PTC liquid heater based on intelligent power management and control method thereof

Abstract

The invention discloses a PTC liquid heater based on intelligent power management and a control method thereof, and belongs to the field of new energy automobile battery thermal management systems. The heater hardware comprises an upper shell, a lower shell, a heating body, a water inlet tank, a water outlet tank and an electronic controller. The heating body is clamped through the reinforcing metal plate assembly, and heat exchange is enhanced through the high-heat-conduction ceramic substrate. The water inlet temperature sensor and the water outlet temperature sensor are arranged at the bottom of the water tank so as to avoid gas phase interference, and the water inlet temperature sensor and the water outlet temperature sensor form a multi-mode sensing system with the IGBT temperature sensor. The electronic controller executes an intelligent algorithm; the semi-water dry burning risk is accurately identified through a quantification formula; under the risk working condition, starting a self-adaptive PID algorithm taking the safety parameter deviation as input, and dynamically limiting the output power; and the thermal load is balanced by adopting an IGBT power polling strategy. Through deep fusion of a hardware structure and a control algorithm, precise protection, intelligent power adjustment and high reliability are realized, and the strict working condition requirements of the commercial vehicle are met.

Description

Technical Field

[0001] This invention belongs to the technical field of thermal management systems for new energy vehicles, specifically relating to a PTC liquid heater based on intelligent power management and its control method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, efficient, safe, and reliable battery thermal management systems have become crucial for ensuring vehicle performance and lifespan. In low-temperature environments, PTC liquid heaters are needed to heat the battery coolant. However, existing technologies have significant shortcomings: First, the structural reliability is poor: PTC heating elements are prone to cracking due to mechanical fatigue under thermal shock.

[0003] Secondly, the dry-burning monitoring mechanism is crude and unreliable: on the one hand, traditional temperature sensors are mostly placed on the top of the water tank, which are easily affected by the accumulation of air or steam, resulting in distorted water temperature measurements; on the other hand, the existing protection logic is usually only based on simple temperature difference thresholds (such as ΔT>20℃) or absolute temperature thresholds, which cannot effectively distinguish between "normal large temperature difference heating in cold environments" and "dangerous half-water dry-burning" conditions, resulting in a high misjudgment rate.

[0004] Furthermore, the protection strategies are too simplistic: when faced with potential risks, most solutions adopt a "one-size-fits-all" approach of directly cutting off the power, which interrupts heating and affects the user experience, and fails to maintain vehicle operation while ensuring safety.

[0005] Finally, there are shortcomings in integration and durability: the waterproof, insulation, and vibration-resistant designs need to be improved, making it difficult to meet the urgent needs of commercial vehicles for miniaturization and high reliability under harsh operating conditions.

[0006] Therefore, there is an urgent need for a high-performance PTC heater solution that integrates advanced structural design, precise sensing, and intelligent control. Summary of the Invention

[0007] The purpose of this invention is to provide a PTC liquid heater and its control method based on intelligent power management, which solves the problems of unreliable dry burning monitoring mechanism, single protection strategy and poor structural reliability of PTC liquid heater in the prior art.

[0008] The objective of this invention can be achieved through the following technical solutions: A control method for a PTC liquid heater based on intelligent power management, wherein the heater includes an inlet water temperature sensor, an outlet water temperature sensor, an IGBT temperature sensor, and an electronic controller, the control method comprising the following steps: S1: Real-time acquisition of inlet water temperature T_in, outlet water temperature T_out, and temperature of each IGBT T_igbt_i, where i represents the IGBT number; S2: Calculate the inlet and outlet water temperature difference ΔT = T_out - T_in, and calculate the temperature rise rate V_igbt_i for each IGBT; S3: If the first judgment condition and / or the second judgment condition are met, the heater is identified as entering a risky operating condition; The first determination condition is: (T_out > T_high_thresh) or (ΔT < ΔT_low_thresh), where T_high_thresh is the preset maximum temperature value and ΔT_low_thresh is the preset minimum temperature difference value. The second condition is: max(V_igbt_i) > V_thresh, where V_thresh is the preset maximum temperature rise rate; S4: If the system enters a risky operating condition, an adaptive PID controller is used. The input error e(t) of the controller is defined as min((T_igbt_max - T_igbt(t)), (ΔT_safe - ΔT(t))), and the safe power limit P_safe is output according to the PID algorithm. Where T_igbt_max is the preset IGBT safety limit, T_igbt(t) is the preset safety temperature difference limit, and T_igbt(t) is the highest temperature among the three IGBTs at the current moment. S5: Based on the safe power limit P_safe, the total power output is distributed in a power rotation manner by dynamically adjusting the working time slice T_on_i and cooling time slice T_off_i of each IGBT device.

