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 a charging and discharging loop to form charging and discharging current based on the rotor angle of the three-phase motor 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, and in particular to a heating control method, a heating control device, and a vehicle for a power battery. Background Art

[0002] In low-temperature environments, the power batteries of existing electric vehicles generally have problems such as difficulty in charging, reduced discharge efficiency, and decreased cycle life. Therefore, the power batteries need to be heated before working. Traditional power battery heating solutions mainly rely on external heating elements such as PTC heaters, which require modifications to the three-phase motor connected to the power battery and the addition of an independent heating circuit, resulting in high heating costs. Summary of the Invention

[0003] The present application provides a power battery heating control method, a heating control device, and a vehicle, which are used to heat the power battery without adding an independent heating circuit, thereby reducing heating costs.

[0004] This application provides the following solutions: According to a first aspect, a power battery heating control method is provided. The method is applied to an AC heating system, wherein 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, 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 and discharge circuit is controlled based on the rotor angle of the three-phase motor to form a charge and discharge current to heat the power battery.

[0005] As an optional embodiment, the other two phase inductor windings of the three-phase motor except the battery-connected phase are respectively used as capacitor-connected phases, and each of the capacitor-connected phases is respectively connected to the capacitor through the three-phase inverter. The control of the charge-discharge circuit based on the rotor angle of the three-phase motor to form the charge-discharge current includes: Based on the rotor angle of the three-phase motor, the on-off state of the switching device in the three-phase inverter connected to the capacitor connection phase is controlled to control the charge and discharge circuit to alternately form a charging current and a discharging current, and the charging current and the discharging current flow in opposite directions through the power battery.

[0006] As an optional manner, controlling the on / off state of a switching device in the three-phase inverter to which the capacitor-connected phase is connected based on the rotor angle of the three-phase motor includes: Obtaining a target direct-axis current of the three-phase motor; determining a target current signal for the capacitor-connected phase based on the target direct-axis current and the rotor angle; determining a control signal of a switching device connected to the capacitor-connected phase based on a target current signal of the capacitor-connected phase and a current acquisition signal of 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.

[0007] As an optional manner, obtaining the target direct-axis current of the three-phase motor 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 direct-axis current of the three-phase motor is determined according to the charge-discharge amplitude and the charge-discharge frequency.

[0008] As an optional manner, determining the target current signal of the capacitor-connected phase based on the target direct-axis current and the rotor angle includes: Based on the target direct-axis current and the rotor angle, obtaining the current in a stationary coordinate system through an inverse Park transform; Based on the current in the stationary coordinate system, a target current signal of the capacitor connection phase is obtained through Clark inverse transformation.

[0009] As an optional manner, determining the control signal of the switching device connected to the capacitor-connected phase based on the target current signal of the capacitor-connected phase and the current acquisition signal of the capacitor-connected phase includes: Performing a proportional integral calculation based on a difference between the target current signal of the capacitor-connected phase and the current acquisition signal 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.

[0010] As an optional manner, before controlling the on / off state of a switching device in the three-phase inverter connected to the capacitor-connected phase based on the rotor angle of the three-phase motor, the method further includes: The quadrature-axis current of the three-phase motor is controlled to be zero, and the rotor angle of the three-phase motor is adjusted to be within a preset angle range, wherein the angle range is determined based on the pulse heating requirement of the power battery.

[0011] As an optional embodiment, a pre-charging circuit and a main positive circuit connected in parallel with the pre-charging circuit are further provided between the power battery and the capacitor, the pre-charging circuit including a pre-charging relay and a pre-charging resistor, the main positive circuit including a main positive relay, and after controlling the current on the charging and discharging circuit based on the rotor angle of the three-phase motor, further comprising: The first relay is controlled to be opened and the second relay is controlled to be closed, and the on-off states of the pre-charge relay and the main positive relay are controlled according to the output power requirement of the power battery.

