wide range of output voltages from 50V to 1000V is achieved through a series-parallel combination of switches.

[0034] Typically, before entering the charging working state, the power module needs to go through a soft-start power-on process. Only when the DC bus voltage stabilizes and reaches the required voltage will the power module enter the charging working state. Figure 3 This is a partial circuit diagram of a power module as an example of this application. Figure 3 The AC / DC converter circuit in the diagram uses a Vienna topology. Figure 3 Taking the AC / DC conversion circuit and soft-start circuit of a medium-power module as an example, the AC power supply inputs a three-phase voltage source to the power module. After passing through the input EMC module and the soft-start circuit, the three-phase voltage source is output to the electrolytic capacitor on the DC bus through the input inductor and the switching network, forming the bus voltage.

[0035] During normal control of the power module charging, the front-end AC / DC converter circuit is responsible for stabilizing and regulating the DC bus, while simultaneously controlling the current power factor. During the soft-start power-on phase, the control sequence is as follows: first, the switch in the soft-start circuit is opened. At this time, the three-phase voltage source naturally rectifies and charges the electrolytic capacitors on the DC bus through the soft-start resistor in the soft-start circuit until the naturally rectified voltage value is reached. Generally, the instantaneous power of the soft-start resistor only needs to meet the soft-start and charging requirements of the electrolytic capacitors, so the size of the soft-start resistor is relatively small.

[0036] In addition, the auxiliary power supply of the power module is generally connected to the DC bus in the AC / DC conversion circuit to draw power from the DC bus to supply power to the power module or other devices in the charging system. For example, after the auxiliary power supply draws power from the DC bus, it can supply power to the switching transistors in the AC / DC conversion circuit so that the controller can control the switching transistors to close.

[0037] It should be noted that the auxiliary power supply of the power module can also be drawn from the AC input side of the power module. When the auxiliary power supply is drawn from the AC side of the power module, the auxiliary power supply will not affect the DC bus voltage. Therefore, it is not necessary to use the preset strategy proposed in this embodiment to judge the DC bus voltage and adjust the control signal. It is only necessary to directly use the PWM signal or high and low level to control the switching transistor to make the soft start resistor heat up. This solution is also included in the protection scope of this application.

[0038] The above describes the soft-start circuit and soft-start power-on process of commonly used power modules. The heating circuit 100 in this embodiment can be a portion of the soft-start circuit and AC / DC conversion circuit already present in the power module, or it can be a newly added heating circuit 100. If the circuit already present in the power module is used as the heating circuit 100, the original small-size, low-power soft-start resistor needs to be replaced with a high-power, large-size soft-start resistor. Combined with the preset strategy provided in this embodiment to control the switching unit 120's opening and closing, heating of the insulating coolant can be achieved. Using the circuit already present in the power module as the heating circuit 100 for heating the insulating coolant is simpler and more economical in actual implementation. It eliminates the need for an additional heating circuit 100; only the power selection and control strategy of the soft-start resistor need to be changed to achieve simultaneous soft-start and heating of the insulating coolant.

[0039] Continue to refer to Figure 2 In this embodiment, the heating circuit 100 may include a heating unit 110 and a switching unit 120. One end of the heating unit 110 is connected to an AC power source, and the other end of the heating unit 110 may be connected to the switching unit 120. Furthermore, existing power devices can be used to compose the heating unit 110, such as heating wires, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), power diodes, etc. These power devices, after being powered on, can generate heat through self-dissipation, thereby achieving the purpose of heating the insulating coolant.

[0040] Furthermore, the switching unit 120 can be connected to the controller of the charging system, and the controller can control its switching on or off. In addition, the switching unit 120 also needs to be grounded to ensure that the circuit containing the switching unit 120 and the heating unit 110 can be connected when the switching unit 120 is closed. The switching unit 120 can be composed of existing switching devices, such as relays, transistors, thyristors, etc.

[0041] The temperature detection device 200 can be a temperature sensor, infrared temperature measurement module, or other device or apparatus capable of acquiring temperature. In this embodiment, the temperature detection device 200 can be placed in the insulating coolant, and can be placed at any position in the insulating coolant. The temperature detection device 200 can be connected to a controller, and the temperature detection device 200 detects the temperature of the insulating coolant it is in and feeds the temperature of the insulating coolant back to the controller.

[0042] Before the power module enters the charging process, the charging system controller receives the temperature of the insulating coolant from the power module temperature detection device 200 and determines whether the current temperature of the insulating coolant is lower than a first temperature value. It should be noted that the first temperature value can be manually set by the operator, and the specific first temperature value can be set according to the lowest temperature at which each component can operate normally; no specific limitation is made here.

[0043] When the controller determines that the temperature of the insulating coolant is higher than or equal to a first temperature value, the controller can control the power module to enter the normal charging process, and no heating treatment of the insulating coolant is required at this time. When the controller determines that the temperature of the insulating coolant is lower than the first temperature value, the controller can first control the power module to enter the heating process of the insulating coolant. When the temperature of the insulating coolant is heated to be equal to or higher than the first temperature value, the controller can then control the power module to enter the normal charging process.

[0044] During the heating process of the power module, the controller outputs a first control signal to the switching unit 120 in the heating circuit 100. The first control signal can be a high-level control signal. The switching unit 120 receives and responds to the first control signal, thereby turning on the heating unit, and the current output by the AC power supply flows through the heating unit 110.

[0045] Therefore, when the controller determines that the temperature of the insulating coolant is lower than the minimum normal operating temperature of each device in the power module, it controls the switch unit 120 to close or close, so that current flows through the heating unit 110. The heating unit 110 generates heat through self-dissipation, thereby achieving the purpose of heating the insulating coolant in which it is located.

[0046] As described above, this application provides two types of heating circuits 100. One type uses a portion of the circuits already present in the power module as the heating circuit 100, while the other type is an additional heating circuit 100 added to the power module. The following sections will provide a detailed description of these two heating circuits 100, their corresponding preset strategies, and the remaining circuit structures of the power module.

[0047] To facilitate understanding, the following section will first introduce the first type of heating circuit 100 and the remaining circuit structures of the power module.

[0048] In some embodiments, the AC power supply includes three output terminals, and the heating unit 110 includes three heating sub-units; one end of each heating sub-unit is connected to each output terminal respectively, and the other end of each heating sub-unit is connected to an AC / DC conversion circuit; each heating sub-unit includes a heating device and a controllable switch, the heating device and the controllable switch are connected in parallel, and the controllable switch is used to disconnect when the temperature of the insulating coolant is lower than a first temperature value, thereby connecting the branch where the heating device is located.

