A method and apparatus for measuring the charging and discharging capacity of an electric vehicle

Abstract

This invention relates to the field of electric vehicle charging and discharging technology, specifically disclosing a method and apparatus for measuring the charging and discharging capacity of an electric vehicle. The method is based on a shunt installed inside the electric vehicle and connected to a PZT ceramic body. The method includes: acquiring the charging current and charging voltage division values ​​using the shunt; obtaining the charge signal output by the PZT ceramic body, wherein the shunt deforms due to heat generated during sampling, causing the PZT ceramic body to output a charge signal; calculating the compensated charging current based on the charge signal and the charging current; and calculating the charging and discharging capacity based on the compensated charging current and the charging voltage division value. This invention connects the PZT ceramic body to the manganese copper sheet of the manganese copper shunt. When the shunt is working, the piezoelectric effect of the PZT ceramic body compensates for the micro-resistance offset error of the manganese copper shunt, achieving the purpose of eliminating errors and accurate measurement.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle charging and discharging technology, and in particular to a method and apparatus for measuring the charging and discharging capacity of an electric vehicle. Background Technology

[0002] Existing standard AC charging systems for electric vehicles use AC meters within the charging station for billing. However, due to energy loss points along the route from the meter to the vehicle battery—including AC relays, charging cables, the charging adapter, and the on-board charger (OBC)—the billed amount may differ from the actual battery charge. Furthermore, standard DC charging systems, with their AC-side metering, cannot measure the energy lost during the AC-DC conversion process. Therefore, billing is inaccurate for charging users. While advanced SiC semiconductor PCS converters can achieve efficiencies exceeding 97%, when fast and ultra-fast chargers are directly connected to the vehicle battery, energy is transmitted DC. In this case, accurate billing on the DC side of the electric vehicle is clearly necessary.

[0003] According to regulations, the rated battery current (continuous maximum operating current) of a DC charging interface ranges from 300A to 800A. For metering high currents, shunts are typically used. However, if the shunt resistance is high, the power consumption will be extremely large. Therefore, shunts in charging stations are usually designed with a resistance of μΩ, and their volume is mostly several hundred cubic centimeters. However, the internal space of the charging socket in an electric vehicle is extremely limited, and modules such as the Battery Management System (BMS) and motor controller are highly integrated. To meet the requirements of lightweight and compact vehicle design and reduce current sampling costs, it is necessary to match a tiny sampling resistor value. Therefore, charging and discharging metering inside an electric vehicle requires the use of miniaturized shunts. However, miniaturized shunts lack active heat dissipation capabilities, and their temperature variation within their operating range is far greater than the rated operating environment, rendering existing compensation methods for shunts in charging stations unsuitable (due to excessive error). Summary of the Invention

[0004] This invention aims to solve the problem of large errors in the internal metering of charging and discharging quantities in electric vehicles. To this end, this invention provides a method and apparatus for measuring the charging and discharging quantities of electric vehicles.

[0005] This invention provides a method for measuring the charging and discharging capacity of an electric vehicle, based on a shunt installed inside the electric vehicle and connected to a PZT ceramic body. The technical solution adopted is as follows: The charging current and the divided voltage of the charging voltage are obtained using a shunt. The charge signal output by the PZT ceramic body is obtained, wherein the charge signal output by the PZT ceramic body is caused by the deformation of the shunt due to heat generated during sampling; The compensated charging current is calculated based on the charge signal and the charging current. The charge / discharge amount is calculated based on the compensated charging current and the voltage divider value of the charging voltage.

[0006] Furthermore, the shunt compensation is added to the charging current to obtain the compensated charging current; The formula for calculating the shunt compensation is: in, This is the compensation amount for the shunt. The charging current is measured by the shunt. The coefficient of linear expansion is 1 / 3. This refers to the charge signal output by the PZT ceramic body. This is the temperature difference-charge signal conversion coefficient.

[0007] Furthermore, when the shunt is a manganese-copper shunt, and the PZT ceramic body is a PZT5H ceramic sheet, and is attached to the central region of the upper surface of the resistive element of the manganese-copper shunt, the temperature difference-charge signal conversion coefficient is... .

[0008] Furthermore, by analyzing the CC / CP signal level, pulse width, and signal frequency characteristics during the charging handshake process, the charging and discharging state can be identified, and the charging and discharging quantity can be determined as either the charging quantity or the discharging quantity based on the charging and discharging state.

