Capacitance temperature determination method and apparatus, electronic device, and storage medium

Abstract

The embodiment of the application provides a capacitor temperature determination method and device, electronic equipment and storage medium, the method comprises the steps that the electrical signal parameter of the circuit system where the capacitor is located is acquired; the capacitor power loss of the capacitor is determined based on the electrical signal parameter; the capacitor core temperature of the capacitor is determined based on a layered heat conduction equivalent model and the capacitor power loss, wherein the layered heat conduction equivalent model is used to characterize the equivalent heat resistance and heat capacity model obtained by structurally layering the heat conduction process of the capacitor. The application solves the technical problem that the accuracy of monitoring the capacitor core temperature is low in the related art.

Description

Technical Field

[0001] This application relates to the field of vehicle electrical technology, and more specifically, to a method, apparatus, electronic device, and storage medium for determining capacitor temperature. Background Technology

[0002] Capacitors are passive devices in circuit systems that maintain voltage stability, absorb high-frequency ripple current, and suppress harmonic interference. Temperature is a crucial factor determining the lifespan and reliability of a capacitor. Currently, capacitor temperature management typically involves installing temperature sensors on the capacitor casing, increasing system cost and wiring complexity. Furthermore, these sensors are prone to failure under harsh conditions such as vibration and high humidity. Due to the significant thermal resistance between the capacitor core and the casing, the casing temperature is much lower than the actual core temperature, resulting in a severely delayed measurement response and low accuracy in monitoring the capacitor core temperature.

[0003] There is currently no good solution to the above problems. Summary of the Invention

[0004] This application provides a method, apparatus, electronic device, and storage medium for determining capacitor temperature, in order to at least solve the technical problem of low accuracy in monitoring capacitor core temperature in related technologies.

[0005] According to one aspect of the embodiments of this application, a method for determining the temperature of a capacitor is provided, comprising: acquiring electrical signal parameters of the circuit system in which the capacitor is located; determining the capacitor power loss of the capacitor based on the electrical signal parameters; and determining the capacitor core temperature of the capacitor based on a layered thermal conduction equivalent model and the capacitor power loss, wherein the layered thermal conduction equivalent model is used to characterize the equivalent thermal resistance and thermal capacity model obtained by structurally layering the thermal conduction process of the capacitor.

[0006] In this embodiment of the application, when the circuit system is an electronic control unit and the capacitor is a bus capacitor, the capacitor power loss is determined based on the electrical signal parameters, including: determining the phase current parameters and power switch state parameters of the electronic control unit based on the electrical signal parameters; and determining the capacitor power loss based on the phase current parameters and power switch state parameters.

[0007] In this embodiment of the application, determining the capacitor power loss based on phase current parameters and power switch state parameters includes: determining the effective value of the ripple current based on the phase current parameters and power switch state parameters, wherein the effective value of the ripple current is used to represent the effective value of the ripple current provided by the capacitor; and determining the capacitor power loss based on the effective value of the ripple current, the first equivalent series resistance value corresponding to the capacitor, and the dielectric loss tangent value.

[0008] In this embodiment of the application, determining the effective value of the ripple current based on phase current parameters and power switch status parameters includes: determining the inverter DC-side current based on phase current parameters and power switch status parameters, wherein the inverter DC-side current is used to represent the DC current value flowing into the inverter DC side of the electronic control unit; and determining the effective value of the ripple current based on the inverter DC-side current and the battery output current, wherein the battery output current is used to represent the DC current value output by the battery in the electronic control unit.

[0009] In this embodiment of the application, determining the effective value of the ripple current based on the inverter DC-side current and the battery output current includes: determining the capacitor ripple current based on the difference between the inverter DC-side current and the battery output current, wherein the capacitor ripple current is used to represent the ripple current value provided by the capacitor; and calculating the root mean square value of the capacitor ripple current within the target control cycle to obtain the effective value of the ripple current.

[0010] In this embodiment of the application, the method further includes: obtaining the historical temperature of the capacitor core and the characteristic frequency of the ripple current, wherein the historical temperature of the capacitor core is used to represent the temperature of the capacitor core determined by at least one historical control cycle, and the characteristic frequency of the ripple current is used to represent the frequency component corresponding to the ripple current; determining a first equivalent series resistance value based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the resistance temperature-frequency mapping relationship, wherein the resistance temperature-frequency mapping relationship is used to represent the mapping relationship of the fitted resistance value with the two-dimensional parameters of temperature and frequency; and determining the dielectric loss tangent value based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the loss temperature-frequency mapping relationship, wherein the loss temperature-frequency mapping relationship is used to represent the mapping relationship of the fitted loss tangent with the two-dimensional parameters of temperature and frequency.

[0011] In this embodiment, the layered heat conduction equivalent model includes at least two heat conduction equivalent layers: a core-to-inner shell heat conduction equivalent layer, an inner shell-to-outer shell heat conduction equivalent layer, an outer shell-to-heat sink heat conduction equivalent layer, and a heat sink-to-ambient heat conduction equivalent layer. Based on the layered heat conduction equivalent model and capacitor power loss, the capacitor core temperature is determined, including: determining the step response parameters of the layered heat conduction equivalent model in the time domain based on the capacitor power loss and the thermal resistance and thermal capacitance parameters corresponding to each heat conduction equivalent layer; and determining the capacitor core temperature based on the step response parameters.

[0012] In this embodiment, determining the capacitor core temperature based on step response parameters includes: determining the temperature rise state vector corresponding to each thermal conduction equivalent layer based on step response parameters, state transition matrix, and input gain matrix, wherein the state transition matrix is ​​determined based on thermal resistance parameters and thermal capacity parameters, the thermal state evolution characteristic matrix, the input gain matrix is ​​determined based on thermal resistance parameters and thermal capacity parameters, and the weighted contribution matrix of power loss to temperature rise is used; and determining the capacitor core temperature based on the temperature rise state vector.

[0013] In this embodiment of the application, determining the capacitor core temperature based on the temperature rise state vector includes: determining the capacitor core temperature based on the temperature rise state vector and the ambient temperature of the circuit system.

[0014] In this embodiment, the target conductive equivalent layer includes a heat conduction equivalent layer from the shell to the heat sink and a heat conduction equivalent layer from the heat sink to the environment. When the layered heat conduction equivalent model includes the target conductive equivalent layer and the heat sink used in the circuit system is a liquid-cooled heat sink, the method further includes: adjusting the initial thermal resistance parameter corresponding to the target conductive equivalent layer based on the coolant flow rate of the liquid-cooled heat sink to obtain the thermal resistance parameter corresponding to the target conductive equivalent layer.

[0015] In this embodiment of the application, the method further includes: obtaining the aging coefficient of the capacitor, wherein the aging coefficient is used to characterize the degree of aging of the capacitor; adjusting the capacitor power loss based on the aging coefficient to obtain the adjusted capacitor power loss; adjusting the thermal resistance parameter and thermal capacity parameter corresponding to each heat conduction equivalent layer in the layered heat conduction equivalent model based on the aging coefficient to obtain the adjusted layered heat conduction equivalent model; and determining the capacitor core temperature based on the adjusted capacitor power loss and the adjusted layered heat conduction equivalent model.

[0016] In this embodiment of the application, when the circuit system is an electronic control unit and the capacitor is a bus capacitor, obtaining the aging coefficient of the capacitor includes: in response to receiving a calibration command, injecting a common-mode voltage signal of a preset amplitude into the inverter in the electronic control unit, and collecting the ripple component voltage parameter and ripple component current parameter corresponding to the target ripple current generated on the DC bus; determining the second equivalent series resistance value based on the ripple component voltage parameter and ripple component current parameter; and determining the aging coefficient based on the second equivalent series resistance value and the first equivalent series resistance value.

[0017] According to another aspect of the embodiments of this application, a device for determining capacitor temperature is also provided, comprising: an acquisition module for acquiring electrical signal parameters of the circuit system in which the capacitor is located; a first determination module for determining the capacitor power loss of the capacitor based on the electrical signal parameters; and a second determination module for determining the capacitor core temperature of the capacitor based on a layered thermal conduction equivalent model and the capacitor power loss, wherein the layered thermal conduction equivalent model is used to characterize the equivalent thermal resistance and thermal capacity model obtained by structurally layering the thermal conduction process of the capacitor.

[0018] In this embodiment of the application, when the circuit system is an electronic control unit and the capacitor is a bus capacitor, the first determining module is further configured to determine the phase current parameters and power switch state parameters of the electronic control unit based on the electrical signal parameters; and determine the capacitor power loss based on the phase current parameters and power switch state parameters.

[0019] In this embodiment of the application, the first determining module is further configured to determine the effective value of the ripple current based on the phase current parameters and the power switch state parameters, wherein the effective value of the ripple current is used to represent the effective value of the ripple current provided by the capacitor; and to determine the capacitor power loss based on the effective value of the ripple current, the first equivalent series resistance value corresponding to the capacitor, and the dielectric loss tangent value.

[0020] In this embodiment of the application, the first determining module is further configured to determine the inverter DC-side current based on the phase current parameters and power switch state parameters, wherein the inverter DC-side current is used to represent the DC current value flowing into the inverter DC side of the electronic control unit; and to determine the effective value of the ripple current based on the inverter DC-side current and the battery output current, wherein the battery output current is used to represent the DC current value output by the battery in the electronic control unit.

[0021] In this embodiment of the application, the first determining module is further configured to determine the capacitor ripple current based on the difference between the inverter DC side current and the battery output current, wherein the capacitor ripple current is used to represent the ripple current value provided by the capacitor; and within the target control cycle, the root mean square value of the capacitor ripple current is calculated to obtain the effective value of the ripple current.

[0022] In this embodiment, the first determining module is further configured to acquire the historical temperature of the capacitor core and the characteristic frequency of the ripple current, wherein the historical temperature of the capacitor core is used to represent the temperature of the capacitor core determined in at least one historical control cycle, and the characteristic frequency of the ripple current is used to represent the frequency component corresponding to the ripple current; based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the temperature-frequency mapping relationship of the resistance, a first equivalent series resistance value is determined, wherein the temperature-frequency mapping relationship of the resistance is used to represent the mapping relationship of the fitted resistance value with the two-dimensional parameters of temperature and frequency; based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the temperature-frequency mapping relationship of the loss, a dielectric loss tangent value is determined, wherein the temperature-frequency mapping relationship of the loss is used to represent the mapping relationship of the fitted loss tangent with the two-dimensional parameters of temperature and frequency.

[0023] In this embodiment, the layered heat conduction equivalent model includes at least two heat conduction equivalent layers: a core-to-inner shell heat conduction equivalent layer, an inner shell-to-outer shell heat conduction equivalent layer, an outer shell-to-heat sink heat conduction equivalent layer, and a heat sink-to-ambient heat conduction equivalent layer. The second determining module is further configured to determine the step response parameters of the layered heat conduction equivalent model in the time domain based on the capacitor power loss and the thermal resistance and thermal capacity parameters corresponding to each heat conduction equivalent layer; and to determine the capacitor core temperature based on the step response parameters.

[0024] In this embodiment of the application, the second determining module is further configured to determine the temperature rise state vector corresponding to each heat conduction equivalent layer based on the step response parameters, the state transition matrix, and the input gain matrix, wherein the state transition matrix is ​​determined based on the thermal resistance parameters and the thermal capacity parameters, the thermal state evolution characteristic matrix, the input gain matrix is ​​determined based on the thermal resistance parameters and the thermal capacity parameters, and the weighted contribution matrix of power loss to temperature rise is a matrix; and the capacitor core temperature is determined based on the temperature rise state vector.

