A hybrid vehicle drive system suitable for fast cold start in extremely cold environments

Abstract

The application provides a hybrid vehicle driving system suitable for quick cold start in extremely cold environment, which can utilize a small amount of electric energy provided by a lithium battery pack under low temperature conditions, and realize AC internal heating of the lithium battery pack through the combination of the six-phase generator winding and the bridge arm gating control of the double three-phase controllable rectifier module. On this basis, the system also provides the function of heating by the external heating module and the external circulation system, and can be flexibly combined and superimposed with the AC internal heating according to the actual needs, so as to rapidly heat the lithium battery pack and rapidly preheat the engine. The system structure can be realized only by a small amount of improvement on the existing hybrid vehicle, has high reliability and low cost, reduces the equipment maintenance cost and the maintenance period, and is well applicable to various different vehicle models.

Description

Technical Field

[0001] This invention belongs to the technical field of hybrid vehicle drive systems, specifically relating to a hybrid vehicle drive system suitable for rapid cold start in extremely cold environments. Background Technology

[0002] Lithium-ion batteries are highly sensitive to temperature, and their actual performance during operation is easily affected by temperature changes. In extremely cold environments, the internal resistance of lithium-ion batteries increases sharply, severely limiting their discharge capacity and charging performance. This not only significantly impairs the power and driving range of hybrid vehicles, but also prevents the starter motor from reaching the engine speed required for a normal cold start, resulting in the engine failing to start. Furthermore, at extremely low temperatures, the increased viscosity and reduced flow of engine oil, poor fuel atomization, decreased cylinder pressure, and excessively low cylinder temperature further exacerbate the difficulty of cold starting the engine. While it is possible to provide heating for the lithium-ion battery pack, engine, and fuel supply system of vehicles in low temperatures using external equipment and methods when conditions permit, this is clearly not feasible for many usage scenarios, such as in the wild.

[0003] Existing battery heating technologies typically employ external heating via PTC resistors or circulating systems. However, external heating with PTC resistors suffers from low heat transfer efficiency, uneven battery heating, and slow temperature rise rates. Similarly, external heating via circulating systems also suffers from significantly reduced battery energy density, uneven heating, and excessively slow temperature rise rates. Various methods for engine cold start preheating, such as intake air preheating via heated plugs, combustion chamber preheating, and engine block preheating via liquid circulation systems, can mitigate fuel atomization degradation and improve oil flow to some extent, thereby reducing starting torque. However, they are ineffective in addressing the insufficient starting power caused by low temperatures. Therefore, providing a method for rapid cold start of hybrid vehicles under extremely cold conditions is one of the most pressing issues to be addressed in this field. Summary of the Invention

[0004] In view of this, and to address the technical problems existing in this field, the present invention provides a hybrid vehicle drive system suitable for rapid cold start in extremely cold environments, specifically comprising:

[0005] The system includes a lithium battery pack, a battery management module, a dual three-phase controllable rectifier module, a dual three-phase controllable rectifier control module, a six-phase generator, an engine, an engine control module, a dual three-phase controllable inverter module, a dual three-phase controllable inverter control module, and two drive motors.

[0006] The lithium battery pack contains two sets of lithium battery modules connected in parallel with identical group configuration and electrical parameters. A module switch controlled by the battery management module is provided between the lithium battery modules. The battery management module is used to control the heating of each lithium battery module in different ways, and when AC internal heating is used, the heating current amplitude and frequency signal are sent to the dual three-phase controllable rectifier control module through the communication bus to realize the on-off control of each power switch in the dual three-phase controllable rectifier module.

[0007] The dual three-phase controllable rectifier module has two groups of 12 power switching transistors. Each group consists of three bridge arms, with the neutral point of each bridge arm serving as the AC side and the two ends of the bridge arm serving as the DC side. These are electrically connected to the positive and negative terminals of the lithium battery pack output via a DC bus. The six-phase generator consists of two groups of three-phase windings, each with the same inductive load. Each winding terminal is electrically connected to the neutral point of one bridge arm of the dual three-phase controllable rectifier module, and the neutral points of the two three-phase windings are electrically connected to each other. The dual three-phase controllable rectifier control module controls the switching on and off of each power switching transistor in the dual three-phase controllable rectifier module, enabling the windings of the two battery modules and the two six-phase generators to form a circuit. In conjunction with the switching on and off of the module switches, the forward and reverse charging and discharging cycles of the circuit elements generate AC excitation on the internal resistance of the lithium battery pack, thereby achieving AC internal heating.