[0009] As a further aspect of the present invention, in the first determination condition, the value range of T_high_thresh is 60℃~70℃, and the value range of ΔT_low_thresh is 2℃~5℃.

[0010] As a further aspect of the present invention, the value of V_thresh ranges from 5℃ / s to 10℃ / s, and the sampling period of the temperature rise rate V_igbt_i is less than or equal to 50ms.

[0011] As a further aspect of the present invention, the operating time slice T_on_i of a single IGBT device is negatively correlated with its real-time temperature T_igbt_i, and the cooling time slice T_off_i is positively correlated with its real-time temperature T_igbt_i.

[0012] The present invention also discloses a PTC liquid heater based on intelligent power management for executing the above control method. The heater includes a heating element, an inlet tank, an outlet tank, an electronic controller, and a terminal block assembly. The upper shell and the lower shell are sealed to form a cavity. The heating element and the electronic controller are placed inside the cavity. The heating element is located between the inlet tank and the outlet tank. The temperature sensing elements of the inlet water temperature sensor and the outlet water temperature sensor are respectively located in the bottom area of ​​the inlet water tank and the outlet water tank; The heating element includes a PTC heating module. The heating surface of the PTC heating module is tightly attached to one side of a high thermal conductivity ceramic substrate through thermally conductive silicone grease. The other side of the high thermal conductivity ceramic substrate is also attached to the wide side of the flat tube through thermally conductive silicone grease. The flat tube has multiple microchannels inside for coolant flow; The assembly of the PTC heating module, the high thermal conductivity ceramic substrate, and the flat tube is entirely encased in a reinforced sheet metal component made of stainless steel.

[0013] The beneficial effects of this invention are: Compared with the prior art, the present invention has the following significant advantages: This application achieves accurate and early identification of high-risk operating conditions such as "half-water dry burning" by combining bottom sensor layout with quantitative judgment formula, which greatly reduces false alarms and missed alarms. This application enables a shift from passive shutdown to active and smooth power management, maximizing the maintenance of heating function while ensuring safety, thereby improving user experience and vehicle usability. This application combines a load balancing strategy with comprehensive sealing protection to ensure the heater's long lifespan and high reliability in harsh environments.

[0014] The integrated design of this application meets the needs of commercial vehicles for miniaturization and modularization of thermal management components. Attached Figure Description

[0015] The invention will now be further described with reference to the accompanying drawings.

[0016] Figure 1 This is a schematic diagram of the liquid heater of the present invention; Figure 2 This is a schematic diagram of the liquid heater of the present invention from another angle; Figure 3 This is a schematic diagram of the liquid heater of the present invention after removing the upper and lower shells; Figure 4 This is a schematic diagram of the liquid heater of the present invention after removing the shell and the adhesive sponge. Figure 5 This is a schematic diagram of the liquid heater of the present invention after removing the housing and control circuit board; Figure 6 This is a structural diagram of the terminal block assembly; Figure 7 This is a schematic diagram of a portion of the heating element; Figure 8 This is a schematic diagram of the PTC heating module; Figure 9 This is a schematic diagram of the flat tube structure; Figure 10 This is a schematic diagram of power regulation under risky operating conditions using adaptive PID control; Figure 11 This is the timing diagram of the IGBT power polling strategy.

