Heating control method and heating control device of power battery and vehicle

Abstract

The embodiment of the invention discloses a heating control method and device of a power battery and a vehicle, the method is applied to an alternating current heating system, the system comprises the power battery, a capacitor, inductance windings of a three-phase motor and a three-phase inverter, and any phase of inductance winding in the three-phase motor serves as a battery connecting phase; the battery connection phase is connected with the power battery through a first relay, and a second relay is arranged between the battery connection phase and the three-phase inverter; the method comprises the steps that a first relay is controlled to be switched on, a second relay is controlled to be switched off, a charging and discharging loop is formed, and the charging and discharging loop comprises an inductance winding of a three-phase motor, a three-phase inverter, a power battery and a capacitor; and controlling the charging and discharging loop to form charging and discharging current so as to heat the power battery. The power battery is heated under the condition that an independent heating circuit is not additionally arranged, so that the heating cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric vehicles, in particular to a heating control method and device of a power battery and a vehicle. BACKGROUND

[0002] In a low temperature environment, the existing power battery of an electric vehicle generally has problems such as charging difficulty, reduced discharging efficiency and cycle life attenuation, so the power battery needs to be heated before it works. The traditional power battery heating scheme mainly relies on external heating elements such as PTC heaters, which requires modification of the three-phase motor connected to the power battery and additional independent heating circuits, resulting in high heating costs. SUMMARY

[0003] The present application provides a heating control method and device of a power battery and a vehicle, which can heat the power battery without additional independent heating circuits, thereby reducing the heating cost.

[0004] The present application provides the following solutions: According to a first aspect, a heating control method of a power battery is provided, which is applied to an alternating current heating system, the system comprising a power battery, a capacitor, an inductive winding of a three-phase motor and a three-phase inverter, any one phase inductive winding of the three-phase motor being a battery connection phase, the battery connection phase being connected to the power battery through a first relay, and a second relay being arranged between the battery connection phase and the three-phase inverter; The method comprises the following steps: controlling the first relay to be closed and the second relay to be opened, so as to form a charging and discharging circuit, the charging and discharging circuit comprising the inductive winding of the three-phase motor, the three-phase inverter, the power battery and the capacitor; controlling the charging and discharging circuit to form a charging and discharging current, so as to heat the power battery.

[0005] As an optional way, the other two phase inductive windings of the three-phase motor except the battery connection phase are capacitor connection phases, the capacitor connection phases are connected to the capacitor through the three-phase inverter, and the step of controlling the charging and discharging circuit to form a charging and discharging current comprises the following steps: controlling the on-off state of the switching device in the three-phase inverter connected to the capacitor connection phase, so as to increase or decrease the voltage of the capacitor, so that the charging and discharging circuit alternately forms a charging current and a discharging current, the directions of the charging current and the discharging current flowing through the power battery are opposite.

[0006] As an optional way, the step of controlling the on-off state of the switching device in the three-phase inverter connected to the capacitor connection phase comprises the following steps: obtaining a target current signal of the power battery; determining a control signal of a switching device connected to the capacitor connection phase based on the target current signal of the power battery and the current collection signals of the two capacitor connection phases; controlling the on-off state of the switching device connected to the capacitor connection phase based on the control signal.

[0007] As an optional mode, the determination of the control signal of the switching device connected to the capacitor connection phase based on the target current signal of the power battery and the current collection signals of the two capacitor connection phases comprises: performing proportional integral calculation based on the difference between the target current signal and the sum of the two current collection signals to obtain a target duty cycle signal; controlling the switching device in the three-phase inverter connected to the battery connection phase to be disconnected, and determining the control signal of the switching device in the three-phase inverter connected to the capacitor connection phase according to the target duty cycle signal.

[0008] As an optional mode, the obtaining of the target current signal of the power battery comprises: determining the charge-discharge amplitude and the charge-discharge frequency of the battery connection phase when performing sinusoidal alternating charge-discharge based on the pulse heating requirement of the power battery; determining the target current signal of the power battery according to the charge-discharge amplitude and the charge-discharge frequency.

[0009] As an optional mode, before controlling the charge-discharge circuit to form a charge-discharge current to heat the power battery, the method further comprises: adjusting the rotor angle of the three-phase motor to a preset angle to make the phase currents of the two capacitor connection phases the same.

[0010] As an optional mode, a third relay is further arranged between the power battery and the capacitor, and the method further comprises: controlling the third relay to be disconnected when the first relay is closed and the second relay is disconnected; controlling the third relay to be closed when the first relay is disconnected and the second relay is closed, so that the power battery and the capacitor form a power supply circuit.

[0011] As an optional mode, a pre-charging circuit is further arranged between the power battery and the capacitor, the pre-charging circuit comprising a fourth relay and a pre-charging resistor connected in series, and the method further comprises: controlling the fourth relay to be disconnected when the first relay is closed and the second relay is disconnected; When the first relay is disconnected and the second relay is closed, the fourth relay is controlled to be closed, so that the power battery, the pre-charging resistor and the capacitor form a pre-charging loop.

