Hybrid heat dissipation method for marine compact frequency inverters

Abstract

This invention relates to a hybrid heat dissipation method for marine compact frequency converters, pioneering a hybrid heat dissipation architecture of "bionic liquid cooling + TEC compensation." This deeply integrates efficient passive liquid cooling with rapid active cooling, meeting both normal heat dissipation requirements and withstanding short-term peak thermal shocks, solving the problem of insufficient efficiency of single heat dissipation methods in the compact space of ships. Based on an intermittent intelligent control strategy driven by operating conditions, TEC is activated only during high temperatures or rapid temperature rises, reducing the total system energy consumption by more than 62% compared to traditional continuous TEC solutions. The bionic microchannels, printed with metal 3D, reduce flow resistance by 40% and increase the heat transfer coefficient by 120%, while the integrated structure is resistant to ship vibration and salt spray corrosion. It features active anti-condensation functionality, completely eliminating the risk of condensation in high humidity environments through real-time dew point tracking and cold surface temperature control, ensuring electrical safety. This allows for a 30% increase in the power density of marine frequency converters, keeps the IGBT junction temperature consistently below 85°C, and extends equipment life by more than 2 times.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology for marine electric propulsion systems, and particularly to a hybrid heat dissipation method for marine compact frequency converters. Background Technology

[0002] As ship electric propulsion systems develop towards higher efficiency, compactness, and higher power, the power density of frequency converters, as core power units, is constantly increasing. However, limited space in ship cabins and harsh environments (high temperature, high humidity, and high salt spray) have made heat dissipation a major bottleneck in technological development. Statistics show that over 55% of frequency converter system failures in the industrial sector are directly related to poor heat dissipation, and the average lifespan of equipment is shortened by 42% under high-temperature conditions.

[0003] Existing marine frequency converters mainly use air cooling or ordinary water cooling for heat dissipation. Air cooling efficiency decreases exponentially with increasing power density; traditional water cooling systems are bulky, have high requirements for water quality, and are prone to leakage under ship vibration and impact. In recent years, thermoelectric coolers (TECs) have been attempted for heat dissipation in electronic devices due to their small size, lack of moving parts, and ability to actively cool. However, they only use a single TEC plus aluminum block structure and lack operating condition identification and intelligent control capabilities. In high-power marine frequency converters, they have the following shortcomings: (1) TECs consume extremely high energy during continuous operation and cannot adapt to dynamic heat loads; (2) They lack anti-condensation design, and condensation on the cold surface in high humidity environments can lead to short circuits; (3) They rely solely on natural convection for heat dissipation, which cannot meet the peak heat flux density requirements. Therefore, there is an urgent need for a small, stable, fast cooling capacity, and low energy consumption hybrid heat dissipation method. Summary of the Invention

[0004] To address the issues that existing marine frequency converter heat dissipation technologies cannot simultaneously achieve efficient heat dissipation under normal conditions and peak thermal shock, and also suffer from high energy consumption and condensation risks, a hybrid heat dissipation method for marine compact frequency converters is proposed.

[0005] The technical solution of this invention is: a hybrid heat dissipation method for a marine compact frequency converter, comprising the following steps: Step S1: Construct a hybrid heat dissipation system: integrate a biomimetic liquid cooling circuit and a semiconductor refrigeration TEC compensation unit. The TEC compensation unit is arranged between the biomimetic liquid cooling circuit and the inverter power semiconductor device, with its cooling surface facing the power semiconductor device and its heating surface facing the biomimetic liquid cooling circuit. Step S2: Real-time acquisition of operating data: Acquire the real-time temperature of the power semiconductor device. Load current, cooling water inlet temperature and outlet temperature; Step S3, Intelligent heat dissipation mode identification: Based on the real-time temperature and its temperature change rate Determine the current operating condition; when Less than the first temperature threshold and Less than the temperature rise rate threshold When the condition is determined to be low load, only the biomimetic liquid cooling circuit is activated; when or When the condition is determined to be a high-load condition, the TEC compensation unit is activated to provide auxiliary cooling. Step S4, Anti-condensation linkage control: Real-time acquisition of ambient dew point temperature And monitor the temperature of the TEC cooling surface. Control the satisfy ,in To prevent condensation, a safety margin is required; When detected And the If the temperature remains above the target control temperature, an anti-condensation priority degradation strategy is implemented, stopping any increase or decrease in the cooling power of the TEC compensation unit and triggering at least one of the following degradation actions: (1) Increase the coolant circulation pump speed of the biomimetic liquid cooling circuit; (2) Allow the real-time temperature of the power semiconductor device The temperature rises below the preset safe upper limit. (3) Send a frequency reduction request to the inverter main control system to reduce the heat generation of the power semiconductor device.

