CN109950661B - Device and method for simultaneously heating inside and outside of power battery pack - Google Patents
Device and method for simultaneously heating inside and outside of power battery pack Download PDFInfo
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- 238000010438 heat treatment Methods 0.000 title claims abstract description 150
- 238000000034 method Methods 0.000 title claims abstract description 39
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 13
- 238000005070 sampling Methods 0.000 claims description 37
- 230000010287 polarization Effects 0.000 claims description 30
- 230000005284 excitation Effects 0.000 claims description 29
- 230000002457 bidirectional effect Effects 0.000 claims description 19
- 239000003990 capacitor Substances 0.000 claims description 14
- 230000006870 function Effects 0.000 claims description 14
- 230000020169 heat generation Effects 0.000 claims description 11
- 238000007599 discharging Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 238000001453 impedance spectrum Methods 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 2
- 238000009826 distribution Methods 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 6
- 238000007796 conventional method Methods 0.000 abstract description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- 238000011217 control strategy Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
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Abstract
A device and a method for simultaneously heating the inside and the outside of a power battery pack relate to the technical field of heating of lithium ion power batteries. The invention solves the problem that the battery use effect is influenced by uneven heating temperature distribution in the conventional method for heating the power battery pack at low temperature by adopting external heating. The invention firstly judges the electric quantity of the battery, and does not start the self-heating process when the electric quantity is low, thereby avoiding the over-discharge of the battery. External heating by the heating film is started when the battery charge is sufficient, and the uneven distribution of temperature by the external heating is adjusted by the internal heating. The internal heating firstly makes even groups of sub battery packs, every two groups of sub battery packs form a self-heating unit, a temperature sensor is adopted to collect the surface temperature of one group of sub battery packs in all the self-heating units, the collected temperatures are compared, and only the group with the lowest temperature is internally heated, so that the aim of uniformly distributing the temperature is fulfilled. The invention is suitable for preheating the power battery pack.
Description
Technical Field
The invention relates to the technical field of heating of lithium ion power batteries.
Background
Along with the generation of energy problems, the nation supports the new energy industry greatly, and lithium ion batteries become important energy storage elements due to the advantages of high energy density, low self-discharge rate, no memory effect and the like, and are widely applied to the fields of new energy power stations, electric vehicles and the like.
Due to the internal structure and electrochemical properties of lithium batteries, the charge and discharge performance of lithium batteries is a major problem at low temperatures. The activity of the active species decreases at low temperatures and the internal diffusion rate decreases. The internal impedance of the lithium ion battery is greatly increased at low temperature, the output power is reduced, and meanwhile, the available battery capacity is correspondingly reduced. Meanwhile, the lithium battery is used at low temperature, so that the problems of lithium precipitation of the negative electrode and the like exist, and the low-temperature heating of the lithium battery becomes necessary. And the adoption of an external heating mode has the problem of uneven temperature distribution.
Disclosure of Invention
The invention provides a device and a method for simultaneously heating the inside and the outside of a power battery pack, aiming at solving the problems that the use effect of a battery is influenced by uneven heating temperature distribution in the conventional method for heating the power battery pack at low temperature by adopting external heating.
The invention relates to a device for simultaneously heating the inside and the outside of a power battery pack, which is applied to the power battery pack comprising 2N sub-battery packs and comprises a heating film 1, 2N switching circuits 3, N temperature sensors 4, a bidirectional DC/DC converter 5, a sampling circuit 6 and a control unit 7;
the heating film 1 is arranged on the outer side of the power battery pack and used for externally heating the power battery pack; the heating power control signal input end of the heating film 1 is connected with the external heating control signal output end of the control unit 7;
two sub-battery packs which are arranged symmetrically with an axis in the internal space of the power battery pack form a self-heating unit, a temperature sensor 4 is arranged in each self-heating unit, the temperature sensor 4 is used for collecting the surface temperature signal of any one sub-battery pack in the self-heating unit, and the temperature signal output ends of the N temperature sensors 4 are all connected with the temperature signal input end of the control unit 7;
the charge and discharge signal input and output ends of one group of sub-battery packs in each self-heating unit are connected with the signal input and output ends on one side of the bidirectional DC/DC converter 5 through a switch circuit 3, and the charge and discharge signal input and output ends of the other group of sub-battery packs are connected with the signal input and output ends on the other side of the bidirectional DC/DC converter 5 through a switch circuit 3; the control signal input ends of the 2N switching circuits 3 are connected with the switch control signal output end of the control unit 7;
the sampling circuit 6 is respectively connected with a group of sub battery packs in the N self-heating units through the N switch circuits 3 and is used for collecting the current, terminal voltage and charge state of the connected sub battery packs; the signal output end of the sampling circuit 6 is connected with the sampling signal input end of the control unit 7.