[0012] According to a second aspect, a heating control device is provided. The device is applied to an AC heating system. The system includes a power battery, a capacitor, an inductor winding of a three-phase motor, and a three-phase inverter. Any one phase of the inductor winding of the three-phase motor serves as a battery connection phase. The battery connection phase is connected to the power battery via a first relay. A second relay is provided between the battery connection phase and the three-phase inverter. Wherein, the device comprises: a path control module configured to control the first relay to be closed and the second relay to be open, thereby forming a charge-discharge loop, wherein the charge-discharge loop includes the inductor winding of the three-phase motor, the three-phase inverter, the power battery, and the capacitor; The current control module is configured to control the charge-discharge circuit to form a charge-discharge current to heat the power battery.

[0013] According to a third aspect, there is provided a vehicle comprising: An AC heating system comprising a power battery, a capacitor, an inductor winding of a three-phase motor, and a three-phase inverter, wherein any one inductor winding of the three-phase motor serves as a battery connection phase, the battery connection phase being connected to the power battery via a first relay, and a second relay being provided between the battery connection phase and the three-phase inverter; A controller is used to execute the steps of the method described in the first aspect above.

[0014] The solution provided by the embodiment of the present application is based on the original system including a power battery, a capacitor, an inductor winding of a three-phase motor and a three-phase inverter. The inductor winding of any one phase of the three-phase motor is used as the battery connection phase, a first relay connecting the battery connection phase and the power battery is added, and a second relay is added between the battery connection phase and the three-phase inverter. When the first relay is closed and the second relay is disconnected, the inductor winding of the three-phase motor and the three-phase inverter can form a charge-discharge circuit. The charge-discharge circuit includes the inductor winding of the three-phase motor, the three-phase inverter, the power battery and the capacitor, and the charge-discharge circuit can be controlled to form a charge-discharge current, so that The power battery and the capacitor can be charged and discharged via an AC charging and discharging circuit to heat the power battery; it can be understood that the present application only requires a new relay switch to ensure the formation of a charging and discharging circuit between the power battery and the capacitor, so that the AC current can flow repeatedly between the power battery and the capacitor, and the power battery and the capacitor are alternately charged and discharged, and then the internal resistance of the power battery itself can be used to generate heat to achieve the purpose of heating the power battery. Compared with traditional solutions that rely on external heating elements such as PTC heaters, the present application does not require structural changes to the three-phase motor, nor does it require the addition of an independent heating circuit, which can effectively reduce heating costs.

[0015] Of course, any product implementing the present application does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A circuit architecture diagram applicable to an embodiment of the present application.

[0018] Figure 2 This is a flow chart of a heating control method for a power battery provided in an embodiment of the present application.

[0019] Figure 3 This is an electrical connection diagram in the heating mode of the power battery heating control method provided in an embodiment of the present application.

[0020] Figure 4 This is a current flow diagram of the power battery discharge in the power battery heating control method provided in an embodiment of the present application.

[0021] Figure 5 This is a current flow diagram for charging a power battery in the power battery heating control method provided in an embodiment of the present application.

[0022] Figure 6 This is a control block diagram of the target current signal in the power battery heating control method provided in an embodiment of the present application.

[0023] Figure 7 This is an electrical connection diagram in the power mode of the power battery heating control method provided in an embodiment of the present application.

[0024] Figure 8 This is a flow chart of an example of a heating mode in the heating control method for a power battery provided in an embodiment of the present application.

[0025] Figure 9 A schematic block diagram of an AC heating system for a power battery provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0027] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a," "an," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0028] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0029] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0030] In the existing technology, under low temperature environment, the power batteries of existing electric vehicles generally have problems such as difficulty in charging, reduced discharge efficiency and decreased cycle life. Therefore, it is necessary to heat the power batteries before working. The traditional power battery heating solution mainly relies on external heating elements such as PTC heaters, which requires modifications to the three-phase motor connected to the power battery and the addition of an independent heating circuit, resulting in high heating costs.

[0031] In order to solve the above problems, the inventors of this application found that using the existing electrical components of the vehicle for energy conversion can avoid the addition of external heating elements. Therefore, by analyzing the energy interaction characteristics between the three-phase motor and the power battery and capacitor, it is proposed to use the inductor winding in the three-phase motor as part of the charging and discharging circuit, and use the charging and discharging process of alternating current to generate heat, thereby achieving heating of the power battery.

[0032] Therefore, the present application provides a heating control method, a heating control device, and a vehicle for a power battery, so as to heat the power battery without adding an independent heating circuit, thereby reducing the heating cost.

[0033] refer to Figure 1 , Figure 1 A circuit architecture diagram applicable to the embodiment of the present application; Figure 1 As shown, the circuit architecture is used in control scenarios related to power batteries and is used to implement the heating control method of the power battery in this application; wherein, the power battery provides electrical energy for the entire circuit, K1 is the third relay, K2 is the fourth relay, K2 is connected in series with the pre-charge resistor R1, and is used to control the on-off and pre-charging of the circuit; K3 and K4 are the first relay and the second relay, respectively, for ensuring that the charge and discharge circuit is turned on in the heating mode; C1 is a capacitor, which can be a thin film capacitor of the motor controller and can participate in the charging and discharging process; S1 to S6 are switching devices in the three-phase inverter, which can be IGBT switching tubes, used to form a three-phase inverter bridge in the three-phase inverter, and the inductor windings L1, L2, L3 in the three-phase motor. Connection; any one of the inductor windings L1, L2, and L3 in the three-phase motor can be used as a battery connection phase, connected to the power battery through the first relay, and can be used as a capacitor connection phase, connected to the capacitor through the second relay. A1 and A2 are current acquisition elements for obtaining the current acquisition signal of the capacitor connection phase; based on the above circuit architecture, the present application can control the charge and discharge circuit to form a charge and discharge current to heat the power battery. For example, in the heating mode, the first relay is controlled to be closed and the second relay is disconnected to form a charge and discharge current, so that Joule heat is generated inside the power battery to complete the heating, and in the power mode, the first relay is controlled to be disconnected and the second relay is closed to meet the vehicle power output requirements.

