Vehicle battery AC heating circuit and its control method

Abstract

This application relates to the field of battery heating technology, providing a vehicle battery AC heating circuit and its control method. The battery AC heating circuit includes: a three-phase inverter circuit, a three-phase drive motor, a switching group, and a power battery pack including at least two sets of power batteries; one end of each phase winding of the three-phase drive motor is connected via the switching group, and the other end is connected to the three-phase inverter circuit; the positive terminal of the power battery is connected to the positive DC bus of the three-phase inverter circuit and one end of any phase winding of the three-phase drive motor, with different windings connected to each power battery; switches are provided between the positive terminal of any power battery and the positive DC bus of the three-phase inverter circuit, and between the positive terminal of any power battery and the three-phase drive motor; the negative terminal of each power battery is connected to the negative DC bus of the three-phase inverter circuit. The vehicle battery AC heating circuit provided in this application can reduce the noise generated during power battery heating and improve heating power.

Description

Technical Field

[0001] This application relates to the field of battery heating technology, specifically to an AC heating circuit for a vehicle battery and its control method. Background Technology

[0002] When electric vehicles are charged in low-temperature environments, the internal materials of the power battery undergo changes, resulting in slower charging or discharging speeds. Therefore, to ensure normal battery operation, the power battery of the electric vehicle needs to be heated. One related technology involves AC heating of the battery. This technology uses a three-phase inverter circuit connected to the power battery, where the motor windings are connected to the battery to cycle through charging and discharging, thereby stimulating AC current in the bus and heating the battery. However, to effectively stimulate bus voltage fluctuations and thus AC current in the battery, the motor winding current oscillation frequency is very high, around 2kHz, a frequency sensitive to human hearing, causing significant acoustic noise. Simultaneously, the DC bus capacitor in the three-phase inverter circuit bypasses and absorbs the high-frequency current generated by the three-phase inverter circuit, reducing the AC current flowing into the battery and resulting in lower battery heating power. Summary of the Invention

[0003] This application aims to at least solve one of the technical problems existing in the related art. To this end, this application proposes an AC heating circuit for a vehicle battery, which can reduce the noise generated during the heating of the power battery and improve the heating power.

[0004] This application also proposes an electric vehicle.

[0005] This application also proposes a method for controlling the AC heating circuit of a vehicle battery.

[0006] This application also proposes a battery AC heating circuit control device for a vehicle.

[0007] This application also proposes a computer-readable storage medium.

[0008] The vehicle battery AC heating circuit according to the first aspect of this application includes:

[0009] Three-phase inverter circuit, three-phase drive motor, on / off switch group and power battery pack including at least two power batteries;

[0010] In the three-phase drive motor, one end of each phase winding is connected by an on / off switch group, and the other end is connected to the three-phase inverter circuit.

[0011] The positive terminal of the power battery is connected to the positive terminal of the DC bus of the three-phase inverter circuit and one end of any phase winding of the three-phase drive motor, and the windings connected to each power battery are different.

[0012] A switch is provided between the positive terminal of any of the power batteries and the positive terminal of the DC bus of the three-phase inverter circuit, and between the positive terminal of any of the power batteries and the three-phase drive motor;

[0013] The negative terminal of each of the power batteries is connected to the negative terminal of the DC bus of the three-phase inverter circuit.

[0014] By connecting one end of each phase winding of the three-phase drive motor with an on / off switch group and the other end with the three-phase inverter circuit, and connecting the positive terminal of the power battery to the positive DC bus of the three-phase inverter circuit, while connecting the positive terminals of different power batteries to different windings of the three-phase drive motor, and by installing switches between the positive terminals of any power battery and the positive DC bus of the three-phase inverter circuit, and between the positive terminals of any power battery and the three-phase drive motor, when power battery heating is required, it is only necessary to disconnect the switches between each power battery and the positive DC bus of the three-phase inverter circuit, open the on / off switch group, and close the switches between each power battery and the three-phase drive motor, allowing alternating current to flow back and forth between the batteries. Since it is not necessary to generate alternating current through high-frequency charging and discharging of the motor windings as in traditional solutions, but instead uses energy exchange between the batteries, the frequency of the alternating current flowing back and forth between the batteries during battery heating can be set to a low frequency of around 50Hz, thereby reducing the noise generated during power battery heating. Meanwhile, during heating, the alternating current flows back and forth between the batteries through the high-voltage end supported by the capacitor of the three-phase inverter circuit, which makes the voltage across the high-voltage end, i.e. the two ends of the bus capacitor of the three-phase inverter circuit, stable. Therefore, the current flowing in and out of the battery is basically not lost, avoiding the bypass absorption of high-frequency current by the capacitor, thereby improving the heating power.

[0015] According to one embodiment of this application, the multiple sets of power batteries include a first power battery and a second power battery, and the on / off switch group includes a first on / off switch.

[0016] A first switch is provided between the positive terminal of the first power battery and the positive terminal of the DC bus of the three-phase inverter circuit, and a second switch is provided between the positive terminal of the first power battery and the first winding of the three-phase drive motor.

[0017] A third switch is provided between the positive terminal of the second power battery and the positive terminal of the DC bus of the three-phase inverter circuit, and a fourth switch is provided between the positive terminal of the second power battery and the second winding of the three-phase drive motor.

[0018] One end of the first on / off switch is connected to the first winding of the three-phase drive motor, and the other end of the first on / off switch is connected to the second and third windings of the three-phase drive motor.

[0019] According to one embodiment of this application, the power battery pack further includes a third power battery, and the on / off switch group further includes a second on / off switch:

[0020] A fifth switch is provided between the positive terminal of the third power battery and the positive terminal of the DC bus of the three-phase inverter circuit, and a sixth switch is provided between the positive terminal of the third power battery and the third winding of the three-phase drive motor.

[0021] One end of the second on / off switch is connected to the second winding of the three-phase drive motor, and the other end of the second on / off switch is connected to the other end of the first on / off switch and the third winding of the three-phase drive motor.