[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 based on the rotor angle of the three-phase motor, so as 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 to use any one phase of the inductor winding of the three-phase motor as the battery connection phase on the basis of the original system including the power battery, capacitor, inductor winding of the three-phase motor and the three-phase inverter, and to add a first relay connecting the battery connection phase and the power battery, and to add a second relay arranged 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 three-phase motor and the three-phase inverter can form a charge and 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 rotor angle of the three-phase motor can be combined to control the charge and discharge circuit to form a charge and discharge current, so that the power battery and the capacitor can be charged and discharged by AC through the charge and discharge circuit to The power battery is heated; it can be understood that the present application can ensure the formation of a charge and discharge circuit between the power battery and the capacitor only by adding a relay switch, so that the AC current can flow repeatedly between the power battery and the capacitor, and the charge and discharge current formed on the charge and discharge circuit is controlled based on the rotor angle of the three-phase motor, which can improve the current controllability, so that the power battery and the capacitor can be charged and discharged alternately more accurately and effectively, 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 improve the heating effect and reduce the heating cost.

[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 main positive relay, K2 is the pre-charge relay, K2 is connected in series with the pre-charge resistor R1, and is used to control the on-off and pre-charge 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 charge and discharge 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 : Controlling the charge-discharge circuit to generate a charge-discharge current based on the rotor angle of the three-phase motor to heat the power battery.

[0035] Among them, a three-phase motor refers to an electric motor with three inductor windings. 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 the battery connection phase to connect the power battery, and the U-phase and W-phase inductor windings can be used as the capacitor connection phase to connect the capacitor through the three-phase inverter.

[0036] It can be understood that the three-phase inverter is used to perform current inversion to form a charging and discharging current as an alternating current, and the rotor angle refers to the real-time position information of the motor rotor, which can be obtained through a sensor or an observer.

[0037] It is worth noting that a first relay is provided between the capacitor connection phase and the power battery, and a second relay is provided between the capacitor connection phase and the three-phase inverter. Therefore, in the heating mode, the first relay can be controlled to close and the second relay to open. Figure 1 As shown, the first relay and the second relay are relays K3 and K4 for controlling the on / off of the charge and discharge circuit. The first relay K3 is used to be arranged between the battery connection phase and the positive terminal of the power battery, and the second relay K4 is used to be arranged between the capacitor 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 a pre-charging circuit and a main positive circuit in parallel with the pre-charging circuit, and the negative terminal is connected to the negative terminal of the power battery. The pre-charging circuit includes a pre-charging relay K2 and a pre-charging resistor R1, and the main positive circuit includes a main positive relay K1. Among them, relays K1 to K4 can all be implemented by electromagnetic relays or solid-state relays to establish a current path between the power battery and the capacitor.

[0038] like Figure 3As shown, the application is based on the original system including the power battery, the capacitor, the inductive winding of the three-phase motor and the three-phase inverter. The inductive winding of any phase of the three-phase motor is used as the battery connection phase. The first relay connecting the battery connection phase and the power battery is added. The 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 opened, the three-phase motor and the three-phase inverter can form a charging and discharging circuit. The charging and discharging circuit includes the inductive winding of the three-phase motor, the three-phase inverter, the power battery and the capacitor. The charging and discharging circuit can be controlled by the rotor angle of the three-phase motor to form a charging and discharging current. The power battery and the capacitor can be charged and discharged through the charging and discharging circuit to heat the power battery. It can be understood that the application only needs to add a relay switch to ensure the formation of the charging and discharging circuit between the power battery and the capacitor. The alternating current can flow between the power battery and the capacitor. The charging and discharging current formed on the charging and discharging circuit based on the rotor angle of the three-phase motor can improve the controllability of the current. The power battery and the capacitor can alternately charge and discharge more accurately and effectively. The power battery itself can be used to generate heat to heat the power battery. Compared with the traditional scheme relying on the external heating element such as the PTC heater, the application does not need to make structural changes to the three-phase motor and does not need to additionally add an independent heating circuit. The heating effect can be improved and the heating cost can be reduced.

[0039] In some embodiments, the other two-phase inductive windings of the three-phase motor except the battery connection phase are respectively used as the capacitor connection phase. Each capacitor connection phase is connected with the capacitor through the three-phase inverter. The charging and discharging current of the charging and discharging circuit is controlled based on the rotor angle of the three-phase motor. The control method includes: based on the rotor angle of the three-phase motor, the on-off state of the switching device in the three-phase inverter connected with the capacitor connection phase is controlled to control the charging and discharging circuit to alternately form the charging current and the discharging current. The directions of the charging current and the discharging current flowing through the power battery are opposite.