[0034] refer to Figure 2 , Figure 2 Flowchart of the heating control method of the power battery provided in the embodiment of the present application; Figure 2 The present application provides a heating control method for a power battery, which is applied to an AC heating system. The AC heating system includes a power battery, a capacitor, an inductor winding of a three-phase motor, and a three-phase inverter. Any one phase of the inductor winding of the three-phase motor serves as a battery connection phase. The battery connection phase is connected to the power battery via a first relay, and a second relay is provided between the battery connection phase and the three-phase inverter. The control method may include at least the following steps: Step 201: Control the first relay to close and the second relay to open, thereby forming a charge-discharge loop, which includes the inductor winding of the three-phase motor, the three-phase inverter, the power battery, and the capacitor; Step 202 : Control the charge-discharge circuit to generate a charge-discharge current to heat the power battery.

[0035] Among them, the three-phase motor has three inductor windings, refer to Figure 3 , Figure 3 In the heating control method of the power battery provided in the embodiment of the present application, the electrical connection diagram in the heating mode; Figure 3 The V-phase inductor winding can be used as a battery connection phase to connect to the power battery, and the U-phase and W-phase inductor windings can be used as capacitor connection phases to connect to the capacitor through a three-phase inverter. The three-phase inverter is used to invert current to form a charging and discharging current as alternating current.

[0036] In some embodiments, the first relay (corresponding to Figure 1 K3 in the figure) is set between the battery connection phase and the positive terminal of the power battery, and the second relay (corresponding to Figure 1 K4 in the figure is set between the battery connection phase and the three-phase inverter. The three-phase inverter is connected in parallel with the capacitor. The positive terminal of the capacitor is connected to the positive terminal of the power battery through the pre-charging circuit (including the fourth relay K2 and the pre-charging resistor R1) and the parallel power supply circuit (including the third relay K1). The negative terminal is directly connected to the negative terminal of the power battery. Relays K1 to K4 can be electromagnetic or solid-state relays to control the on and off of the current path between the power battery and the capacitor.

[0037] like Figure 3As shown, the present application uses, on the basis of the original system including a power battery, a capacitor, an inductor winding of a three-phase motor and a three-phase inverter, any one phase inductor winding of the three-phase motor is used as the battery connection phase, a first relay connecting the battery connection phase and the power battery is added, and a second relay is added between the battery connection phase and the three-phase inverter, so that when the first relay is closed and the second relay is disconnected, the inductor winding of the three-phase motor and the three-phase inverter can form a charge-discharge circuit, which includes the inductor winding of the three-phase motor, the three-phase inverter, the power battery and the capacitor, and then the charge-discharge circuit can be controlled to form a charge-discharge current, so that the power battery The battery and capacitor can be charged and discharged by AC through the charge and discharge circuit to heat the power battery; it can be understood that the present application can ensure the formation of the charge and discharge circuit between the power battery and the capacitor by only adding a relay switch, so that the AC current can flow repeatedly between the power battery and the capacitor, and the power battery and the capacitor are alternately charged and discharged, and then the internal resistance of the power battery itself can be used to generate heat to achieve the purpose of heating the power battery. Compared with the traditional solution that relies on external heating elements such as PTC heaters, the present application does not require structural changes to the three-phase motor, nor does it require the addition of an independent heating circuit, which can effectively reduce the heating cost.

[0038] In some embodiments, the other two-phase inductance windings of the three-phase motor except the battery-connected phase serve as capacitor-connected phases, and the capacitor-connected phases are connected to the capacitor through a three-phase inverter to control the charge and discharge current formed in the charge and discharge circuit, including: controlling the on and off states of the switching devices in the three-phase inverter to which the capacitor-connected phase is connected, so that the inductance windings of the three-phase inverter store and release energy in a cycle to increase or decrease the voltage of the capacitor, so that the charge and discharge circuit alternately forms charging current and discharging current, and the charging current and the discharging current flow through the power battery in opposite directions.

[0039] The above process can achieve energy storage and energy release management of the inductor winding by adjusting the on-off state of the switching device, so as to control the charge and discharge circuit to alternately form charging current and discharge current: it can be understood that when the discharge current of the power battery is required, the inductor winding of the capacitor-connected phase is put into the energy storage state by setting the control signal of the target duty cycle. At this time, the electrical energy output by the power battery and the magnetic field energy stored in the inductor work together through the three-phase inverter to transfer energy to the capacitor, forming a Boost circuit and achieving a voltage increase of the capacitor.

[0040] Conversely, when the battery charging current needs to be switched, the duty cycle of the control signal is adjusted to put the inductor winding into a discharge state. At this point, the energy stored in the capacitor and the energy released by the inductor are reversely transferred to the battery via the three-phase inverter, forming a buck circuit to reduce the capacitor voltage.