[0006] Furthermore, in step S4, the anti-condensation linkage control also includes: After triggering the aforementioned linkage degradation strategy, continuously monitor the... ; to be described Restored to above Afterwards, the degradation action is lifted, and the operating current of the TEC compensation unit is reassessed and adjusted.

[0007] Furthermore, step S5, precise temperature control of local hot spots, is included after step S3: The TEC compensation unit is composed of multiple micro TEC units arranged in a grid-like array; multiple regional temperature sensors are arranged on the surface of the power semiconductor device; the controller independently adjusts the operating current of each micro TEC unit in the array to selectively compensate for local areas where the temperature exceeds the limit.

[0008] Furthermore, the hybrid heat dissipation method for marine compact frequency converters also includes step S6, returning to high-efficiency heat dissipation: When the real-time temperature of the power semiconductor device Drop to the second temperature threshold After the duration reaches the preset time, the TEC compensation unit is turned off, and the system switches to a mode that only enables the biomimetic liquid cooling circuit.

[0009] Furthermore, the microchannels of the biomimetic liquid cooling circuit in step S1 adopt a three-level fractal leaf vein structure integrally formed by metal 3D printing; the three-level fractal leaf vein structure includes a primary trunk channel, a secondary branch channel, and a tertiary branch channel, wherein the width of the primary trunk channel is 1.5mm to 2.5mm, the width of the secondary branch channel is 0.8mm to 1.2mm, the width of the tertiary branch channel is 0.4mm to 0.6mm, and the depth of all channels is uniformly 1.0mm to 1.5mm.

[0010] A hybrid heat dissipation system for a marine compact frequency converter, used to implement the aforementioned hybrid heat dissipation method, includes: The biomimetic liquid cooling circuit includes a microchannel heat sink integrally formed by metal 3D printing, wherein the heat sink is mounted in close contact with the power semiconductor device of the frequency converter; The TEC compensation unit includes multiple miniature semiconductor cooling chips, which are embedded and fixedly mounted in a grid pattern on the microchannel heat sink. Its cooling surface is in contact with the power semiconductor device through a thermally conductive medium, and its heating surface is in contact with the microchannel heat sink. The sensor group includes a temperature sensor for acquiring the temperature of the power semiconductor device, a current transformer for acquiring the load current, a water temperature sensor for acquiring the cooling water temperature, and a temperature and humidity sensor for acquiring the ambient temperature and humidity. The controller is electrically connected to the circulating pump of the biomimetic liquid cooling circuit, the TEC compensation unit, and the sensor group, respectively; the controller is configured to execute the heat dissipation mode recognition, on-demand start-up, and anti-condensation linkage degradation control logic as described in any one of claims 1-5.

[0011] Preferably, the microchannel heat sink is made of 316L stainless steel, copper alloy, or titanium alloy; when the application environment is a high salt spray corrosion scenario, the surface of the microchannel heat sink is coated with a parylene anti-corrosion coating with a thickness of 20μm to 30μm.

[0012] Preferably, the TEC compensation unit includes 6 to 12 miniature TEC units, each of which is independently connected to the PWM drive circuit of the controller. The controller achieves independent closed-loop control of the operating current of each miniature TEC unit by adjusting the PWM duty cycle.

