CN116872798A

CN116872798A - Vehicle battery self-heating system and method

Info

Publication number: CN116872798A
Application number: CN202311093770.0A
Authority: CN
Inventors: 蒋烨; 段崇伟; 高尚
Original assignee: Jingwei Hengrun Tianjin Research And Development Co ltd
Current assignee: Jingwei Hengrun Tianjin Research And Development Co ltd
Priority date: 2023-08-28
Filing date: 2023-08-28
Publication date: 2023-10-13

Abstract

The invention relates to the field of vehicle batteries, and discloses a vehicle battery self-heating system and a vehicle battery self-heating method. The system comprises a vehicle battery, a first switching device group, a second switching device group, a controller, a motor, a resonant capacitor and a switch, wherein the first switching device group comprises a first power switch and a second power switch, a first source drain electrode of the first power switch is connected with a first end of the battery, a second source drain electrode of the first power switch is connected with a third source drain electrode of the second power switch, a fourth source drain electrode of the second power switch is connected with a second end of the battery, and the second switching device group comprises a third power switch and a fourth power switch; the fifth source drain electrode of the third power switch is connected with the first end, the sixth source drain electrode is connected with the seventh source drain electrode of the fourth power switch, and the eighth source drain electrode of the fourth power switch is connected with the second end; the grid electrodes of the power switches are respectively connected with the controller, and the first side and the second side of the motor are respectively connected with the first switching device group and the second switching device group. Compared with the related art, the invention has the advantages of high self-heating efficiency of the battery, low cost and the like.

Description

Vehicle battery self-heating system and method

Technical Field

The invention relates to the technical field of vehicle batteries, in particular to a vehicle battery self-heating system and a vehicle battery self-heating method.

Background

Lithium ion batteries are an important component of electric automobiles, but the performance of lithium ion batteries is easily affected by temperature, and particularly in low-temperature environments, the performance of lithium ion batteries is obviously degraded. In order to solve the problem of performance degradation of the lithium ion battery in a low-temperature environment, the electric automobile is provided with a lithium battery heating system.

In the related art, the lithium battery heating system may be implemented by PTC (Positive Temperature Coefficient ) thermistor heating or heat pump heating, so as to increase the ambient temperature of the lithium ion battery. For the thermistor heating mode, the problem of low heating efficiency exists, and a large amount of lithium ion battery electric quantity is consumed by supplying power to the thermistor through the lithium ion battery, so that the endurance of the electric automobile is seriously influenced; the heat pump heating mode has the problems of complex structure and high implementation cost, and has low heating efficiency in a low-temperature environment.

Disclosure of Invention

In view of the above, the present invention can provide a vehicle battery self-heating system and method to solve the problems of low heating efficiency and the like in the related art.

In a first aspect, the present invention provides a vehicle battery self-heating system comprising:

A vehicle battery having a first end and a second end;

a first switching device group including a first power switch and a second power switch; the first source drain electrode of the first power switch is connected with the first end, the second source drain electrode of the first power switch is connected with the third source drain electrode of the second power switch, and the fourth source drain electrode of the second power switch is connected with the second end;

a second switching device group including a third power switch and a fourth power switch; the fifth source drain electrode of the third power switch is connected with the first end, the sixth source drain electrode of the third power switch is connected with the seventh source drain electrode of the fourth power switch, and the eighth source drain electrode of the fourth power switch is connected with the second end;

a controller; the first grid electrode of the first power switch, the second grid electrode of the second power switch, the third grid electrode of the third power switch and the fourth grid electrode of the fourth power switch are respectively connected with the controller;

a motor having a first side and a second side; the second source drain electrode and the third source drain electrode are respectively used for connecting the first side, and the sixth source drain electrode and the seventh source drain electrode are respectively used for connecting the second side;

a resonant capacitor having a third terminal and a fourth terminal; the third end is connected with the second side of the motor, and the sixth source drain electrode and the seventh source drain electrode are respectively connected with the fourth end;

A switch; the switch is connected in parallel with the resonant capacitor.