[0049] In this embodiment, the heating unit 11 may include three heating sub-units, and the three heating sub-units are respectively arranged on the three input lines between the AC power supply and the AC / DC conversion circuit. One end of each heating sub-unit is connected to each output terminal of the AC power supply, and the other end of each heating sub-unit is connected to the AC / DC conversion circuit.

[0050] Furthermore, the heating subunit may include a heating element and a controllable switch. The heating element may be a power device capable of self-dissipating heat generation, such as a heating resistor or a heating wire. The controllable switch may be a relay, contactor, etc. No specific limitations are imposed on the heating element and the controllable switch here. The heating element and the controllable switch can be connected in parallel. In this case, when the controllable switch is open, the current input from the AC power supply will flow through the heating element.

[0051] Figure 4 This is a second partial circuit diagram of the fully immersive power module according to an embodiment of this application. For example... Figure 4 As shown, as an example, heating unit 110 includes a first resistor R1, a second resistor R2, a third resistor R3, a first switch Q1, a second switch Q2, and a third switch Q3. Switching unit 120 includes a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, an eighth switch Q8, and a ninth switch Q9.

[0052] In this circuit, one end of the first switch Q1, the second switch Q2, and the third switch Q3 are respectively connected to each input terminal of the AC power supply, and the first resistor R1, the second resistor R2, and the third resistor R3 are respectively connected in parallel across the two ends of the first switch Q1, the second switch Q2, and the third switch Q3.

[0053] The fourth switch Q4 and the fifth switch Q5 are connected in reverse series and then connected between the first switch Q1 and the midpoint of the DC bus. The sixth switch Q6 and the seventh switch Q7 are connected in reverse series and then connected between the second switch Q2 and the midpoint of the DC bus. The eighth switch Q8 and the ninth switch Q9 are connected in reverse series and then connected between the third switch Q3 and the midpoint of the DC bus.

[0054] The first resistor R1, the second resistor R2, and the third resistor R3 are the heating devices, and the first switch Q1, the second switch Q2, and the third switch Q3 are the controllable switches.

[0055] It should be noted that the first heating circuit 100 described in this embodiment utilizes a portion of the circuit structure inherent in the power module itself as the heating circuit 100, primarily utilizing the soft-start circuit and the PFC (Power Factor Correction) module in the AC / DC conversion circuit. As is well known, there are various topologies for the PFC module in the AC / DC conversion circuit, such as the Vienna topology, single-level power supply topology, conventional two-level topology, and three-level topology. Since this embodiment primarily achieves heating of the insulating coolant by changing the control strategy of the soft-start process, the aforementioned PFC module topologies are all suitable as part of the structure of the heating circuit 100 in this embodiment. This embodiment uses the Vienna topology as an example to introduce the heating circuit 100 and its preset strategy.

[0056] Specifically, the heating unit 110 in this embodiment may include a first resistor R1, a second resistor R2, a third resistor R3, a first switch Q1, a second switch Q2, and a third switch Q3. The first switch Q1, the second switch Q2, and the third switch Q3 can be existing switches such as relays or transistors. It is understood that the power module in this embodiment is connected to an AC power supply; therefore, in the front-end AC / DC conversion circuit, each module is connected via three input lines: phase A, phase B, and phase C. Similarly, in this embodiment, the first switch Q1, the second switch Q2, and the third switch Q3 are respectively disposed on the three input lines, and one end of each switch is connected to one of the three input terminals of the AC power supply.

[0057] In some embodiments, the switching unit 120 is disposed in the AC / DC conversion circuit of the power module, which may include a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a first inductor L1, a second inductor L2, and a third inductor L3.

[0058] The other end of the first switch Q1 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 is connected to one end of the first inductor L1, the other end of the first inductor L1 is connected to the first end of the fourth switch Q4, forming the first node N1, the second end of the fourth switch Q4 is connected to the second end of the fifth switch Q5, and the first end of the fifth switch Q5 is connected to the midpoint of the DC bus in the AC / DC conversion circuit. The fourth switch Q4 and the fifth switch Q5 are connected in reverse series.

[0059] The other end of the second switch Q2 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5 is connected to one end of the second inductor L2, the other end of the second inductor L2 is connected to the first end of the sixth switch Q6, forming the second node N2, the second end of the sixth switch Q6 is connected to the second end of the seventh switch Q7, and the first end of the seventh switch Q7 is connected to the midpoint of the DC bus in the AC / DC converter circuit. The sixth switch Q6 and the seventh switch Q7 are connected in reverse series.

[0060] The other end of the third switch Q3 is connected to one end of the sixth resistor R6, the other end of the sixth resistor R6 is connected to one end of the third inductor L3, the other end of the third inductor L3 is connected to the first end of the eighth switch Q8, forming the third node N3, the second end of the eighth switch Q8 is connected to the second end of the ninth switch Q9, and the first end of the ninth switch Q9 is connected to the midpoint of the DC bus in the AC / DC converter circuit. The eighth switch Q8 and the ninth switch Q9 are in reverse series configuration.

[0061] In addition, the AC / DC conversion circuit may also include a first electrolytic capacitor C1 and a second electrolytic capacitor C2, wherein the first electrolytic capacitor C1 and the second electrolytic capacitor C2 are connected in series, and the first electrolytic capacitor C1 and the second electrolytic capacitor C2 are disposed on the DC bus, with the midpoint of the DC bus between the first electrolytic capacitor C1 and the second electrolytic capacitor C2.

[0062] It should be noted that switches Q4, Q5, Q6, Q7, Q8, and Q9 can be NMOS transistors, SiC MOS transistors, etc. If NMOS transistors are used, the first and second terminals of switches Q4, Q5, Q6, Q7, Q8, and Q9 can be either the source or drain, and the third terminal is the gate. The third terminals of switches Q1 through Q9 are all connected to the controller.

[0063] It is understandable that the soft-start resistor in a conventional power module only needs to meet the requirements of the soft-start process, so low-power, small-size resistors are usually chosen. However, the first resistor R1, the second resistor R2, and the third resistor R3 in this embodiment need to meet not only the soft-start requirement but also the heating requirement. Therefore, unlike existing power modules, the first resistor R1, the second resistor R2, and the third resistor R3 in this embodiment need to be high-power, large-size resistors to meet both the soft-start and heating requirements, so that the steady-state power (under cryogenic liquid immersion conditions) can reach the heating power requirement.

[0064] In some implementations, the AC / DC conversion circuit may further include a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6.