[0041] refer to Figure 4and Figure 5 , Figure 4 The current flow chart of the power battery discharging in the heating control method of the power battery provided by the embodiment of the application, Figure 5 The current flow chart of the power battery charging in the heating control method of the power battery provided by the embodiment of the application: it can be understood that in the heating control scenario of the application, the Boost circuit is reflected in the process of discharging the power battery to the capacitor. As shown in Figure 4 , in the power battery discharging stage, the current flows out from the positive electrode of the power battery, flows to the battery connection phase (such as L2) in the three-phase motor through the circuit, and flows through the capacitor connection phase (such as L1 and L3), the on-off state of the switching device in the three-phase inverter connected to the capacitor connection phase is controlled, so that the inductance (L1, L3) of the three-phase motor enters the energy storage state, and the charging and discharging circuit is equivalent to the boost circuit: part of the energy released by the power battery is stored through the inductance, and the other part directly charges the capacitor C1, realizes the voltage rise between the power battery and the capacitor, and completes the energy transfer of the forward current.

[0042] On the contrary, the Buck circuit corresponds to the stage of charging the capacitor to the power battery. As shown in Figure 5 , in the power battery charging stage, the current flows out from the positive electrode of the capacitor, flows to the capacitor connection phase (such as L1 and L3) after being regulated by the three-phase inverter, and then flows through the battery connection phase (such as L2) to return to the positive electrode of the power battery. At this time, the on-off state of the switching device in the three-phase inverter connected to the capacitor connection phase is controlled, so that the inductance (L1, L3) enters the energy release state, and the charging and discharging circuit is equivalent to the buck circuit: the energy stored by the capacitor and the energy released by the inductance are jointly charged to the power battery, realizing the energy recovery of the reverse current.

[0043] In some embodiments, the switching device in the three-phase inverter connected to the capacitor connection phase includes an upper bridge arm switch tube and a lower bridge arm switch tube, the upper bridge arm switch tube is connected to the positive electrode of the power battery, and the lower bridge arm switch tube is connected to the negative electrode of the power battery, the on-off state of the switching device connected to the capacitor connection phase is controlled based on the control signal, including: based on the control signal, the upper bridge arm switch tube connected to the capacitor connection phase is switched from the open state to the closed state, and the lower bridge arm switch tube connected to the capacitor connection phase is switched from the closed state to the open state, so that the charging and discharging circuit works as a boost circuit to form a charging current; based on the control signal, the upper bridge arm switch tube connected to the capacitor connection phase is switched from the closed state to the open state, and the lower bridge arm switch tube connected to the capacitor connection phase is switched from the open state to the closed state, so that the charging and discharging circuit works as a buck circuit to form a discharging current.

[0044] In which, as Figure 1As shown, S1, S2, and S3 are the upper-arm switching tubes, and S4, S5, and S6 are the lower-arm switching tubes. The complementary switching of the upper-arm switching tube and the lower-arm switching tube is used to realize bidirectional energy conversion. When the upper-arm switching tube of the capacitor connection phase is closed and the lower-arm switching tube is disconnected, the electric energy of the power battery flows into the capacitor through the inductor winding. At this time, the inductor stores part of the energy in the form of a magnetic field. After being superimposed on the battery output voltage, the voltage at the capacitor terminal increases. At this time, the current flows from the power battery to the capacitor, forming a discharge process for the battery; when the upper-arm switching tube is disconnected and the lower-arm switching tube is closed, the high-voltage electric energy stored in the capacitor drives the current to flow in the opposite direction, and the inductor winding releases the previously stored energy, which is transmitted to the power battery together with the capacitor energy. At this time, the circuit is equivalent to a buck topology. The capacitor voltage is reduced after being buffered by the inductor energy release, adapting to the charging needs of the power battery, forming a battery charging process.

[0045] It is understood that the alternating switching of the above-mentioned switching states can be achieved by a control signal generated according to the target duty cycle signal, ensuring that the upper and lower arm switches are not turned on at the same time in the same cycle to avoid the risk of short circuit. At the same time, by adjusting the on-time ratio, the energy storage and release cycles of the inductor are controlled, so that the amplitude and frequency of the charge and discharge currents match the heating requirements of the power battery. For example, when the heating power needs to be increased, the on-duty cycle of the upper arm switch can be increased to enhance the boost effect and increase the discharge current amplitude. At the same time, the on-duty cycle of the lower arm switch can be adjusted accordingly to ensure the reverse balance of the charging current, thereby achieving efficient heating through the periodic work done by the current on the battery's internal resistance.

[0046] refer to Figure 6 , Figure 6 A control block diagram of a target current signal in a heating control method for a power battery provided in an embodiment of the present application; Figure 6 As shown, in some embodiments, controlling the on-off state of the switching device in the three-phase inverter to which the capacitor-connected phase is connected includes: obtaining a target current signal of the power battery; determining a control signal of the switching device connected to the capacitor-connected phase based on the target current signal of the power battery and the current acquisition signals of the two capacitor-connected phases; and controlling the on-off state of the switching device connected to the capacitor-connected phase based on the control signal.

[0047] Among them, the target current signal refers to the phase current set value that the battery charging and discharging current needs to reach, and the current acquisition signal refers to the actual current measurement value of the capacitor-connected phase, which is used to feedback the actual current state. By comparing the deviation between the target current signal of the power battery and the current acquisition signals of the two capacitor-connected phases, adjustments can be made, and then the on-off state of the switching devices in the three-phase inverter can be adjusted to form the charging and discharging current.