A heating control method of a device for simultaneously heating the inside and the outside of a power battery pack is realized based on the device for simultaneously heating the inside and the outside of the power battery pack, and the method comprises the following specific steps:
step one, putting a certain group of sub battery packs into a sampling loop, collecting the charge state soc of the sub battery packs, and judging whether the charge state soc is larger than a set charge state threshold socsetIf so, executing the step two, otherwise, keeping the battery pack in a low-power state, and repeatedly executing the step one, soc, in order to prevent the battery from over-discharging and not carrying out the self-heating processsetIs a positive number;
step two, collecting the temperature T in the N self-heating units, and judging the lowest temperature value T in the N self-heating unitsminWhether or not less than a temperature threshold TsetIf yes, executing the third step, otherwise, returning to execute the first step; wherein, TsetIs a positive number;
step three, controlling the heating film 1 to start external heating on the power battery pack 2; while collecting the temperature as the lowest value TminThe terminal voltage U and the battery current I of one sub-battery pack in the self-heating unit;
step four, establishing the temperature as the minimum value TminThe first-order Davining equivalent circuit model of the sub-battery pack utilizes the terminal voltage U and the battery current I of the sub-battery pack acquired in the third step to perform the following operation on the internal parameters of the sub-battery pack: ohmic internal resistance R0Internal resistance to polarization R1And a polarization capacitor C1Performing identification;
step five, according toOhmic internal resistance R identified in step four0Internal resistance to polarization R1And a polarization capacitor C1Identifying to obtain total internal impedance and alternating excitation frequency functions of the two groups of power batteries;
step six, obtaining the minimum value T of the temperature by using the total impedance and frequency function and the heat generation rate formula in the battery obtained in the step fiveminThe optimum excitation heating frequency of the sub-battery pack of (1);
step seven, setting the temperature as the minimum value TminThe optimum heating excitation frequency of the sub-battery is used as the optimum alternating switching frequency of the bidirectional DC/DC converter to make the temperature be the minimum value TminTwo groups of sub battery packs in the self-heating unit to which the sub battery packs belong alternately discharge to realize the minimum value T of temperatureminAfter time t1, the method returns to the step one, wherein t1 is a positive number.
The power battery pack is heated by adopting two modes of internal heating and external heating, so that the effect of quickly preheating the power battery pack is realized. The method comprises the steps of firstly judging the electric quantity of the battery, and not starting a self-heating process when the electric quantity is low, so that the over-discharge of the battery is avoided. External heating by the heating film is started when the battery charge is sufficient, and the uneven distribution of temperature by the external heating is adjusted by the internal heating. The internal heating firstly makes even groups of sub-battery packs, each two groups of sub-battery packs form a self-heating unit, and because two symmetrical batteries often have similar temperature characteristics, two battery packs positioned in the same self-heating unit are spatially symmetrical by the central shaft of the whole power battery pack. The temperature sensors are adopted to collect the surface temperatures of a group of sub-battery packs in all the self-heating units, the collected temperatures are compared, and only the group with the lowest temperature is internally heated, so that the aim of uniformly distributing the temperatures is fulfilled. The lowest temperature group is connected to the bidirectional DC/DC converter through the switching circuit. And the optimal alternating excitation heating frequency of the battery pack is obtained, and the optimal heating frequency is used as the alternating switching frequency of the bidirectional DC/DC converter.
Drawings
FIG. 1 is a schematic structural diagram of a device for simultaneously heating the inside and the outside of a power battery pack according to the present invention;
FIG. 2 is a flow chart illustrating a heating control method of the simultaneous internal and external heating apparatus of the power battery pack according to the present invention;
fig. 3 is a diagram of an equivalent circuit model of a first-order thevenin according to the fourth embodiment.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the accompanying drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the corresponding technical effects can be fully understood and implemented. The embodiments and the features of the embodiments can be combined without conflict, and the technical solutions formed are all within the scope of the present invention.
