A battery heating control method, system and selection method

Abstract

The present invention provides a battery heating control method, system and selection method, which can realize the charge and discharge state conversion when the current in the capacitor charging and discharging circuit is 0 or the current discharge is changed, that is, when the current in the power supply circuit of the battery is 0 or the current direction is changed, by obtaining the charging time of the capacitor in the charge pump, wherein the charging time is determined according to the oscillation period of the capacitor charging circuit; obtaining the discharge time of the capacitor in the charge pump, wherein the discharge time is determined according to the oscillation period of the capacitor discharging circuit; obtaining the dead time of the switch device in the charge pump; and determining the switching cycle of the switch device in the charge pump based on the charging time, the discharge time and the dead time. The current in the capacitor charging and discharging circuit is 0 or the current discharge is changed, that is, when the current in the power supply circuit of the battery is 0 or the current direction is changed. The peak voltage generated by the current in the circuit during switching is avoided, and the safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries, and in particular to a battery heating control method, system and selection method. Background Art

[0002] As the core component of the power system of electric vehicles, the working state of the power battery has a crucial impact on the reliability and safety of the vehicle. The characteristics of the power battery are significantly affected by the ambient temperature, especially in low temperature environments, its performance will decline significantly. Therefore, before starting the car at low temperature, the power battery needs to be preheated.

[0003] The charge pump self-heating technology solution in the prior art can realize battery self-heating by using relatively small on-board electronic components, without the need for external source equipment, and can be self-heated anytime and anywhere as needed, which is convenient for users. However, when the charge and discharge states in the charge pump are switched, there may be current in the circuit, which will generate extremely high voltage spikes at both ends of the power battery and the charge pump, which can easily cause damage to the power battery and switching devices, thereby affecting the safe and reliable operation of the system. Summary of the invention

[0004] In order to solve the problem of voltage spikes in the prior art, the present invention provides a battery heating control method, system and selection method, which has the characteristics of not easily generating voltage spikes in the charge pump.

[0005] A battery heating control method provided according to a specific embodiment of the present invention includes:

[0006] Obtaining a charging time of a capacitor in a charge pump, wherein the charging time is determined according to an oscillation period of a capacitor charging circuit, and when the charging time of the capacitor in the charge pump reaches the charging time, the current is zero or the current direction is different from the current direction at the charging start time, and the oscillation period of the capacitor charging circuit is determined by a capacitance value, an equivalent inductance value, and an equivalent resistance value in the capacitor charging circuit;

[0007] Obtaining a discharge time of the capacitor in the charge pump, wherein the discharge time is determined according to an oscillation period of a capacitor discharge loop, and when the discharge time of the capacitor in the charge pump reaches the discharge time, the current is zero or the current direction is different from the current direction at the discharge start time, and the oscillation period of the capacitor discharge loop is determined by the capacitance value, equivalent inductance value, and equivalent resistance value in the capacitor discharge loop;

[0008] Obtaining the dead time of the switch device in the charge pump;

[0009] The switching cycle of the switching device in the charge pump is determined based on the charging time, the discharging time and the dead time to achieve heating of the power battery.

[0010] Furthermore, the charging time is an odd number of times of a half period of the oscillation period of the capacitor charging circuit, and the discharging time is an odd number of times of a half period of the oscillation period of the capacitor discharging circuit.

[0011] Furthermore, the process of determining the charging time and the discharging time includes:

[0012] Injecting a voltage signal of a first preset frequency into a capacitor charging loop to determine a half period of an oscillation period of the capacitor charging loop;

[0013] Injecting a voltage signal of a second preset frequency into the capacitor discharge loop to determine a half period of the oscillation period of the capacitor discharge loop;

[0014] The frequency of the battery voltage signal injected into the capacitor charging circuit is adjusted according to the half period of the oscillation period of the capacitor charging circuit, and the frequency of the battery voltage signal injected into the capacitor discharging circuit is adjusted according to the half period of the oscillation period of the capacitor discharging circuit; wherein the test charging time of the capacitor charging circuit and the test discharging time of the capacitor discharging circuit are continuously reduced;

[0015] When the effective current values ​​of the capacitor charging circuit and the capacitor discharging circuit match the battery heating rate requirement, the test charging time of the corresponding capacitor charging circuit is used as the charging time, and the test discharge time of the corresponding capacitor discharging circuit is used as the discharge time.

[0016] Further, the adjusting the frequency of the battery voltage signal injected into the capacitor charging loop according to a half period of the capacitor charging loop oscillation period, and adjusting the frequency of the battery voltage signal injected into the capacitor discharging loop according to a half period of the capacitor discharging loop oscillation period, comprises:

[0017] Adjust the frequency of the battery voltage signal injected into the capacitor charging loop according to the half-period and multiple adjustment strategy of the capacitor charging loop oscillation period;

[0018] Adjust the frequency of the battery voltage signal injected into the capacitor discharge loop according to the half period of the capacitor discharge loop oscillation period and the multiple adjustment strategy;

[0019] The multiple adjustment strategy is that the difference in the test charging time of the capacitor charging circuit after two adjustments is a preset even number of times of half a period of the capacitor charging circuit oscillation period; the difference in the test discharge time of the capacitor discharging circuit after two adjustments is a preset even number of times of half a period of the capacitor discharging circuit oscillation period; wherein, the initial value of the test charging time of the capacitor charging circuit is a preset odd number of times of half a period of the capacitor charging circuit oscillation period, the initial value of the test discharge time of the capacitor discharging circuit is a preset odd number of times of half a period of the capacitor discharging circuit oscillation period, and the test charging time of the capacitor charging circuit and the test discharge time of the capacitor discharging circuit are continuously reduced.

