A direct current charging closed-loop control method for electric vehicles

Abstract

The application relates to the technical field of direct-current charging of electric vehicles, and discloses a direct-current charging closed-loop control method for electric vehicles, which comprises the following steps: collecting battery pack state parameters and SOC estimation data, and generating battery pack state data; performing maximum charging capacity analysis and processing on the battery pack state data to generate target charging current data; when direct-current charging control of the electric vehicle is performed, real-time collection of actual current data entering the battery pack is performed, the target charging current is compared to generate a compensation amount, and the compensation amount is superimposed into a charging pile request current, so that current transmission loss in the charging loop can be compensated in real time, the accuracy of current control in the direct-current charging process is ensured, the charging efficiency is improved, and the charging time is shortened.

Description

Technical Field

[0001] This invention relates to the field of DC charging technology for electric vehicles, specifically a closed-loop control method for DC charging of electric vehicles. Background Technology

[0002] Electric vehicles are a new type of environmentally friendly transportation that relies on electricity to achieve zero or extremely low emissions, reducing environmental pollution. Batteries are the power source of electric vehicles, while charging devices are the power transmission channels for batteries and are an indispensable part of electric vehicles. DC charging refers to the conversion of high-voltage AC power from the power grid into high-voltage DC power required by electric vehicles by off-board conductive chargers.

[0003] Currently, due to various dynamic interference factors in the DC charging process of electric vehicles, when performing high-power DC charging, the battery management system calculates the target charging current through a preset charging rate table, but cannot compensate for the current transmission loss in the charging circuit in real time. When the actual current entering the battery pack deviates from the target current, it will cause a decrease in battery charging efficiency and a lengthening of charging time, making it impossible to guarantee accurate control of DC charging.

[0004] Therefore, a closed-loop control method for DC charging of electric vehicles is proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a closed-loop control method for DC charging of electric vehicles. The method provided by this invention solves the problems mentioned in the background art, such as reduced battery charging efficiency and extended charging time, which prevent accurate control of DC charging.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a closed-loop control method for DC charging of electric vehicles, the method comprising the following steps: Collect battery pack status parameters and SOC estimation data, and generate battery pack status data; Based on the battery pack status data, the maximum charging capacity of the cells is analyzed and processed to generate target charging current data. The actual charging current data during the DC charging process is collected, and the current difference is calculated based on the target charging current data and the actual charging current data to generate charging current compensation data. Based on the vehicle load demand data, the target charging current data, and the charging current compensation data, the requested current is calculated and processed to generate the pile end requested current data. The requested current data at the charging pile is sent to the charging pile to control the output current of the charging pile. Collect dynamic voltage data of the battery cells during DC charging, and perform SOC deviation judgment processing based on the preset battery cell charging rate table to generate SOC deviation type data. When the SOC deviation type data is a negative deviation, SOC upward interpolation correction processing is performed based on the cell dynamic voltage data to generate corrected SOC data; When the SOC deviation type data is a positive deviation, the SOC value is waited for until the cell voltage reaches the voltage limit. The target charging current data is updated based on the corrected SOC data and the SOC data awaiting processing. Throughout the entire charging process, the current difference calculation, request current calculation, and charging pile output control processes are continuously and cyclically executed to achieve closed-loop control of DC charging.

[0007] Preferably, generating battery pack status data includes the following steps: Temperature data of the battery pack is collected through the battery management system; The battery pack's SOC estimation data is collected through the battery management system; The temperature data and the SOC estimation data are combined to generate battery pack status data.

[0008] Preferably, generating the target charging current data includes the following steps: Obtain the temperature data and SOC estimation data from the battery pack status data; Based on the preset cell charging rate table, the corresponding maximum charging capacity value is queried according to the temperature data and the SOC estimation data; The maximum charging capacity value is converted into target charging current data.

[0009] Preferably, generating the charging current compensation data includes the following steps: The actual current entering the battery pack during DC charging is collected using a current sensor; Obtain the target charging current data; Calculate the difference between the target charging current data and the actual charging current data to generate charging current compensation data. The formula for calculating the difference is: ; in This indicates the charging current compensation data. This represents the target charging current data. This represents the actual incoming current data.

[0010] Preferably, generating the pile end requested current data includes the following steps: Obtain vehicle load requirements data; Obtain the target charging current data; Obtain the charging current compensation data; Based on the formula: Pile terminal requested current = Vehicle load demand + Target charging current + Charging current compensation, the pile terminal requested current data is calculated and generated.