[0008] The dual three-phase controllable inverter module has the same power switch tube structure as the dual three-phase controllable rectifier module. The neutral point of the bridge arm of each power switch tube serves as the AC side and is electrically connected to the winding of one of the drive motors. The two ends of the bridge arm are DC sides and are electrically connected to the positive and negative terminals of the lithium battery pack output through a DC bus. The dual three-phase controllable inverter control module is used to control the on and off of each power switch tube, enabling the drive motor to electrically drive the vehicle.

[0009] The six-phase generator is mechanically connected to the engine. When the lithium battery pack is heated to a predetermined temperature, the dual three-phase controllable rectifier module drives the six-phase generator to rotate the engine to reach the ignition condition. The engine control module is used to collect engine operating parameters and calculate the reverse drag speed, and feeds them back to the dual three-phase controllable rectifier module through the communication bus to realize closed-loop control of engine speed.

[0010] Furthermore, the dual three-phase controllable rectifier module and the dual three-phase controllable inverter module share the same set of power switching transistors. By switching the neutral point of the bridge arm and the electrical connection method between the two ends of each bridge arm in the system, the rectification or inversion functions of the two modules can be realized in the system respectively. The dual three-phase controllable rectifier control module and the dual three-phase controllable inverter control module are also implemented by the same controller, and perform corresponding control when switching the rectification or inversion function through the electrical connection method.

[0011] Furthermore, the battery management module controls the heating of the lithium battery pack not only through AC internal heating but also through an external electric heating module or an external circulating heating method. The external electric heating module or external circulating heating method can be simultaneously superimposed on AC internal heating or performed in a predetermined order and combination. The external electric heating module or external circulating heating method is turned on or off by the external electric heating switch. The battery management module determines whether the external electric heating module or external circulating heating method needs to be turned on in addition to AC internal heating based on the collected lithium battery pack operating parameters.

[0012] Furthermore, in the lithium-ion battery pack, each lithium battery module has a branch connected in parallel between its positive and negative terminals, consisting of an external electric heating switch and an external electric heating module connected in series; the battery management module controls the external electric heating module to heat the battery by switching the external electric heating switch on and off.

[0013] Furthermore, the heat generated by the six-phase generator windings and the power switching tubes of the dual three-phase controllable rectifier module during operation is introduced into an external circulating heating system for external heating.

[0014] Furthermore, upon receiving a cold start command from the vehicle, the battery management module collects operating parameters of the lithium battery pack, including temperature, voltage, and state of charge, through corresponding sensors to determine whether to perform internal AC heating and whether other heating methods need to be superimposed.

[0015] Furthermore, the engine control module collects cylinder temperature, cylinder pressure and load torque parameters when the engine is working, and calculates the anti-drag speed based on these parameters.

[0016] Furthermore, when the temperature reaches the starting condition, the vehicle makes a decision on whether to have the engine control module control the engine for reverse towing or pure electric drive, based on the detected engine cylinder temperature, state of charge, and driver input commands; after the engine starts, the six-phase generator switches to power generation mode.

[0017] The hybrid vehicle drive system for rapid cold start in extremely cold environments provided by this invention can utilize the limited electrical energy provided by the lithium battery pack under low-temperature conditions. This is achieved through AC internal heating of the lithium battery pack via a six-phase generator winding combined with the bridge arm selection control of a dual three-phase controllable rectifier module. Furthermore, the system also provides heating functionality using an external heating module and an external circulation system. These can be flexibly combined and superimposed with AC internal heating as needed, enabling rapid heating of the lithium battery pack and rapid preheating of the engine. This system structure requires only minor modifications to existing hybrid vehicles, offering high reliability and low cost, reducing equipment maintenance costs and repair cycles, and is well-suited for various vehicle models. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the system provided by the present invention;

[0019] Figure 2 This is a schematic diagram illustrating the structural principle of the system for implementing AC internal heating provided by the present invention.

[0020] Figure 3 The circuit diagram for implementing AC internal heating in the system provided by this invention;

[0021] Figure 4 This is a schematic diagram of the complete internal heating cycle in an example of the present invention;

[0022] Figure 5 This is a schematic diagram illustrating the principle of heating using an external electric heating module in the system provided by the present invention.

