Inverter water cooling system and optimal control method thereof

Abstract

The application discloses an inverter water cooling system and an optimal control method thereof, and the rotational speed of a fan and a water pump during operation of the inverter water cooling system is discretized, the relationship between the rotational speed of the fan and the water pump and the gear is established, the control rotational speed combination of the fan and the water pump at all gears is subjected to grid search, and the optimal solution of a target function under the gear combination of the fan and the water pump is obtained; the rotational speed range corresponding to the optimal solution of the gear combination of the fan and the water pump is taken as the search interval for further optimization and solution, the search step of the rotational speed of the fan and the water pump is shortened to 0.2 times, the rotational speed combination of the fan and the water pump is subjected to further grid search, and the optimal solution of the target function on the current search step of the rotational speed of the fan and the water pump is obtained; and when the termination condition is met, the optimal solution is output. The application can maintain the temperature of the inverter in a reasonable range while reducing the energy consumption of the water cooling system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inverter thermal management, and particularly relates to an inverter water cooling system and an optimal control method thereof. BACKGROUND

[0002] The motor controller is a core power electronic unit specific to a new energy vehicle, controls the motor to output a specified torque and rotating speed to drive the vehicle to run by receiving a vehicle running control instruction of a vehicle controller. The motor controller generates a large amount of heat during work, and after a period of use, the high temperature inside the controller can cause the internal components to age, affect the service life and have a certain impact on the vehicle running. In order to ensure the stability and reliability of the vehicle output power, a better motor controller cooling system needs to be developed to meet the vehicle working requirements.

[0003] The inverter liquid cooling system includes a water pump and a radiator. In actual cooling system control, only the cooling liquid flow is calibrated, and the cooling liquid temperature is not considered as a control variable. When the heat production rate exceeds a critical value, the cooling liquid can not control the inverter temperature within the target range, thereby causing the inverter to fail to dissipate heat. In addition, the traditional PID and logic condition judgment control method only controls the inverter temperature, without considering the power consumption of the cooling system actuator, thereby causing the cooling system to run at a high energy consumption. SUMMARY

[0004] In view of the deficiencies in the prior art, the application provides an optimal control method of an inverter water cooling system, which efficiently cools through a fan and a water pump, maintains the inverter temperature within a reasonable range, and reduces the energy consumption of the water cooling system.

[0005] The application achieves the above technical purposes through the following technical means.

[0006] An optimal control method of an inverter water cooling system comprises the following steps:

[0007] Obtain the motor control rotating speed, torque and cooling liquid inlet temperature under three-phase current control of the inverter, and predict the inverter temperature through an inverter water cooling system temperature prediction model;

[0008] Discretize the rotating speeds of the fan and the water pump during the operation of the inverter water cooling system, establish the relationship between the rotating speeds of the fan and the water pump and the gear positions, perform grid search on the control rotating speed combinations of all gear positions of the fan and the water pump, and obtain the optimal solution of the target function under the gear position combination of the fan and the water pump;

[0009] The speed range corresponding to the optimal solution of the fan and water pump gear combination is taken as the search interval for further optimization solution, and the search step of the fan and water pump speed is shortened to 0.2 times, and the target function is obtained by further grid search on the current fan and water pump speed search step; when the termination condition is met, the optimal solution is output.

[0010] Further, the target function is:

[0011]

[0012] Wherein: t0, t1 are the starting time and the ending time, respectively, T max (t) represents the real-time maximum temperature of the inverter, T0 represents the target control temperature of the inverter, △T max represents the theoretical maximum temperature difference between the maximum temperature of the inverter and the target temperature, P fan (t) and P pump (t) represent the power consumption of the fan and the water pump at a given speed, respectively, P0 represents the power factor, and a represents the weight factor of the balance temperature tracking and system energy consumption.

[0013] Further, the inverter circuit in the temperature prediction model is divided into upper and lower half bridges, the upper half bridge IGBT temperature node, the upper half bridge diode temperature node, the lower half bridge IGBT temperature node and the lower half bridge diode temperature node are connected with the substrate temperature node, and the substrate temperature node is connected with one end of the cooling plate temperature node through a heat conduction boundary, and the other end of the cooling plate temperature node is connected with a convection cooling boundary.

