Composite radiator, power semiconductor device radiating system and converter valve assembly

Abstract

The invention provides a composite radiator, a power semiconductor device heat dissipation system and a converter valve assembly, and belongs to the technical field of semiconductor device heat dissipation. The combined type radiator comprises a substrate, a cooling liquid flow channel is arranged in the substrate, and a phase change working medium flow channel is arranged on the surface layer of the substrate. The boiling point of the phase change working medium is larger than the temperature of the surface layer of the substrate of the power semiconductor device under the steady-state working condition and smaller than the temperature of the surface layer of the substrate of the power semiconductor device under the transient-state working condition, and in the steady-state working condition, the inner-layer cooling liquid works independently to maintain the normal temperature of the device; and in a transient working condition, the surface phase change cooling layer is immediately started and cooperatively works with the inner cooling liquid, so that the sudden rise of the junction temperature of the device in the transient working condition is effectively inhibited. The two layers of cooling media are mutually independent and mutually matched, hierarchical control of junction temperature of the device is achieved, and a good heat dissipation effect can be provided for the power semiconductor device under the steady state working condition and the transient state working condition.

Description

Technical Field

[0001] This invention relates to a composite heat sink, a power semiconductor device heat dissipation system, and a converter valve assembly, belonging to the field of semiconductor device heat dissipation technology. Background Technology

[0002] Converter valves are critical equipment in high-voltage direct current (HVDC) transmission systems, and their reliability directly affects the stable operation of the power grid. Power semiconductor devices (such as IGBTs and thyristors) are the core components of converter valves. The heat generated during their operation must be quickly dissipated through efficient heat dissipation devices to ensure device capacity and lifespan. With the increase in device power density, heat dissipation problems under steady-state conditions can be solved by pure water forced convection technology. However, under transient conditions (such as valve group start-up and shutdown, fault overcurrent, lightning impulse, etc.), the instantaneous power loss of the devices surges, causing the junction temperature to rise sharply in a short period of time. If the junction temperature exceeds the safety threshold, it will cause thermal failure of the devices, seriously threatening the stability of the system.

[0003] Traditional single-layer plate heat sinks rely on forced convection of pure water for heat exchange. For example, Chinese invention patent application CN104992935A discloses a water-cooled heat sink for power electronic components. While water-cooled heat sinks can meet steady-state heat dissipation requirements, they have significant drawbacks in transient conditions. First, the thermal resistance response is lag-dependent. The heat transfer coefficient of pure water convection is limited by the flow velocity (typically 2-3 m / s), and under transient conditions, the heat exchange efficiency cannot be rapidly improved, resulting in a slow decrease in thermal resistance and insufficient control of the junction temperature peak. Second, the cooling mode is singular, sharing the same cooling mechanism for both steady-state and transient conditions. No dedicated heat dissipation structure is designed for the high heat flux density characteristics of transient conditions, requiring an increased cooling configuration to adapt to the heat dissipation requirements of transient conditions. This increases heat dissipation costs, and the cooling system operates at high configuration for extended periods, resulting in low energy matching efficiency.

[0004] Another Chinese utility model patent with authorization announcement number CN201417762Y discloses a heat dissipation device for high-power semiconductor devices. This heat dissipation device relies solely on phase change cooling medium to dissipate heat from the power semiconductor device. This heat dissipation method has certain limitations. Because the junction temperature of the power semiconductor device rises suddenly under transient operating conditions, if the heat carried away by the phase change cooling medium in the flow channel during vaporization is insufficient to absorb all the high temperature generated by the power semiconductor device, then the phase change cooling medium can only absorb heat again through phase change after liquefying in the external heat exchanger and returning to the heat sink. Therefore, the efficiency of phase change will affect the heat dissipation effect, resulting in the power semiconductor device not being able to dissipate heat quickly, and there is still a risk of thermal failure. Summary of the Invention

[0005] The purpose of this invention is to provide a composite heat sink to solve the problems of low heat exchange efficiency and insufficient control of junction temperature peak of power semiconductor devices under transient conditions caused by relying solely on pure water forced convection heat transfer in the prior art, or the problem of low energy matching efficiency caused by using high cooling configuration to adapt to heat dissipation requirements under transient conditions, as well as the problem that power semiconductor devices are still at risk of thermal failure due to the limitation of phase change efficiency when relying solely on phase change cooling medium for heat dissipation in the prior art; the purpose of this invention is also to provide a heat dissipation system for power semiconductor devices and a converter valve assembly to solve the above problems.

[0006] To achieve the above objectives, the composite radiator of this invention adopts the following technical solution: A composite heat sink includes a substrate with coolant channels inside for forced convection heat transfer; a phase change working fluid channel on the surface of the substrate for latent heat transfer; the boiling point of the phase change working fluid is higher than the temperature of the substrate surface under steady-state conditions of the power semiconductor device, but lower than the temperature of the substrate surface under transient conditions of the power semiconductor device, so that the coolant alone dissipates heat from the power semiconductor device under steady-state conditions, and the coolant and phase change working fluid work together to dissipate heat from the power semiconductor device under transient conditions.