[0023] Figure 6 This is a flowchart illustrating the rapid cold start of the system provided by the present invention under extremely cold conditions. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The present invention provides a hybrid vehicle drive system suitable for rapid cold start in extremely cold environments, such as... Figure 1 As shown, it specifically includes:

[0026] The system includes a lithium battery pack, a battery management module, a dual three-phase controllable rectifier module, a dual three-phase controllable rectifier control module, a six-phase generator, an engine, an engine control module, a dual three-phase controllable inverter module, a dual three-phase controllable inverter control module, and two drive motors.

[0027] The lithium battery pack contains two sets of lithium battery modules connected in parallel with identical group configuration and electrical parameters. A module switch K3 controlled by the battery management module is provided between the lithium battery modules. The battery management module is used to control the heating of each lithium battery module in different ways, and when AC internal heating is used, the heating current amplitude and frequency signal are sent to the dual three-phase controllable rectifier control module through the communication bus to realize the on-off control of each power switch in the dual three-phase controllable rectifier module.

[0028] Among them, such as Figure 2 and 3As shown, the dual three-phase controllable rectifier module has two groups of a total of 12 power switches. Each group consists of three bridge arms, with the power switches paired up: the first bridge arm of the first group, the second bridge arm of the first group, the third bridge arm of the first group, the first bridge arm of the second group, the second bridge arm of the second group, and the third bridge arm of the second group. Specifically, the first bridge arm of the first group includes power switch Q11 (also called the upper power switch of the first bridge arm) and power switch Q14 (also called the lower power switch of the first bridge arm); the second bridge arm of the first group includes power switch Q12 (also called the upper power switch of the first bridge arm) and power switch Q15 (also called the lower power switch of the first bridge arm); the third bridge arm of the first group includes power switch Q13 (also called the upper power switch of the first bridge arm) and power switch Q16 (also called the lower power switch of the first bridge arm); and the first bridge arm of the second group includes power switch Q21 (also called the upper power switch of the second bridge arm). The first group of bridge arms consists of two power switches: Q22 (also known as the upper power switch of the second group of bridge arms) and Q25 (also known as the lower power switch of the second group of bridge arms). The second group of bridge arms consists of two power switches: Q23 (also known as the upper power switch of the second group of bridge arms) and Q26 (also known as the lower power switch of the second group of bridge arms). During operation, the AC internal heating circuit uses a dual three-phase controllable rectifier module circuit to select any one of the first group of bridge arms and any one of the second group of bridge arms for series connection into the heating circuit. The neutral point of each bridge arm serves as the AC side, and the two ends of the bridge arm are DC sides, electrically connected to the positive and negative terminals of the lithium battery pack output via a DC bus.

[0029] The six-phase generator consists of two sets of three-phase windings, each with the same inductive load, which can be equivalent to a resistor and an inductor connected in series. The inductances between the six terminals of the six-phase generator and the neutral point include inductors L1, L2, L3, L4, L5, and L6. Each winding terminal is electrically connected to the neutral point of one arm of the dual three-phase controllable rectifier module, and the neutral points of the two three-phase windings are electrically connected to each other. The dual three-phase controllable rectifier control module controls the on / off state of each power switch of the dual three-phase controllable rectifier module, so that the windings of the two battery modules and the two six-phase generators form a circuit. When the AC internal heating circuit is working, it can select any set of windings in the six-phase generator, and cooperate with the on / off state of the module switch to generate AC excitation on the internal resistance of the lithium battery pack through the forward and reverse charging and discharging cycle of the circuit elements, thereby realizing AC internal heating.

[0030] The dual three-phase controllable inverter module has the same power switch tube structure as the dual three-phase controllable rectifier module. The neutral point of the bridge arm of each power switch tube serves as the AC side and is electrically connected to the winding of one of the drive motors. The two ends of the bridge arm are DC sides and are electrically connected to the positive and negative terminals of the lithium battery pack output through a DC bus. The dual three-phase controllable inverter control module is used to control the on and off of each power switch tube, enabling the drive motor to electrically drive the vehicle.

[0031] The six-phase generator is mechanically connected to the engine. When the lithium battery pack is heated to a predetermined temperature, the dual three-phase controllable rectifier module drives the six-phase generator to rotate the engine to reach the ignition condition. The engine control module is used to collect engine operating parameters and calculate the reverse drag speed, and feeds them back to the dual three-phase controllable rectifier module through the communication bus to realize closed-loop control of engine speed.

[0032] During the AC internal heating process, any one or more of the three bridge arms in the first group and any one or more of the three bridge arms in the second group are selected by the dual three-phase controllable rectifier module. Correspondingly, the AC internal heating circuit selects the motor winding corresponding to the bridge arm.