[0009] The present invention also provides a metering device for the charging and discharging of an electric vehicle, the technical solution of which is as follows: installed inside the electric vehicle, including: a power metering and monitoring module, a data processing and storage module, an encryption and decryption module and a wireless transmission module; The power metering and monitoring module is used to identify the charging and discharging status and measure the charging and discharging amount; wherein, the power metering and monitoring module is equipped with a shunt connected to a PZT ceramic body; when the shunt deforms due to heat generated by sampling, it causes the PZT ceramic body to output a charge signal, which is used to compensate for the current sampled by the shunt. The data processing and storage module is used to statistically analyze and record the charging and discharging power. The encryption / decryption module is used to encrypt the charging / discharging power data. The wireless transmission module is used to transmit data about the charging and discharging power levels.

[0010] Furthermore, the power metering and monitoring module can be configured as an AC metering module and an AC charging protocol monitoring module, or as a DC metering module and a DC charging protocol monitoring module, or as an AC metering module, an AC charging protocol monitoring module, a DC metering module and a DC charging protocol monitoring module. The AC metering module is used to measure the amount of charge and discharge during AC charging and discharging. The AC charging protocol monitoring module is used to identify the charging and discharging status of AC charging and discharging. The DC metering module is used to measure the amount of charge and discharge during DC charging and discharging. The DC charging protocol monitoring module is used to identify the charging and discharging status of DC charging and discharging.

[0011] Furthermore, the shunt is a manganese copper shunt; the PZT ceramic body is a PZT5H ceramic sheet, which is attached to the central area of ​​the upper surface of the resistive element of the manganese copper shunt.

[0012] Furthermore, it also includes a thermal status acquisition and cooling module, which is connected to the power metering and monitoring module. The ambient temperature acquisition unit of the thermal state acquisition and cooling module is arranged near the splitter and away from the direct blowing area of ​​the micro fan, and is used to obtain the ambient boundary temperature of the splitter. The micro fan of the thermal state acquisition and cooling module blows airflow along the length of the splitter over the surface of the resistor.

[0013] Furthermore, the power metering and monitoring module calculates the shunt thermal state index based on the charge signal output by the PZT ceramic body, the ambient temperature collected by the thermal state acquisition and cooling module, and the charging current collected by the shunt; then it calculates the resistance compensation coefficient to compensate for the nominal resistance of the shunt; then it calculates the compensated current, and combines it with the charging voltage division value collected by the shunt to calculate the charging power.

[0014] Furthermore, the power metering and monitoring module determines the driving quantity of the micro fan based on the thermal state index of the shunt and transmits it to the thermal state acquisition and cooling module to realize the control of the micro fan.

[0015] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: This invention fixes a PZT ceramic body to the manganese copper sheet of a manganese copper shunt. During shunt operation, the piezoelectric effect of the PZT ceramic body compensates for the micro-resistance offset error of the manganese copper shunt, achieving error elimination and accurate measurement. Its advantages lie in improved accuracy and reduced cost. This invention can increase the rated power of the manganese copper shunt while maintaining rated accuracy, and significantly reduce the size and weight of the manganese copper shunt in the same current metering application scenarios, making it suitable for built-in charging and discharging metering in electric vehicles.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the metering device provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the connection between the PZT ceramic body and the shunt provided by the present invention.

[0020] Figure 3 This is a circuit diagram of the charge / discharge measurement provided by the present invention.

[0021] Figure 4 This is a flowchart of the measurement method provided by the present invention.

[0022] Figure label: 1. DC metering module; 2. DC charging protocol monitoring module; 3. AC metering module; 4. AC charging protocol monitoring module; 5. Data processing and storage module; 6. Encryption and decryption module; 7. Wireless transmission module. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but should not be used to limit the scope of this invention.

[0024] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0025] The following is combined with Figures 1 to 4The present invention will be further described in detail below, providing a method and apparatus for measuring the charging and discharging quantities of an electric vehicle: Example 1 In this embodiment, as Figure 1 As shown, a metering device for the charging and discharging of an electric vehicle is provided, installed inside the electric vehicle. It includes a power metering and monitoring module, a data processing and storage module 5, an encryption / decryption module 6, and a wireless transmission module 7. Each of these modules measures the actual charging and discharging amounts generated by the AC and DC sockets during the charging process in real time and stores and records the power consumption. The data is encrypted and decrypted according to the application scenario and communicated with other modules, systems, and platforms via wireless communication.