[0007] The beneficial effects of the above technical solution are as follows: This invention is a pioneering invention, proposing a composite heat sink, which includes a substrate, a coolant flow channel inside the substrate for the coolant to exchange heat through forced convection; and a phase change working medium flow channel on the surface of the substrate for the phase change working medium to exchange heat through the latent heat of phase change. In this way, the heat sink integrates two cooling media with different heat exchange principles.

[0008] The boiling point of the phase change working fluid is higher than the temperature of the substrate surface under steady-state conditions of the power semiconductor device, but lower than the temperature of the substrate surface under transient conditions of the power semiconductor device. Thus, under steady-state conditions, the phase change working fluid does not play a role, and the coolant works alone to dissipate heat from the power semiconductor device, meeting the heat dissipation requirements of the power semiconductor device during steady-state operation and maintaining the normal temperature of the power semiconductor device.

[0009] When transient conditions occur, the heat generated by power semiconductor devices rises sharply. The phase change medium on the surface absorbs a large amount of heat and rapidly undergoes a phase change, transforming from a liquid to a gaseous state. Utilizing the latent heat of the phase change, it efficiently absorbs and removes heat, effectively suppressing the sudden rise in junction temperature and overcoming the problem of hysteresis in the thermal resistance response of traditional heat sinks. Simultaneously, the internal coolant also exchanges heat through forced convection, removing the remaining heat that the phase change medium did not absorb during the phase change. In other words, the coolant and phase change medium work together to achieve graded control of the device junction temperature, effectively suppressing the sudden rise in junction temperature under transient conditions and significantly improving heat dissipation efficiency and system reliability.

[0010] The phase change working fluid and coolant are both independent and complementary, enabling graded control of the junction temperature of the device. They can provide good heat dissipation for power semiconductor devices under both steady-state and transient conditions. Therefore, the coolant circulation system does not require an increase in cooling configuration, which improves energy matching efficiency and reduces operating costs.

[0011] Furthermore, a groove is formed on the contact surface of the substrate for contacting the power semiconductor device. A working fluid channel for accommodating the phase change working fluid is embedded and fixed in the groove. The inner cavity of the working fluid channel forms a phase change working fluid flow channel. One side of the channel wall is flush with the contact surface of the substrate.

[0012] Furthermore, the groove has a U-shaped cross-section, and the working fluid pipe is a flat pipe.

[0013] Furthermore, the substrate includes two opposing and parallel contact surfaces, each with a groove, and a working fluid pipe is embedded and fixed in each groove, with the coolant flow channel located between the working fluid pipes on both sides.

[0014] Furthermore, the phase change working fluid channel is processed inside the substrate near the surface layer, and one side of the channel wall of the phase change working fluid channel is part of the substrate surface layer.

[0015] Furthermore, the phase change working fluid channel includes a horizontal section and inclined sections connected to both ends of the horizontal section and extending upwards at an angle.

[0016] Furthermore, on the same side of the substrate, two or more phase change working fluid channels are arranged at intervals along the vertical direction, and each phase change working fluid channel is connected to a manifold at both ends, with the manifold at both ends having an interface for connecting to the condenser.

[0017] To achieve the above objectives, the power semiconductor device heat dissipation system of the present invention adopts the following technical solution: A heat dissipation system for a power semiconductor device includes a heat sink for being attached to the power semiconductor device. The heat sink includes a substrate with a coolant flow channel inside for forced convection heat transfer of the coolant. A phase change working fluid flow channel is provided on the surface of the substrate for latent heat transfer of the phase change working fluid. The boiling point of the phase change working fluid is higher than the temperature of the substrate surface under steady-state conditions and lower than the temperature of the substrate surface under transient conditions, so that the coolant alone dissipates heat from the power semiconductor device under steady-state conditions, and the coolant and phase change working fluid work together to dissipate heat from the power semiconductor device under transient conditions. The heat dissipation system also includes a condenser connected to the phase change working fluid flow channel in the heat sink for the phase change working fluid to change from a gaseous state to a liquid state and flow back to the phase change working fluid flow channel.

[0018] The beneficial effects of the above technical solution are as follows: This invention is an improved invention. The improvement is that the heat sink includes a substrate, and a coolant flow channel is provided inside the substrate so that the coolant can exchange heat through forced convection; a phase change working medium flow channel is provided on the surface of the substrate so that the phase change working medium can exchange heat through the latent heat of phase change. In this way, the heat sink integrates two cooling media with different heat exchange principles.

[0019] The boiling point of the phase change working fluid is higher than the temperature of the substrate surface under steady-state conditions of the power semiconductor device, but lower than the temperature of the substrate surface under transient conditions of the power semiconductor device. Thus, under steady-state conditions, the phase change working fluid does not play a role, and the coolant works alone to dissipate heat from the power semiconductor device, meeting the heat dissipation requirements of the power semiconductor device during steady-state operation and maintaining the normal temperature of the power semiconductor device.