[0020] A battery heating control system provided according to a specific embodiment of the present invention includes: a charge pump connected to both ends of a battery, and a controller connected to a switch device in the charge pump, wherein the controller is used to execute each step of the battery heating control method as described above.

[0021] Furthermore, the battery heating control system further includes: an absorption circuit connected in parallel with the switching device in the charge pump.

[0022] Furthermore, the absorption circuit includes: a first resistor and a first capacitor connected in series.

[0023] Furthermore, the absorption circuit also includes: a second resistor, a second capacitor and a diode. The second resistor and the second capacitor are connected in parallel and then in series with the diode. The conduction direction of the diode is used to conduct the current of the corresponding switching device along the initial current direction.

[0024] Furthermore, the battery heating control system further includes: an adjustable inductor connected to the battery bus.

[0025] A method for selecting a battery heating control system according to a specific embodiment of the present invention includes:

[0026] Obtaining a preset switching cycle of the charge pump;

[0027] Obtaining the dead time of the switch device in the charge pump;

[0028] Determine the sum of an oscillation period of a capacitor charging loop and an oscillation period of a capacitor discharging loop in the charge pump based on the preset switching period and the dead time;

[0029] Determine a first expected oscillation period of the capacitor charging circuit oscillation period and a second expected oscillation period of the capacitor discharging circuit oscillation period according to the sum value and the relationship between the capacitor charging circuit oscillation period and the capacitor discharging circuit oscillation period;

[0030] Determining the capacitance and parasitic inductance of the capacitor in the charge pump according to the first expected oscillation period, the second preset oscillation period, the battery voltage, and the effective value of the current required by the battery heating rate;

[0031] The parasitic resistance value in the charge pump is determined according to the battery internal resistance and the line resistance parameters.

[0032] The effective effects of the present invention are as follows: by obtaining the charging time of the capacitor in the charge pump, wherein the charging time is determined according to the oscillation period of the capacitor charging circuit, and when the charging time of the capacitor in the charge pump reaches the charging time, the current is zero or the current direction is different from the current direction at the charging start time, and the capacitor charging circuit oscillation period is determined by the capacitance value, equivalent inductance value and equivalent resistance value in the capacitor charging circuit; obtaining the discharge time of the capacitor in the charge pump, wherein the discharge time is determined according to the oscillation period of the capacitor discharge circuit, and when the discharge time of the capacitor in the charge pump reaches the discharge time, the current is zero or the current direction is different from the current direction at the discharge start time, and the capacitor discharge circuit oscillation period is determined by the capacitance value, equivalent inductance value and equivalent resistance value in the capacitor discharge circuit; obtaining the dead time of the switch device in the charge pump; and then determining the switching cycle of the switch device in the charge pump based on the determined charging time, discharge time and dead time to heat the power battery. After the current in the capacitor charging and discharging circuit is zero or the current direction changes, that is, after the current in the power supply circuit of the battery is zero or the current direction changes, the charging and discharging state conversion is performed. This effectively avoids the peak voltage generated on both ends of the battery and on the device by the current in the loop during switching, thereby improving the reliability and safety of the system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1 is a flow chart of a battery heating control method provided according to an exemplary embodiment;

[0035] Figure 2 is a flow chart of a process for determining a charging duration and a discharging duration according to an exemplary embodiment;

[0036] Figure 3 is a flow chart for selecting circuit parameters in a charge pump according to an exemplary embodiment;

[0037] Figure 4is an equivalent circuit diagram of a capacitor in a charging state according to an exemplary embodiment;

[0038] Figure 5 is an equivalent circuit diagram of a capacitor in a discharged state according to an exemplary embodiment;

[0039] Figure 6 is a structural diagram of an absorption circuit provided according to an exemplary embodiment;

[0040] Figure 7 is another structural diagram of an absorption circuit provided according to an exemplary embodiment;

[0041] Figure 8 is an existing system operation waveform diagram provided according to an exemplary embodiment;

[0042] Fig. 9 is a system operation waveform diagram after applying a battery heating control method provided according to an exemplary embodiment;

[0043] Fig.10 is a structural diagram of a battery heating control system provided according to an exemplary embodiment. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0045] Reference Figure 1 As shown, an embodiment of the present invention provides a battery heating control method, which may include:

[0046] 101. Obtain the charging time of the capacitor in the charge pump.

[0047] The charging time is determined according to the oscillation period of the capacitor charging circuit, and when the charging time of the capacitor in the charge pump reaches the charging time, the current is zero or the current direction is different from the current direction of the charging start time, and the capacitor charging circuit oscillation period is determined by the capacitance value, equivalent inductance value and equivalent resistance value in the capacitor charging circuit. The capacitor charging circuit here refers to the circuit when each capacitor in the charge pump is in parallel and the power battery charges each capacitor. The capacitance value in the capacitor charging circuit is determined by the capacitance value of the capacitor in the capacitor charging circuit, and the equivalent inductance value and equivalent resistance value in the capacitor charging circuit are determined by the parasitic parameters of the capacitor in the circuit, the parasitic parameters of the circuit itself, the internal resistance of the battery, and the conduction internal resistance of the switching device. The parasitic parameters of the capacitor include parasitic resistance and parasitic inductance, and the parasitic parameters of the circuit itself include parasitic inductance. In some embodiments, an external inductor is also connected in series on the battery bus, and the equivalent inductance value also includes the inductance value of the external inductor. It is understandable that in other embodiments, there may be no external inductor.