[0026] This embodiment is installed inside the electric vehicle, specifically between the AC charging gun socket and the OBC on-board charger, or between the DC charging gun socket and the BMS battery management system, to monitor and measure the charging and discharging amount of the electric vehicle.

[0027] The power metering and monitoring module is used to identify the charging and discharging status and measure the charging and discharging amount. Depending on the specific DC and AC charging and discharging conditions of the electric vehicle, the power metering and monitoring module in this embodiment can be configured as an AC metering module 3 and an AC charging protocol monitoring module 4, or as a DC metering module 1 and a DC charging protocol monitoring module 2, or as an AC metering module, an AC charging protocol monitoring module, a DC metering module, and a DC charging protocol monitoring module.

[0028] The AC metering module is used to measure the charge and discharge amounts during AC charging and discharging. It employs electronic circuitry and chips based on non-isolated AC measurement using direct sampling resistors. With the first voltage divider resistor The actual charging and discharging capacity of the AC gun socket is accurately measured.

[0029] The AC charging protocol monitoring module is used to identify the charging and discharging status of AC charging and discharging. This module is based on electronic circuits and chips that analyze the pulse signals of the charging communication handshake signal CC / CP (Connection Confirmation / Control Guidance). It identifies the charging and discharging status by analyzing the characteristics of the CC / CP signal level, pulse width, and signal frequency during the AC charging handshake process.

[0030] A DC metering module is used to measure the amount of charge and discharge during DC charging and discharging. The DC metering module is an electronic circuit and chip based on direct sampling, non-isolated DC measurement, using a sampling resistor on the high-voltage side. Low voltage side sampling resistor With the second voltage divider resistor Accurately measure the actual charging and discharging quantity of the DC gun socket.

[0031] The DC charging protocol monitoring module is used to identify the charging and discharging status of DC charging and discharging. This module is based on electronic circuits and chips that analyze the differential signals of CAN communication during charging communication. It parses CAN communication messages during the DC charging handshake process to obtain the status of the charger CCU and battery pack BMS system, including VID, requested voltage, requested current, and other characteristics to identify the charging and discharging status.

[0032] The data processing and storage module is used to statistically analyze and record the charging and discharging power. This module receives, processes, and stores data from the AC metering module, AC charging protocol monitoring module, DC metering module, and DC charging protocol monitoring module. By integrating these functional modules, the module accurately understands the charging and discharging status and ports of the electric vehicle. Furthermore, by combining the measured power data from both the AC and DC terminals, it precisely measures and records the total power consumption of the electric vehicle.

[0033] The encryption / decryption module is used to encrypt the charging and discharging power data. It utilizes hardware-based encryption circuits and chips, supporting methods such as SM encryption / decryption. A public key issued by a cryptographic authority is pre-stored. During data transmission, parameter configuration, and initialization, an encryption request is generated based on a random number and the built-in public key to verify the peer's response.

[0034] The wireless transmission module is used to transmit charging and discharging power data. It is an electronic circuit and chip capable of both local and remote wireless communication. Local wireless communication refers to the communication method where, via a handheld terminal near the electric vehicle where the device is installed, the charging and discharging power data within the device is read and written, and device parameters are configured. Remote wireless communication refers to the communication method where, via a GSM network, the power data within the metering module is read and written, and device parameters are configured, with a remote master platform.

[0035] The power metering requires 0.1% accuracy (Class S). Due to the large dynamic range of the actual current during AC or DC charging, ordinary current transformers and Hall effect sensors cannot meet the requirements. Current sampling typically uses a shunt (installed in both AC and DC metering modules) to collect current and voltage data. The shunt is made of metals with relatively stable temperature resistivity, such as manganese copper or chromium copper, and possesses a relatively stable precision micro-resistance, generating a voltage drop when current flows through it. This sampled voltage is measured by an amplifier circuit and converted into the actual current according to Ohm's law. Under 1000kW ultra-fast charging conditions, the maximum current can reach 1200A. The manganese copper sheet in the shunt undergoes slight deformation due to power consumption under continuous current, causing changes in the current-carrying path and affecting the calibrated resistance value, leading to a deterioration in sampling accuracy.

