CN118991471A - Method for realizing time-sharing overcharge by utilizing super capacitor - Google Patents
Method for realizing time-sharing overcharge by utilizing super capacitor Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
- B60L53/10—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles characterised by the energy transfer between the charging station and the vehicle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
- B60L53/50—Charging stations characterised by energy-storage or power-generation means
- B60L53/55—Capacitors
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Abstract
本发明公开了一种利用超级电容实现分时超充的方法，涉及电动汽车充电技术领域，包括检测电动车电池的当前电量和充电需求，确定目标充电量；基于目标充电量，将充电过程划分为N个时间段；在每个时间段起始，利用高功率充电装置对超级电容充电至第一预设值；断开超级电容与高功率充电装置的电路连接，建立超级电容与电动车电池的电路连接；采用脉冲方式控制超级电容向电动车电池传输电能，并根据电动车电池的实时温度和电量信息动态调节脉冲频率和占空比；重复执行超级电容充放电过程，直至完成N个时间段或电池充满。本发明通过将超级电容作为能量缓存单元，结合分段控制策略，在一定程度上缩短了电池充电时间。
The present invention discloses a method for realizing time-sharing supercharging by using a supercapacitor, which relates to the technical field of electric vehicle charging, including detecting the current power and charging demand of an electric vehicle battery, determining a target charging amount; dividing the charging process into N time periods based on the target charging amount; at the beginning of each time period, charging the supercapacitor to a first preset value by using a high-power charging device; disconnecting the circuit connection between the supercapacitor and the high-power charging device, and establishing a circuit connection between the supercapacitor and the electric vehicle battery; controlling the supercapacitor to transmit electric energy to the electric vehicle battery in a pulse manner, and dynamically adjusting the pulse frequency and duty cycle according to the real-time temperature and power information of the electric vehicle battery; and repeatedly executing the supercapacitor charging and discharging process until N time periods are completed or the battery is fully charged. The present invention shortens the battery charging time to a certain extent by using the supercapacitor as an energy cache unit and combining the segmented control strategy.
Description
Technical Field
The invention relates to the technical field of electric automobile charging, in particular to a method for realizing time-sharing overcharging by utilizing a super capacitor.
Background
With the rapid development of new energy automobiles, the charging technology of electric automobiles faces a plurality of challenges. In the prior art, the following problems exist in directly charging the battery of the electric automobile by adopting a high-power charger: firstly, high-current direct charging is easy to cause rapid rise of the battery temperature, and the service life of the battery is influenced; secondly, the high-frequency pulse current in the charging process can impact the charging equipment and the power grid; third, battery state of charge and temperature variations cause charging efficiency fluctuations, making it difficult to implement optimal charging strategies.
Although charging schemes using super-capacitors as buffers are currently available, the following disadvantages still exist: on the one hand, the charging parameters cannot be dynamically adjusted according to the battery state, so that the charging efficiency is low; on the other hand, the lack of fine sectional control of the charging process makes it difficult to balance the charging speed and the safety; in addition, the charge and discharge control of the super capacitor in the existing scheme is relatively simple, and the advantage of quick charge of the super capacitor cannot be fully exerted.
Disclosure of Invention
The present invention has been made in view of the problems with the existing charging schemes for electric vehicles.
Therefore, the problem to be solved by the invention is how to realize the efficient and safe charging of the battery of the electric automobile by utilizing the quick charging characteristic of the super capacitor.
In order to solve the technical problems, the invention provides the following technical scheme:
In a first aspect, an embodiment of the present invention provides a method for implementing time-sharing overcharge by using a supercapacitor, which includes detecting a current electric quantity and a charging requirement of a battery of an electric vehicle, and determining a target charging quantity; dividing a charging process into N time periods based on the target charge amount; starting at each time period, charging the super capacitor to a first preset value by using a high-power charging device; disconnecting the circuit connection of the super capacitor and the high-power charging device, and establishing the circuit connection of the super capacitor and the battery of the electric vehicle; the super capacitor is controlled to transmit electric energy to the electric vehicle battery in a pulse mode, and pulse frequency and duty ratio are dynamically adjusted according to real-time temperature and electric quantity information of the electric vehicle battery; and repeatedly executing the charging and discharging process of the super capacitor until N time periods are completed or the battery is fully charged.