[0013] Preferably, the marine compact inverter hybrid heat dissipation system further includes a double-sided cooling extension structure: two sets of the biomimetic liquid cooling circuits and the TEC compensation unit are symmetrically arranged on both sides of the power semiconductor device to form a sandwich-type double-sided heat dissipation structure.

[0014] Preferably, the controller also integrates a fault self-diagnosis module. When the temperature of the power semiconductor device exceeds a preset limit safety threshold, or the temperature change rate is greater than a preset sudden change threshold, the controller issues an over-temperature warning signal and forcibly outputs a frequency reduction command to the inverter main control system.

[0015] The beneficial effects of this invention are as follows: This invention provides a hybrid heat dissipation method for marine compact frequency converters. 1) The first-ever hybrid heat dissipation architecture of "bionic liquid cooling + TEC compensation" deeply integrates efficient passive liquid cooling and rapid active cooling, which can not only meet the normal heat dissipation needs, but also withstand short-term peak thermal shock, solving the problem of insufficient efficiency of a single heat dissipation method in the compact space of a ship. 2) Based on the intermittent intelligent control strategy of working condition perception, TEC is activated only when the temperature is high or the temperature rises rapidly, and the total energy consumption of the system is reduced by more than 62% compared with the traditional continuous TEC solution; 3) The biomimetic microchannels, made of metal 3D printing, reduce flow resistance by 40% and increase heat transfer coefficient by 120%. At the same time, the integrated structure is resistant to ship vibration and salt spray corrosion. 4) It has an active anti-condensation function, which completely eliminates the risk of condensation in high humidity environments and ensures electrical safety through real-time dew point tracking and cold surface temperature control; 5) Enables a 30% increase in power density for marine frequency converters, while maintaining IGBT junction temperature consistently within a specified range. Below 85℃ The equipment lifespan is extended by more than 2 times. Attached Figure Description

[0016] Figure 1 This is an overall flowchart of the hybrid heat dissipation method for marine compact frequency converters of the present invention; Figure 2 This is a schematic diagram of the hybrid heat dissipation system structure in the method of the present invention; Figure 3 This is a state transition diagram of the intelligent control strategy in the method of the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0018] like Figure 1 The overall flowchart of the hybrid heat dissipation method for marine compact frequency converters shown includes the following steps: Step 1: Construct a hybrid heat dissipation system: Integrate a biomimetic liquid cooling circuit and a thermoelectric cooler (TEC) compensation unit; the biomimetic liquid cooling circuit uses an integrated leaf-vein-shaped microchannel heat sink printed by metal 3D printing, installed close to the inverter's power semiconductor device (IGBT); the TEC compensation unit is arranged between the biomimetic liquid cooling circuit and the power device, with its cooling surface facing the power device and its heating surface facing the biomimetic liquid cooling circuit; for example... Figure 2 The schematic diagram of the hybrid heat dissipation system shows a biomimetic microchannel water-cooled plate 3 with inlet and outlet ports 4. A semiconductor cooling chip 2 is embedded and fixedly mounted on the biomimetic microchannel water-cooled plate 3, and an IGBT power module 1 is mounted on the semiconductor cooling chip 2. The TEC compensation unit consists of 6 to 12 miniature TEC arrays arranged in a grid pattern below the IGBT substrate.

[0019] Steps 2 to 8 below constitute a real-time control loop with a sampling frequency of 10Hz. The controller executes the operating condition identification and mode switching logic once every 100ms.

[0020] Step 2: Real-time acquisition of operating data: When the frequency converter is working, the temperature of the power semiconductor device is collected in real time through temperature sensors embedded on the power semiconductor device substrate, frequency converter output current transformer, and cooling water flow meter. Load current Cooling water inlet temperature and outlet temperature .

