A method for controlling charging voltage of new energy vehicle

Abstract

The present invention discloses a method for controlling the charging voltage of a new energy vehicle, which specifically relates to the field of new energy technology, and comprises the following steps: obtaining each state parameter of a battery of a new energy vehicle before charging starts and performing a safety state judgment, and determining whether the battery of the new energy vehicle is in a normal state based on the safety state judgment result; when the battery of the new energy vehicle is in a normal state before charging starts, performing a charging analysis operation to obtain a voltage input index and a power input index respectively; performing fuzzy reasoning according to the voltage input index and the power input index to determine the type of charging to be started and to perform charging; performing safety monitoring during the charging process, triggering a preset safety mechanism when a target state parameter has a safety hazard, and performing safety adjustments according to a preset safety strategy until the safety hazard is eliminated; the present invention can dynamically select the charging mode that best suits the current battery state, and maximize the charging efficiency while ensuring the battery safety.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and more specifically, to a method for controlling a charging voltage of a new energy vehicle. Background Art

[0002] New energy vehicles refer to vehicles that use unconventional vehicle fuels or conventional vehicle fuels but are combined with new on-board power devices. New energy vehicles include pure electric vehicles, extended-range electric vehicles, hybrid vehicles, fuel cell electric vehicles, hydrogen engine vehicles and other types. New energy vehicles are not only significantly different from traditional fuel vehicles in terms of technical principles, but also excel in environmental protection and energy conservation. For example, pure electric vehicles mainly rely on rechargeable batteries for power, and use motors to drive the wheels, which can achieve zero emissions, low noise, and relatively low cost of use. Hybrid vehicles, on the other hand, combine internal combustion engines and electric motors to recover braking energy while the engine is working, improve fuel economy, and reduce tail gas emissions.

[0003] When charging traditional new energy vehicles, most of them rely on fixed thresholds to switch charging modes, lacking intelligent judgment based on battery status. Such control methods may not be able to adjust the charging mode in time when the battery status changes complexly, resulting in low charging efficiency and even safety issues. Therefore, a method for controlling the charging voltage of new energy vehicles is proposed. Summary of the invention

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for controlling the charging voltage of a new energy vehicle comprises the following steps:

[0006] Obtain each state parameter of the new energy vehicle battery before charging begins and make a safety status judgment, and determine whether the new energy vehicle battery is in a normal state based on the safety status judgment result;

[0007] When the battery of the new energy vehicle is in a normal state before charging begins, a charging analysis operation is performed to obtain a voltage input index and a power input index respectively;

[0008] Fuzzy reasoning is performed based on the voltage input index and the power input index to determine the type of charging to be started and to execute charging;

[0009] Safety monitoring is carried out during the charging process. When there are safety hazards in the target state parameters, the preset safety mechanism is triggered and safety adjustments are made according to the preset safety strategy until the safety hazards are eliminated.

[0010] In a preferred embodiment, safety status determination refers to:

[0011] Get each state parameter separately and compare it with the corresponding normal state value range. If the target item state parameter falls within the corresponding normal state value range, the target item state parameter is in a normal state. If the target item state parameter does not fall within the corresponding normal state value range, the target item state parameter is in an abnormal state. If all state parameters are in a normal state, the new energy vehicle battery is in a normal state.

[0012] In a preferred embodiment, the logic for obtaining the voltage input index is:

[0013] Get the current battery voltage and mark it as , the minimum operating voltage of the battery and is marked as , the maximum operating voltage of the battery is marked as , the current battery temperature and marked as , standard reference temperature and is marked as , the characteristic coefficients corresponding to the battery materials are marked as , the internal integrated impedance of the battery is marked as , the current battery current and is marked as , and then substitute them into the voltage input index calculation formula:

[0014] ;

[0015] is the voltage input index, is the preset temperature compensation coefficient.

[0016] In a preferred embodiment, the internal integrated impedance of the battery The acquisition logic is:

[0017] Under a stable current input, the stable current is marked as , and then set n time periods t, the heat generated in each period is , then calculate the stable current The product of the square of the time period t, and then the heat generated in each cycle Divide by the product value to obtain n proportional values, and take the average value of all proportional values ​​to obtain an impedance value of one;

[0018] Obtain the absolute value of the difference between the voltage data at the end of each time period t and the voltage data at the beginning under the stable current input, then calculate the average value of all absolute values ​​and divide the average value by the stable current , get impedance value 2;

[0019] The internal comprehensive impedance of the battery is obtained by weighted summing the impedance value 1 and the impedance value 2. .

