CN109050518B

CN109050518B - Hybrid power system and cold start method thereof

Info

Publication number: CN109050518B
Application number: CN201810691987.4A
Authority: CN
Inventors: 张光耀; 马勇; 王明强
Original assignee: United Automotive Electronic Systems Co Ltd
Current assignee: United Automotive Electronic Systems Co Ltd
Priority date: 2018-06-28
Filing date: 2018-06-28
Publication date: 2021-06-08
Anticipated expiration: 2038-06-28
Also published as: CN109050518A

Abstract

The invention provides a hybrid power system.A power battery provides a power supply for a transmission mechanism, and comprises a super capacitor module and a lithium battery module; the DC-DC conversion module realizes bidirectional charging between a control power supply and the power battery; the engine is used for providing power energy for the transmission mechanism when the power battery is insufficient in energy; the power-assisted recovery motor recovers energy and stores the energy in the power battery when the engine is braked, starts the engine when the engine is started, and performs acceleration power assistance on the engine when the engine is accelerated; and the hybrid power control unit is respectively connected with the power battery, the DC-DC conversion module, the control power supply and the power-assisted recovery motor, and controls and coordinates the work in the hybrid power system. The invention has the advantages of canceling a special starting motor for the engine, reducing material cost, saving space in the vehicle and simultaneously reducing the performance requirement of the control power supply.

Description

Hybrid power system and cold start method thereof

Technical Field

The invention relates to the field of power systems of automobiles, in particular to a hybrid power system and a cold start method thereof.

Background

The electric automobile is a vehicle which takes a vehicle-mounted power supply as power and drives wheels by a motor to run, and meets various requirements of road traffic and safety regulations. Because the influence on the environment is smaller than that of the traditional automobile, the automobile is a recommended automobile model at present. The electric automobile is divided into: a pure electric vehicle (BEV), a hybrid electric vehicle (PHEV), and a fuel cell vehicle (FCEV). At present, a pure electric vehicle is limited by imperfect charging facilities and cannot be generally applied. The hybrid electric vehicle is supplemented by two energy sources, namely a battery and a fuel, so as to provide power for vehicles together.

As shown in fig. 1, a conventional hybrid system 3' includes 2 starter motors: 12V starting motor and helping hand recovery motor. The reason for using 2 starting motors in the system at the same time is caused by the poor low-temperature performance of the power battery (mainly 48V battery). In the prior art, all power batteries are single lithium batteries, and the capacity of the power batteries is mostly between 8Ah and 10Ah in consideration of cost control. However, the discharge capacity of the lithium battery is greatly reduced at low temperature (-10 to-30 ℃), namely, even if the electric capacity of the lithium battery is enough at low temperature (-10 to-30 ℃), the instantaneous output current of the lithium battery is still insufficient to support the power-assisted recovery motor to start the engine, so that the system has to keep the traditional control power supply and a 12V starting motor special for the engine. The 12V battery in the prior art is generally a lead-acid battery, and the output current of the lead-acid battery at the low temperature is enough to support the 12V starting motor to start the engine, so that the prior hybrid power system has to simultaneously reserve a large-capacity control power supply and the 12V motor to support the working condition of low-temperature cold start. In order to cover the working condition of low-temperature cold start, the power system has certain requirements on the capacity and the discharge power of the control power supply, and the production cost is increased. Meanwhile, the traditional motor has the defects of long starting time and large starting noise.

In summary, the conventional hybrid system has the disadvantages that 2 groups of high-performance and large-capacity batteries (48V and 12V) must be included at the same time, the power system has redundancy, the battery utilization rate is not high enough, and the cost of the power system is high.

Disclosure of Invention

In order to solve the problems, reduce the requirements on the performance of the battery, reduce redundancy and reduce cost, the invention provides a hybrid power system, which enables a power battery (48V battery) to be used for low-temperature cold start, thereby reducing the requirements on controlling the capacity and the discharge power of a power supply. The application range of the isolated 48V battery and the control power supply is determined, the 48V battery is specially used for the power of the vehicle, and the control power supply is specially used for a control system of the vehicle. The control system includes not only electric devices for controlling the driving posture of the vehicle but also various other electric devices designed for safety, comfort and convenience of driving in a broad sense.