[0065] In this configuration, the anode of the first diode D1 is connected to the first node N1, and the cathode of the first diode D1 is connected to one end of the first electrolytic capacitor C1. The cathode of the second diode D2 is connected to the first node N1, and the anode of the second diode D2 is connected to one end of the second electrolytic capacitor C2. The anode of the third diode D3 is connected to the second node N2, and the cathode of the third diode D3 is connected to one end of the first electrolytic capacitor C1. The cathode of the fourth diode D4 is connected to the second node N2, and the anode of the fourth diode D4 is connected to one end of the second electrolytic capacitor C2. The anode of the fifth diode D5 is connected to the third node N3, and the cathode of the fifth diode D5 is connected to one end of the first electrolytic capacitor C1. The cathode of the sixth diode D6 is connected to the third node N3, and the anode of the sixth diode D6 is connected to one end of the third electrolytic capacitor.

[0066] Figure 5 This is a partial circuit diagram of the fully immersive power module according to an embodiment of this application. In some embodiments, the structure of the switching unit 120 and the AC / DC conversion circuit can also be as follows: Figure 5 The structure shown is as follows. Figure 5 As shown, the heating unit 110 includes a first resistor R1, a second resistor R2, a third resistor R3, a first switch Q1, a second switch Q2, and a third switch Q3; the switch unit 120 includes a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a seventh switch Q7, an eighth switch Q8, and a ninth switch Q9.

[0067] In this configuration, one end of the first switch Q1, the second switch Q2, and the third switch Q3 are respectively connected to the respective input terminals of the AC power supply; the first resistor R1, the second resistor R2, and the third resistor R3 are respectively connected in parallel across the two ends of the first switch Q1, the second switch Q2, and the third switch Q3; the fourth switch Q4 and the fifth switch Q5 are connected in series across the two ends of the DC bus; the sixth switch Q6 and the seventh switch Q7 are connected in series across the two ends of the DC bus; the eighth switch Q8 and the ninth switch Q9 are connected in series across the two ends of the DC bus; the other end of the first switch Q1 is connected between the fourth switch Q4 and the fifth switch Q5; the other end of the second switch Q2 is connected between the sixth switch Q6 and the seventh switch Q7; and the other end of the third switch Q3 is connected between the eighth switch Q8 and the ninth switch Q9.

[0068] The difference between this embodiment and the switching unit 120 and AC / DC conversion circuit in the previous embodiment is that the AC / DC conversion circuit in this embodiment is a two-level topology. The AC / DC conversion circuit includes a first electrolytic capacitor C1, which is disposed on the DC bus. Secondly, the fourth switch Q4 and the fifth switch Q5 are connected in series, with a first node N1 between them. The fourth switch Q4 and the fifth switch Q5 are connected in series to the two ends of the DC bus (i.e., the two ends of the first electrolytic capacitor C1). The sixth switch Q6 and the seventh switch Q7 are connected in series, with a second node N2 between them. The sixth switch Q6 and the seventh switch Q7 are connected in series to the two ends of the DC bus. The eighth switch Q8 and the ninth switch Q9 are connected in series, with a third node N3 between them. The eighth switch Q8 and the ninth switch Q9 are connected in series to the two ends of the DC bus. Finally, the other end of the first inductor L1 is connected to the first node N1, the other end of the second inductor L2 is connected to the second node N2, and the other end of the third inductor L3 is connected to the third node N3. Figure 6 This is a circuit diagram of an example fully immersed power module of this application, such as... Figure 6 As shown, in some embodiments, the power module also includes an input EMC module 300 and a DC / DC conversion circuit 400.

[0069] The input EMC module 300 can be placed between the heating unit 110 and the AC power supply. The input EMC module 300 (electromagnetic compatibility module) is used to ensure the stable operation of the charging system in the electromagnetic environment, while reducing its interference to the power grid and other equipment, and preventing electromagnetic noise in the power grid from entering the power module.

[0070] Continue to refer to Figure 6 The DC / DC converter circuit 400 may include a transformer rectifier module, an output switch module, an output electrolysis module, and a reverse protection module.

[0071] One end of the transformer-rectifier module is connected to the AC / DC conversion circuit, and the other end of the transformer-rectifier module is connected to one end of the output switch module. The output switch module is connected to the first input terminal and the second output terminal of the output electrolysis module. The first output terminal of the output electrolysis module is connected to one end of the reverse protection module, the second output terminal of the output electrolysis module is connected to the negative terminal of the load, and the other end of the reverse protection module is connected to the positive terminal of the load.

[0072] Specifically, the transformer-rectifier module may include a first transformer T1, a second transformer T2, a first rectifier bridge, and a second rectifier bridge. The primary windings of both the first transformer T1 and the second transformer T2 are connected in parallel across the DC bus in the AC / DC converter circuit. The two input terminals of the first rectifier bridge are connected to the secondary winding of the first transformer T1, and the two output terminals of the first rectifier bridge are connected to the output switch module. The two input terminals of the second rectifier bridge are connected to the secondary winding of the second transformer T2, and the two output terminals of the second rectifier bridge are connected to the output switch module. Both the first and second rectifier bridges can be composed of four rectifier diodes. The specific structures of the first and second rectifier bridges can be found in [reference needed]. Figure 6 The structure of the text will not be elaborated here.

[0073] The output switch module may include a first relay K1, a second relay K2, a third relay K3, and a fourth relay K4. One end of the first relay K1 is connected to the first output terminal of the first rectifier bridge, and the other end of the first relay K1 is connected to the first output terminal of the second rectifier bridge. One end of the second relay K2 is connected to the second output terminal of the first rectifier bridge, and the other end of the second relay K2 is connected to the second output terminal of the second rectifier bridge. One end of the third relay K3 is connected to the second output terminal of the first rectifier bridge, and the other end of the third relay K3 is connected between the third electrolytic capacitor C3 and the fourth electrolytic capacitor C4 in the output electrolytic module. One end of the fourth relay K4 is connected to the first output terminal of the second rectifier bridge, and the other end of the fourth relay K4 is connected between the third electrolytic capacitor C3 and the fourth electrolytic capacitor C4.

[0074] The third electrolytic capacitor C3 and the fourth electrolytic capacitor C4 are connected in series. The output electrolytic module may also include a fourth inductor L4. The primary side of the fourth inductor L4 can be connected to the two ends of the series connection between the third electrolytic capacitor C3 and the fourth electrolytic capacitor C4. One end of the secondary coil of the fourth inductor L4 can be connected to the reverse protection module, and the other end of the secondary coil of the fourth inductor L4 can be connected to the negative terminal of the load.