[0021] Step 3: Intelligent heat dissipation mode identification: Input the collected data into the embedded controller and calculate the temperature change rate. and heat load rating; when and When, it is judged to be a low-load operating condition; when or At that time, it was determined to be a high-load operating condition; among which The value range is 75℃~85℃ (IGBT derating temperature setting value). The value range is 2℃ / s to 4℃ / s (dynamic temperature rise setting). This manual sets the high-load temperature. 85℃, low load temperature The target temperature is 65℃. The safety margin for preventing condensation is 75℃. The value is 2℃. The specific value is determined by derating by 80% based on the maximum allowable junction temperature (usually 150℃~175℃) in the power device datasheet. It is also adjusted in conjunction with the thermal resistance of the biomimetic liquid cooling circuit (measured 0.05~0.10 K / W) and the inlet temperature of the ship's cooling water (0℃~40℃). For example, for the IGBT module FF450R12ME4, the derating temperature is 85℃ and the temperature rise rate threshold is 3℃ / s; for SiC MOSFET (higher temperature resistance), the threshold can be increased to 95℃ and 4℃ / s respectively.

[0022] Step 4: Activate TEC compensation as needed: Under low load conditions, only the bionic liquid cooling circuit is activated, and the TEC remains off; under high load conditions, the controller outputs a PWM signal to drive the TEC to start, and adjusts the compensation based on the real-time temperature of the power devices. With target temperature (The difference adjusts the TEC operating current) proportionality coefficient The settings were adjusted through experiments.

[0023] Step 5, Precise temperature control of local hot spots: Multiple miniature TEC arrays are arranged on the surface of the power device, and each unit in the array corresponds to a regional temperature sensor; the controller independently adjusts the current of each unit in the array to selectively compensate for the temperature exceeding the standard and eliminate local hot spots.

[0024] Step 6, Anti-condensation control: Real-time monitoring of ambient dew point temperature (Calculated by temperature and humidity sensors), and ensures the temperature of the TEC cooling surface. ,in To prevent condensation, a safety margin should be maintained; when As the temperature approaches the dew point, the controller reduces the TEC current or forces the system into intermittent operation to prevent condensation. The controller detects the temperature of the TEC cooling surface. And the temperature of power devices Still above the high load temperature At this time, the anti-condensation logic takes precedence over the maximum cooling demand: the controller will not continue to increase the TEC current, but will instead execute one or a combination of the following degradation strategies: 1. Increase the pump speed of the biomimetic liquid cooling circuit to the maximum (e.g., increase it by 30% from the rated flow rate) to force an increase in convective heat transfer; 2. The junction temperature of power devices is temporarily allowed to rise below the safe upper limit (e.g., 105°C), but not to the absolute maximum value in the datasheet; 3. If If the temperature exceeds the second safety threshold (105℃), a frequency reduction request is sent to the inverter master controller to actively reduce the heat generation. 4. Pending After restoring the current to above the dew point plus the anti-condensation safety margin, reassess the TEC operating current.

[0025] Step 7, Return to Efficient Heat Dissipation: When the temperature of power devices... Reduced to low load temperature After 30 seconds, the controller shuts off TEC and switches to biomimetic liquid cooling mode only to reduce system energy consumption.

[0026] like Figure 3 The intelligent control strategy state transition diagram shown automatically switches between low-load liquid cooling mode, high-load TEC auxiliary mode, and anti-condensation intermittent mode to ensure that the frequency converter operates in the optimal state.

[0027] The microchannels of the biomimetic liquid cooling circuit described in step 1 adopt a three-level fractal leaf vein structure: the primary main channel is 2.0 mm wide, the secondary branch is 1.0 mm wide, and the tertiary branch is 0.5 mm wide. All channels have a uniform depth of 1.2 mm, and the hydraulic diameter is approximately 0.8 mm (calculated using the rectangular channel formula). Compared to traditional parallel straight channels, this structure reduces pressure drop by 40% (simulation value: original 5.2 kPa → now 3.1 kPa) at the same flow rate (5 L / min), increases the Nusselt number by 120%, and achieves a heat transfer coefficient of 8500 W / (m²·K). The flow channel is integrally molded using 316L stainless steel 3D printing, with no welding seams, increasing the natural frequency to over 200 Hz (traditional welded types are only 80 Hz), and improving resistance to ship vibration acceleration (±5g, 5~200 Hz sweep frequency) by 3 times, with no risk of leakage. Copper alloys or titanium alloys can also be used to adapt to different corrosive environments.