The motor in the self-heating system of the vehicle battery is equivalent to an inductor, a first switch device group is arranged between one end of the inductor and the vehicle battery, a second switch device group is arranged between the other end of the inductor and the vehicle battery, and the controller is used for controlling on-off of a first power switch and a second power switch in the first switch device group and a third power switch and a fourth power switch in the second switch device group, so that battery discharging current and battery charging current are formed between the vehicle battery and the inductor, heat is generated in the process that current flows through the internal resistance of the vehicle battery, and the self-heating purpose of the battery is realized. According to the LC oscillating circuit scheme formed by connecting the resonant capacitor with the equivalent inductance of the motor in series, the scheme can form larger heating current through the LC oscillating circuit, and has the advantages of smaller heating loss, higher heating efficiency and the like. According to the invention, the vehicle battery can be heated by adopting different battery heating modes under the condition that the control switch is in the closed state or the open state, so that the vehicle battery is heated by adopting different heating currents. Compared with a thermistor heating mode, the invention does not need to arrange an independent thermistor, but can heat the battery by the internal resistance heat release mode of the battery, so that the energy conversion efficiency is higher, and the heating efficiency is higher; compared with a heat pump heating mode, the self-heating scheme provided by the invention greatly reduces the influence of a low-temperature environment on the battery heating process, can heat the battery with high power under the low-temperature environment, and has the advantages of simpler overall structure and lower implementation cost. Therefore, the invention has the advantages of high self-heating efficiency of the battery, high energy utilization rate, low cost and the like.

In an alternative embodiment, the motor is a three-phase four-wire motor, the first side includes a phase a, a phase B and a phase C, and the second side is a neutral line of the three-phase four-wire motor;

the first power switch comprises a first sub-switch, a second sub-switch and a third sub-switch which are arranged in parallel, and the second power switch comprises a fourth sub-switch, a fifth sub-switch and a sixth sub-switch which are arranged in parallel;

the second source drain electrode of the first sub-switch and the third source drain electrode of the fourth sub-switch are respectively connected with the A phase, the second source drain electrode of the second sub-switch and the third source drain electrode of the fifth sub-switch are respectively connected with the B phase, and the second source drain electrode of the third sub-switch and the third source drain electrode of the sixth sub-switch are respectively connected with the C phase.

Based on the connection mode, the three-phase four-wire motor is used after three bridge arms of the three-phase four-wire motor are connected in parallel, the problem of torque generated when a vehicle battery is heated is avoided, and the working condition of the equivalent inductance of the three-phase four-wire motor is more stable, so that the heating efficiency of the vehicle battery is further improved.

In an alternative embodiment, the system further comprises:

the cooling liquid circulation pipeline comprises a first pipeline, a second pipeline and a third pipeline, and the cooling liquid circulation pipeline is filled with circulating flowing cooling liquid; the first pipeline is arranged at the side of the motor, the second pipeline is arranged at the side of the resonant capacitor, and the third pipeline is arranged at the side of the battery.

The invention can also recover the heat generated by the motor and the resonance capacitor, and transfer the recovered heat to the vehicle battery to further heat the vehicle battery.

In an alternative embodiment, the system further comprises:

and two ends of the direct current bus capacitor are respectively connected with the first end and the second end.

The invention can also stabilize the voltage at two sides of the first switch device group and the voltage at two sides of the second switch device group through the direct current bus capacitor, thereby ensuring the working stability of the first switch device group and the second switch device group and further ensuring the working reliability of the self-heating system of the vehicle battery.

In a second aspect, the present invention provides a method for self-heating a vehicle battery, applied to a controller in a self-heating system of a vehicle battery in one or more embodiments of the present invention, the method comprising:

determining a first switching frequency based on a voltage of a vehicle battery;

transmitting first control pulses to the first power switch and the fourth power switch according to the first switching frequency, and transmitting second control pulses to the second power switch and the third power switch according to the first switching frequency;

the difference between the phase of the first control pulse and the phase of the second control pulse is a first set value.

Based on the first control pulse and the second control pulse, the first power switch and the second power switch in the first switch device group and the third power switch and the fourth power switch in the second switch device group are controlled to be on-off, so that battery discharging current and battery charging current are formed between a vehicle battery and an inductor, heat is generated in the process that the current flows through the internal resistance of the vehicle battery, and the purpose of self-heating of the battery is achieved. Compared with a thermistor heating mode, the invention does not need to arrange an independent thermistor, but can heat the battery by the internal resistance heat release mode of the battery, so that the energy conversion efficiency is higher, and the heating efficiency is higher; compared with a heat pump heating mode, the self-heating scheme provided by the invention greatly reduces the influence of a low-temperature environment on the battery heating process, can heat the battery with high power under the low-temperature environment, and has the advantages of simpler overall structure and lower implementation cost. Therefore, the invention has the advantages of high self-heating efficiency of the battery, high energy utilization rate, low cost and the like.