[0025] In this embodiment of the application, the second determining module is further used to determine the capacitor core temperature based on the temperature rise state vector and the ambient temperature of the circuit system.

[0026] In this embodiment, the target conductive equivalent layer includes a heat conduction equivalent layer from the shell to the heat sink and a heat conduction equivalent layer from the heat sink to the environment. When the layered heat conduction equivalent model includes the target conductive equivalent layer and the heat sink used in the circuit system is a liquid-cooled heat sink, the second determining module is further used to adjust the initial thermal resistance parameter corresponding to the target conductive equivalent layer based on the coolant flow rate of the liquid-cooled heat sink to obtain the thermal resistance parameter corresponding to the target conductive equivalent layer.

[0027] In this embodiment, the second determining module is further configured to obtain the aging coefficient of the capacitor, wherein the aging coefficient is used to characterize the degree of aging of the capacitor; adjust the capacitor power loss based on the aging coefficient to obtain the adjusted capacitor power loss; adjust the thermal resistance parameter and thermal capacity parameter corresponding to each heat conduction equivalent layer in the layered heat conduction equivalent model based on the aging coefficient to obtain the adjusted layered heat conduction equivalent model; and determine the capacitor core temperature based on the adjusted capacitor power loss and the adjusted layered heat conduction equivalent model.

[0028] In this embodiment of the application, when the circuit system is an electronic control unit and the capacitor is a bus capacitor, the second determining module is further configured to, in response to receiving a calibration command, inject a common-mode voltage signal of a preset amplitude into the inverter in the electronic control unit, and collect the ripple component voltage parameters and ripple component current parameters corresponding to the target ripple current generated on the DC bus; determine the second equivalent series resistance value based on the ripple component voltage parameters and ripple component current parameters; and determine the aging coefficient based on the second equivalent series resistance value and the first equivalent series resistance value.

[0029] In this embodiment, firstly, the electrical signal parameters of the circuit system containing the capacitor are obtained; then, based on the electrical signal parameters, the capacitor power loss is determined; finally, based on the layered thermal conduction equivalent model and the capacitor power loss, the capacitor core temperature is determined. This application achieves accurate mapping of the entire heat transfer process from heat source excitation to heat transfer by obtaining the electrical signal parameters of the circuit system to accurately calculate the capacitor power loss and determining the capacitor core temperature based on the layered thermal conduction equivalent model, thus improving monitoring accuracy. The use of a layered equivalent model for the heat transfer process accurately characterizes multi-level thermal resistance and thermal capacity effects, accurately reflecting the dynamic heat transfer patterns and actual thermal hysteresis characteristics inside and outside the capacitor. This effectively eliminates estimation errors under dynamic operating conditions caused by model simplification, as well as deviations between the outer shell temperature and the core temperature caused by neglecting the internal thermal resistance distribution. This embodiment can restore the true temperature state of the capacitor hotspot in real time and dynamically, thereby solving the technical problem of low accuracy in monitoring the capacitor core temperature in related technologies. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1 This is a flowchart of a method for determining capacitor temperature according to an embodiment of this application;

[0032] Figure 2 This is a schematic diagram of the technical framework of a capacitor temperature determination method according to an embodiment of this application;

[0033] Figure 3 This is a schematic diagram of a layered heat conduction equivalent model according to an embodiment of this application;

[0034] Figure 4 This is a schematic diagram of a capacitor power loss determination process according to an embodiment of this application;

[0035] Figure 5 This is a schematic diagram of an optional capacitor temperature determination process according to an embodiment of this application;

[0036] Figure 6 This is a schematic diagram of a capacitor temperature determination device according to an embodiment of this application. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] According to an embodiment of this application, an embodiment of a method for determining capacitor temperature is provided. The steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be performed in a different order than that shown here.

[0040] This embodiment provides a method for determining the temperature of a capacitor. Figure 1 This is a flowchart of a method for determining capacitor temperature according to an embodiment of this application, as shown below. Figure 1 As shown, the process includes the following steps:

[0041] Step S102: Obtain the electrical signal parameters of the circuit system where the capacitor is located.

[0042] The aforementioned electrical signal parameters may refer to electrical measurement values ​​or reconstructed values ​​required for calculating capacitor power loss.

[0043] As an optional implementation, electrical sensors already configured in the circuit system can be used, or additional electrical sensors can be configured in the circuit system to collect electrical signal parameters. During this process, voltage sensor data can be read to obtain voltage signals, and current signals output by current sensors can be read. This process relies on the measurement of physical sensors, and analog signals are converted into digital signals by an analog-to-digital converter for processing by the main control unit.

[0044] By setting up the above parameters, the electrical signal parameters of the circuit system where the capacitor is located are obtained, ensuring the comprehensiveness and real-time nature of the temperature estimation at the input source. This provides a data foundation for subsequent high-precision core temperature estimation and improves the robustness of the overall thermal management strategy.

[0045] Step S104: Determine the capacitor power loss based on the electrical signal parameters.

[0046] The aforementioned capacitor power loss can refer to the heat loss power generated by the capacitor during operation due to its own physical characteristics.

[0047] As an optional implementation, the capacitor power loss can be directly calculated based on the reconstructed RMS value of the ripple current and the electrical parameters obtained through dynamic lookup tables. Specifically, the RMS value of the ripple current can be calculated within one control cycle using the acquired capacitor ripple current signal to obtain the RMS value of the ripple current. Then, based on the historical temperature of the capacitor core estimated at the previous moment and the characteristic frequency of the current ripple current, bilinear interpolation is performed in a two-dimensional lookup table pre-stored in the controller's read-only memory to obtain the equivalent series resistance and dielectric loss tangent under the current operating condition. Finally, the Joule heat loss is obtained based on the RMS value of the ripple current and the equivalent series resistance. The dielectric loss is then calculated by combining the capacitor value, voltage frequency, and dielectric loss tangent. The Joule heat loss and dielectric loss are then added together to obtain the capacitor power loss. This process utilizes real-time electrical parameters and dynamic lookup tables to accurately quantify energy loss under different operating conditions.

[0048] As an alternative implementation, the ripple current and losses can be indirectly derived and calculated using the current difference method. Specifically, the instantaneous value of the ripple current can be obtained. Then, the instantaneous value of the ripple current within a time window is squared, integrated, and square-rooted to obtain the effective value of the ripple current. Subsequently, a simplified linear temperature coefficient model is used to linearly correct the initial equivalent series resistance value based on the currently estimated temperature, obtaining the equivalent series resistance value at the current temperature. Finally, based on the effective value of the ripple current and the equivalent series resistance value, the capacitor power loss is calculated. This method simplifies the calculation of dielectric losses, focuses on quickly estimating heat generation through current difference, and is suitable for scenarios with limited computing power or requiring rapid response.

[0049] With the above settings, the capacitor power loss can be determined based on electrical signal parameters, and accurate heat source input can be obtained in real time without additional hardware. This provides precise excitation for subsequent thermal models, thereby improving the real-time performance and accuracy of capacitor core temperature estimation, reducing system costs, and enhancing the reliability of thermal management.

[0050] Step S106: Determine the capacitor core temperature based on the layered heat conduction equivalent model and capacitor power loss.

[0051] Among them, the layered thermal conduction equivalent model is used to characterize the equivalent thermal resistance and thermal capacity model obtained by structurally layering the thermal conduction process of the capacitor.

[0052] The aforementioned hierarchical heat conduction equivalent model can refer to a higher-order dynamic thermal network model. Here, "higher-order" means that the model has more state variables and more dynamic poles in its mathematical structure, thus enabling a more precise description of the spatial distribution and time lag characteristics of the heat conduction process. The hierarchical heat conduction equivalent model is used to simulate the complex heat conduction process inside a capacitor. It divides the capacitor's heat conduction process into layers based on its physical structure or thermal resistance path, dividing it into at least two series-connected thermal resistance-thermal capacity links. The hierarchical heat conduction equivalent model describes the evolution of the temperature rise state vector in the time domain through state-space equations.

[0053] The aforementioned capacitor core temperature can refer to the temperature of the hot spot inside the capacitor, i.e., the actual operating temperature of the capacitor core. In this application, the capacitor core temperature is an estimated value calculated using the aforementioned layered heat conduction equivalent model, combined with the ambient temperature, real-time calculated capacitor power loss, and the temperature rise state vector of each node within the layered heat conduction equivalent model.

[0054] As an optional implementation, a layered heat conduction equivalent model in the continuous domain can be used for analytical solutions or numerical integration calculations. This model divides the internal heat conduction path of the capacitor into multiple series-connected thermal resistance-capacitance links: core to inner shell, inner shell to outer shell, outer shell to heat sink, and heat sink to the environment. Using the capacitor's power loss as the input source, a system of differential equations is constructed using the thermal resistance and capacity parameters of each layer. During calculation, the step response of this system of equations is solved, which is the superposition of exponential functions of temperature rise over time, expressed as the sum of the temperature rise contributions of each layer. By introducing a time constant, the layered heat conduction equivalent model can accurately describe the dynamic hysteresis process of heat diffusion from the point of generation, i.e., the core, to the environment. This method theoretically provides high physical fidelity, can meticulously characterize the differences in thermal inertia between different material layers inside the capacitor, and is suitable for simulation or offline analysis scenarios requiring high precision and sufficient computing power, ensuring accurate capture of transient thermal shocks.

[0055] As an alternative implementation, the continuous thermal network model can be discretized into state-space equations for real-time iterative solution in a microprocessor. Specifically, the hierarchical heat conduction model can be transformed into state equations in the discrete-time domain, with the state variables being the temperature rise vectors of each thermal node. The state transition matrix and input gain matrix can be pre-calculated based on thermal resistance and thermal capacity parameters. In each control cycle, the temperature rise state vector from the previous moment is multiplied by the state transition matrix and then added to the product of the current power loss and the input gain matrix to obtain the current temperature rise state vector. Finally, the node temperature rise corresponding to the capacitor core is extracted from this temperature rise state vector, and the capacitor core temperature is obtained by adding the ambient temperature. This method avoids the complex real-time solution of differential equations, achieves rapid iteration through simpler matrix multiplication, significantly reduces computational complexity, and is suitable for real-time operation in resource-constrained automotive-grade vehicle control units, ensuring the real-time and continuous nature of the estimation.

[0056] The above settings achieve both compatibility and real-time performance. This design ensures the theoretical accuracy of the solution while also taking into account the real-time requirements of engineering implementation. It enables flexible adaptation to controller platforms with different computing power levels, thereby enhancing practical application value and wide applicability.

[0057] In this embodiment, firstly, the electrical signal parameters of the circuit system containing the capacitor are obtained; then, based on the electrical signal parameters, the capacitor power loss is determined; finally, based on the layered thermal conduction equivalent model and the capacitor power loss, the capacitor core temperature is determined. This application achieves accurate mapping of the entire heat transfer process from heat source excitation to heat transfer by obtaining the electrical signal parameters of the circuit system to accurately calculate the capacitor power loss and determining the capacitor core temperature based on the layered thermal conduction equivalent model, thus improving monitoring accuracy. The use of a layered equivalent model for the heat transfer process accurately characterizes multi-level thermal resistance and thermal capacity effects, accurately reflecting the dynamic heat transfer patterns and actual thermal hysteresis characteristics inside and outside the capacitor. This effectively eliminates estimation errors under dynamic operating conditions caused by model simplification, as well as deviations between the outer shell temperature and the core temperature caused by neglecting the internal thermal resistance distribution. This embodiment can restore the true temperature state of the capacitor hotspot in real time and dynamically, thereby solving the technical problem of low accuracy in monitoring the capacitor core temperature in related technologies.