[0014] Still further, the heat conduction boundary is determined by the material properties and geometric dimensions of the adjacent nodes connected thereto.

[0015] Still further, the convection boundary condition = convection heat transfer coefficient * temperature difference * cooling area, wherein the convection heat transfer coefficient is obtained by looking up the corresponding cooling liquid flow table, the temperature difference specifically refers to the temperature difference between the cooling liquid inlet temperature and the cooling plate temperature node, and the cooling area is the inner surface area of the water channel.

[0016] Further, the termination condition includes that the speed search step is less than 10 rpm or the difference between the current optimization control target function solution result and the last step optimization control target function solution result is within 5%.

[0017] An inverter water cooling system implementing the optimal control method, comprising: a water channel arranged in a heat conduction plate, the water channel is distributed in an S shape, cooling liquid enters from the water inlet of the water channel, flows through the water channel to cool and take away the heat generated during operation of the inverter module, and then is discharged from the water outlet of the water channel.

[0018] In the above technical solution, the upper part of the heat conduction plate is an inverter module.

[0019] The present application has the following advantages:

[0020] (1) The temperature prediction model is used to predict the temperature of the inverter, thereby reducing the number of temperature sensors.

[0021] (2) The control method implemented by the present application includes real-time prediction of the temperature of the inverter, energy consumption of the fan and the water pump, and optimization control of the temperature control and system energy consumption, thereby improving the efficiency of the inverter cooling system and meeting the system temperature tracking requirements.

[0022] (3) The present application proposes a multi-grid search strategy, which greatly shortens the search space of the grid search algorithm by establishing the relationship between the fan and water pump speed and the gear position, and quickly obtains the optimal solution of the fan and water pump speed by shortening the speed search step, thereby avoiding the situation that the optimization solution falls into a local optimum.

[0023] (4) The present application is provided with a circulating water channel pipeline in the inverter, which forcibly cools each module inside the inverter, thereby effectively reducing the heat inside the inverter.

[0024] (5) The present application establishes an optimization control objective function of the inverter cooling system, uses the grid search to obtain the optimal solution of the objective function, and maintains the temperature of the inverter in a reasonable range. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic diagram of an inverter water cooling system of an embodiment of the present application;

[0026] Figure 2 is a three-dimensional schematic diagram of an inverter water cooling structure of an embodiment of the present application from one perspective;

[0027] Figure 3 is a schematic diagram of a water channel cross section inside an inverter of an embodiment of the present application;

[0028] Figure 4 is a schematic diagram of an inverter water cooling system and a control module of an embodiment of the present application;

[0029] Figure 5 is a schematic diagram of the control module shown in the embodiment Figure 3 of the present application;

[0030] Figure 6 is a structure schematic diagram of an inverter temperature prediction model of an embodiment of the present application;

[0031] Figure 7 is an optimal control flowchart of an inverter water cooling system of an embodiment of the present application.

[0032] In the figure: 1 - inverter switch and diode, 2 - solder layer, 3 - upper copper plate bonding, 4 - ceramic bonding, 5 - lower copper plate bonding, 6 - substrate solder layer, 7 - substrate, 8 - heat-conducting silicone grease, 9 - heat-conducting plate, 10 - water channel inlet, 11 - water channel outlet, 12 - electric water pump, 13 - radiator, 14 - fan, 15 - water channel, 1201 - electric water pump first port, 1202 - electric water pump second port, 1301 - radiator first port, 1302 - radiator second port, 100 - control module, 101 - interface A, 102 - interface B, 103 - coolant temperature signal, 104 - input interface, 105 - memory, 106 - processor, 107 - output interface, 108 - bus, 201 - upper half-bridge IGBT temperature node, 202 - upper half-bridge diode temperature node, 203 - lower half-bridge IGBT temperature node, 204 - lower half-bridge diode temperature node, 205 - substrate temperature node, 206 - cooling plate temperature node, 207 - heat conduction boundary, 208 - convection cooling boundary. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. For example, the finned radiator structure of the inverter can be reasonably replaced. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Various specific embodiments of the present application will be described below with reference to the accompanying drawings which form a part of the specification.