[0020] In a preferred embodiment, the logic for obtaining the power input index is:

[0021] Get the current remaining battery power and mark it as , the total capacity of the battery and is marked as , the self-discharge rate of the battery and is marked as , the battery aging factor is marked as , the number of charge and discharge cycles of the battery is marked as , and then substitute them into the calculation formula of power input index: ; Enter an index for the charge.

[0022] In a preferred embodiment, the battery aging factor The calculation formula is: ; Greater than zero.

[0023] In a preferred embodiment, the logic of fuzzy reasoning is:

[0024] The voltage input index and the power input index are obtained separately and used as input variables together, the type of new energy vehicle charging is used as the output variable, the input variables are fuzzified, and the values ​​of the input variables are converted into fuzzy sets. The output variables are fuzzified and converted into fuzzy sets. Fuzzy rules are formulated to describe the charging type requirements under different data type combinations. The fuzzified input variables are inferred through fuzzy rules to determine the type of new energy vehicle charging.

[0025] In a preferred embodiment, the types of start-up charging include constant current charging type, constant voltage charging type and trickle charging type.

[0026] In a preferred embodiment, the target state parameter has a potential safety hazard, which means:

[0027] Get the time series data of the target state parameters, and then calculate the standard deviation of the time series data and the rate of change between two adjacent data acquisition moments: ; is a preset positive constant, Get the rate of change between time i and i+1 for two adjacent data, represents the data value of the target state parameter corresponding to time i, The data value of the target state parameter corresponding to time i+1 is represented by comparing the standard deviation of the time series data with the preset standard threshold value and the rate of change The absolute value of the time series data is compared with the preset standard change reference value. If the standard deviation of the time series data is less than or equal to the preset standard threshold and the change rate If the absolute value of the time series data is less than or equal to the preset standard change reference value, then there is no safety hazard in the target state parameter. If the standard deviation of the time series data is less than or equal to the preset standard threshold and the change rate is not satisfied, If the absolute value of is less than or equal to the preset standard change reference value, there is a safety hazard in the target state parameter.

[0028] Technical effects and advantages of the present invention:

[0029] By comprehensively monitoring the voltage, power, temperature and other state parameters of the battery, the present invention can detect potential safety hazards in real time during the charging process, such as overcharging, over-discharging, overheating, etc. By intelligently adjusting the charging voltage and charging mode, it can effectively prevent damage and safety accidents caused by abnormal battery conditions.

[0030] The present invention introduces the voltage input index and the power input index, and combines fuzzy reasoning to select the charging mode that best suits the current battery state (such as constant current charging, constant voltage charging, and trickle charging). This dynamic adjustment of the charging mode can maximize charging efficiency and shorten charging time while ensuring battery safety.

[0031] By real-time monitoring of the battery's internal comprehensive impedance, self-discharge rate and aging coefficient, the present invention can more accurately determine the battery's health status and adjust the charging strategy accordingly to avoid long-term charging of the battery under unfavorable conditions, thereby reducing the risk of excessive aging and extending the battery's service life.

[0032] When abnormal battery parameters are detected, the preset safety mechanism can be triggered in time, and the charging voltage can be adjusted or charging can be suspended according to the safety strategy until the safety hazard is eliminated. This fast response mechanism ensures that during the charging process, the present invention can dynamically adjust the battery status to avoid potential dangers. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to facilitate understanding by those skilled in the art, the present invention is further described below in conjunction with the accompanying drawings;

[0034] Figure 1 This is a schematic diagram of a method for controlling the charging voltage of a new energy vehicle in the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Reference Figure 1 The following embodiments are obtained:

[0037] Embodiment 1: A method for controlling the charging voltage of a new energy vehicle comprises the following steps:

[0038] Obtain each state parameter of the new energy vehicle battery before charging begins and make a safety state judgment. Based on the safety state judgment result, know whether the new energy vehicle battery is in a normal state; before charging begins, detect the battery state parameters (such as voltage, current, temperature, etc.) to ensure that they are within the safe range to prevent dangerous situations such as battery overheating, overcooling, and overvoltage. If the battery parameters are abnormal when charging begins, it may cause failure or danger, so it is very important to check the state before charging begins. Determine whether the battery is suitable for charging by the state parameters to avoid potential dangers during the charging process. After obtaining the various state parameters of the battery, analyze these parameters to determine whether the battery is within the normal working range. This step is to ensure that the charging operation is started only when the battery is in good condition. Otherwise, the protection mechanism or adjustment strategy may be triggered to avoid damaging the battery or causing safety hazards. Ensure that the charging process is started only when the battery is in normal condition to protect the battery safety.

