A method for reusing motor stator windings and controlling battery heating

Abstract

The present invention discloses a motor stator winding reuse and battery heating control method, wherein the motor stator three-phase winding is used in parallel to form a motor stator winding combined inductance, which is combined with an inverter and a battery pack to form a battery internal heating system, so that the B1 battery pack and the B2 battery pack are mutually charged and discharged through the motor winding combined inductance, generating Joule heat to internally heat the battery pack; the present invention is suitable for internal preheating of lithium batteries at low temperatures, making full use of existing hardware resources of electric vehicles, and controlling the on and off of two sets of inverter full-control devices to generate self-heating current inside the lithium battery, and generating heat by mutual charging and discharging between batteries, thereby improving the thermoelectric conversion efficiency. The present invention is suitable for electric vehicles with multiple motors, and can meet the different needs of dual motors, multiple motor windings, and open winding motors.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery heating for new energy vehicles, and in particular relates to a method for controlling stator winding reuse and battery heating of a motor. Background Art

[0002] In recent years, as the public's attention to environmental issues has continued to increase, new energy vehicles have received policy support due to their low-carbon and environmentally friendly advantages. Major domestic automobile companies have also made efforts in new energy vehicles, including increasing research and development efforts in core electric vehicle batteries.

[0003] Lithium batteries have become the first choice for driving electric vehicles due to their advantages such as high energy density and long cycle life. However, the internal resistance of the battery increases sharply under low temperature conditions, and the output power and available energy drop significantly. In addition, the battery is difficult to charge at low temperatures, and lithium dendrites are easily generated during charging, causing safety hazards, which greatly limits the use of lithium-ion batteries in cold environments.

[0004] At present, the effective method to improve the performance of lithium-ion batteries in low temperature environment is to preheat the power battery. Common methods include wide-line metal film heating, electric heating film heating and other external heating methods. The battery needs to be heated through contact conduction, air convection, liquid heat transfer and other ways, which requires a large space and high cost. The Chinese patent (CN 113506934 A) proposes a lithium battery heating system and heating method, which controls the on and off of four fully controlled devices to generate self-heating current inside the lithium battery, thereby adjusting the size and frequency of the charge and discharge current. However, the system needs to design a new device for a specific vehicle model. Each component in the device is newly added, which not only increases the production cost, but also occupies the internal space of the vehicle and increases the weight of the vehicle body, which is not conducive to vehicle-mounted applications.

[0005] Therefore, there is an urgent need for a method to realize battery heating control based on the existing hardware resources of electric vehicles. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a motor stator winding reuse and battery heating control method utilizing the existing hardware resources of an electric vehicle to solve the problem of reduced performance and slow heating speed of lithium-ion batteries in electric vehicles under low temperature environments.

[0007] To achieve the above-mentioned purpose, the present invention is designed to reuse the stator winding of a motor and control the battery heating. The special feature of the method is that the three-phase stator winding of the motor is connected in parallel to form a motor stator winding combined inductance, which is combined with an inverter (motor controller) and a battery pack to form a battery heating system, so that the B1 battery pack and the B2 battery pack are charged and discharged with each other through the motor winding combined inductance, generating Joule heat to heat the battery pack internally; wherein,

[0008] The battery heating system includes a first inverter, a second inverter, a detection unit, a control unit and a motor stator winding combined inductor, the B1 battery pack is connected in parallel with the first inverter; the B2 battery pack is connected in parallel with the second inverter; the negative electrode of the B1 battery pack is connected to the negative electrode of the B2 battery pack; the midpoints of the bridge arms of the first inverter and the second inverter are respectively connected to the motor winding combined inductor;

[0009] The control unit detects the surface temperature of the battery pack and the current flowing through the motor winding combined inductance through the detection unit, and controls the on and off of the fully controlled devices in the first inverter and the second inverter according to the detection results, so that a self-heating current is generated inside the lithium battery, and the size and frequency of the charging and discharging current are adjusted.

[0010] Preferably, the motor stator winding combined inductance is composed of single motor stator windings connected in parallel, one end of the single motor stator winding is connected to the midpoint of the bridge arm of the first inverter, and the other end is connected to the midpoint of the bridge arm of the second inverter, the left and right tubes of the upper / lower bridge arm of the first inverter are synchronously turned on to short-circuit the circuit at one end, and the left and right tubes of the upper / lower bridge arm of the second inverter are synchronously turned on to short-circuit the circuit at the other end, and by controlling the left and right tubes of the upper / lower bridge arm of the first inverter and the second inverter to be synchronously turned on, a parallel connection between the stator windings connected to the midpoint of the bridge arm is achieved to form the motor stator winding combined inductance.

[0011] Preferably, the motor stator winding combined inductance is composed of dual motor stator windings connected in series and parallel, the first inverter and the second inverter are respectively connected to the stator winding of one motor in the dual motors, and the parallel connection between the stator windings connected to the midpoint of the bridge arm is realized by controlling the left and right tubes of the upper / lower bridge arms of the first inverter and the second inverter to be synchronously turned on, and the two stator winding combined inductors respectively connected to the inverters are connected to the midpoints through the stator winding Y connection, forming a motor stator winding combined inductance connected in series with each other and connected between the midpoints of the two inverter combined bridge arms.