[0048] 102. Obtain the discharge time of the capacitor in the charge pump.

[0049] The discharge time is determined according to the oscillation period of the capacitor discharge circuit, and when the discharge time of the capacitor in the charge pump reaches the discharge time, the current is zero or the current direction is different from the current direction of the discharge start time, and the capacitor discharge circuit oscillation period is determined by the capacitance value, equivalent inductance value and equivalent resistance value in the capacitor discharge circuit. The capacitor discharge circuit here refers to the circuit when each capacitor in the charge pump is in a series state and each capacitor after series connection charges the power battery. The capacitance value in the capacitor discharge circuit is determined by the capacitance value of the capacitor in the capacitor discharge circuit, and the equivalent inductance value and equivalent resistance value in the capacitor discharge circuit are determined by the parasitic parameters of the capacitor in the circuit, the parasitic parameters of the circuit itself, the internal resistance of the battery, and the conduction internal resistance of the switching device. The parasitic parameters of the capacitor include parasitic resistance and parasitic inductance, and the parasitic parameters of the circuit itself include parasitic inductance. In some embodiments, an external inductor is also connected in series on the battery bus, and the equivalent inductance value also includes the inductance value of the external inductor. It can be understood that in other embodiments, there can be no external inductor.

[0050] Among them, the capacitor charging circuit oscillation period and the capacitor discharging circuit oscillation period can be obtained by calculation, such as calculating the parasitic parameters in the charge pump in the capacitor charging state equivalently to the circuit connected to the power battery, and obtaining the oscillation period of the charging resonant circuit (that is, the capacitor charging circuit); calculating the parasitic parameters in the charge pump in the capacitor discharging state equivalently to the circuit connected to the power battery, and obtaining the oscillation period of the discharge resonant circuit (that is, the capacitor discharging circuit). In some other embodiments, the capacitor charging circuit oscillation period and the capacitor discharging circuit oscillation period can also be obtained by actual testing. In addition, the parasitic parameters in the charge pump can be obtained by calculation or by testing.

[0051] After the resistance, capacitance and inductance parameters in the circuit are equivalent to the battery power supply circuit, the circuit in the capacitor charging state and the circuit in the capacitor discharging state can be regarded as an RLC series resonant circuit, and its circuit characteristics are in the form of oscillation attenuation, that is, the direction of the current in the circuit will be repeatedly switched during the oscillation process, and the switch is turned off when the current oscillates to the zero point or oscillates to the opposite direction of the initial current, so that the voltage spike caused by the instantaneous mutation of the current can be avoided. And when performing equivalent calculations, an external inductor of preset specifications can be connected to the circuit connected to the battery. The addition of external inductance can still regard the entire circuit as an RLC series resonant circuit when the equivalent inductance in the charge pump is weak, so that the corresponding period can be obtained more easily.

[0052] 103. Obtain the dead time of the switching device in the charge pump.

[0053] The switching of the switch state needs to take into account the dead time of the switch, that is, the current in the circuit needs to become zero within the dead time.

[0054] 104. Based on the above charging time, discharging time and dead time, a switching cycle of a switching device in a charge pump is determined to achieve heating of the power battery.

[0055] Specifically, in the capacitor series mode, the initial direction of the current in the loop is opposite to that in the capacitor parallel mode. The power battery is charged by two capacitors in series. The basic working principle in the capacitor series mode is the same as that in the capacitor parallel mode. The switch state switching must also be completed at the zero point of the half-cycle of the loop current oscillation or within a half-cycle to one cycle of the oscillation. Then, the sum of the half-cycle of the circuit oscillation in the capacitor charging state and the half-cycle of the circuit oscillation in the capacitor discharging state and the two dead time periods is used as the switching cycle, so that the current in the capacitor charging circuit and the capacitor discharging circuit is 0 or the current direction changes, that is, the current in the power supply circuit of the power battery is 0 or the current direction changes. The charge and discharge state conversion can be realized. This effectively avoids the spike voltage generated by the current in the circuit at both ends of the battery and the switch device during switching, thereby improving the reliability and safety of the system operation.

[0056] Reference Figure 8 and Fig. 9 The corresponding system response waveform is shown in Figure 2, where Figure 8 It is the existing system working waveform diagram; Fig. 9 It is a system working waveform diagram after applying the battery heating control method of the present invention, and the vertical axes are, from bottom to top, the current value I in the circuit, the equivalent voltage value V, and the corresponding voltage values ​​Vg2 and Vg1 in the circuit after the switch is switched, wherein Vg1 is the voltage value in the capacitor charging circuit, and Vg2 is the voltage value in the capacitor discharging circuit. It can be seen from the comparison effect that the switching cycle determined by the application of the battery heating control method can effectively suppress the occurrence of voltage spikes in the charge pump circuit, and has better reliability and safety.

[0057] As a feasible implementation method of the above embodiment, refer to Figure 4 and Figure 5 As shown, Figure 4 is the equivalent circuit of the capacitor in the charging state, Figure 5 is the equivalent circuit of the capacitor in the discharged state, where Figure 4 The arrow in the figure indicates the direction of the current at the start of charging. Figure 5 The arrow in the figure indicates the direction of the current at the start of discharge.