[0011] Preferably, generating SOC deviation type data includes the following steps: The dynamic voltage value of the battery cell during DC charging is collected by a voltage sensor; Obtain current cell temperature data, charging current data, and SOC estimation data; Based on the cell charging rate table, query the corresponding voltage limit under the current conditions; Compare the dynamic voltage value with the voltage limit: When the dynamic voltage value is higher than the voltage limit, SOC deviation type data with negative deviation is generated; When the dynamic voltage value is lower than the voltage limit, SOC deviation type data with positive deviation is generated; The voltage comparison logic is as follows: when Then, negative deviation type SOC deviation type data is generated; when Then, positive deviation type SOC deviation type data is generated; in This indicates the dynamic voltage data of the battery cell. This indicates the voltage limit value obtained from the cell charging rate table.

[0012] Preferably, the SOC up-interpolation correction process includes the following steps: When the SOC deviation type data is a negative deviation, obtain the current cell dynamic voltage data; Based on the cell charging rate table, interpolation calculations are performed within adjacent SOC intervals; The corrected SOC data is generated based on the interpolation results.

[0013] Preferably, the SOC value waiting process includes the following steps: When the SOC deviation type data is a positive deviation, pause the increase of the SOC estimate; Continuously monitor changes in cell voltage; When the cell voltage reaches the voltage limit, the SOC estimate resumes normal growth.

[0014] Preferably, updating the target charging current data includes the following steps: Obtain the corrected SOC data and the SOC data awaiting processing; Based on the obtained corrected SOC data and the SOC data awaiting processing, as well as the battery pack temperature data collected by the battery management system, the cell charging rate table is queried again. Generate updated target charging current data.

[0015] Preferably, the continuous cyclic execution of current difference calculation processing, request current calculation processing, and charging pile output control process further includes a charging over-temperature protection step: Real-time monitoring of battery pack temperature data, and generation of battery pack temperature monitoring data; When the battery pack temperature monitoring data exceeds a preset temperature threshold, a charging derating instruction is generated. Based on the charging derating instruction data, the requested current data at the pile end is reduced by a preset ratio. When the battery pack temperature monitoring data falls back to the safety threshold, the original pile-end requested current data is restored. Continue executing the closed-loop control process using the updated pile-end request current data.

[0016] Beneficial effects Compared with the prior art, the present invention provides a closed-loop control method for DC charging of electric vehicles, which has the following beneficial effects: 1. In this invention, when controlling DC charging of electric vehicles, the actual current data entering the battery pack is collected in real time and compared with the target charging current to generate a compensation amount. The compensation amount is then added to the current requested by the charging pile. This can compensate for the current transmission loss in the charging circuit in real time, ensure the accuracy of current control during DC charging, improve charging efficiency, and shorten charging time.

[0017] 2. In this invention, when controlling DC charging of electric vehicles, the dynamic voltage data of the battery cells is monitored in real time, and the type of SOC estimation deviation is determined based on the preset voltage limit. When a deviation occurs, the corrected SOC data is generated by interpolation calculation, so that the system can automatically correct the SOC estimation error caused by the voltage plateau region characteristics of lithium iron phosphate batteries, avoid overcharging and undercharging of the battery, and ensure charging safety and reliability.

[0018] 3. In this invention, when controlling DC charging of electric vehicles, the battery pack temperature data is monitored in real time, and a dynamic derating command is generated when the temperature exceeds the safety threshold. The charging current is reduced proportionally according to the temperature risk level, enabling the system to achieve intelligent derating control in high-temperature scenarios, avoiding interruption due to overheating protection during charging, and improving the continuity of DC charging and user experience. Attached Figure Description

[0019] Figure 1 This is a flowchart of a DC charging closed-loop control method for electric vehicles according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] For specific implementation examples, please refer to: Figure 1 The present method for closed-loop control of DC charging for electric vehicles includes the following steps: Collect battery pack status parameters and SOC estimation data, and generate battery pack status data; Based on the battery pack status data, the maximum charging capacity of the cells is analyzed and processed to generate target charging current data. The system collects actual charging current data during DC charging and calculates the current difference based on the target charging current data and the actual charging current data to generate charging current compensation data. Based on the vehicle load demand data, target charging current data, and charging current compensation data, the requested current is calculated and processed to generate the pile-end requested current data. Send the requested current data from the charging pile to the charging pile and control the output current of the charging pile. Collect dynamic voltage data of the battery cells during DC charging, and perform SOC deviation judgment processing based on the preset battery cell charging rate table to generate SOC deviation type data. When the SOC deviation type data is negative deviation, SOC upward interpolation correction is performed based on the cell dynamic voltage data to generate corrected SOC data. When the SOC deviation type data is a positive deviation, the SOC value is pending processing until the cell voltage reaches the voltage limit. Update the target charging current data based on the corrected SOC data and the SOC data awaiting processing; Throughout the entire charging process, the current difference calculation, request current calculation, and charging pile output control processes are continuously and cyclically executed to achieve closed-loop control of DC charging.