[0075] The anti-reverse module may include an anti-reverse diode Dx, the cathode of which can be connected to the positive terminal of the load, and the anode of which is connected to the other end of the secondary winding of the fourth inductor L4. It should be noted that in charging station applications, the load typically refers to the battery load in the electric vehicle. Furthermore, the DC / DC converter circuit 400 described above is an example; other structures can also be used for the power module's DC / DC converter circuit 400, which will not be elaborated upon here.

[0076] Referring to the circuit diagram of the fully immersive power module above, the control strategy of the fully immersive power module will be described in detail below.

[0077] If the first type of heating circuit 100 is adopted (i.e., using its own circuit structure as the heating circuit 100), the embodiments of this application provide the following three preset strategies to control the heating unit 110 to heat the insulating coolant. The three preset strategies are described in detail below.

[0078] In some implementations, the preset strategy may include: outputting a second control signal to the switching unit 120, and outputting a first control signal to the switching unit 120 when it is determined that the voltage of the DC bus reaches a first threshold, and repeating the above steps when it is determined that the voltage of the DC bus reaches a second threshold, until the temperature of the insulating coolant reaches a second temperature value.

[0079] The second control signal is used to control the switch unit 120 to turn off, the first control signal is used to control the switch unit 120 to close, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

[0080] It should be noted that the first threshold can be set based on the bus voltage after soft-start natural rectification. For example, the first threshold can be set slightly lower than the bus voltage after natural rectification. This bus refers to the DC bus in the AC / DC converter circuit. The second threshold can be set based on the minimum voltage required to maintain auxiliary power supply. For example, the second threshold can be set higher than the minimum voltage required to maintain auxiliary power supply. Furthermore, the second temperature value can be set slightly higher than the first temperature value. For example, the second temperature value can be set 5°C higher than the first temperature value.

[0081] Specifically, before the power module is turned on, the controller of the charging system can first receive the temperature of the insulating coolant sent by the temperature detection device 200 in the power module, and determine whether the current temperature of the insulating coolant is less than the first temperature value. If the current temperature of the insulating coolant is less than the first temperature value, the controller controls the heating unit 110 and the switching unit 120 to perform soft start and heating of the insulating coolant according to the preset strategy.

[0082] Figure 7 This is one of the control timing diagrams in the embodiments of this application. Figure 7 The control timing diagram for the controller's PWM wave and DC bus voltage is shown. The horizontal axis represents time, the vertical axis corresponding to the DC bus voltage represents voltage, and the vertical axis corresponding to the PWM wave represents the amplitude of the PWM wave.

[0083] refer to Figure 4 and Figure 7First, when the current temperature of the insulating coolant is lower than the first temperature value, the AC power supply is turned on, and the first switch Q1, the second switch Q2, and the third switch Q3 are in the open state. The controller outputs the second control signal (i.e., PWM wave) to the switching unit 120, causing the switching unit 120 to turn off. At this time, the three-phase voltage charges the electrolytic capacitor on the DC bus through the first resistor R1, the second resistor R2, and the third resistor R3, and the voltage of the electrolytic capacitor rises slowly. This process is the soft start process of the power module, which raises the voltage of the electrolytic capacitor on the DC bus through natural rectification.

[0084] Furthermore, when the voltage of the electrolytic capacitor rises to the first threshold (i.e., reaches t0), the soft start is considered to be basically achieved, and the auxiliary power supply can draw power from the DC bus to power the controller and other devices. At this time, the controller can output the first control signal to the switching unit 120, causing all six switches of the switching unit 120 (i.e., the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, the eighth switch Q8, and the ninth switch Q9) to close. The three-phase soft start resistors (i.e., the first resistor R1, the second resistor R2, and the third resistor R3) form a Y-type circuit. The first resistor R1, the second resistor R2, and the third resistor R3 bear the phase voltage and related power loss, thus generating heat. The first resistor R1, the second resistor R2, and the third resistor R3 heat the insulating coolant. Since the switching unit 120 is in the conducting state, natural rectification no longer continues, and the voltage of the DC bus will slowly decrease, such as... Figure 7 The t0-t1 stage is shown.

[0085] When the voltage of the electrolytic capacitor drops to the second threshold (i.e., reaches t1), the controller outputs a second control signal to the switching unit 120, causing the switching unit 120 to be in the off state. The power module then re-enters the soft-start phase, performing natural rectification, which causes the DC bus voltage to rise again, ensuring continuous power supply to the auxiliary power source. This process is repeated until the temperature of the insulating coolant received by the controller reaches the second temperature value. At this point, this control strategy can be terminated, and the original soft-start control strategy can be resumed.

[0086] Under the control of the above-mentioned preset strategy, the soft start process and the insulating coolant heating process are carried out alternately, which can not only meet the needs of starting and maintaining the auxiliary power bus, but also use the soft start resistors (i.e., the first resistor R1, the second resistor R2 and the third resistor R3) to heat the insulating coolant, thereby increasing the temperature of the power module.

[0087] In some implementations, the preset strategy may include: outputting a second control signal to the switching unit 120, and when it is determined that the voltage of the DC bus reaches a first threshold, outputting a pulse-type control signal to the switching unit 120 according to a preset duty cycle, and when it is determined that the voltage of the DC bus reaches a second threshold, repeating the above steps until the temperature of the insulating coolant reaches a second temperature value.

[0088] The second control signal is used to control the switch unit 120 to turn off. When the pulsed control signal is at a high level, the switch unit 120 is closed, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

[0089] The difference from the aforementioned preset strategy is that, in the preset strategy of this embodiment, when outputting the first control signal to the switching unit 120, a pulse-type first control signal can be output.

[0090] Figure 8 This is the second control timing diagram in the embodiments of this application. Figure 8 The control timing diagram for the controller's PWM wave and DC bus voltage is shown. The horizontal axis represents time, the vertical axis corresponding to the DC bus voltage represents voltage, and the vertical axis corresponding to the PWM wave represents the amplitude of the PWM wave.

[0091] refer to Figure 4 and Figure 8 First, when the current temperature of the insulating coolant is lower than the first temperature value, the AC power supply is turned on, and the first switch Q1, the second switch Q2, and the third switch Q3 are in the open state. The controller outputs the second control signal (i.e., PWM wave) to the switching unit 120, causing the switching unit 120 to turn off. At this time, the three-phase voltage charges the electrolytic capacitor on the DC bus through the first resistor R1, the second resistor R2, and the third resistor R3, and the voltage of the electrolytic capacitor rises slowly. This process is the soft start process of the power module, which raises the voltage of the electrolytic capacitor on the DC bus through natural rectification.