[0040] The above process can realize the energy storage and release management of the inductive winding of the three-phase motor by adjusting the on-off state of the switching device to control the charging and discharging circuit to alternately form the charging current and the discharging current. It can be understood that when the discharging current needs to be formed, the inductive winding of the capacitor connection phase enters the energy storage state by setting the on-off control signal corresponding to the target duty ratio. The magnetic field energy stored in the inductor is used to transfer energy to the capacitor after being regulated by the three-phase inverter. At this time, the current flows out of the power battery to form a boost circuit. When the charging current needs to be switched, the inductive winding is switched to the energy release state by adjusting the on-off control signal corresponding to the target duty ratio. The released energy and the electric energy stored in the capacitor are jointly transmitted to the power battery in the reverse direction through the three-phase inverter to form a buck circuit.

[0041] refer to Figure 4 and Figure 5 , Figure 4 In the power battery heating control method provided in the embodiment of the present application, the current flow diagram of the power battery discharge is as follows: Figure 5 In the power battery heating control method provided in the embodiment of the present application, the current flow diagram of the power battery charging: It can be understood that in the heating control scenario of the present application, the Boost boost circuit is reflected in the process of the power battery discharging to the capacitor. Figure 4 As shown, during the power battery discharge stage, current flows out from the positive electrode of the power battery, flows through the loop to the battery-connected phase (such as L2) in the three-phase motor, and flows through the capacitor-connected phase (such as L1 and L3), controlling the on-off state of the switching devices in the three-phase inverter connected to the capacitor-connected phase, so that the inductor (L1, L3) of the three-phase motor enters the energy storage state. The charge and discharge circuit is equivalent to a boost circuit: part of the energy released by the power battery is stored through the inductor, and the other part directly charges the capacitor C1, thereby increasing the voltage between the power battery and the capacitor and completing the energy transfer of the forward current.

[0042] In contrast, the Buck step-down circuit corresponds to the stage where the capacitor charges the power battery. Figure 5 As shown in the figure, during the battery charging phase, current flows from the positive electrode of the capacitor, is regulated by the three-phase inverter, flows to the capacitor-connected phases (such as L1 and L3), and then flows through the battery-connected phase (such as L2) back to the positive electrode of the battery. At this time, the switching devices in the three-phase inverter connected to the capacitor-connected phase are controlled to release energy in the inductors (L1 and L3). The charge-discharge circuit is equivalent to a buck circuit: the energy stored in the capacitor and the energy released by the inductor are combined to charge the battery, achieving reverse current energy recovery.

[0043] It is worth noting that since the rotor angle will change the magnetic coupling state of the inductor windings of each phase of the three-phase motor, thereby affecting the equivalent impedance and current carrying capacity of the inductor windings of different capacitor-connected phases, for example, the change in the rotor angle may cause the inductance value of a certain capacitor-connected phase to increase and the other phase to decrease, thereby changing the energy storage / release efficiency of the two. Therefore, during the charging and discharging current switching process, the present application needs to control the on-off of the switching device according to the rotor angle, adjust the on-off rhythm of the switching of different capacitor-connected phases, and ensure that even if the inductor winding can still maintain a stable switching direction of the charging current and the discharging current, a periodically alternating sinusoidal current is formed, and continuous Joule heat is generated through energy conversion inside the power battery to achieve heating.

[0044] 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 6As shown, in some embodiments, based on the rotor angle of the three-phase motor, the on-off state of the switching device in the three-phase inverter connected to the capacitor-connected phase is controlled, including: obtaining the target direct-axis current of the three-phase motor; determining the target current signal of the capacitor-connected phase based on the target direct-axis current and the rotor angle; determining the control signal of the switching device connected to the capacitor-connected phase based on the target current signal of the capacitor-connected phase and the current acquisition signal of the capacitor-connected phase; and controlling the on-off state of the switching device connected to the capacitor-connected phase based on the control signal.

[0045] Among them, the target direct-axis current refers to the reference current component used to generate a magnetic field in motor control, which can be determined by adjusting the quadrature-axis current to zero and combining it with the pulse heating requirement. The target current signal refers to the phase current setting value that the capacitor-connected phase needs to reach. 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 phase target current signal and the current acquisition signal, adjustments can be made to adjust the on-off state of the switching devices in the three-phase inverter to form a charging and discharging current.