[0039] When the battery of a new energy vehicle is in a normal state before charging begins, a charging analysis operation is performed to obtain the voltage input index and the power input index respectively; this step quantifies the current state of the battery by calculating the voltage input index and the power input index of the battery. The calculation of these two indexes can help to more accurately select a suitable charging strategy. By quantifying the voltage and power input index, it is helpful to flexibly select a suitable charging mode according to the battery status.

[0040] Fuzzy reasoning is performed based on the voltage input index and the power input index to determine the type of charging to start and perform charging. Through the fuzzy reasoning method, the voltage input index and the power input index are used as input variables, and reasoning is performed based on the preset fuzzy rules to determine the most suitable charging type (such as constant current charging, constant voltage charging or trickle charging). Fuzzy reasoning can flexibly select the most suitable charging mode when the battery state is more complex or uncertain, so as to balance the charging efficiency and battery safety. Optimize the charging process and flexibly select the most suitable charging strategy when the battery state changes, thereby improving charging efficiency and safety.

[0041] Safety monitoring is performed during the charging process. When there are safety hazards in the target state parameters, the preset safety mechanism is triggered and safety adjustments are made according to the preset safety strategy until the safety hazards are eliminated. During the charging process, the battery state may change due to changes in current, voltage, temperature, etc., so these parameters need to be monitored in real time to ensure the safety of the charging process. If any abnormal situation is detected, adjustments can be made in time. Ensure that the battery is always in a safe state during the entire charging process to prevent dangerous situations such as battery overheating and overvoltage. If a parameter (such as temperature or voltage) is detected to be abnormal during the charging process, the preset safety mechanism is automatically triggered, and the charging process is adjusted or paused according to the preset strategy. For example, if the temperature is too high, the charging power can be temporarily reduced or charging can be stopped until the temperature returns to a safe range. This mechanism helps protect the safety of the battery and the user. Ensure that the charging equipment can automatically adjust to protect the battery and the charging equipment when any safety hazards occur, and prevent any potential dangers.

[0042] Safety status judgment means: obtaining each status parameter separately and comparing it with the corresponding normal status value range. If the target status parameter falls within the corresponding normal status value range, the target status parameter is in a normal state. If the target status parameter does not fall within the corresponding normal status value range, the target status parameter is in an abnormal state. If all status parameters are in a normal state, the new energy vehicle battery is in a normal state. Obtaining each key status parameter of the battery ensures that the actual working condition of the battery can be fully understood, not just relying on a single parameter to avoid potential hidden dangers being ignored. Each status parameter has a reasonable working range (for example, the battery voltage is safe within a certain range). By comparing the current state with the preset normal value range, abnormal conditions can be identified in time and measures can be taken in advance. If a single status parameter exceeds the normal range, it can be judged that the parameter is in an abnormal state, indicating a potential safety risk. In this way, adjustments or alarms can be made for specific problems. Only when all parameters are in a normal state is the battery considered to be normal as a whole. This comprehensive judgment mechanism can ensure that the battery starts charging in the best state and avoid charging hazards caused by abnormalities in some parameters. The ultimate goal of this step is to ensure the safety of new energy vehicle batteries. By independently judging each status parameter, the safety status of the battery can be fully controlled to prevent safety hazards caused by abnormal parameters during charging. This multi-dimensional safety status judgment is a key step in ensuring the safety of new energy vehicle battery charging. It accurately compares each status parameter to ensure that any potential risks are avoided before charging.

[0043] The logic for obtaining the voltage input index is:

[0044] Get the current battery voltage and mark it as , that is, the actual voltage of the battery in the current charging or discharging state, the minimum operating voltage of the battery and marked as , refers to the lowest safe voltage at which the battery can operate normally. A voltage lower than this may cause the battery to be damaged or over-discharged. The maximum operating voltage of the battery is marked as , exceeding this voltage may cause overcharging, which may bring safety risks. The current battery temperature is marked as , reflects the temperature rise of the battery due to chemical reactions during the charging and discharging process, and is marked as the standard reference temperature , usually room temperature (e.g. 25°C), used to compensate for battery temperature, the characteristic coefficients corresponding to the battery material and marked as , used to describe the effect of battery material properties on voltage, the internal integrated impedance of the battery and is marked as , the current battery current and is marked as , which indicates the current size of the current during charging or discharging. The change of current will directly affect the change of the internal voltage of the battery, and then it is substituted into the voltage input index calculation formula:

[0045] ;

[0046] is the voltage input index, which indicates the current battery voltage within its acceptable operating range from the lowest operating voltage to the highest operating voltage, while taking into account the effects of temperature, internal resistance and current. Larger, closer to 1, indicating that the battery voltage is close to , the battery is close to full charge or there is a high risk of overcharge. Smaller, closer to 0, indicating that the battery voltage is close to , the battery power is low or there may be a risk of over-discharge. The larger the voltage input index, the closer the current battery voltage is to its maximum allowable voltage, which means the battery may be nearly fully charged. If the voltage input index is too large, it may indicate that the battery is close to being overcharged, and the charging current needs to be reduced or charging needs to be stopped to protect the battery safety.

[0047] The temperature compensation coefficient is a preset temperature compensation coefficient related to the battery temperature, which is used to adjust the difference between the battery temperature and the standard reference temperature. The size of the temperature compensation coefficient can be determined based on experimental data or the relationship between temperature and voltage changes provided by the battery manufacturer. For example, the temperature of different battery types (such as lithium batteries and lead-acid batteries) has different effects on voltage, and needs to be set according to the actual situation of the battery. When the temperature rises, the internal resistance of the battery may decrease, but high temperature may also accelerate the evaporation of the electrolyte or the aging of the battery. The temperature compensation coefficient is used to indicate the impact of temperature changes on battery performance.

[0048] The temperature compensation coefficient is usually pre-set based on the physical characteristics of the battery and experimental data. In order to ensure that the battery can work stably at different temperatures, the battery manufacturer or engineer will determine this compensation coefficient through experiments and simulations based on the impact of different temperatures on battery performance.

[0049] Reasons for presetting: Different battery materials have different characteristics: Different batteries (such as lithium-ion batteries, nickel-metal hydride batteries, etc.) have different sensitivities to temperature, so the compensation coefficient usually needs to be determined based on the material and structure of the specific battery. Through actual charging and discharging experiments, researchers can measure the voltage variation of the battery under different temperature conditions and set a reasonable compensation coefficient based on these data. Temperature affects the electrochemical reaction rate of the battery, so the pre-set temperature compensation coefficient helps to avoid overcharging or over-discharging of the battery under extreme temperature conditions and prolong the battery life.

[0050] Common temperature compensation coefficient range: The temperature compensation coefficient is usually a decimal that reflects the effect of temperature changes on the battery voltage. The common range is: 0.001 to 0.01 per degree Celsius, and the specific value depends on the type of battery and the application environment. For example: For lithium-ion batteries, the temperature compensation coefficient may be close to 0.003 / ℃. For nickel-metal hydride batteries, the temperature compensation coefficient may be close to 0.005 / ℃. The temperature compensation coefficient is usually a specific value obtained by a one-to-one mapping based on the difference between the current temperature of the battery and the reference temperature.

[0051] Each temperature difference A voltage correction value will be generated, which is determined by the temperature compensation coefficient. The temperature compensation coefficient is obtained based on experimental data or engineering calculations, reflecting the impact of every 1°C increase or decrease in battery voltage. For example, if the temperature compensation coefficient is 0.005V / °C, then the voltage will drop by 0.005V for every 1°C increase in battery temperature, so corresponding compensation is required.

[0052] By calculating the heat accumulation and voltage difference of multiple cycles under stable current, the changes in the internal impedance of the battery can be fully reflected, especially during the charging and discharging process. This impedance is a key factor affecting battery performance and life. The data accumulation and calculation of each time period can avoid the influence of single measurement errors and ensure that the impedance calculation is more accurate. Especially when the current and voltage fluctuations are small, the cumulative calculation of multiple cycles can effectively capture the slight changes in impedance. The internal comprehensive impedance of the battery is a key parameter for the battery management system (BMS) to monitor the health status of the battery. The battery management system (BMS) is an existing technology and will not be described in detail here. Through precise impedance measurement, the BMS can adjust the charging strategy in real time to prevent overcharging or over-discharging of the battery.

[0053] The greater the internal impedance of the battery, the greater the resistance to current during charging and discharging. This usually means that the health of the battery is deteriorating, the battery is aging, or the battery temperature is high and the internal loss is large. When the impedance increases, the battery will produce greater voltage losses during charging and discharging, resulting in a decrease in charging and discharging efficiency. Specifically, the battery provides less electrical energy during discharge, and more of the energy absorbed during charging is used to overcome the internal impedance and is wasted on heat generation. The increase in battery impedance will also lead to more heat accumulation, because the resistance is proportional to the square of the current, and the heat generated when the current passes through the battery increases. Long-term high-temperature operation may further aggravate battery aging and even cause safety problems.