[0017] In the diagram: 1. Upper housing; 2. Lower housing; 3. Heating element; 4. Electronic controller; 5. Terminal block assembly; 6. Inlet pipe; 7. Inlet tank; 8. Outlet tank; 9. Outlet pipe; 10. IGBT heat sink; 11. PTC heating module; 12. Low-voltage wiring harness; 13. High-voltage wiring harness; 14. Vent valve; 15. Moisture-absorbing adhesive sponge; 16. Waterproof sealing strip; 17. Adhesive-backed sponge block; 18. Reinforced sheet metal assembly; 19. Reinforced sheet metal body; 20. Reinforced sheet metal cover plate; 21. Inlet temperature sensor; 22. Outlet temperature sensor; 23. Limiting plate; 24. Flat tube; 25. Grounding screw hole; 26. High thermal conductivity ceramic substrate. Detailed Implementation

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

[0019] Example 1 PTC liquid heaters based on intelligent power management, such as Figures 1 to 9 As shown, it includes a heating element 3, which includes a PTC heating module 11. The PTC heating module 11 is formed by welding multiple PTC chips in parallel. The heating surface of the PTC heating module 11 is tightly attached to one side of a high thermal conductivity ceramic substrate 26 through thermally conductive silicone grease. The other side of the high thermal conductivity ceramic substrate 26 is also attached to the wide side of the flat tube 24 through thermally conductive silicone grease.

[0020] The flat tube 24 has multiple microchannels inside, which allow the coolant to fully absorb heat as it flows through.

[0021] The radius (R) of the flat tube 24 is thickened to increase its resistance to alternating hot and cold temperatures; The high thermal conductivity ceramic substrate 26 can be an alumina ceramic substrate. The assembly of the PTC heating module 11, the high thermal conductivity ceramic substrate 26 and the flat tube 24 is completely covered by a reinforced sheet metal component 18 made of stainless steel.

[0022] The reinforced sheet metal assembly 18 consists of a reinforced sheet metal body 19 and a reinforced sheet metal cover plate 20, and the cross-section of the reinforced sheet metal assembly 18 is U-shaped.

[0023] The upper edges of both sides of the sheet metal body 19 are provided with outwardly folded limiting plates 23. The sheet metal cover plate 20 has elongated holes corresponding to the positions of the limiting plates 23. During assembly, after the limiting plates 23 are inserted into the elongated holes, a certain displacement is applied to make the two misaligned and clamped, thereby providing a continuous and uniform clamping force for the PTC module, effectively resisting the expansion stress caused by the hot and cold cycles, and preventing cracking.

[0024] The two ends of the flat tube 24 are connected to the inlet tank 7 and the outlet tank 8 respectively by brazing. The outer sides of the inlet tank 7 and the outlet tank 8 are covered with a 1mm thick steel plate reinforcement layer and locked with metal clamps to prevent high pressure expansion.

[0025] The inlet water tank 7 is equipped with an inlet water temperature sensor 21, and the outlet water tank 8 is equipped with an outlet water temperature sensor 22. The inlet temperature sensor 21 and the outlet temperature sensor 22 are PT1000 platinum resistance thermometers.

[0026] To ensure measurement accuracy, the metal temperature probes of the inlet temperature sensor 21 and the outlet temperature sensor 22 are directly installed and sealed at the lowest point of the inlet tank 7 and the outlet tank 8, respectively. This design ensures that the temperature sensing part of the sensor is always immersed in the coolant, completely avoiding temperature measurement distortion caused by air bubbles or steam that may exist in the pipeline accumulating at the top.

[0027] A heat sink 10 is tightly attached to the side wall of the water inlet tank 7 using a thermally conductive material. An IGBT power device is mounted on the heat sink 10. During operation, the coolant flowing through the water tank dissipates heat from the IGBT. An IGBT temperature sensor is also fixedly installed on the heat sink 10 to directly monitor the junction temperature of the IGBT power device.