[0033] The following uses the first group of bridge arms and its corresponding second group of bridge arms as examples to illustrate the selection of bridge arms and the configuration of the AC internal heating circuit. The same method applies to the selection of non-corresponding bridge arms. For example, when selecting the upper power switch of the first group of first bridge arms and the lower power switch of the second group of first bridge arms, the lithium battery module one, the first group of first bridge arms, inductors L1 and L4, the second group of first bridge arms, and the lithium battery module two constitute the AC internal heating circuit. When selecting the upper power switch of the first group of first bridge arms, the upper power switch of the first group of second bridge arms, the lower power switch of the second group of first bridge arms, and the lower power switch of the second group of second bridge arms, the lithium battery module one, the first group of first bridge arms, the first group of second bridge arms, inductors L1, L2, L4, L5, the second group of first bridge arms, the second group of second bridge arms, and the lithium battery module two constitute the AC internal heating circuit. Battery module 2 forms an AC internal heating circuit; when selecting the first group of first bridge arm upper power switch, the first group of second bridge arm upper power switch, the first group of third bridge arm upper power switch and the second group of first bridge arm lower power switch, the second group of second bridge arm lower power switch and the second group of third bridge arm lower power switch, lithium battery module 1, the first group of first bridge arm, the first group of second bridge arm, the first group of third bridge arm, inductors L1, L2, L3, L4, L5, L6, the second group of first bridge arm, the second group of second bridge arm, the second group of third bridge arm and lithium battery module 2 form an AC internal heating circuit.

[0034] More specifically, the AC internal heating circuit is composed of the real part of the AC impedance of lithium battery module one, the real part of the AC impedance of lithium battery module two, the lithium battery module switch, and the inductance of one or more bridge arms of the first and second groups of the dual three-phase controllable rectifier module and the inductance of one or more phase windings corresponding to the bridge arms.

[0035] Figure 4 (a), (b), (c), and (d) illustrate an example of the present invention in which the first bridge arms of the first and second groups are selected to perform four stages within the AC internal heating cycle, including the following stages T1, T2, T3, and T4:

[0036] During phase T1, the battery management module first controls the lithium battery module switch to turn off. The dual three-phase controllable rectifier control module controls power switch Q11 and power switch Q24 to be forward-biased, while other power switches are in forward-biased off state. The lithium battery module then charges inductors L1 and L4.

[0037] In stage T2, when inductors L1 and L4 reach a certain energy storage, the dual three-phase controllable rectifier control module controls power switch Q11 and power switch Q21 to conduct in the forward direction, while other power switches are turned off in the forward direction. At this time, power switch Q21 is in the reverse direction under the freewheeling effect of the inductor, and lithium battery module 1, inductors L1 and L4 charge lithium battery module L2 together.

[0038] In stage T3, when the energy stored in inductors L1 and L4 is depleted, the current reverses. The dual three-phase controllable rectifier control module controls power switch Q14 and power switch Q21 to conduct in the forward direction, while other power switches are in the forward cutoff direction. The lithium battery module 2 charges inductors L1 and L4.

[0039] In stage T4, once inductors L1 and L4 have accumulated a certain amount of energy, the dual three-phase controllable rectifier control module controls power switches Q11 and Q21 to conduct in the forward direction, while other power switches are forward-biased and cut off. At this time, power switch Q11 is reverse-biased due to the freewheeling current from the inductor, and lithium battery module two, along with inductors L1 and L4, charge lithium battery module one. This completes one AC internal heating cycle.

[0040] During the heating cycle described above, the upper and lower power switches of the first bridge arm of the first group and the upper and lower power switches of the second group of the first bridge arm work alternately to achieve power transfer between the lithium battery module one and the lithium battery module two. The real part of the AC impedance of the lithium battery module one and the real part of the AC impedance of the lithium battery module two generate heat and spread rapidly inside the battery, causing the temperature of the power battery pack to rise. Thus, the power battery pack generates heat under the action of AC power and heats itself from the inside.

[0041] During the above process, the battery management module continuously collects operating parameters of the lithium battery pack, including temperature, voltage, and state of charge, through corresponding sensors. When the lithium battery pack is heated to a predetermined temperature, the dual three-phase controllable rectifier module drives the six-phase generator to rotate the engine and achieve ignition conditions. The engine control module collects operating parameters of the engine, such as cylinder temperature, cylinder pressure, and load torque, and calculates the reverse drag speed based on these parameters. This calculation is then fed back to the dual three-phase controllable rectifier module via the communication bus to achieve closed-loop control of the engine speed.