[0022] Generating battery pack status data includes the following steps: Temperature data of the battery pack is collected through the battery management system; The battery pack's SOC estimation data is collected through the battery management system; Temperature data and SOC estimation data are combined to generate battery pack status data.

[0023] Generating the target charging current data includes the following steps: Obtain temperature data and SOC estimation data from the battery pack status data; Based on the preset cell charging rate table, the corresponding maximum charging capacity value is queried according to temperature data and SOC estimation data; Convert the maximum charging capacity value into target charging current data.

[0024] Generating charging current compensation data includes the following steps: The actual current entering the battery pack during DC charging is collected using a current sensor, specifically including the following operations: Real-time current signal is captured using a Hall sensor; Kalman filtering is applied to the current signal for noise reduction. ; in This is the filtered actual incoming current data. The original current value of the sensor. The Kalman gain coefficient is... This is the filter current value from the previous moment; Obtain the target charging current data; Calculate the difference between the target charging current data and the actual charging current data to generate charging current compensation data. The formula for calculating the difference is: ; in This indicates the charging current compensation data. This represents the target charging current data. This represents the actual incoming current data.

[0025] Generating the requested current data at the pile end includes the following steps: Obtain vehicle load requirements data; Obtain the target charging current data; Obtain charging current compensation data; Based on the formula: Pile terminal requested current = Vehicle load demand + Target charging current + Charging current compensation, the pile terminal requested current data is calculated and generated.

[0026] Generating SOC deviation type data includes the following steps: The dynamic voltage value of the battery cell during DC charging is collected by a voltage sensor; Obtain current cell temperature data, charging current data, and SOC estimation data; Based on the cell charging rate table, the corresponding voltage limit under the current conditions is retrieved. The cell charging rate table is generated through the following steps: Controlling the cell temperature gradient in a constant temperature environment ranging from -20℃ to 55℃; Charging tests were conducted at various temperature points with a current range of 2.7A–86A. Record dynamic voltage data corresponding to different SOC values ​​from 10% to 100%; The voltage-temperature-current surface was fitted using cubic spline interpolation. ; in Indicates voltage limit. Indicates the temperature variation of the battery cell. The charging current variable is represented by SOC, and the state of charge variable is represented by SOC. The fitting coefficient for the temperature term is represented. The fitting coefficients for the current term are represented. express The fitting coefficient of the term, , , Indicates the order of the polynomial, representing temperature, current, and... The highest power of the three variables in the fitted model; Compare the dynamic voltage value with the voltage limit: When the dynamic voltage value is higher than the voltage limit, SOC deviation type data with negative deviation is generated; When the dynamic voltage value is lower than the voltage limit, SOC deviation type data with positive deviation is generated; The voltage comparison logic is as follows: when Then, negative deviation type SOC deviation type data is generated; when Then, positive deviation type SOC deviation type data is generated; in This indicates the dynamic voltage data of the battery cell. This indicates the voltage limit value obtained from the cell charging rate table.

[0027] The SOC up-interpolation correction process includes the following steps: When the SOC deviation type data is negative deviation, obtain the current cell dynamic voltage data; Based on the cell charging rate table, interpolation calculations are performed within adjacent SOC intervals, specifically including the following steps: Determine the boundary values ​​of the cell dynamic voltage data within adjacent SOC intervals: Obtain the low boundary SOC value and their corresponding voltage limits ; Obtain the high boundary SOC value and their corresponding voltage limits ; Calculate the voltage normalization scaling factor: ; in This represents the ratio of voltage to relative position. This is the dynamic voltage data of the battery cell. For low boundary SOC voltage limits, For high boundary SOC voltage limits; Generate corrected SOC data based on the interpolation results: ; in Indicates after correction data, This is the voltage normalization scaling factor. Indicates the lower boundary of the interval value, Indicates the high boundary of the interval value.