[0020] When transient conditions occur, the heat generated by power semiconductor devices rises sharply. The phase change medium on the surface absorbs a large amount of heat and rapidly undergoes a phase change, transforming from a liquid to a gaseous state. Utilizing the latent heat of the phase change, it efficiently absorbs and removes heat, effectively suppressing the sudden rise in junction temperature and overcoming the problem of hysteresis in the thermal resistance response of traditional heat sinks. Simultaneously, the internal coolant also exchanges heat through forced convection, removing the remaining heat that the phase change medium did not absorb during the phase change. In other words, the coolant and phase change medium work together to achieve graded control of the device junction temperature, effectively suppressing the sudden rise in junction temperature under transient conditions and significantly improving heat dissipation efficiency and system reliability.

[0021] The phase change working fluid and coolant are both independent and complementary, enabling graded control of the junction temperature of the device. They can provide good heat dissipation for power semiconductor devices under both steady-state and transient conditions. Therefore, the coolant circulation system does not require an increase in cooling configuration, which improves energy matching efficiency and reduces operating costs.

[0022] Furthermore, a groove is formed on the contact surface of the substrate for contacting the power semiconductor device. A working fluid channel for accommodating the phase change working fluid is embedded and fixed in the groove. The inner cavity of the working fluid channel forms a phase change working fluid flow channel. One side of the channel wall is flush with the contact surface of the substrate.

[0023] Furthermore, the groove has a U-shaped cross-section, and the working fluid pipe is a flat pipe.

[0024] Furthermore, the substrate includes two opposing and parallel contact surfaces, each with a groove, and a working fluid pipe is embedded and fixed in each groove, with the coolant flow channel located between the working fluid pipes on both sides.

[0025] Furthermore, the phase change working fluid channel is processed inside the substrate near the surface layer, and one side of the channel wall of the phase change working fluid channel is part of the substrate surface layer.

[0026] Furthermore, the phase change working fluid channel includes a horizontal section and inclined sections connected to both ends of the horizontal section and extending upwards at an angle.

[0027] Furthermore, on the same side of the substrate, two or more phase change working fluid channels are arranged at intervals along the vertical direction, and each phase change working fluid channel is connected to a manifold at both ends, with the manifold at both ends having an interface for connecting to the condenser.

[0028] Furthermore, the condenser is located above the radiator so that the phase change working fluid, which has been converted into liquid, flows back into the phase change working fluid channel under the action of gravity.

[0029] To achieve the above objectives, the converter valve assembly of the present invention adopts the following technical solution: A converter valve assembly includes a power semiconductor device. The power semiconductor device is configured with a heat dissipation system. The heat dissipation system includes a heat sink for being attached to the power semiconductor device. The heat sink includes a substrate with a coolant flow channel inside for forced convection heat transfer of the coolant. A phase change working fluid flow channel is provided on the surface of the substrate for latent heat transfer of the phase change working fluid therein. The boiling point of the phase change working fluid is higher than the temperature of the substrate surface under steady-state operation of the power semiconductor device and lower than the temperature of the substrate surface under transient operation of the power semiconductor device. This allows the coolant to dissipate heat from the power semiconductor device alone under steady-state operation, and the coolant and the phase change working fluid to dissipate heat from the power semiconductor device in synergistic operation under transient operation. The heat dissipation system also includes a condenser connected to the phase change working fluid flow channel in the heat sink for the phase change working fluid to change from a gaseous state to a liquid state and flow back to the phase change working fluid flow channel.

[0030] The beneficial effects of the above technical solution are as follows: This invention is an improved invention. The improvement is that the heat sink includes a substrate, and a coolant flow channel is provided inside the substrate so that the coolant can exchange heat through forced convection; a phase change working medium flow channel is provided on the surface of the substrate so that the phase change working medium can exchange heat through the latent heat of phase change. In this way, the heat sink integrates two cooling media with different heat exchange principles.

[0031] The boiling point of the phase change working fluid is higher than the temperature of the substrate surface under steady-state conditions of the power semiconductor device, but lower than the temperature of the substrate surface under transient conditions of the power semiconductor device. Thus, under steady-state conditions, the phase change working fluid does not play a role, and the coolant works alone to dissipate heat from the power semiconductor device, meeting the heat dissipation requirements of the power semiconductor device during steady-state operation and maintaining the normal temperature of the power semiconductor device.

[0032] When transient conditions occur, the heat generated by power semiconductor devices rises sharply. The phase change medium on the surface absorbs a large amount of heat and rapidly undergoes a phase change, transforming from a liquid to a gaseous state. Utilizing the latent heat of the phase change, it efficiently absorbs and removes heat, effectively suppressing the sudden rise in junction temperature and overcoming the problem of hysteresis in the thermal resistance response of traditional heat sinks. Simultaneously, the internal coolant also exchanges heat through forced convection, removing the remaining heat that the phase change medium did not absorb during the phase change. In other words, the coolant and phase change medium work together to achieve graded control of the device junction temperature, effectively suppressing the sudden rise in junction temperature under transient conditions and significantly improving heat dissipation efficiency and system reliability.