[0054] Since the present invention is mainly aimed at charging voltage control, the internal comprehensive impedance of the battery in the present invention is The acquisition logic is: under stable current input, the stable current is marked as , and then set n time periods t, the heat generated in each period is , then calculate the stable current The product of the square of the time period t, and then the heat generated in each cycle Divide by the product value to obtain n proportional values, and take the average value of all proportional values ​​to obtain an impedance value of one;

[0055] Obtain the absolute value of the difference between the voltage data at the end of each time period t and the voltage data at the beginning under the stable current input, then calculate the average value of all absolute values ​​and divide the average value by the stable current , get impedance value 2;

[0056] The internal comprehensive impedance of the battery is obtained by weighted summing the impedance value 1 and the impedance value 2. .

[0057] ; is the impedance value one, is the impedance value 2, , is the corresponding weighting coefficient, which is adjusted according to the importance of impedance value 1 and impedance value 2, and usually satisfies that the sum of the two is one.

[0058] The logic for obtaining the power input index is:

[0059] Get the current remaining battery power and mark it as , the total capacity of the battery and is marked as , the self-discharge rate of the battery and is marked as , the battery aging factor is marked as , the number of charge and discharge cycles of the battery is marked as , and then substitute them into the calculation formula of power input index: ; Enter an index for the charge.

[0060] During long-term use of a battery, the remaining power cannot directly reflect the actual available power of the battery. The formula can more accurately evaluate the current available power of the battery by adding correction factors such as self-discharge rate and aging coefficient. Self-discharge is the phenomenon that the power of a battery decreases spontaneously when it is not in use. By introducing the self-discharge rate, this formula corrects the power loss of the battery when it is not in use for a long time, ensuring that the obtained power index is closer to the actual situation. The self-discharge rate of a battery refers to the fact that the battery will spontaneously lose a certain proportion of power when it is not in use. Generally, battery manufacturers will provide the typical self-discharge rate of the battery through experiments, and users can find relevant information in the battery specifications.

[0061] The larger the power input index is, the more power the battery currently has available, which means the better the battery condition is and the more energy it can provide. Conversely, the smaller the power input index is, the less power the battery has left and may need to be charged as soon as possible or the battery is seriously aged.

[0062] Battery aging factor The calculation formula is: ; Greater than zero. The aging factor of the battery is described by the number of charge and discharge cycles. As the number of uses increases, the performance of the battery will gradually decay. Therefore, this formula not only takes into account the current power, but also combines the battery's usage history to reflect the health of the battery. It is usually expressed as an acceleration factor or rate constant, which determines the rate of change of the model or the steepness of the curve. Determines how fast the battery ages. Indicates that the battery ages faster, and the smaller Indicates that the battery ages slowly. k is usually a positive number because the aging process is irreversible and the battery performance will only decrease as the number of cycles increases. The value is between 10 to the negative power of -3 and 10 to the negative power of -1.

[0063] The logic of fuzzy reasoning is:

[0064] The voltage input index and the power input index are obtained separately and used as input variables together, and the type of new energy vehicle charging is used as the output variable. The input variables are fuzzified and the values ​​of the input variables are converted into fuzzy sets. The output variables are fuzzified and the output variables are converted into fuzzy sets. Fuzzy rules are formulated to describe the charging type requirements under different data type combinations. The fuzzified input variables are inferred through fuzzy rules to determine the type of new energy vehicle charging. The types of charging include constant current charging type, constant voltage charging type and trickle charging type.

[0065] The voltage input index and the power input index are obtained separately and used as input variables in the reasoning process. The voltage input index reflects the current voltage state of the battery, and the power input index reflects the remaining power of the battery. The two indexes together determine the current charging demand of the battery. Fuzzification is performed on the input variables. Fuzzification refers to converting specific values ​​into fuzzy sets in order to process uncertain or ambiguous information. The voltage input index and the power input index will be converted into fuzzy sets respectively. For example, the voltage input index is divided into "low voltage", "medium voltage" and "high voltage", and the power input index is divided into "low power", "medium power" and "high power".

[0066] Fuzzy processing is also required for the output variable, i.e., the charging type of new energy vehicles. The charging types can include the following three types: Constant current charging type: When the battery power is low, a constant current is used for fast charging to increase the battery voltage. Constant voltage charging type: When the battery is nearly fully charged, the voltage remains constant and the current gradually decreases to protect the battery. Trickle charging type: When the battery is nearly fully charged, a very small current is used to maintain the battery power to avoid overcharging.