[0092] Furthermore, when the voltage of the electrolytic capacitor rises to the first threshold (i.e., reaches t0), the soft start is considered to be basically achieved, and the auxiliary power supply can draw power from the DC bus to power the controller and other devices. At this time, the controller can output a pulse-type first control signal to the switching unit 120 according to a preset duty cycle, causing all six switches of the switching unit 120 (i.e., the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, the eighth switch Q8, and the ninth switch Q9) to close. The three-phase soft start resistors (i.e., the first resistor R1, the second resistor R2, and the third resistor R3) form a Y-type circuit. The first resistor R1, the second resistor R2, and the third resistor R3 bear the phase voltage and related power loss, thus generating heat. The first resistor R1, the second resistor R2, and the third resistor R3 heat the insulating coolant. Since the switching unit 120 is in the conducting state, natural rectification no longer continues, and the voltage of the DC bus will slowly decrease, such as... Figure 8 The t0-t1 stage is shown.

[0093] It should be noted that the preset duty cycle can be determined based on the resistance values ​​of the first resistor R1, the second resistor R2, and the third resistor R3, the required power of the auxiliary power supply, and the capacitance value of the electrolytic capacitor on the DC bus. For example, if the resistance values ​​of the first resistor R1, the second resistor R2, and the third resistor R3 are large, their heat generation per unit time will also be large, so the preset duty cycle can be set relatively small. If the required power of the auxiliary power supply is large, it means that the DC bus voltage may drop faster, so the preset duty cycle can also be set relatively small. If the capacitance value of the electrolytic capacitor is large, the electrolytic capacitor will store more electrical energy, so the preset duty cycle can be set relatively large.

[0094] If the preset duty cycle is inappropriate and causes the voltage to drop below the second threshold, the waveform can be stopped. If the preset duty cycle is large and appropriate, it can meet both the heating time requirement and the natural rectification requirement.

[0095] When the voltage of the electrolytic capacitor drops to the second threshold (i.e., reaches t1), the controller outputs a second control signal to the switching unit 120, causing the switching unit 120 to be in the off state. The power module then re-enters the soft-start phase, performing natural rectification, which causes the DC bus voltage to rise again, ensuring continuous power supply to the auxiliary power source. This process is repeated until the temperature of the insulating coolant received by the controller reaches the second temperature value. At this point, this control strategy can be terminated, and the original soft-start control strategy can be resumed.

[0096] In addition, due to the high-frequency operation of the switching unit 120, it will generate switching losses and also play a certain role in heating. At the same time, it can share some of the transient power of the resistor and play a role in protecting the resistor.

[0097] In some implementations, the preset strategy may include: outputting a second control signal to the switching unit 120, and when it is determined that the voltage of the DC bus reaches a first threshold, outputting a pulse-type control signal to the switching unit 120 according to a target duty cycle, and when it is determined that the voltage of the DC bus reaches a second threshold, repeating the above steps until the temperature of the insulating coolant reaches a second temperature value.

[0098] The target duty cycle is dynamically adjusted based on the set voltage and the DC bus voltage. The second control signal is used to control the switch unit 120 to turn off. When the pulse control signal is in the first case, the switch unit 120 is closed, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

[0099] The difference between this embodiment and the second preset strategy is that, in the preset strategy, when outputting the first control signal to the switching unit 120, the first control signal can be output in a pulse-like manner according to the dynamic target duty cycle.

[0100] Figure 9 This is the third control timing diagram in the embodiments of this application. Figure 9 The control timing diagram for the controller's PWM wave and DC bus voltage is shown. The horizontal axis represents time, the vertical axis corresponding to the DC bus voltage represents voltage, and the vertical axis corresponding to the PWM wave represents the amplitude of the PWM wave.

[0101] refer to Figure 4 and Figure 9 First, when the current temperature of the insulating coolant is lower than the first temperature value, the AC power supply is turned on, and the first switch Q1, the second switch Q2, and the third switch Q3 are in the open state. The controller outputs the second control signal (i.e., PWM wave) to the switching unit 120, causing the switching unit 120 to turn off. At this time, the three-phase voltage charges the electrolytic capacitor on the DC bus through the first resistor R1, the second resistor R2, and the third resistor R3, and the voltage of the electrolytic capacitor rises slowly. This process is the soft start process of the power module, which raises the voltage of the electrolytic capacitor on the DC bus through natural rectification.

[0102] Furthermore, when the voltage of the electrolytic capacitor rises to the first threshold (i.e., reaches t0), the soft start is considered to be basically achieved, and the auxiliary power supply can draw power from the DC bus to power the controller and other devices. At this time, the controller can output a pulse-type first control signal to the switching unit 120 according to the target duty cycle, causing all six switches of the switching unit 120 (i.e., the fourth switch Q4, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, the eighth switch Q8, and the ninth switch Q9) to close. The three-phase soft start resistors (i.e., the first resistor R1, the second resistor R2, and the third resistor R3) form a Y-type circuit. The first resistor R1, the second resistor R2, and the third resistor R3 bear the phase voltage and related power loss, thus generating heat. The first resistor R1, the second resistor R2, and the third resistor R3 heat the insulating coolant. Since the switching unit 120 is in the conducting state, natural rectification no longer continues, and the voltage of the DC bus will slowly decrease, such as... Figure 9 The t0-t1 stage is shown.

[0103] When the voltage of the electrolytic capacitor drops to the second threshold (i.e., reaches t1), the controller outputs a second control signal to the switching unit 120, causing the switching unit 120 to be in the off state. The power module then re-enters the soft-start phase, performing natural rectification, which causes the DC bus voltage to rise again, ensuring continuous power supply to the auxiliary power source. This process is repeated until the temperature of the insulating coolant received by the controller reaches the second temperature value. At this point, this control strategy can be terminated, and the original soft-start control strategy can be resumed.

[0104] It should be noted that the target duty cycle can be dynamically adjusted based on the set voltage and the DC bus voltage. The dynamic adjustment method can be: using hysteresis to adjust.

[0105] Specifically, an intermediate voltage value can be determined between the first threshold and the second threshold, and this intermediate voltage value can be used as the set voltage. A PI control loop is used to output the target duty cycle. By outputting a pulsed first control signal according to the target duty cycle, the DC bus voltage can be accurately controlled at the set voltage.

[0106] Figure 10 This is a block diagram of the PI control in an embodiment of this application. Figure 10 As shown, the controller can acquire the DC bus voltage in real time and use a PI control strategy to calculate the difference between the current DC bus voltage Vdc and the set voltage Vdc*, obtaining the voltage difference value. After multiplying the voltage difference value by -1, the input value is sent to the PI regulator. The PI regulator outputs a PWM signal to control the switching unit 120 to turn on and off. The PWM signal output by the PI regulator is a pulse-type control signal output according to the target duty cycle.