The first embodiment is as follows: the present embodiment will be described with reference to fig. 1, and the apparatus for simultaneously heating the inside and the outside of a power battery pack according to the present embodiment is applied to a power battery pack 2 including 2N sub-battery packs, and includes a heating film 1, 2N switching circuits 3, N temperature sensors 4, a bidirectional DC/DC converter 5, a sampling circuit 6, and a control unit 7;
the heating film 1 is arranged on the outer side of the power battery pack and used for externally heating the power battery pack; the heating power control signal input end of the heating film 1 is connected with the external heating control signal output end of the control unit 7;
two sub-battery packs which are arranged symmetrically with an axis in the internal space of the power battery pack form a self-heating unit, a temperature sensor 4 is arranged in each self-heating unit, the temperature sensor 4 is used for collecting the surface temperature signal of any one sub-battery pack in the self-heating unit, and the temperature signal output ends of the N temperature sensors 4 are all connected with the temperature signal input end of the control unit 7;
the charge and discharge signal input and output ends of one group of sub-battery packs in each self-heating unit are connected with the signal input and output ends on one side of the bidirectional DC/DC converter 5 through a switch circuit 3, and the charge and discharge signal input and output ends of the other group of sub-battery packs are connected with the signal input and output ends on the other side of the bidirectional DC/DC converter 5 through a switch circuit 3; the control signal input ends of the 2N switching circuits 3 are connected with the switch control signal output end of the control unit 7;
the sampling circuit 6 is respectively connected with a group of sub battery packs in the N self-heating units through the N switch circuits 3 and is used for collecting the current, terminal voltage and charge state of the connected sub battery packs; the signal output end of the sampling circuit 6 is connected with the sampling signal input end of the control unit 7.
The second embodiment is as follows: in this embodiment, the device for heating the inside and the outside of the power battery pack at the same time in the first embodiment is further described, wherein the sampling circuit 6 includes a current sampling circuit, a voltage sampling circuit and a state of charge sampling circuit, the current sampling circuit is used for collecting the current of the connected sub-battery pack, the voltage sampling circuit is used for the terminal voltage of the connected sub-battery pack, and the state of charge sampling circuit is used for collecting the state of charge of the connected sub-battery pack.
The third concrete implementation mode: referring to fig. 2, a heating control method for a simultaneous internal and external heating device of a power battery pack according to this embodiment is described, and the method is implemented based on the simultaneous internal and external heating device of the power battery pack according to the embodiment, and includes the following specific steps:
step one, putting a certain group of sub battery packs into a sampling loop, collecting the charge state soc of the sub battery packs, and judging whether the charge state soc is larger than a set charge state threshold socsetIf so, executing the step two, otherwise, keeping the battery pack in a low-power state, and repeatedly executing the step one, soc, in order to prevent the battery from over-discharging and not carrying out the self-heating processsetIs a positive number;
step two, collecting the temperature T in the N self-heating units, and judging the lowest temperature value T in the N self-heating unitsminWhether or not less than a temperature threshold TsetIf yes, executing the third step, otherwise, returning to execute the first step; wherein, TsetIs a positive number;
step three, control and addThe hot film 1 starts to externally heat the power battery pack 2; while collecting the temperature as the lowest value TminThe terminal voltage U and the battery current I of one sub-battery pack in the self-heating unit;
step four, establishing the temperature as the minimum value TminThe first-order Davining equivalent circuit model of the sub-battery pack utilizes the terminal voltage U and the battery current I of the sub-battery pack acquired in the third step to perform the following operation on the internal parameters of the sub-battery pack: ohmic internal resistance R0Internal resistance to polarization R1And a polarization capacitor C1Performing identification;
step five, according to the ohmic internal resistance R identified in the step four0Internal resistance to polarization R1And a polarization capacitor C1Identifying to obtain total internal impedance and alternating excitation frequency functions of the two groups of power batteries;
step six, obtaining the minimum value T of the temperature by using the total impedance and frequency function and the heat generation rate formula in the battery obtained in the step fiveminThe optimum excitation heating frequency of the sub-battery pack of (1);
step seven, setting the temperature as the minimum value TminThe optimum heating excitation frequency of the sub-battery is used as the optimum alternating switching frequency of the bidirectional DC/DC converter to make the temperature be the minimum value TminTwo groups of sub battery packs in the self-heating unit to which the sub battery packs belong alternately discharge to realize the minimum value T of the contrastminAfter time t1, the method returns to the step one, wherein t1 is a positive number.