[0022] According to one embodiment of this application, the three-phase inverter circuit includes a capacitor, one end of which is connected to the positive terminal of the DC bus of the three-phase inverter circuit, and the other end of which is connected to the negative terminal of the DC bus of the three-phase inverter circuit.

[0023] When the battery is heated by the AC heating circuit, the voltage on the capacitor is greater than that of each power battery, but less than or equal to the maximum allowable operating voltage of the three-phase inverter circuit.

[0024] According to one embodiment of this application, it further includes a controller connected to the three-phase drive motor;

[0025] The controller is used to control the three-phase current of the three-phase drive motor according to each preset constraint model;

[0026] The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a battery power balance constraint model.

[0027] According to one embodiment of this application, the controller is specifically used for:

[0028] Determining that the vehicle is in motion, the three-phase current used to control the three-phase drive motor is determined based on the first current constraint sub-model in the three-phase current constraint model, the first power constraint sub-model in the battery heating power constraint model, the first torque constraint sub-model in the motor torque constraint model, the first voltage constraint sub-model in the bus voltage constraint model, and the first balance constraint sub-model in the battery charge balance constraint model; or,

[0029] Once the vehicle is confirmed to be in a parked state, the three-phase current for controlling the three-phase drive motor is determined based on the second current constraint sub-model in the three-phase current constraint model, the second power constraint sub-model in the battery heating power constraint model, the second torque constraint sub-model in the motor torque constraint model, the second voltage constraint sub-model in the bus voltage constraint model, and the second balance constraint sub-model in the battery charge balance constraint model.

[0030] According to one embodiment of this application, the controller is specifically used for:

[0031] If the vehicle is in a driving state, and the power battery pack has two battery packs, the three-phase current for controlling the three-phase drive motor is determined according to the first current constraint condition in the first current constraint sub-model, the first power constraint condition in the first power constraint sub-model, the first torque constraint condition in the first torque constraint sub-model, the first voltage constraint condition in the second voltage constraint sub-model, and the first battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0032] When the power battery pack has three battery groups, the three-phase current for controlling the three-phase drive motor is determined based on the second current constraint condition in the first current constraint sub-model, the second power constraint condition in the first power constraint sub-model, the second torque constraint condition in the first torque constraint sub-model, the second voltage constraint condition in the first voltage constraint sub-model, and the second battery charge balance constraint condition in the first battery charge balance constraint sub-model.

[0033] According to one embodiment of this application, the controller is specifically used for:

[0034] If the vehicle is in a parked state, and the power battery pack has two battery packs, the three-phase current for controlling the three-phase drive motor is determined according to the third current constraint condition in the second current constraint sub-model, the third power constraint condition in the second power constraint sub-model, the third torque constraint condition in the second torque constraint sub-model, the third voltage constraint condition in the second voltage constraint sub-model, and the third battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0035] When the power battery pack has three battery groups, the three-phase current for controlling the three-phase drive motor is determined according to the fourth current constraint condition in the second current constraint sub-model, the fourth power constraint condition in the second power constraint sub-model, the fourth torque constraint condition in the second torque constraint sub-model, the fourth voltage constraint condition in the second voltage constraint sub-model, and the fourth battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0036] The electric vehicle according to the second aspect of this application includes the battery AC heating circuit of the vehicle described in any of the above embodiments.

[0037] The vehicle battery AC heating circuit control method according to the third aspect of this application, applied to the controller in the vehicle battery AC heating circuit according to the above embodiment, includes:

[0038] The three-phase current of the three-phase drive motor is controlled according to each preset constraint model;

[0039] The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a battery power balance constraint model.

[0040] A battery AC heating circuit control device for a vehicle according to a fourth aspect embodiment of this application includes:

[0041] The circuit control module is used to control the three-phase current of the three-phase drive motor according to each preset constraint model;

[0042] The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a battery power balance constraint model.

[0043] A computer-readable storage medium according to a sixth aspect of this application stores a computer program thereon, which, when executed by a processor, implements the battery AC heating circuit control method for a vehicle as described in any of the above embodiments.

[0044] The above-described one or more technical solutions in the embodiments of this application have at least one of the following technical effects:

[0045] By connecting one end of each phase winding of the three-phase drive motor with an on / off switch group and the other end with the three-phase inverter circuit, and connecting the positive terminal of the power battery to the positive DC bus of the three-phase inverter circuit, while connecting the positive terminals of different power batteries to different windings of the three-phase drive motor, and by installing switches between the positive terminals of any power battery and the positive DC bus of the three-phase inverter circuit, and between the positive terminals of any power battery and the three-phase drive motor, when power battery heating is required, it is only necessary to disconnect the switches between each power battery and the positive DC bus of the three-phase inverter circuit, open the on / off switch group, and close the switches between each power battery and the three-phase drive motor, allowing alternating current to flow back and forth between the batteries. Since it is not necessary to generate alternating current through high-frequency charging and discharging of the motor windings as in traditional solutions, but instead uses energy exchange between the batteries, the frequency of the alternating current flowing back and forth between the batteries during battery heating can be set to a low frequency of around 50Hz, thereby reducing the noise generated during power battery heating. Meanwhile, during heating, the alternating current flows back and forth between the batteries through the high-voltage end supported by the capacitor of the three-phase inverter circuit, which makes the voltage of the high-voltage end, i.e. the capacitor of the three-phase inverter circuit, stable. Therefore, the current flowing in and out of the battery is basically not lost, avoiding the capacitor from bypassing and absorbing the high-frequency current, thereby improving the heating power. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the AC heating circuit for a vehicle battery in related technologies;

[0048] Figure 2 This is a schematic diagram of the structure of the vehicle battery AC heating circuit provided in the embodiments of this application;

[0049] Figure 3 This is a schematic diagram of the battery AC heating circuit including two sets of power batteries in an embodiment of this application;

[0050] Figure 4 This is a schematic diagram of the equivalent circuit structure of the battery AC heating circuit provided in the embodiments of this application;

[0051] Figure 5 This is a schematic diagram of the battery AC heating circuit including three sets of power batteries in an embodiment of this application;

[0052] Figure 6This is a schematic flowchart of the vehicle battery AC heating circuit control method provided in the embodiments of this application;

[0053] Figure 7 This is a schematic diagram of the structure of the vehicle battery AC heating circuit control device provided in the embodiments of this application. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0055] The following will provide a detailed description and explanation of the vehicle battery AC heating circuit and its control method provided in this application through several specific embodiments.