[0058] In this embodiment of the application, when the circuit system is an electronic control unit and the capacitor is a bus capacitor, the capacitor power loss is determined based on the electrical signal parameters, including: determining the phase current parameters and power switch state parameters of the electronic control unit based on the electrical signal parameters; and determining the capacitor power loss based on the phase current parameters and power switch state parameters.

[0059] The aforementioned electronic control unit (ECU) can refer to the drive motor controller of a new energy vehicle, which can be an inverter assembly or a power electronic controller. The ECU is a crucial component connecting the high-voltage battery and the drive motor, internally containing a DC bus, power switching devices, drive circuitry, and a control motherboard. The ECU is responsible for receiving DC power from the battery and converting it into AC power to drive the motor. It also has the function of monitoring and managing the temperature of the bus capacitors.

[0060] The aforementioned bus capacitors can refer to the support capacitors installed at both ends of the DC bus of the electronic control unit. The main functions of the bus capacitors are: to smooth the DC bus voltage and reduce voltage fluctuations; to absorb the high-frequency ripple current generated by the high-frequency switching action of power switching devices and the commutation of motor windings; and to filter out high-frequency harmonic interference on the DC side, protecting the battery and power devices.

[0061] The aforementioned phase current parameters can refer to the real-time measured or reconstructed values ​​of the three-phase current on the output side of the inverter in the electronic control unit (ECU). These phase current parameters are raw data collected by current sensors in the ECU, or equivalent current values ​​derived from other electrical quantities. When calculating capacitor power losses, the phase current parameters are used to reconstruct the DC-side current in conjunction with the switching state, thereby separating the ripple current flowing through the bus capacitor.

[0062] The aforementioned power switch status parameters refer to the on / off logic states of the power switching devices in each phase of the inverter. These can be represented by switching functions, where each function can take a value of 0 or 1. For example, 1 represents the upper switch being on and the lower switch being off, while 0 represents the upper switch being off and the lower switch being on. The power switch status parameters reflect the current pulse width modulation state of the inverter and serve as parameters for calculating the current flowing into the DC side of the inverter. Based on these parameters, it is possible to determine which phases of current are flowing through the DC bus, thereby accurately calculating the effective value of the ripple current borne by the bus capacitor.

[0063] As an optional implementation, the ripple current can be indirectly obtained by reconstructing and subtracting the DC-side current. Specifically, the phase current parameters of the three-phase inverter in the control unit, as well as the corresponding power switch status parameters, can be acquired in real time. The switch status parameters represent the on / off logic of the power devices in each bridge arm. Based on the phase current parameters and power switch status parameters, the instantaneous current waveform flowing into the DC side of the inverter can be reconstructed. Subsequently, the reconstructed DC-side current is compared with the battery output current directly acquired by the DC bus sensor in real time to obtain the ripple current flowing through the bus capacitor. Finally, the ripple current is calculated within one control cycle to obtain the effective value of the ripple current, and combined with the preset equivalent series resistance value, the capacitor power loss caused by Joule heating is calculated.

[0064] As an alternative implementation, losses can be calculated directly using phase current and switching states without explicitly separating the battery current. Similarly, phase current parameters and power switch state parameters are obtained, assuming the battery current is relatively smooth or already known through other means; the focus is on calculating the AC component loss borne by the capacitor. Based on the phase current parameters and power switch state parameters, the sequence of current pulses flowing through the capacitor in each switching cycle is directly calculated. The root mean square value of this current pulse within one switching cycle, i.e., the effective value of the ripple current, is directly calculated using analytical or numerical integration methods. In this process, a switching timing model can be introduced to consider the impact of dead time on the current path, thereby more accurately reconstructing the capacitor current waveform. Subsequently, the effective value is squared and multiplied by the equivalent series resistance under the current operating condition to directly obtain the Joule thermal power loss of the capacitor. This method simplifies the signal processing chain, focuses on direct mathematical mapping based on the switching topology, and is suitable for scenarios with high real-time computational requirements and stable switching frequencies.

[0065] By utilizing the existing hardware resources of the electronic control unit (ECU), namely the phase current sensor and pulse width modulation controller, the need for an additional dedicated DC-side high-frequency current sensor is eliminated, thereby reducing system cost and wiring complexity. Through switch state reconstruction, the details of ripple current caused by high-frequency power switching can be accurately captured, allowing for high-precision estimation of the actual heat generation of the capacitor even without direct measurement of the DC-side high-frequency current. This method improves the compactness of system integration, enhances the feasibility and economy of the solution, and ensures the accuracy of capacitor heat loss calculation under dynamic operating conditions, providing a reliable data foundation for subsequent temperature estimation.

[0066] In this embodiment of the application, determining the capacitor power loss based on phase current parameters and power switch state parameters includes: determining the effective value of the ripple current based on the phase current parameters and power switch state parameters, wherein the effective value of the ripple current is used to represent the effective value of the ripple current provided by the capacitor; and determining the capacitor power loss based on the effective value of the ripple current, the first equivalent series resistance value corresponding to the capacitor, and the dielectric loss tangent value.

[0067] The aforementioned RMS ripple current refers to the effective value of the AC current flowing through the bus capacitor. The RMS ripple current can be obtained by subtracting the relatively smoothed battery output DC current from the inverter DC-side current, and then calculating the root mean square value within a target control cycle. The RMS ripple current characterizes the actual AC current load borne by the capacitor during operation and serves as a parameter for calculating the Joule heat within the capacitor. Since the capacitor primarily absorbs high-frequency ripple, the RMS ripple current reflects the thermal stress intensity of the capacitor.

[0068] The aforementioned first equivalent series resistance value refers to the equivalent series resistance of the capacitor at the current operating temperature, calculated using the estimated temperature from the previous moment and the main frequency components of the current ripple current. This first equivalent series resistance value is based on a two-dimensional lookup table of equivalent series resistances measured in the laboratory at different temperatures and frequencies. The real-time value is obtained by using bilinear interpolation to look up the table based on the current estimated temperature and the characteristic frequency of the ripple current. The first equivalent series resistance value characterizes the equivalent resistance properties of the capacitor's internal electrodes, leads, and dielectric under an alternating current electric field.

[0069] The aforementioned dielectric loss tangent refers to the dielectric loss tangent of the bus capacitor at the current operating temperature, calculated using the estimated temperature from the previous moment and the dominant frequency component of the current ripple current. The dielectric loss tangent is based on a two-dimensional lookup table of dielectric loss tangents at different temperatures and frequencies, pre-measured in the laboratory. The real-time value is obtained by bilinear interpolation, using the current estimated temperature and the characteristic frequency of the ripple current. The dielectric loss tangent characterizes the proportion of energy consumed by the capacitor dielectric due to dielectric polarization hysteresis under an alternating electric field.

[0070] As an optional implementation, dynamic electrical parameters can be obtained and capacitor power loss calculated using a lookup table interpolation method. Specifically, the capacitor ripple current can be reconstructed based on the phase current and switching state, and the root mean square value of the capacitor ripple current over one control cycle can be calculated to obtain the effective value of the ripple current. Next, the estimated capacitor core temperature from the previous moment and the main frequency components of the current ripple current, such as the switching frequency, are read, and a two-dimensional lookup table pre-stored in the controller's non-volatile memory is accessed. This two-dimensional lookup table records the equivalent series resistance and dielectric loss tangent values ​​at different temperatures and frequencies. The first equivalent series resistance value and dielectric loss tangent value under the current operating condition are obtained using a bilinear interpolation algorithm. Finally, the Joule heat loss and dielectric loss are calculated separately to obtain the total power loss of the capacitor.

[0071] As an alternative implementation, a simplified linear model can be used for rapid estimation, suitable for scenarios with limited computing power or high real-time requirements. Specifically, the effective value of the ripple current is first calculated. Based on the initially calibrated equivalent series resistance and dielectric loss tangent, a simple linear temperature coefficient is introduced for correction, taking into account the current estimated temperature. For example, the equivalent series resistance increases linearly with temperature; by scaling the initial equivalent series resistance value using the temperature coefficient, an approximate equivalent series resistance value at the current temperature is obtained. The dielectric loss can be set to a fixed ratio based on experience or roughly estimated solely based on temperature. Finally, the Joule heat loss is calculated using the simplified equivalent series resistance and the effective value of the ripple current, and the total power loss of the capacitor is obtained by combining the simplified dielectric loss formula. This method avoids table lookups and interpolation calculations, reducing the processor load and making it suitable for rapid execution in automotive-grade vehicle control units or high-frequency interrupts.

[0072] Through the above settings, the lookup table interpolation method can accurately capture the nonlinear characteristics of capacitance parameters as a function of temperature and frequency. Under high-frequency operating conditions where dielectric loss contributes significantly to total loss, it provides higher estimation accuracy and is suitable for high-end vehicles with stringent thermal management requirements. The linear simplification method, on the other hand, sacrifices some accuracy for higher computational efficiency, reducing resource consumption in embedded systems and ensuring real-time response capabilities in resource-constrained environments. This implementation mechanism allows for adaptation to hardware platforms with different computing power levels, ensuring the possibility of high-precision estimation while providing a low-complexity alternative, thus enhancing the versatility, economy, and engineering feasibility of the technical solution.

[0073] In this embodiment of the application, determining the effective value of the ripple current based on phase current parameters and power switch status parameters includes: determining the inverter DC-side current based on phase current parameters and power switch status parameters, wherein the inverter DC-side current is used to represent the DC current value flowing into the inverter DC side of the electronic control unit; and determining the effective value of the ripple current based on the inverter DC-side current and the battery output current, wherein the battery output current is used to represent the DC current value output by the battery in the electronic control unit.

[0074] The inverter DC-side current mentioned above refers to the instantaneous current value flowing into the DC bus terminal of the inverter in the electronic control unit. The inverter DC-side current is calculated through mathematical reconstruction based on the existing three-phase current parameters and power switch status parameters of the electronic control unit.

[0075] The aforementioned battery output current refers to the DC current value directly output from the high-voltage battery pack to the input terminal of the electronic control unit. The battery output current is directly acquired by a DC current sensor installed at the battery output terminal or the controller input terminal. The battery output current has significant inertia and exhibits a smoother behavior, primarily containing low-frequency or quasi-DC components. When calculating ripple current, the battery output current is used as a reference DC current, and its difference is calculated with the inverter's DC-side current to separate the capacitor ripple current specifically provided by the charging and discharging of the bus capacitors.

[0076] As an optional implementation, the instantaneous value of the DC-side current can be reconstructed based on the switching function, and the effective value of the ripple current can be calculated. Specifically, the phase current parameters of the three-phase motor and the power switching status parameters of each arm of the inverter can be acquired in real time. Within each control cycle, the instantaneous current waveform flowing into the DC side of the inverter is reconstructed, which includes high-frequency ripple components caused by switching operations. Subsequently, the reconstructed instantaneous current is subtracted in real time from the battery output current directly acquired by the DC bus sensor to obtain the instantaneous ripple current flowing through the bus capacitor. Finally, within a complete switching cycle or a specific time window, the instantaneous ripple current is squared, integrated, and square-rooted to obtain the effective value of the ripple current.