[0028] The heating element 3, the water inlet tank 7, and the water outlet tank 8 are all located in the protective shell formed by the combination of the upper shell 1 and the lower shell 2. The upper shell 1 and the lower shell 2 are made of aluminum alloy die-cast shell or PA66 mixed glass fiber high temperature resistant and high strength flame retardant plastic shell, and are equipped with internal reinforcing ribs to improve structural strength.

[0029] The mating surfaces of the upper housing 1 and the lower housing 2 are machined with sealing grooves, and double silicone waterproof sealing strips 16 are embedded in the sealing grooves to ensure IP67 level sealing at the joint of the protective housing.

[0030] A vent valve 14 is installed on the top of the upper housing 1 to balance the internal and external pressures. After assembly, a cured adhesive with good thermal conductivity is poured into the cavity formed by the housing and internal components, to a height of about 70% (2 / 3 to 3 / 4) of the cavity height, to achieve fixation, buffering, auxiliary heat dissipation and secondary sealing of the internal components.

[0031] The adhesive with good thermal conductivity after curing is an addition-type two-component high-temperature resistant flame-retardant silicone adhesive or a thermally conductive epoxy resin adhesive. The lower housing 2 is fixed with a control circuit board of an electronic controller 4 by a bracket. The control circuit board and the inner wall of the upper housing 1 are lined with moisture-absorbing adhesive sponge 15 made of IXPE material to absorb any condensation that may occur.

[0032] The electrical connection of the PTC module is also achieved by setting up terminal block assembly 5. Flame-retardant insulating partitions are installed between the copper busbar and the busbar of terminal block assembly 5, and silicone insulating sheets are placed at key contact points to prevent electric arcing.

[0033] The lower housing 2 has independent high-voltage wiring harness interface 13 and low-voltage wiring harness interface 12 on its side for easy wiring. Grounding is achieved by using an internally threaded copper post pre-embedded in the lower housing 2 and connecting to an external ground wire through a grounding screw hole 25.

[0034] Example 2 PTC liquid heater control method based on intelligent power management, such as Figures 10 to 11 As shown, it includes: 1. Data Acquisition and Preprocessing After the system is powered on, the controller cyclically acquires the following signals through the ADC module at a period of 20ms: The voltage value of the inlet temperature sensor 21 is converted into temperature T_in.

[0035] The voltage value of the outlet temperature sensor 22 is converted into temperature T_out.

[0036] The voltage values ​​of the three IGBT temperature sensors are converted into temperatures T_igbt_1, T_igbt_2, and T_igbt_3, respectively. Simultaneously, the following calculations are performed in each sampling period: Real-time temperature difference ΔT = T_out - T_in.

[0037] The instantaneous temperature rise rate of each IGBT is V_igbt_i = (T_igbt_i [k] - T_igbt_i [k-1]) / 0.02 (unit: ℃ / s).

[0038] 2. Quantitative identification of risky operating conditions The collected data is continuously compared with preset thresholds to perform multimodal risk assessment. Condition A (High Temperature, Small Temperature Difference): Determine if both T_out > T_high_thresh and ΔT < ΔT_low_thresh are satisfied simultaneously. This condition is used to identify a semi-dry-burning state where heat accumulates due to stagnant water flow.

[0039] Where T_high_thresh is the preset maximum temperature value, and ΔT_low_thresh is the preset minimum temperature difference value; the value range of T_high_thresh is 60℃~70℃, and the value range of ΔT_low_thresh is 2℃~5℃.

[0040] Condition B (IGBT overheat surge): Take the largest temperature rise rate among the three IGBT temperature sensors and determine whether it satisfies max(V_igbt_i) > V_thresh; Where V_thresh is the preset maximum temperature rise rate; the value of V_thresh ranges from 5℃ / s to 10℃ / s; This condition is used for rapid response to a sharp temperature rise caused by a sudden deterioration in heat dissipation (such as the flow of air bubbles).

[0041] If either condition A or condition B is met, the system immediately switches from "normal heating mode" to "risk protection mode".

[0042] 3. Adaptive safety power decision (risk protection mode) In risk protection mode, the traditional isothermal PID controller is suspended. A safety-priority adaptive PID controller is then activated.