The invention provides a hybrid power system for providing power for a vehicle, which comprises: the power recovery system comprises a power battery, a hybrid power control unit, a DC-DC conversion module, a control power supply, a power recovery motor and an engine;

the power battery is connected with a transmission mechanism in the vehicle and provides a power supply for the transmission mechanism, and the power battery comprises a super capacitor module and a lithium battery module;

the DC-DC conversion module is respectively connected with the control power supply and the power battery, and bidirectional charging is realized between the control power supply and the power battery;

the control power supply is connected with a control system of the vehicle and used for supplying power to the control system of the vehicle;

the engine is used for providing power energy for the transmission mechanism when the power battery is insufficient in energy;

the power-assisted recovery motor is connected with the engine, recovers energy and stores the energy in the power battery when the engine is braked, starts the engine when the engine is started, and performs acceleration power assistance on the engine when the engine is accelerated;

the power-assisted recovery motor is also connected with the power battery, and when the power-assisted recovery motor carries out acceleration power assistance on the engine, the power battery provides energy;

the hybrid power control unit is respectively connected with the power battery, the DC-DC conversion module, the control power supply and the power-assisted recovery motor, and controls and coordinates the work in the hybrid power system.

In the hybrid power system, the super capacitor module includes a super capacitor, a sensor and a super capacitor management module; the input end and the output end of the sensor are respectively connected with the super capacitor and the super capacitor management module, and the super capacitor management module collects voltage, current and temperature information of the super capacitor through the sensor.

The hybrid system described above, wherein the super capacitor includes:

a plurality of series connected super capacitor units;

and the super capacitor management module controls the charge and discharge interface to perform charge and discharge conversion according to the capacity information.

In the hybrid power system, the super capacitor management module is further connected to the hybrid power control unit, and the super capacitor is charged or discharged according to the control of the hybrid power control unit.

In the hybrid power system, the charge-discharge interface is further connected to the DC-DC conversion module.

In the hybrid system, the voltage of the power battery is 48V.

In the hybrid system, the voltage of the control power supply is 12V.

The hybrid system, wherein the super capacitor module is replaced by a lithium carbonate battery.

The invention also provides a cold start method based on the hybrid power system, which comprises the following steps:

s1, detecting the cold start of the engine by a control system of the vehicle;

s2, the control system of the vehicle evaluates the discharge capacity of the power battery;

s3, evaluating and evaluating the starting energy consumption of the engine by a control system of the vehicle;

s4, if the control system of the vehicle judges that the discharging capacity of the super capacitor module in the power battery meets the engine starting energy consumption, executing S7;

s5, if the vehicle control system judges that the discharging capacity of the lithium battery module in the power battery meets the engine starting energy consumption, executing S8;

s6, charging the super capacitor module by the control power supply, and then executing S4;

s7, supplying power to the engine by the super capacitor module, and then executing S9;

s8, supplying power to the engine by the lithium battery module, and then executing S9;

and S9, finishing the starting of the engine.

The cold start method of the hybrid power system further comprises the step of charging the super capacitor module after the engine is started or before the whole vehicle is powered off.

The cold start method of the hybrid system further includes, after the engine is started, the steps of:

s10, charging the super capacitor module by the aid of the power recovery motor or the control power supply;

and S12, completing charging of the super capacitor module.

The cold start method of the hybrid power system, wherein after the control system receives the power-off request of the entire vehicle, the method further includes:

s11, controlling the power supply to charge the super capacitor module;

and S12, completing charging of the super capacitor module.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. the 12V starting motor is reduced, the power-assisted recovery motor has the function, the material cost is directly reduced, and the space in the vehicle is saved.

2. Because the function of cold starting the engine at low temperature is not needed, the requirement on the capacity of the control power supply is greatly reduced, and the cost is reduced again.