[0048] It can be understood that the control signal of the switching device connected to the capacitor connection phase refers to the electrical signal used to regulate the on-off state of the power switching device connected to the capacitor connection phase in the three-phase inverter. Its function is to achieve the adjustment of the direction, magnitude and change rate of the capacitor connection phase current by controlling the on and off rhythm of the switching device, so as to cooperate with the charging and discharging process of the power battery and capacitor to complete the heating.

[0049] It's worth noting that the control signal determines the direction and magnitude of the current in the capacitor-connected phase by changing the on / off state of the switching device, thereby achieving alternating switching between boost discharge and buck charging modes between the power battery and capacitor. Specifically, when the power battery needs to discharge the capacitor, the control signal drives the switching device on with a high duty cycle, causing the inductor winding in the capacitor-connected phase to enter an energy storage state. Subsequently, the control signal turns low, the switching device turns off, and the inductor releases energy, which is superimposed on the power battery voltage, forming a current higher than the battery voltage flowing to the capacitor, completing the discharge. At this time, the duty cycle of the control signal determines the boost amplitude. Conversely, when the capacitor needs to charge the power battery, the control signal drives the switching device on with a low duty cycle, causing the current released by the capacitor to flow through the inductor and store some energy. After the switch device is turned off, the inductor releases energy, which, after superimposing on the capacitor current, flows to the power battery at a level lower than the capacitor voltage, completing the charging. At this time, the duty cycle of the control signal determines the buck amplitude.

[0050] In some embodiments, obtaining a target current signal of a power battery includes: determining a charge and discharge amplitude and a charge and discharge frequency when the battery connection phase performs sinusoidal AC charge and discharge based on a pulse heating requirement of the power battery; and determining the target current signal of the power battery based on the charge and discharge amplitude and the charge and discharge frequency.

[0051] Among them, the pulse heating demand may include parameters such as the difference between the current temperature of the power battery and the target temperature, the maximum allowable heating time, etc. The charge and discharge amplitude may correspond to the peak value of the sinusoidal AC current, and its magnitude is positively correlated with the heating power. The charge and discharge frequency may match the resonant characteristics formed by the inductor winding and capacitor of the three-phase motor, and be selected within a preset range to avoid switching losses at high frequencies or excessive current ripple at low frequencies.

[0052] It can be understood that after determining the charge and discharge amplitude and charge and discharge frequency, the value of the target current signal can be obtained by the current waveform formula I= A sin(2*π *f* t) is obtained, where I is the target current signal, is the charge and discharge amplitude, is the AC charge and discharge frequency, π is the mathematical constant representing pi, t is the time variable, π is the mathematical constant representing pi, t is the time variable.

[0053] In some embodiments, based on the target current signal of the power battery and the current acquisition signals of the two capacitor connection phases, the control signal of the switching device connected to the capacitor connection phase is determined, including: performing a proportional integral calculation based on the difference between the target current signal and the sum of the two current acquisition signals to obtain a target duty cycle signal; controlling the switching device in the three-phase inverter connected to the battery connection phase to disconnect, and determining the control signal of the switching device in the three-phase inverter connected to the capacitor connection phase according to the target duty cycle signal.

[0054] Among them, the proportional-integral calculation refers to adjusting the difference between the target current signal and the sum of the two current acquisition signals through a combination of a proportional link and an integral link. Specifically, it can be implemented by a proportional-integral controller PID. The target duty cycle signal can be generated by pulse width modulation technology to determine the control signal of the switching device in the three-phase inverter connected to the capacitor connection phase, and then the ratio of the on-time and off-time of the switching device is modulated through the control signal to adjust the phase current of the capacitor connection phase.

[0055] It can be understood that when the difference between the target current signal and the sum of the two current acquisition signals is converted into a target duty cycle signal through proportional integral calculation, it is also necessary to disconnect the switching device in the three-phase inverter connected to the battery connection phase to avoid the formation of an interference loop. Then, a control signal can be generated according to the target duty cycle signal, and the switching frequency of the switching device in the three-phase inverter connected to the capacitor connection phase can be adjusted based on the control signal, thereby controlling the phase current of the capacitor connection phase.

[0056] In some embodiments, before controlling the charge-discharge circuit to form the charge-discharge current to heat the power battery, it also includes: adjusting the rotor angle of the three-phase motor to a preset angle so that the phase currents of the two capacitor-connected phases are the same.

[0057] The preset angle is 120 degrees, based on the spatial distribution characteristics of the three-phase motor windings. When the rotor angle is positioned at 120 degrees, the inductor windings of the two capacitor-connected phases (such as phases U and W) are uniformly coupled to the rotor magnetic field, resulting in the same equivalent impedance. In this state, when symmetrical control signals are applied through the three-phase inverter, the two capacitor-connected phases generate phase currents of equal magnitude and matching direction.