[0077] By setting up the ripple current RMS value based on the inverter's DC-side current and the battery output current, there is no need to install a high-frequency current sensor on the DC bus. Utilizing the phase current sensor and the controller's switching state information, the RMS value of the ripple current can be obtained through algorithm reconstruction, reducing hardware costs and system complexity. Through accurate reconstruction and differential calculation, the actual high-frequency ripple current borne by the capacitor can be effectively separated, avoiding interference from low-frequency fluctuations on the battery side in loss calculations. This improves the accuracy of ripple current estimation, accurately locates the internal heat loss sources of the capacitor, provides a reliable data foundation for subsequent high-precision temperature estimation, and enhances the system's thermal management capabilities and safety.

[0078] In this embodiment of the application, determining the effective value of the ripple current based on the inverter DC-side current and the battery output current includes: determining the capacitor ripple current based on the difference between the inverter DC-side current and the battery output current, wherein the capacitor ripple current is used to represent the ripple current value provided by the capacitor; and calculating the root mean square value of the capacitor ripple current within the target control cycle to obtain the effective value of the ripple current.

[0079] The aforementioned capacitor ripple current refers to the instantaneous value of the AC current flowing through the bus capacitor. The capacitor ripple current is obtained by calculating the difference between the inverter's DC-side current and the battery output current. Due to the significant capacitive and inductive effects of the battery, the battery output current is relatively smooth, mainly providing a low-frequency or DC component. The inverter's DC-side current includes high-frequency pulsations caused by motor load fluctuations and high-frequency power switching. The difference between the inverter's DC-side current and the battery output current represents the high-frequency AC current component that needs to be absorbed or released by the bus capacitor, i.e., the capacitor ripple current.

[0080] The aforementioned target control cycle can refer to the basic time unit for the execution of the main control program of the electronic control unit or the thermal management estimation algorithm.

[0081] As an optional implementation, the root mean square (RMS) value can be calculated using a numerical integration method based on discrete sampling points. Specifically, discrete sampling sequences of the inverter DC-side current and battery output current can be acquired at a high-frequency sampling rate within the target control cycle. The difference between the inverter DC-side current and the battery output current is calculated point by point to obtain a discrete sequence of capacitor ripple current. Subsequently, each sample value in this discrete sequence is squared. Then, the squared values ​​are summed within the target control cycle to obtain a sum of squares. Finally, the sum of squares is divided by the number of sampling points, and the square root is taken to obtain the effective value of the ripple current. This method is directly based on time-domain sampling data, the calculation process is simple and intuitive, it is applicable to most digital signal processors, can accurately reflect the thermal effect of periodic ripple current, and does not require additional filtering, thus reducing phase delay.

[0082] By directly utilizing the difference between the inverter's DC-side current and the battery's output current, an additional dedicated high-frequency current sensor is unnecessary, reducing hardware costs and improving system integration. The calculated root mean square (RMS) value accurately reflects the thermal effect of ripple current across the resistor, thus ensuring the accuracy of the temperature estimation model.

[0083] In this embodiment of the application, the method further includes: obtaining the historical temperature of the capacitor core and the characteristic frequency of the ripple current, wherein the historical temperature of the capacitor core is used to represent the temperature of the capacitor core determined by at least one historical control cycle, and the characteristic frequency of the ripple current is used to represent the frequency component corresponding to the ripple current; determining a first equivalent series resistance value based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the resistance temperature-frequency mapping relationship, wherein the resistance temperature-frequency mapping relationship is used to represent the mapping relationship of the fitted resistance value with the two-dimensional parameters of temperature and frequency; and determining the dielectric loss tangent value based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the loss temperature-frequency mapping relationship, wherein the loss temperature-frequency mapping relationship is used to represent the mapping relationship of the fitted loss tangent with the two-dimensional parameters of temperature and frequency.

[0084] The aforementioned historical temperature of the capacitor core can refer to the temperature value of the internal hot spot of the capacitor calculated using the temperature estimation method described above in at least one past control cycle. Since the electrical characteristics of the capacitor change with temperature, an iterative estimation strategy is adopted, that is, using the estimated temperature from the previous moment as the input variable for querying the electrical characteristic parameters at the current moment.

[0085] The aforementioned ripple current characteristic frequency can refer to the dominant frequency component in the ripple current flowing through the bus capacitor. The ripple current characteristic frequency can be composed of the following main frequency components: the pulse width modulation switching frequency and harmonics of the inverter power devices; the motor frequency and harmonics; and the fundamental frequency and harmonics determined by the motor speed and number of pole pairs.

[0086] The aforementioned resistance-temperature-frequency mapping relationship can refer to a two-dimensional lookup table or mathematical fitting function model pre-stored in the controller's non-volatile memory, describing the correspondence between the equivalent series resistance value of the bus capacitor and temperature and frequency. This resistance-temperature-frequency mapping relationship is generated by measuring the same type of capacitor at different temperatures and frequencies using an impedance analyzer in a laboratory environment, collecting a large number of data points, and then fitting the data.

[0087] The aforementioned temperature-frequency loss mapping relationship can refer to a two-dimensional lookup table or mathematical fitting function model pre-stored in the controller's non-volatile memory, describing the correspondence between the dielectric loss tangent of the bus capacitor and temperature and frequency. Impedance tests were conducted on capacitors of the same model at multiple temperature and frequency points in a laboratory environment, recording the dielectric loss tangent data under different conditions and then fitting the data to generate the mapping.

[0088] As an optional implementation, bilinear interpolation can be performed using a pre-stored two-dimensional lookup table. Specifically, the historical temperature of the capacitor core, estimated at the previous moment, is obtained and stored in a circular buffer as the initial temperature estimate for the current moment. The characteristic frequency of the ripple current is determined based on the current motor speed and inverter switching frequency. Next, the resistance-temperature-frequency mapping table and the loss-temperature-frequency mapping table, stored in the controller's non-volatile memory, are accessed. These tables are pre-calibrated through laboratory testing and record the equivalent series resistance and dielectric loss tangent values ​​at different temperature and frequency points. Then, bilinear interpolation is performed in the corresponding two-dimensional tables using the historical temperature and characteristic frequency as coordinates to accurately obtain the first equivalent series resistance and dielectric loss tangent values ​​under the current operating conditions. This method can highly fit the nonlinear variation characteristics of the capacitor parameters, providing high-precision parameter estimation.

[0089] As an alternative implementation, real-time calculations can be performed using analytical function models. Specifically, the historical temperature and ripple current characteristic frequency of the capacitor core are obtained, and pre-fitted mathematical expressions are used. For the equivalent series resistance, an empirical formula incorporating temperature and frequency coefficients is employed; for the dielectric loss tangent, a similar exponential or logarithmic function model is used. Substituting the historical temperature and characteristic frequency into these analytical formulas, the current equivalent series resistance and dielectric loss tangent values ​​are directly calculated. This method avoids the memory overhead and interpolation computation costs associated with table lookups, offers fast calculation speed, and is suitable for microcontrollers with limited computing power or storage resources. Furthermore, it can meet the requirements for thermal estimation within a certain accuracy range.

[0090] The above settings, based on historical temperature and characteristic frequency, determine the electrical parameters. By introducing temperature dependence, the error caused by assuming a fixed equivalent series resistance value is resolved. Since the equivalent series resistance and dielectric loss of the capacitor change with temperature, dynamic correction improves the accuracy of loss calculation. Considering frequency characteristics allows for adaptation to ripple spectrum variations under different operating conditions, and in scenarios with significant high-frequency switching noise, it more realistically reflects the capacitor's heating behavior.

[0091] In this embodiment, the layered heat conduction equivalent model includes at least two heat conduction equivalent layers: a core-to-inner shell heat conduction equivalent layer, an inner shell-to-outer shell heat conduction equivalent layer, an outer shell-to-heat sink heat conduction equivalent layer, and a heat sink-to-ambient heat conduction equivalent layer. Based on the layered heat conduction equivalent model and capacitor power loss, the capacitor core temperature is determined, including: determining the step response parameters of the layered heat conduction equivalent model in the time domain based on the capacitor power loss and the thermal resistance and thermal capacitance parameters corresponding to each heat conduction equivalent layer; and determining the capacitor core temperature based on the step response parameters.

[0092] The aforementioned equivalent thermal conduction layer from the core to the inner shell refers to an equivalent thermal network unit that simulates the heat transfer process between the core heating area inside the capacitor and the first metal shielding or encapsulation layer surrounding the core. The equivalent thermal conduction layer from the core to the inner shell primarily characterizes the resistance to heat conduction from the capacitor's internal dielectric and electrodes to the first heat dissipation interface, as well as its heat storage capacity.

[0093] The aforementioned inner-shell to outer-shell thermal conductivity equivalent layer can refer to an equivalent thermal network unit that simulates the heat transfer process from the inner shell of the capacitor to the outer metal casing. The inner-shell to outer-shell thermal conductivity equivalent layer characterizes the thermal resistance and thermal capacitance of heat transferred from the inner shell to the outer shell through the capacitor's internal insulation structure, potting compound, or epoxy resin.

[0094] The aforementioned equivalent heat conduction layer from the capacitor casing to the heat sink can refer to an equivalent thermal network unit that simulates the heat transfer process from the surface of the capacitor casing to the mounting surface of the motor controller heat sink. The equivalent heat conduction layer from the capacitor casing to the heat sink characterizes the contact thermal resistance at the interface between the capacitor casing and the heat sink, as well as the thermal conductivity of any auxiliary materials such as thermal grease and insulating pads that may be present.

[0095] The aforementioned equivalent heat transfer layer from the radiator to the environment can refer to an equivalent thermal network unit that simulates the heat transfer process from the surface of the motor controller radiator to the surrounding cooling medium. The equivalent heat transfer layer from the radiator to the environment characterizes the radiator's ability to dissipate heat to the external environment. The thermal resistance of this layer is highly dependent on cooling conditions, such as coolant flow rate, velocity, ambient temperature, and airflow rate.

[0096] The aforementioned thermal resistance parameters can refer to the thermal resistance values ​​corresponding to each thermal conduction equivalent layer in the layered thermal conduction equivalent model.

[0097] The aforementioned heat capacity parameters can refer to the heat capacity values ​​corresponding to each heat conduction equivalent layer in the layered heat conduction equivalent model.

[0098] The aforementioned step response parameters can refer to the response characteristic parameters of the temperature of each node in the hierarchical heat conduction equivalent model as a function of time when the capacitor power loss undergoes a step change in the time domain.

[0099] As an optional implementation, an analytical solution can be calculated using a layered heat conduction equivalent model. This model physically divides the capacitor's heat conduction path into multiple series-connected thermal resistance-capacitance links, such as core to inner shell, inner shell to outer shell, outer shell to heat sink, and heat sink to environment. The thermal resistance and capacity of each link are determined based on the physical dimensions and material properties of each layer. In the time domain, the temperature rise generated by each thermal resistance-capacitance link is calculated using the step response formula, with power loss as the step input. The temperature rise responses of each link are superimposed to obtain the total temperature rise. Finally, the total temperature rise is added to the ambient temperature, and the temperature of the inner node is taken as the capacitor core temperature. This method has clear physical meaning, an intuitive calculation process, and can accurately describe the dynamic process of heat generation and dissipation, making it suitable for scenarios requiring high-precision physical modeling.

[0100] As an alternative implementation, a hierarchical heat conduction equivalent model combined with state-space equations can be used for numerical iterative solution. Specifically, a hierarchical heat conduction equivalent model is constructed and transformed into a discrete state-space form. The state vector contains the temperature rise of each hot node. In each control cycle, the state vector is updated through matrix multiplication. Using the temperature rise state of the previous moment and the current power loss, the temperature rise of each node in the next moment is predicted through the state transition matrix. The capacitor core temperature can be extracted from the end node in the state vector. This method avoids the high overhead of real-time calculation of exponential functions, has high computational efficiency, is suitable for real-time operation in resource-constrained automotive-grade vehicle control units, ensures the real-time and continuous nature of temperature estimation, and performs better under high-frequency sampling requirements.