[0034] Figure 1 The figure is an inverter water cooling system of an embodiment of the present application, showing the connection relationship between the components in the inverter water cooling system and the components, which are described as follows: the electric water pump first port 1201 is in communication with the radiator second port 1302, the radiator first port 1301 and the water channel inlet 10 are in communication, and the water channel outlet 11 is in communication with the electric water pump second port 1202.

[0035] Figure 2 The figure shows the inverter water cooling structure of an embodiment of the present application. As shown in the figure, the inverter water cooling structure of the present application comprises a substrate 7, a heat-conducting plate 9, a water channel 15, an electric water pump 12, a radiator 13, a fan 14, a control module 100, an interface A 101, an interface B 102, a coolant temperature signal 103, an input interface 104, a memory 105, a processor 106, an output interface 107, a bus 108, an upper half-bridge IGBT temperature node 201, an upper half-bridge diode temperature node 202, a lower half-bridge IGBT temperature node 203, a lower half-bridge diode temperature node 204, a substrate temperature node 205, a cooling plate temperature node 206, a heat conduction boundary 207, and a convection cooling boundary 208. Figure 2As shown, the inverter water cooling system includes an inverter switch and diode 1, a solder layer 2, an upper copper plate bond 3, a ceramic bond 4, a lower copper plate bond 5, a substrate solder layer 6, a substrate 7, thermal grease 8, a heat-conducting plate 9, a water inlet 10, a water outlet 11, an electric water pump 12, a radiator 13, a fan 14, and a water channel 15. The inverter switch and diode 1 are connected to the upper copper plate bond 3 through the solder layer 2. The upper copper plate bond 3, ceramic bond 4, lower copper plate bond 5, substrate solder layer 6, substrate 7, thermal grease 8, and heat-conducting plate 9 are stacked together in sequence. The fan 14 is located at the radiator 13, and the water channel 15 is located inside the heat-conducting plate 9. The system achieves efficient heat dissipation of the inverter water cooling system through convection heat transfer and has the characteristics of a compact structure.

[0036] Figure 3 This is a schematic diagram of the internal water channel of an inverter according to an embodiment of this application. The water channel 15 is distributed in an S-shape in the 9 chamber of the heat-conducting plate. The coolant enters from the water channel inlet 10, flows through the water channel 15 to cool and carry away the heat generated by the inverter module (including inverter switch and diode 1, solder layer 2, upper copper plate bonding 3, ceramic bonding 4, lower copper plate bonding 5 and substrate solder layer 6) during operation, and then is discharged from the water channel outlet 11.

[0037] Figure 4 This is a schematic diagram of an inverter water cooling system and control module according to an embodiment of this application. The input interface 104 of the control module 100 receives the coolant temperature signal 103 (acquired by a temperature sensor installed at the water inlet 10). The output interface 107 of the control module 100 communicates with the electric water pump 12 and the fan 14 through interface A101 and interface B102 respectively. The control module 100 controls the coolant flow rate by controlling the electric water pump 12, controls the air cooling flow rate of the radiator 13 by controlling the fan 14, and obtains the inverter coolant inlet temperature by receiving the coolant temperature signal 103.

[0038] Figure 5 This is the embodiment. Figure 4 The diagram shows a schematic internal structure of the control module. Figure 4 As shown, the control module 100 of the inverter cooling system includes a bus 108, an input interface 104, a memory 105, a processor 106, and an output interface 107. Specifically, the memory 105 stores programs, instructions, and data, while the processor 106 reads programs, instructions, and data from the memory 105 and can write data to the memory 105; the processor 106 reads programs and instructions, and exchanges signals through the input interface 104 and the output interface 107. Figure 5As shown, the control module 100 receives the coolant temperature signal 103 through the input interface 104, and is in communication connection with the electric water pump 12 and the fan 14 through the interface A 101 and the interface B 102. Specifically, the control device 100 can accept the operation request of the inverter water cooling system or the signal of other components through the input interface 104, and send control signals to each controlled component through the output interface 107, so as to realize the control instruction.