3. The control power supply and the power battery have mutually charged channels, and can be mutually backed up when needed, so that the electric quantity is temporarily supplemented, and the flexibility of the system is greatly enhanced.

4. Because the 12V starting motor is eliminated, the power battery layout has abundant space.

Drawings

FIG. 1 is a block diagram of a hybrid powertrain system of the prior art;

FIG. 2 is a block diagram of an embodiment of the hybrid powertrain of the present invention;

FIG. 3 is a block diagram of one embodiment of a supercapacitor module of the present invention;

FIG. 4 is a schematic diagram of one embodiment of a power supply system of the present invention;

FIG. 5 is a flow chart of the engine cold start of the present invention;

FIG. 6 is a flow chart of a method of charging a supercapacitor after completion of an engine start in accordance with the present invention;

FIG. 7 is a flowchart of a method for charging a super capacitor before powering down the entire vehicle according to the present invention.

Detailed Description

The present invention will be described in more detail with reference to the accompanying drawings, which are included to illustrate embodiments of the present invention.

A hybrid system 3 shown in fig. 2 includes a power battery 31, a hybrid control unit 32 (connection relation is not shown), a DC-DC conversion module 33, a control power source 34, a power recovery motor 35, and an engine 36. The power battery 31 is connected with the transmission mechanism 1 in the vehicle, and provides power supply for the transmission mechanism 1, so that the vehicle can move. The power battery 31 and the engine 36 drive the transmission mechanism 1 in a time-sharing manner according to the following principle:

a. when the vehicle runs normally, the engine 36 is in a working state, the power-assisted recovery motor 35 is in an electric or power generation mode, and the torque outputs of the engine 36 and the power-assisted recovery motor 35 are distributed by the hybrid control unit 32 so as to drive the vehicle;

b. in the acceleration process of the vehicle, the power recovery motor 35 provides power (additionally provides energy) to accelerate the vehicle;

c. in the deceleration process of the vehicle, the power-assisted recovery motor 35 recovers energy generated in the braking process and stores the energy in the power battery 31 in the form of electric energy;

d. when the vehicle is in cold start, the power battery 31 supplies energy for the power-assisted recovery motor 35, and the power-assisted recovery motor 35 starts the engine 36.

The power battery 31 comprises a lithium battery module 312 and a super capacitor module 311. The capacity range of the lithium battery module 312 is between 8Ah and 10Ah, the discharge capacity of the lithium battery module is insufficient at low temperature (-10 to-30 ℃), and the lithium battery module is only suitable for being used as a conventional power energy source. The super capacitor module 311 has excellent low-temperature performance, can still output instantaneous large current at low temperature, can be used as an auxiliary energy storage component to supplement the capacity defect of a main battery (lithium battery) at low temperature, and is used for starting the engine 36.

One end of the power-assisted recovery motor 35 is connected with the power battery 31, and the other end is connected with the engine 36, so that the two-way energy transmission and conversion functions are realized between the two motors. When the vehicle is started, the power battery 31 provides energy, the boosting recovery motor 35 drives the engine 36 to start, and when the vehicle is braked, the boosting recovery motor 35 recovers the energy of the engine 36 and stores the energy into the power battery 31.

The control power supply 34 is connected with the vehicle control system 2 of the vehicle and provides working power supply for the vehicle control system 2 of the whole vehicle. The control power source 34 of the present invention has a much reduced capacity compared to conventional control power sources because the function of the control power source to provide the engine starting power source is eliminated. One promising value is that the capacity of the control power supply 34 can be reduced to 30Ah on a vehicle equipped with a 48V electrical network, whereas the capacity of the control power supply is 100Ah, which is common in the prior art.

The DC-DC conversion module 33 has one end connected to the power battery 31 and the other end connected to the control power source 34 (generally, 12V operating voltage for electronic devices on the vehicle), and performs two-way energy transmission and conversion between the two. When the capacity of the control power supply 34 is too low, the power battery 31 charges the control power supply 34 through the DC-DC conversion module 33; when the power battery 31 can not meet the cold start requirement of the engine 36 or before the whole vehicle is powered off, the control power supply 34 charges the power battery 31 through the DC-DC conversion module 33.