[0012] Preferably, the motor stator winding combined inductance is formed by connecting multiple motor stator windings in parallel, the first inverter and the second inverter are formed by connecting a plurality of inverter groups in parallel, each inverter group has the same structure, and the midpoint of each inverter bridge arm in the first inverter and the second inverter is respectively connected to the motor winding combined inductance;

[0013] Each inverter group in the first inverter and the second inverter is respectively connected to a stator winding of a motor, and the parallel connection between the stator windings connected to the midpoint of the bridge arm is realized by controlling the left and right tubes of the upper / lower bridge arm of the inverter to be synchronously turned on; the stator windings connected to each inverter group in the first inverter are connected in parallel to form a first parallel inductance, and the stator windings connected to each inverter group in the second inverter are connected in parallel through a Y-connected midpoint to form a second parallel inductance, and the first parallel inductance and the second parallel inductance are connected in series through the Y-connected midpoint to form a motor stator winding combined inductance.

[0014] Preferably, a contactor KM is provided between the external inductors respectively connected to the two inverters, and the control end of the contactor KM is connected to the control unit, and the control unit controls the closing / opening of the contactor KM contacts to realize the closing / opening of the electrical connection between the external inductor and the inverter combined bridge arm.

[0015] Preferably, during the battery heating process, the charge state balance control between the B1 battery pack and the B2 battery pack is simultaneously implemented, and the balance control is achieved by adjusting the ratio T1 / T2 of the charging cycle T1 to the discharging cycle T2. The specific process is as follows:

[0016] When the expected value of the stator winding combination inductance current is the same, measure the average value of the battery terminal voltage of the B1 battery group and the B2 battery group in their respective discharge / charge cycles, calculated as U1 and U2, and then distribute the ratio of the B1 battery charging cycle T1 to the B1 battery discharging cycle T2 according to T2 / T1=U1 / U2.

[0017] Preferably, both the B1 battery pack and the B2 battery pack are connected to a load. During the battery heating process, when the B1 battery pack and the B2 battery pack carry the load and implement the battery internal heating program, the ratio T1 / T2 of the charging cycle T1 of the B1 battery pack to the discharging cycle T2 of the B1 battery pack in the battery heating system is determined according to the power difference △P or the current difference △I of the loads carried by the B1 battery pack and the B2 battery pack during the heating process; if the load current carried by the B1 battery pack is greater than the load current carried by the B2 battery pack by △I, and the expected value of the inductor current flowing through is I, then T2 / T1=I / (I+△I); conversely, if the load current carried by the B1 battery pack is less than the load current carried by the B2 battery pack by △I, then T2 / T1=I / (I-△I).

[0018] Preferably, the ratio of the B1 battery pack charging cycle T1 to the B1 battery pack discharging cycle T2 is allocated according to T2 / T1=k1*U1 / U2+k2*I / (I+△I) or T2 / T1=k1*U1 / U2+k2*I / (I-△I), wherein U1 and U2 are the average values ​​of the battery terminal voltages of the B1 battery pack and the B2 battery pack in their respective discharge cycles, and K1 and K2 are preset or real-time adjustable coefficients.

[0019] The present invention also provides a lithium battery heating system, which implements the above-mentioned motor stator winding reuse and battery heating control method.

[0020] The present invention further proposes an electric vehicle, comprising a motor, a B1 battery pack, a B2 battery pack and a lithium-ion battery heating system, wherein the lithium-ion battery heating system executes the above-mentioned motor stator winding reuse and battery heating control method.

[0021] Compared with the prior art, the beneficial effects of the present invention include:

[0022] (1) The present invention is suitable for internal preheating of lithium-ion batteries at low temperatures, making full use of existing hardware resources of electric vehicles, reusing motor stator windings and inverters, and connecting the three-phase stator windings of the motor in parallel to form a motor stator winding combined inductance, which is combined with the inverter and battery pack to form a battery heating system. The battery pack is charged and discharged through the motor stator winding combined inductance, thereby generating Joule heat to heat the battery pack internally.

[0023] (2) The present invention controls the on and off of multiple groups of inverter full-control devices to generate self-heating current inside the lithium battery, and generates heat through the method of mutual charging and discharging between batteries, thereby improving the thermoelectric conversion efficiency.

[0024] (3) The present invention is applicable to electric vehicles with multiple motors and can meet the different requirements of dual motors, multiple motor windings, and open-winding motors.

[0025] (4) The present invention aims at the situation that lithium batteries are usually connected to loads in actual applications, and adjusts the magnitude and frequency of the charge and discharge current to achieve charge state balance between the battery packs B1 and B2. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of the battery heating system used in the first embodiment of the present invention.

[0027] Figure 2 Schematic diagram of the structure of a battery heating system used in the second embodiment of the present invention.

[0028] Figure 3 Schematic diagram of the structure of a battery heating system used in the third embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The present invention proposes a motor stator winding reuse and battery heating control method, which is applied to electric vehicles. The three-phase stator windings of the motor are connected in parallel to form a motor stator winding combined inductance, which is combined with an inverter (motor controller) and a battery pack to form a battery heating system, so that the B1 battery pack and the B2 battery pack are charged and discharged with each other through the motor winding combined inductance, generating Joule heat to heat the battery pack internally.

[0031] Embodiment 1

[0032] The structure of the lithium battery heating system used in this embodiment is as follows Figure 1 As shown, it includes a B1 battery pack, a B2 battery pack, a first inverter, a second inverter, a detection unit, a control unit and a motor winding combination inductance. The motor stator winding combination inductance L is formed by connecting single motor stator windings in parallel, the left side of the single motor stator winding is connected to the midpoint of the first inverter, and the right side is connected to the midpoint of the second inverter. The left and right tubes of the upper / lower bridge arm of the first inverter are synchronously turned on to short-circuit the left circuit, and the left and right tubes of the upper / lower bridge arm of the second inverter are synchronously turned on to short-circuit the right circuit. By controlling the left and right tubes of the upper / lower bridge arm of the first inverter and the second inverter to be synchronously turned on, the parallel connection between the stator windings connected to the midpoint of the bridge arm is realized to form the motor stator winding combination inductance.