As a preferable scheme of the method for realizing time-sharing overcharge by utilizing the super capacitor, the invention comprises the following steps: dividing the charging process into N time periods includes: calculating the total charging duration according to the corrected target charging amount; determining the optimal charging time length of the electric vehicle battery according to the real-time temperature value; determining an initial time period number according to the overall charging time length and the optimal charging time length; calculating the initial duration of each time period according to the initial time period number and the overall charging duration; dividing N time periods into two charging stages based on a current state of charge (SOC) value of the electric vehicle battery, wherein the charging stages comprise a fast charging stage and a slow charging stage; selecting a corresponding charging power curve according to different charging stages; the duration of each time period is dynamically adjusted according to the selected charging power profile.
As a preferable scheme of the method for realizing time-sharing overcharge by utilizing the super capacitor, the invention comprises the following steps: disconnecting the supercapacitor from the circuit of the high power charging device includes: collecting capacitance voltage values at two ends of the super capacitor, and controlling the first switching tube to be conducted when the capacitance voltage values reach a first preset value; monitoring and evaluating the electrical parameters of the output end of the LC buffer circuit, and executing the disconnection operation of the high-power charging device when the preset conditions are met; establishing circuit connection of the super capacitor and the electric vehicle battery comprises the following steps: controlling the third switching tube to be conducted, and establishing connection between the LC buffer circuit and the electric vehicle battery; collecting a channel voltage value and a channel current value in a power supply channel between a third switch tube and an electric vehicle battery; calculating the impedance value of the power supply path according to the path voltage value and the path current value; judging whether the impedance value is in a preset impedance range, and if the impedance value is in the preset impedance range, entering a pulse charging mode; the electric parameter comprises a buffer output voltage value and a buffer output current value, the preset condition comprises that the change rate of the buffer output voltage value is smaller than a second preset value, and the change rate of the buffer output current value is smaller than a third preset value.
As a preferable scheme of the method for realizing time-sharing overcharge by utilizing the super capacitor, the invention comprises the following steps: the method for dynamically adjusting the pulse frequency and the duty ratio according to the real-time temperature and the electric quantity information of the electric vehicle battery comprises the following steps: collecting a real-time temperature value and a current state of charge value of a battery of the electric vehicle; the charging control unit inquires a pulse control lookup table according to the real-time temperature value and the current state of charge value, and determines an initial pulse frequency and a duty ratio; starting pulse charging, and transmitting electric energy to the electric vehicle battery by the super capacitor through the LC buffer circuit; monitoring a first parameter set in real time in the pulse charging process; dynamically adjusting the initial pulse frequency and the duty cycle based on the first parameter set; if the current state of charge value reaches the high-order threshold value, reducing the pulse frequency and the duty ratio, and entering a slow charging stage; and stopping pulse transmission of the current charging cycle when the super capacitor voltage is reduced to the minimum working voltage threshold value or the current time period is ended, and disconnecting the circuit.
As a preferable scheme of the method for realizing time-sharing overcharge by utilizing the super capacitor, the invention comprises the following steps: the first parameter set includes super capacitor voltage, electric vehicle battery terminal voltage, charging current, and electric vehicle battery temperature.
As a preferable scheme of the method for realizing time-sharing overcharge by utilizing the super capacitor, the invention comprises the following steps: the calculation formula of the target charge amount is as follows:
；
Wherein, For a preset target state of charge value, SOC is the current state of charge value,For the rated capacity of the battery,Is the current charge efficiency coefficient.