[0058] in, Figure 4 and Figure 5 With a two-stage charge pump, S1, S2, and S3 are switch devices, C1 and C2 are charge pump capacitors, and Vbat is a power battery. When S1 and S3 are turned on and S2 is turned off, the two capacitors are connected in parallel, and the power battery V1at charges the capacitors C1 and C2; when S1 and S3 are turned off and S2 is turned on, the two capacitors C1 and C2 are connected in series, and the capacitors C1 and C2 charge the power battery Vbat. The two states are repeatedly cycled, and positive and negative pulse currents are generated on the power battery Vbat to heat the power battery Vbat. In the existing control method, the duration of the two control methods is usually selected to be the same, and a certain dead time is separated in between. When the switch control frequency is high, since each charge and discharge time is short, the capacitor cannot reach a steady state when switching between charge and discharge states, that is, there is still a charge / discharge current in the circuit. At this time, after the switch is turned off and the dead time is entered, the current in the circuit will become zero. If the circuit is in an ideal state, that is, there are only capacitors and resistors but no inductive components, then the instantaneous mutation of the current will not produce other adverse consequences. However, there is parasitic inductance in the actual circuit. At this time, the instantaneous mutation of current will generate a voltage spike on the loop inductance, threatening the safe operation of the switching device.

[0059] like Figure 4 As shown in the figure, in the capacitor parallel mode, the equivalent series inductance of the capacitor is recorded as L cap , the line parasitic inductance is recorded as Lwire , the external inductance is denoted as L ex , the internal resistance of the battery is recorded as R bat , the equivalent series resistance of the capacitor is denoted as R cap , the on-resistance of the switch device is denoted as R S , the line parasitic inductance is recorded as R wire The capacitance value in the parallel mode is C eq =C 1 +C 2 , the equivalent series inductance L of the capacitor cap The parasitic inductance of the circuit and the line are equivalent to the battery bus, and the equivalent inductance of the entire circuit (i.e. the equivalent inductance value) is L eq =L cap +L wire +L ex =L, if there is no external inductance, then L is ignored ex The equivalent series resistance R of the battery internal resistance and capacitor cap , the on-state resistance of the switching device R S , the equivalent series resistance of the capacitor is denoted as R cap 、Battery internal resistance R bat Combined and recorded as the equivalent internal resistance of the circuit (i.e. equivalent resistance value) R eq =R bat +R cap +R S +R wire =R, then the entire circuit can be regarded as an RLC series resonant circuit, and its circuit voltage equation can be written as:

[0060]

[0061] Among them, V bat is the voltage of the power battery, v C is the voltage of the capacitor, is the voltage of the equivalent inductance of the loop, Ri L is the voltage of the equivalent internal resistance of the loop, and then the yields (first-order derivative) processing is performed.

[0062] The general solution to the above homogeneous differential equation can be written as:

[0063]

[0064] in,

[0065]

[0066]

[0067] From the above formula, we can see that the loop current is in the form of oscillation attenuation. α is the attenuation coefficient, which represents the attenuation rate of the response.d is the circuit's decaying oscillation angular frequency, characterizing the oscillation rate of the response, A is the current amplitude, is the initial phase of the current. During the oscillation process, the direction of the circuit current will switch repeatedly. If the switch can be turned off when the current oscillates to the zero point or oscillates to the opposite direction of the initial current, the voltage spike caused by the instantaneous mutation of the current can be avoided. Specifically, it is divided into the following two cases:

[0068] 1. Turn off the switch at the current zero crossing point: According to the characteristics of oscillation attenuation, the first zero crossing point of the current occurs at the half cycle of the oscillation, that is, At this time, turning off switches S1 and S3 can reduce the voltage spike to the minimum. Then it enters the dead time when S1, S2, and S3 are all closed. During the dead time, the current in the circuit remains zero. After the dead time, S2 is turned on, and no spike voltage is generated inside the circuit.

[0069] 2. Turn off the switch after the current direction changes: If the turn-off time is after the first zero crossing point and before the second zero crossing point, that is, When the current direction in the loop is opposite to the initial current direction, S1 and S3 are turned off at this time. After entering the dead time, the current in the loop will be conducted through the parasitic diode of the MOSFET (field effect transistor). After the dead time ends, S2 is turned on and the current will continue to flow in this direction, so no spike voltage will be generated in the loop.

[0070] Figure 5 The initial direction of the current in the loop in the series mode shown is opposite to that in the parallel mode. The two capacitors are connected in series to charge the power battery. The basic working principle in the series mode is the same as that in the parallel mode. The switch state switching must also be completed at the zero point of the half-cycle of the loop current oscillation or within the oscillation half cycle to one cycle. The above calculation formula is still valid. The difference is that the equivalent parameters of the loop are different. The calculation methods of loop parasitic inductance and resistance will also produce certain differences, but the loop equivalent capacitance is the dominant factor in determining the loop oscillation frequency.

[0071] Since the oscillation form, oscillation frequency, attenuation coefficient, etc. of the RLC oscillation circuit are inherent parameters of the circuit, they will not change with the excitation form and excitation frequency after the circuit topology and component parameters are determined. Therefore, if the circuit parameters have been determined, the switching period can be determined according to the following principles:

[0072] Parallel mode working time:

[0073]

[0074] Among them, t p is the half period of the capacitor charging loop oscillation period, ω dpis the decaying oscillation angular frequency of the parallel mode;

[0075] Series mode working time:

[0076]

[0077] Among them, t s Half period of the capacitor discharge loop oscillation period, ωd s is the decaying oscillation angular frequency of the series mode;

[0078] Dead time t d It is determined based on the rise and fall time and delay time of the switching device;

[0079] Then the switching period T = t p +t s +2t d .