[0043] Error Calculation: The input error e(t) of this controller is redefined, no longer targeting the set temperature, but rather the system safety boundary. Specifically: e(t) = min((105-T_igbt_max(t)), (15-ΔT(t))) Where T_igbt_max(t) is the highest temperature among the three IGBTs at the current moment.

[0044] This formula means that the controller always focuses on the "most dangerous" parameter (closest to the IGBT safety limit of 105℃, or closest to the safe temperature difference limit of 15℃) and strives to minimize the deviation of this most dangerous parameter.

[0045] Power limit calculation: The safe power limit is calculated using a positional PID algorithm. P_safe: P_safe [k] = Kp * e[k] + Ki * Σe[j] + Kd * (e[k] - e[k-1]) Where Kp, Ki, and Kd are conservative parameters tuned in risk mode. The calculated P_safe is the maximum allowable output power value for the current cycle, and its value will change dynamically, such as... Figure 10 As shown.

[0046] 4. IGBT power rotation and load balancing To achieve P_safe power output and prevent overheating of a single IGBT during prolonged operation, a dynamic load balancing strategy is employed. The timing details are provided below. Figure 11 .

[0047] When three IGBTs are configured with three temperature sensors, the solution is as follows: The controller maintains a scheduling queue for the three IGBTs. At any given time, typically only one or two IGBTs are operated (via PWM chopping) to handle the load corresponding to P_safe; Each IGBT is allocated a base operating time slice T_base (e.g., 10 seconds) and a base cooling time slice.

[0048] Dynamic adjustment: At the beginning of each scheduling cycle, calculate the average temperature T_avg of the three IGBTs. Then, dynamically adjust the current working time of each IGBT based on its real-time temperature: T_on_i = T_base - α * (T_igbt_i - T_avg) / / Higher temperature, shorter working time T_off_i = T_base + β * (T_igbt_i - T_avg) / / Higher temperature, longer cooling time (α and β are positive coefficients less than 1, determined experimentally); This strategy ensures that the heat load is actively and evenly distributed among all IGBTs, effectively preventing local overheating and significantly improving system lifespan.

[0049] When three IGBTs are configured with one temperature sensor, the solution is as follows: In risk protection mode, to ensure safe power output P_safe, the controller employs a preventative load balancing round-robin strategy. Since there is only one IGBT temperature sensor, the core strategy has been adjusted from 'based on real-time temperature feedback' to 'based on operating history and status prediction'.

[0050] Option A (based on cumulative operating time): The controller internally maintains a counter that records the cumulative on-time of each IGBT in risk mode. The scheduler always prioritizes the IGBT with the shortest cumulative on-time to take over. This ensures that the 'work-rest' level of all IGBTs tends to be balanced during long-term operation, avoiding excessive fatigue of a single device.

[0051] Option B (based on estimated temperature): The scheduler makes decisions based on the estimated temperature T_igbt_i_est. While meeting power requirements, it prioritizes IGBTs with lower estimated temperatures. This method allows for a more precise dynamic balance of heat load.

[0052] In practical applications, the two schemes can be combined to form a comprehensive scheduling rule, which can effectively implement thermal load management and extend system life even in the absence of multi-channel direct temperature monitoring.

[0053] 5. Mode Switching and Recovery When the risk assessment conditions (A and B) are not met for more than a preset time (e.g., 30 seconds) and the system parameters tend to stabilize, the controller automatically exits the risk protection mode and resumes normal temperature control logic.

[0054] The advantage of this invention is that it upgrades a passive and simple protection system into an active and intelligent thermal safety management system, which can make optimal decisions under complex operating conditions, taking into account safety, availability and reliability.