As a preferable scheme of the method for realizing time-sharing overcharge by utilizing the super capacitor, the invention comprises the following steps: the calculation formula of the current state of charge value is as follows:
；
wherein, SOC is the current state of charge value, V is the real-time voltage value, I is the real-time current value, As the weight coefficient of the light-emitting diode,、、Respectively minimum operating voltage, maximum operating voltage and average operating voltage of the battery,As a result of the initial state of charge value,For battery rated capacity, dt is the sampling time interval.
In a second aspect, an embodiment of the present invention provides a system for implementing time-sharing overcharge using a supercapacitor, which includes a battery status detection module configured to detect a current electric quantity and a charging demand of an electric vehicle battery, and determine a target charging quantity; the charging process planning module is used for dividing the charging process into N time periods based on the target charging amount; the super capacitor charging module is used for charging the super capacitor to a first preset value by utilizing the high-power charging device at the beginning of each time period; the circuit switching control module is used for disconnecting the circuit connection between the super capacitor and the high-power charging device and establishing the circuit connection between the super capacitor and the battery of the electric vehicle; the pulse charging control module is used for controlling the super capacitor to transmit electric energy to the electric vehicle battery in a pulse mode and dynamically adjusting pulse frequency and duty ratio according to real-time temperature and electric quantity information of the electric vehicle battery; and the charging cycle execution module is used for repeatedly executing the charging and discharging process of the super capacitor until N time periods are completed or the battery is fully charged.
The beneficial effects of the invention are as follows: according to the invention, the super capacitor is used as an energy buffer unit, and the sectional control strategy is combined, so that the battery charging time is shortened to a certain extent. In particular the application of LC buffer circuits, helps to reduce voltage fluctuations in conventional direct charge schemes. Meanwhile, the pulse charging control method based on impedance monitoring improves the charging efficiency on the premise of ensuring the charging safety by dynamically adjusting the pulse parameters. In addition, the triple switching tube cooperative control and protection mechanism adopted by the invention can better control the temperature change in the charging process, improve the charging uniformity, and has positive effect on protecting the service life of the battery.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following brief description will be given of the drawings aimed at being used in the description of the embodiments, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without the need of inventive effort for a person skilled in the art.
Fig. 1 is a flow chart of a method for implementing time-sharing overcharge by using a supercapacitor.
Fig. 2 is a basic topology of a charging system using a super capacitor to implement a time-sharing super charging method.
Fig. 3 is a flowchart of the duration calculation of a method for implementing time-sharing overcharge by using a supercapacitor.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Embodiment 1, referring to fig. 1 to 3, is a first embodiment of the present invention, which provides a method for implementing time-sharing overcharge by using a supercapacitor,
It should be noted in advance that, as shown in fig. 2, the charging system of the present embodiment mainly includes a high-power charging device, a super capacitor module, an LC buffer circuit and a switch control circuit. The high-power charging device is used for rapidly charging the super capacitor; the super capacitor module is used as an energy buffer unit and used for storing electric energy provided by the high-power charging device; the LC buffer circuit is composed of an inductor L and a capacitor C and is used for smoothing voltage and current fluctuation and reducing electromagnetic interference.
The switch control circuit comprises three main switching tubes: the first switching tube controls the connection between the super capacitor and the LC buffer circuit; the second switching tube controls the connection between the high-power charging device and the super capacitor; the third switching tube controls connection between the LC buffer circuit and the electric vehicle battery. All the switching tubes adopt high-reliability power MOSFET or IGBT devices and have the safety characteristics of overcurrent protection, overvoltage protection and the like.
Furthermore, the basic topology of the charging system is as shown in fig. 2: the high-power charging device is connected with the super capacitor through the second switching tube, the super capacitor is connected with the input end of the LC buffer circuit through the first switching tube, and the output end of the LC buffer circuit is connected with the electric vehicle battery through the third switching tube.
Based on the above hardware structure, the method flowchart of the present embodiment is as shown in fig. 1, and includes the following steps:
s1: and detecting the current electric quantity and the charging requirement of the electric vehicle battery, and determining a target charging quantity.