[0067] Fuzzy input variables: voltage input index and power input index.

[0068] Fuzzy output variable: charging type (constant current charging, constant voltage charging, trickle charging).

[0069] Fuzzy rules: The following logic should be made clear: When the voltage input index is "low voltage" and the power input index is "low power", choose constant current charging. When the voltage input index is "high voltage" and the power input index is "medium power", choose constant voltage charging. When the voltage input index is "high voltage" and the power input index is "high power", choose trickle charging.

[0070] The input variables of fuzzy reasoning are voltage input index and power input index, which are used to characterize the current battery status:

[0071] The output variable is the charging type, which indicates the charging mode that should be adopted under different conditions. There are three types: Constant current charging type: used when the battery voltage is low, the battery voltage is increased by maintaining a constant current. Constant voltage charging type: used when the battery voltage is close to full charge, the charging current is gradually reduced through a constant voltage to avoid overcharging the battery. Trickle charging type: when the battery is close to being fully charged, a very small current is used to maintain the charge to prevent overcharging.

[0072] In order to perform fuzzy reasoning, the input and output variables need to be fuzzified. Take three fuzzy sets as an example: Voltage input index: can be divided into "low voltage", "medium voltage", and "high voltage". Power input index: can be divided into "low power", "medium power", and "high power". Output charging type: divided into "constant current charging", "constant voltage charging", and "trickle charging". Each fuzzy set has a membership function, which is used to represent the membership of the input value or output value to the fuzzy set. The membership value ranges from 0 to 1, indicating the degree to which the current input belongs to a certain fuzzy set.

[0073] Fuzzy rules are used to map the voltage input index and the power input index to specific charging types. Each input combination corresponds to an output of a charging type. The following are typical fuzzy rules:

[0074] Rule 1: When the voltage input index is "low voltage" and the power input index is "low power", select constant current charging. Explanation: When the battery voltage and power are both low, the battery needs to be quickly replenished and the voltage is increased by constant current.

[0075] Rule 2: When the voltage input index is "low voltage" and the power input index is "medium power", select constant current charging. Explanation: At this time, the battery voltage is still low, but the power has increased, and constant current charging is still needed to further increase the battery voltage.

[0076] Rule 3: When the voltage input index is "medium voltage" and the power input index is "medium power", select constant voltage charging. Explanation: When the battery voltage and power are both at medium levels, constant voltage charging is used to gradually reduce the current through constant voltage control to prevent battery overheating.

[0077] Rule 4: When the voltage input index is "high voltage" and the power input index is "medium power", select constant voltage charging. Explanation: The battery voltage is already high but not fully charged, continue to control the current with constant voltage charging, gradually reduce the charging speed, and protect the battery safety.

[0078] Rule 5: When the voltage input index is "high voltage" and the power input index is "high power", select trickle charge. Explanation: When the battery is nearly full, in order to avoid overcharging, use trickle charge to maintain the battery in the best condition.

[0079] The fuzzified input variables are brought into the fuzzy rules, and the most suitable charging type is determined through the fuzzy reasoning mechanism. The reasoning process is based on the membership of the fuzzy set, and the optimal charging method is automatically selected according to different combinations of voltage and power. Through fuzzy reasoning, the output result is finally obtained, that is, the charging type that the new energy vehicle currently needs to start. According to the reasoning results, the charging method can be dynamically adjusted to improve the charging efficiency while ensuring battery safety.

[0080] The potential safety risks of target status parameters are:

[0081] Get the time series data of the target state parameters, and then calculate the standard deviation of the time series data. The purpose of calculating the standard deviation is to determine whether the target state parameters fluctuate within a relatively stable range. A smaller standard deviation means that the state parameters are stable, and a larger standard deviation means that the state may be unstable. Calculate the rate of change between two adjacent data acquisition moments: ; is a preset positive constant, The rate of change between the two adjacent data acquisition times i and i+1 can be used to detect whether the target state parameters have a risk of sudden change. If the absolute value of the rate of change is too large, it means that the target parameters have changed dramatically in a short period of time, which may be risky or abnormal. represents the data value of the target state parameter corresponding to time i, The data value of the target state parameter corresponding to time i+1 is represented by comparing the standard deviation of the time series data with the preset standard threshold value and the rate of change The absolute value of the time series data is compared with the preset standard change reference value. If the standard deviation of the time series data is less than or equal to the preset standard threshold and the change rate If the absolute value of the time series data is less than or equal to the preset standard change reference value, then there is no safety hazard in the target state parameter. If the standard deviation of the time series data is less than or equal to the preset standard threshold and the change rate is not satisfied, If the absolute value of is less than or equal to the preset standard change reference value, there is a safety hazard in the target state parameter.