[0033] The phase change working fluid and coolant are both independent and complementary, enabling graded control of the junction temperature of the device. They can provide good heat dissipation for power semiconductor devices under both steady-state and transient conditions. Therefore, the coolant circulation system does not require an increase in cooling configuration, which improves energy matching efficiency and reduces operating costs.

[0034] Furthermore, a groove is formed on the contact surface of the substrate for contacting the power semiconductor device. A working fluid channel for accommodating the phase change working fluid is embedded and fixed in the groove. The inner cavity of the working fluid channel forms a phase change working fluid flow channel. One side of the channel wall is flush with the contact surface of the substrate.

[0035] Furthermore, the groove has a U-shaped cross-section, and the working fluid pipe is a flat pipe.

[0036] Furthermore, the substrate includes two opposing and parallel contact surfaces, each with a groove, and a working fluid pipe is embedded and fixed in each groove, with the coolant flow channel located between the working fluid pipes on both sides.

[0037] Furthermore, the phase change working fluid channel is processed inside the substrate near the surface layer, and one side of the channel wall of the phase change working fluid channel is part of the substrate surface layer.

[0038] Furthermore, the phase change working fluid channel includes a horizontal section and inclined sections connected to both ends of the horizontal section and extending upwards at an angle.

[0039] Furthermore, on the same side of the substrate, two or more phase change working fluid channels are arranged at intervals along the vertical direction, and each phase change working fluid channel is connected to a manifold at both ends, with the manifold at both ends having an interface for connecting to the condenser.

[0040] Furthermore, the condenser is located above the radiator so that the phase change working fluid, which has been converted into liquid, flows back into the phase change working fluid channel under the action of gravity. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the heat dissipation system for the power semiconductor device of the present invention; Figure 2 This is a side cross-sectional view of the composite heat sink in the power semiconductor device heat dissipation system of the present invention; Figure 3 for Figure 2 Sectional view along line AA in the middle; Figure 4 for Figure 2 BB-direction sectional view.

[0042] In the diagram: 1. Substrate; 2. Coolant flow channel; 21. Inlet; 22. Outlet; 3. Phase change working fluid flow channel; 31. Horizontal section; 32. Inclined section; 4. Manifold; 41. Interface; 5. Connecting pipe; 6. Condenser. Detailed Implementation

[0043] The power semiconductor devices in converter valves experience a surge in losses under transient operating conditions, leading to a rapid increase in junction temperature within a short period. If the junction temperature exceeds the safety threshold, it will cause thermal failure of the devices, seriously threatening system stability. Traditional single-layer plate heat sinks rely on forced convection heat transfer with pure water, which, while meeting steady-state heat dissipation requirements, suffers from problems such as hysteresis in thermal resistance response, a single cooling mode, and low energy matching efficiency under transient operating conditions. Furthermore, existing technologies relying solely on phase change cooling media have limitations. The basic concept of this invention is to design a composite heat sink. The inner layer of this heat sink uses coolant to meet the steady-state heat dissipation requirements of the power semiconductor devices, while the outer layer integrates a phase change cooling medium to handle transient high heat flux density conditions. Through the synergistic work of the steady-state coolant layer and the transient phase change layer, graded control of the junction temperature of the power semiconductor devices is achieved, effectively suppressing the sudden rise in junction temperature under transient operating conditions, significantly improving heat dissipation efficiency and system reliability, and providing a new approach for the thermal management of high-power-density devices in converter valves.

[0044] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0045] An embodiment of the power semiconductor device heat dissipation system (hereinafter referred to as the heat dissipation system) in this invention: like Figure 1 As shown, the heat dissipation system includes a heat sink for contact mounting with power semiconductor devices. This heat sink is a composite heat sink, combining... Figure 2 , Figure 3 and Figure 4 As shown, it is formed by coupling a high thermal conductivity substrate 1 with a double-layer flow channel.

[0046] The substrate 1, made of a high thermal conductivity material, can be pure aluminum, aluminum alloy, pure copper, copper alloy, etc. The substrate 1 has contact surfaces for contacting power semiconductor devices (such as IGBTs and thyristors). In use, if the substrate 1 is positioned between two power semiconductor devices, contacting both devices on either side, then the substrate 1 has two contact surfaces, namely, two end faces in the thickness direction of the substrate 1. If the substrate 1 is positioned at the end of a converter valve assembly, contacting only one power semiconductor device, then the substrate 1 has only one contact surface, namely, one end face in the thickness direction of the substrate 1. In this embodiment, the substrate 1 has two contact surfaces, which are opposite to each other and arranged parallel to each other.