[0107] It should be noted that when the PWM signal is high (first control signal), the DC bus voltage drops due to the lack of natural rectification; when the PWM signal is low (second control signal), the switching unit 120 is turned off, and the DC bus voltage rises due to natural rectification. Therefore, the voltage difference needs to be multiplied by -1 in reverse before PI control output.

[0108] The above-mentioned dual-line hysteresis voltage setting of the bus voltage, with the second threshold higher than the minimum sustaining voltage of the auxiliary power supply and the first threshold lower than the natural rectification determined by the current input voltage (the natural rectification is calculated based on the input voltage and varies with the input voltage), ensures that the DC bus can stably provide an input source to the auxiliary power supply and also enables the heating of the insulating coolant. Furthermore, the third preset strategy determines the target duty cycle through feedback adjustment and then outputs a pulse control signal according to the target duty cycle, achieving dynamic adjustment of the target duty cycle. In addition, due to the high-frequency operation of the switching unit 120, it generates switching losses, which also contribute to heating and share some of the transient power of the resistor, thus protecting the resistor.

[0109] The above are three preset strategies. These three preset strategies can also be used in other topologies, for example, in the two-level topology of the above embodiments (such as...). Figure 5 In the example shown, the difference is that when the control signal is high, all three upper transistors or all three lower transistors can be turned on. In this way, the soft-start resistors (i.e., the first resistor R1, the second resistor R2, and the third resistor R3) form a Y-type circuit with the three-phase power grid. When the control signal is low capacitance, the switching unit 120 is turned off and natural rectification is performed, which causes the DC bus voltage to rise. The control logic can be referred to the control logic above, and will not be repeated here.

[0110] It is worth mentioning that the above description uses two-level and Vienna three-level topologies as examples. Other topologies, such as T-type three-level, I-type three-level, or high-level topologies, are similar.

[0111] The structure of the added heating circuit 100 and its preset strategy will be described in more detail below.

[0112] In some embodiments, the heating unit 110 includes multiple heating sub-units, the switching unit 120 includes at least one switching sub-unit, the heating sub-unit includes at least one heating device, and the switching sub-unit includes a switching transistor; the heating devices are connected in series and / or in parallel, the first end of the switching transistor is connected to the corresponding heating sub-unit, the second end of the switching transistor is grounded, and the third end of the switching transistor is connected to the controller.

[0113] In this embodiment, there can be multiple heating sub-units and multiple switching sub-units. The more heating sub-units there are, the higher the heating efficiency. One end of each heating sub-unit can be connected to any one of the three input lines. For example, if there are 3 heating sub-units, they can be connected to the three input lines respectively. If there are 5 heating sub-units, two heating sub-units can be connected to any two of the three input lines, and the remaining heating sub-unit can be connected to the other input line.

[0114] The other end of each heating subunit is connected to the corresponding switching subunit. One switching subunit can be connected to multiple heating subunits. The other end of the switching subunit is connected to the N line.

[0115] Figure 11 This is a circuit diagram of a fully immersion power module according to an embodiment of this application. Figure 11 As shown, in some embodiments, the heating unit 110 includes three heating sub-units. The first end of each heating sub-unit is connected to one of the three input lines respectively, and the second end of each heating sub-unit is connected to a corresponding switch sub-unit. When the number of switch sub-units is 1, the second end of each heating sub-unit is connected to the switch sub-unit. When the number of switch sub-units is 2, the second ends of any two heating sub-units are connected to one switch sub-unit, and the second ends of the remaining heating sub-units are connected to another switch sub-unit. When the number of switch sub-units is 3, each heating sub-unit is connected to each switch sub-unit respectively.

[0116] It should be noted that, Figure 11 The structure of the heating circuit 100 shown is a specific example of a series configuration, and it can also be configured as follows: Figure 11 Using the circuit structure in the example as a reference, the number and combination connection of the heating sub-unit and the switching sub-unit are changed to obtain more heating circuit topologies.

[0117] Specifically, the heating unit 110 may include three heating sub-units, and the switching unit 132 may include at least one switching sub-unit. One end of each heating sub-unit is connected to one of the three input lines, with a one-to-one correspondence between the heating sub-unit and the three input lines. The connection method of the other end of the heating sub-unit can be divided into the following three cases: In the first scenario, when there are three switching subunits, the other end of each heating subunit is connected to one of the three corresponding switching subunits, with a one-to-one correspondence between the heating subunits and the switching subunits. For example, if heating unit 110 includes heating subunit 1, heating subunit 2, and heating subunit 3, and switching unit 120 includes switching subunit 1, switching subunit 2, and switching subunit 3, with three input lines representing phase A, phase B, and phase C respectively, then one end of heating subunit 1 can be connected to the phase A input line, and the other end to switching subunit 1; one end of heating subunit 2 can be connected to the phase B input line, and the other end to switching subunit 2; one end of heating subunit 3 can be connected to the phase C input line, and the other end to switching subunit 3.

[0118] The second approach involves having two switching subunits. The other ends of any two heating subunits are connected to one switching subunit, and the other end of the remaining heating subunit is connected to the other switching subunit. For example, if heating unit 110 includes heating subunit 1, heating subunit 2, and heating subunit 3, and switching unit 120 includes switching subunit 1 and switching subunit 2, with three input lines representing phase A, phase B, and phase C respectively, then one end of heating subunit 1 can be connected to the phase A input line, one end of heating subunit 2 can be connected to the phase B input line, and the other ends of both heating subunit 1 and heating subunit 2 are connected to switching subunit 1; one end of heating subunit 3 can be connected to the phase C input line, and the other end of heating subunit 3 is connected to switching subunit 2. Other combinations can also be used in this example, which will not be elaborated here.

[0119] The third method involves having only one switching subunit, with the other ends of all three heating subunits connected to this switching subunit. For example, heating unit 110 includes heating subunit 1, heating subunit 2, and heating subunit 3, and switching unit 120 includes switching subunit 1. The three input lines are the input lines for phase A, phase B, and phase C, respectively. One end of heating subunit 1, heating subunit 2, and heating subunit 3 can be connected to the input lines for phase A, phase B, and phase C, respectively, while the other end of heating subunit 1, heating subunit 2, and heating subunit 3 is connected to switching subunit 1.

[0120] In some embodiments, the heating subunit includes at least one heating element, and the switching subunit includes a switching transistor. The heating elements are connected in series and / or in parallel; the first terminal of the switching transistor is connected to the corresponding heating subunit, the second terminal of the switching transistor is grounded, and the third terminal of the switching transistor is connected to the controller.