[0036] like Figure 2As shown, the shunt used in this embodiment is a novel strapdown fixed PZT ceramic shunt. It utilizes the piezoelectric effect of the PZT ceramic to sense the dynamic error of the shunt, thereby improving metering accuracy. This embodiment employs an interconnected structure of shunts and PZT ceramics. When the manganese-copper shunt undergoes a slight deformation due to heat generated during sampling, it causes the PZT ceramic to generate a voltage output. Based on the charge signal output by the PZT ceramic, the shunt compensation amount (current) can be calculated to compensate for the current sampled by the manganese-copper shunt.

[0037] In this embodiment, the shunt is a manganese copper shunt, and the PZT ceramic body is a PZT5H ceramic sheet, which is attached to the central area of ​​the upper surface of the resistive element of the manganese copper shunt.

[0038] When the power metering and monitoring module has both DC and AC charge / discharge metering functions, its circuit structure is as follows: Figure 3 As shown. Taking charging as an example, the electricity metering process is explained as follows: AC charging power metering: Shunt unit collects AC charging current. PZT ceramic body acquisition shunt AC compensation amount Both are compensated by AC_ADD to generate AC charging current. AC charging voltage divider value (Acquired by the shunt) AC measurement voltage value is generated by the amplifier. ; and AC real-time power is generated by the multiplier AC_MUX The metering circuit has a sampling rate of 12.8kHz. Accumulate points to obtain AC charging power. .

[0039] DC charging current measurement: Shunt unit collects DC charging current. PZT ceramic body acquisition shunt DC compensation amount Both are compensated by DC_ADD to generate DC charging current. DC charging voltage divider value (Acquired by the shunt) The DC measurement voltage value is generated by the amplifier. ; and DC real-time power is generated by the multiplier DC_MUX The metering circuit has a sampling rate of 12.8kHz. Integrate to obtain the DC charging power. .

[0040] When the power metering and monitoring module only has DC or AC charging and discharging measurement functions, it adopts a partial... Figure 3The circuit structure.

[0041] The data processing and storage module statistically analyzes the charging and discharging power. The process is as follows: AC charging power. DC charging capacity The final measured amount of electricity is obtained through the adder. During this calculation process, the AC charging protocol monitoring module and the DC charging protocol monitoring module identify the charging and discharging status. During charging, and Take a positive value, during discharge, and Take the negative value.

[0042] When a large current passes through the shunt in the AC and DC metering modules, a resistive heating effect is generated, which causes deformation of the metal. Although manganese copper or chromium copper has a low temperature resistivity, the deformation causes a shift in the equivalent micro-resistance. This invention innovatively fixes a PZT ceramic body to the manganese copper sheet of the manganese copper shunt. When the shunt is working, the piezoelectric effect of the PZT ceramic body compensates for the micro-resistance shift error of the manganese copper shunt, achieving error elimination and accurate measurement. Its advantages are improved accuracy and reduced cost. This invention can increase the rated power of the manganese copper shunt while maintaining rated accuracy, and significantly reduce the size and weight of the manganese copper shunt in the same current metering application scenario, making it suitable for built-in charging and discharging metering in electric vehicles.

[0043] Example 2 In this embodiment, as Figure 4 As shown, a method for measuring the charging and discharging capacity of an electric vehicle is provided, based on a shunt installed inside the electric vehicle and connected to a PZT ceramic body, including the following steps: The charging current and the divided voltage of the charging voltage are obtained using a shunt. The charge signal output by the PZT ceramic body is obtained, wherein the charge signal output by the PZT ceramic body is caused by the deformation of the shunt due to heat generated during sampling; The compensated charging current is calculated based on the charge signal and the charging current. The charge / discharge amount is calculated based on the compensated charging current and the voltage divider value of the charging voltage.

[0044] In this embodiment, the shunt compensation amount is calculated based on the charge signal and charging current. The calculation formula is as follows: in, This is the compensation amount for the shunt. The charging current is measured by the shunt. The coefficient of linear expansion is 1 / 3. This refers to the charge signal output by the PZT ceramic body. This is the temperature difference-charge signal conversion coefficient.

[0045] The shunt compensation is added to the charging current to obtain the compensated charging current; the compensated charging current is multiplied by the charging voltage divider value to obtain the charge / discharge amount.

[0046] The charge / discharge quantity is specifically the charging capacity or the discharging capacity. The charging / discharging state is identified by analyzing the characteristics such as the CC / CP signal level, pulse width, and signal frequency during the charging handshake process, and then determined.