[0047] The "double layer" in the double-layer flow channel refers to a double cooling medium layer, that is, the substrate 1 is coupled with two different cooling mediums in the flow channel. Specifically, the substrate 1 is provided with a coolant flow channel 2 to allow the coolant to exchange heat through forced convection. The coolant can be pure water, water-based coolant (such as ethylene glycol aqueous solution), or non-water-based coolant (such as insulating oil).

[0048] Combination Figure 2 and Figure 3 As shown, the coolant flow channel 2 in this embodiment includes multiple branch channels arranged vertically and in parallel, with equal spacing between each branch channel, achieving uniform distribution within the substrate 1. A liquid inlet 21 is located on the bottom left side of the substrate 1, communicating with the main liquid inlet channel inside the substrate 1, which in turn communicates with each branch channel. A liquid outlet 22 is located on the bottom right side of the substrate 1, communicating with the main liquid outlet channel inside the substrate 1. The main liquid outlet channel is arranged horizontally parallel to the main liquid inlet channel and communicates with each branch channel.

[0049] The inlet 21 and outlet 22 are used to connect to the coolant circulation system (which typically includes pumps, heat exchangers, and other components). Under the action of the pump, the coolant in the circulation system enters the substrate 1 through the inlet 21, flows through various branch channels via the main inlet channel, and finally converges into the main outlet channel. It then returns to the coolant circulation system through the outlet 22, carrying away heat and forming a heat dissipation cycle. Under steady-state conditions, the coolant in the coolant channel 2 plays a major role in heat dissipation. Through forced convection heat transfer, it continuously removes the heat generated by the power semiconductor devices, providing stable heat dissipation capabilities and meeting the heat dissipation requirements during steady-state operation.

[0050] The dimensions and arrangement of the coolant flow channel 2 are determined based on the required flow resistance and thermal resistance of the converter valve. This embodiment only provides one specific implementation. In other embodiments, the coolant flow channel 2 may not be a strip-shaped flow channel arranged vertically and horizontally, but rather a serpentine or S-shaped flow channel, a planar spiral flow channel, or a radiating flow channel, or various other flow channel forms. The processing method of the flow channel can refer to existing technologies. In addition, the positions of the inlet and outlet can also be adjusted adaptively.

[0051] Combination Figure 1 , Figure 2 and Figure 4 As shown, a phase change working fluid flow channel 3 is provided on the surface of the substrate 1 so that the phase change working fluid can exchange heat through the latent heat of phase change. The surface of the substrate 1 refers to the surface near the contact surface that contacts the power semiconductor device.

[0052] In this invention, the boiling point of the phase change working fluid is greater than the temperature of the surface layer of substrate 1 (i.e., the surface layer of the heat sink) under steady-state conditions of the power semiconductor device, but less than the temperature of the surface layer of substrate 1 under transient conditions of the power semiconductor device. Thus, under steady-state conditions, the phase change working fluid does not play a role, and the coolant works alone to dissipate heat from the power semiconductor device, meeting the heat dissipation requirements of the power semiconductor device during steady-state operation and maintaining the normal temperature of the power semiconductor device.

[0053] When transient conditions occur, the heat generated by the power semiconductor device rises sharply. The phase change working fluid in the surface channel absorbs a large amount of heat and rapidly undergoes a phase change, transforming from a liquid to a gaseous state. Utilizing the latent heat of the phase change, it efficiently absorbs and removes heat, effectively suppressing the sudden rise in junction temperature and overcoming the problem of lag in thermal resistance response in traditional heat sinks. Simultaneously, the coolant in the internal coolant channel also exchanges heat through forced convection, removing the remaining heat that the phase change working fluid did not absorb during the phase change. In other words, the coolant and phase change working fluid work together to achieve graded control of the device junction temperature, effectively suppressing the sudden rise in junction temperature under transient conditions and significantly improving heat dissipation efficiency and system reliability.

[0054] Specifically, this embodiment employs embedded tube technology. A groove is formed on the contact surface of the substrate 1 for contacting the power semiconductor device. A working fluid pipe for filling the phase change working fluid is embedded and fixed within the groove. The inner cavity of the working fluid pipe forms a phase change working fluid flow channel. One side of the working fluid pipe wall is flush with the contact surface of the substrate 1 (the remaining pipe walls are in close contact with the groove wall). In this way, one side of the working fluid pipe wall and the contact surface of the substrate 1 simultaneously contact the power semiconductor device. Under steady-state conditions, the heat dissipated by the power semiconductor device can be transferred to the interior of the substrate 1 through the contact surface and carried away by forced convection of the coolant. Under transient conditions, the heat generated by the sudden rise in junction temperature of the power semiconductor device directly acts on the pipe wall of the working fluid pipe, causing the phase change working fluid to rapidly absorb a large amount of heat and immediately undergo a phase change. This utilizes the latent heat of phase change to efficiently absorb and remove heat, effectively suppressing the sudden rise in junction temperature.