[0058] It is understandable that the motor has no torque output. When the motor is stationary, energy is only transferred between the battery and the capacitor. Therefore, when the V-phase end of the three-phase motor is connected to the positive pole of the power battery as the battery connection phase, the current of the charge and discharge circuit is equal to the battery charge and discharge current. At the same time, the 120-degree pre-positioning can make the forces generated by the currents of the two capacitor connection phases in the magnetic field balance each other, ensuring that the output torque of the three-phase motor is zero and preventing the motor from rotating during the heating process. This ensures that energy is only transferred between the power battery and the capacitor, avoiding energy loss caused by motor rotation. This pre-positioning step lays the foundation for the subsequent control of the symmetry of the charge and discharge current through the three-phase inverter, ensuring the stability of the current waveform during the charge and discharge process, and improving heating efficiency and control accuracy.

[0059] It is worth noting that the V-phase end of the three-phase motor is connected to the positive pole of the power battery as the battery connection phase. When the motor has no torque output, the current of the charge and discharge circuit is equal to the battery charge and discharge current, and energy is only transferred between the battery and the capacitor.

[0060] refer to Figure 7 , Figure 7 In the heating control method of the power battery provided in the embodiment of the present application, the electrical connection diagram in the power mode; Figure 7 The present application further proposes that a third relay is provided between the power battery and the capacitor, and the method further includes: when the first relay is closed and the second relay is disconnected, controlling the third relay to disconnect; when the first relay is disconnected and the second relay is closed, controlling the third relay to close, so that the power battery and the capacitor form a power supply circuit.

[0061] In some embodiments, a pre-charging circuit is further provided between the power battery and the capacitor, and the pre-charging circuit includes a fourth relay and a pre-charging resistor connected in series. The method further includes: when the first relay is closed and the second relay is disconnected, controlling the fourth relay to disconnect; when the first relay is disconnected and the second relay is closed, controlling the fourth relay to close, so that the power battery, the pre-charging resistor and the capacitor form a pre-charging circuit.

[0062] Among them, a pre-charging circuit and a power supply circuit connected in parallel with the pre-charging circuit as the main positive output of the motor are also provided between the power battery and the capacitor. The pre-charging circuit includes a fourth relay and a pre-charging resistor, and the power supply circuit includes a third relay. After controlling the charge and discharge circuit to form a charge and discharge current, it also includes: controlling the first relay to disconnect and the second relay to close, and controlling the on and off states of the third relay and the fourth relay according to the output power requirement of the power battery.

[0063] Among them, the pre-charging circuit refers to the current limiting path formed by the fourth relay and the pre-charging resistor in series, which can be implemented by a combination of an electromagnetic relay and a carbon film resistor, and is used to limit the capacitor charging current when the system starts; the power supply circuit refers to a low-impedance path formed by direct connection of the third relay, which can be implemented by a high-power contactor, and is used to provide a low-loss current path when the system is running stably; the power mode refers to the vehicle being in driving or energy output state. At this time, the AC heating system needs to adjust the circuit topology according to the driving requirements. The coordinated control of the third relay and the fourth relay can realize the current grading management of the capacitor charging process.

[0064] It can be understood that after the present application completes heating the power battery in the heating mode, it can enter the power mode to enable the power battery to operate normally. In this state, the first relay can be disconnected to cut off the charging and discharging circuit, and the second relay can be closed to activate the capacitor connection phase. At this time, the pre-charging circuit is turned on first, and the pre-charging resistor limits the initial charging current of the capacitor to avoid inrush current from impacting the three-phase inverter. Then, when the capacitor voltage reaches the preset threshold, the third relay closes to bypass the pre-charging circuit, reducing the conduction loss, so that the AC heating system can dynamically adjust the switching timing of the fourth relay and the third relay according to the real-time output power demand, such as extending the working time of the pre-charging circuit when the power demand is low, and quickly switching to the power supply circuit when the power demand is high, effectively suppressing the impact of current mutation on circuit elements and improving circuit reliability.

[0065] refer to Figure 8 , Figure 8 This is an example flow chart of a heating mode in the heating control method of the power battery provided in an embodiment of the present application; Figure 8 As shown, the present application can be in low temperature conditions, the vehicle is in neutral gear, and after the three-phase motor reaches a predetermined position with a rotor angle of 120 degrees, it switches to the pulse heating mode; further, during pulse heating, the present application can operate as follows Figure 6 The target current signal control process is to first use Boost to increase the voltage so that the power battery charges the capacitor. At this time, the current is a positive sinusoidal current. Then, the control logic Buck is used to reduce the voltage so that the capacitor charges the power battery. At this time, the current is a negative sinusoidal current. This allows the power battery and the capacitor to perform AC charging and discharging through the charge and discharge circuit, thereby heating the power battery without adding an independent heating circuit, thereby reducing the heating cost.

[0066] refer to Figure 9 , Figure 9 A schematic block diagram of an AC heating system for a power battery provided in an embodiment of the present application; Figure 9As shown, the present application further provides a heating control device 900, which is applied to an AC heating system. The system includes a power battery, a capacitor, an inductor winding of a three-phase motor and a three-phase inverter. Any one-phase inductor winding of the three-phase motor serves as a battery connection phase, and the battery connection phase is connected to the power battery through a first relay. A second relay is provided between the battery connection phase and the three-phase inverter; wherein, the device includes: a path control module 901, which is configured to control the first relay to close and the second relay to open, to form a charge-discharge loop, and the charge-discharge loop includes the inductor winding of the three-phase motor, the three-phase inverter, the power battery and the capacitor; a current control module 902, which is configured to control the charge-discharge loop to form a charge-discharge current to heat the power battery.