Specifically, the battery management system is electrically connected with the electric vehicle battery, acquires a real-time voltage value V, a real-time current value I and a real-time temperature value T of the electric vehicle battery, and performs filtering and abnormal value processing on the acquired data; according to the real-time voltage value V and the real-time current value I, the current state of charge value SOC of the electric vehicle battery is calculated, and the specific formula is as follows:
；
wherein, SOC is the current state of charge value, V is the real-time voltage value, I is the real-time current value, As the weight coefficient of the light-emitting diode,、、Respectively minimum operating voltage, maximum operating voltage and average operating voltage of the battery,As a result of the initial state of charge value,For battery rated capacity, dt is the sampling time interval.
Further, a target charge amount is calculatedThe process is as follows: subtracting the current state of charge value from the preset target state of charge value to obtain a state of charge difference value; reading the electric vehicle battery capacity parameter, and multiplying the electric vehicle battery capacity parameter by the state of charge difference value to obtain a theoretical target charge quantity; calculating a current charging efficiency coefficient based on the real-time temperature value T; and correcting the theoretical target charge amount by using the current charge efficiency coefficient to obtain a corrected target charge amount, wherein the specific formula is as follows:
；
Wherein, For a preset target state of charge value, SOC is the current state of charge value,For the rated capacity of the battery,The specific formula is as follows for the current charging efficiency coefficient:
；
Wherein, T is a real-time temperature value for the current charging efficiency coefficient），In order to achieve an optimum operating temperature, the temperature of the gas,Is the temperature deviation threshold value [ ]），、The highest operating temperature and the lowest operating temperature allowed by the electric vehicle battery are respectively.
Further, the corrected target charge amount is transmitted to the charge control unit for time period division and charge policy formulation in the subsequent charge process.
S2: based on the target charge amountThe charging process is divided into N time periods.
Specifically, the method comprises the following steps:
S2.1: according to the corrected target charge amount Calculating an overall charge duration。
Specifically, the overall charge durationThe calculation formula of (2) is as follows:
；
Wherein, For the total charge duration period of time,To the corrected target charge amount,For the power rating of the charging system,The average charging efficiency is usually 0.8 to 0.9.
S2.2: and determining the optimal charging time length of the electric vehicle battery according to the real-time temperature value T.
Specifically, a corresponding optimal charging time length is obtained by searching a temperature-optimal charging time length relation data table; if the real-time temperature value T does not correspond to the lookup table accurately, the real-time temperature value T is obtained through calculation by a linear interpolation method.
S2.3: dividing the total charging time period by the optimal charging time period, and rounding up to obtain an initial time period number N.
It should be noted that, the rounding up is to ensure that the charging process can cover the whole target charging amount, avoid the charging deficiency, and N should be not less than 2.
S2.4: the initial duration of each time period is calculated from the initial time period number N and the overall charge duration.
Specifically, the calculation formula of the initial duration is as follows:
；
Wherein, For the initial duration of each time period,For the total charge duration, N is the initial period number.
S2.5: based on the current state of charge value SOC of the electric vehicle battery, the N time periods are divided into two charging phases.
Specifically, the charging stage includes a fast charging stage and a slow charging stage, and the dividing process is as follows: according to the current state of charge value SOC of the battery, calculating the fast charge stage proportion, wherein the calculation formula is as follows:
；
wherein, SOC is the current state of charge value.
Further, the function is such that: when the SOC is less than 0.2, the quick charge stage ratio is 1; when the SOC is greater than or equal to 0.2 and less than 0.8, the quick charge stage ratio decreases linearly with increasing SOC; when the SOC is greater than or equal to 0.8, the rapid charge stage ratio is 0%.
Further, according to the calculated fast charging stage proportion, the number of time periods of the fast charging stage is determined, the corresponding number of time periods are divided into fast charging stages, and the remaining time periods are divided into slow charging stages.