In this embodiment, the implementation method of putting a certain group of sub-battery packs into the sampling loop to collect the state of charge soc of the sub-battery pack in the step one is to control one of the 2N switch circuits 3 to be closed, and implement the sampling circuit to sample the state of charge of one group of sub-battery packs in the 2N sub-battery packsminOnly one group of the steps from the second step to the seventh step needs to be selected arbitrarily,because the outside heats simultaneously, after heating time t1, the temperature of all sub-group battery all can change, simultaneously, because the position of two sets of sub-group battery in every self-heating unit becomes spatial symmetry with the axis of the whole inner space of group battery, consequently, the surface temperature difference of two sets of sub-group battery of a self-heating unit is very little, consequently, only need adopt a temperature sensor to gather the temperature of the sub-group battery in a self-heating unit just can. In the seventh step, the temperature is set to be the minimum value TminThe optimum heating excitation frequency of the sub-battery is used as the optimum alternating switching frequency of the bidirectional DC/DC converter to make the temperature be the minimum value TminTwo groups of sub battery packs in the self-heating unit to which the sub battery packs belong alternately discharge to realize the minimum value T of temperatureminThe sub-battery packs perform excitation heating. The specific process comprises the following steps: the control unit controls the alternating switching current direction of the bidirectional DC/DC converter by using the obtained optimal heating excitation frequency of the sub-battery pack as an optimal alternating switching frequency control signal, and the control unit controls the temperature to be the minimum value T simultaneouslyminThe two switch circuits 3 of the self-heating unit of the sub-battery pack are closed, so that the temperature of the bidirectional DC/DC converter and the same temperature of the bidirectional DC/DC converter is the minimum value TminIs connected with the two sub-battery packs of the self-heating unit, thereby realizing the minimum value T of the temperatureminThe sub-battery packs perform excitation heating.
The fourth concrete implementation mode: referring to fig. 3, the present embodiment will be described further with reference to the method for controlling the heating of the simultaneous internal and external heating devices of the power battery pack in the third embodiment, wherein the first-order davinin equivalent circuit model in the fourth embodiment includes ohmic internal resistance R0Polarization resistance R1And a polarization capacitor C1And an open circuit equivalent voltage source UOC；
Ohmic internal resistance R0One end of the positive electrode is connected with the positive electrode of the charging power supply, and the ohmic internal resistance R0The other end of the capacitor is simultaneously connected with a polarization capacitor C1And a polarization resistance R1One end of (a); polarization capacitance C1The other end of the same is connected with the polarization resistor R1And the other end of the open circuit equivalent voltage source UOCOpen circuit equivalent voltage source UOCThe negative electrode of the charging power supply is connected with the negative electrode of the charging power supply.
The fifth concrete implementation mode: in this embodiment, the heating control method of the simultaneous internal and external heating device of the power battery pack according to the fourth embodiment is further described, wherein the formula of the first-order davinin equivalent circuit model is as follows:
wherein R is0Is ohmic internal resistance, R1For polarizing internal resistance, C1To polarize the capacitance, UOCFor the open circuit voltage of the lithium ion battery, U is the terminal voltage of the lithium ion battery, and s is the complex frequency.