In an alternative embodiment, a motor and a resonance capacitor are sequentially connected in series between the first switching device group and the second switching device group, and the resonance capacitor is connected with a switch in parallel;

Before determining the first switching frequency based on the voltage of the vehicle battery, further comprising:

determining a range of states of charge of a vehicle battery;

if the charge state of the vehicle battery is in a first preset range, the control switch is turned off, a third control pulse is sent to the first power switch and the fourth power switch according to a second switching frequency, and a fourth control pulse is sent to the second power switch and the third power switch according to the second switching frequency;

the first preset range is larger than the first preset value and smaller than the second preset value, and the difference value between the phase of the third control pulse and the phase of the fourth control pulse is a second set value;

if the state of charge of the vehicle battery is within the second preset range, controlling the switch to be closed, and returning to the step of determining the first switching frequency;

the second preset range is smaller than or equal to the first preset value or larger than or equal to the second preset value.

The invention can also heat the vehicle battery through the induction heating mode when the SOC of the battery is too high or the SOC is too low, and the mode avoids using excessive current to heat the vehicle battery when the SOC of the battery is too high or too low, thereby realizing the heating purpose and simultaneously ensuring the safety of the heating process of the vehicle battery. The invention can also provide higher heating current through the resonance heating mode when the battery SOC is moderate, so as to realize rapid heating of the vehicle battery; therefore, the invention can give consideration to both the heating speed of the vehicle battery and the heating safety of the vehicle battery.

In an alternative embodiment, before determining the range of the state of charge of the vehicle battery, the method further comprises:

receiving a self-heating instruction and state information of a vehicle battery, wherein the self-heating instruction and the state information comprise a state of charge, a voltage and a battery temperature, are sent by a battery management system, and the battery management system is used for collecting the state information of the vehicle battery;

according to the self-heating instruction and/or the battery temperature, judging whether to execute the step of determining the range of the charge state of the vehicle battery.

The invention can also reliably control whether the self-heating system of the vehicle starts the self-heating operation of the battery according to the self-heating instruction and/or the battery temperature.

In an alternative embodiment, the second switching frequency is half of the resonance frequency of the resonant unit formed by the equivalent inductance of the motor together with the resonance capacitance.

The second switching frequency determined by the mode can improve the resonance effect of the resonance unit so as to further improve the self-heating effect of the vehicle battery.

In an alternative embodiment, determining the first switching frequency based on the voltage of the vehicle battery includes:

where fL denotes a first switching frequency, ubat denotes a voltage of a vehicle battery, L denotes an inductance value of an equivalent inductance of the motor, and Irms denotes an effective value of a self-heating current to be achieved.

In an alternative embodiment, the second switching frequency is fLC;

wherein L represents the inductance value of the equivalent inductance of the motor, C _res Representing the capacitance value of the resonant capacitance.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural composition diagram of a vehicle battery self-heating system according to an embodiment of the present invention;

fig. 2 is a schematic structural composition diagram of another vehicle battery self-heating system according to an embodiment of the present invention;

fig. 3 is a schematic structural composition diagram of yet another vehicle battery self-heating system according to an embodiment of the present invention;

FIG. 4 is a flow chart of a method for self-heating a vehicle battery according to an embodiment of the invention;

FIG. 5 is a flow chart of another vehicle battery self-heating method according to an embodiment of the invention;

FIG. 6 is a flow chart of yet another vehicle battery self-heating method according to an embodiment of the present invention;

Fig. 7 is a waveform diagram of a motor three-phase winding total current waveform IL, a current waveform Ibat flowing through a battery, a motor output voltage waveform Vab in a resonant heating mode according to an embodiment of the invention;

fig. 8 is a waveform diagram of the motor three-phase winding total current waveform IL, the current waveform Ibat flowing through the battery, the motor output voltage waveform Vab in the induction heating mode according to the embodiment of the invention.