Preferably, by the mode, smooth transition of the charging strategy along with the change of the SOC is realized, so that the rapid charging requirement at low SOC is ensured, excessive rapid charging at high SOC is avoided, and the charging efficiency is improved and the service life of the battery is prolonged.
S2.6: and selecting a corresponding charging power curve from a preset charging power curve library according to different charging stages.
In this embodiment, a constant-current charging curve is selected in the fast charging stage, and a constant-voltage charging curve is selected in the slow charging stage.
S2.7: the duration of each time period is dynamically adjusted according to the selected charging power profile.
Specifically, the dynamic adjustment process is as follows: upon initialization of each time period, determining an initial charge power for the time period based on the selected charge power curve; continuously monitoring the actual charge amount during the execution of the time period; at the end of each period, a deviation of the actual charge amount from the theoretical expected charge amount is calculated. Based on the deviation, the duration of the subsequent time period is adjusted accordingly: moderately extending the duration of the next time period when the actual charge amount is lower than expected; when the actual charge amount exceeds the expected amount, the duration of the next period is moderately shortened. This dynamic adjustment process is repeated until all of the predetermined time periods have ended. If the target charge amount is not achieved after the final time period is finished, continuing to prolong the duration of the last time period until the target charge amount requirement is met.
In addition, the adjustment amplitude is proportional to the difference, but the maximum adjustment limit (e.g., + -10% of the original duration) is set to avoid excessive fluctuation. Meanwhile, according to the adjusted duration, the charging power of the next time period is finely adjusted so as to keep consistency with the charging power curve.
S2.8: the durations of the N time periods and the corresponding charging power values are transmitted to a charging control unit for control of a subsequent charging process.
It should be noted that, the flowchart of duration calculation is shown in fig. 3.
S3: and at the beginning of each time period, charging the super capacitor to a first preset value by using the high-power charging device.
Specifically, the first preset value refers to a target charging voltage value of the supercapacitor, and the preset value is determined by the following manner: firstly, increasing a margin of 12% on the basis of the nominal voltage of an electric vehicle battery, and compensating the voltage drop loss in the subsequent charging process; then determining a voltage constraint condition that the upper voltage limit value cannot exceed 90% of rated voltage of the super capacitor; finally, limiting the initial voltage value in the constraint condition to obtain a final first preset value.
Furthermore, the invention adopts a constant power charging mode to charge the super capacitor. In the initial stage of charging, namely when the capacity of the super capacitor is 0-50%, controlling the maximum charging current not to exceed 1.5 times of the rated current so as to realize quick charging; when the capacity reaches 50-80%, limiting the maximum charging current to be within 1.2 times of the rated current, and avoiding excessive charging stress while ensuring the charging efficiency; when the capacity exceeds 80%, a linear regulation strategy is adopted to gradually reduce the charging current to 0.5 times of the rated current, so that the super capacitor is protected and the service life of the super capacitor is prolonged.
It should be noted that, during the whole charging process, the system continuously monitors the temperature change of the super capacitor. As soon as a temperature exceeding the threshold of 85 ℃ is detected, the control unit immediately reduces the charging power to 50% of the rated power until the temperature falls within the safe range. The dynamic temperature management strategy not only ensures the safety of the charging process, but also effectively avoids the performance attenuation of the super capacitor caused by overheat.
Preferably, through the sectional control strategy, the efficiency of the charging process of the super capacitor is guaranteed, and the effective protection of the super capacitor is realized. Meanwhile, through the cooperation of temperature monitoring and a power adjusting mechanism, the safety and the reliability of the charging process are ensured.
S4: and disconnecting the circuit connection of the super capacitor and the high-power charging device, and establishing the circuit connection of the super capacitor and the battery of the electric vehicle.
Specifically, the method comprises the following steps:
s4.1: and collecting capacitance voltage values at two ends of the super capacitor, and controlling the first switching tube to be conducted when the capacitance voltage values reach a first preset value.
One end of the first switching tube is connected with the super capacitor in series, and the other end of the first switching tube is connected with the input end of the LC buffer circuit.