[0028] In step 2, the temperature sensor is a PT1000 thin-film platinum resistance thermometer, which is mounted directly below the IGBT chip; the current transformer has an accuracy of 0.5 class; and the sampling frequency is 10Hz.

[0029] In step 4, the PWM drive frequency is 1kHz, the TEC operating current range is 0~5A, and the maximum cooling power is 60W.

[0030] In step 5, there are 6 to 12 miniature TEC units, arranged in a grid pattern. Each unit has a rated voltage of 5V and a maximum current of 2A.

[0031] In step 6, a thin thermocouple or NTC thermistor is attached to the TEC cooling surface to directly measure the cold surface temperature. Meanwhile, ambient temperature is obtained by temperature and humidity sensors placed near the TEC at a point of stable airflow. The dew point temperature is calculated using formula (1) based on the relative humidity (RH). : , Where a=17,27, b=237.7℃ (applicable to the range of 0~50℃).

[0032] controller with For the goal ( The PID algorithm is used to adjust the PWM duty cycle of the TEC in real time, so that... Track this target value. The PID output is directly limited to control the TEC operating current. ( Forming closed-loop coupled control: when When the value is below the target value, reduce Or enter intermittent work mode; when When the value is higher than the target value, an increase is allowed. However, it is necessary to monitor whether the temperature of the power devices exceeds the limit at the same time.

[0033] Priority arbitration: if Excessive heat requires full-power TEC cooling, while If the value is already below the target value, the anti-condensation logic takes precedence over the maximum cooling demand, and the controller will not increase its output. Instead, a degradation strategy is implemented (such as increasing the speed of the bionic liquid cooling pump or sending a frequency reduction request to the inverter), pending... Restore TEC adjustment only after the value has been restored above the target value.

[0034] Verification data: In a constant temperature and humidity chamber with an ambient temperature of 45℃ and a relative humidity of 85%, after continuous operation for 24 hours using the method described in this step, the TEC cold surface temperature... Always stable at Within the specified range, the cold surface and surrounding circuit boards were inspected using a high-powered microscope, and no condensation droplets were found, verifying the reliability of the anti-condensation control.

[0035] The method also includes step 8, fault self-diagnosis: when the temperature of the power device exceeds 105℃ or the temperature change rate is greater than 10℃ / s, the controller issues an over-temperature warning signal and forcibly reduces the output frequency of the inverter.

[0036] The method of this invention was implemented on a certain type of 500kW marine propulsion frequency converter. The frequency converter contains 6 IGBT modules (model Infineon FF450R12ME4), with a total heat dissipation power of approximately 1.2kW. The ambient temperature in the ship's cabin was 45℃, the humidity was 85%, and the cooling water source was seawater (temperature 32℃).

[0037] Step 1: Construct a hybrid cooling system: An integrated biomimetic water-cooled plate, made of 316L stainless steel, was manufactured using metal 3D printing (EOS M290 equipment). The microchannels employ a three-stage fractal leaf vein structure: the first stage is 2mm wide, the second stage is 1mm wide, and the third stage is 0.5mm wide, with a depth of 1.2mm and a total flow channel length of 280mm. The water-cooled plate's inlet / outlet uses G1 / 4 threaded interfaces. Twelve miniature TECs (model TEC1-12703, size 20×20×3.8mm) are arranged in a 4×3 grid between the water-cooled plate and the IGBTs. The cooling surface of the TECs is coated with thermal grease (thermal conductivity 3.5W / m·K), and the space between the heating surface and the water-cooled plate is filled with indium foil. The controller uses an STM32F407 with a built-in PID algorithm, and the output PWM drives the TECs via MOSFETs.

[0038] Step 2: Real-time acquisition of operating condition data: A PT1000 thin-film resistor (accuracy ±0.1℃) is mounted at the center of each IGBT substrate and connected to the AD7124 acquisition module via a three-wire connection. A LEM IT400 current sensor is used to measure the inverter's output current. A turbine flow meter (range 2~20L / min) and a PT1000 temperature sensor are installed in the water-cooling circuit. All sensors transmit data to the controller at a frequency of 10Hz.