[0080] It can be understood that the above embodiments are combined with the description of the most basic charge pump circuit composed of two capacitors and three switches. Other numbers of capacitors and switches can also be used to form charge pumps of different orders of magnitude to determine the switching cycle. Those skilled in the art can apply the above principles of the present invention to charge pumps of different orders of magnitude, and the present invention is not limited here.

[0081] As a specific application of the above embodiment, the circuit parameters have been determined, the capacitance of C1 and C2 is 1mF, the equivalent inductance of the loop is 10uH, the equivalent resistance of the loop is 20mΩ, and the equivalent capacitance of the loop in parallel is 2mF, then the loop differential equation is Can be written as:

[0082]

[0083] The characteristic equation of the loop is:

[0084]

[0085] Substituting the circuit parameters into the above formula, we get:

[0086] p 2 +2000p+5×10 7 =0

[0087] The characteristic equation gives the discriminant:

[0088] Δ=2000 2 -4×5×10 7 <0

[0089] The characteristic root is a conjugate complex root, and its response form is oscillation attenuation. According to the same method, when the capacitors are connected in series, the equivalent capacitance of the circuit is 0.5mF, and the response form is also oscillation attenuation. The oscillation angular frequency when connected in parallel and in series is calculated as: ω dp =7000rad / s,ω ds =14107rad / s, the working time in parallel and series mode is t p =4.488×10 -4 s, t s =2.227×10 -4 s, set the corresponding dead time of the switching device to t d =1×10 -5 s, then the switching period T=6.915×10 -4 S, the corresponding frequency f = 1.446kHz. The switching cycle determined in this way can significantly reduce the voltage spike caused by switching the switch state, thereby avoiding the impact on the power battery and the switch device.

[0090] In practical applications, since the parasitic parameters in the charge pump, such as the parasitic parameters of the capacitor and the parasitic parameters of the circuit itself, are difficult to measure accurately, when performing a basic heating test on the power battery, the half-period of the oscillation period of the capacitor charging circuit, the half-period of the oscillation period of the capacitor discharging circuit, and the charging time and discharge time of the capacitor in the charge pump can be obtained by calibration test. For example, when performing a heating test on a battery with unknown parameters, the switching frequency can be determined by reference. Figure 2 The following steps may be included:

[0091] 201. Inject a voltage signal of a first preset frequency into a capacitor charging loop to determine a half period of an oscillation period of the capacitor charging loop.

[0092] Specifically, a voltage signal of a first preset frequency is injected into the capacitor charging loop, the current waveform result is observed, the time duration and the number of half cycles for the current waveform to decay to 0 are recorded, and the half cycle of the capacitor charging loop oscillation cycle is calculated.

[0093] 202. Inject a voltage signal of a second preset frequency into the capacitor discharge loop to determine a half period of an oscillation period of the capacitor discharge loop.

[0094] Specifically, a voltage signal of a first preset frequency is injected into the capacitor discharge loop, the current waveform result is observed, the duration and number of half-cycles of the current waveform decaying to 0 are recorded, and the half-cycle of the capacitor discharge loop oscillation period is calculated. The voltage signal used in step 201 and step 202 may be equal to the battery voltage signal, or may be close to or less than the battery voltage signal. In order to simulate the heating effect on the power battery, the battery voltage signal is selected in the subsequent steps.

[0095] 203. Adjust the frequency of the battery voltage signal injected into the capacitor charging loop according to a half period of the oscillation period of the capacitor charging loop.

[0096] In this step, the number of half-cycles of the capacitor charging circuit oscillation period corresponding to the test charging duration can be determined according to the number of half-cycles determined in step 201, and then the frequency of the battery voltage signal injected into the capacitor charging circuit can be determined according to the number of half-cycles of the capacitor charging circuit oscillation period. Among them, the relationship between the number of half-cycles of the capacitor charging circuit oscillation period and the frequency of the battery voltage signal of the capacitor charging circuit is an existing theory, which will not be repeated here. It should be noted that, in order to ensure safety, measurement accuracy and other reasons, the first preset frequency and the second preset frequency generally selected in step 201 and step 202 are relatively small, and the number of half-cycles of the capacitor charging circuit oscillation period corresponding to the test charging duration is generally determined and adjusted according to experience, calibration or preset strategies in step 203. And in order to ensure safety, the number of half-cycles of the capacitor charging circuit oscillation period corresponding to the test charging duration generally starts from a larger number and continues to decrease.

[0097] 204. Adjust the frequency of the battery voltage signal injected into the capacitor discharge loop according to the half period of the capacitor discharge loop oscillation period; wherein the test charging time of the capacitor charging loop and the test discharging time of the capacitor discharge loop are continuously reduced.

[0098] In this step, the number of half-cycles of the capacitor discharge circuit oscillation period corresponding to the test discharge duration can be determined according to the number of half-cycles determined in step 202, and then the frequency of the battery voltage signal injected into the capacitor charging circuit can be determined according to the number of half-cycles of the capacitor discharge circuit oscillation period. Among them, the relationship between the number of half-cycles of the capacitor discharge circuit oscillation period and the frequency of the battery voltage signal of the capacitor discharge circuit is an existing theory, which will not be repeated here. It should be noted that in step 204, the number of half-cycles of the capacitor discharge circuit oscillation period corresponding to the test charging duration is generally determined and adjusted according to experience, calibration or preset strategies. And in order to ensure safety, the number of half-cycles of the capacitor discharge circuit oscillation period corresponding to the test discharge duration generally starts from a larger number and continues to decrease. In the process of continuously reducing the test charging duration of the capacitor charging circuit and the test discharge duration of the capacitor discharge circuit, the effective value of the current of the capacitor charging circuit and the capacitor discharge circuit is constantly approaching the battery heating rate requirement. 205. When the effective values ​​of the currents of the capacitor charging circuit and the capacitor discharging circuit match the battery heating rate requirements, the test charging time of the corresponding capacitor charging circuit is used as the charging time, and the test discharging time of the corresponding capacitor discharging circuit is used as the discharging time.