[0046] 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.

[0047] 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.

[0048] In some embodiments, obtaining the target direct-axis current of the three-phase motor includes: determining the charge and discharge amplitude and charge and discharge frequency of the battery connection phase when performing sinusoidal AC charge and discharge based on the pulse heating requirements of the power battery; and determining the target direct-axis current of the three-phase motor according to the charge and discharge amplitude and charge and discharge frequency.

[0049] 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.

[0050] It can be understood that after determining the charge and discharge amplitude and charge and discharge frequency, the value of the target direct-axis current can be derived through the inverse operation of the coordinate transformation. Since the direct-axis current needs to be equivalent to the sinusoidal current of the battery connection phase after the Park inverse transformation and the Clark inverse transformation, the amplitude of the target direct-axis current has a fixed proportional relationship with the charge and discharge amplitude, and the charge and discharge frequency can be matched by controlling the dynamic change rate of the direct-axis current.

[0051] In some embodiments, based on the target direct-axis current and the rotor angle, the target current signal of the capacitor-connected phase is determined, including: based on the target direct-axis current and the rotor angle, obtaining the current in a stationary coordinate system through a Park inverse transform; based on the current in the stationary coordinate system, obtaining the target current signal of the capacitor-connected phase through a Clark inverse transform.

[0052] The Park inverse transform converts the current in a rotating coordinate system to the current in a stationary coordinate system. This can be achieved using a coordinate transformation matrix, which combines the target direct-axis current with the rotor angle to generate the current components in the stationary coordinate system. The Clark inverse transform converts the current in the stationary coordinate system to the phase current. This can be achieved using a three-phase to two-phase coordinate transformation matrix, which decomposes the stationary coordinate system current into the target current values ​​of the two capacitor-connected phases, thereby achieving phase current control.

[0053] It can be understood that after determining the target direct-axis current and rotor angle, the direct-axis current is converted into a current component in a stationary coordinate system through a coordinate transformation algorithm, and then the current target values ​​of the two capacitor-connected phases are obtained. By real-time acquisition of the actual current signal of the capacitor-connected phase, the deviation between the target value and the actual value is input into the proportional-integral controller, and the target duty cycle signal for controlling the on and off of the switching devices in the three-phase inverter is calculated. By adjusting the switching frequency and duty cycle of the switching devices in the three-phase inverter, AC charging and discharging between the power battery and the capacitor is realized.

[0054] It is worth noting that the Park inverse transform is to convert the target direct axis current ( ) is converted into the two-phase current of the stationary coordinate system (α-β axis) ( 、 ), whose transformation matrix can contain the sine and cosine functions of the rotor angle θ. This process associates the direct axis current with the spatial magnetic field direction of the motor winding through the rotor angle, ensuring that the current vector is always consistent with the magnetic field direction. The subsequent Clark inverse transform converts the stationary coordinate system 、 Converted into phase current in the three-phase coordinate system, since one phase of the three-phase motor is already used as the battery-connected phase, only the target current values ​​of the other two phases (capacitor-connected phases) need to be calculated. For example, when the battery-connected phase is V phase, the target current signals of phase U and phase W can be obtained through transformation, and both satisfy Iu+Iw=-Iv (Iv is the battery-connected phase current), thus complying with Kirchhoff's current law. Furthermore, through the above two-level coordinate transformation, the abstract direct-axis current command can be converted into a target current signal of the capacitor-connected phase that can be directly controlled, providing a specific basis for subsequent current closed-loop control.

[0055] In some embodiments, based on the target current signal of the capacitor-connected phase and the current acquisition signal of the capacitor-connected phase, the control signal of the switching device connected to the capacitor-connected phase is determined, including: performing a proportional integral calculation based on the difference between the target current signal of the capacitor-connected phase and the current acquisition signal to obtain a target duty cycle signal; controlling the switching device in the three-phase inverter connected to the battery-connected phase to disconnect, and determining the control signal of the switching device in the three-phase inverter connected to the capacitor-connected phase according to the target duty cycle signal.

[0056] Among them, proportional-integral calculation refers to adjusting the error signal through the combination of proportional and integral links, which can be specifically implemented by a proportional-integral controller. 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 control signal is used to modulate the ratio of the on-time and off-time of the switching device to adjust the phase current of the capacitor connection phase.