[0039] Figure 7 The optimal control flow chart of the inverter water cooling system which is an embodiment of the present application adopts a multi-grid search strategy, establishes the relationship between the fan 14 and the electric water pump 12 speed and the gear, greatly shortens the search space of the grid search algorithm, and through the shortening of the speed search step, the optimal solution of the fan and the electric water pump speed can be quickly obtained, and the situation that the optimization solution falls into local optimum is avoided; the control flow chart includes the following steps:

[0040] Step (1), constructing an inverter water cooling system temperature prediction model

[0041] Figure 6 The structure diagram of the inverter water cooling system temperature prediction model, the inverter temperature prediction model considers the IGBT and diode heat generation under the given working condition of the inverter three-phase current control; the inverter temperature prediction model calculates the coolant flow according to the electric water pump 12 speed (known value) to determine the inverter convection boundary condition; the inverter temperature prediction model performs mathematical solution (solution process is prior art) on the heat conduction boundary and convection boundary condition of the whole inverter through the thermal model, so as to obtain the IGBT and diode temperature of the inverter.

[0042] In the temperature prediction model, the inverter circuit is divided into upper and lower half bridges and A, B and C three phases. Taking the A phase as an example, the upper half bridge IGBT temperature node 201 and the upper half bridge diode temperature node 202 are T IGBT1 , T Diode1 , the lower half bridge IGBT temperature node 203 and the lower half bridge diode temperature node 204 are T IGBT2 , T Diode2 ; the substrate temperature node 205 T BaseA is connected with the above temperature nodes and the cooling plate temperature node 206 T Plate through the heat conduction boundary 207, and the cooling plate temperature node 206 T PlateThe other end is connected with a convection cooling boundary 208. The thermal conduction boundary 207 is determined by the material properties and geometric dimensions (including cross-sectional area and centroid distance) of the adjacent nodes connected therewith; the heat generation of the IGBT and diode temperature nodes is determined through the inverter working condition (corresponding to the motor control speed, torque) and the corresponding data lookup table; the convection boundary condition 208 = convection heat transfer coefficient * temperature difference * cooling area, wherein the convection heat transfer coefficient is obtained through the corresponding cooling liquid flow lookup table, the temperature difference specifically refers to the temperature difference between the cooling liquid inlet temperature and the cooling plate temperature node 206T Plate .

[0043] Step (2), the motor control speed, torque and cooling liquid inlet temperature under the three-phase current control of the inverter are obtained, and the temperature of the inverter (i.e. the temperature of the IGBT and diode) is predicted through the inverter water cooling system temperature prediction model.

[0044] Step (3), an optimization control objective function of the inverter water cooling system is established, and the optimization control objective function in the time period t0 to t1 is defined as:

[0045]

[0046] Wherein, T max (t) represents the real-time maximum temperature of the inverter (i.e. the temperature predicted in step (2)), T0 represents the target control temperature of the inverter, △T max represents the theoretical maximum temperature difference between the maximum temperature of the inverter and the target temperature, P fan (t) and P pump (t) respectively represent the power consumption of the fan and the water pump under the given speed (obtained by looking up the table), P0 represents the power factor (determined by the sum of the maximum power of the fan and the water pump), and α represents the weight factor of balancing temperature tracking and system energy consumption, wherein the weight factor α is obtained through offline inverter water cooling system simulation evaluation, and the Pareto optimal solution under multi-objective optimization of the inverter water cooling system is obtained.