[0047] When the shunt is a manganese-copper shunt, and the PZT ceramic body is a PZT5H ceramic sheet, bonded to the central region of the upper surface of the resistive element of the manganese-copper shunt, the temperature difference-charge signal conversion coefficient is: The verification process is as follows: 1. Experimental and analytical conditions: A 600A range manganese copper shunt was used to measure the DC charging gun current, and a PZT ceramic body was used to compensate for the sampling current by utilizing the thermal strain of the manganese copper body.

[0048] (1) Mechanical parameters of manganese-copper shunt: Manganese bronze resistor element dimensions: 50mm × 50mm × 3mm (length × width × thickness), resistance value : ; Current direction: along the length (50mm); Cross-sectional area : ; Effective length : (The total length is consistent with 50mm, and the copper pin soldering area at both ends is approximately 3.7mm).

[0049] (2) Parameters of manganese-copper alloy materials: resistivity : ; Temperature coefficient of resistance : ; Coefficient of linear expansion: ; Maximum long-term operating temperature: 170℃.

[0050] (3) Working environment parameters: Ambient temperature : ; Power consumption under 600A rated operating conditions : ; Design temperature rise under 600A rated operating conditions : Approximately 90℃ (operating temperature approximately 130℃, 0.5-class shunt specification); Equivalent thermal conductivity: ; The equivalent heat transfer coefficient, For effective heat transfer area.

[0051] (4) Specifications of PZT ceramic body: Material: PZT5H; Dimensions: 40mm×40mm×0.3mm (cover the manganin resistor section as much as possible, leaving a 5mm margin on all four sides); Arrangement method: Single piece, pasted on the upper surface of manganin resistor, covering the central area of ​​the effective resistance segment; piezoelectric constant: ; The transverse piezoelectric strain constant is The longitudinal piezoelectric strain constant; elastic modulus : ; Curie temperature : ; Temperature coefficient: The range of variation is approximately .

[0052] 2. Temperature rise model of manganese-copper shunt: Steady-state temperature rise : I represents the current value; Operating temperature : ; Verification: When I=600A, , .

[0053] It matches the model simulation expectations.

[0054] 3. Derivation of the error equation: (1) Physical mechanism: Joule heating is generated when current flows through the shunt, causing the temperature of the manganin resistor to rise by ΔT. This temperature rise causes two effects: Resistivity variation of manganese-copper alloy : This is the direct source of measurement error; Thermal expansion of manganese-copper alloys causes strain : , is a perceptible physical quantity of PZT. The coefficient of linear expansion; The PZT ceramic body is bonded to the surface of the manganese-copper body, directly sensing the thermal expansion strain ε, and outputting a charge signal proportional to the strain. By inferring ΔT from the charge signal of the PZT ceramic body, the resistance temperature drift of the shunt can be compensated.

[0055] (2) Error equation without PZT compensation: Without PZT compensation, the resistance drift of the manganese-copper resistor due to temperature rise is entirely reflected as measurement error. Substitute : (100%) Right now: (%), the error is proportional to the square of the current and proportional to the temperature rise caused by Joule heating. The measurement error is for a manganese-copper shunt without PZT compensation.

[0056] (3) Error equation with PZT compensation: PZT compensation principle: PZT measures strain Then we can deduce the reverse. Receive compensation The residual error after PZT compensation depends on the accuracy of PZT strain measurement and is mainly limited by the following factors: (a) PZT piezoelectric constant Temperature dependence: exist Within the range of ±8%, after two-point calibration and correction, the residual nonlinear error is approximately 3%. (b) Strain transfer loss of the adhesive layer: The adhesive layer between PZT and the manganese copper matrix results in incomplete strain transfer, with a strain transfer efficiency of approximately 97%–99% and an uncertainty of approximately 2%. Two-factor RSS synthesis: ; To compensate for residual factors.

[0057] That is, PZT compensation can eliminate about 96% of the temperature drift error, with a residual 4%.

[0058] Measurement error of manganese-copper shunt with PZT compensation for: Convert to percentage: .

[0059] (4) PZT compensation ratio: Compensation ratio: In other words, PZT compensation reduces thermal drift error to 1 / 25 of its original value, regardless of the current magnitude.