[0033] The B1 battery pack is connected in parallel with the first inverter, which includes fully-controlled devices Q31, Q32, Q33 and fully-controlled devices Q41, Q42, Q43 connected in series. The fully-controlled devices Q31, Q32, Q33 form an upper bridge arm, and the fully-controlled devices Q41, Q42, Q43 form a lower bridge arm. The fully-controlled devices Q31, Q32, Q33 and the fully-controlled devices Q41, Q42, Q43 are power electronic power devices. Each fully-controlled device is provided with a gate, an emitter, and a collector. The gates of the fully-controlled devices Q31, Q32, Q33 and the gates of the fully-controlled devices Q41, Q42, Q43 are all connected to the control unit; the emitters of the fully-controlled devices Q31, Q32, Q33 are connected to the collectors of the fully-controlled devices Q41, Q42, Q43, and the collectors of the fully-controlled devices Q31, Q32, Q33 are connected to the positive electrode of the B1 battery pack; the emitters of the fully-controlled devices Q41, Q42, Q43 are connected to the negative electrode of the B1 battery pack.

[0034] The B2 battery pack is connected in parallel with the second inverter; the second inverter includes fully controlled devices Q11, Q12, Q13 and fully controlled devices Q21, Q22, Q23 connected in series. The fully controlled devices Q11, Q12, Q13 form an upper bridge arm, and the fully controlled devices Q21, Q22, Q23 form a lower bridge arm. The fully-controlled devices Q11, Q12, Q13 and the fully-controlled devices Q21, Q22, Q23 are power electronic power devices. Each fully-controlled device is provided with a gate, an emitter and a collector. The gates of the fully-controlled devices Q11, Q12, Q13 and the gates of the fully-controlled devices Q21, Q22, Q23 are all connected to the control unit; the emitters of the fully-controlled devices Q11, Q12, Q13 are connected to the collectors of Q21, Q22, Q23, and the collectors of the fully-controlled devices Q11, Q12, Q13 are connected to the positive electrode of the B2 battery pack; the emitters of the fully-controlled devices Q21, Q22, Q23 are connected to the negative electrode of the B2 battery pack.

[0035] One end of the motor winding combination inductor L is connected to the connection circuit between the emitter of the fully-controlled devices Q31, Q32, Q33 and the collector of the fully-controlled devices Q41, Q42, Q43; the other end of the motor winding combination inductor is connected to the connection circuit between the emitter of the fully-controlled devices Q11, Q12, Q13 and the collector of the fully-controlled devices Q21, Q22, Q23. The detection unit obtains information such as the battery temperature and the current flowing through the motor winding combination inductor through the temperature sensor and the Hall element, determines whether the battery needs to be heated, and determines whether the battery self-heating current is within the expected range, and sends the judgment information to the control unit; the control unit controls the on and off of the fully-controlled devices of the first inverter and the second inverter according to the judgment result sent by the detection unit.

[0036] The control unit can reuse the central management unit of the system. The central management unit determines whether to start or end heating based on the battery temperature signal and heating criteria, and sends instructions to the control unit. The control unit then communicates with the inverter control board, or the central management unit directly communicates with the inverter control board to control the on and off operation of all controlled devices in the inverter.

[0037] When the method of the present invention is used to heat the battery, after the detection unit detects that the temperature of the B1 battery pack or the B2 battery pack is lower than the battery heating threshold temperature, the control unit confirms that the battery pack needs to be heated. The switch control of the full control device and the flow direction of the current in the circuit during the heating process are described in detail as follows:

[0038] The heating process is divided into an upper half cycle (first stage, second stage) and a lower half cycle (third stage, fourth stage), as shown in Table 1. In the upper half cycle, the self-heating process is performed by the B1 battery pack charging the B2 battery pack; in the lower half cycle, the B2 battery pack charges the B1 battery pack. The upper half cycle and the lower half cycle are performed alternately until the lithium battery heating process is completed.

[0039] Table 1 Switch control of all control devices during heating of the heating system in Example 1

[0040] Phase 1 Phase II Phase 3 Stage 4 Q11, Q12, Q13 Pass Pass Pass Q21, Q22, Q23 Pass Q31, Q32, Q33 Pass Pass Pass Q41, Q42, Q43 Pass

[0041] In the first half cycle, in the first stage, the fully controlled devices Q31, Q32, Q33 of the first inverter are turned on while the fully controlled devices Q41, Q42, Q43 are turned off, and the fully controlled devices Q21, Q22, Q23 of the second inverter are turned on while the fully controlled devices Q11, Q12, Q13 are turned off; the current flows from the positive electrode of the B1 battery pack through the fully controlled devices Q31, Q32, Q33, the motor winding combination inductor, the fully controlled devices Q21, Q22, Q23 to the negative electrode of the battery pack B1. In this stage, the current in the motor winding combination inductor continues to increase, and the B1 battery pack discharges.

[0042] In order to prevent the current from exceeding the maximum current I allowed to flow in the combined inductance of the motor windings MAX , pre-set the maximum allowable value of the motor winding combination inductance current I LH , if the motor winding combination inductance current value I L Increase to the maximum value I LH , then the fully controlled devices Q21, Q22, Q23 of the second inverter are turned off, and the fully controlled devices Q11, Q12, Q13 are turned on, and the heating system enters the second stage. The current in the motor winding combination inductance flows through the fully controlled devices Q11, Q12, Q13, the positive electrode of the B2 battery pack, the negative electrode of the B1 battery pack, and the fully controlled devices Q31, Q32, Q33. Due to the internal resistance of the battery, the current in the motor winding combination inductance continues to decrease, and the B2 battery pack is charged.