The control power supply 34 is connected to the vehicle control system 2, and is configured to supply power to the vehicle control system 2 (including other various electronic devices).

Fig. 3 shows a block diagram of the inside of the super capacitor module 311. The super capacitor module 311 is composed of a super capacitor 3111, a sensor 3112 and a super capacitor management module 3113. The super capacitor 3111 is composed of a plurality of super capacitor monomers and charge-discharge interfaces connected in series. The super capacitor has the characteristic of being capable of being charged/discharged by large current in the temperature range of (-40 to +70) DEG C, and the charging and discharging can be completed within a time of tens of seconds to several minutes. This allows for a low temperature engine start function, which reduces the performance requirements for the control power supply 34 and reduces the need for a 12V motor. The input end of the sensor 3112 is connected to the super capacitor 3111, and the output end is connected to the super capacitor management module 3113. Specifically, the sensor 3112 may include multiple and various types of sensors to transmit information such as voltage, current, and temperature of the super capacitor 3111 to the super capacitor management module 3113. Preferably, the sensor 3112 includes a voltage sensor, a current sensor, and a temperature sensor. The super capacitor management module 3113 collects information such as voltage, current, and temperature of the super capacitor 3111 through the sensor 3112, calculates capacity information and charge/discharge capability of the super capacitor, and controls the super capacitor 3111 to switch a charge or discharge state according to the capacity information and the charge/discharge capability. Meanwhile, the super capacitor management module 3113 is also interactive with the vehicle control system 2, and adjusts the working state of the super capacitor according to the overall working state of the entire vehicle.

Further, in a 48V hybrid system, according to the energy consumed in the process of starting the engine by the power-assisted recovery motor, the minimum requirement of energy storage of the super capacitor module can be determined. According to the definition of the LV148 standard on the voltage interval, the voltage range of the super capacitor module in the full-power operation and the reduced-power operation can be calculated. After the working voltage and the minimum energy storage requirement of the super capacitor module are determined, the capacitance value and the output current required by the super capacitor module can be determined by designing a certain allowance according to the relation between the energy storage of the capacitor and the voltage and the capacitance value and considering the self-discharge characteristic, the temperature influence, the initial state not full charge and other factors of the capacitor.

Further, the number and the integration mode of the super capacitor units are designed according to the conditions of the capacity, the mechanical parameters and the like of the super capacitor units, and the weight/volume of the super capacitor module is estimated to be within 2.5kg/2.5L and can be arranged at the position of an original 12V motor or a trunk by taking the factors of other accessory components such as a main relay, the shape of the units, the integration space redundancy, a module shell and the like into consideration, so that the space arrangement feasibility is high, and the super capacitor module can be fixed on a front cabin or a trunk bottom plate in a bolt connection mode. Because the service condition of super capacitor module is mostly low temperature or start for the first time, and ambient temperature is lower, operating time is shorter, and the thermal environment is not abominable, so the cooling method adopts the forced air cooling.

Further, in the prior art, there is a method for improving the low-temperature performance of the lithium battery by heating the lithium battery module by using the PTC thermal resistance. After the super capacitor module is introduced, the low-temperature performance of the lithium battery module is improved without a PTC thermal resistance heating mode, and the thermal safety of a system is improved.

Further, as can be easily inferred by those skilled in the art, lithium carbonate (Li) excellent in low-temperature performance is used₂CO₃) The battery can partially replace the super capacitor module.