[0099] Specifically, the size of the voltage signal can be selected as needed, and can generally be set to the voltage of the power battery. The first preset frequency and the second preset frequency can be the same or different. According to the characteristics of the oscillation circuit, the effective current size can be controlled by adjusting the number of half cycles. Turning off the switch at 2N+1 half cycles can achieve the effect of reducing oscillation, and the larger the N value, the smaller the effective value of the current. When multiple half cycles are selected, formulas (5) and (6) can be modified as follows:

[0100]

[0101]

[0102] Since it is difficult to accurately measure the line parasitic parameters, a lower frequency, such as 100 Hz, is selected at the beginning of the test to test the oscillation period, and the oscillation half-period under the capacitor parallel state is recorded as t p , the oscillation half period of the capacitor in series state is t s .

[0103] Then observe the current waveform results of the low-frequency test, record the number of half cycles when the current waveform decays to 0 (must be an odd number, 2N+1), and calculate as well as The switching frequency for the initial test is calculated from this.

[0104] Continue to adjust the test frequency and find the appropriate current effective value: gradually reduce N and conduct tests. During this process, according to the characteristics of the oscillation circuit, it can be seen that the current effective value will gradually increase. When the current effective value can meet the battery heating rate requirements, record N at this time and use it as the fixed frequency for heating this power battery with this charging and discharging system in the future.

[0105] In some embodiments, adjusting the frequency of the battery voltage signal injected into the capacitor charging loop according to a half period of the capacitor charging loop oscillation cycle, and adjusting the frequency of the battery voltage signal injected into the capacitor discharging loop according to a half period of the capacitor discharging loop oscillation cycle, includes:

[0106] The frequency of the battery voltage signal injected into the capacitor charging loop is adjusted according to the half-cycle and multiple adjustment strategy of the capacitor charging loop oscillation cycle;

[0107] The frequency of the battery voltage signal injected into the capacitor discharge loop is adjusted according to the half-period and multiple adjustment strategy of the capacitor discharge loop oscillation period;

[0108] The multiple adjustment strategy is that the difference in the test charging time of the capacitor charging circuit after two adjustments is a preset even number of times of half a period of the capacitor charging circuit oscillation period; the difference in the test discharge time of the capacitor discharging circuit after two adjustments is a preset even number of times of half a period of the capacitor discharging circuit oscillation period; wherein, the initial value of the test charging time of the capacitor charging circuit is a preset odd number of times of half a period of the capacitor charging circuit oscillation period, the initial value of the test discharge time of the capacitor discharging circuit is a preset odd number of times of half a period of the capacitor discharging circuit oscillation period, and the test charging time of the capacitor charging circuit and the test discharge time of the capacitor discharging circuit are continuously reduced.

[0109] The preset even multiples may be empirical values ​​or calibration values, such as 2 times, 4 times, etc., and the preset odd multiples may also be empirical values ​​or calibration values, such as 15 times, 13 times, etc.

[0110] Based on the same design idea, refer to Fig.10 As shown, an embodiment of the present invention further provides a battery heating control system, comprising: a charge pump connected to both ends of a battery, and a controller connected to a switching device in the charge pump, the controller being used to execute each step of the battery heating control method described in the above embodiment.

[0111] Further, the switching devices in the charge pump are connected in parallel with the absorption circuit.

[0112] The absorption circuit includes: a first resistor and a first capacitor connected in series.

[0113] The absorption circuit also includes: a second resistor, a second capacitor and a diode, the second resistor and the second capacitor are connected in parallel and then in series with the diode, and the conduction direction of the diode is used to conduct the current of the corresponding switch device along the initial current direction. The initial current direction here refers to the current direction corresponding to the switch device at time 0.

[0114] Specifically, refer to Figure 6 The absorption circuit shown may include:

[0115] The filter circuit composed of a resistor and a capacitor connected in series is composed of a resistor and a capacitor connected in series in the dotted box shown in the figure, and limits the voltage rise based on the characteristic that the voltage across the capacitor will not change suddenly.

[0116] Further, refer to Figure 7 As shown, the absorption circuit may further include a second absorption circuit formed by connecting a resistor and a capacitor in parallel and then connecting the resistor and a capacitor in series with a diode.

[0117] The capacitor is used to absorb energy and suppress voltage spikes, while the resistor is used to consume energy and weaken the oscillation process. After the resistor and capacitor are connected in parallel, a diode is connected in series to prevent the energy absorbed by the capacitor from reversely charging the parasitic inductance and generating resonance, thus effectively suppressing voltage oscillation.

[0118] It is understandable that those skilled in the art may also use other circuits with the same functions to implement the function of the absorption circuit in the present invention, and the present invention is not limited thereto.

[0119] In order to make it easier to calculate the parameters of the resonant circuit in the charge pump and determine the oscillation period, in some specific embodiments of the present invention, an adjustable inductor is also provided on the battery bus. Obviously, the adjustable inductor serves as an external inductor.

[0120] Those skilled in the art may set the relevant parameters of the adjustable inductor according to actual application conditions, and the present invention will not elaborate on them here.