[0060] (5) Signal-to-noise ratio of PZT signal: Charge output of a single PZT5H chip (40mm×40mm×0.3mm) under thermal expansion of a manganese-copper body: PZT electrode area : ; Thermal strain of manganese-copper body: ; PZT charge output per unit area under biaxial strain : Total charge output : Charge amplifier output (Feedback capacitor) ): That is, every 1℃ temperature rise generates 14.25mV output signal (charge signal), with an extremely high signal-to-noise ratio.

[0061] Under 600A rated operating conditions: , The output signal amplitude is much larger than the circuit noise, ensuring compensation accuracy.

[0062] This embodiment tested the full range (operating temperature). The error (from 40.0℃ to 130.0℃) is shown in Table 1. At 600A, the operating temperature is 130.0℃, which is within the long-term operating temperature range of manganese-copper alloy (≤170℃), meeting the rated operating condition design. The compensation ratio is constant at 25, determined by the PZT compensation residual factor δ=4%, and is independent of the current magnitude. At 0A, there is no temperature rise, no thermal drift error, and PZT compensation has no effect.

[0063] Table 1 This embodiment verifies the advantages of PZT compensation through the above process: (1) Constant error reduction: PZT compensation reduces thermal drift error to 1 / 25 of its original value (a 96% reduction), regardless of the current magnitude. This is because PZT directly senses thermal strain, and the compensation accuracy is independent of the temperature rise.

[0064] (2) The error growth rate is significantly reduced: the error growth rate without PZT is The error growth rate of PZT is... The growth rate decreased to 1 / 25 of its original value, and the error no longer deteriorated rapidly under high current.

[0065] (3) A qualitative leap in accuracy level: Without PZT: 600A, the error is 0.45%, which only meets the 0.5 level and has no accuracy margin; with PZT: 600A, the error is 0.018%, which meets the 0.05 level and has an extremely ample accuracy margin. This is equivalent to improving the accuracy level of the shunt from 0.5 level to 0.05 level (a 10-fold improvement).

[0066] (4) Sufficient PZT signal strength: A single PZT outputs 1.425 nC of charge for every 1℃ temperature rise, and outputs 14.25 mV / ℃ after passing through a charge amplifier. The output is 1.283V under the 600A rated operating condition, which is much greater than the circuit noise, ensuring compensation accuracy.

[0067] (5) Advantages of single-piece large-area coverage: A single PZT covers the central area of ​​the manganese copper body (40mm×40mm), and measures the integral strain of the entire effective resistance section, naturally realizing the surface average measurement of the temperature field and avoiding the complexity of multi-point arrangement.

[0068] Since both AC and DC charging require separate measurement of the current in the AC and DC circuits, this method is applicable to both AC and DC. The difference between AC and DC lies in the rated current of the shunt (AC charging has a maximum rated current of 120A for a maximum of 13kW, so there is no need to select a 600A shunt). The error optimization scheme and compensation techniques are the same.

[0069] This embodiment can be implemented based on the electric vehicle charging and discharging measurement device described in Embodiment 1.

[0070] Example 3 This embodiment provides a metering device for the charging and discharging capacity of an electric vehicle. Based on Embodiment 1, a thermal state acquisition and cooling module is added, which is connected to the power metering and monitoring module. Specifically, the thermal state acquisition and cooling module is connected to both an AC metering module and a DC metering module.

[0071] The thermal state acquisition and cooling module includes an ambient temperature acquisition unit and a miniature fan. The ambient temperature acquisition unit is positioned near the shunt but away from the direct airflow area of ​​the miniature fan, used to acquire the ambient boundary temperature of the shunt. The ambient temperature serves as a boundary condition for the compensation model, participating in the calculation of the thermal state index along with the PZT charge signal to compensate for the hysteresis problem of single-point temperature sampling. The miniature fan is positioned so that airflow runs along the length of the shunt across the resistive surface, creating forced convection cooling.

[0072] The method in Example 2, which directly converts the shunt compensation amount using PZT charge signals, has stringent requirements regarding the consistency of the bonding process, the accuracy of material parameters, and the temperature dependence of PZT. This example uses offline calibration to directly establish an empirical mapping relationship between the characteristic values ​​of PZT charge and the temperature drift of the shunt. In this example, the PZT charge signal does not directly participate in the power calculation; instead, it serves as the raw input for thermal state sensing and is converted into a thermal state index. The thermal state index is used for both the calculation of the compensation current and the calculation of the fan drive quantity.