[0057] It can be understood that when the current difference 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.

[0058] In some embodiments, before controlling the on-off state of the switching device in the three-phase inverter to which the capacitor-connected phase is connected based on the rotor angle of the three-phase motor, it also includes: controlling the cross-axis current of the three-phase motor to be zero, and adjusting the rotor angle of the three-phase motor to a preset angle range, wherein the angle range is determined based on the pulse heating requirement of the power battery.

[0059] Among them, zero quadrature-axis current means that during the three-phase motor control process, the quadrature-axis current component is set to zero. This can be achieved by adjusting the current closed-loop control parameters of the motor controller, thereby simplifying the current control logic and focusing on the regulation of the direct-axis current.

[0060] It can be understood that 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. During the charge and discharge process, the motor needs to be stationary, that is, the motor has no torque output. When the motor is stationary, energy is only transferred between the battery and the capacitor. The torque output by the motor is mainly determined by the quadrature-axis current of the Q-axis. Therefore, to ensure that the quadrature-axis current is zero, it is only necessary to control the direct-axis current of the D-axis.

[0061] In some embodiments, corresponding Figure 6 The specific process of determining the target direct-axis current of a three-phase motor using the Park / Clark inverse transformation is as follows: According to the Park inverse transformation formula (1) and Clark inverse transformation formula (2), the V phase current as the battery connection phase and the target direct axis current are derived. And the relationship between the rotor angle, When , the relationship is shown in Formula 3 and Formula 4: in, is the cosine, sine, 、 、 are the phase currents of the three-phase inductance windings of the motor, 、 are the currents in the stationary two-phase coordinate system, 、 are the quadrature and direct axis currents in the rotating coordinate system, is the rotor angle, “°” is the degree symbol, " is the square root symbol, ” is the matrix symbol; According to the above formulas 1 to 4, it can be deduced that to control the V phase sinusoidal AC charge and discharge as the battery connection phase, the target direct axis current As shown in Formula 5: in, is the AC charge and discharge amplitude, is the AC charge and discharge frequency, π is the mathematical constant representing pi, and t is the time variable.

[0062] Furthermore, if Figure 6 As shown, the control process of phase current control can be as follows: First, calculate the target direct-axis current using Equation 5 , and obtain the rotor angle Then, the U and W phase current target values ​​can be calculated by performing Park inverse transformation and Clark inverse transformation according to formulas 1 to 4, and then the target values ​​of the U and W phase currents can be calculated by Figure 1 The current sensors A1 and A2 obtain the current acquisition signals of the U and W phases; further, the dual PID current loop controller can calculate the target duty cycle of the IGBT switch tubes corresponding to U and W, and then update the two-phase target duty cycle to the control unit to control Figure 1 The on and off of S1, S3, S4, and S6 in the circuit breaker are controlled, and the upper and lower bridges of the V phase are both in the off state, that is, S2 and S4 are in the off state throughout the process, to ensure that the charging and discharging circuit is turned on in the heating mode, and the current flows repeatedly between the power battery and the capacitor.

[0063] The present application further proposes that before obtaining the rotor angle of the three-phase motor, if the rotor angle of the three-phase motor is not within a preset angle range, the rotor angle of the three-phase motor is adjusted to within the angle range, wherein the angle range is determined based on the pulse heating requirements of the three-phase motor.

[0064] Among them, the rotor angle is not within the preset angle range means that the actual mechanical position of the three-phase motor rotor deviates from the preset interval. Specifically, an angle sensor or encoder can be used to detect the rotor angle, and whether it is within the range can be determined by comparing the detected value with the preset range boundary value. Adjusting to within the angle range means changing the mechanical position of the rotor by controlling the drive signal of the three-phase motor. Specifically, a closed-loop control algorithm can be used to generate a drive signal to rotate the rotor to the target angle range. The angle range is determined based on the pulse heating demand, which means that the angle range is dynamically set according to the heating power demand of the power battery, the charging and discharging capacity of the capacitor, and the electrical parameters of the three-phase motor. Specifically, the optimal angle range can be determined by a table lookup method or a real-time calculation method; for example, to ensure that the absolute value of the V-phase current as the battery connection phase is maximized, when θ When ∈[90°,150°], [270°,330°], θ−30°∈[60°,120°], [240°,300°], sin(θ−30°) approaches its peak value at [sin60°,sin90°], so the range of θ can be [90°,150°], [270°,330°].