[0121] It should be noted that the heating element can be a heating resistor or a heating wire. If a heating resistor is used, a resistor with a smaller resistance value can be selected. Under the same voltage, a smaller resistance value results in a larger current flow, increasing power dissipation and generating more heat during self-dissipation, thus leading to higher heating efficiency. However, when selecting a heating resistor, it is also necessary to ensure that the current flowing through it does not exceed the maximum allowable current during soft-start. Furthermore, the switching transistor can be a MOSFET, IGBT, transistor, mechanical relay, or SCR, etc. No specific limitations are imposed on the switching transistor here.

[0122] In this embodiment, each heating subunit may include multiple heating resistors, which can be set in series and parallel, and then connected in the circuit.

[0123] Figure 12 This is a circuit diagram of an example fully immersed power module from this application. Figure 12 As shown, as an example, heating unit 110 includes three heating sub-units, each including a heating resistor. Switching unit 120 also includes three switching sub-units, each including an NMOS switch. One end of the three heating resistors is connected to the input lines of phase A, phase B, and phase C, respectively. The other end of the three heating resistors is connected to the first terminal (i.e., source or drain) of the three NMOS switches, respectively. The second terminal (i.e., source or drain) of the three NMOS switches is grounded, and the third terminal (i.e., gate) of the three NMOS switches is connected to the controller.

[0124] In some embodiments, the power module further includes an input EMC module 300; one end of the input EMC module 300 is connected to an AC power source, and the other end of the input EMC module 300 is connected to an AC / DC conversion circuit; one end of the heating unit 110 is connected between the AC power source and the input EMC module 300; or, one end of the heating unit 110 is connected between the input EMC module 300 and the AC / DC conversion circuit.

[0125] Specifically, if the heating circuit 100 can be located between the AC power supply and the input EMC module 300, then one end of the heating unit 110 is connected to the input line between the AC power supply and the input EMC module 300. The specific connection method can be referred to the connection method described above, and will not be repeated here. If the heating circuit 100 can be located between the input EMC module 300 and the AC / DC conversion circuit, then one end of the heating unit 110 is connected to the input line between the input EMC module 300 and the AC / DC conversion circuit. The specific connection method can be referred to the connection method described above, and will not be repeated here.

[0126] If the second heating circuit 100 (i.e., the added heating circuit 100) is adopted, the preset strategy of this application embodiment can be: when the current temperature of the insulating coolant is less than the third temperature value, the controller is used to continuously output a first control signal to the switching unit 120; when the current temperature of the insulating coolant is greater than the third temperature value and less than the fourth temperature value, the controller is used to output a first control signal to the switching unit 120 according to the target duty cycle; wherein, the target duty cycle is dynamically adjusted based on the current temperature of the insulating coolant and the fourth temperature value, and the first temperature value is greater than the third temperature value and less than the fourth temperature value.

[0127] It should be noted that the third temperature value can be less than the first temperature value; for example, the third temperature value can be equal to the first temperature value -10℃. The fourth temperature value can be set to the temperature at which each component in the power module can operate normally, i.e., the temperature value required for the heating process. This can be set manually by the operator; for example, the fourth temperature value can be equal to the first temperature value +5℃.

[0128] In some implementations, the switching unit 120 is in the off state when the power module enters the charging operation mode.

[0129] Specifically, before the power module is put into use, the controller first receives the current temperature of the insulating coolant output by the temperature detection device 200 and determines whether the current temperature of the insulating coolant is lower than a first temperature value. If the current temperature of the insulating coolant is lower than the first temperature value, the heating function of the power module is activated. After the heating function of the power module is activated, the controller can determine again whether the current temperature of the insulating coolant is lower than a third temperature value. If the current temperature of the insulating coolant is lower than the third temperature value, the controller can output a continuous first control signal to all three switching subunits, causing all three switching subunits to close, and the corresponding three heating subunits to continuously heat the insulating coolant.

[0130] If, before the power module is put into use, or during the heating process, the controller determines that the current temperature of the insulating coolant is higher than the third temperature value but lower than the fourth temperature value, the controller can choose to output a pulsed first control signal to all three switching subunits, or it can choose to output a pulsed first control signal to some of the switching subunits. Furthermore, the controller can output the pulsed first control signal according to a target duty cycle. It should be noted that the target duty cycle refers to the ratio of the first control signal to the total time, and the target duty cycle can be dynamically adjusted based on the current temperature of the insulating coolant and the fourth temperature value. Specifically, a PI control method can be used to gradually bring the current temperature of the insulating coolant closer to the fourth temperature value.

[0131] Therefore, by simply changing the power rating of the soft-start resistor, localized heating of the module can be achieved using the heat generated by the soft-start resistor. No additional circuitry or drive circuitry is required; heating can be achieved simply through control waveform generation. Alternatively, by modifying the power module's circuitry and using the heating resistor to heat the insulating coolant, the internal temperature of the power module's insulating coolant can be rapidly raised to a predetermined temperature. This ensures that the electronic components within the power module operate in an optimal temperature environment, thereby improving the overall reliability of the module and resolving the issue of reduced charging system reliability caused by low-temperature insulating coolant.

[0132] Based on the above embodiments, this application also provides a charging system. Figure 13 This is a schematic diagram of the charging system according to an embodiment of this application. Figure 13 As shown, the charging system may include at least two power modules 510 as described above, a controller 520, a power distribution device 530, and at least one charging interface 540. The power distribution device 530 is connected to the controller 520, each power module 510, and each charging interface 540. The controller 520 is connected to each power module 510. For any power module 510, the controller 520 receives the temperature of the insulating coolant output by the temperature detection device 200 in the power module 510. When the temperature of the insulating coolant is lower than a first temperature value, the controller outputs a first control signal to the switching unit 120 of the heating circuit 100 in the power module 510 according to a preset strategy. The switching unit 120 responds to the first control signal output by the controller 520 and turns on the circuit where the heating unit 110 is located.

[0133] In addition, the power module 510 is used to convert the AC power of the power grid into DC power and provide it to the charging interface 540. The controller 520 is used to obtain the power demand of each charging interface 540 and generate a scheduling command according to the connection relationship of the controllable switch in the power distribution device 530 and the power demand. The power distribution device 530 is used to control the opening or closing of the controllable switch according to the scheduling command so as to distribute the output power of each power module 510 to each charging interface 540.

[0134] In one optional implementation, the charging system provided in this application is an integrated DC charging pile, with the charging interface 540 used to connect the charging gun, which is then connected to the main unit of the charging system via a gun mount on the main body of the charging system.