[0055] Furthermore, such as Figure 2 As shown, since the substrate 1 has two contact surfaces in this embodiment, grooves are provided on both contact surfaces, and working fluid pipes are embedded and fixed in the grooves. The coolant channel 2 is located between the working fluid pipes on both sides, that is, the coolant channel 2 is centrally arranged in the longitudinal section of the substrate 1. In other embodiments, if the substrate 1 has only one contact surface, it is only necessary to provide a groove on the contact surface and embed and fix the working fluid pipe.

[0056] Furthermore, the cross-section of the aforementioned groove is U-shaped, with the groove opening facing one side. The aforementioned working fluid pipe is a flat tube (with a rectangular cross-section), which facilitates configuration and manufacturing. Moreover, the thickness direction of the flat tube is consistent with the thickness direction of the substrate 1, so that the large surface of the pipe wall on one side of the flat tube serves as the pipe wall in contact with the power semiconductor device, thereby increasing the heat exchange area and improving the heat absorption effect of the phase change working fluid.

[0057] In other embodiments, the working fluid conduit can also be a conduit with a square cross-section, or it can be a specially made conduit with a rhomboid, triangular or trapezoidal cross-section. The shape of the groove is adapted to the shape of the working fluid conduit so that the working fluid conduit can be embedded and fixed in the groove (the specific fixing method can be welding or interference fit). One side of the working fluid conduit's flat wall (preferably the large surface) is flush with the contact surface of the substrate 1, ensuring that the conduit wall and the contact surface of the substrate 1 are in contact with the power semiconductor device at the same time.

[0058] In other embodiments, the working fluid conduit may not be a prefabricated conduit with a flat conduit wall, but rather a round tube pressed into the groove. During the pressing process, the round tube is deformed into a roughly elliptical conduit. After pressing, the side under pressure will form a flat conduit wall that is flush with the contact surface of the substrate 1.

[0059] In other embodiments, the phase change working fluid channel may not be formed by the inner cavity of an embedded working fluid pipe, but rather by a phase change working fluid channel directly formed inside the substrate 1 near the surface. For example, a through hole can be formed along the length or width of the substrate 1, serving as the phase change working fluid channel. In this case, the through hole can be a circular hole or a rectangular hole. Alternatively, a groove, such as a U-shaped groove or a semi-circular arc groove, can be formed on the end face of the substrate body first, and then a cover plate can be sealed and fixed. The cover plate and the groove together form the phase change working fluid channel, and the cover plate and the substrate body together form the substrate. In these cases, since the phase change working fluid channel is close to the surface of the substrate 1, one side of the channel wall of the phase change working fluid channel is part of the surface of the substrate 1. Furthermore, since the surface of the substrate 1 is in direct contact with the power semiconductor device, it can also achieve a heat exchange effect that is essentially equivalent to that of an embedded working fluid pipe.

[0060] Furthermore, on the same side of the substrate 1, two or more phase change working fluid channels (including phase change working fluid channels formed by the inner cavity of the embedded working fluid pipe and phase change working fluid channels formed by direct processing) are evenly spaced in the vertical direction (four in this embodiment; in other embodiments, two, three, five or more can be set according to the specific dimensions of the substrate 1 and the phase change working fluid channels), and each phase change working fluid channel is connected to a manifold 4 at both ends. The manifold 4 at both ends has an interface 41, which is connected to the condenser 6 through the connecting pipe 5.

[0061] In this way, the surface of the substrate 1 is fully utilized to set more phase change working fluid channels to ensure heat dissipation under transient conditions. At the same time, multiple phase change working fluid channels are connected to the condenser 6 through the manifold 4, which simplifies the structure and avoids overly complex piping.

[0062] Specifically, if the phase change working fluid channel is formed by the inner cavity of an embedded working fluid pipe, then both ends of the working fluid pipe extend out of the substrate 1 to form joints, and the joints are fixedly connected to the corresponding manifold 4. If the phase change working fluid channel is directly formed on the substrate 1, then multiple joints are connected to the manifold 4, and each joint is connected to the phase change working fluid channel in a one-to-one correspondence.

[0063] In other embodiments, whether the phase change working fluid channel is formed by the inner cavity of the embedded working fluid pipe or the phase change working fluid channel is directly formed on the substrate, both ends of each phase change working fluid channel can be connected to the condenser through independent connecting pipes.

[0064] Furthermore, such as Figure 4As shown, the phase change working fluid channel 3 (including the phase change working fluid channel formed by the inner cavity of the embedded working fluid pipe and the phase change working fluid channel formed by direct processing) includes a horizontal section 31 and inclined sections 32 connected to both ends of the horizontal section 31 and extending upwards at an incline. The inclined sections 32 on both sides are symmetrically arranged relative to the middle horizontal section 31. In use, the phase change working fluid is filled at least to the connection position between the manifold 4 and the uppermost phase change working fluid channel 3 (and at most to the interface position of the manifold 4). In each phase change working fluid channel 3, when a transient condition occurs, the phase change working fluid in the horizontal section 31 and the inclined section 32 absorbs heat and rapidly undergoes a phase change, changing from a liquid state to a gaseous state. The gaseous working fluid can smoothly enter the manifold 4 along the inclined section 32, and then enter the condenser 6 through the manifold 4 and the connecting pipe 5, thereby improving the cooling efficiency.