To help deepen understanding, fig. 4 shows connection relationships between the modules in the hybrid system and the communication bus, the high-voltage bus, and the low-voltage bus. The high-voltage bus is connected with: the power-assisted recovery motor 35, the super capacitor module 311, the lithium battery module 312 and the DC-DC conversion module 33. The low-voltage bus is connected with: the power-assisted recovery motor 35, the super capacitor module 311, the lithium battery module 312, the DC-DC conversion module 33, the hybrid control unit 32, the control power supply 34 and the vehicle control system. The communication bus is connected with: the power-assisted recovery motor 35, the super capacitor module 311, the lithium battery module 312, the DC-DC conversion module 33, the hybrid control unit 32, the control power supply 34 and the vehicle control system. Preferably, the communication bus is a CAN industrial bus, the high-voltage bus is a power supply provided by the power battery 31 for driving the vehicle, the low-voltage bus is a power supply provided by the control power supply 34, and the control power supply 34 provides operating power to various electronic devices provided for the purposes of control, entertainment, comfort, safety, and the like. In the figure, a power battery 31, a hybrid control unit 32, a DC-DC conversion module 33 and a power recovery motor 35 are connected with the high-voltage bus; the power battery 31, the hybrid control unit 32, the DC-DC conversion module 33, the control power source 34, the power recovery motor 35 and the control system are connected to the low voltage bus and the communication bus.

As shown in fig. 5, the cold start method of the hybrid system includes the following steps:

s1, detecting the cold start of the engine by a control system of the vehicle;

and S9, finishing the starting of the engine.

And simultaneously, the step of charging the super capacitor module is also included after the engine is started or before the whole vehicle is powered off, and the aim is to constantly keep the capacitance of the super capacitor module for the next starting.

The step of charging the super capacitor module after the engine is started is as follows:

and S12, completing charging of the super capacitor module.

Before the whole vehicle is powered off, namely after the control system receives a whole vehicle power off request, the charging method further comprises the following steps of:

s11, controlling the power supply to charge the super capacitor module;

and S12, completing charging of the super capacitor module.

The auxiliary energy storage super capacitor module is added, on one hand, the function of part of control power supply is shared, and 12V motors are reduced compared with the traditional hybrid power system; on the other hand, the requirement of the whole vehicle on a control power supply is reduced through the bidirectional energy transfer function of the DC-DC conversion module. The comprehensive investigation results in reduced cost and saved space. And because the 12V motor has the defects of long starting time and large vibration noise in the starting process, the 12V motor is cancelled, and the pollution is reduced.

It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A hybrid powertrain system for powering a vehicle, comprising: the power recovery system comprises a power battery, a hybrid power control unit, a DC-DC conversion module, a control power supply, a power recovery motor and an engine;

2. The hybrid system of claim 1, wherein the super capacitor module comprises a super capacitor, a sensor, and a super capacitor management module; the input end and the output end of the sensor are respectively connected with the super capacitor and the super capacitor management module, and the super capacitor management module collects voltage, current and temperature information of the super capacitor through the sensor.

3. The hybrid system of claim 2, wherein the ultracapacitor comprises:

a plurality of series connected super capacitor units;

and the charge and discharge interface is connected with the plurality of serially connected super capacitor units, and the super capacitor management module controls the charge and discharge interface to perform charge and discharge conversion according to capacity information.

4. The hybrid system of claim 2, wherein the supercapacitor management module is further connected to the hybrid control unit, and the supercapacitor management module is controlled by the hybrid control unit to charge or discharge the supercapacitor.

5. The hybrid system of claim 3, wherein the charge-discharge interface is further coupled to the DC-DC conversion module.

6. The hybrid system of claim 1, wherein the voltage of the power cell is 48V.

7. The hybrid system according to claim 1, wherein the voltage of the control power source is 12V.

8. The hybrid system of claim 1, wherein the supercapacitor module is replaced with a lithium carbonate battery.

9. A cold start method of a hybrid system according to any one of claims 1 to 7, characterized by comprising the steps of:

s1, detecting the cold start of the engine by a control system of the vehicle;

and S9, finishing the starting of the engine.

10. The cold start method of a hybrid system of claim 9, further comprising the step of charging said super capacitor module after engine start-up or before vehicle power-down.

11. The cold start method of a hybrid powertrain of claim 9, further comprising, after the engine start is complete:

and S12, completing charging of the super capacitor module.

12. The cold start method of a hybrid power system according to claim 9, wherein the control system further comprises, after receiving a vehicle power-off request:

s11, controlling the power supply to charge the super capacitor module;

and S12, completing charging of the super capacitor module.