[0039] Steps 3-7: Intelligent Control and Testing Setting parameters: , , , The dew point margin is 2℃. Steady-state low load (30% of rated load) and dynamic load (30%→100%→30% step) experiments were conducted, and compared with pure biomimetic liquid cooling and traditional air cooling.

[0040] Experimental results: Steady-state 30% load: Pure liquid cooling can stabilize the maximum temperature of IGBT at 62℃; the method of this invention does not start the TEC, the temperature is 61.5℃, and the energy consumption is the same as that of pure liquid cooling.

[0041] 100% load step: Under pure liquid cooling conditions, the IGBT temperature rises from 62°C to 98°C within 90 seconds (exceeding the 85°C warning threshold); the method of this invention achieves this when the temperature rises to 80°C ( ) TEC was activated, and the final temperature stabilized at 79℃, never exceeding 85℃ throughout the process.

[0042] Anti-condensation test: At 85% humidity and 45°C ambient temperature, the dew point is approximately 42.3°C. The controller maintains the TEC cold surface temperature at 44.5°C for 24 hours without condensation.

[0043] Energy consumption comparison: For a single 100% load operation lasting 10 minutes, the pure TEC solution (continuous operation) consumes 36kJ of energy. The method of this invention operates for a cumulative total of 180 seconds with TEC, consuming only 13.5kJ of energy, a reduction of 62.5%.

[0044] Additional modifications to the specific implementation plan: For applications with severe salt spray corrosion, biomimetic microchannels can be 3D printed using titanium alloys, with a 25μm thick parylene (Parylene C) coating on the surface.

[0045] For inverters with higher power density, a double-sided cooling structure can be added in step 1: a set of biomimetic water-cooled plates and TECs are arranged on both sides of the IGBT to form a sandwich-type heat dissipation.

[0046] Using the above methods, marine compact frequency converters can intelligently switch heat dissipation strategies according to real-time operating conditions, significantly reducing the long-term energy consumption of TEC while ensuring that the temperature of power devices is controllable, avoiding the risk of condensation, and improving system reliability and power density.

[0047] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A hybrid heat dissipation method for a marine compact frequency converter, characterized in that, Includes the following steps: Step S1: Construct a hybrid heat dissipation system: Integrate a biomimetic liquid cooling circuit and a semiconductor refrigeration TEC compensation unit. The TEC compensation unit is arranged between the biomimetic liquid cooling circuit and the inverter power semiconductor device, with its cooling surface facing the power semiconductor device and its heating surface facing the biomimetic liquid cooling circuit. Step S2: Real-time acquisition of operating data: Acquire the real-time temperature of the power semiconductor device.

1. Load current, cooling water inlet temperature and outlet temperature; Step S3, Intelligent identification of heat dissipation mode: based on the real-time temperature and its temperature change rate Determine the current operating condition; when Less than the first temperature threshold and Less than the temperature rise rate threshold When the condition is determined to be low load, only the biomimetic liquid cooling circuit is activated; when or When the condition is determined to be high load, the TEC compensation unit is activated for auxiliary cooling; Step S4, anti-condensation linkage control: real-time acquisition of ambient dew point temperature. And monitor the temperature of the TEC cooling surface. Control the satisfy ,in To prevent condensation, a safety margin should be maintained; when condensation is detected... And the If the temperature remains above the target control temperature, an anti-condensation priority linkage degradation strategy is implemented, stopping the increase or decrease of the cooling power of the TEC compensation unit, and triggering at least one of the following degradation actions: (1) increasing the coolant circulation pump speed of the biomimetic liquid cooling circuit; (2) allowing the real-time temperature of the power semiconductor device to remain above the target control temperature. The temperature rises below the preset safe upper limit. (3) Send a frequency reduction request to the inverter main control system to reduce the heat generation of the power semiconductor device.

2. The hybrid heat dissipation method for marine compact frequency converters according to claim 1, characterized in that, In step S4, the anti-condensation linkage control further includes: after triggering the linkage degradation strategy, continuously monitoring the... ; to be described Restored to above Afterwards, the degradation action is lifted, and the operating current of the TEC compensation unit is reassessed and adjusted.