[0042] When AC internal heating alone is insufficient to meet the requirements for rapid cold start, the battery management module can determine whether external electric heating or external circulating heating is needed. External electric heating or external circulating heating can be simultaneously superimposed on AC internal heating or performed in a predetermined sequence and combination, and the external electric heating module or external circulating heating can be turned on or off via the external electric heating switch. The battery management module, based on the collected lithium battery pack operating parameters, determines whether external electric heating or external circulating heating needs to be activated in addition to AC internal heating. The external electric heating module can employ methods such as... Figure 5 As shown, in the configuration shown, a branch consisting of an external electric heating switch and an external electric heating module connected in series is connected in parallel between the positive and negative terminals of each lithium battery module in the lithium-ion battery pack. The battery management module controls the external electric heating module to heat the battery by switching the external electric heating switch on and off.

[0043] When the temperature reaches the starting condition, the vehicle makes a decision on whether to have the engine control module control the engine for reverse towing or pure electric drive, based on the detected engine cylinder temperature, state of charge, and driver input commands. After the engine starts, the six-phase generator switches to power generation mode. Figure 6 The diagram shows the text flow of a hybrid vehicle that can quickly start in extremely cold environments, as implemented by the system provided by this invention.

[0044] The six-phase generator winding and the power switching tube of the dual three-phase controllable rectifier module of the present invention generate a large amount of heat energy when they are working. Therefore, they can also be used as a heat source and this part of the heat energy can be introduced into an external circulating heating system for external heating.

[0045] In a preferred embodiment of the present invention, the dual three-phase controllable rectifier module and the dual three-phase controllable inverter module share the same set of power switching transistors. By switching the neutral point of the bridge arm and the electrical connection method between the two ends of each bridge arm in the system, the rectification or inversion functions of the two modules are realized in the system respectively. The dual three-phase controllable rectifier control module and the dual three-phase controllable inverter control module are also implemented by the same controller, and perform corresponding control when switching the rectification or inversion function through the electrical connection method.

[0046] In this system, the six-phase generator and two drive motors can use compatible wiring, allowing for interchangeable wiring and substitution in case of faults or other necessary scenarios. The interchangeable wiring method involves equivalently connecting the L1, L2, and L3 winding ports of the six-phase generator corresponding to the dual three-phase controllable rectifier module to the U, V, and W ports of the first drive motor corresponding to the dual three-phase controllable inverter module; and equivalently connecting the L4, L5, and L6 winding ports of the six-phase generator corresponding to the dual three-phase controllable rectifier module to the U, V, and W ports of the second drive motor corresponding to the dual three-phase controllable inverter module; the DC bus port wiring method remains unchanged.

[0047] Those skilled in the art will understand that, under the guidance of this invention, many of the functions of this invention can be achieved using existing sensing units, controllers, and circuits. For example, a current sensor can detect the input and output current values ​​of lithium battery module one and lithium battery module two, and output the detection results to the battery management module; a voltage sensor can detect the voltage values ​​of lithium battery module one and lithium battery module two, and output the detection results to the battery management module; a temperature sensor can detect the temperature of lithium battery module one and lithium battery module two, and output the detection results to the battery management module; furthermore, the battery management module calculates the state of charge (SOC) of the lithium battery pack based on the current value from the current sensor, the voltage value from the voltage sensor, and the temperature value from the temperature sensor. The SOC calculation can employ various known methods. The calculated SOC, current, voltage, and temperature are used to determine the current amplitude, frequency, and operating mode of the AC internal heating. The operating mode includes turning on or off the AC internal heating, whether external circulating heating is performed simultaneously, and whether external electric heating is performed simultaneously. The battery management module can be connected to lithium battery module one and lithium battery module two via signal lines. The amplitude and frequency of the internal heating current are sent to the dual three-phase controlled rectifier control module via the communication bus. The dual three-phase controlled rectifier control module controls the opening and closing of the power switching transistors of the dual three-phase controlled rectifier module through signal lines. The communication methods between the nodes of the communication bus include, but are not limited to, CAN communication, FlexRay communication, and Ethernet communication.