In the drawing the view of the figure,

100. a vehicle battery;

200. a first switching device group; 201. a first power switch; 202. a second power switch;

300. a second switching device group; 301. a third power switch; 302. a fourth power switch;

400. a controller;

500. a motor;

600. a resonance capacitor;

700. a switch;

801. a first pipeline; 802. a second pipeline; 803. a third pipeline;

900. DC bus capacitor.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The lithium ion battery has the advantages of high storage energy, high power density, low maintenance requirement, good charge-discharge cycle life and the like, meets the fast charge requirement, and becomes an indispensable part of the electric automobile. However, the characteristics of the lithium ion battery are greatly affected by the ambient temperature, and the performance of the lithium ion battery working in a low-temperature environment is obviously degraded, for example, when the ambient temperature is lower than 20 ℃, the lithium ion battery is charged and discharged for a long time, so that the service life of the lithium ion battery is greatly shortened, and the power output and the cruising duration of the electric automobile are affected. Some electric vehicles are then equipped with lithium battery heating systems, which can generally be implemented by a thermistor heating scheme or a heat pump heating scheme. For the thermistor heating scheme, a lithium ion battery is used for supplying power to the thermistor, and heat generated by the thermistor is used for heating the lithium ion battery; the greatest disadvantage of the method is that a large amount of battery electric energy consumed in the process of supplying power to the thermistor is only partially converted into heat energy for heating the lithium ion battery, the energy conversion efficiency is low, and the problem of low heating efficiency is caused. For the heat pump heating scheme, the heat pump heat release function is realized by the refrigeration principle of the air conditioner, so that the lithium ion battery is heated, but in the implementation process, the scheme is found to have low heating efficiency under the condition of low outdoor environment temperature, and the scheme also has the problems of complex overall structure, high implementation cost and the like.

As shown in fig. 1, the self-heating system for a vehicle battery provided in the embodiment of the invention includes, but is not limited to, a vehicle battery 100, a first switching device group 200, a second switching device group 300, a controller 400, a motor 500, a resonant capacitor 600, and a switch 700.

The vehicle battery 100 has a first end and a second end, and embodiments of the present invention relate to a vehicle battery 100 that may include, but are not limited to, a lithium ion battery; any vehicle battery 100 that is temperature dependent is within the scope of the present invention.

The vehicle battery 100 is used as a power battery of an electric vehicle to provide power for running of the electric vehicle. The first end of the vehicle battery 100 may be a positive electrode and the second end of the vehicle battery 100 may be a negative electrode.

The first switching device group 200 includes a first power switch 201 and a second power switch 202; the first source drain electrode of the first power switch 201 is connected to the first end, the second source drain electrode of the first power switch 201 is connected to the third source drain electrode of the second power switch 202, and the fourth source drain electrode of the second power switch 202 is connected to the second end.

It should be understood that the term "source drain" as used herein refers to a source or drain, and that for a power switch, where one source drain of the power switch is the source, the other source drain of the power switch is the drain. For example, the first source-drain electrode of the first power switch 201 is a source electrode, and the second source-drain electrode of the first power switch 201 is a drain electrode; alternatively, the first source-drain electrode of the first power switch 201 is a drain electrode, and the second source-drain electrode of the first power switch 201 is a source electrode.

The first power switch 201 in this embodiment may include one or more switching devices arranged in parallel, and the second power switch 202 may include one or more switching devices arranged in parallel.

The power switch device can be a Metal-Oxide-Semiconductor Field-Effect Transistor (Metal Oxide semiconductor field effect transistor).

The second switching device group 300 includes a third power switch 301 and a fourth power switch 302; the fifth source-drain electrode of the third power switch 301 is connected to the first end, the sixth source-drain electrode of the third power switch 301 is connected to the seventh source-drain electrode of the fourth power switch 302, and the eighth source-drain electrode of the fourth power switch 302 is connected to the second end.

The third power switch 301 of the present invention may include one or more power switching devices arranged in parallel, and the fourth power switch 302 may include one or more power switching devices arranged in parallel.

In this embodiment, the MOS transistor S41 represents the third power switch 301, and the MOS transistor S42 represents the fourth power switch 302.

Specifically, the first gate of the first power switch 201, the second gate of the second power switch 202, the third gate of the third power switch 301, and the fourth gate of the fourth power switch 302 according to the embodiment of the present invention are respectively connected to the controller 400, where the controller 400 in this embodiment is specifically a motor controller, and the motor controller has four different pins connected to the first gate, the second gate, the third gate, and the fourth gate in a one-to-one correspondence.

In the embodiment of the present invention, the grid electrodes of the power switches are respectively connected with corresponding pins on the controller, and the first side and the second side of the motor 500 are respectively connected with the first switching device group 200 and the second switching device group 300 correspondingly.