[0056] When electric vehicles are charged in low-temperature environments, the charging speed slows down due to changes in the internal material properties of the power battery. Therefore, to achieve fast charging in low-temperature environments, the power battery of the electric vehicle needs to be heated. Existing heating methods typically use multiple external PTC automotive heaters that are switched to heat the coolant, thereby heating the power battery. However, this indirect heating method requires heat to be transferred to the battery through the coolant and external battery structure, resulting in a significant amount of heat not being effectively transferred to the battery, leading to a slow temperature rise and low heating efficiency. Therefore, related technologies, such as... Figure 1 As shown, this method uses a three-phase inverter circuit connected to the power battery via motor windings for charging and discharging cycles to generate AC current on the bus, thereby heating the power battery. However, to effectively generate AC current within the battery by inducing bus voltage fluctuations, the motor winding current oscillation frequency is very high, around 2kHz, a frequency sensitive to the human ear, resulting in significant acoustic noise. Simultaneously, the DC bus capacitor Cdc has a bypass absorption effect on the high-frequency current generated by the three-phase inverter circuit, reducing the AC current flowing into the battery and resulting in lower battery heating power.

[0057] Therefore, in one embodiment, such as Figure 2 As shown, a battery AC heating circuit for a vehicle is provided, comprising:

[0058] 1. Three-phase inverter circuit; 2. Three-phase drive motor; 3. On / off switch group; and 4. Power battery pack including at least two power batteries.

[0059] One end of each phase winding in the three-phase drive motor 2 is connected by a switch group 3, and the other end is connected to the three-phase inverter circuit 1.

[0060] The positive terminal of the power battery is connected to the positive terminal of the DC bus of the three-phase inverter circuit 1 and one end of any phase winding of the three-phase drive motor 2, and the windings connected to each power battery are different.

[0061] A switch is provided between the positive terminal of any of the power batteries and the positive terminal of the DC bus of the three-phase inverter circuit 1, and between the positive terminal of any of the power batteries and the three-phase drive motor 2.

[0062] The negative terminal of each of the power batteries is connected to the negative terminal of the DC bus of the three-phase inverter circuit 1.

[0063] In one embodiment, the three-phase inverter circuit 1 includes multiple half-bridges and a capacitor Cdc. Each half-bridge includes an upper arm and a lower arm. One end of the capacitor Cdc is connected to the upper arm of each half-bridge to be connected to the positive terminal of the DC bus of the three-phase inverter circuit 1, and the other end is connected to the lower arm of each half-bridge to be connected to the negative terminal of the DC bus of the three-phase inverter circuit 1. Each upper arm and each lower arm includes a switch.

[0064] For example, the first upper bridge switch Q1, the second upper bridge switch Q3, and the third upper bridge switch Q5 form three upper bridge arms. One end of each of these switches is connected to the positive terminal of each power battery in the power battery pack 1. The first lower bridge switch Q2, the second lower bridge switch Q4, and the third lower bridge switch Q6 form three lower bridge arms. One end of the first lower bridge switch Q2 is connected to the other end of the first upper bridge switch Q1, one end of the second lower bridge switch Q4 is connected to the other end of the second upper bridge switch Q3, and one end of the third lower bridge switch Q6 is connected to the other end of the third upper bridge switch Q5. The other ends of these switches are connected to the negative terminal of each power battery in the power battery pack 1.

[0065] The three-phase drive motor 2 has three windings: a first winding, a second winding, and a third winding. These windings are connected in a star configuration via a set of on / off switches. Specifically, the three terminals of the first, second, and third windings are connected to the other ends of the first upper bridge switch Q1, the second upper bridge switch Q3, and the third upper bridge switch Q5, respectively. The other ends of the first, second, and third windings are connected via a set of on / off switches 3, forming a neutral point when each switch in the set is closed. The on / off switches can be relays.

[0066] In one embodiment, such as Figure 3As shown, if the power battery pack 4 only includes the first power battery U1 and the first power battery U2, a switch is provided between the positive terminal of each power battery and the positive terminal of the DC bus of the three-phase inverter circuit 1, and a switch is also provided between the positive terminal of each power battery and the three-phase drive motor. This allows the power battery to be connected to the positive terminal of the three-phase inverter circuit or to the winding of the three-phase drive motor 2 by means of the switches. Each switch can be a relay. Figure 2 As shown in Figure 3, a first switch K1 is provided between the first power battery U1 and the positive terminal of the DC bus of the three-phase inverter circuit 1, and a second switch K2 is provided between the first power battery U1 and the three-phase drive motor; a third switch K3 is provided between the second power battery U2 and the positive terminal of the DC bus of the three-phase inverter circuit 1, and a fourth switch K4 is provided between the second power battery U2 and the three-phase drive motor.

[0067] like Figure 3 As shown, if the power battery pack 4 only includes the first power battery U1 and the first power battery U2, then the on / off switch group 4 can only include the first on / off switch kc. One end of the first on / off switch kc is connected to the first winding of the three-phase drive motor 1, and the other end of the first on / off switch kc is connected to the second winding and the third winding of the three-phase drive motor 1.

[0068] When there is no need to heat the power battery pack, the switch between each power battery and the positive terminal of the DC bus of the three-phase inverter circuit 1 is closed, the switches in the on / off switch group 3 are closed, and the switch between each power battery and the three-phase drive motor 2 is open.