[0043] In order to ensure the battery heating speed, the minimum allowable current of the motor winding combination I is pre-set. LL , when the current in the motor winding combination inductance is less than I LL When the motor winding combination inductance current value I L Less than the preset value I LL , the fully controlled devices Q11, Q12, Q13 of the second inverter are turned off and the fully controlled devices Q21, Q22, Q23 are turned on. The heating system is in the first stage, which increases the current value of the motor winding combined inductance L and discharges the B1 battery pack.

[0044] Repeat the full-control devices Q11, Q12, Q13 and the full-control devices Q21, Q22, Q23 on the second inverter to alternately turn on and off, and set the motor winding combined inductance current value I L Maintain within the preset range I LL ,I LH Inside.

[0045] In the second half cycle, the fully controlled devices Q11, Q12, Q13 of the second inverter in the third stage are turned on while the fully controlled devices Q21, Q22, Q23 are turned off, the fully controlled devices Q31, Q32, Q33 of the first inverter are turned off while the fully controlled devices Q41, Q42, Q43 are turned on, and the current flows from the positive electrode of the B2 battery pack through the fully controlled devices Q11, Q12, Q13, the motor winding combination inductor, the fully controlled devices Q41, Q42, Q43 to the negative electrode of the B1 battery pack. In this stage, the current in the motor winding combination inductor continuously decreases until the current polarity changes and then increases, and the B2 battery pack discharges.

[0046] In order to avoid exceeding the maximum current I allowed to flow in the combined inductance of the motor windings MAX , pre-set the maximum allowable current I in the motor winding combination inductance LH , if the current value in the motor winding combination inductance I L Increase to the maximum value I LH , the fully controlled devices Q31, Q32, Q33 of the first inverter are turned on and the fully controlled devices Q41, Q42, Q43 are turned off, and the heating system enters the fourth stage. The current in the motor winding combined inductance flows through the fully controlled devices Q31, Q32, Q33, the positive electrode of the B1 battery pack, the negative electrode of the B2 battery pack, and the fully controlled devices Q11, Q12, Q13. Due to the internal resistance of the battery, the B1 battery pack is charged.

[0047] If the current value in the motor winding combination inductance is I L Less than the preset value I LL , the fully controlled devices Q31, Q32, Q33 of the first inverter are turned off, and the fully controlled devices Q41, Q42, Q43 are turned on, and the heating system enters the third stage, which increases the inductance current value of the motor winding combination and discharges the B2 battery pack.

[0048] In the first and third stages, the current flowing through the motor winding combined inductance increases continuously. In the second and fourth stages, the current flowing through the motor winding combined inductance decreases continuously. When the battery pack temperature rises to the battery heating threshold temperature, the detection unit sends information to make the control unit stop outputting the drive signal, and the electric vehicle starts normally.

[0049] It should also be noted that the control method of the motor winding combination inductor current can be open-loop control or closed-loop control. When the control method is open-loop control, the on and off time of the upper and lower full-control devices connected in series with the charged battery pack is determined by a preset value. When the control method is closed-loop control, the on and off time of the upper and lower full-control devices connected in series with the charged battery pack is controlled by a current hysteresis loop, and the loop width of the current hysteresis loop is determined by a preset value.

[0050] During the heating process, the time distribution of the upper and lower cycles needs to be adjusted to balance the charge state between the B1 battery pack and the B2 battery pack. It is also necessary to adjust the alternating frequency of the upper and lower cycles and the alternating on and off frequency of the upper and lower full-control devices to change the internal heat generation rate of the B1 battery pack and the B2 battery pack.

[0051] The specific process of implementing the charge state balance control between the B1 battery pack and the B2 battery pack during the battery heating process is as follows:

[0052] Embodiment 2

[0053] The structure of the lithium battery heating system used in this embodiment is as follows Figure 2 As shown, it includes a B1 battery pack, a B2 battery pack, a first inverter, a second inverter, a detection unit, a control unit and two motor winding combined inductors. The negative pole of the B1 battery pack is electrically connected to the negative pole of the B2 battery pack, and the B1 battery pack and the B2 battery pack are charged and discharged with each other through the two motor winding combined inductors.

[0054] The B1 battery pack is connected in parallel with the first inverter, which includes fully-controlled devices Q31, Q32, Q33 and fully-controlled devices Q41, Q42, Q43 connected in series. The fully-controlled devices Q31, Q32, Q33 and fully-controlled devices Q41, Q42, Q43 are power electronic power devices, each of which is provided with a gate, an emitter and a collector. The gates of the fully-controlled devices Q31, Q32, Q33 and the gates of the fully-controlled devices Q41, Q42, Q43 are all connected to the control unit; the emitters of the fully-controlled devices Q31, Q32, Q33 are connected to the collectors of the fully-controlled devices Q41, Q42, Q43, and the collectors of the fully-controlled devices Q31, Q32, Q33 are connected to the positive electrode of the B1 battery pack; the emitters of the fully-controlled devices Q41, Q42, Q43 are connected to the negative electrode of the B1 battery pack.