[0055] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for controlling a PTC liquid heater based on intelligent power management, said heater comprising a water inlet temperature sensor (21), a water outlet temperature sensor (22), an IGBT temperature sensor and an electronic controller (4), characterized in that, Includes the following steps: S1: Real-time acquisition of inlet water temperature T_in, outlet water temperature T_out, and temperature of each IGBT T_igbt_i, where i represents the IGBT number; S2: Calculate the inlet and outlet water temperature difference ΔT = T_out - T_in, and calculate the temperature rise rate V_igbt_i for each IGBT; S3: If the first judgment condition and / or the second judgment condition are met, the heater is identified as entering a risky operating condition; The first determination condition is: (T_out > T_high_thresh) or (ΔT < ΔT_low_thresh), where T_high_thresh is the preset maximum temperature value and ΔT_low_thresh is the preset minimum temperature difference value. The second condition is: max(V_igbt_i) > V_thresh, where V_thresh is the preset maximum temperature rise rate; S4: If the system enters a risky operating condition, an adaptive PID controller is used. The input error e(t) of the controller is defined as min((T_igbt_max - T_igbt(t)), (ΔT_safe - ΔT(t))), and the safe power limit P_safe is output according to the PID algorithm. Where T_igbt_max is the preset IGBT safety limit, T_igbt(t) is the preset safety temperature difference limit, and T_igbt(t) is the highest temperature among the three IGBTs at the current moment. S5: Based on the safe power limit P_safe, the total power output is distributed in a power rotation manner by dynamically adjusting the working time slice T_on_i and cooling time slice T_off_i of each IGBT device.

2. The method of claim 1, wherein, In the first determination condition, the value range of T_high_thresh is 60℃~70℃, and the value range of ΔT_low_thresh is 2℃~5℃.

3. The method of claim 1, wherein, In the second determination condition, the value range of V_thresh is 5℃ / s to 10℃ / s, and the sampling period of the temperature rise rate V_igbt_i is less than or equal to 50ms.

4. The method of claim 1, wherein, In step S5, the operating time slice T_on_i of a single IGBT device is negatively correlated with its real-time temperature T_igbt_i, and the cooling time slice T_off_i is positively correlated with its real-time temperature T_igbt_i.

5. A PTC liquid heater based on intelligent power management, used to execute the control method described in any one of claims 1-4, the heater comprising a heating element (3), an inlet tank (7), an outlet tank (8), an electronic controller (4), and a terminal block assembly (5), wherein the upper housing (1) and the lower housing (2) are sealed to form a cavity, the heating element (3) and the electronic controller (4) are placed inside the cavity, and the heating element (3) is disposed between the inlet tank (7) and the outlet tank (8), characterized in that: The temperature sensing elements of the inlet water temperature sensor (21) and the outlet water temperature sensor (22) are respectively located in the bottom area of ​​the inlet water tank (7) and the outlet water tank (8); A heat sink plate (10) is tightly attached to the side wall of the water inlet tank (7) by a heat-conducting material. An IGBT is attached to the heat sink plate (10), and an IGBT temperature sensor is fixedly installed on the heat sink plate (10). The heating element (3) includes a PTC heating module (11). The heating surface of the PTC heating module (11) is tightly attached to one side of a high thermal conductivity ceramic substrate (26) through thermal grease. The other side of the high thermal conductivity ceramic substrate (26) is also attached to the wide side of the flat tube (24) through thermal grease. The flat tube (24) has multiple microchannels inside for coolant flow; The assembly of the PTC heating module (11), the high thermal conductivity ceramic substrate (26), and the flat tube (24) is completely covered by a reinforced sheet metal component (18) made of stainless steel.

6. The PTC liquid heater of claim 5, wherein, The reinforced sheet metal assembly (18) consists of a sheet metal body (19) and a sheet metal cover plate (20) forming a U-shaped clamping structure. The sheet metal body (19) is provided with a limiting plate (23), and the sheet metal cover plate (20) is provided with a strip hole that cooperates with the limiting plate (23). The limiting is achieved through staggered connection.

7. The PTC liquid heater of claim 5, wherein, The cavity is filled with sealant to a height of 2 / 3 to 3 / 4 of the cavity height.

8. The PTC liquid heater according to claim 5, characterized in that, A double waterproof sealing strip (16) is provided between the upper shell (1) and the lower shell (2).

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