[0082] The triggering conditions of the safety mechanism are based on the following judgment results:

[0083] Standard deviation exceeds the limit: If the standard deviation of the time series data exceeds the preset threshold, it means that the parameter fluctuates greatly, indicating that the battery is in an unstable state. For example, if the voltage or temperature fluctuates greatly, it may mean that the battery is overcharged, over-discharged, or has abnormal temperature.

[0084] Change rate exceeds the limit: The data change rate at adjacent time points exceeds the preset reference value, indicating that the parameters have changed dramatically in a short period of time and there is a risk of sudden changes. If the battery current or temperature change rate is large, it may indicate abnormal charging or the risk of overheating.

[0085] When the present invention determines that there is a potential safety hazard, the safety mechanism is immediately triggered and the following strategies are executed:

[0086] When abnormal fluctuations in battery parameters are detected, the present invention will first try to adjust the charging current and charging mode to balance the battery load and reduce the risk of instability. Strategy: Reduce the charging current, for example, reduce the current by 50% to reduce the internal heat of the battery. Applicable scenarios: Applicable to slight temperature fluctuations or voltage fluctuations to reduce the battery burden and gradually return the parameters to a safe range.

[0087] If the parameter fluctuation continues, the present invention will automatically switch to a safer charging mode. For situations where the voltage or power is high, switching to the trickle charging mode can avoid overcharging. Strategy: Automatically switch to constant voltage charging or trickle charging mode according to the parameter fluctuation to charge the battery in a smoother manner. Applicable scenarios: Applicable to situations where the battery is close to full charge, the temperature is high, or the voltage is close to the safety upper limit to avoid further temperature rise or voltage increase.

[0088] If the parameter fluctuation is not alleviated, and the rate of change and standard deviation exceed the safety threshold, the present invention will take measures to suspend charging to prevent potential safety accidents. Strategy: Automatically interrupt charging, wait for the battery status to return to a safe range, and then restart the charging process. Applicable scenarios: When the battery temperature exceeds 60°C, or the voltage and current change abnormally and drastically, further overheating or overcharging is prevented by suspending charging.

[0089] When it is detected that the parameters exceed the safety threshold and the rate of change is large, the present invention will trigger the alarm function, notify the user that the current battery status is abnormal, and suggest the user to stop using it immediately. Strategy: Issue a sound alarm, screen warning or send a notification to the user terminal to prompt that the current status is abnormal, and suggest the user to stop charging or check the device. Applicable scenarios: When the battery temperature rises sharply, the voltage exceeds the limit, etc., the user needs to intervene in time to avoid danger.

[0090] In different usage environments (such as low temperature or high temperature environments), the present invention can dynamically adjust the safety threshold according to the real-time monitored environmental data. For example, in a low temperature environment, the temperature threshold can be lowered to prevent internal overheating due to the low external temperature. Strategy: When the ambient temperature is below 0°C, lower the temperature threshold; when the ambient temperature is high, increase the upper temperature limit to optimize charging safety. Applicable scenarios: For special environmental conditions, avoid unnecessary alarms or safety hazards caused by environmental changes.

[0091] Case 1: Abnormal battery temperature fluctuation: During the charging process, the present invention detects that the standard deviation of the battery temperature exceeds the set threshold. At the same time, the temperature change rate in a short period of time also exceeds the safety range. Steps: The present invention first reduces the charging current by 50% to observe whether the temperature fluctuation is restored. If the temperature change rate is still large, switch to trickle charging mode and continue charging with a very small current to avoid further temperature increase. If the temperature is still out of control, suspend charging and trigger an alarm to remind the user to check the battery status. Through step-by-step adjustment and real-time monitoring, the present invention can take effective measures before the battery temperature overheats, thereby reducing safety risks.

[0092] Case 2: Battery voltage fluctuates beyond the limit: The present invention detects that the battery voltage fluctuates violently, the standard deviation exceeds the threshold, and the voltage change rate between adjacent time points exceeds the preset reference value, and there is a risk of overcharging. Steps: The present invention switches the charging mode from constant current charging to constant voltage charging mode to reduce the voltage rise rate. If the voltage still fails to stabilize, the present invention suspends charging and issues a warning to notify the user to avoid further charging. The present invention avoids further voltage over-limit by quickly adjusting the charging mode and suspending the charging operation, thereby preventing safety problems that may be caused by overcharging of the battery.