[0055] The B2 battery pack is connected in parallel with the second inverter; the second inverter includes fully-controlled devices Q11, Q12, Q13 and fully-controlled devices Q21, Q22, Q23 connected in series, the fully-controlled devices Q11, Q12, Q13 and fully-controlled devices Q21, Q22, Q23 are power electronic power devices, each of which is provided with a gate, an emitter and a collector, the gates of the fully-controlled devices Q11, Q12, Q13 and the gates of the fully-controlled devices Q21, Q22, Q23 are all connected to the control unit; the emitters of the fully-controlled devices Q11, Q12, Q13 are connected to the collectors of Q21, Q22, Q23, and the collectors of the fully-controlled devices Q11, Q12, Q13 are connected to the positive electrode of the B2 battery pack; the emitters of the fully-controlled devices Q21, Q22, Q23 are connected to the negative electrode of the B2 battery pack.

[0056] The first inverter and the second inverter are respectively connected to a motor stator winding. The parallel connection between the stator windings connected to the midpoint of the bridge arm is realized by controlling the left and right tubes of the upper / lower bridge arms of the first inverter and the second inverter to be synchronously turned on. The two stator winding combined inductors respectively connected to the inverters are connected through the stator winding Y-connected midpoint, forming a motor stator winding combined inductor connected in series with each other and connected across the midpoints of the inverter bridges of the two inverters.

[0057] A contactor KM is provided between the external inductors respectively connected to the two inverters, and the control end of the contactor KM is connected to the control unit. The control unit controls the closing / opening of the contact of the contactor KM to realize the closing / opening of the electrical connection between the motor stator winding combined inductance and the inverter combined bridge arm.

[0058] The detection unit obtains information such as the battery temperature and the current flowing in the motor winding combined inductance through the temperature sensor and the Hall element, determines whether the battery needs to be heated, and determines whether the battery self-heating current is within the expected range, and sends the judgment information to the control unit; the control unit controls the on-off of the first inverter and the second inverter full-control device according to the judgment result sent by the detection unit. When the control unit receives the judgment result sent by the detection unit that the battery needs to be heated, it controls the contact of the contactor KM to close, the electrical connection between the motor stator winding combined inductance and the inverter combined bridge arm to close, and controls the switch of the full-control device in the first inverter and the second inverter to heat the battery. The control unit can reuse the central management unit of the system, and the central management unit determines whether to start or end heating according to the battery temperature signal and the heating criterion, and sends instructions to the control unit, and then the control unit communicates with the inverter control board, or the central management unit directly communicates with the inverter control board to control the on-off work of the full-control device in the inverter. The process of controlling battery heating using the method in this embodiment is the same as that in embodiment 1, and will not be repeated here. When the battery pack temperature rises to the battery heating threshold temperature, the detection unit sends information to the control unit to stop outputting the drive signal, the contacts of the control contactor KM are disconnected, the connection between the motor stator winding combined inductance and the inverter combined bridge arm is disconnected, and the electric vehicle starts normally.

[0059] When the expected value of the stator winding combination inductance current remains unchanged, the average values ​​of the battery terminal voltages of the B1 battery group and the B2 battery group in their respective discharge cycles are measured and recorded as U1 and U2. The ratio of the B1 battery group charging cycle T1 to the B1 battery group discharging cycle T2 is distributed according to T2 / T1=U1 / U2.

[0060] The B1 battery pack and the B2 battery pack may be connected to a load. During the battery heating process, when the B1 battery pack and the B2 battery pack carry a load and implement the battery internal heating program, the ratio T1 / T2 of the B1 battery pack charging cycle T1 to the B1 battery pack discharging cycle T2 of the battery heating system is determined according to the power difference △P or the current difference △I of the load carried by the B1 battery pack and the B2 battery pack during the heating process.

[0061] If the load current carried by the B1 battery pack is greater than the load current carried by the B2 battery pack by △I, and the expected value of the current flowing through the inductor is I, then T2 / T1=I / (I+△I); conversely, if the load current carried by the B1 battery pack is less than the load current carried by the B2 battery pack by △I, then T2 / T1=I / (I-△I);

[0062] The ratio of the B1 battery pack charging cycle T1 to the B1 battery pack discharging cycle T2 is allocated according to T2 / T1=k1*U1 / U2+k2*I / (I+△I) or T2 / T1=k1*U1 / U2+k2*I / (I-△I), where U1 and U2 are the average values ​​of the battery terminal voltages of the B1 battery pack and the B2 battery pack during the discharge cycle, and K1 and K2 are preset or real-time adjustable coefficients.

[0063] Embodiment 3

[0064] The structure of the lithium battery heating system used in this embodiment is as follows Figure 3 As shown, it includes a B1 battery pack, a B2 battery pack, two groups of first inverters, two groups of second inverters, a detection unit, a control unit and four motor winding combined inductors. The negative pole of the B1 battery pack is electrically connected to the negative pole of the B2 battery pack, and the B1 battery pack and the B2 battery pack are charged and discharged with each other through the four motor winding combined inductors.

[0065] In this embodiment, the first inverter and the second inverter are each composed of two groups, and each group is connected to a motor winding combined inductor. Each group of the first inverter includes six fully controlled devices Q311, Q312, Q313, Q411, Q412, Q413 / Q321, Q322, Q323, Q421, Q422, and Q423; wherein the emitters of the fully controlled devices Q311, Q312, Q313 / Q321, Q322, and Q323 are connected to the collectors of Q411, Q412, Q413 / Q421, Q422, and Q423, respectively; The collectors of Q322 and Q323 are connected to the positive electrode of the B1 battery pack, the emitters of the fully-controlled devices Q411, Q412, Q413 / Q421, Q422 and Q423 are connected to the negative electrode of the B1 battery pack, the gates of the fully-controlled devices Q311, Q312, Q313, Q411, Q412, Q413 / Q321, Q322, Q323, Q421, Q422 and Q423 are all connected to the control end of the control unit, and the midpoint of each group of first inverters is connected to a stator winding of a motor.