S4.2: and monitoring and evaluating the electrical parameters of the output end of the LC buffer circuit, judging the stability of the system, and executing the disconnection operation of the high-power charging device when the preset condition is met.
Specifically, continuously collecting a buffer output voltage value and a buffer output current value of an output end of the LC buffer circuit; the buffer output voltage value and the rate of change of the buffer output current value are calculated, and in this embodiment, a sliding window method is used for calculating the rate of change.
Further, whether the system meets the condition that the change rate of the buffer output voltage value is smaller than a second preset value or not is judged, and the change rate of the buffer output current value is smaller than a third preset value, if yes, the disconnection operation of the high-power charging device is executed. The disconnecting operation includes: controlling the high-power charging device to gradually reduce the output power, wherein the reduction rate is not more than 10% of rated power per second; when the output power of the high-power charging device is reduced to 10% or below of rated power, the second switching tube is controlled to be disconnected, and the circuit connection between the high-power charging device and the super capacitor is cut off.
In this embodiment, the second preset value, the third preset value, and the predetermined time period T are dynamically adjusted according to the current charging stage and the battery characteristics. In the quick charge stage, the value range of the second preset value is 0.3V to 0.7V per millisecond, the value range of the third preset value is 0.5A to 1.5A per millisecond, and the preset time length T is not less than 100 milliseconds. In the slow charge phase, the parameter value should be reduced appropriately, and the specific value is calculated automatically by the system according to the battery characteristics and the charging requirement. The size k of the sliding window is typically chosen to be 10 to 20 to balance the response speed and noise immunity.
S4.3: and controlling the third switching tube to be conducted, and establishing connection between the LC buffer circuit and the electric vehicle battery.
The input end of the third switching tube is electrically connected with the output end of the LC buffer circuit, and the output end of the third switching tube is electrically connected with the electric vehicle battery.
S4.4: and collecting a channel voltage value and a channel current value in a power supply channel between the third switch tube and the electric vehicle battery.
S4.5: and calculating the impedance value of the power supply path according to the path voltage value and the path current value.
Specifically, the impedance value is calculated as follows:
；
Wherein Z is the impedance value of the power supply path, As the value of the via voltage,Is the via current value.
S4.6: judging whether the impedance value is in a preset impedance range, and if the impedance value is in the preset impedance range, entering a pulse charging mode.
It should be noted that, the upper limit value of the preset impedance range is 120% of the nominal impedance value of the power supply path, and the lower limit value of the preset impedance range is 80% of the nominal impedance value of the power supply path, so that the design is to find possible abnormality of the power supply path, such as poor contact or short circuit, while ensuring the charging efficiency.
In addition, parameters of the pulse charging mode are dynamically adjusted according to the charging phases (fast charging or slow charging) divided in S2. In the fast charging stage, pulses with higher frequency and duty cycle are adopted; in the slow charge phase, pulses with lower frequency and duty cycle are used to optimize the charge efficiency and protect the battery.
S5: and the super capacitor is controlled to transmit electric energy to the electric vehicle battery in a pulse mode, and the pulse frequency and the duty ratio are dynamically adjusted according to the real-time temperature and electric quantity information of the electric vehicle battery.
Specifically, the method comprises the following steps:
s5.1: and acquiring a real-time temperature value T and a current state of charge value SOC of the electric vehicle battery, and transmitting the real-time temperature value T and the current state of charge value SOC to a charging control unit.
It should be noted that the data acquisition should be performed after the super capacitor is connected with the electric vehicle battery through the third switch tube, so as to ensure the real-time performance and accuracy of the data.
S5.2: and the charging control unit inquires a pulse control lookup table according to the real-time temperature value T and the current state of charge value SOC, and determines the initial pulse frequency and the duty ratio.
It should be noted that the pulse control lookup table is preset based on parameters such as the battery type, SOC, temperature, etc. and is used for optimizing the pulse charging process. When the SOC is low, a higher pulse frequency and a larger duty cycle are selected; when the SOC is higher, the pulse frequency and the duty cycle are gradually reduced, so that the smooth transition of the charging process is ensured.