[0065] 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 pre-charging circuit and a main positive circuit connected in parallel with the pre-charging circuit are provided between the power battery and the capacitor. The pre-charging circuit includes a pre-charging relay and a pre-charging resistor. The main positive circuit includes a main positive relay. After controlling the current in the charging and discharging circuit based on the rotor angle of the three-phase motor, it also includes: controlling the first relay to disconnect and the second relay to close, and controlling the on and off states of the pre-charging relay and the main positive relay according to the output power requirement of the power battery.

[0066] Among them, the pre-charging circuit refers to a current limiting path formed by the pre-charging 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 main positive circuit refers to a low-impedance path formed by direct connection of the main positive 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 pre-charging relay and the main positive relay can realize the current grading management of the capacitor charging process.

[0067] 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 charge and discharge circuit, and the second relay can be closed to activate the capacitor connection phase. At this time, the pre-charge circuit is turned on first, and the pre-charge resistor limits the initial charging current of the capacitor to avoid inrush current impacting the three-phase inverter. Then, when the capacitor voltage reaches the preset threshold, the main positive relay closes to bypass the pre-charge circuit, reducing the conduction loss, so that the AC heating system can dynamically adjust the switching timing of the pre-charge relay and the main positive relay according to the real-time output power demand, such as extending the working time of the pre-charge circuit when the power demand is low, and quickly switching to the main positive circuit when the power demand is high, effectively suppressing the impact of current mutation on circuit elements and improving circuit reliability.

[0068] 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 start pulse heating of the whole vehicle under low temperature conditions; further, the motor controller of the whole vehicle can be used as a heating control device to determine whether the rotor angle of the three-phase motor is within a preset range. If not, the rotor angle of the three-phase motor is controlled to enter the preset range. If so, it switches to the heating mode. The motor controller can have torque mode, speed mode, pulse heating mode, etc. During pulse heating, the motor controller switches to pulse heating mode and operates as follows Figure 6The target current signal control process is to first boost the voltage so that the power battery charges the capacitor. At this time, the current is a positive sinusoidal current, and then reduce the voltage through the control logic Buck so that the capacitor charges the power battery. At this time, the current is a negative sinusoidal current, so that the power battery and the capacitor are AC charged and discharged through the charge and discharge circuit, thereby heating the power battery without adding an independent heating circuit, thereby reducing the heating cost.

[0069] refer to Figure 9 , Figure 9 A schematic block diagram of a heating control device for a power battery provided in an embodiment of the present application; Figure 9 As 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. 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; 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, so as 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 based on the rotor angle of the three-phase motor to form a charge-discharge current to heat the power battery.

[0070] 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 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.

[0071] In some embodiments, the other two-phase inductance windings of the three-phase motor except the battery-connected phase are respectively used as capacitor-connected phases, and each capacitor-connected phase is respectively connected to the capacitor through a three-phase inverter. When the charge-discharge circuit is controlled based on the rotor angle of the three-phase motor to form a charge-discharge current, the current control module 902 is further configured to: based on the rotor angle of the three-phase motor, control the on-off state of the switching device in the three-phase inverter to which the capacitor-connected phase is connected, so as to control the charge-discharge circuit to alternately form a charging current and a discharging current, and the charging current and the discharging current flow through the power battery in opposite directions.

[0072] In some embodiments, when controlling the on-off state of the switching device in the three-phase inverter connected to the capacitor-connected phase based on the rotor angle of the three-phase motor, the current control module 902 is further configured to: obtain the target direct-axis current of the three-phase motor; determine the target current signal of the capacitor-connected phase based on the target direct-axis current and the rotor angle; determine the control signal of the switching device connected to the capacitor-connected phase based on the target current signal of the capacitor-connected phase and the current acquisition signal of the capacitor-connected phase; and control the on-off state of the switching device connected to the capacitor-connected phase based on the control signal.

[0073] In some embodiments, when obtaining the target direct-axis current of the three-phase motor, the current control module 902 is further configured to: determine the charge and discharge amplitude and charge and discharge frequency of the battery connection phase when performing sinusoidal AC charging and discharging based on the pulse heating requirements of the power battery; determine the target direct-axis current of the three-phase motor according to the charge and discharge amplitude and charge and discharge frequency.