[0066] The two groups of second inverters also include six fully controlled devices Q111, Q112, Q113, Q211, Q212, Q213 / Q121, Q122, Q123, Q221, Q222, Q223, wherein the emitters of the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123 are connected to the collectors of Q211, Q212, Q213 / Q221, Q222, Q223, and the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123 are connected to the collectors of Q211, Q212, Q213 / Q221, Q222, Q223. 1. The collectors of Q122 and Q123 are connected to the positive electrode of the B2 battery pack, the emitters of the fully-controlled devices Q211, Q212, Q213 / Q221, Q222, and Q223 are connected to the negative electrode of the B2 battery pack, the gates of the fully-controlled devices Q111, Q112, Q113, Q211, Q212, Q213 / Q121, Q122, Q123, Q221, Q222, and Q223 are all connected to the control end of the control unit, and the midpoint of each group of the second inverter is connected to the stator winding of the motor.

[0067] Four motor stator windings are connected in parallel to form the motor stator winding combined inductance in this embodiment. Each inverter group in the first inverter and the second inverter is respectively connected to a motor stator winding, and the parallel connection between the stator windings connected to the midpoint of the bridge arm is realized by controlling the synchronous conduction of the left and right tubes of the upper / lower bridge arms of the inverter; the stator windings connected to each inverter group in the first inverter are connected in parallel to form a first parallel inductance, and the stator windings connected to each inverter group in the second inverter are connected in parallel through a Y-connected midpoint to form a second parallel inductance. The first parallel inductance and the second parallel inductance are connected in series through the Y-connected midpoint to form the motor stator winding combined inductance.

[0068] After the detection unit detects that the temperature of the B1 battery pack or the B2 battery pack is lower than the battery heating threshold temperature, the control unit / central management unit confirms that the battery pack needs to be heated, controls the closure of the contacts of contactors KM1, KM2, and KM3, the closure of the electrical connection between the motor stator winding combined inductance and the inverter combined bridge arm, and realizes switching control of the fully controlled devices in the first inverter and the second inverter through communication with the inverter control board to heat the battery.

[0069] The process of controlling battery heating using the method in this embodiment is as follows:

[0070] The heating process is divided into an upper half cycle (first stage, second stage) and a lower half cycle (third stage, fourth stage), as shown in Table 2. In the upper half cycle, the B1 battery pack charges the B2 battery pack during the self-heating process; in the lower half cycle, the B2 battery pack charges the B1 battery pack. The upper half cycle and the lower half cycle are performed alternately until the lithium battery heating process is completed.

[0071] Table 2 Switch control of all control devices during heating process of heating system in Example 3

[0072] Phase 1 Phase II Phase 3 Stage 4 Q111, Q112, Q113 Pass Pass Pass Q121, Q122, Q123 Pass Pass Pass Q211, Q212, Q213 Pass Q221, Q222, Q223 Pass Q311, Q312, Q313 Pass Pass Pass Q321, Q322, Q323 Pass Pass Pass Q411, Q412, Q413 Pass Q421, Q422, Q423 Pass

[0073] In the first half cycle, in the first stage, the fully controlled devices Q311, Q312, Q313 / Q321, Q322, Q323 of the first inverter are turned on and the fully controlled devices Q411, Q412, Q413 / Q421, Q422, Q423 are turned off, and the fully controlled devices Q211, Q212, Q213 / Q221, Q222, Q223 of the second inverter are turned on and The fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123 are turned off; the current flows from the positive electrode of the B1 battery pack through the fully controlled devices Q311, Q312, Q313 / Q321, Q322, Q323, the motor winding combination inductor, the fully controlled devices Q411, Q412, Q413 / Q421, Q422, Q423 to the negative electrode of the battery pack B1. In this stage, the current in the motor winding combination inductor continues to increase, and the B1 battery pack is discharged.

[0074] Preset the maximum allowable value of the motor winding combination inductance current I LH , if the motor winding combination inductance current value I L Increase to the maximum value I LH , then the fully controlled devices Q211, Q212, Q213 / Q221, Q222, Q223 of the second inverter are turned off, and the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123 are turned on, and the heating system enters the second stage. The current in the motor winding combination inductance flows through the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123, the positive electrode of the B2 battery pack, the negative electrode of the B1 battery pack, and the fully controlled devices Q311, Q312, Q313 / Q321, Q322, Q323. Due to the internal resistance of the battery, the current in the motor winding combination inductance continues to decrease, and the B2 battery pack is charged.

[0075] In order to ensure the battery heating speed, the minimum allowable current of the motor winding combination I is pre-set. LL , when the current in the motor winding combination inductance is less than I LL When the motor winding combination inductance current value I L Less than the preset value I LL , control the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123 of the second inverter to be turned off and at the same time, the fully controlled devices Q211, Q212, Q213 / Q221, Q222, Q223 are turned on. The heating system is in the first stage, which increases the inductance current value of the motor winding combination and discharges the B1 battery pack.

[0076] Repeat the full-control devices Q111, Q112, Q113 / Q121, Q122, Q123 and the full-control devices Q211, Q212, Q213 / Q221, Q222, Q223 on the second inverter to alternately turn on and off, and set the motor winding combined inductance current value I L Maintain within the preset range I LL ,I LH Inside.