[0069] When heating of the power battery pack is required, the switch between each power battery and the positive terminal of the DC bus of the three-phase inverter circuit 1 is disconnected, all on / off switches in the on / off switch group 3 are open, and the switch between each power battery and the three-phase drive motor 2 is closed. For example... Figure 3 The battery AC heating circuit shown is configured such that, at this time, the first switch k1, the third switch k3, and the first on / off switch kc are open, while the second switch k2 and the fourth switch k4 are closed. The equivalent circuit of the battery AC heating circuit at this time is as follows: Figure 4 As shown, the two half-bridges formed by the second upper bridge switch Q3 and the second lower bridge switch Q4, and the third upper bridge switch Q5 and the third lower bridge switch Q6, can be combined into an equivalent half-bridge circuit under heating conditions. Figure 4The diagram shows the half-bridge circuit formed by Q35 and Q46. It can be seen that, at this point, the first power battery U1 and the first power battery U2, together with the motor windings of the three-phase drive motor, the half-bridge circuit, and the capacitor Cdc, constitute two bidirectional boost circuits. Therefore, during heating, one boost circuit discharges the battery, and the other boost circuit charges the battery, continuously switching the charging and discharging direction. The current flows back and forth between the two power batteries through the high-voltage terminal supported by Cdc. Therefore, the frequency of this current flow can theoretically be arbitrarily low. Considering factors such as battery charging and discharging safety limitations at low temperatures, the frequency can still be as low as approximately 50Hz.

[0070] By connecting one end of each phase winding of the three-phase drive motor with an on / off switch group and the other end with the three-phase inverter circuit, and connecting the positive terminal of the power battery to the positive DC bus of the three-phase inverter circuit, while connecting the positive terminals of different power batteries to different windings of the three-phase drive motor, and by installing switches between the positive terminals of any power battery and the positive DC bus of the three-phase inverter circuit, and between the positive terminals of any power battery and the three-phase drive motor, when power battery heating is required, it is only necessary to disconnect the switches between each power battery and the positive DC bus of the three-phase inverter circuit, open the on / off switch group, and close the switches between each power battery and the three-phase drive motor, allowing alternating current to flow back and forth between the batteries. Since it is not necessary to generate alternating current through high-frequency charging and discharging of the motor windings as in traditional solutions, but instead uses energy exchange between the batteries, the frequency of the alternating current flowing back and forth between the batteries during battery heating can be set to a low frequency of around 50Hz, thereby reducing the noise generated during power battery heating. Meanwhile, during heating, the alternating current flows back and forth between the batteries through the high-voltage end supported by the capacitor of the three-phase inverter circuit, which makes the voltage of the high-voltage end, i.e. the capacitor of the three-phase inverter circuit, stable. Therefore, the current flowing in and out of the battery is basically not lost, avoiding the capacitor from bypassing and absorbing the high-frequency current, thereby improving the heating power.

[0071] In one embodiment, such as Figure 5 As shown, in addition to the first battery U1 and the second battery U2, the power battery pack 1 may also include a third power battery U3, that is, the power battery pack 1 includes three power batteries. Correspondingly, the on / off switch group 3 includes a first on / off switch kc1 and a second on / off switch kc2.

[0072] A fifth switch k5 is provided between the positive terminal of the third power battery U3 and the positive terminal of the DC bus of the three-phase inverter circuit 1, and a sixth switch k6 is provided between the positive terminal of the third power battery U3 and the third winding of the three-phase drive motor 2.

[0073] One end of the second on / off switch kc2 is connected to the second winding of the three-phase drive motor 2, and the other end of the second on / off switch kc2 is connected to the other end of the first on / off switch kc1 and the third winding of the three-phase drive motor 2. One end of the first on / off switch kc1 is connected to the first winding. At this time, the three motor windings of the three-phase drive motor 2 can be divided as follows: Figure 5 The three independent windings shown can be restored to a star connection through the first on / off switch kc1 and the second on / off switch kc2.

[0074] Similar to the principle of the two sets of power batteries, when heating of the power battery pack is not required, the first switch k1, the third switch k3, the fifth switch k5, and the first on / off switches kc1 and kc2 are closed, while the second switch k2, the fourth switch k4, and the sixth switch k6 are open. When heating of the power battery pack is required, the first switch k1, the third switch k3, the fifth switch k5, and the first on / off switches kc1 and kc2 are open, while the second switch k2, the fourth switch k4, and the sixth switch k6 are closed. During heating, the current can still flow back and forth between the three power batteries via the high-voltage terminal supported by the Cdc, thereby reducing noise generated during battery heating and increasing heating power.

[0075] In one embodiment, when the battery AC heating circuit heats the battery, the voltage on the capacitor of the three-phase inverter circuit 1 is greater than that of each power battery, and less than or equal to the maximum allowable operating voltage of the three-phase inverter circuit 1.

[0076] By setting the voltage on the capacitor of the three-phase inverter circuit to be greater than the voltage of each power battery while not exceeding the maximum allowable operating voltage of the three-phase inverter circuit during battery heating in the AC heating circuit, the current of the three-phase drive motor is kept under control.

[0077] In one embodiment, a controller (not shown) connected to the three-phase drive motor 2 is also included;

[0078] The controller is used to control the three-phase current of the three-phase drive motor 2 according to each preset constraint model;

[0079] The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a battery power balance constraint model.

[0080] To ensure that the three-phase current generated by the three-phase drive motor meets the requirements for motor torque output, battery heating, bus voltage maintenance, and battery charge balance, in one embodiment, a three-phase current constraint model can be pre-constructed based on the motor current frequency, AC component amplitude, and DC bias current of the three-phase windings in the three-phase drive motor; a battery heating power constraint model can be constructed based on the phase current flowing through the power battery and the battery internal resistance; a motor torque constraint model can be constructed based on the phase current flowing through the power battery; a bus voltage constraint model can be constructed based on the sum of the phase currents; and a charge balance constraint model can be constructed based on the charge difference between the power batteries.

[0081] After constructing the three-phase current constraint model, battery heating power constraint model, motor torque constraint model, bus voltage constraint model, and power balance constraint model, the three-phase current during heating can be determined through the constraints of these models, and the three-phase drive motor can be controlled to perform heating using the three-phase current.