[0028] The SOC value waiting process includes the following steps: When the SOC deviation type data is a positive deviation, pause the increase of the SOC estimate; Continuously monitor changes in cell voltage; When the cell voltage reaches the voltage limit, the SOC estimate resumes normal growth, specifically including the following steps: When the cell voltage reaches the voltage limit, the ampere-hour integration method is used to dynamically calibrate the SOC estimate. Calculate the SOC growth using the ampere-hour integral formula: SOC ; in SOC represents the increase in the estimated SOC value. Indicates the battery's rated capacity. This represents the actual incoming current value as a function of time. This indicates the starting point of SOC's recovery and growth. Indicates the current time; The SOC estimate is updated based on the growth rate.

[0029] Updating the target charging current data includes the following steps: Obtain the corrected SOC data and the SOC data awaiting processing; Based on the obtained corrected SOC data and the SOC data awaiting processing, as well as the battery pack temperature data collected by the battery management system, the cell charging rate table is queried again. Generate updated target charging current data.

[0030] The continuous loop execution of current difference calculation, request current calculation, and charging pile output control processes also includes a charging over-temperature protection step. Real-time monitoring of battery pack temperature data, and generation of battery pack temperature monitoring data; When the battery pack temperature monitoring data exceeds the preset temperature threshold, a charging derating instruction is generated, which includes the following steps: Obtain temperature safety reference parameters: preset temperature threshold Battery pack safe temperature threshold ; Calculate the temperature risk gradient coefficient: ; This represents the temperature risk level coefficient. This indicates battery pack temperature monitoring data. Indicates the safe temperature threshold. Indicates the preset temperature threshold; Generate current derating instruction: ; in Request current data for the pile end after the rate reduction. Request current data for the original pile tip; Based on the charging derating instruction data, the requested current data at the pile end is reduced by a preset ratio. When the battery pack temperature monitoring data falls back to the safety threshold, restore the original pile-end requested current data; Continue executing the closed-loop control process using the updated pile-end request current data.

[0031] The operation steps of this closed-loop control method for DC charging of electric vehicles are as follows: Step 1: Real-time compensation for current transmission loss The battery management system collects real-time current data of the current entering the battery pack and dynamically compares it with the target charging current to generate a current difference compensation amount. This compensation amount is added to the current requested by the charging pile, forming a closed-loop current compensation mechanism. This process is continuously executed in a loop to ensure that current losses in the charging circuit are offset in real time, thereby improving charging efficiency and shortening charging time.

[0032] Step 2: Dynamic Correction of SOC Estimation Deviation Based on the cell charging rate table, the voltage limit under the current operating conditions is retrieved. By comparing the real-time dynamic voltage with the voltage limit, the type of SOC estimation deviation is determined. When a negative deviation is detected, linear interpolation calculation is performed within the adjacent SOC interval to generate corrected SOC data. This mechanism accurately corrects the SOC error caused by the voltage plateau region characteristics of lithium iron phosphate batteries, avoiding the risks of overcharging and undercharging.

[0033] Step 3: Intelligent Depreciation Control for Temperature Risk The system monitors battery pack temperature data in real time. When the temperature exceeds a safety threshold, it calculates a temperature risk level coefficient. Based on this coefficient, it proportionally reduces the charging pile's output current, generating a dynamic derating command. Once the temperature drops back to the safety threshold, the original charging current is automatically restored. This closed-loop control strategy maintains charging continuity in high-temperature scenarios, avoiding charging interruptions caused by overheat protection.