[0135] In one optional implementation, the charging system provided in this application is a split-type DC charging pile. The charging system also includes multiple charging terminals. The charging interface 540 is used to connect the charging terminals. The charging terminals are set separately from the main body of the charging system. The charging terminals are equipped with a single charging gun or dual charging guns for outputting power to electric vehicles.

[0136] It should be noted that for details not disclosed in the charging system of this embodiment, please refer to the details disclosed in the embodiment of the power module 510 in this specification, which will not be repeated here.

[0137] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A fully immersion power module, characterized in that, The power module is used in a charging system. The power module includes a PCBA assembly, which is fully immersed in an insulating coolant. The PCBA assembly includes a heating circuit, a temperature detection device, and an AC / DC conversion circuit. The heating circuit includes a heating unit and a switching unit. The heating unit is disposed between the AC power supply and the AC / DC conversion circuit, and the switching unit is connected to the controller of the charging system. The temperature detection device is used to detect the temperature of the insulating coolant. The controller is used to output a first control signal to the switching unit according to a preset strategy when the temperature of the insulating coolant is less than a first temperature value. The switching unit is used to respond to the first control signal output by the controller and turn on the heating unit. The heating unit is used to heat the insulating coolant when the heating circuit is working. The PCBA assembly also includes an AC / DC conversion circuit, which is connected to the heating unit. The switching unit is disposed in the AC / DC conversion circuit and is used to control the DC bus voltage of the AC / DC conversion circuit. The preset strategy includes: outputting a second control signal to the switching unit, and when it is determined that the DC bus voltage reaches a first threshold, outputting the first control signal to the switching unit, and when it is determined that the DC bus voltage reaches a second threshold, repeating the above steps until the temperature of the insulating coolant reaches a second temperature value. Wherein, the second control signal is used to control the switch unit to turn off, the first control signal is used to control the switch unit to close, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

2. The fully immersion power module according to claim 1, characterized in that, The PCBA assembly also includes an AC / DC conversion circuit, which is connected to the heating unit. The switching unit is disposed in the AC / DC conversion circuit and is used to control the DC bus voltage of the AC / DC conversion circuit. The preset strategy includes: outputting a second control signal to the switching unit, and when it is determined that the DC bus voltage reaches a first threshold, outputting a pulse-type first control signal to the switching unit according to a preset duty cycle; and when it is determined that the DC bus voltage reaches a second threshold, repeating the above steps until the temperature of the insulating coolant reaches a second temperature value. Wherein, the second control signal is used to control the switch unit to turn off, the first control signal is used to control the switch unit to close, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

3. The fully immersion power module according to claim 1, characterized in that, The PCBA assembly also includes an AC / DC conversion circuit, which is connected to the heating unit. The switching unit is disposed in the AC / DC conversion circuit and is used to control the DC bus voltage of the AC / DC conversion circuit. The preset strategy includes: outputting a second control signal to the switching unit, and when it is determined that the DC bus voltage reaches a first threshold, outputting a pulse-type first control signal to the switching unit according to a target duty cycle; and when it is determined that the DC bus voltage reaches a second threshold, repeating the above steps until the temperature of the insulating coolant reaches a second temperature value. The target duty cycle is dynamically adjusted based on the set voltage and the DC bus voltage. The second control signal is used to control the switching unit to turn off, the first control signal is used to control the switching unit to close, the second threshold is less than the first threshold, and the second temperature value is greater than the first temperature value.

4. The fully immersion power module according to claim 1, characterized in that, The AC power supply has three output terminals, and the heating unit has three heating sub-units. One end of each heating subunit is connected to the corresponding output terminal, and the other end of each heating subunit is connected to the AC / DC conversion circuit; Each heating subunit includes a heating device and a controllable switch. The heating device and the controllable switch are connected in parallel. The controllable switch is used to disconnect when the temperature of the insulating coolant is lower than a first temperature value, thereby connecting the branch where the heating device is located.

5. The fully immersion power module according to any one of claims 2 to 4, characterized in that, The AC / DC conversion circuit is a Vienna circuit; The heating unit includes a first switch, a second switch, and a third switch; The switching unit includes a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, and a ninth switch; The fourth and fifth switches are connected in reverse series and then connected between the first switch and the midpoint of the DC bus. The sixth and seventh switches are connected in reverse series and then connected between the second switch and the midpoint of the DC bus. The eighth and ninth switches are connected in reverse series and then connected between the third switch and the midpoint of the DC bus.

6. The fully immersion power module according to any one of claims 2 to 4, characterized in that, The heating unit includes a first switch, a second switch, and a third switch; The switching unit includes a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, and a ninth switch; The fourth and fifth switches are connected in series to both ends of the DC bus; the sixth and seventh switches are connected in series to both ends of the DC bus; and the eighth and ninth switches are connected in series to both ends of the DC bus. The other end of the first switch is connected between the fourth switch and the fifth switch, the other end of the second switch is connected between the sixth switch and the seventh switch, and the other end of the third switch is connected between the eighth switch and the ninth switch.

7. The fully immersion power module according to claim 1, characterized in that, The heating unit includes multiple heating sub-units, the switching unit includes at least one switching sub-unit, the heating sub-unit includes at least one heating device, and the switching sub-unit includes a switching tube; The heating devices are connected in series and / or in parallel. The first end of the switching transistor is connected to the corresponding heating subunit, the second end of the switching transistor is grounded, and the third end of the switching transistor is connected to the controller.

8. The fully immersion power module according to claim 7, characterized in that, The preset strategy includes: When the temperature of the insulating coolant is lower than the third temperature value, the first control signal is continuously output to the switching unit; When the temperature of the insulating coolant is greater than the third temperature value and less than the fourth temperature value, the first control signal is output to the switching unit according to the target duty cycle. The first control signal is used to control the closing of the switch unit, and the target duty cycle is dynamically adjusted based on the temperature of the insulating coolant and the fourth temperature value, wherein the first temperature value is greater than the third temperature value and less than the fourth temperature value.

9. A charging system, characterized in that, It includes at least two power modules, a controller, a power distribution device, and at least one charging interface as described in any one of claims 1 to 8; The power distribution device is connected to the controller, each of the power modules, and each of the charging interfaces respectively; The controller is connected to each of the power modules respectively; For any power module, the controller is used to receive the temperature of the insulating coolant output by the temperature detection device in the power module, and when the temperature of the insulating coolant is less than a first temperature value, it outputs a first control signal to the switching unit of the heating circuit in the power module according to a preset strategy. The switching unit is used to respond to the first control signal output by the controller and turn on the heating unit. The heating unit is used to heat the insulating coolant when the heating circuit is working.

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