[0101] Through the above setup, the hierarchical heat conduction equivalent model provides a clear physical mapping, facilitating the understanding of heat transfer mechanisms. It also offers advantages in offline calibration and verification, ensuring the accuracy of model parameters. The spatial method improves the computational load of embedded systems by pre-computing matrix parameters, transforming complex physical differential equations into efficient algebraic operations, meeting the stringent real-time control requirements of new energy vehicle electronic control systems. This implementation strategy enables the technical solution to meet the needs of high-precision thermal analysis while adapting to engineering implementation on different computing platforms, enhancing the versatility and practical application value of the technical solution, and ensuring robust, real-time capacitor temperature estimation under various operating conditions.

[0102] In this embodiment, determining the capacitor core temperature based on step response parameters includes: determining the temperature rise state vector corresponding to each thermal conduction equivalent layer based on step response parameters, state transition matrix, and input gain matrix, wherein the state transition matrix is ​​determined based on thermal resistance parameters and thermal capacity parameters, the thermal state evolution characteristic matrix, the input gain matrix is ​​determined based on thermal resistance parameters and thermal capacity parameters, and the weighted contribution matrix of power loss to temperature rise is used; and determining the capacitor core temperature based on the temperature rise state vector.

[0103] The aforementioned state transition matrix can be considered as a linear transformation matrix describing the natural evolution of the temperature state of each node in the heat conduction equivalent model over time within the discretized time domain. In other words, it represents the temperature change relying solely on the system's internal thermal inertia without any new power loss input. The state transition matrix reflects the memory and decay characteristics of the thermal state between different control cycles. For example, the temperature rise accumulated in the previous time step will decay or be passed on to the next time step according to the proportion of this state transition matrix.

[0104] The aforementioned input gain matrix can be considered a linear transformation matrix in the discretized time domain, describing the instantaneous contribution of the current input capacitor power loss to the temperature rise of each node in the system. It weights the current thermal power input and distributes it to each thermally-state node. The input gain matrix characterizes the efficiency and hysteresis effect of converting power loss into temperature rise. For example, power loss first causes a temperature rise in the inner nodes, and then gradually conducts to the outer layers through thermal resistance.

[0105] The aforementioned temperature rise state vector refers to the set of temperature rise values ​​for each node in the layered heat conduction equivalent model during the current control cycle. Each element in the temperature rise state vector represents the temperature rise relative to the ambient temperature or the previous level ambient temperature. The last element in the temperature rise state vector corresponds to the temperature rise of the capacitor core relative to the installation reference point.

[0106] As an optional implementation, a discretized iterative solution based on the state-space equations can be performed. Specifically, a state transition matrix and an input gain matrix can be pre-constructed based on the thermal resistance and thermal capacity parameters of each layer in the layered heat conduction model. The state transition matrix describes the evolution characteristics of the internal thermal state of the system, i.e., how the temperature rise of each hot node at the previous moment affects the current state; the input gain matrix describes how the power loss at the current moment contributes weighted to the temperature rise of each hot node. In each control cycle, the current capacitor power loss is collected as input, and calculations are performed using the corresponding formula. Through matrix multiplication, the temperature rise state vector corresponding to each equivalent heat conduction layer at the current moment is obtained. Finally, the temperature rise component corresponding to the capacitor core sub-node is extracted from this state vector, which is the temperature rise state of that layer, thus obtaining the temperature rise state vector.

[0107] As an alternative implementation, a reduced-order model or simplified matrix operations can be used to improve computational efficiency. Specifically, the state transition matrix and input gain matrix can be determined based on thermal resistance and thermal capacity parameters. To reduce computational complexity, a high-order model can be reduced to a low-order model, or the matrix can be sparsified. During the calculation, instead of performing full matrix multiplication directly, the state vector can be updated through row-by-row or column-by-column scalar operations, utilizing specific matrix structures such as diagonal or lower triangular matrices. For example, the state transition matrix can be a diagonal matrix, simplifying the calculation to independent exponential decay updates for each state variable. Combined with the current power loss, the temperature rise of each layer is obtained through simplified weighted summation. This method reduces the number of floating-point operations and memory access overhead, making it suitable for resource-constrained microcontrollers. Finally, the temperature rise of the capacitor core sub-nodes is read from the updated state vector as the output.

[0108] By setting up the temperature rise state vector based on the state transition matrix and input gain matrix, the continuous physical process of heat conduction is transformed into a discrete mathematical model, which facilitates real-time calculation of the internal temperature distribution of the capacitor in a digital processor. Pre-calculating matrix parameters transforms the solution of complex differential equations into efficient matrix operations, improving computational speed and meeting the high-frequency sampling and real-time control requirements of new energy vehicle electronic control systems. The state vector not only outputs the core temperature but also indirectly reflects the thermal state of each internal layer, providing data support for more accurate thermal management strategies and enhancing the system's safety and reliability.

[0109] In this embodiment of the application, determining the capacitor core temperature based on the temperature rise state vector includes: determining the capacitor core temperature based on the temperature rise state vector and the ambient temperature of the circuit system.

[0110] The ambient temperature mentioned above can refer to the temperature of the surrounding medium, which serves as a reference point in the heat conduction model.

[0111] As an alternative implementation, the core temperature rise can be directly mapped using a state-space output matrix combined with the ambient temperature. Specifically, data from specific nodes can be extracted from the temperature rise state vector calculated in the previous stage; these nodes physically correspond to hot spots within the capacitor core. In the discretized thermal network model, the hot nodes directly connected to the capacitor core are selected as representatives of the core temperature. An output matrix is ​​defined that maps the state vector to the relative temperature rise of the core. During the calculation, a vector dot product operation is performed to obtain the temperature rise of the capacitor core relative to a reference temperature. Subsequently, the ambient temperature of the current circuit system is read. Finally, the capacitor core temperature is determined based on the sum of the temperature rise state vector and the ambient temperature. This method is logically clear, directly reflects the cumulative effect of heat conduction from the environment to the core, and ensures the physical consistency of the temperature estimation.

[0112] By setting up the capacitor core temperature based on the temperature rise state vector and ambient temperature, the internal thermal dynamics process is organically combined with external boundary conditions, realizing a mapping from relative temperature rise to absolute temperature and ensuring the actual physical meaning of the estimation results. The introduction of a dynamic processing and compensation mechanism for ambient temperature enhances the adaptability to harsh operating conditions and environmental changes, improving the algorithm's robustness. This simple linear superposition structure has low computational complexity, is easy to implement in embedded systems, and ensures real-time performance. This process provides an accurate and reliable temperature reference for subsequent thermal management strategies, enabling the system to make protection decisions based on the actual core temperature rather than the outer casing temperature, effectively preventing capacitor overheating failure and improving the overall vehicle safety and reliability.

[0113] In this embodiment, the target conductive equivalent layer includes a heat conduction equivalent layer from the shell to the heat sink and a heat conduction equivalent layer from the heat sink to the environment. When the layered heat conduction equivalent model includes the target conductive equivalent layer and the heat sink used in the circuit system is a liquid-cooled heat sink, the method further includes: adjusting the initial thermal resistance parameter corresponding to the target conductive equivalent layer based on the coolant flow rate of the liquid-cooled heat sink to obtain the thermal resistance parameter corresponding to the target conductive equivalent layer.

[0114] The aforementioned coolant flow rate can refer to the flow rate of the cooling medium that flows through the cooling channel to remove heat in a motor controller system that uses a liquid-cooled radiator.

[0115] As an optional implementation, linear or nonlinear mapping adjustments based on a pre-calibrated lookup table can be performed. Specifically, the thermal resistance data of the liquid-cooled radiator under various coolant flow rates can be pre-calibrated through bench tests, establishing a lookup table between coolant flow rate and thermal resistance, and storing this lookup table in the controller memory. This lookup table covers the thermal resistance variation curves of the two target conductive equivalent layers—from the outer shell to the radiator and from the radiator to the environment—ranging from lower to higher flow rates. During vehicle operation, the control signal of the liquid-cooled pump or the data from the flow meter sensor is read in real time to obtain the current coolant flow rate. Subsequently, the lookup table is queried using the coolant flow rate as an index. If the coolant flow rate does not directly correspond to a discrete point in the table, linear interpolation or a high-order polynomial fitting algorithm is used to calculate the corresponding thermal resistance adjustment coefficient or directly obtain the corrected thermal resistance value. Finally, the calculated corrected thermal resistance value replaces the original initial thermal resistance parameters in the thermal network model, thereby dynamically updating the thermal resistance parameters of the target conductive equivalent layer and ensuring that the model accurately reflects the heat dissipation capacity under the current cooling conditions.

[0116] By adjusting the target thermal resistance parameters of the equivalent heat conduction layer based on the coolant flow rate, the layered heat conduction equivalent model can reflect the changes in heat dissipation efficiency of the liquid cooling system under different power conditions and pump speeds in real time. Dynamically correcting the thermal resistance from the casing to the environment improves the accuracy of capacitor core temperature estimation, enabling more timely warnings of overheating risks when insufficient cooling occurs due to high loads or low-speed operation. This adaptive mechanism enhances the robustness of the thermal management system, ensuring that even with minor performance degradation of the cooling system throughout its entire lifespan, the layered heat conduction equivalent model maintains high accuracy, providing a reliable basis for predictive maintenance and proactive thermal protection.

[0117] In this embodiment of the application, the method further includes: obtaining the aging coefficient of the capacitor, wherein the aging coefficient is used to characterize the degree of aging of the capacitor; adjusting the capacitor power loss based on the aging coefficient to obtain the adjusted capacitor power loss; adjusting the thermal resistance parameter and thermal capacity parameter corresponding to each heat conduction equivalent layer in the layered heat conduction equivalent model based on the aging coefficient to obtain the adjusted layered heat conduction equivalent model; and determining the capacitor core temperature based on the adjusted capacitor power loss and the adjusted layered heat conduction equivalent model.

[0118] The aforementioned aging factor can refer to a dimensionless scaling factor used to quantify the degree of performance degradation of bus capacitors due to long-term use.

[0119] The adjusted capacitor power loss mentioned above refers to the power loss value that is closer to the actual heat generation after the aging factor is introduced to correct the original calculated capacitor power loss.

[0120] The aforementioned adjusted layered heat conduction equivalent model can refer to the model obtained by fine-tuning or updating the thermal resistance and heat capacity parameters in the model based on the initial layered heat conduction equivalent model using an aging coefficient.

[0121] As an optional implementation, aging factor acquisition and model correction are performed based on periodic online equivalent series resistance identification. Specifically, when the vehicle starts self-test or detects a steady-state light-load condition, the online equivalent series resistance identification program is triggered. The controller injects a small-amplitude common-mode voltage signal of a specific frequency into the inverter, causing the DC bus to generate a ripple current of known amplitude and frequency. Simultaneously, the ripple component voltage corresponding to the DC bus voltage is collected, and the current actual equivalent series resistance value is calculated. The system compares the actual equivalent series resistance value with the equivalent series resistance value in the initial healthy state of the capacitor to calculate the aging factor. Subsequently, the equivalent series resistance term in the power loss calculation is scaled using this aging factor to obtain the adjusted power loss. According to the empirical model, the aging factor is mapped to the thermal resistance parameters of the layered heat conduction equivalent model proportionally or nonlinearly. For example, it is assumed that aging causes a slight decrease in internal thermal conductivity, and the thermal resistance increases linearly with the aging factor, thereby updating the thermal resistance and thermal capacity parameters in the layered heat conduction equivalent model, and then calculating the capacitor core temperature based on the updated model parameters.