[0065] In other embodiments, the phase change working fluid channel 3 can also be set at an overall inclination. Similarly, multiple phase change working fluid channels 3 are arranged in parallel at intervals. After phase change, the gaseous working fluid in each phase change working fluid channel 3 moves upward along the inclination phase change working fluid channel and enters the manifold 4, and then enters the condenser 6 through the connecting pipe 5.

[0066] The connecting pipe 5 is made of insulating material, which serves as insulation and isolation.

[0067] The condenser 6 is made of thermally conductive material and is positioned above the radiator, allowing the gaseous working fluid to autonomously enter the condenser 6 along the connecting pipe 5. Within the condenser 6, the gaseous fluid transforms into a liquid state, condensing into a liquid working fluid. The liquid working fluid then flows back into the phase change working fluid channel 3 under gravity, achieving recycling. Therefore, the phase change working fluid channel 3 adopts a non-powered, recirculating design, enabling long-term operation after a single replenishment of the phase change working fluid without requiring additional power input.

[0068] In practical applications, a mounting bracket for fixing the condenser 6 needs to be set above the converter valve assembly composed of multiple power semiconductor devices. The condenser 6 exchanges heat with the air naturally (the indoor temperature of the converter station can fully meet the condensation efficiency of the phase change working fluid). In order to further improve the phase change efficiency, a converter valve assembly can be configured with multiple condensers 6, so that one or two radiators are connected to one condenser 6.

[0069] In other embodiments, the condenser 6 may not be arranged above the radiator, but at the same height as the radiator or below the radiator. In this case, the gaseous working fluid generated by the phase change in the radiator can enter the condenser under the action of pressure difference, and the liquid working fluid in the condenser needs to be pumped back to the phase change working fluid channel by a pump.

[0070] In use, it is known that the surface temperature of the heat sink of the power semiconductor device is T1 under steady-state conditions and T2 under transient conditions, and the boiling point of the phase change material is T3, where T2 > T3 > T1.

[0071] Under steady-state conditions, the surface temperature T1 of the heat sink for power semiconductor devices is lower than the boiling point T3 of the phase change material. At this point, the phase change material has not reached its phase change temperature. The heat generated by the power device is transferred inwards through the heat sink surface and finally exchanges heat with the coolant in the coolant channels, completing heat dissipation. Under this condition, the heat generated by the power semiconductor device is mainly dissipated by the coolant.

[0072] Under transient operating conditions, the surface temperature of the heat sink in power semiconductor devices quickly rises to T2, which is higher than the boiling point T3 of the phase change material (PCM). At this point, the PCM has reached its phase change temperature. The PCM in the PCM working fluid channel absorbs heat and rapidly undergoes a phase change, efficiently absorbing and carrying away some heat through its latent heat of phase change, thus suppressing a sudden rise in the junction temperature of the power semiconductor device. After the phase change cooling layer absorbs some heat, the surface temperature of the heat sink decreases. When the temperature falls below the boiling point of the PCM, the phase change stops, and the remaining heat is transferred inward through the heat sink surface, exchanging heat with the coolant in the coolant channel, completing heat dissipation. Under this condition, the heat generated by the power semiconductor device is dissipated through the coordinated work of the surface phase change cooling layer and the inner coolant layer, achieving graded control of the device junction temperature.

[0073] As a specific example, suppose the heat generation of power devices under steady-state and transient overload conditions in a certain engineering project is as shown in the table below:

[0074] The formula for calculating the surface temperature of a radiator is: .

[0075] Wherein: T s T1 is the surface temperature of the radiator, in °C; T2 is the inlet water temperature of the radiator's pure water cooling layer, in °C; P is the heat output of the power device, in kW; R s This represents the thermal resistance of the power device, expressed in K / kW.

[0076] The formula for calculating the junction temperature of power devices is: .

[0077] Wherein: T j T represents the junction temperature of power devices, expressed in °C. s R represents the surface temperature of the heat sink, in °C; P represents the heat output of the power device, in kW; thy This represents the thermal resistance of the power device, expressed in K / kW.

[0078] Based on the above parameters and calculation formula, we can conclude that: Under steady-state conditions, the surface temperature T of the radiator s =67.8℃, junction temperature T of power devices j =83.5℃. At this point, the surface temperature of the heat sink does not exceed the evaporation temperature of the phase change cooling medium. The phase change cooling medium remains unchanged, and the heat generated by the power device is transferred inward through the surface layer of the heat sink, and finally exchanges heat with the inner pure water cooling layer. The junction temperature of the power device is stabilized below 90℃.

[0079] Under transient operating conditions, if only a pure water cooling layer is configured, the surface temperature T of the radiator will be... s =78.8℃, junction temperature T of power devices j =102.5℃, the junction temperature of the power device exceeds the upper limit of safe operation.