[0082] By using a set of preset constraint models consisting of a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a power balance constraint model, the three-phase current required by the three-phase drive motor is determined. This ensures that the three-phase current during heating meets the requirements of each preset constraint model, thereby making the three-phase current generated by the three-phase drive motor controllable and improving safety.

[0083] To ensure that the three-phase current generated by the three-phase drive motor better meets actual requirements, in one embodiment, the controller is specifically used for:

[0084] Determining that the vehicle is in motion, the three-phase current used to control the three-phase drive motor is determined based on the first current constraint sub-model in the three-phase current constraint model, the first power constraint sub-model in the battery heating power constraint model, the first torque constraint sub-model in the motor torque constraint model, the first voltage constraint sub-model in the bus voltage constraint model, and the first battery charge balance constraint sub-model in the charge balance battery charge balance constraint model; or,

[0085] Once the vehicle is determined to be in a parked state, the three-phase current for controlling the three-phase drive motor is determined based on the second current constraint sub-model in the three-phase current constraint model, the second power constraint sub-model in the battery heating power constraint model, the second torque constraint sub-model in the motor torque constraint model, the second voltage constraint sub-model in the bus voltage constraint model, and the second battery power balance constraint sub-model in the battery power balance constraint model.

[0086] In one embodiment, the vehicle's states include a driving state and a parked state. Since the required motor drive torque differs between these two states, different sub-models need to be established for each state to ensure the three-phase current generated by the three-phase drive motor better meets actual requirements. Specifically, for the driving state, a first current constraint sub-model is established based on the current frequency, AC component amplitude, DC bias current of each phase winding, and the phase of the current relative to the rotor angle of the three-phase drive motor. Secondly, since the three-phase current is slightly DC biased AC current during vehicle operation, a first power constraint sub-model can be established based on the internal resistance of each battery and the current flowing through the battery within one AC cycle, and a first torque constraint sub-model can be established based on the current flowing through the battery. In the driving state, the rise and fall of the bus voltage of the battery AC heating circuit is determined by the current of each phase; therefore, a first voltage constraint sub-model is established based on the sum of the three-phase currents. Simultaneously, a first battery charge balance constraint sub-model is established based on the difference in charge levels of each power battery. Furthermore, from the perspective of maximizing the balance of winding heating, the first battery charge balance constraint sub-model can also be established based on the effective values ​​of each phase current.

[0087] After constructing the first current constraint sub-model, the first power constraint sub-model, the first torque constraint sub-model, the first voltage constraint sub-model, and the first battery charge balance constraint sub-model, the three-phase current when the vehicle is in motion and heating is working can be determined through the constraints of the first current constraint sub-model, the first power constraint sub-model, the first torque constraint sub-model, the first voltage constraint model, and the first battery charge balance constraint sub-model, so as to use the three-phase current to control the three-phase drive motor for heating.

[0088] For the parking state, i.e., when the motor is stationary, the vehicle is braked to a stop, and the motor's drive torque requirement is zero, a second current constraint sub-model is established based on the AC oscillation frequency, AC component amplitude, and DC bias current of each phase winding; a second power constraint sub-model is established based on the internal resistance of each battery and the current flowing through the battery; a second torque constraint sub-model is established based on the average torque within the AC current cycle; a second voltage constraint sub-model is established based on the sum of the three-phase currents; and a second battery charge balance constraint sub-model is established based on the difference in charge of each power battery.

[0089] After constructing the second current constraint sub-model, the second power constraint sub-model, the second torque constraint sub-model, the second voltage constraint sub-model, and the second battery charge balance constraint sub-model, the three-phase current when the vehicle is in a parked state and heating is working can be determined through the constraints of the second current constraint sub-model, the second power constraint sub-model, the second torque constraint sub-model, the second voltage constraint model, and the second battery charge balance constraint sub-model, so as to use the three-phase current to control the three-phase drive motor for heating.

[0090] By taking into account different vehicle states, sub-models corresponding to different states are obtained from each preset constraint model to determine the three-phase current that the three-phase drive motor needs to generate under different states, so that the three-phase current during heating can meet the constraint requirements under different states.

[0091] In one embodiment, the controller is specifically used for:

[0092] If the vehicle is in a driving state, and the power battery pack has two battery packs, the three-phase current for controlling the three-phase drive motor is determined according to the first current constraint condition in the first current constraint sub-model, the first power constraint condition in the first power constraint sub-model, the first torque constraint condition in the first torque constraint sub-model, the first voltage constraint condition in the second voltage constraint sub-model, and the first battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0093] When the power battery pack has three battery groups, the three-phase current for controlling the three-phase drive motor is determined based on the second current constraint condition in the first current constraint sub-model, the second power constraint condition in the first power constraint sub-model, the second torque constraint condition in the first torque constraint sub-model, the second voltage constraint condition in the first voltage constraint sub-model, and the second battery charge balance constraint condition in the first battery charge balance constraint sub-model.

[0094] In one embodiment, if the vehicle is in motion and the power battery pack consists of two battery groups (i.e., the vehicle is in motion and the power battery pack includes only the first power battery U1 and the second power battery U2), then the first current constraint condition in the first current constraint sub-model is:

[0095]

[0096] Among them, f e I is the current frequency of the three-phase drive motor. s For the amplitude of the AC component, I A，dc I B，dc I C，dc I represents the DC bias current of the three-phase windings A, B, and C of the three-phase drive motor. A，dc I B，dc I C，dc Less than I s , This refers to the phase of the current relative to the rotor angle of the three-phase drive motor, or the cumulative angle difference. Specifically, if the three-phase drive motor is a permanent magnet synchronous motor, then... This represents the phase of the current relative to the rotor angle of the three-phase drive motor; if the three-phase drive motor is an asynchronous motor, then... It is the cumulative angle difference between the current and the rotor angle of the three-phase drive motor.

[0097] Since the three-phase current is slightly DC biased AC current when the vehicle is running, the battery heating power is determined by the current flowing through the power battery within one AC cycle. Therefore, the first power constraint condition in the first power constraint sub-model is:

[0098]

[0099] Where P is the battery heating power, R U1 R is the internal resistance of the power battery U1. U2 The internal resistance of the power battery U2 is given, and the integral length is one AC cycle.