The sixth specific implementation mode: in this embodiment, the heating control method of the simultaneous internal and external heating device of the power battery pack according to the fifth embodiment is further described, wherein the fourth step is to set internal parameters of the sub-battery pack: ohmic internal resistance R0Internal resistance to polarization R1And a polarization capacitor C1The specific method for identification comprises the following steps:
step four, one, order
Formulating the equivalent circuit model into a differential form, wherein x (k) is a physical quantity value obtained by sampling at the kth time, and x (k-1) is a physical quantity value obtained by sampling at the kth-1 time, and the physical quantity is Uoc (k), U (k) or I (k);
UOC(K)-U(K)＝k1[UOC(K-1)-U(K-1)]+k2I(K)-k3I(K-1) (2)
wherein the content of the first and second substances,
uoc (k) is the open circuit voltage of the power battery sampled k times, U (k) is the terminal voltage of the power battery sampled k times, I (K) is the current of the power battery sampled k times, k-1 represents the k-1 sampling, T is the sampling interval, the time between two samplings, UOC(k-1) is k-1 sampling runsThe open-circuit voltage of the power battery, U (k-1) is the terminal voltage of the power battery sampled k-1 times, and I (k-1) is the current of the power battery sampled k-1 times;
step four and two, identifying the parameter k in the differential equation by a recursive least square method1,k1,k3(ii) a The parameters in the equivalent circuit model are:
the seventh embodiment: in this embodiment, the method for simultaneously heating the inside and the outside of the power battery pack according to the sixth embodiment is further described, wherein the functions of the total internal impedance and the alternating excitation frequency of the two groups of power batteries obtained in the fifth step are as follows:
wherein ω is 2 pi f; f is the alternating excitation heating frequency of the lithium ion power battery, j is an imaginary number unit, R1(f) As a function of the polarization internal resistance of the cell with the alternating excitation heating frequency, C1(f) Is a polarization capacitance C of the battery1As a function of the heating frequency of the alternating excitation, wherein C1(f) And R1(f) And fitting through an impedance spectrum to obtain the impedance spectrum.
The specific implementation mode is eight: in this embodiment, the method for simultaneously heating the inside and the outside of the power battery pack according to the seventh embodiment is further described, and the specific method for calculating and obtaining the optimal heating frequency of the lithium ion battery in the current temperature environment in the fifth step is as follows:
using formula of heat production power
Obtaining the heat generation power Q and the alternating excitation frequency function, wherein Re (Z (f)) is the real part of complex number Z (f), and Delta U is the terminal voltage U and the open circuitPress UOCA difference of (d); the heat production power formula is developed to obtain:
and solving a first derivative and a second derivative of the heat generation power expansion equation to obtain a maximum value of the heat generation power, wherein the alternating excitation frequency corresponding to the maximum value of the heat generation power is the alternating excitation heating frequency of the power battery.
The specific implementation method nine: in this embodiment, the method for simultaneously heating the inside and the outside of the power battery pack according to the third embodiment is further described, wherein the intermediate threshold soc is set in the first stepsetThe range of (A): soc of 0.1 & ltset＜0.15。
The detailed implementation mode is ten: in this embodiment, the method for controlling charging/heating of the power battery of the electric vehicle according to the third embodiment is further explained, and the temperature threshold T is set according to the second embodimentsetIn the range of 5 < Tset＜10℃。
The concrete implementation mode eleven: in this embodiment, the method for controlling charging and heating of the power battery of the electric vehicle according to the third embodiment is further described, and the heating time t1 in the seventh step is in a range from 20s to 40 s.
The invention adopts two modes of internal heating and external heating to heat the power battery pack simultaneously, thereby realizing the effect of quick preheating. The heating film is used for external heating, and alternating excitation charging and discharging among batteries in the battery pack are realized through the bidirectional DC/DC converter, so that the lithium ion battery pack is internally heated. Meanwhile, the control strategy is adopted, so that the internal heating can realize the adjustment of the uneven distribution of the temperature caused by the external heating. And the control strategy is adopted to avoid the possibility of over-discharge caused by self-heating of the battery when the battery is low.