[0067] Among them, the AC heating system refers to a circuit structure composed of a power battery, a capacitor and a charge-discharge circuit. Specifically, it can be implemented by using one-phase inductance winding of a three-phase motor as a battery connection phase to connect to the power battery, and the remaining two-phase inductance windings as capacitor connection phases to connect to the capacitor through a three-phase inverter. The three-phase motor and the three-phase inverter realize bidirectional energy flow. The three-phase inverter refers to a circuit unit for converting AC power into DC power. Specifically, it can be implemented by using a three-phase full-bridge rectifier circuit or a bridge arm circuit composed of multiple insulated gate bipolar transistors. The charge-discharge circuit is controlled by controlling the on-off state of the switching devices in the three-phase inverter to form a charge-discharge current. The current control module 902 refers to a processor for executing the heating control algorithm, which can be implemented by a microcontroller or a digital signal processor.

[0068] In some embodiments, the other two-phase inductance windings of the three-phase motor except the battery-connected phase serve as capacitor-connected phases, and the capacitor-connected phases are connected to the capacitor through a three-phase inverter. When controlling the formation of charge and discharge currents in the charge and discharge circuit, the current control module 902 is further configured to: control the on-off state of the switching device in the three-phase inverter to which the capacitor-connected phase is connected, so that the inductance winding of the three-phase inverter stores and releases energy in a cycle to increase or decrease the voltage of the capacitor, so that the charge and discharge circuit alternately forms charging current and discharging current, and the charging current and the discharging current flow through the power battery in opposite directions.

[0069] In some embodiments, when controlling the on-off state of the switching device in the three-phase inverter connected to the capacitor-connected phase, the current control module 902 is further configured to: obtain the target current signal of the power battery; determine the control signal of the switching device connected to the capacitor-connected phase based on the target current signal of the power battery and the current acquisition signals of the two capacitor-connected phases; and control the on-off state of the switching device connected to the capacitor-connected phase based on the control signal.

[0070] In some embodiments, when determining the control signal of the switching device connected to the capacitor connection phase based on the target current signal of the power battery and the current acquisition signals of the two capacitor connection phases, the current control module 902 is further configured to: perform a proportional integral calculation based on the difference between the target current signal and the sum of the two current acquisition signals to obtain a target duty cycle signal; control the switching device in the three-phase inverter connected to the battery connection phase to disconnect, and determine the control signal of the switching device in the three-phase inverter connected to the capacitor connection phase according to the target duty cycle signal.

[0071] In some embodiments, when obtaining the target current signal of the power battery, the current control module 902 is further configured to: determine the charge and discharge amplitude and charge and discharge frequency when the battery connection phase performs sinusoidal AC charge and discharge based on the pulse heating requirements of the power battery; and determine the target current signal of the power battery according to the charge and discharge amplitude and charge and discharge frequency.

[0072] In some embodiments, the switching devices in the three-phase inverter connected to the capacitor connection phase include an upper bridge arm switching tube and a lower bridge arm switching tube. The upper bridge arm switching tube is connected to the positive pole of the power battery, and the lower bridge arm switching tube is connected to the negative pole of the power battery. Based on the control signal, when the on-off state of the switching device connected to the capacitor connection phase is controlled, the current control module 902 is also configured as follows: based on the control signal, the upper bridge arm switching tube connected to the capacitor connection phase is controlled to switch from an open state to a closed state, and the lower bridge arm switching tube connected to the capacitor connection phase is controlled to change from a closed state to an open state, so that the charging and discharging circuit acts as a boost circuit to form a charging current; based on the control signal, the upper bridge arm switching tube connected to the capacitor connection phase is controlled to change from a closed state to an open state, and the lower bridge arm switching tube connected to the capacitor connection phase is controlled to switch from an open state to a closed state, so that the charging and discharging circuit acts as a step-down circuit to form a discharge current.

[0073] In some embodiments, before controlling the charge and discharge circuit to form a charge and discharge current to heat the power battery, the current control module 902 is further configured to: adjust the rotor angle of the three-phase motor to a preset angle so that the phase currents of the two capacitor-connected phases are the same.

[0074] In some embodiments, a third relay is further provided between the power battery and the capacitor, and the path control module 901 is further configured to: when the first relay is closed and the second relay is disconnected, control the third relay to be disconnected; when the first relay is disconnected and the second relay is closed, control the third relay to be closed, so that the power battery and the capacitor form a power supply circuit.

[0075] In some embodiments, a pre-charging circuit is further provided between the power battery and the capacitor, and the pre-charging circuit includes a fourth relay and a pre-charging resistor connected in series. The path control module 901 is further configured to: when the first relay is closed and the second relay is disconnected, control the fourth relay to be disconnected; when the first relay is disconnected and the second relay is closed, control the fourth relay to be closed, so that the power battery, the pre-charging resistor and the capacitor form a pre-charging circuit.

[0076] The present application further proposes a vehicle, which may include: an AC heating system, the system including a power battery, a capacitor, an inductor winding of a three-phase motor and a three-phase inverter, wherein any one phase of the inductor winding of the three-phase motor serves as a battery connection phase, the battery connection phase is connected to the power battery through a first relay, and a second relay is provided between the battery connection phase and the three-phase inverter; a controller, for executing the steps of the method of the first aspect above, so as to have the effect of heating the power battery of any one of the embodiments of the first and second aspects above without adding an independent heating circuit to reduce the heating cost, so it will not be repeated here.