[0122] As an alternative implementation, an aging factor can be derived based on cumulative thermal stress or capacity decay estimation, and the degree of aging can be estimated through cumulative analysis of long-term operating data. The capacitor's operating temperature history, ripple current RMS value, and duration are recorded in real time, and the cumulative thermal stress damage value is calculated by combining linear cumulative damage theory or an electrolytic capacitor life model. Alternatively, the capacitor's capacitance decay can be indirectly inferred by monitoring the trend of DC bus voltage ripple amplitude changes, and then the aging factor can be derived. When the cumulative damage value or capacitance change exceeds a preset threshold, the aging factor is updated. Then, the power loss is corrected using this aging factor. Considering that aging affects not only the equivalent series resistance but also the dielectric loss, the terms in the total loss formula are weighted and adjusted. For the layered heat conduction equivalent model, a pre-stored aging-thermal parameter mapping table is used. Based on the current aging factor, the corresponding new thermal resistance and new thermal capacitance parameters are queried and replaced with the old thermal resistance and old thermal capacitance parameters in the layered heat conduction equivalent model. This non-invasive method requires no additional control actions and utilizes operating data to achieve aging tracking throughout the entire life cycle.

[0123] By adjusting power loss and thermal model parameters based on the aging factor, this approach solves the estimation error problem caused by the time-varying capacitor parameters in the thermal model, achieving adaptive updates of the layered heat conduction equivalent model parameters as the device's health status evolves. Real-time correction of power loss and thermal resistance improves the long-term accuracy of capacitor core temperature estimation throughout its lifespan, avoiding overheating risks caused by temperature underestimation due to aging. This mechanism eliminates the need for additional hardware sensors; monitoring the internal state of the capacitor is achieved through software algorithms, reducing system costs. This adaptive capability enhances the robustness of the thermal management strategy, providing reliable temperature warnings and protection even in cases of capacitor performance degradation, extending motor lifespan, and improving the overall vehicle safety and reliability.

[0124] In this embodiment of the application, when the circuit system is an electronic control unit and the capacitor is a bus capacitor, obtaining the aging coefficient of the capacitor includes: in response to receiving a calibration command, injecting a common-mode voltage signal of a preset amplitude into the inverter in the electronic control unit, and collecting the ripple component voltage parameter and ripple component current parameter corresponding to the target ripple current generated on the DC bus; determining the second equivalent series resistance value based on the ripple component voltage parameter and ripple component current parameter; and determining the aging coefficient based on the second equivalent series resistance value and the first equivalent series resistance value.

[0125] The aforementioned calibration command may refer to the command that triggers the system to execute the online identification algorithm for capacitor aging status.

[0126] The aforementioned preset amplitude common-mode voltage signal can refer to artificially tested voltage fluctuations of a specific frequency and amplitude injected into the DC bus.

[0127] The ripple component voltage parameter corresponding to the target ripple current mentioned above can refer to the voltage fluctuation component generated on the DC bus under common-mode voltage signal excitation, which has the same frequency as the target ripple current.

[0128] The ripple component current parameter corresponding to the target ripple current mentioned above can refer to the current fluctuation component with the same frequency as the target current flowing through the DC bus capacitor under the excitation of a common-mode voltage signal with a preset amplitude.

[0129] The aforementioned second equivalent series resistance value refers to the capacitor's equivalent series resistance value measured in real time using the online identification algorithm described above. This second equivalent series resistance value is the capacitor's true equivalent series resistance value under its current aging condition. It is compared with the first equivalent series resistance value initially stored in the system; the ratio is the aging factor. The second equivalent series resistance value reflects the increase in internal losses caused by long-term use of the capacitor.

[0130] As an optional implementation, a time-domain analysis method utilizing pulse-width modulation (PWM) to inject common-mode voltage disturbances can be used to determine the aging factor. When the system receives a calibration command, such as during vehicle start-up self-test or a specific maintenance mode, the controller adjusts the PWM duty cycle to superimpose a small-amplitude sinusoidal or square-wave common-mode voltage signal of a known frequency (which can be the switching frequency or a specific harmonic frequency) onto the DC bus. This common-mode voltage signal generates a specific ripple current on the DC side. By acquiring the ripple component of the DC bus voltage and the ripple current component obtained through reconstruction or measurement, and since the injected signal frequency is fixed and the amplitude is known, the system calculates the ratio of the effective value of the voltage ripple to the effective value of the current ripple within one or more signal cycles. This yields the second equivalent series resistance under the current operating condition. Based on the second and first equivalent series resistance values, the aging factor is then determined. This method directly utilizes the inverter's own modulation capability, eliminating the need for external testing equipment, and achieves in-situ measurement of the capacitor's internal impedance characteristics, accurately reflecting the capacitor's impedance state under actual operating voltage.

[0131] Through the above setup, this method of determining the aging coefficient based on injected common-mode voltage signals provides a non-invasive, high-precision online monitoring method for capacitor health status. It allows for real-time acquisition of changes in equivalent series resistance without disassembling the capacitor or using external instruments. Secondly, by comparing the current equivalent series resistance with the initial equivalent series resistance, the degree of capacitor aging can be quantified, providing a basis for the adaptive correction of parameters in the layered heat conduction equivalent model, thereby maintaining the long-term accuracy of temperature estimation. This process is triggered at specific moments, having minimal impact on normal driving conditions, achieving full lifecycle health management. This proactive identification mechanism enhances the system's self-diagnostic capabilities, enabling the controller to detect capacitor performance degradation in advance, achieving predictive maintenance, avoiding sudden failures, and improving the safety and reliability of new energy vehicles.

[0132] The technical solution proposed in this application is described below with reference to an optional embodiment. This application proposes a method and system for estimating the temperature of the bus capacitor in a drive motor controller for new energy vehicles, belonging to the field of new energy vehicle electronic control technology. Specifically, it is a method and system for online estimation of the internal temperature of the DC bus support capacitor in the drive motor controller of electric vehicles, hybrid vehicles, and other vehicles. The aim is to estimate the core temperature of the bus capacitor in real time with high accuracy, high reliability, and low cost, so as to achieve accurate thermal management and predictive maintenance, thereby improving the lifespan of the motor controller and the safety level of the entire vehicle.

[0133] Figure 2 This is a schematic diagram of the technical framework of a capacitor temperature determination method according to an embodiment of this application, as shown below. Figure 2As shown, the system includes a dynamic thermal network model with a capacitor power loss calculation module and a hierarchical heat conduction equivalent model, as well as a multi-parameter online self-correction module with a dynamic correction module based on cooling conditions and a correction module based on capacitor aging status. The system transmits data to the capacitor core temperature calculation module, and then transmits the data to the graded early warning and protection strategy formulation module.

[0134] This application presents a bus capacitor temperature estimation scheme based on a dynamic thermal network model and multi-parameter online self-correction. This scheme constructs a high-order thermal network model that accurately characterizes the internal heat conduction and external heat dissipation processes of the capacitor; uses real-time calculated capacitor power loss as model input; and introduces an online adaptive correction mechanism for model parameters based on cooling conditions and capacitor health status. This achieves accurate, real-time, and robust estimation of the capacitor core temperature. The specific technical solution includes the following modules and steps:

[0135] An accurate capacitor power loss calculation module is proposed, which calculates the capacitor power loss of the bus capacitor. It mainly consists of equivalent series resistance (ESR) loss and dielectric loss:

[0136] ;

[0137] in, To determine the effective value of the ripple current, this application utilizes existing phase current sensors and switch status information from the motor controller for reconstruction. Specifically, the method involves reconstructing the ripple current based on the switching function of the three-phase inverter, i.e., the power switch status parameters (…). , , ) and the measured three-phase currents, i.e., phase current parameters ( , , ), through formula Reconstruct the current flowing into the DC side of the inverter, i.e., the inverter DC side current. The inverter's DC-side current Compared to the relatively smooth DC current from the battery, i.e., the battery output current The difference is the ripple current provided by the capacitor, i.e., the capacitor ripple current. The effective value is then calculated within one control cycle to obtain the effective value of the ripple current. and These are the equivalent series resistance and the dielectric loss tangent, respectively, which are functions of temperature T and frequency f. In this application, prior measurements of multiple sets of equivalent series resistance and dielectric loss tangent data at different temperatures and frequencies were conducted in a laboratory environment using a precision impedance analyzer. These data were then used to create a two-dimensional lookup table, which was stored in the controller's read-only memory. During online estimation, the estimated temperature from the previous moment is used... The main frequency component of the current ripple current, determined by the motor frequency and switching frequency (i.e., the characteristic frequency of the ripple current), is used for bilinear interpolation to obtain the accurate first equivalent series resistance value and dielectric loss tangent value. This indicates the capacitance value of the capacitor. This indicates the voltage across the capacitor.

[0138] A high-order dynamic thermal network model construction and solution module is proposed. A fourth-order resistance-capacitance thermal network is used to accurately simulate the thermal dynamic process of a capacitor. This hierarchical heat conduction equivalent model decomposes the thermal behavior of a physical capacitor into four series-connected thermal resistance-capacitance (THC) networks. The three stages correspond to heat transfer paths such as from the core to the inner shell, from the inner shell to the outer shell, from the outer shell to the heat sink, and from the heat sink to the environment. The step response of this layered heat conduction equivalent model in the time domain, i.e., the step response parameters of the layered heat conduction equivalent model in the time domain, are also discussed. It can be represented as follows:

[0139] ;

[0140] in, The thermal time constants of each stage are derived from the thermal resistance parameters of each layer. and heat capacity parameters The product is determined; Represents the time variable. Based on step response parameters. and capacitor power loss The capacitor power loss generated by the capacitor at time k can be determined. To facilitate real-time computation in a microprocessor, the continuous model is discretized. Using the backward Euler method, the state-space equations are established as follows:

[0141] ;

[0142] in, It is the temperature rise state vector of each hot node at time k, where A and B are the temperature rise state vectors of each layer. and The system matrix, state transition matrix, and input gain matrix are constructed. The capacitor core temperature is also considered. for:

[0143] ;

[0144] in, For ambient temperature, The output matrix is ​​typically [0,0,0,1], and the last node is selected as the core temperature.

[0145] Figure 3 This is a schematic diagram of a layered heat conduction equivalent model according to an embodiment of this application, such as... Figure 3 As shown, the layered heat conduction equivalent model includes four heat conduction equivalent layers: the heat conduction equivalent layer from the core interior to the inner shell, corresponding to the thermal resistance parameter Rth4 and the thermal capacity parameter Cth4; the heat conduction equivalent layer from the inner shell to the outer shell, corresponding to the thermal resistance parameter Rth3 and the thermal capacity parameter Cth3; the heat conduction equivalent layer from the outer shell to the heat sink, corresponding to the thermal resistance parameter Rth2 and the thermal capacity parameter Cth2; and the heat conduction equivalent layer from the heat sink to the environment, corresponding to the thermal resistance parameter Rth1 and the thermal capacity parameter Cth1. In the figure, Ta represents the ambient temperature, Ts represents the heat sink temperature, Th represents the outer shell temperature, Ti represents the inner shell temperature, and Tc represents the capacitor core temperature.