[0074] In some embodiments, when determining the target current signal of the capacitor-connected phase based on the target direct-axis current and the rotor angle, the current control module 902 is further configured to: obtain the current in the stationary coordinate system through Park inverse transformation based on the target direct-axis current and the rotor angle; and obtain the target current signal of the capacitor-connected phase through Clark inverse transformation based on the current in the stationary coordinate system.

[0075] In some embodiments, when determining the control signal of the switching device connected to the capacitor-connected phase based on the target current signal of the capacitor-connected phase and the current acquisition signal of the capacitor-connected phase, the current control module 902 is further configured to: perform a proportional integral calculation based on the difference between the target current signal of the capacitor-connected phase and the current acquisition signal to obtain a target duty cycle signal; control the switching device in the three-phase inverter connected to the battery-connected phase to disconnect, and determine the control signal of the switching device in the three-phase inverter connected to the capacitor-connected phase according to the target duty cycle signal.

[0076] In some embodiments, before controlling the on-off state of the switching device in the three-phase inverter to which the capacitor-connected phase is connected based on the rotor angle of the three-phase motor, the current control module 902 is further configured to: control the quadrature-axis current of the three-phase motor to be zero, and adjust the rotor angle of the three-phase motor to within a preset angle range, wherein the angle range is determined based on the pulse heating requirement of the power battery.

[0077] In some embodiments, a pre-charging circuit and a main positive circuit connected in parallel with the pre-charging circuit are further provided between the power battery and the capacitor. The pre-charging circuit includes a pre-charging relay and a pre-charging resistor. The main positive circuit includes a main positive relay. After controlling the current in the charging and discharging circuit based on the rotor angle of the three-phase motor, the path control module 901 is further configured to: control the first relay to disconnect and the second relay to close, and control the on and off states of the pre-charging relay and the main positive relay according to the output power requirement of the power battery.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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)).

[0083] 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 and discharge circuit is controlled based on the rotor angle of the three-phase motor to form a charge and discharge current to heat the power battery.

2. The method according to claim 1, characterized in that The other two phase inductance windings of the three-phase motor except the battery-connected phase are respectively used as capacitor-connected phases, and each of the capacitor-connected phases is respectively connected to the capacitor through the three-phase inverter. The charging and discharging circuit is controlled based on the rotor angle of the three-phase motor to form a charging and discharging current, including: Based on the rotor angle of the three-phase motor, the on-off state of the switching device in the three-phase inverter connected to the capacitor connection phase is controlled to control the charge and discharge circuit to alternately form a charging current and a discharging current, and the charging current and the discharging current flow in opposite directions through the power battery.

3. The method according to claim 2, characterized in that The controlling, based on the rotor angle of the three-phase motor, of the on-off state of the switching device in the three-phase inverter to which the capacitor-connected phase is connected comprises: Obtaining a target direct-axis current of the three-phase motor; determining a target current signal for the capacitor-connected phase based on the target direct-axis current and the rotor angle; determining a control signal of a switching device connected to the capacitor-connected phase based on a target current signal of the capacitor-connected phase and a current acquisition signal of 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 obtaining of the target direct-axis current of the three-phase motor 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 direct-axis current of the three-phase motor is determined according to the charge-discharge amplitude and the charge-discharge frequency.

5. The method according to claim 3, characterized in that The determining the target current signal of the capacitor-connected phase based on the target direct-axis current and the rotor angle includes: Based on the target direct-axis current and the rotor angle, obtaining the current in a stationary coordinate system through an inverse Park transform; Based on the current in the stationary coordinate system, a target current signal of the capacitor connection phase is obtained through Clark inverse transformation.

6. The method according to claim 2, characterized in that Before controlling the on / off state of a switch device in the three-phase inverter connected to the capacitor-connected phase based on the rotor angle of the three-phase motor, the method further includes: The quadrature-axis current of the three-phase motor is controlled to be zero, and the rotor angle of the three-phase motor is adjusted to be within a preset angle range, wherein the angle range is determined based on the pulse heating requirement of the power battery.

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 main positive 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 based on the rotor angle of the three-phase motor, so as 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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