Although the embodiments of the present invention have been described above, the above descriptions are only for the convenience of understanding the present invention, and are not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. A control method for heating the inside and the outside of a power battery pack simultaneously is realized based on a device for heating the inside and the outside of the power battery pack simultaneously, and is characterized in that the device is applied to the power battery pack (2) comprising 2N sub-battery packs and comprises a heating film (1), 2N switching circuits (3), N temperature sensors (4), a bidirectional DC/DC converter (5), a sampling circuit (6) and a control unit (7);
the heating film (1) is arranged on the outer side of the power battery pack and used for externally heating the power battery pack; the heating power control signal input end of the heating film (1) is connected with the external heating control signal output end of the control unit (7);
two sub-battery packs which are arranged symmetrically with an axis in the internal space of the power battery pack form a self-heating unit, a temperature sensor (4) is arranged in each self-heating unit, the temperature sensors (4) are used for collecting surface temperature signals of any one sub-battery pack in the self-heating unit, and the temperature signal output ends of the N temperature sensors (4) are all connected with the temperature signal input end of the control unit (7);
the charge and discharge signal input and output ends of one group of sub-battery packs in each self-heating unit are connected with the signal input and output ends on one side of the bidirectional DC/DC converter (5) through a switch circuit (3), and the charge and discharge signal input and output ends of the other group of sub-battery packs are connected with the signal input and output ends on the other side of the bidirectional DC/DC converter (5) through a switch circuit (3); the control signal input ends of the 2N switching circuits (3) are connected with the switch control signal output end of the control unit (7);
the sampling circuit (6) is respectively connected with one group of sub battery packs in the N self-heating units through the N switch circuits (3) and is used for collecting the current, the terminal voltage and the charge state of the connected sub battery packs; the signal output end of the sampling circuit (6) is connected with the sampling signal input end of the control unit (7);
the method for controlling the simultaneous heating of the inside and the outside of the power battery pack comprises the following specific steps:
step one, putting a certain group of sub battery packs into a sampling loop, collecting the charge state soc of the sub battery packs, and judging whether the charge state soc is larger than a set charge state threshold socsetIf so, executing the step two, otherwise, keeping the battery pack in a low-power state, and repeatedly executing the step one, soc, in order to prevent the battery from over-discharging and not carrying out the self-heating processsetIs a positive number;
step two, collecting the temperature T in the N self-heating units, and judging the lowest temperature value T in the N self-heating unitsminWhether or not less than a temperature threshold TsetIf yes, executing the third step, otherwise, returning to execute the first step; wherein, TsetIs a positive number;
step three, controlling the heating film (1) to start external heating on the power battery pack (2); while collecting the temperature as the lowest value TminThe terminal voltage U and the battery current I of one sub-battery pack in the self-heating unit;
step four, establishing the temperature as the minimum value TminThe first-order Davining equivalent circuit model of the sub-battery pack utilizes the terminal voltage U and the battery current I of the sub-battery pack acquired in the third step to perform the following operation on the internal parameters of the sub-battery pack: ohmic internal resistance R0Internal resistance to polarization R1And a polarization capacitor C1Performing identification;
step five, according to the ohmic internal resistance R identified in the step four0Internal resistance to polarization R1And a polarization capacitor C1Identifying to obtain total internal impedance and alternating excitation frequency functions of the two groups of power batteries;
the functions of the total internal impedance and the alternating excitation frequency of the two groups of power batteries are as follows:
wherein ω is 2 pi f; f is the alternating excitation heating frequency of the lithium ion power batteryJ is an imaginary unit, R1(f) As a function of the polarization internal resistance of the cell with the alternating excitation heating frequency, C1(f) Is a polarization capacitance C of the battery1As a function of the heating frequency of the alternating excitation, wherein C1(f) And R1(f) Fitting through an impedance spectrum to obtain;
step six, obtaining the minimum value T of the temperature by using the total impedance and frequency function and the heat generation rate formula in the battery obtained in the step fiveminThe optimum excitation heating frequency of the sub-battery pack of (1);
step seven, setting the temperature as the minimum value TminThe optimum heating excitation frequency of the sub-battery is used as the optimum alternating switching frequency of the bidirectional DC/DC converter to make the temperature be the minimum value TminTwo groups of sub battery packs in the self-heating unit to which the sub battery packs belong alternately discharge to realize the minimum value T of the contrastminAfter time t1, the method returns to the step one, wherein t1 is a positive number.
2. The method for controlling simultaneous heating of the inside and the outside of a power battery pack according to claim 1, wherein the sampling circuit (6) comprises a current sampling circuit for collecting the current of the connected sub-battery pack, a voltage sampling circuit for the terminal voltage of the connected sub-battery pack, and a state-of-charge sampling circuit for collecting the state-of-charge of the connected sub-battery pack.