[0048] It should be understood that the sequence number of each step in the embodiments of the present invention does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hybrid vehicle drive system suitable for fast cold start in extremely cold environments, characterized by: Specifically comprising: lithium battery pack, battery management module, double three-phase controllable rectifier module, double three-phase controllable rectifier control module, six-phase generator, engine, engine control module, double three-phase controllable inverter module, double three-phase controllable inverter control module and two drive motors; The lithium battery pack includes two groups of lithium battery modules that are parallel to each other, in a group form and have completely consistent electrical parameters, and a module switch controlled by the battery management module is arranged between the lithium battery modules; the battery management module is used to control heating of each lithium battery module in different ways, and when alternating current internal heating is used, a heating current amplitude and a frequency signal are sent to the double three-phase controllable rectifier control module through a communication bus to realize on-off control of each power switch tube in the double three-phase controllable rectifier module; The double three-phase controllable rectifier module has a total of 12 power switch tubes in two groups, and the power switch tubes in each group are respectively paired to form three bridge arms, the neutral points of each bridge arm are used as an alternating current side, and the two ends of the bridge arm are used as direct current sides and are electrically connected to the positive and negative poles of the output end of the lithium battery pack through a direct current bus; the six-phase generator is composed of two three-phase windings, each winding has the same inductive load, and the terminals of each winding are electrically connected to the neutral points of one bridge arm of the double three-phase controllable rectifier module, and the neutral points of the two three-phase windings are electrically connected to each other; the double three-phase controllable rectifier control module is used to control the on-off of the power switch tubes of the double three-phase controllable rectifier module, so that the two battery modules and the windings of the two six-phase generators form a loop, and the on-off of the module switch is matched, the positive and negative charging and discharging cycles of the loop elements generate alternating current excitation to the internal resistance of the lithium battery pack, thereby realizing alternating current internal heating; The double three-phase controllable inverter module has the same power switch tube structure as the double three-phase controllable rectifier module, the neutral points of each bridge arm of the power switch tubes in each group are used as an alternating current side, and are electrically connected to the windings of one of the two drive motors, and the two ends of the bridge arm are used as direct current sides and are electrically connected to the positive and negative poles of the output end of the lithium battery pack through a direct current bus; the double three-phase controllable inverter control module is used to control the on-off of each power switch tube, so that the drive motor realizes electric power driving of the vehicle; The six-phase generator is mechanically connected to the engine, when the lithium battery pack is heated to a predetermined temperature, the double three-phase controllable rectifier module drives the six-phase generator to drive the engine to rotate to reach the ignition condition; The engine control module is used to collect engine operating parameters and calculate the reverse drag speed, and feedback to the double three-phase controllable rectifier module through a communication bus to realize engine speed closed-loop control.

2. The system of claim 1, wherein: The double three-phase controllable rectifier module and the double three-phase controllable inverter module share the same set of power switch tube structures, the electrical connection mode of the neutral points of the bridge arms and the two ends of each bridge arm in the system is switched, thereby realizing the rectification or inversion function of the two modules in the system; the double three-phase controllable rectifier control module and the double three-phase controllable inverter control module are also realized by the same controller, and when the rectification or inversion function is switched through the electrical connection mode, the corresponding control is performed.

3. The system of claim 1, wherein: The battery management module controls the lithium battery pack to be heated by external electric heating module or external circulation heating mode in addition to AC internal heating; the external electric heating module or external circulation heating mode and the AC internal heating can be simultaneously superimposed or performed in a predetermined order and combination, and the external electric heating module or external circulation heating is turned on or off by the external electric heating switch; the battery management module determines whether the external electric heating module or external circulation heating needs to be turned on in addition to the AC internal heating according to the collected working parameters of the lithium battery pack.

4. The system of claim 3, wherein: In the lithium battery pack, a branch composed of an external electric heating switch and an external electric heating module is connected in parallel between the positive and negative electrodes of each lithium battery module; the battery management module controls the external electric heating module to heat by turning on and off the external electric heating switch.

5. The system of claim 3, wherein: The heat generated by the six-phase generator winding and the power switch tube of the double three-phase controllable rectification module during work is introduced into an external circulation heating system for external heating.

6. The system of claim 1, wherein: The battery management module specifically receives a cold start instruction of the vehicle, collects working parameters of the lithium battery pack including temperature, voltage and state of charge through a corresponding sensor, determines whether to perform internal AC heating and whether to superimpose other heating modes.

7. The system of claim 1, wherein: The engine control module collects cylinder temperature, in-cylinder pressure and load torque parameters during engine work, and calculates the reverse driving speed based on these parameters.

8. The system of claim 1, wherein: When the temperature reaches the starting condition, the vehicle makes a decision whether to control the engine to start by the engine control module or to drive by pure electricity according to the detected engine cylinder temperature, state of charge and driver input instruction; After the engine starts, the six-phase generator switches to the power generation mode.

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