[0047] Step (4), the speed of the fan and the water pump during the operation of the inverter water cooling system is discretized, and the relationship between the speed of the fan and the water pump and the gear position (as shown in Table 1 and Table 2) is established, and the control speed combination of all gear positions of the fan and the water pump (according to the gear positions shown in Table 1 and Table 2, there are 45 combinations) is searched (the process is prior art), and the optimal solution of the objective function under the gear combination of the fan and the water pump is obtained;

[0048] Table 1 Discretization of water pump speed

[0049]

[0050]

[0051] Table 2 fan speed discretization

[0052]

[0053] Step (5), the speed range corresponding to the optimal solution of the fan and water pump gear combination is taken as the search interval for further optimization solution, the fan and water pump speed search step is shortened to 0.2 times (when shortened for the first time, the speed search step is the search step in step (4)), the fan and water pump speed combination is further subjected to grid search, and the optimal solution of the target function on the current fan and water pump speed search step is obtained;

[0054] Step (6), it is judged whether the termination condition of the optimization search algorithm is met, if not, step (5) is returned, if the termination condition of the optimization search algorithm is met, the algorithm is terminated, and the optimal solution is output; wherein the termination condition includes that the speed search step is <10 rpm or the difference between the optimization control target function solution result and the optimization control target function solution result of the last step is within 5%.

[0055] The embodiments are preferred embodiments of the present application, but the present application is not limited to the above embodiments, and any obvious improvement, replacement or modification made by those skilled in the art without departing from the essential content of the present application shall fall within the protection scope of the present application.

Claims

1. An optimal control method of an inverter water cooling system, characterized by: obtaining the motor control speed, torque and cooling liquid inlet temperature under the control of the three-phase current of the inverter, and predicting the inverter temperature through an inverter water cooling system temperature prediction model; discretizing the speeds of the fan and water pump during the operation of the inverter water cooling system, establishing the relationship between the speeds of the fan and water pump and the gear positions, and performing grid search on the control speed combinations of all gear positions of the fan and water pump to obtain the optimal solution of the target function under the gear position combination of the fan and water pump; taking the speed range corresponding to the optimal solution of the gear position combination of the fan and water pump as the search interval for further optimization and solution, shortening the search step of the fan and water pump speed to 0.2 times, and further performing grid search on the fan and water pump speed combination to obtain the optimal solution of the target function under the current fan and water pump speed search step; when the termination condition is met, the optimal solution is output; the termination condition includes that the speed search step is less than 10 rpm or the difference between the optimization control target function solution result and the optimization control target function solution result of the previous step is within 5%; in the temperature prediction model, the inverter circuit is divided into upper and lower half bridges, the upper half bridge IGBT temperature node, the upper half bridge diode temperature node, the lower half bridge IGBT temperature node and the lower half bridge diode temperature node are connected with the substrate temperature node, the substrate temperature node is connected with one end of the cooling plate temperature node through a heat conduction boundary, and the other end of the cooling plate temperature node is connected with a convection cooling boundary; the target function is: wherein: t0, t1 are the start and end time, respectively, T max (t) represents the real-time maximum temperature of the inverter, T0 represents the target control temperature of the inverter, ΔT max represents the theoretical maximum temperature difference between the maximum temperature of the inverter and the target temperature, P fan (t) and P pump (t) represent the power consumption of the fan and water pump at a given speed, respectively, P0 represents the power factor, and α represents the weight factor of balancing temperature tracking and system energy consumption.

2. The optimal control method of claim 1, wherein, the heat conduction boundary is determined by the material properties and geometric dimensions of the adjacent nodes connected therewith.

3. The optimal control method of claim 1, wherein, the convection boundary condition = convection heat transfer coefficient * temperature difference * cooling area, wherein the convection heat transfer coefficient is obtained by looking up the corresponding cooling liquid flow table, the temperature difference specifically refers to the temperature difference between the cooling liquid inlet temperature and the cooling plate temperature node, and the cooling area is the inner surface area of the water channel.

4. An inverter water cooling system implementing the optimal control method of any one of claims 1-3, characterized in that, including: a water channel arranged in the heat conduction plate, the water channel is distributed in an S shape, the cooling liquid enters from the water channel inlet, flows through the water channel to cool and carry away the heat generated during the operation of the inverter module, and then is discharged from the water channel outlet.

5. The water-cooling system for an inverter according to claim 4, wherein the upper part of the heat conduction plate is the inverter module.

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