[0100] The first torque constraint condition in the first torque constraint sub-model is:

[0101] T = f(I) A ,I B ,I C )≈g(I s ,φ).

[0102] Among them, the functions f and g are determined according to the design of the three-phase drive motor.

[0103] When the vehicle is running, the rise and fall of the bus voltage is determined by the "common-mode current," that is, by I. com =I A +I B +I C Therefore, by implementing closed-loop control of the bus voltage, the constraint on the sum of the three-phase currents is obtained, i.e., the first voltage constraint condition is:

[0104] I com =I A +I B +I C =I A,dc +I B,dc +I C,dc .

[0105] When the vehicle is determined to be in motion, based on the difference in battery charge between the first power battery U1 and the second power battery U2, the net current requirement flowing from battery U1 to battery U2 is obtained through closed-loop control calculations. That is, the first battery charge balance constraint condition in the second battery charge balance constraint sub-model is:

[0106] I U1→U2 =I A,dc -(I B,dc +I C,dc ).

[0107] Considering that the above conditions may not be sufficient to determine the DC bias of each of the three phases, there exists an adjustable degree of freedom to impose additional requirements. Preferably, from the perspective of maximizing the balance of winding heating, when the vehicle is in motion and the power battery pack consists only of the first battery pack U1 and the second battery pack U2, it is desirable that the effective values ​​of the B and C phase currents generated by the second and third windings are equal. Therefore, the following constraints can be added:

[0108] I B,dc =I C,dc .

[0109] Based on the aforementioned first current constraint, first power constraint, first torque constraint, first voltage constraint, and first battery charge balance constraint, it can be concluded that {I} s ,φ,I A,dc I B,dc I C,dc The five parameters correspond exactly to the five constraints, thus uniquely determining the three-phase current of the battery AC heating circuit when the vehicle is in motion and the power battery pack has two battery packs.

[0110] Similarly, if the power battery pack has three battery packs, namely, the first battery pack U1, the second battery pack U2, and the third battery pack U3, then the second current constraint condition in the first current constraint sub-model under vehicle driving conditions is:

[0111]

[0112] The second power constraint condition in the first power constraint sub-model is:

[0113]

[0114] The second torque constraint condition in the first torque constraint sub-model is:

[0115] T = f(I) A ,I B ,I C )≈g(I s ,φ).

[0116] The second voltage constraint condition in the first voltage constraint sub-model is:

[0117] I com =I A +I B +I C =I A,dc +I B,dc +I C,dc .

[0118] The second battery charge balance constraint condition in the first battery charge balance constraint sub-model is:

[0119] I U1→U2 =I A,dc -I B,dc ;I U2→U3 =I B,dc -I C,dc .

[0120] At this point, with the vehicle in a parked state and the power battery pack consisting of two battery packs, the three-phase current during heating can be uniquely determined based on the aforementioned second current constraint, second power constraint, second torque constraint, second voltage constraint, and second battery charge balance constraint.

[0121] In one embodiment, the controller is specifically used for:

[0122] When the vehicle is in a parked state, and the power battery pack has two battery packs, the three-phase current for controlling the three-phase drive motor is determined based on the third current constraint condition in the second current constraint sub-model, the third power constraint condition in the second power constraint sub-model, the first torque constraint condition in the second torque constraint sub-model, the third voltage constraint condition in the second voltage constraint sub-model, and the third battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0123] When the power battery pack has three battery groups, the three-phase current for controlling the three-phase drive motor is determined according to the fourth current constraint condition in the second current constraint sub-model, the fourth power constraint condition in the second power constraint sub-model, the fourth torque constraint condition in the second torque constraint sub-model, the fourth voltage constraint condition in the second voltage constraint sub-model, and the fourth battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0124] If the vehicle is parked and the battery pack consists of two battery groups (i.e., the motor's drive torque requirement is zero and the battery pack only includes the first battery U1 and the second battery U2), and the three-phase current is determined as if the vehicle were in motion, then the resulting three-phase current would be DC when the motor is stationary. This means that current would flow constantly from one battery to the other, causing an imbalance in the battery's charge level. Furthermore, for commonly used permanent magnet synchronous motors, the current command obtained in this situation would vary with the rotor angle; at certain angles, the current command would be very small and ineffective in heating the battery. Therefore, in such cases, the three-phase current needs to be varied by alternating current with a slight DC bias, and the frequency of the alternating current should be set to a certain given value. That is, constraints are constructed based on AC oscillation combined with a slight DC bias, with the AC oscillation frequency being f. ac This can be a relatively low frequency, such as 50Hz; or it can be the inverter switching frequency, in which case the AC component in the current is the fundamental frequency of the current ripple. Secondly, the phases of the BC phase currents are opposite to those of phase A, and their amplitudes are half that of phase A. The advantage of this design is that it ensures I... com =I A +I B +I C Since the voltage is DC, the voltage across the high-voltage side Cdc capacitor will not fluctuate, avoiding interference with other electrical appliances on the bus and reducing the risk of bus voltage overvoltage.

[0125] Specifically, the third current constraint condition is:

[0126]

[0127] The third power constraint condition is:

[0128]

[0129] The third torque constraint condition changes from requiring the torque to meet the vehicle's driving requirements at any given time to a constraint on the average torque over the AC current cycle, i.e.:

[0130]

[0131] Since the average torque is almost entirely related to the DC bias, although there is a certain frequency of fluctuating torque, the frequency is relatively high, and the mechanical clearance and elasticity of the transmission shaft system absorb the vibration, as well as the body itself absorbs the vibration, so it will not cause obvious body vibration problems.

[0132] The third voltage constraint condition is:

[0133] I com =I A +IB +I C =I A,dc +I B,dc +I C,dc .

[0134] The third battery charge balance constraint condition is:

[0135] I U1→U2 =I A,dc -(I B,dc +I C,dc ).

[0136] At this point, when the vehicle is in motion and the power battery pack has three battery packs, the three-phase current that the three-phase drive motor needs to output can be determined based on the third current constraint, the third power constraint, the third torque constraint, the third voltage constraint, and the third battery charge balance constraint.