[0093] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0094] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0095] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0096] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for controlling the charging voltage of a new energy vehicle, characterized in that: The following steps are involved: Obtain each state parameter of the new energy vehicle battery before charging begins and make a safety status judgment, and determine whether the new energy vehicle battery is in a normal state based on the safety status judgment result; When the battery of the new energy vehicle is in a normal state before charging begins, a charging analysis operation is performed to obtain a voltage input index and a power input index respectively; Fuzzy reasoning is performed based on the voltage input index and the power input index to determine the type of charging to be started and to execute charging; Perform safety monitoring during the charging process. When there are safety hazards in the target state parameters, trigger the preset safety mechanism and make safety adjustments according to the preset safety strategy until the safety hazards are eliminated. The logic for obtaining the voltage input index is: Get the current battery voltage and mark it as , the minimum operating voltage of the battery and is marked as , the maximum operating voltage of the battery is marked as , the current battery temperature and marked as , standard reference temperature and marked as , the characteristic coefficients corresponding to the battery materials are marked as , the internal integrated impedance of the battery is marked as , the current battery current and is marked as , and then substitute them into the voltage input index calculation formula: ； is the voltage input index, is the preset temperature compensation coefficient; The logic for obtaining the power input index is: Get the current remaining battery power and mark it as , the total capacity of the battery and is marked as , the self-discharge rate of the battery and is marked as , the battery aging factor is marked as , the number of charge and discharge cycles of the battery is marked as , and then substitute them into the calculation formula of power input index: ; Enter the index for the quantity of electricity; The logic of fuzzy reasoning is: The voltage input index and the power input index are obtained separately and used as input variables together, and the type of new energy vehicle charging is used as the output variable. The input variables are fuzzified and the values ​​of the input variables are converted into fuzzy sets. The output variables are fuzzified and the output variables are converted into fuzzy sets. Fuzzy rules are formulated to describe the charging type requirements under different data type combinations. The fuzzified input variables are inferred through fuzzy rules to determine the type of new energy vehicle charging. The types of charging include constant current charging type, constant voltage charging type and trickle charging type.

2. A method for controlling the charging voltage of a new energy vehicle according to claim 1, characterized in that: Safety status judgment refers to: Get each state parameter separately and compare it with the corresponding normal state value range. If the target item state parameter falls within the corresponding normal state value range, the target item state parameter is in a normal state. If the target item state parameter does not fall within the corresponding normal state value range, the target item state parameter is in an abnormal state. If all state parameters are in a normal state, the new energy vehicle battery is in a normal state.

3. A method for controlling the charging voltage of a new energy vehicle according to claim 2, characterized in that: The internal impedance of the battery The acquisition logic is: Under a stable current input, the stable current is marked as , and then set n time periods t, the heat generated in each period is , then calculate the stable current The product of the square of the time period t, and then the heat generated in each cycle Divide by the product value to obtain n proportional values, and take the average value of all proportional values ​​to obtain an impedance value of one; Obtain the absolute value of the difference between the voltage data at the end of each time period t and the voltage data at the beginning under the stable current input, then calculate the average value of all absolute values ​​and divide the average value by the stable current , get impedance value 2; The internal comprehensive impedance of the battery is obtained by weighted summing the impedance value 1 and the impedance value 2. .

4. A method for controlling the charging voltage of a new energy vehicle according to claim 3, characterized in that: Battery aging factor The calculation formula is: ; Greater than zero.

5. A method for controlling the charging voltage of a new energy vehicle according to claim 4, characterized in that: The potential safety risks of target status parameters are: Get the time series data of the target state parameters, and then calculate the standard deviation of the time series data and the rate of change between two adjacent data acquisition moments: ; is a preset positive constant, Get the rate of change between time i and i+1 for two adjacent data, represents the data value of the target state parameter corresponding to time i, The data value of the target state parameter corresponding to time i+1 is represented by comparing the standard deviation of the time series data with the preset standard threshold value and the rate of change The absolute value of the time series data is compared with the preset standard change reference value. If the standard deviation of the time series data is less than or equal to the preset standard threshold and the change rate If the absolute value of the time series data is less than or equal to the preset standard change reference value, then there is no safety hazard in the target state parameter. If the standard deviation of the time series data is less than or equal to the preset standard threshold and the change rate is not satisfied, If the absolute value of is less than or equal to the preset standard change reference value, there is a safety hazard in the target state parameter.

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