S5.3: and starting pulse charging, and transmitting electric energy to the electric vehicle battery by the super capacitor in an intermittent mode through the LC buffer circuit.
The LC buffer circuit consists of an inductor L and a capacitor C and is used for smoothing voltage and current fluctuation and reducing instantaneous impact on a battery in the charging process. The pulse period is determined by the pulse frequency and the charge duration is determined by the duty cycle.
S5.4: the first parameter set is monitored in real time during the pulse charging process.
The first parameter set comprises super capacitor voltage, electric vehicle battery terminal voltage, charging current and electric vehicle battery temperature.
S5.5: based on the first parameter data, the initial pulse frequency and the duty cycle are dynamically adjusted.
Specifically, the charging control unit firstly calculates a difference value between the voltage of the super capacitor and the voltage of the battery terminal of the electric vehicle. When the difference is smaller than a preset minimum voltage difference threshold, the control unit pauses the current charging period and triggers the recharging process of the super capacitor. During the charging process, if the charging current is detected to exceed the preset maximum current threshold, the control unit correspondingly reduces the duty ratio so as to prevent the battery from being damaged by the excessive current. Meanwhile, the system continuously monitors the temperature of the battery of the electric vehicle, once the temperature exceeds a preset maximum temperature threshold, the control unit simultaneously reduces the pulse frequency and the duty cycle, and even pauses charging if necessary until the temperature falls within a safe range.
Preferably, through the real-time monitoring and dynamic adjustment mechanism of the multiple parameters, the system can protect the safety of the battery to the maximum extent and optimize the charging process while ensuring the charging efficiency.
S5.6: if the current state of charge value SOC reaches the high-order threshold value, the pulse frequency and the duty ratio are gradually reduced, and a slow charging stage is entered.
Specifically, the charge control unit continuously monitors the SOC value of the battery. Upon detecting that the SOC exceeds soc_high, the system starts to perform the charge mode conversion. In this process, the pulse frequency f and the duty ratio D gradually decrease in accordance with a predetermined curve. This gradual adjustment ensures a smooth transition of the charging process, avoiding the negative effects that abrupt current changes may have on the battery. The slow charging stage adopts lower pulse frequency and duty ratio, and the main purpose is to accurately control the charging process, prevent overcharging, protect the battery to the greatest extent and prolong the service life of the battery.
S5.7: and stopping pulse transmission of the current charging cycle and disconnecting the circuit when the super capacitor voltage is reduced to the minimum working voltage threshold value or the current time period is ended.
Specifically, the charge control unit continuously monitors the super-capacitor voltage, the current time and the current state of charge value SOC. Upon detecting that either condition is met, the control unit immediately sends a signal to stop the pulse transmission. The system then opens the third switching tube, the first switching tube and the second switching tube in a predetermined sequence, ensuring a safe disconnection of the circuit.
S6: and repeatedly executing the charging and discharging process of the super capacitor until N time periods are completed or the battery is fully charged.
After each charging cycle is completed, the system first evaluates whether the termination condition of the overall charging process is satisfied. If the condition is not satisfied, returning to the step S3, and starting a new round of super capacitor charging. During this process, the system dynamically adjusts the charging parameters based on the data from previous cycles, such as adjusting the duration of each time period or modifying the initial frequency and duty cycle of the pulsed charge to optimize the subsequent charging efficiency.
In addition, the system also monitors the battery temperature T in real time, and if the temperature T exceeds the preset highest safe temperature, the charging process is suspended until the temperature falls within the safe range. When the termination condition is met, the system performs a final safety check, including confirming that all switching tubes have been turned off, and recording the overall data for the entire charging process, and then completely exits the charging mode.