[0137] Similarly, if the power battery pack has three battery packs, namely the first battery pack U1, the second battery pack U2, and the third battery pack U3, then the fourth current constraint condition in the second current constraint sub-model when the vehicle is parked is:

[0138]

[0139] The fourth power constraint condition in the second power constraint sub-model is:

[0140]

[0141] The fourth torque constraint condition in the second torque constraint sub-model is:

[0142]

[0143] The fourth voltage constraint condition in the second voltage constraint sub-model is:

[0144] I com =I A +I B +I C =I A,dc +I B,dc +I C,dc .

[0145] The fourth battery charge balance constraint condition in the second battery charge balance constraint sub-model is:

[0146] I U1→U2 =I A,dc -I B,dc ;I U2→U3 =I B,dc -I C,dc .

[0147] After constructing the fourth current constraint, fourth power constraint, fourth torque constraint, fourth voltage constraint, and fourth battery charge balance constraint, the three-phase current to be output by the three-phase drive motor can be determined when the vehicle is parked and the power battery pack has three battery packs.

[0148] In one embodiment, an electric vehicle is also provided, including a battery AC heating circuit for a vehicle as described in any of the above embodiments.

[0149] The following describes the control method for the AC heating circuit of a vehicle battery provided in this application. The control method for the AC heating circuit of a vehicle battery described below is applied to the controller in the AC heating circuit of the vehicle battery described above.

[0150] In one embodiment, such as Figure 6 As shown, a method for controlling the AC heating circuit of a vehicle battery is provided, which is applied to the controller in the AC heating circuit of the vehicle battery as described in the embodiment.

[0151] The method includes:

[0152] Step 101: Control the three-phase current of the three-phase drive motor according to each preset constraint model;

[0153] The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a power balance constraint model.

[0154] In one embodiment, controlling the three-phase current of the three-phase drive motor according to each preset constraint model includes:

[0155] Determining that the vehicle is in motion, the three-phase current used to control the three-phase drive motor is determined based on the first current constraint sub-model in the three-phase current constraint model, the first power constraint sub-model in the battery heating power constraint model, the first torque constraint sub-model in the motor torque constraint model, the first voltage constraint sub-model in the bus voltage constraint model, and the first battery charge balance constraint sub-model in the charge balance constraint model; or,

[0156] Once the vehicle is confirmed to be in a parked state, the three-phase current for controlling the three-phase drive motor is determined based on the second current constraint sub-model in the three-phase current constraint model, the second power constraint sub-model in the battery heating power constraint model, the second torque constraint sub-model in the motor torque constraint model, the second voltage constraint sub-model in the bus voltage constraint model, and the second battery charge balance constraint sub-model in the charge balance constraint model.

[0157] In one embodiment, after determining that the vehicle is in a driving state, the three-phase current for controlling the three-phase drive motor is determined based on the first current constraint sub-model in the three-phase current constraint model, the first power constraint sub-model in the battery heating power constraint model, the first torque constraint sub-model in the motor torque constraint model, the first voltage constraint sub-model in the bus voltage constraint model, and the first battery charge balance constraint sub-model in the charge balance constraint model. This includes:

[0158] If the vehicle is in a driving state, and the power battery pack has two battery packs, the three-phase current for controlling the three-phase drive motor is determined according to the first current constraint condition in the first current constraint sub-model, the first power constraint condition in the first power constraint sub-model, the first torque constraint condition in the first torque constraint sub-model, the first voltage constraint condition in the second voltage constraint sub-model, and the first battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0159] When the power battery pack has three battery groups, the three-phase current for controlling the three-phase drive motor is determined based on the second current constraint condition in the first current constraint sub-model, the second power constraint condition in the first power constraint sub-model, the second torque constraint condition in the first torque constraint sub-model, the second voltage constraint condition in the first voltage constraint sub-model, and the second battery charge balance constraint condition in the first battery charge balance constraint sub-model.

[0160] In one embodiment, determining that the vehicle is in a parked state, the three-phase current for controlling the three-phase drive motor is determined based on the second current constraint sub-model in the three-phase current constraint model, the second power constraint sub-model in the battery heating power constraint model, the second torque constraint sub-model in the motor torque constraint model, the second voltage constraint sub-model in the bus voltage constraint model, and the second battery charge balance constraint sub-model in the charge balance constraint model, including:

[0161] If the vehicle is in a parked state, and the power battery pack has two battery packs, the three-phase current for controlling the three-phase drive motor is determined according to the third current constraint condition in the second current constraint sub-model, the third power constraint condition in the second power constraint sub-model, the third torque constraint condition in the second torque constraint sub-model, the third voltage constraint condition in the second voltage constraint sub-model, and the third battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0162] When the power battery pack has three battery groups, the three-phase current for controlling the three-phase drive motor is determined according to the fourth current constraint condition in the second current constraint sub-model, the fourth power constraint condition in the second power constraint sub-model, the fourth torque constraint condition in the second torque constraint sub-model, the fourth voltage constraint condition in the second voltage constraint sub-model, and the fourth battery charge balance constraint condition in the second battery charge balance constraint sub-model.

[0163] The following describes the vehicle battery AC heating circuit control device provided in this application. The vehicle battery AC heating circuit control device described below can be referred to in correspondence with the vehicle battery AC heating circuit control method described above.

[0164] In one embodiment, such as Figure 7 As shown, a battery AC heating circuit control device for a vehicle is provided, comprising:

[0165] The circuit control module 210 is used to control the three-phase current of the three-phase drive motor according to each preset constraint model;

[0166] The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a power balance constraint model.

[0167] On the other hand, this application embodiment also provides a storage medium, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the vehicle battery AC heating circuit control method provided in the above embodiments.