3. The method according to claim 1, wherein the first-order thevenin equivalent circuit model of step four comprises ohmic internal resistance R0Polarization resistance R1And a polarization capacitor C1And an open circuit equivalent voltage source UOC；
Ohmic internal resistance R0One end of the positive electrode is connected with the positive electrode of the charging power supply, and the ohmic internal resistance R0The other end of the capacitor is simultaneously connected with a polarization capacitor C1And a polarization resistance R1One end of (a); polarization capacitance C1The other end of the same is connected with the polarization resistor R1Another end of (1) and an openingEquivalent voltage source UOCOpen circuit equivalent voltage source UOCThe negative electrode of the charging power supply is connected with the negative electrode of the charging power supply.
4. The method of claim 3, wherein the first order thevenin equivalent circuit model is formulated as:
wherein R is0Is ohmic internal resistance, R1For polarizing internal resistance, C1To polarize the capacitance, UOCFor the open circuit voltage of the lithium ion battery, U is the terminal voltage of the lithium ion battery, and s is the complex frequency.
5. The method of claim 4, wherein the internal parameters of the sub-battery in step four: ohmic internal resistance R0Internal resistance to polarization R1And a polarization capacitor C1The specific method for identification comprises the following steps:
step four, formulating the first-order Davining equivalent circuit model into a differential form to obtain:
UOC(k)-U(k)＝k1[UOC(k-1)-U(k-1)]+k2I(k)-k3I(k-1) (2)
wherein the content of the first and second substances,
uoc (k) is the open circuit voltage of the power battery sampled k times, U (k) is the terminal voltage of the power battery sampled k times, I (k) is the current of the power battery sampled k times, k-1 represents the k-1 sampling, T is the sampling interval, the time between two samplings, UOC(k-1) is the open-circuit voltage of the power battery sampled k-1 times, U (k-1) is the terminal voltage of the power battery sampled k-1 times, and I (k-1) is the current of the power battery sampled k-1 times;
step four and two, identifying the parameter k in the differential equation by a recursive least square method1,k1,k3(ii) a The parameters in the equivalent circuit model are:
6. the method according to claim 5, wherein the specific method for calculating and obtaining the optimal heating frequency of the lithium ion battery in the current temperature environment in the sixth step is as follows:
using formula of heat production power
Obtaining heat generation power Q and an alternating excitation frequency function, wherein Re (Z (f)) is a real part of complex number Z (f), and delta U is terminal voltage U and open-circuit voltage UOCA difference of (d); the heat production power formula is developed to obtain:
and solving a first derivative and a second derivative of the heat generation power expansion equation to obtain a maximum value of the heat generation power, wherein the alternating excitation frequency corresponding to the maximum value of the heat generation power is the alternating excitation heating frequency of the power battery.
7. Method according to claim 1, characterised in that the temperature threshold T of step two issetIn the range of 5 < Tset＜10℃。
8. The method as claimed in claim 1, wherein the heating time t1 in step seven is in the range of 20s to 40 s.
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| CN111355003B (en) * | 2020-03-12 | 2021-08-10 | 奇瑞新能源汽车股份有限公司 | Heating method of power battery heating device |
| CN111864136B (en) * | 2020-07-08 | 2022-06-17 | 中北大学 | Composite storage battery pack device with low-temperature starting and temperature adjusting functions and using method |
| CN111934038B (en) * | 2020-07-29 | 2021-08-24 | 厦门金龙旅行车有限公司 | Battery heating device and heating method |
| CN112240984B (en) * | 2020-09-22 | 2021-10-26 | 清华大学 | Lithium ion battery lithium analysis detection method and detection device thereof |
| CN112599889B (en) * | 2020-12-14 | 2022-05-06 | 天津市捷威动力工业有限公司 | Self-heating control method of lithium ion battery |
| CN112601297B (en) * | 2020-12-15 | 2023-06-16 | 北京理工大学 | Composite alternating-current heating device for power battery |
| CN113206325B (en) * | 2021-04-30 | 2022-05-03 | 重庆长安新能源汽车科技有限公司 | Power battery internal and external combined heating method |
| CN117317456B (en) * | 2023-11-27 | 2024-02-06 | 江苏欧力特能源科技有限公司 | Low-temperature cold starting system of household energy storage lithium battery |
| CN117728075B (en) * | 2023-12-19 | 2024-06-28 | 佛山科学技术学院 | Self-heating method and heating device for lithium ion battery in low-temperature environment |
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