3. The hybrid heat dissipation method for marine compact frequency converters according to claim 1, characterized in that, Step S3 is followed by step S5, precise temperature control of local hot spots: the TEC compensation unit is composed of multiple micro TEC units arranged in a grid array; multiple area temperature sensors are arranged on the surface of the power semiconductor device; the controller independently adjusts the operating current of each micro TEC unit in the array to selectively compensate for local areas with excessive temperature.

4. The hybrid heat dissipation method for marine compact frequency converters according to claim 1, characterized in that, It also includes step S6, returning to efficient heat dissipation: when the real-time temperature of the power semiconductor device... Drop to the second temperature threshold After the duration reaches the preset time, the TEC compensation unit is turned off, and the system switches to a mode that only enables the biomimetic liquid cooling circuit.

5. The hybrid heat dissipation method for marine compact frequency converters according to claim 1, characterized in that, The microchannels of the biomimetic liquid cooling circuit in step S1 adopt a three-level fractal leaf vein structure integrally formed by metal 3D printing; the three-level fractal leaf vein structure includes a primary trunk channel, a secondary branch channel and a tertiary branch channel, wherein the width of the primary trunk channel is 1.5mm to 2.5mm, the width of the secondary branch channel is 0.8mm to 1.2mm, the width of the tertiary branch channel is 0.4mm to 0.6mm, and the depth of all channels is uniformly 1.0mm to 1.5mm.

6. A hybrid heat dissipation system for a marine compact frequency converter, used to implement the hybrid heat dissipation method as described in any one of claims 1-5, characterized in that, include: The biomimetic liquid cooling circuit includes a microchannel heat sink integrally formed by metal 3D printing, wherein the heat sink is mounted in close contact with the power semiconductor device of the frequency converter; The TEC compensation unit includes multiple miniature semiconductor cooling chips embedded and fixedly mounted in a grid pattern on the microchannel heat sink. Its cooling surface contacts the power semiconductor device via a thermally conductive medium, and its heating surface contacts the microchannel heat sink. A sensor group includes a temperature sensor for acquiring the temperature of the power semiconductor device, a current transformer for acquiring the load current, a water temperature sensor for acquiring the cooling water temperature, and a temperature and humidity sensor for acquiring the ambient temperature and humidity. A controller is electrically connected to the circulation pump of the biomimetic liquid cooling circuit, the TEC compensation unit, and the sensor group. The controller is configured to execute the heat dissipation mode recognition, on-demand start-up, and anti-condensation linkage degradation control logic as described in any one of claims 1-5.

7. The marine compact frequency converter hybrid heat dissipation system according to claim 6, characterized in that, The microchannel heat sink is made of 316L stainless steel, copper alloy or titanium alloy; when the application environment is a high salt spray corrosion scenario, the surface of the microchannel heat sink is coated with a parylene anti-corrosion coating with a thickness of 20μm to 30μm.

8. The marine compact frequency converter hybrid heat dissipation system according to claim 6, characterized in that, The TEC compensation unit contains 6 to 12 miniature TEC units, each of which is independently connected to the PWM drive circuit of the controller. The controller achieves independent closed-loop control of the operating current of each miniature TEC unit by adjusting the PWM duty cycle.

9. The marine compact frequency converter hybrid heat dissipation system according to claim 6, characterized in that, It also includes a double-sided cooling extension structure: two sets of the biomimetic liquid cooling circuits and the TEC compensation unit are symmetrically arranged on both sides of the power semiconductor device to form a sandwich-type double-sided heat dissipation structure.

10. The marine compact frequency converter hybrid heat dissipation system according to claim 6, characterized in that: The controller also integrates a fault self-diagnosis module. When the temperature of the power semiconductor device exceeds the preset limit safety threshold, or the temperature change rate is greater than the preset sudden change threshold, the controller issues an over-temperature warning signal and forcibly outputs a frequency reduction command to the inverter main control system.

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