[0146] An online adaptive correction module for model parameters is proposed, which adjusts the initial thermal network parameters (...). The results were obtained through experiments with a capacitor under a step power load and curve fitting techniques. To improve the model's adaptability throughout its entire lifespan, this application designs the following online correction strategy: dynamic correction based on cooling conditions, and thermal resistance of the capacitor's heat dissipation path (from the casing to the environment). It is highly dependent on cooling conditions. For liquid-cooled controllers, the ambient temperature can be obtained using the controller's insulated-gate bipolar transistor temperature sensor reading or a separate coolant temperature sensor reading. Based on the coolant flow rate To dynamically correct Through bench testing, the pre-calibrated... and Mapping relationship (such as) ), and store it as a lookup table, These are configurable calibration parameters. During online operation, this table is queried based on the real-time flow rate to update the corresponding thermal resistance parameters in the thermal network model. value.

[0147] This paper proposes a correction based on capacitor aging. During use, the equivalent series resistance of a capacitor gradually increases due to aging, leading to actual power loss higher than the calculated value based on initial parameters. To address this, this application periodically executes an online equivalent series resistance identification algorithm, for example, during each vehicle start-up self-test or when a steady-state light-load condition is detected. Under the premise of stable DC bus voltage, a small-amplitude common-mode voltage signal of a specific frequency, such as the switching frequency, is injected into the inverter through the controller's pulse width modulation unit. This generates a ripple current with known amplitude and frequency on the DC side, i.e., the target ripple current, and then the ripple component current parameters are collected. Simultaneously, the ripple component of the DC bus voltage is sampled, i.e., the ripple component voltage parameter. The actual equivalent series resistance value at that frequency, i.e., the second equivalent series resistance value, is then... for:

[0148] ;

[0149] Then calculate the aging coefficient. , here This represents the first equivalent series resistance value determined above. The aging factor is used for two corrections: correcting power loss calculations. ; Empirically fine-tune the internal thermal resistance of the heat network (e.g. This is because aging means a deterioration in internal thermal conductivity.

[0150] The proposed temperature estimation output and thermal management execution module, integrating the above steps, performs the following process within each control cycle (e.g., 100μs): acquiring electrical and cooling system signals; calculating ripple current and power loss; adaptively correcting model parameters; solving the discretized thermal network state equation; and outputting the capacitor core temperature for the current cycle. The estimated capacitor core temperature is directly used in the upper-level thermal management strategy for graded early warning and protection. (e.g., 85°C), the system operates normally; when (e.g., 95°C) triggers a Level 1 warning, sending a warning message to the instrument panel via the controller's local area network bus; when This triggers the secondary protection, and the motor controller enters the derating mode, reducing the output torque according to the preset curve and forcibly reducing the ripple current, causing the capacitor temperature to drop.

[0151] The following detailed description of this application is based on an embodiment of a water-cooled motor controller, with a bus capacitor specification of 450V / 1000μF film capacitor. Preliminary preparation and parameter calibration were performed. On an experimental bench, the equivalent series resistance (ESR) and dielectric loss tangent of this type of capacitor were measured at different temperatures (-40°C to 105°C) and frequencies (10Hz to 100kHz). Generate a lookup table. Apply a constant power load (e.g., 60W) to the capacitor, record the temperature response curves at multiple points on the casing, and use the system identification toolkit to fit the initial thermal resistance parameters of the layered heat conduction equivalent model. and initial heat capacity parameters The thermal resistance parameters from the capacitor casing to the environment were calibrated on a wind tunnel and liquid-cooled test bench at different coolant flow rates (0.5 L / min to 10 L / min). The curve shows the change. During the online operation process, while the vehicle is in motion, the motor controller performs data acquisition and reads the phase current parameters during each interrupt cycle. , , Insulated-gate bipolar transistor temperature as ambient temperature Coolant flow rate Ripple calculation is performed based on the power switch state parameters ( , , ) and phase current parameters ( , , ), calculate the DC side current of the inverter and the battery output current The difference is used to obtain the capacitor ripple current. Find the capacitor ripple current. The effective value of the ripple current is obtained by calculating the effective value of the current. Next, loss calculation is performed, and the temperature is estimated based on the previous cycle. Using the current motor fundamental frequency, interpolate the first equivalent series resistance value and the dielectric loss tangent value to calculate the capacitor power loss. Adjust the parameters according to the coolant flow rate. Query the pre-stored mapping table and update the resistance parameters in the thermal network. (correspond If the equivalent series resistance value identification trigger condition is met, such as the current driving time being 10 minutes or more, online equivalent series resistance value identification will be performed, and the aging coefficient will be updated. And correct subsequent capacitor power losses. Next, the model is solved, and the corrected model is obtained. Substitute the model parameters into the discrete state equations to calculate the new temperature rise state vector. This, in turn, outputs the capacitor core temperature. And perform thermal management to determine... Within the specified temperature range, corresponding normal, warning, or derating operations are performed. Through the above process, this application achieves continuous, accurate, and adaptive monitoring and management of the bus capacitor core temperature.

[0152] Figure 4 This is a schematic diagram of a capacitor power loss determination process according to an embodiment of this application, as shown below. Figure 4 As shown, the inverter DC-side current is determined based on phase current parameters and power switch status parameters; the capacitor ripple current is determined based on the inverter DC-side current and battery output current; and the effective value of the ripple current is determined based on the capacitor ripple current.

[0153] Figure 5 This is a schematic diagram of an optional capacitor temperature determination process according to an embodiment of this application, as shown below. Figure 5As shown, the electrical signal parameters of the circuit system containing the capacitor are obtained. Based on the electrical signal parameters, the capacitor power loss is determined. Based on the capacitor power loss, and the thermal resistance and thermal capacitance parameters corresponding to each heat conduction equivalent layer, the step response parameters of the layered heat conduction equivalent model in the time domain are determined; based on the step response parameters, the capacitor core temperature is determined. Based on the step response parameters, the state transition matrix, and the input gain matrix, the temperature rise state vector corresponding to each heat conduction equivalent layer is determined; based on the temperature rise state vector and the ambient temperature of the circuit system, the capacitor core temperature is determined.

[0154] The technical solution proposed in this application achieves at least the following technical effects: Lifespan prediction and data recording. The system continuously records the cumulative thermal stress of the capacitor, such as the operating time above a certain temperature. Combining linear cumulative damage theory or more complex lifespan models, it assesses the remaining lifespan of the capacitor online, providing data support for predictive maintenance. High estimation accuracy and real-time performance. Employing a fourth-order dynamic thermal network, it accurately describes the entire process of heat generation and dissipation, accurately tracking lagging core temperature changes, far superior to shell temperature measurement and low-order models. Good adaptability and robustness. By introducing online corrections for cooling conditions and aging states, the model can automatically adapt to changes in vehicle operating conditions and the performance degradation of components, ensuring the accuracy of the estimation results throughout the entire lifespan. Low cost and high reliability. Implemented based on the existing hardware resources of the motor controller, eliminating the need for dedicated temperature sensors and their wiring, simplifying the system structure and improving overall reliability. Achieving proactive safety and predictive maintenance. Based on accurate core temperature estimation, it can achieve advanced overheat protection and intelligent derating, avoiding capacitor thermal failure. Simultaneously, it provides important basis for system health status monitoring and lifespan prediction, promoting the transformation of maintenance mode from passive response to proactive prediction.

[0155] According to another aspect of the embodiments of this application, a capacitor temperature determination device is also provided. This device can execute the capacitor temperature determination method of the above embodiments. The specific implementation method and preferred application scenarios are the same as those of the above embodiments, and will not be repeated here.

[0156] Figure 6 This is a schematic diagram of a capacitor temperature determination device according to an embodiment of this application, as shown below. Figure 6 As shown, the device includes the following: an acquisition module 602, a first determination module 604, and a second determination module 606.

[0157] The acquisition module 602 is used to acquire the electrical signal parameters of the circuit system in which the capacitor is located; the first determination module 604 is used to determine the capacitor power loss based on the electrical signal parameters; and the second determination module 606 is used to determine the capacitor core temperature based on the layered thermal conduction equivalent model and the capacitor power loss, wherein the layered thermal conduction equivalent model is used to characterize the equivalent thermal resistance and thermal capacity model obtained by structurally layering the thermal conduction process of the capacitor.

[0158] In the case where the circuit system is an electronic control unit and the capacitor is a bus capacitor, the first determining module is also used to determine the phase current parameters and power switch status parameters of the electronic control unit based on the electrical signal parameters; and to determine the capacitor power loss based on the phase current parameters and power switch status parameters.

[0159] The first determining module is further used to determine the effective value of the ripple current based on the phase current parameters and the power switch state parameters, wherein the effective value of the ripple current is used to represent the effective value of the ripple current provided by the capacitor; and to determine the capacitor power loss based on the effective value of the ripple current, the first equivalent series resistance value of the capacitor and the dielectric loss tangent value.

[0160] The first determining module is further configured to determine the inverter DC-side current based on phase current parameters and power switch state parameters, wherein the inverter DC-side current is used to represent the DC current value flowing into the inverter DC side of the electronic control unit; and to determine the effective value of the ripple current based on the inverter DC-side current and the battery output current, wherein the battery output current is used to represent the DC current value output by the battery in the electronic control unit.

[0161] The first determining module is also used to determine the capacitor ripple current based on the difference between the inverter DC side current and the battery output current, wherein the capacitor ripple current is used to represent the ripple current value provided by the capacitor; within the target control cycle, the root mean square value of the capacitor ripple current is calculated to obtain the effective value of the ripple current.

[0162] The first determining module is further configured to acquire the historical temperature of the capacitor core and the characteristic frequency of the ripple current, wherein the historical temperature of the capacitor core represents the temperature of the capacitor core determined in at least one historical control cycle, and the characteristic frequency of the ripple current represents the frequency component corresponding to the ripple current; based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the temperature-frequency mapping relationship of the resistance, determine the first equivalent series resistance value, wherein the temperature-frequency mapping relationship of the resistance is used to represent the mapping relationship of the fitted resistance value with the two-dimensional parameters of temperature and frequency; and based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the temperature-frequency mapping relationship of the loss, determine the dielectric loss tangent value, wherein the temperature-frequency mapping relationship of the loss is used to represent the mapping relationship of the fitted loss tangent with the two-dimensional parameters of temperature and frequency.

[0163] The layered heat conduction equivalent model includes at least two heat conduction equivalent layers: a core-to-inner shell heat conduction equivalent layer, an inner shell-to-outer shell heat conduction equivalent layer, an outer shell-to-heat radiator heat conduction equivalent layer, and a heat radiator-to-ambient heat conduction equivalent layer. The second determining module is also used to determine the step response parameters of the layered heat conduction equivalent model in the time domain based on the capacitor power loss and the thermal resistance and thermal capacity parameters corresponding to each heat conduction equivalent layer; and to determine the capacitor core temperature based on the step response parameters.

[0164] The second determining module is further used to determine the temperature rise state vector corresponding to each heat conduction equivalent layer based on the step response parameters, the state transition matrix, and the input gain matrix. The state transition matrix is ​​determined based on the thermal resistance parameters and the thermal capacity parameters, the thermal state evolution characteristic matrix is ​​determined based on the thermal resistance parameters and the thermal capacity parameters, and the weighted contribution matrix of power loss to temperature rise is determined based on the temperature rise state vector.

[0165] The second determining module is also used to determine the capacitor core temperature based on the temperature rise state vector and the ambient temperature of the circuit system.