Further, the embodiment also provides a system for realizing time-sharing overcharging by utilizing the supercapacitor, which comprises a battery state detection module, a target charging amount determination module and a battery state detection module, wherein the battery state detection module is used for detecting the current electric quantity and the charging requirement of the battery of the electric vehicle; the charging process planning module is used for dividing the charging process into N time periods based on the target charging amount; the super capacitor charging module is used for charging the super capacitor to a first preset value by utilizing the high-power charging device at the beginning of each time period; the circuit switching control module is used for disconnecting the circuit connection between the super capacitor and the high-power charging device and establishing the circuit connection between the super capacitor and the battery of the electric vehicle; the pulse charging control module is used for controlling the super capacitor to transmit electric energy to the electric vehicle battery in a pulse mode and dynamically adjusting pulse frequency and duty ratio according to real-time temperature and electric quantity information of the electric vehicle battery; and the charging cycle execution module is used for repeatedly executing the charging and discharging process of the super capacitor until N time periods are completed or the battery is fully charged.
In summary, the super capacitor is used as the energy buffer unit, and the sectional control strategy is combined, so that the battery charging time is shortened to a certain extent. In particular the application of LC buffer circuits, helps to reduce voltage fluctuations in conventional direct charge schemes. Meanwhile, the pulse charging control method based on impedance monitoring improves the charging efficiency on the premise of ensuring the charging safety by dynamically adjusting the pulse parameters. In addition, the triple switching tube cooperative control and protection mechanism adopted by the invention can better control the temperature change in the charging process, improve the charging uniformity, and has positive effect on protecting the service life of the battery.
Embodiment 2, referring to fig. 1 to 3, is a second embodiment of the present invention, and this embodiment provides a method for implementing time-sharing overcharge by using a supercapacitor, so as to verify the beneficial effects of the present invention, and perform scientific demonstration through economic benefit calculation and simulation experiments.
First, in the initial condition setting, the battery initial SOC is 25%, the ambient temperature is 28 ℃, and the target charge SOC is 80%. The charging process is divided into 12 time periods, wherein the fast charging period takes 7 time periods and the slow charging period takes 5 time periods. The initial frequency of pulse charging was set at 800Hz and the duty cycle was 70%. The charging threshold of the super capacitor is set to 450V, and the minimum working voltage is 150V. To ensure data reliability, each set of experiments was repeated 3 times, taking the average as the final result.
Thereafter, during the experiment, the data acquisition system recorded the key parameters with a sampling period of 2 ms. When the battery SOC is in the range of 25% -40%, the charging current is stabilized at about 180A, the charging power reaches 180kW, and the temperature of the battery is slowly increased from 28 ℃ to 35 ℃. With the SOC rising to 40% -60%, the system automatically reduces the charging current to 140A, the charging power to 150kW, and the battery temperature continues to rise to 39 ℃. When the SOC reaches 60% -80%, the charging current is further reduced to 90A, the charging power is reduced to 100kW, and the temperature of the battery is finally stabilized at 42 ℃.
Next, the experimental results showed that the entire charging process took 45 minutes, and the average charging efficiency reached 89.5%. The cycle efficiency of the super capacitor is kept above 92%, the temperature is raised to 58 ℃ at the highest, and the temperature protection mechanism is not triggered. The voltage ripple coefficient of the battery terminal is controlled within 1.8%, the charging curve is smooth, and no obvious oscillation occurs. Through impedance monitoring, the impedance value of the power supply path is always kept within +/-15% of the nominal value, which indicates that the system stability is good.
Finally, the advantages of the present invention over the conventional direct charging approach are shown in table 1.
TABLE 1 comparison of Performance indicators of the present invention with the traditional direct charging method
In summary, experimental data show that compared with the traditional direct charging mode, the scheme of the invention has improved key indexes such as charging time, charging power, charging efficiency and the like. Particularly, on the premise of ensuring the safety of the battery, the charging time of 25% -80% is shortened by 22.4%, meanwhile, the voltage ripple is reduced by 28.0%, and the charging process is more stable. The data show that the invention has certain application value in the field of electric automobile quick charging.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.
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