Specifically, the motor 500 has a first side and a second side; the second source drain electrode and the third source drain electrode are respectively used for connecting the first side, and the sixth source drain electrode and the seventh source drain electrode are respectively used for connecting the second side.

In this embodiment, the first power switch 201, the second power switch 202, the third power switch 301 and the fourth power switch 302 form an equivalent H-bridge topology, and the motor 500 is located in the middle of the equivalent H-bridge topology.

As shown in fig. 1, capacitor C _res Representing the resonant capacitance 600.

The resonant capacitor 600 has a third terminal and a fourth terminal, wherein the third terminal is connected to the second side of the motor 500, and the sixth source drain and the seventh source drain are respectively connected to the fourth terminal.

The LC oscillation circuit is constituted by the inductance equivalent to the motor 500 by the resonance capacitor 600, so that a large current can be formed in the vehicle battery 100, for example, the maximum current flowing through the vehicle battery 100 in the resonance heating mode shown in fig. 7 can reach an amplitude of 200A (ampere).

As shown in fig. 1, a switch 700 is connected in parallel with a resonant capacitor 600. Switch K1 represents switch 700. After the switch is disconnected, the self-heating system of the vehicle battery in the embodiment can work in a resonance heating mode, and an LC oscillating circuit formed by connecting the resonance capacitor with the equivalent inductance of the motor in series is used for heating the vehicle battery; after the switch is closed, the self-heating system of the vehicle battery in the embodiment can work in an induction heating mode, and the vehicle battery is heated through the equivalent inductance of the motor in the induction heating mode. It can be seen that the invention can also heat the vehicle battery by adopting different battery heating modes under the condition that the control switch is in the closed state or the open state, so that the vehicle battery is heated by adopting different heating currents.

The vehicle battery self-heating system shown in fig. 1 may operate as follows: the first control pulse is sent to the first power switch and the fourth power switch according to the first switching frequency, and the second control pulse is sent to the second power switch and the third power switch according to the first switching frequency, the motor 500 in this embodiment is equivalent to an inductor, the inductor is used as an energy storage element, the vehicle battery 100 is repeatedly discharged and charged in the process, and heat is generated when current generated in the discharging and charging process flows through the internal resistance of the vehicle battery 100, and the heat is used for heating the battery, so that the self-heating function of the vehicle battery is realized. The difference between the phase of the first control pulse and the phase of the second control pulse in this embodiment is a first set value, and the first preset value is 180 ° for example.

The motor in the vehicle battery self-heating system of the embodiment is equivalent to an inductor, a first switch device group is arranged between one end of the inductor and the vehicle battery, a second switch device group is arranged between the other end of the inductor and the vehicle battery, and the controller is used for controlling on-off of a first power switch and a second power switch in the first switch device group and a third power switch and a fourth power switch in the second switch device group, so that the vehicle battery is rapidly charged and discharged repeatedly in the process, battery discharging current and battery charging current are formed between the vehicle battery and the inductor, the battery discharging current and the battery charging current are particularly alternating current, and heat is generated in the process that the current flows through the internal resistance of the vehicle battery, and the purpose of self-heating of the battery is achieved.

In an alternative embodiment of the invention, the third control pulse is sent to the first power switch and the fourth power switch at the second switching frequency, and the fourth control pulse is sent to the second power switch and the third power switch at the second switching frequency. The resonance capacitor 600 is equivalent to the inductance of the motor 500 as an energy storage element, and rapidly discharges and charges the vehicle battery 100 repeatedly during this process, and heat is generated when current generated during the discharging and charging flows through the internal resistance of the vehicle battery 100, thereby realizing the self-heating function of the vehicle battery. The third control pulse and the fourth control pulse in this embodiment are pulses with a second preset duty cycle, for example, 50%.

According to the LC oscillating circuit scheme formed by connecting the resonant capacitor with the equivalent inductance of the motor in series, the LC oscillating circuit scheme can form larger heating current, and has the advantages of smaller heating loss, higher heating efficiency and the like.

Compared with the related art, the second switching device group and the resonant capacitor are added on the structure of the product, and the cost is increased slightly.

Compared with a thermistor heating mode, the invention does not need to arrange an independent thermistor, but can heat the battery by the internal resistance heat release mode of the battery, so that the energy conversion efficiency is higher, and the heating efficiency is higher; compared with a heat pump heating mode, the self-heating scheme provided by the invention greatly reduces the influence of a low-temperature environment on the battery heating process, can heat the battery with high power under the low-temperature environment, and has the advantages of simpler overall structure and lower implementation cost. Therefore, the invention has the advantages of high self-heating efficiency of the battery, high energy utilization rate, low cost and the like.