[0077] In the second half cycle, the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123 of the second inverter in the third stage are turned on, and the fully controlled devices Q211, Q212, Q213 / Q221, Q222, Q223 are turned off, and the fully controlled devices Q311, Q312, Q313 / Q321, Q322, Q323 of the first inverter are turned off. At this time, the fully controlled devices Q411, Q412, Q413 / Q421, Q422, Q423 are turned on, and the current flows from the positive electrode of the B2 battery pack through the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123, the motor winding combination inductor, the fully controlled devices Q411, Q412, Q413 / Q421, Q422, Q423 to the negative electrode of the B1 battery pack. In this stage, the current in the motor winding combination inductor continues to decrease until the current polarity changes and then increases, and the B2 battery pack is discharged.

[0078] Preset the maximum allowable current I in the motor winding combined inductance LH , if the current value in the motor winding combination inductance I L Increase to the maximum value I LH , the fully controlled devices Q311, Q312, Q313 / Q321, Q322, Q323 of the first inverter are controlled to be turned on and the fully controlled devices Q411, Q412, Q413 / Q421, Q422, Q423 are turned off, and the heating system enters the fourth stage. The current in the motor winding combination inductance flows through the fully controlled devices Q311, Q312, Q313 / Q321, Q322, Q323, the positive electrode of the B1 battery pack, the negative electrode of the B2 battery pack, and the fully controlled devices Q111, Q112, Q113 / Q121, Q122, Q123. Due to the internal resistance of the battery, the B1 battery pack is charged.

[0079] If the current value in the motor winding combination inductance is I L Less than the preset value I LL , the fully controlled devices Q311, Q312, Q313 / Q321, Q322, and Q323 of the first inverter are controlled to be turned off, and the fully controlled devices Q411, Q412, Q413 / Q421, Q422, and Q423 are turned on, and the heating system enters the third stage, increasing the inductance current value of the motor winding combination and discharging the B2 battery pack.

[0080] In the first and third stages, the current flowing through the motor winding combined inductance continues to increase. In the second and fourth stages, the current flowing through the motor winding combined inductance continues to decrease. When the battery pack temperature rises to the battery heating threshold temperature, the detection unit sends information to the control unit to stop outputting the drive signal, control the contacts of contactors KM1, KM2, and KM3 to disconnect, disconnect the connection between the motor stator winding combined inductance and the inverter combined bridge arm, and the electric vehicle starts normally.

[0081] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of this patent rather than to limit it. Although this patent has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of this patent can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of this patent, which should be included in the scope of the claims of this patent.

Claims

1. A method for controlling stator winding reuse and battery heating of a motor, characterized in that: The three-phase stator windings of the motor are connected in parallel to form a motor stator winding combined inductance, which is combined with an inverter and a battery pack to form a battery heating system, so that the B1 battery pack and the B2 battery pack are charged and discharged mutually through the motor winding combined inductance, generating Joule heat to heat the battery pack internally; wherein, The battery heating system includes a first inverter, a second inverter, a detection unit, a control unit and a motor stator winding combined inductor, the B1 battery pack is connected in parallel with the first inverter; the B2 battery pack is connected in parallel with the second inverter; the negative electrode of the B1 battery pack is connected to the negative electrode of the B2 battery pack; the midpoints of the bridge arms of the first inverter and the second inverter are respectively connected to the motor winding combined inductor; The control unit detects the surface temperature of the battery pack and the current flowing through the motor winding combined inductance through the detection unit, and controls the on and off of the fully controlled devices in the first inverter and the second inverter according to the detection results, so that a self-heating current is generated inside the lithium battery, and the size and frequency of the charge and discharge current are adjusted; The motor stator winding combined inductance is formed by connecting the phase windings of a single motor stator in parallel, one end of the single motor stator winding is connected to the midpoint of the bridge arm of the first inverter, and the other end is connected to the midpoint of the bridge arm of the second inverter, the left and right tubes of the upper / lower bridge arm of the first inverter are synchronously turned on to short-circuit the circuit at one end, and the left and right tubes of the upper / lower bridge arm of the second inverter are synchronously turned on to short-circuit the circuit at the other end, and by controlling the left and right tubes of the upper / lower bridge arm of the first inverter and the second inverter to be synchronously turned on, the parallel connection between the phase windings of the stator connected to the midpoint of the bridge arm is realized to form the motor stator winding combined inductance.

2. A method for controlling motor stator winding reuse and battery heating, characterized in that: The three-phase stator windings of the motor are connected in parallel to form a motor stator winding combined inductance, which is combined with the inverter / motor controller and the battery pack to form a battery heating system, so that the B1 battery pack and the B2 battery pack are charged and discharged with each other through the motor winding combined inductance, generating Joule heat to heat the battery pack internally; wherein, The battery heating system includes a first inverter, a second inverter, a detection unit, a control unit and a motor stator winding combined inductor, the B1 battery pack is connected in parallel with the first inverter; the B2 battery pack is connected in parallel with the second inverter; the negative electrode of the B1 battery pack is connected to the negative electrode of the B2 battery pack; the midpoints of the bridge arms of the first inverter and the second inverter are respectively connected to the motor winding combined inductor; The control unit detects the surface temperature of the battery pack and the current flowing through the motor winding combined inductance through the detection unit, and controls the on and off of the fully controlled devices in the first inverter and the second inverter according to the detection results, so that a self-heating current is generated inside the lithium battery, and the size and frequency of the charge and discharge current are adjusted; The motor stator winding combined inductance is composed of dual motor stator windings connected in series and in parallel. The first inverter and the second inverter are respectively connected to the stator winding of one motor in the dual motors. The parallel connection between the phase windings of the motor stator connected to the midpoint of the bridge arm is realized by controlling the left and right tubes of the upper / lower bridge arms of the first inverter and the second inverter to be synchronously turned on. The two motor stator winding combined inductances respectively connected to the first and second inverters are connected to the midpoints of the motor stator windings through the Y-connection, forming a mutually serially connected motor stator winding combined inductance across the midpoints of the two inverter combined bridge arms.