[0121] According to the characteristics of the above RLC oscillation circuit, refer to Figure 3 As shown, an embodiment of the present invention further provides a method for selecting a battery heating control system, which can design the parameters of the capacitor and the inductor in the charge pump. The method may include the following steps:

[0122] 301. Obtain a preset switching cycle of a charge pump.

[0123] 302. Obtain the dead time of the switching device in the charge pump.

[0124] 303. Determine a sum of an oscillation period of a capacitor charging loop and an oscillation period of a capacitor discharging loop in a charge pump based on a preset switching cycle and a dead time.

[0125] 304. Determine a first expected oscillation period of the capacitor charging circuit oscillation period and a second expected oscillation period of the capacitor discharging circuit oscillation period according to the above sum value and the relationship between the capacitor charging circuit oscillation period and the capacitor discharging circuit oscillation period.

[0126] Specifically, after obtaining the sum of the capacitor charging loop oscillation period and the capacitor discharging loop oscillation period, since in general, the capacitor charging loop oscillation period is about twice the capacitor discharging loop oscillation period, the first expected oscillation period of the capacitor charging loop oscillation period and the second expected oscillation period of the capacitor discharging loop oscillation period can be preliminarily determined.

[0127] 305. Determine the capacitance and parasitic inductance of the capacitor in the charge pump according to the first expected oscillation period, the second preset oscillation period, the battery voltage, and the effective value of the current required by the battery heating rate.

[0128] 306. Determine the parasitic resistance value in the charge pump according to the battery internal resistance and the circuit resistance parameters.

[0129] Specifically, the equivalent inductance of the loop can be changed by connecting an inductor in series at the battery bus terminal, and the equivalent capacitance of the loop can be changed by changing the capacitance value. It can be seen that the oscillation frequency decreases as R or C increases. When L increases, the oscillation frequency increases. When L increases, the oscillation frequency decreases. When a fixed switching frequency is required, the loop parameters can be adjusted according to the above principles to achieve voltage spike suppression at a certain switching frequency.

[0130] For example: the switching frequency is 20kHz;

[0131] The dead time t is determined by the switch device parameters d =5×10 -6 s, then the sum of the series-parallel mode working time is

[0132] Then the corresponding loop equivalent resistance value is 20mΩ, the loop equivalent inductance value is 1uH, and the capacitance values ​​of C1 and C2 are both 36uF.

[0133] Check the switching period: First calculate the oscillation angular frequency ω dp =117426rad / s,ω ds =235490rad / s, the working time in parallel and series mode is t p =2.675×10 -5 s, t s =1.334×10 -5 s, switching period T = 5.009 × 10 -5 s, switching frequency f=19.96kHz.

[0134] The verification results show that the design parameters basically meet the system switching frequency requirements. If further optimization is still needed, the loop RLC parameters can be further adjusted.

[0135] Among them, from the series-parallel relationship of capacitors, it can be obtained that the oscillation period of the capacitor charging circuit is approximately twice the oscillation period of the capacitor discharging circuit. Therefore, after knowing the sum value, the expected oscillation period of the charging circuit and the discharging circuit can be obtained. Taking the charging and discharging circuit as an example to illustrate the parameter selection method, the internal resistance of the battery and the equivalent resistance of the line are small and can usually be ignored when calculating the oscillation frequency. Therefore, the oscillation period can be written as: The peak current in the line can be written as: Ubat is the battery voltage. When the battery voltage is determined, the parameters of L and C can be uniquely determined based on the required bus current and oscillation frequency. The equivalent resistance parameters in the circuit can be calculated based on the battery internal resistance and circuit resistance parameters, which are usually in the order of 10mΩ. If the effective value of the current needs to be adjusted later, the loop can be oscillated for multiple cycles before switching to series-parallel connection. The more oscillation cycles, the smaller the effective value of the current.

[0136] The battery heating control method, system and selection method provided by the above embodiments of the present invention effectively avoid the peak voltage generated by the traditional hard-switching charge pump at both ends of the battery and on the device, and significantly improve the reliability of the system operation.

[0137] For the aforementioned method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0138] It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0139] The steps in the methods of each embodiment of the present application can be adjusted in order, combined and deleted according to actual needs, and the technical features recorded in each embodiment can be replaced or combined.

[0140] The modules and sub-modules in the devices and terminals of the various embodiments of the present application can be combined, divided and deleted according to actual needs.

[0141] In the several embodiments provided in the present application, it should be understood that the disclosed terminals, devices and methods can be implemented in other ways. For example, the terminal embodiments described above are only schematic, for example, the division of modules or submodules is only a logical function division, and there may be other division methods in actual implementation, for example, multiple submodules or modules can be combined or integrated into another module, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or modules, which can be electrical, mechanical or other forms.

[0142] The modules or submodules described as separate components may or may not be physically separated, and the components of the modules or submodules may or may not be physical modules or submodules, that is, they may be located in one place, or they may be distributed on multiple network modules or submodules. Some or all of the modules or submodules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0143] In addition, each functional module or submodule in each embodiment of the present application may be integrated into one processing module, or each module or submodule may exist physically separately, or two or more modules or submodules may be integrated into one module. The above-mentioned integrated modules or submodules may be implemented in the form of hardware or in the form of software functional modules or submodules.

[0144] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may 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.