[0166] The target conduction equivalent layer includes the heat conduction equivalent layer from the shell to the heat sink and the heat conduction equivalent layer from the heat sink to the environment. When the layered heat conduction equivalent model includes the target conduction equivalent layer and the heat sink used in the circuit system is a liquid-cooled heat sink, the second determining module is also used to adjust the initial thermal resistance parameter corresponding to the target conduction equivalent layer based on the coolant flow rate of the liquid-cooled heat sink to obtain the thermal resistance parameter corresponding to the target conduction equivalent layer.

[0167] The second determining module is further used to obtain the aging coefficient of the capacitor, wherein the aging coefficient is used to characterize the degree of aging of the capacitor; adjust the capacitor power loss based on the aging coefficient to obtain the adjusted capacitor power loss; adjust the thermal resistance parameter and thermal capacity parameter corresponding to each heat conduction equivalent layer in the layered heat conduction equivalent model based on the aging coefficient to obtain the adjusted layered heat conduction equivalent model; and determine the capacitor core temperature based on the adjusted capacitor power loss and the adjusted layered heat conduction equivalent model.

[0168] In the case where the circuit system is an electronic control unit and the capacitor is a bus capacitor, the second determining module is further configured to, in response to receiving a calibration command, inject a common-mode voltage signal of a preset amplitude into the inverter in the electronic control unit, and collect the ripple component voltage parameters and ripple component current parameters corresponding to the target ripple current generated on the DC bus; determine the second equivalent series resistance value based on the ripple component voltage parameters and ripple component current parameters; and determine the aging coefficient based on the second equivalent series resistance value and the first equivalent series resistance value.

[0169] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of the relevant data must comply with the relevant laws, regulations and standards of the relevant countries and regions, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0170] According to another aspect of the embodiments of this application, a vehicle is also provided, including: a memory storing an executable program; and a processor for running the program, wherein the program executes the methods in various embodiments of this application when it runs.

[0171] The aforementioned memory can refer to devices inside a computer used to store data and programs, including RAM, hard disks, etc. RAM can be used to temporarily store running programs and data, while hard disks can be used to store programs and data long-term. Memory enables the computer to read and write data and execute programs. The aforementioned processor is responsible for executing instructions in computer programs and performing data processing. It can also be responsible for controlling and executing various operations, including arithmetic operations, logical operations, and data transmission.

[0172] According to another aspect of the embodiments of this application, a computer-readable storage medium is also provided, the computer-readable storage medium including a stored executable program, wherein, when the executable program is running, it controls the device where the computer-readable storage medium is located to perform the methods of various embodiments of this application.

[0173] The aforementioned computer storage media can refer to the media used in computer memory to store certain discontinuous physical quantities. Computer storage media mainly include semiconductors, magnetic cores, magnetic drums, magnetic tapes, laser discs, etc. Computer-readable storage media include stored programs, which can be a set of instructions that a computer can recognize and execute, running on an electronic computer to meet certain information needs.

[0174] According to another aspect of the embodiments of this application, a computer program product is also provided, including a computer program that, when executed by a processor, implements the methods of various embodiments of this application.

[0175] The aforementioned computer program products can refer to software programs that have been written, tested, and released, and can run on computers or other devices. Computer program products can include application programs, operating systems, utility software, etc., used to achieve specific functions or solve specific problems.

[0176] According to another aspect of the embodiments of this application, a computer program product is also provided, including a non-volatile computer-readable storage medium storing a computer program, which, when executed by a processor, implements the methods in various embodiments of this application.

[0177] The aforementioned non-volatile computer-readable storage medium can refer to a medium for storing data. Non-volatile computer-readable storage media can retain data without loss when power is off and can be used to store long-term data, such as operating systems, applications, and user files. Non-volatile storage media can include hard disk drives, solid-state drives, optical disks, and flash memory storage devices, etc.

[0178] According to another aspect of the embodiments of this application, a computer program is also provided, which, when executed by a processor, implements the methods of the various embodiments of this application.

[0179] The aforementioned computer program can refer to a set of instructions used to tell the computer to perform specific tasks or operations. Computer programs can be written by programmers using specific programming languages ​​and can include algorithms, data structures, logic, and control flow. Computer programs can be used for a variety of purposes, including application software, operating systems, etc.

[0180] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0181] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0182] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0183] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0184] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard drive, magnetic disk, or optical disk.

[0185] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for determining the temperature of a capacitor, characterized in that, include: Obtain the electrical signal parameters of the circuit system where the capacitor is located; Based on the electrical signal parameters, determine the capacitor power loss; Based on the layered thermal conduction equivalent model and the power loss of the capacitor, the temperature of the capacitor core is determined. The layered thermal conduction equivalent model is used to characterize the equivalent thermal resistance and thermal capacity model obtained by structurally layering the thermal conduction process of the capacitor.

2. The method for determining capacitor temperature according to claim 1, characterized in that, When the circuit system is an electronic control unit and the capacitor is a bus capacitor, the capacitor power loss is determined based on the electrical signal parameters, including: Based on the electrical signal parameters, the phase current parameters and power switch status parameters of the electronic control unit are determined; The capacitor power loss is determined based on the phase current parameters and the power switch state parameters.

3. The method for determining capacitor temperature according to claim 2, characterized in that, Determining the capacitor power loss based on the phase current parameters and the power switch state parameters includes: Based on the phase current parameters and the power switch state parameters, the effective value of the ripple current is determined, wherein the effective value of the ripple current is used to represent the effective value of the ripple current provided by the capacitor. Based on the effective value of the ripple current, the first equivalent series resistance value and the dielectric loss tangent value corresponding to the capacitor, the power loss of the capacitor is determined.

4. The method for determining capacitor temperature according to claim 3, characterized in that, Based on the phase current parameters and the power switch state parameters, the effective value of the ripple current is determined, including: Based on the phase current parameters and the power switch state parameters, the inverter DC side current is determined, wherein the inverter DC side current is used to represent the DC current value flowing into the inverter DC side of the electronic control unit; The effective value of the ripple current is determined based on the inverter DC side current and the battery output current, wherein the battery output current is used to represent the DC current value output by the battery in the electronic control unit.

5. The method for determining capacitor temperature according to claim 4, characterized in that, The effective value of the ripple current is determined based on the inverter DC-side current and the battery output current, including: The capacitor ripple current is determined based on the difference between the inverter DC side current and the battery output current, wherein the capacitor ripple current is used to represent the ripple current value provided by the capacitor. Within the target control cycle, the root mean square value of the capacitor ripple current is calculated to obtain the effective value of the ripple current.

6. The method for determining capacitor temperature according to claim 3, characterized in that, The method further includes: The historical temperature of the capacitor core and the characteristic frequency of the ripple current are obtained, wherein the historical temperature of the capacitor core is used to represent the temperature of the capacitor core determined by at least one historical control cycle, and the characteristic frequency of the ripple current is used to represent the frequency component corresponding to the ripple current. Based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the temperature-frequency mapping relationship of the resistance, the first equivalent series resistance value is determined, wherein the temperature-frequency mapping relationship of the resistance is used to represent the mapping relationship of the fitted resistance value with the two-dimensional parameters of temperature and frequency. Based on the historical temperature of the capacitor core, the characteristic frequency of the ripple current, and the temperature-frequency mapping relationship of the loss, the dielectric loss tangent value is determined, wherein the temperature-frequency mapping relationship is used to represent the fitted mapping relationship of the loss tangent with the two-dimensional parameters of temperature and frequency.

7. The method for determining capacitor temperature according to any one of claims 1 to 6, characterized in that, The layered heat conduction equivalent model includes at least two heat conduction equivalent layers: the heat conduction equivalent layer from the core interior to the inner shell, the heat conduction equivalent layer from the inner shell to the outer shell, the heat conduction equivalent layer from the outer shell to the heat sink, and the heat conduction equivalent layer from the heat sink to the environment. Based on the layered heat conduction equivalent model and the capacitor power loss, the capacitor core temperature is determined, including: Based on the capacitor power loss, and the thermal resistance and thermal capacity parameters corresponding to each thermal conduction equivalent layer, the step response parameters of the layered thermal conduction equivalent model in the time domain are determined. The temperature of the capacitor core is determined based on the step response parameters.

8. The method for determining capacitor temperature according to claim 7, characterized in that, Determining the capacitor core temperature based on the step response parameters includes: Based on the step response parameters, state transition matrix, and input gain matrix, the temperature rise state vector corresponding to each heat conduction equivalent layer is determined, wherein the state transition matrix is ​​determined based on the thermal resistance parameter and the heat capacity parameter, the thermal state evolution characteristic matrix is ​​determined based on the thermal resistance parameter and the heat capacity parameter, and the power loss weighted contribution matrix to the temperature rise is determined based on the thermal resistance parameter and the heat capacity parameter. The temperature of the capacitor core is determined based on the temperature rise state vector.

9. The method for determining capacitor temperature according to claim 8, characterized in that, Determining the capacitor core temperature based on the temperature rise state vector includes: The temperature of the capacitor core is determined based on the temperature rise state vector and the ambient temperature of the circuit system.

10. The method for determining capacitor temperature according to claim 7, characterized in that, The target conduction equivalent layer includes the heat conduction equivalent layer from the outer casing to the heat sink and the heat conduction equivalent layer from the heat sink to the environment; when the layered heat conduction equivalent model includes the target conduction equivalent layer and the heat sink used in the circuit system is a liquid-cooled heat sink, the method further includes: Based on the coolant flow rate of the liquid cooler, the initial thermal resistance parameter corresponding to the target conductive equivalent layer is adjusted to obtain the thermal resistance parameter corresponding to the target conductive equivalent layer.

11. The method for determining capacitor temperature according to any one of claims 1 to 6, characterized in that, The method further includes: Obtain the aging coefficient of the capacitor, wherein the aging coefficient is used to characterize the degree of aging of the capacitor; The capacitor power loss is adjusted based on the aging coefficient to obtain the adjusted capacitor power loss. Based on the aging coefficient, the thermal resistance and thermal capacity parameters corresponding to each thermal conduction equivalent layer in the layered thermal conduction equivalent model are adjusted to obtain the adjusted layered thermal conduction equivalent model. The temperature of the capacitor core is determined based on the adjusted capacitor power loss and the adjusted layered heat conduction equivalent model.

12. The method for determining capacitor temperature according to claim 11, characterized in that, When the circuit system is an electronic control unit and the capacitor is a bus capacitor, obtaining the aging coefficient of the capacitor includes: In response to receiving a calibration command, a common-mode voltage signal of preset amplitude is injected into the inverter in the electronic control unit, and the ripple component voltage parameters and ripple component current parameters corresponding to the target ripple current generated on the DC bus are collected. The second equivalent series resistance value is determined based on the ripple component voltage parameter and the ripple component current parameter. The aging coefficient is determined based on the second equivalent series resistance value and the first equivalent series resistance value.

13. A device for determining capacitor temperature, characterized in that, include: The acquisition module is used to acquire the electrical signal parameters of the circuit system in which the capacitor is located; The first determining module is used to determine the capacitor power loss based on the electrical signal parameters; The second determining module is used to determine the capacitor core temperature of the capacitor based on the layered thermal conduction equivalent model and the capacitor power loss, wherein the layered thermal conduction equivalent model is used to characterize the equivalent thermal resistance and thermal capacity model obtained by structurally layering the thermal conduction process of the capacitor.

14. An electronic device, characterized in that, include: Memory, which stores executable programs; A processor for running the program, wherein the program, when running, executes the method for determining the capacitor temperature according to any one of claims 1 to 12.

15. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored executable program, wherein, when the executable program is executed, it controls the device on which the storage medium is located to perform the method for determining the capacitor temperature according to any one of claims 1 to 12.

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