[0080] Under transient conditions, if a composite heat sink is used, the surface temperature of the heat sink exceeds the evaporation temperature of the phase change cooling medium. The phase change cooling medium absorbs heat and undergoes a rapid phase change, suppressing a sudden rise in the heat sink surface temperature and maintaining it at the evaporation temperature of 68°C. At this point, the transient junction temperature T of the power device... j =91.5℃.

[0081] In summary, the composite heat sink proposed in this invention has two operating mechanisms. Under steady-state conditions, the inner coolant cooling layer operates independently to maintain the normal temperature of the device. Under transient conditions, the surface phase-change cooling layer immediately activates and works in conjunction with the inner coolant cooling layer. The two cooling media operate independently yet in cooperation, achieving graded control of the device junction temperature. This provides excellent heat dissipation for power semiconductor devices under both steady-state and transient conditions, offering a new approach to thermal management of high-power-density devices in converter valves.

[0082] In summary, the present invention has the following advantages: I. Improved transient response speed: The phase change cooling layer can respond quickly under transient conditions, using the latent heat of phase change to quickly remove heat, overcoming the problem of lag in thermal resistance response of traditional heat sinks, effectively suppressing the sudden rise in junction temperature, and improving the reliability of the device in transient processes.

[0083] II. Optimized Cooling Mode: Different cooling mechanisms are employed for steady-state and transient operating conditions, avoiding the drawbacks of a single cooling mode. Cooling relies on coolant during steady-state operation, while phase-change cooling is activated during transient operation, thus optimizing the cooling mode and improving heat dissipation efficiency.

[0084] 3. Improve energy matching efficiency: Through a reasonable dual-layer structure design, while meeting heat dissipation requirements, it avoids the energy waste caused by excessively increasing the cooling configuration to adapt to transient operating conditions, thereby improving energy matching efficiency and reducing operating costs.

[0085] The embodiment of the converter valve assembly in this invention is as follows: the converter valve assembly includes a power semiconductor device, the power semiconductor device is equipped with a heat dissipation system, and the heat dissipation system is the same as the heat dissipation system of the power semiconductor device in the above embodiment, and will not be repeated here.

[0086] The implementation method of the composite heat sink in this invention is as follows: the composite heat sink is the same as the heat sink in the above-mentioned power semiconductor device heat dissipation system implementation method, and will not be repeated here.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A composite radiator, characterized in that, The device includes a substrate with internal coolant channels for forced convection heat transfer. A phase change working fluid (PCM) channel is located on the substrate surface for latent heat transfer. The PCM has a boiling point higher than the substrate surface temperature under steady-state conditions but lower than the substrate surface temperature under transient conditions. This allows the coolant to dissipate heat from the power semiconductor device under steady-state conditions alone, and under transient conditions, the coolant and PCM work together to dissipate heat.

2. The composite radiator according to claim 1, characterized in that, The substrate has a groove on the contact surface for contacting power semiconductor devices. A working fluid channel for accommodating phase change working fluid is embedded and fixed in the groove. The inner cavity of the working fluid channel forms a phase change working fluid flow channel. One side of the channel wall is flush with the contact surface of the substrate.

3. The composite radiator according to claim 2, characterized in that, The groove has a U-shaped cross-section, and the working fluid pipe is a flat pipe.

4. The composite radiator according to claim 2, characterized in that, The substrate includes two opposing and parallel contact surfaces. Grooves are provided on both contact surfaces, and working fluid pipes are embedded and fixed in the grooves. Coolant flow channels are located between the working fluid pipes on both sides.

5. The composite radiator according to claim 1, characterized in that, The phase change working fluid channel is processed inside the substrate near the surface, and one side of the channel wall is part of the substrate surface.

6. The composite radiator according to any one of claims 1 to 5, characterized in that, The phase change working fluid channel includes a horizontal section and inclined sections that are connected to both ends of the horizontal section and extend upwards at an angle.

7. The composite radiator according to any one of claims 1 to 5, characterized in that, On the same side of the substrate, two or more phase change working fluid channels are arranged at intervals in the vertical direction, and each phase change working fluid channel is connected to a manifold at both ends, and the manifold at both ends has an interface for connecting to the condenser.

8. A heat dissipation system for a power semiconductor device, the heat dissipation system comprising a heat sink for being disposed in close contact with the power semiconductor device, characterized in that, The radiator is the composite radiator as described in any one of claims 1 to 7, and the heat dissipation system further includes a condenser connected to the phase change working fluid channel in the composite radiator to allow the phase change working fluid to change from a gaseous state to a liquid state and flow back to the phase change working fluid channel.

9. The power semiconductor device heat dissipation system according to claim 8, characterized in that, The condenser is located above the composite radiator so that the phase change working fluid, which has been converted into liquid, flows back into the phase change working fluid channel under the action of gravity.

10. A converter valve assembly, comprising a power semiconductor device, the power semiconductor device being configured with a heat dissipation system, characterized in that, The heat dissipation system is the power semiconductor device heat dissipation system as described in claim 8 or 9.

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