[0145] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly by hardware, software units executed by a processor, or a combination of the two. The software units may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0146] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0147] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery heating control method, characterized in that: include: Obtaining a charging time of a capacitor in a charge pump, wherein the charging time is determined according to an oscillation period of a capacitor charging circuit, and when the charging time of the capacitor in the charge pump reaches the charging time, the current is zero or the current direction is different from the current direction at the charging start time, and the oscillation period of the capacitor charging circuit is determined by the capacitance value, equivalent inductance value and equivalent resistance value in the capacitor charging circuit; the charging time is an odd multiple of a half period of the oscillation period of the capacitor charging circuit; Obtaining a discharge time of the capacitor in the charge pump, wherein the discharge time is determined according to an oscillation period of a capacitor discharge loop, and when the discharge time of the capacitor in the charge pump reaches the discharge time, the current is zero or the current direction is different from the current direction at the discharge start time, and the oscillation period of the capacitor discharge loop is determined by the capacitance value, equivalent inductance value and equivalent resistance value in the capacitor discharge loop; the discharge time is an odd multiple of a half period of the oscillation period of the capacitor discharge loop; Obtaining the dead time of the switch device in the charge pump; the dead time is determined according to the rise and fall time and delay time of the switch device; The switching cycle of the switching device in the charge pump is determined based on the charging time, the discharging time and the dead time to achieve heating of the power battery; wherein, the sum of a half cycle of the circuit oscillation in the capacitor charging state, a half cycle of the circuit oscillation in the capacitor discharging state and the two dead times is taken as the switching cycle.

2. The battery heating control method according to claim 1, characterized in that: The process of determining the charging time and the discharging time includes: Injecting a voltage signal of a first preset frequency into a capacitor charging loop to determine a half period of an oscillation period of the capacitor charging loop; Injecting a voltage signal of a second preset frequency into the capacitor discharge loop to determine a half period of the oscillation period of the capacitor discharge loop; The frequency of the battery voltage signal injected into the capacitor charging circuit is adjusted according to the half period of the oscillation period of the capacitor charging circuit, and the frequency of the battery voltage signal injected into the capacitor discharging circuit is adjusted according to the half period of the oscillation period of the capacitor discharging circuit; wherein the test charging time of the capacitor charging circuit and the test discharging time of the capacitor discharging circuit are continuously reduced; When the effective current values ​​of the capacitor charging circuit and the capacitor discharging circuit match the battery heating rate requirement, the test charging time of the corresponding capacitor charging circuit is used as the charging time, and the test discharge time of the corresponding capacitor discharging circuit is used as the discharge time.

3. The battery heating control method according to claim 2, characterized in that: The step of adjusting the frequency of the battery voltage signal injected into the capacitor charging circuit according to a half period of the capacitor charging circuit oscillation cycle, and adjusting the frequency of the battery voltage signal injected into the capacitor discharging circuit according to a half period of the capacitor discharging circuit oscillation cycle, comprises: Adjust the frequency of the battery voltage signal injected into the capacitor charging loop according to the half-period and multiple adjustment strategy of the capacitor charging loop oscillation period; Adjust the frequency of the battery voltage signal injected into the capacitor discharge loop according to the half period of the capacitor discharge loop oscillation period and the multiple adjustment strategy; The multiple adjustment strategy is that the difference in the test charging time of the capacitor charging circuit after two adjustments is a preset even number of times of half a period of the capacitor charging circuit oscillation period; the difference in the test discharge time of the capacitor discharging circuit after two adjustments is a preset even number of times of half a period of the capacitor discharging circuit oscillation period; wherein, the initial value of the test charging time of the capacitor charging circuit is a preset odd number of times of half a period of the capacitor charging circuit oscillation period, the initial value of the test discharge time of the capacitor discharging circuit is a preset odd number of times of half a period of the capacitor discharging circuit oscillation period, and the test charging time of the capacitor charging circuit and the test discharge time of the capacitor discharging circuit are continuously reduced.

4. A battery heating control system, characterized in that: include: A charge pump connected to both ends of a battery, and a controller connected to a switch device in the charge pump, wherein the controller is used to execute each step of the battery heating control method according to any one of claims 1 to 3.

5. The battery heating control system according to claim 4, characterized in that: Also includes: An absorption circuit is connected in parallel with the switching device in the charge pump.

6. The battery heating control system according to claim 5, characterized in that: The absorption circuit includes: a first resistor and a first capacitor connected in series.

7. The battery heating control system according to claim 5, characterized in that: The absorption circuit further includes: a second resistor, a second capacitor and a diode. The second resistor and the second capacitor are connected in parallel and in series with the diode. The conduction direction of the diode is used to conduct the current of the corresponding switch device along the initial current direction.

8. The battery heating control system according to any one of claims 4 to 7, characterized in that: Also includes: An adjustable inductor connected to the battery bus.

9. A method for selecting a battery heating control system, characterized in that: include: Obtaining a preset switching cycle of the charge pump; Obtaining the dead time of the switch device in the charge pump; Determine the sum of an oscillation period of a capacitor charging loop and an oscillation period of a capacitor discharging loop in the charge pump based on the preset switching period and the dead time; According to the sum value and the relationship between the oscillation period of the capacitor charging circuit and the oscillation period of the capacitor discharging circuit, determine a first expected oscillation period of the capacitor charging circuit oscillation period and a second expected oscillation period of the capacitor discharging circuit oscillation period; wherein the oscillation period of the capacitor charging circuit is twice the oscillation period of the capacitor discharging circuit; Determining the capacitance and parasitic inductance of the capacitor in the charge pump according to the first expected oscillation period, the second expected oscillation period, the battery voltage, and the effective value of the current required by the battery heating rate; The parasitic resistance value in the charge pump is determined according to the battery internal resistance and the line resistance parameters.

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