In some alternative implementations, the motor 500 of the present invention is a three-phase four-wire motor, with a first side comprising a phase a, a phase B, and a phase C, and a second side being the centerline of the three-phase four-wire motor.

The windings corresponding to the three-phase four-wire motor A, the windings corresponding to the three-phase four-wire motor B and the windings corresponding to the three-phase four-wire motor C are connected in parallel.

The first power switch 201 includes a first sub-switch, a second sub-switch, and a third sub-switch that are arranged in parallel, and the second power switch 202 includes a fourth sub-switch, a fifth sub-switch, and a sixth sub-switch that are arranged in parallel.

The second source drain electrode of the first sub-switch and the third source drain electrode of the fourth sub-switch are respectively connected with the A phase, the second source drain electrode of the second sub-switch and the third source drain electrode of the fifth sub-switch are respectively connected with the B phase, and the second source drain electrode of the third sub-switch and the third source drain electrode of the sixth sub-switch are respectively connected with the C phase. Based on the connection mode, the embodiment of the invention realizes that three bridge arms (the winding corresponding to the A, the winding corresponding to the three-phase four-wire motor B and the winding corresponding to the three-phase four-wire motor C) are connected in parallel and then used, so that the problem of torque generated when a vehicle battery is heated is avoided, the working condition of the equivalent inductance of the three-phase four-wire motor is more stable and balanced, the specific value of the equivalent inductance is hardly changed, and the heating efficiency of the vehicle battery is further improved.

In this embodiment, the first sub-switch, the second sub-switch, the third sub-switch, the fourth sub-switch, the fifth sub-switch and the sixth sub-switch are all power switching devices, and are respectively one MOS transistor. Referring to fig. 1 to 3, MOS transistor S11 represents a first sub-switch, MOS transistor S21 represents a second sub-switch, MOS transistor S31 represents a third sub-switch, MOS transistor S12 represents a fourth sub-switch, MOS transistor S22 represents a fifth sub-switch, and MOS transistor S32 represents a sixth sub-switch.

In this embodiment, the motor controller has eight different pins connected to the first gate of the first sub-switch, the first gate of the second sub-switch, the first gate of the third sub-switch, the second gate of the fourth sub-switch, the second gate of the fifth sub-switch, the second gate of the sixth sub-switch, the third gate of the third power switch 301, and the fourth gate of the fourth power switch 302 in a one-to-one correspondence. As for the resonance capacitor 600, the neutral line of the three-phase four-wire motor is connected in series with the resonance capacitor 600 and the resonance capacitor 600 is connected in parallel through the switch 700.

Therefore, the embodiment provides a power battery self-heating system based on the three-phase four-wire motor by taking the equivalent inductance of the three-phase four-wire motor as an energy storage element.

Based on the connection mode, the three bridge arms are connected in parallel and then used, the problem of torque generated when the vehicle battery is heated is avoided, and the working condition of the equivalent inductance of the three-phase four-wire motor is more stable, so that the heating efficiency of the vehicle battery is further improved.

In some alternative embodiments, as shown in fig. 2, the vehicle battery self-heating system further includes a coolant circulation line.

The coolant circulation pipeline in this embodiment is the last coolant circulation pipeline of electric automobile, is provided with the water pump on the coolant circulation pipeline, and this water pump can be used to drive coolant circulation flow in the pipeline, and the coolant can be water, and this embodiment utilizes coolant circulation pipeline to realize heat recovery function.

The cooling liquid circulation pipeline comprises a first pipeline 801, a second pipeline 802 and a third pipeline 803, and the cooling liquid circulation pipeline is filled with circulating cooling liquid; the first pipeline 801 is arranged beside the motor 500, the second pipeline 802 is arranged beside the resonant capacitor 600, and the third pipeline 803 is arranged beside the battery.

The capacitor water cooling plate is disposed on the resonance capacitor 600, the second pipeline 802 may be tightly attached to the capacitor water cooling plate, and in the working process of the resonance capacitor 600, generated heat is transferred to the cooling liquid in the second pipeline 802 through the capacitor water cooling plate, and the circulating cooling liquid can transfer heat to the battery. Similarly, since the first pipeline 801 is disposed beside the motor 500 in this embodiment, during operation of the motor 500, heat generated by the motor 500 is transferred to the battery through the cooling liquid in the first pipeline 801.