[0077] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, 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 through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0078] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0079] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0080] In the above embodiments, all or part of the embodiments can be implemented using software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments can be implemented in the form of a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions according to the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be read by a computer or a data storage device such as a server or data center that integrates one or more available media. Available media may be magnetic media (eg, floppy disks, hard disks, tapes), optical media (eg, digital versatile discs (DVDs)), or semiconductor media (eg, solid state disks (SSDs)).

[0081] The above describes the technical solution provided by this application in detail. Specific examples are used herein to illustrate the principles and implementation methods of this application. The description of the above embodiments is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the contents of this specification should not be understood as limiting this application.

Claims

1. A heating control method for a power battery, characterized in that: The method is applied to an AC heating system, which includes a power battery, a capacitor, an inductor winding of a three-phase motor, and a three-phase inverter. Any one phase of the inductor winding of the three-phase motor serves as a battery connection phase. The battery connection phase is connected to the power battery via a first relay, and a second relay is provided between the battery connection phase and the three-phase inverter. The method comprises: Controlling the first relay to close and the second relay to open to form a charge-discharge loop, wherein the charge-discharge loop includes the inductor winding of the three-phase motor, the three-phase inverter, the power battery, and the capacitor; The charge-discharge circuit is controlled to form a charge-discharge current to heat the power battery.

2. The method according to claim 1, characterized in that The other two inductive windings of the three-phase motor except the battery-connected phase serve as capacitor-connected phases, the capacitor-connected phases are connected to the capacitor via the three-phase inverter, and the controlling of the charge-discharge circuit to form a charge-discharge current includes: The on-off state of the switching device in the three-phase inverter to which the capacitor connection phase is connected is controlled to increase or decrease the voltage of the capacitor, so that the charge and discharge circuit alternately forms a charging current and a discharging current, and the charging current and the discharging current flow through the power battery in opposite directions.

3. The method according to claim 2, characterized in that The controlling the on-off state of the switching device in the three-phase inverter to which the capacitor-connected phase is connected includes: Obtaining a target current signal of the power battery; determining, based on the target current signal of the power battery and the current acquisition signals of the two capacitor-connected phases, a control signal of a switching device connected to the capacitor-connected phase; Based on the control signal, the on-off state of the switching device connected to the capacitor connection phase is controlled.

4. The method according to claim 3, characterized in that The determining, based on the target current signal of the power battery and the current acquisition signals of the two capacitor-connected phases, the control signal of the switching device connected to the capacitor-connected phase comprises: Performing proportional integral calculation based on the difference between the target current signal and the sum of the two current acquisition signals to obtain a target duty cycle signal; The switching device in the three-phase inverter connected to the battery connection phase is controlled to be disconnected, and a control signal for the switching device in the three-phase inverter connected to the capacitor connection phase is determined according to the target duty cycle signal.

5. The method according to claim 3, characterized in that The obtaining of the target current signal of the power battery includes: Determining, based on the pulse heating requirements of the power battery, a charge and discharge amplitude and a charge and discharge frequency when the battery connection phase performs sinusoidal AC charge and discharge; A target current signal of the power battery is determined according to the charge and discharge amplitude and the charge and discharge frequency.

6. The method according to claim 2, characterized in that Before controlling the charge-discharge circuit to form the charge-discharge current, the method further includes: The rotor angle of the three-phase motor is adjusted to a preset angle so that the phase currents of the two capacitor-connected phases are the same.

7. The method according to any one of claims 1 to 6, characterized in that A third relay is further provided between the power battery and the capacitor, and the method further comprises: When the first relay is closed and the second relay is open, controlling the third relay to be open; When the first relay is disconnected and the second relay is closed, the third relay is controlled to be closed, so that the power battery and the capacitor form a power supply circuit.

8. The method according to any one of claims 1 to 6, characterized in that A pre-charging circuit is further provided between the power battery and the capacitor, the pre-charging circuit including a fourth relay and a pre-charging resistor connected in series, and the method further includes: When the first relay is closed and the second relay is open, controlling the fourth relay to be open; When the first relay is disconnected and the second relay is closed, the fourth relay is controlled to be closed, so that the power battery, the pre-charging resistor and the capacitor form a pre-charging loop.

9. A heating control device, characterized in that: The device is applied to an AC heating system, which includes a power battery, a capacitor, an inductor winding of a three-phase motor, and a three-phase inverter. Any one phase of the inductor winding of the three-phase motor serves as a battery connection phase. The battery connection phase is connected to the power battery via a first relay, and a second relay is provided between the battery connection phase and the three-phase inverter. Wherein, the device comprises: a path control module configured to control the first relay to be closed and the second relay to be open, thereby forming a charge-discharge loop, wherein the charge-discharge loop includes the inductor winding of the three-phase motor, the three-phase inverter, the power battery, and the capacitor; The current control module is configured to control the charge-discharge circuit to form a charge-discharge current to heat the power battery.

10. A vehicle, characterized in that: include: An AC heating system comprising a power battery, a capacitor, an inductor winding of a three-phase motor, and a three-phase inverter, wherein any one inductor winding of the three-phase motor serves as a battery connection phase, the battery connection phase being connected to the power battery via a first relay, and a second relay being provided between the battery connection phase and the three-phase inverter; A controller for executing the steps of the method according to any one of claims 1 to 8.

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