[0168] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the 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 the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

Claims

1. An alternating current heating circuit for a battery of a vehicle, characterized in that, The application relates to a three-phase inverter circuit, a three-phase driving motor, a group of on-off switches and a group of power batteries including at least two power batteries. One end of each phase winding in the three-phase driving motor is connected through the group of on-off switches, and the other end is connected with the three-phase inverter circuit. The positive pole of each power battery is connected with the positive pole of the DC bus of the three-phase inverter circuit and one end of any phase winding in the three-phase driving motor, and the windings connected by each power battery are different. A switch is arranged between the positive pole of any power battery and the positive pole of the DC bus of the three-phase inverter circuit and between the positive pole of any power battery and the three-phase driving motor. The negative pole of each power battery is connected with the negative pole of the DC bus of the three-phase inverter circuit. The group of on-off switches includes a first on-off switch, one end of which is connected with the first winding of the three-phase driving motor, and the other end of which is connected with the second winding and the third winding of the three-phase driving motor. When heating of the group of power batteries is needed, the switch between each power battery and the positive pole of the DC bus of the three-phase inverter circuit is turned off, each on-off switch in the group of on-off switches is turned off, and the switch between each power battery and the three-phase driving motor is turned on. The group of power batteries includes a first power battery and a second power battery.

2. The battery AC heating circuit of a vehicle according to claim 1, characterized by, A first switch is arranged between the positive pole of the first power battery and the positive pole of the DC bus of the three-phase inverter circuit, and a second switch is arranged between the positive pole of the first power battery and the first winding of the three-phase driving motor. A third switch is arranged between the positive pole of the second power battery and the positive pole of the DC bus of the three-phase inverter circuit, and a fourth switch is arranged between the positive pole of the second power battery and the second winding of the three-phase driving motor. The group of power batteries further includes a third power battery, and the group of on-off switches further includes a second on-off switch.

3. The battery AC heating circuit of a vehicle according to claim 2, characterized by, A fifth switch is arranged between the positive pole of the third power battery and the positive pole of the DC bus of the three-phase inverter circuit, and a sixth switch is arranged between the positive pole of the third power battery and the third winding of the three-phase driving motor. One end of the second on-off switch is connected with the second winding of the three-phase driving motor, and the other end of the second on-off switch is connected with the other end of the first on-off switch and the third winding of the three-phase driving motor. The three-phase inverter circuit includes a capacitor, one end of which is connected with the positive pole of the DC bus of the three-phase inverter circuit, and the other end of which is connected with the negative pole of the DC bus of the three-phase inverter circuit.

4. The battery AC heating circuit of a vehicle according to claim 1, characterized by, When the battery AC heating circuit performs battery heating, the voltage on the capacitor is greater than that of each power battery and less than or equal to the maximum working voltage allowed by the three-phase inverter circuit. The application further includes a controller connected with the three-phase driving motor.

5. The battery AC heating circuit of a vehicle according to any one of claims 1 to 4, characterized by, The controller is used for controlling the three-phase current of the three-phase driving motor according to each preset constraint model. Each preset constraint model includes a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model and a battery power balance constraint model. The controller is specifically used for 6. The battery AC heating circuit of a vehicle according to claim 5, characterized by, ​ determining the three-phase current for controlling the three-phase driving motor according to a first current constraint sub-model in a three-phase current constraint model, a first power constraint sub-model in a battery heating power constraint model, a first torque constraint sub-model in a motor torque constraint model, a first voltage constraint sub-model in a bus voltage constraint model, and a first balance constraint sub-model in an electric quantity balance constraint model when the vehicle is in the driving state; or determining the three-phase current for controlling the three-phase driving motor according to a second current constraint sub-model in a three-phase current constraint model, a second power constraint sub-model in a battery heating power constraint model, a second torque constraint sub-model in a motor torque constraint model, a second voltage constraint sub-model in a bus voltage constraint model, and a second balance constraint sub-model in an electric quantity balance constraint model when the vehicle is in the parking state.

7. The battery AC heating circuit of a vehicle according to claim 6, characterized by, The controller is specifically configured to: determining the three-phase current for controlling the three-phase driving motor according to a first current constraint condition in the first current constraint sub-model, a first power constraint condition in the first power constraint sub-model, a first torque constraint condition in the first torque constraint sub-model, a first voltage constraint condition in the second voltage constraint sub-model, and a first balance constraint condition in the second balance constraint sub-model when the vehicle is in the driving state and the number of the battery groups in the power battery group is two; determining the three-phase current for controlling the three-phase driving motor according to a second current constraint condition in the first current constraint sub-model, a second power constraint condition in the first power constraint sub-model, a second torque constraint condition in the first torque constraint sub-model, a second voltage constraint condition in the first voltage constraint sub-model, and a second balance constraint condition in the first balance constraint sub-model when the number of the battery groups in the power battery group is three.

8. The battery AC heating circuit of a vehicle according to claim 6 or 7, characterized by, The controller is specifically configured to: determining the three-phase current for controlling the three-phase driving motor according to a third current constraint condition in the second current constraint sub-model, a third power constraint condition in the second power constraint sub-model, a third torque constraint condition in the second torque constraint sub-model, a third voltage constraint condition in the second voltage constraint sub-model, and a third balance constraint condition in the second balance constraint sub-model when the vehicle is in the parking state and the number of the battery groups in the power battery group is two; determining the three-phase current for controlling the three-phase driving motor according to a fourth current constraint condition in the second current constraint sub-model, a fourth power constraint condition in the second power constraint sub-model, a fourth torque constraint condition in the second torque constraint sub-model, a fourth voltage constraint condition in the second voltage constraint sub-model, and a fourth balance constraint condition in the second balance constraint sub-model when the number of the battery groups in the power battery group is three.

9. An electric vehicle, characterized by The battery AC heating circuit of the vehicle according to any one of claims 1-7.

10. A battery AC heating circuit control method of a vehicle, characterized by, The controller applied to the battery AC heating circuit of the vehicle according to any one of claims 5-8; The method comprises: controlling the three-phase current of the three-phase driving motor according to each preset constraint model; The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a power balance constraint model. The preset constraint models include a three-phase current constraint model, a battery heating power constraint model, a motor torque constraint model, a bus voltage constraint model, and a power balance constraint model.

Images