[0034] Step 4: Multi-parameter collaborative closed-loop execution Current compensation data, corrected SOC data, and temperature derating commands are dynamically integrated to construct a summary parameter for charging control. The charging pile adjusts its output in real time based on the summary parameter, while simultaneously cyclically executing the current acquisition, SOC calibration, and temperature monitoring process, forming a complete closed-loop control chain of "monitoring-decision-execution-feedback" to ensure the efficiency and safety of the DC charging process.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A closed-loop control method for DC charging of electric vehicles, characterized in that: The method includes the following steps: Collect battery pack status parameters and SOC estimation data, and generate battery pack status data; Based on the battery pack status data, the maximum charging capacity of the cells is analyzed and processed to generate target charging current data. The actual charging current data during the DC charging process is collected, and the current difference is calculated based on the target charging current data and the actual charging current data to generate charging current compensation data. Based on the vehicle load demand data, the target charging current data, and the charging current compensation data, the requested current is calculated and processed to generate the pile end requested current data. The requested current data at the charging pile is sent to the charging pile to control the output current of the charging pile. Collect dynamic voltage data of the battery cells during DC charging, and perform SOC deviation judgment processing based on a preset battery cell charging rate table to generate SOC deviation type data, including the following steps: The dynamic voltage value of the battery cell during DC charging is collected by a voltage sensor; Obtain current cell temperature data, charging current data, and SOC estimation data; Based on the cell charging rate table, query the corresponding voltage limit under the current conditions; Compare the dynamic voltage value with the voltage limit: When the dynamic voltage value is higher than the voltage limit, SOC deviation type data with negative deviation is generated; When the dynamic voltage value is lower than the voltage limit, SOC deviation type data with positive deviation is generated; The voltage comparison logic is as follows: when Then, negative deviation type SOC deviation type data is generated; when Then, positive deviation type SOC deviation type data is generated; in This indicates the dynamic voltage data of the battery cell. This indicates the voltage limit value retrieved from the cell charging rate table; When the SOC deviation type data is a negative deviation, SOC upward interpolation correction processing is performed based on the cell dynamic voltage data to generate corrected SOC data; When the SOC deviation type data is a positive deviation, the SOC value is waited for until the cell voltage reaches the voltage limit. The target charging current data is updated based on the corrected SOC data and the SOC data awaiting processing. Throughout the entire charging process, the current difference calculation, request current calculation, and charging pile output control processes are continuously and cyclically executed to achieve closed-loop control of DC charging.

2. The closed-loop control method for DC charging of an electric vehicle according to claim 1, characterized in that: The process of generating battery pack status data includes the following steps: Temperature data of the battery pack is collected through the battery management system; The battery pack's SOC estimation data is collected through the battery management system; The temperature data and the SOC estimation data are combined to generate battery pack status data.

3. The closed-loop control method for DC charging of an electric vehicle according to claim 2, characterized in that: The process of generating the target charging current data includes the following steps: Obtain the temperature data and SOC estimation data from the battery pack status data; Based on the preset cell charging rate table, the corresponding maximum charging capacity value is queried according to the temperature data and the SOC estimation data; The maximum charging capacity value is converted into target charging current data.

4. The closed-loop control method for DC charging of an electric vehicle according to claim 1, characterized in that: The process of generating charging current compensation data includes the following steps: The actual current entering the battery pack during DC charging is collected using a current sensor; Obtain the target charging current data; Calculate the difference between the target charging current data and the actual charging current data to generate charging current compensation data. The formula for calculating the difference is: ； in This indicates the charging current compensation data. This represents the target charging current data. This represents the actual incoming current data.

5. The closed-loop control method for DC charging of an electric vehicle according to claim 1, characterized in that: The process of generating the requested current data at the pile end includes the following steps: Obtain vehicle load requirements data; Obtain the target charging current data; Obtain the charging current compensation data; Based on the formula: Pile terminal requested current = Vehicle load demand + Target charging current + Charging current compensation, the pile terminal requested current data is calculated and generated.

6. The closed-loop control method for DC charging of an electric vehicle according to claim 1, characterized in that: The SOC up-interpolation correction process includes the following steps: When the SOC deviation type data is a negative deviation, obtain the current cell dynamic voltage data; Based on the cell charging rate table, interpolation calculations are performed within adjacent SOC intervals; The corrected SOC data is generated based on the interpolation results.

7. The closed-loop control method for DC charging of an electric vehicle according to claim 1, characterized in that: The process of waiting for the SOC value includes the following steps: When the SOC deviation type data is a positive deviation, pause the increase of the SOC estimate; Continuously monitor changes in cell voltage; When the cell voltage reaches the voltage limit, the SOC estimate resumes normal growth.

8. The closed-loop control method for DC charging of an electric vehicle according to claim 1, characterized in that: Updating the target charging current data includes the following steps: Obtain the corrected SOC data and the SOC data awaiting processing; Based on the obtained corrected SOC data and the SOC data awaiting processing, as well as the battery pack temperature data collected by the battery management system, the cell charging rate table is queried again. Generate updated target charging current data.

9. The closed-loop control method for DC charging of an electric vehicle according to claim 1, characterized in that: The continuous cyclic execution of current difference calculation, request current calculation, and charging pile output control process also includes a charging over-temperature protection step: Real-time monitoring of battery pack temperature data, and generation of battery pack temperature monitoring data; When the battery pack temperature monitoring data exceeds a preset temperature threshold, a charging derating instruction is generated. Based on the charging derating instruction data, the requested current data at the pile end is reduced by a preset ratio. When the battery pack temperature monitoring data falls back to the safety threshold, the original pile-end requested current data is restored. Continue executing the closed-loop control process using the updated pile-end request current data.

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