Based on the cooling liquid circulation pipeline, the heat generated by the motor and the resonance capacitor is transferred to the vehicle battery, so that the motor and the resonance capacitor can be used for recovering the heat generated by the motor and the resonance capacitor, and the recovered heat is transferred to the vehicle battery, and further the vehicle battery is heated.

In some alternative embodiments, as shown in fig. 3, the vehicle battery self-heating system further includes a dc bus capacitor 900. Specifically, two ends of the dc bus capacitor 900 are connected to the first end and the second end respectively.

With reference to FIG. 3, capacitor C _bus The dc bus capacitance 900 is shown.

According to an embodiment of the present invention, a vehicle battery self-heating method embodiment is provided, and although a logic sequence is shown in the flowchart, in some cases the steps shown or described may be performed in a different order than that shown or described herein. The specific structure of the vehicle battery self-heating system suitable for implementing the vehicle battery self-heating method according to the embodiment of the present invention is described in detail in the present specification, and will not be described here again.

In this embodiment, a self-heating method for a vehicle battery is provided, which may be used for the controller in the self-heating system for a vehicle battery, and fig. 4 is a flowchart of the self-heating method for a vehicle battery according to an embodiment of the present invention, as shown in fig. 4, and the flowchart includes the following steps:

Step S110 determines a first switching frequency based on a voltage of a vehicle battery.

Step S120, a first control pulse is sent to the first power switch and the fourth power switch according to the first switching frequency, and a second control pulse is sent to the second power switch and the third power switch according to the first switching frequency; the difference between the phase of the first control pulse and the phase of the second control pulse is a first set value. In this embodiment, the first control pulse and the second control pulse are pulses with a first preset duty cycle, for example, 50%.

In one or more embodiments of the present invention, the first set point is 180 ° (degrees), and it can be seen that the first control pulse sent to the first power switch and the fourth power switch of the present invention is 180 ° out of phase with the second control pulse sent to the second power switch and the third power switch.

Based on the first control pulse and the second control pulse, the embodiment of the invention controls the on-off of the first power switch and the second power switch in the first switch device group and the third power switch and the fourth power switch in the second switch device group, so that battery discharging current and battery charging current are formed between the vehicle battery and the inductor, and heat is generated in the process that the current flows through the internal resistance of the vehicle battery, thereby realizing the purpose of self-heating of the battery. Compared with a thermistor heating mode, the invention does not need to arrange an independent thermistor, but can heat the battery by the internal resistance heat release mode of the battery, so that the energy conversion efficiency is higher, and the heating efficiency is higher; compared with a heat pump heating mode, the self-heating scheme provided by the invention greatly reduces the influence of a low-temperature environment on the battery heating process, can heat the battery with high power under the low-temperature environment, and has the advantages of simpler overall structure and lower implementation cost. Therefore, the invention has the advantages of high self-heating efficiency of the battery, high energy utilization rate, low cost and the like.

In this embodiment, a motor and a resonance capacitor are sequentially connected in series between a first switching device group and a second switching device group, and the resonance capacitor is connected with a switch in parallel; the motor in this embodiment may be a three-phase four-wire motor, and this embodiment can provide a power battery self-heating method based on the three-phase four-wire motor. Fig. 5 is a flowchart of a self-heating method of a vehicle battery according to an embodiment of the present invention, as shown in fig. 5, the flowchart including the steps of:

step S101, determining a range of a state of charge of a vehicle battery.

The state of charge of the vehicle battery represents the vehicle battery SOC (State Of Charge).

The embodiment assumes that the inductance value of the equivalent inductance after the three-phase windings of the three-phase four-wire motor are connected in parallel is L, and the vehicle battery voltage is Ubat.

Step S102, judging whether the charge state of a vehicle battery is in a first preset range; the first preset range is larger than the first preset value and smaller than the second preset value, and the difference value between the phase of the third control pulse and the phase of the fourth control pulse is a second set value.

The first preset value is denoted as soc_a, the second preset value is denoted as soc_b, and the specific value can be set according to the actual situation of the vehicle battery.

Step S103, if the state of charge of the vehicle battery is within the first preset range, the control switch is turned off.