[0073] The calculation process for supplementing the sampling current using the charge signal output from the PZT ceramic body and the current ambient temperature acquired by the thermal state acquisition and cooling module includes: The thermal state index of the shunt is calculated based on the charge signal and ambient temperature, using the following formula: in, This is the thermal state index of the shunt in the current sampling period. For PZT charge signal weights, This refers to the charge signal output by the PZT ceramic body. Weights are estimated for Joule heating. The charging current is measured by the manganese-copper shunt. The nominal resistance of the shunt at the reference temperature. Assuming an ambient temperature weight, The current ambient temperature. This is for offline calibration reference temperature.

[0074] The resistance compensation coefficient is calculated based on the shunt's thermal state index. The calculation formula is as follows: in, This is the current resistance compensation coefficient. The constant term obtained through offline identification. The identification coefficient corresponding to the current thermal state index. The identification coefficient corresponding to the thermal state index of the previous cycle. This is the thermal state index of the shunt in the previous sampling period.

[0075] The equivalent resistance of the compensated shunt is calculated using the following formula: in, This is the current compensated equivalent resistance of the shunt. The nominal resistance of the shunt is at the reference temperature.

[0076] The equivalent resistance of the compensated shunt is calculated using the following formula: in, This is the current after compensation. Sample the current shunt voltage division value of the charging voltage.

[0077] The real-time power is calculated based on the current after compensation and the voltage divider value of the charging voltage; the charging capacity is obtained by integrating the real-time power based on a 12.8kHz sampling rate. The calculation methods for AC charging capacity and DC charging capacity are the same.

[0078] The fan drive quantity calculation process is as follows: The normalized adjustment of the fan's thermal state is determined based on the thermal state index of the shunt, and then the drive quantity of the micro fan is calculated. The calculation formula is as follows: in, For the current micro fan drive quantity, This is the minimum allowable drive quantity for the fan. This is the maximum allowable drive capacity of the fan. This is the normalized adjustment value for the fan's thermal state. in, The threshold for the fan to enter a regulated thermal state. The thermal threshold for full-scale fan adjustment. This is the amplitude limiting function.

[0079] Abnormal situation handling: When the PZT charge signal reaches the upper limit of the charge amplification unit range, the ambient temperature acquisition value is lost, the shunt sampling voltage exceeds the ADC input range, or the thermal state index exceeds the effective range of offline calibration, the calculation of the compensation coefficient is stopped; the current after compensation is calculated using the previous effective compensation coefficient, and the abnormal status is added to the uploaded data.

[0080] After the power metering and monitoring module completes the calculation of the charging power and the micro fan drive quantity, it transmits the charging power and the micro fan drive quantity to the data processing and storage module to store the calculated data; and transmits the micro fan drive quantity to the thermal status acquisition and cooling module to control the micro fan.

[0081] Offline calibration: thermal state weights ( , and ), compensation coefficient ( , and ) and fan threshold ( and The calibration is performed offline. The specific process is as follows: First, the nominal resistance of the shunt at a reference temperature is determined using a reference current source and a reference voltage measuring device. Then, under multiple DC current steps (covering 0%–120% of rated current), multiple ambient temperature points (covering 0℃–140℃), and multiple fan drive parameters (0%–100% duty cycle), the following data are simultaneously collected: PZT charge characteristic value, shunt sampling voltage, ambient temperature, and reference current value, constructing a calibration sample set. Based on this sample set, the thermal state weights, compensation coefficients, and fan thresholds are determined using least squares or table lookup fitting methods.

[0082] This embodiment utilizes PZT thermal state sensing and ambient temperature boundary to compensate for the lag problem of single-point temperature sampling; the driving force of the micro fan is obtained by limiting the thermal state index to avoid the disconnect between the heat dissipation structure and the compensation algorithm; the abnormal condition handling enables the system to maintain interpretable metering output even when the sensor is saturated or the sampling exceeds the limit.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the charging and discharging capacity of an electric vehicle, characterized in that, This is achieved using a shunt installed inside the electric vehicle and connected to a PZT ceramic body, including: The charging current and the divided voltage of the charging voltage are obtained using a shunt. The charge signal output by the PZT ceramic body is obtained, wherein the charge signal output by the PZT ceramic body is caused by the deformation of the shunt due to heat generated during sampling; The compensated charging current is calculated based on the charge signal and the charging current. The shunt compensation is added to the charging current to obtain the compensated charging current; The formula for calculating the shunt compensation is: in, This is the compensation amount for the shunt. The charging current is measured by the shunt. The coefficient of linear expansion is 1 / 3. This refers to the charge signal output by the PZT ceramic body. The temperature difference-charge signal conversion coefficient; The charge / discharge amount is calculated based on the compensated charging current and the voltage divider value of the charging voltage.