3. A method for controlling motor stator winding reuse and battery heating, characterized in that: The three-phase stator windings of the motor are connected in parallel to form a motor stator winding combined inductance, which is combined with the inverter / motor controller and the battery pack to form a battery heating system, so that the B1 battery pack and the B2 battery pack are charged and discharged with each other through the motor winding combined inductance, generating Joule heat to heat the battery pack internally; wherein, The battery heating system includes a first inverter, a second inverter, a detection unit, a control unit and a motor stator winding combined inductor, the B1 battery pack is connected in parallel with the first inverter; the B2 battery pack is connected in parallel with the second inverter; the negative electrode of the B1 battery pack is connected to the negative electrode of the B2 battery pack; the midpoints of the bridge arms of the first inverter and the second inverter are respectively connected to the motor winding combined inductor; The control unit detects the surface temperature of the battery pack and the current flowing through the motor winding combined inductance through the detection unit, and controls the on and off of the fully controlled devices in the first inverter and the second inverter according to the detection results, so that a self-heating current is generated inside the lithium battery, and the size and frequency of the charge and discharge current are adjusted; The motor stator winding combined inductance is formed by connecting multiple motor stator windings in parallel, the first inverter and the second inverter are formed by connecting a plurality of inverter groups in parallel, each inverter group has the same structure, and the midpoint of each inverter bridge arm in the first inverter and the second inverter is respectively connected to the motor winding combined inductance; Each inverter group in the first inverter and the second inverter is respectively connected to a motor stator winding, and the parallel connection between the stator phase windings connected to the midpoint of the bridge arm is realized by controlling the left and right tubes of the upper / lower bridge arm of the inverter to be synchronously turned on; the stator windings connected to each inverter group in the first inverter are connected in parallel by connecting the motor stator winding Y-connected to the midpoint to form a first parallel inductance, and the stator windings connected to each inverter group in the second inverter are connected in parallel by connecting the motor stator winding Y-connected to the midpoint to form a second parallel inductance, and the first parallel inductance and the second parallel inductance are connected in series by connecting the motor stator winding Y-connected to the midpoint to form a motor stator winding combined inductance.

4. The method for controlling stator winding reuse and battery heating of a motor according to claim 1, characterized in that: The midpoints of the two inverter bridge arms are respectively connected to the external inductor through the contactor KM contacts. The closing / opening of the contactor KM contacts is controlled by the control unit. The control unit controls the closing / opening of the contactor KM contacts to realize the closing / opening of the electrical connection between the external inductor and the inverter combined bridge arm.

5. A motor stator winding reuse and battery heating control method according to any one of claims 1 to 4, characterized in that: During the battery heating process, the charge state balance control between the B1 battery pack and the B2 battery pack is simultaneously implemented. The balance control is achieved by adjusting the ratio T1 / T2 of the charging cycle T1 and the discharging cycle T2. The specific process is as follows: When the expected values ​​of the stator winding combination inductance current are the same, the average values ​​of the battery terminal voltages of the B1 battery pack and the B2 battery pack during the discharge cycle are measured and recorded as U1 and U2, and the ratio of the charging cycle T1 to the discharging cycle T2 of the B1 battery pack is allocated according to T2 / T1=U1 / U2.

6. The method for controlling stator winding reuse and battery heating of a motor according to claim 5, characterized in that: The B1 battery pack and the B2 battery pack are both connected to a load. During the battery heating process, when the B1 battery pack and the B2 battery pack are loaded and the battery internal heating program is implemented, the ratio T1 / T2 of the charging cycle T1 and the discharging cycle T2 of the B1 battery pack in the battery heating system is determined according to the power difference △P or the current difference △I of the load carried by the B1 battery pack and the B2 battery pack during the heating process; If the load current carried by the B1 battery pack is greater than the load current carried by the B2 battery pack by △I, and the expected value of the current flowing through the inductor is I, then T2 / T1=I / (I+△I); conversely, if the load current carried by the B1 battery pack is less than the load current carried by the B2 battery pack by △I, then T2 / T1=I / (I-△I).

7. The method for controlling stator winding reuse and battery heating of a motor according to claim 5, characterized in that: The ratio of the charging cycle T1 to the discharging cycle T2 of the B1 battery pack is allocated according to T2 / T1=k1*U1 / U2+k2*I / (I+△I) or T2 / T1=k1*U1 / U2+k2*I / (I-△I), where U1 and U2 are the average values ​​of the battery terminal voltages of the B1 battery pack and the B2 battery pack during the discharge cycle, and K1 and K2 are preset or real-time adjustable coefficients.

8. A lithium battery heating system, characterized in that: The lithium battery heating system implements a motor stator winding reuse and battery heating control method as described in any one of claims 1 to 7.

9. An electric vehicle, characterized in that: The electric vehicle comprises a motor, a first inverter, a second inverter, a B1 battery pack, a B2 battery pack and a lithium-ion battery heating system, and the lithium-ion battery heating system implements a motor stator winding reuse and battery heating control method as described in any one of claims 1 to 7.

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