2. The method for measuring the charging and discharging capacity of an electric vehicle as described in claim 1, characterized in that, When the shunt is a manganese-copper shunt, and the PZT ceramic body is a PZT5H ceramic sheet, and is attached to the central area of ​​the upper surface of the resistive element of the manganese-copper shunt, the temperature difference-charge signal conversion coefficient is: .

3. The method for measuring the charging and discharging capacity of an electric vehicle as described in claim 1, characterized in that, By analyzing the CC / CP signal level, pulse width, and signal frequency characteristics during the charging handshake process, the charging and discharging status is identified, and the charging and discharging quantity is determined to be either the charging quantity or the discharging quantity based on the charging and discharging status.

4. A metering device for the charging and discharging of an electric vehicle, characterized in that, Installed inside the electric vehicle, it includes: a power metering and monitoring module, a data processing and storage module, an encryption and decryption module, and a wireless transmission module; The power metering and monitoring module is used to identify the charging and discharging status and measure the charging and discharging amount; wherein, the power metering and monitoring module is equipped with a shunt connected to a PZT ceramic body; when the shunt deforms due to heat generated by sampling, it causes the PZT ceramic body to output a charge signal, and the charge signal is used to compensate the current sampled by the shunt to calculate the compensated charging current. The shunt compensation is added to the charging current to obtain the compensated charging current; The formula for calculating the shunt compensation is: in, This is the compensation amount for the shunt. The charging current is measured by the shunt. The coefficient of linear expansion is 1 / 3. This refers to the charge signal output by the PZT ceramic body. The temperature difference-charge signal conversion coefficient; The data processing and storage module is used to statistically analyze and record the charging and discharging power. The encryption / decryption module is used to encrypt the charging / discharging power data. The wireless transmission module is used to transmit data about the charging and discharging power levels.

5. The metering device for the charging and discharging of an electric vehicle as described in claim 4, characterized in that, The power metering and monitoring module can be configured as an AC metering module and an AC charging protocol monitoring module, or as a DC metering module and a DC charging protocol monitoring module, or as an AC metering module, an AC charging protocol monitoring module, a DC metering module and a DC charging protocol monitoring module. The AC metering module is used to measure the amount of charge and discharge during AC charging and discharging. The AC charging protocol monitoring module is used to identify the charging and discharging status of AC charging and discharging. The DC metering module is used to measure the amount of charge and discharge during DC charging and discharging. The DC charging protocol monitoring module is used to identify the charging and discharging status of DC charging and discharging.

6. The metering device for the charging and discharging of an electric vehicle as described in claim 4, characterized in that, The shunt is a manganese copper shunt; the PZT ceramic body is a PZT5H ceramic sheet, which is attached to the central area of ​​the upper surface of the resistive element of the manganese copper shunt.

7. The metering device for the charging and discharging of an electric vehicle as described in claim 4, characterized in that, It also includes a thermal status acquisition and cooling module, which is connected to the power metering and monitoring module. The ambient temperature acquisition unit of the thermal state acquisition and cooling module is arranged near the splitter and away from the direct blowing area of ​​the micro fan, and is used to obtain the ambient boundary temperature of the splitter. The micro fan of the thermal state acquisition and cooling module blows airflow along the length of the splitter over the surface of the resistor.

8. The metering device for the charging and discharging of an electric vehicle as described in claim 7, characterized in that, The power metering and monitoring module calculates the shunt thermal state index based on the charge signal output by the PZT ceramic body, the ambient temperature collected by the thermal state acquisition and cooling module, and the charging current collected by the shunt. Then calculate the resistance compensation coefficient to compensate for the nominal resistance of the shunt; Then, the compensated current is calculated, and combined with the charging voltage division value collected by the shunt, the charging capacity is calculated.

9. A metering device for the charging and discharging of an electric vehicle as described in claim 8, characterized in that, The power metering and monitoring module determines the driving quantity of the micro fan based on the thermal state index of the shunt and transmits it to the thermal state acquisition and cooling module to realize the control of the micro fan.

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