If the battery SOC_a is less than or equal to SOC and less than or equal to SOC_b, the control switch is turned off. After the control switch is turned off in the embodiment, the self-heating method of the vehicle battery of the embodiment operates in the resonance heating mode, which includes the following step S104.

In this embodiment, after the control switch is turned off, the self-heating method of the vehicle battery of the present invention operates in the resonant heating mode, i.e. step S104 described below.

As shown in fig. 1 to 3, after the switch K1 is turned off, the equivalent inductance and the resonance capacitance C after the three-phase windings of the three-phase four-wire motor are connected in parallel _res An LC resonant network is constructed as a load for an equivalent H-bridge and then a resonant heating mode can be entered.

The first power switch 201, the second power switch 202, the third power switch 301, and the fourth power switch 302 are shown to form an equivalent H-bridge.

Step S104, transmitting third control pulses to the first power switch and the fourth power switch according to the second switching frequency, and transmitting fourth control pulses to the second power switch and the third power switch according to the second switching frequency. The third control pulse and the fourth control pulse in this embodiment are pulses having a second preset duty cycle, for example, 50%. In one or more embodiments of the present invention, the second set point is 180 ° (degrees), and it can be seen that the third control pulse sent to the first and fourth power switches of the present invention is 180 ° out of phase with the fourth control pulse sent to the second and third power switches.

In this embodiment, the second switching frequency is assumed to be fLC.

In some alternative embodiments, the second switching frequency in this embodiment is half the resonant frequency of the resonant unit formed by the equivalent inductance of the motor together with the resonant capacitance.

The second switching frequency isWherein L represents the inductance value of the equivalent inductance of the motor, C _res Representing the capacitance value of the resonant capacitance.

Wherein fLC is the inductance L of the equivalent inductance of the motor winding and the capacitance C of the resonant capacitor _res 1/2 of the resonant frequency of the resonant cells formed after the series connection, fLC, can be determined by calculation or off-line calibration; in particular, the method comprises the steps of,

in this embodiment, the lead resistance and loss are ignored, and the dc bus capacitor C is ignored _bus Ideally, the total current of the motor winding in the resonant heating mode of this embodiment is iL (t).

Where ω represents the resonance frequency of the resonance unit and t represents time.

The second switching frequency determined in the mode can improve the resonance effect of the resonance unit, so that the self-heating effect of the vehicle battery is further improved.

By combining the modes, the self-locking deviceThe heating current can reach the expected effective value Ih of the maximum self-heating current _max The mode can use a large heating current to self-heat the vehicle battery, and is suitable for quickly heating the battery under the condition of moderate battery SOC.

In addition, if the maximum self-heating current effective value Ih required to be achieved is known in the design stage _max The capacitance value of the resonant capacitor in the circuit can be calculated

As shown in fig. 7, the waveform of the total current waveform IL of the three-phase winding of the motor, the waveform of the current waveform Ibat flowing through the battery, and the waveform of the output voltage waveform Vab of the motor in the resonance heating mode are shown, wherein the abscissa indicates t (time) in seconds and the ordinate includes IL, ibat and Vab. As illustrated, the motor output voltage waveform Vab of the present embodiment represents output voltage waveforms of the parallel arms S11& S21& S31& S12& S22& S32 and S41& S42. As can be seen from fig. 7, the present invention is capable of self-heating the vehicle battery with a large self-heating current when operating in this resonant heating mode.

Step S105, if the state of charge of the vehicle battery is within the second preset range, controlling the switch to be closed, and returning to the step of determining the first switching frequency; the second preset range is smaller than or equal to the first preset value or larger than or equal to the second preset value.

If the battery SOC is not less than SOC_a or not less than SOC_b, the control switch is closed. After the control switch is turned on in the embodiment, the self-heating method of the vehicle battery of the embodiment operates in the induction heating mode, and includes the following steps S110 and S120.

In the embodiment of the invention, the first switching frequency is denoted by fL, and the first switching frequency fL is determined specifically by the voltage of the vehicle battery, the inductance value of the equivalent inductance of the motor, and the effective value of the self-heating current to be achieved.

Where Ubat represents the voltage of the vehicle battery, L represents the inductance value of the equivalent inductance of the motor, irms represents the effective value of the self-heating current that needs to be reached.

As shown in fig. 1 to 3, after the switch K1 is closed, only the three-phase windings of the three-phase four-wire motor are used as the load of the equivalent H-bridge, and the present embodiment can then enter the induction heating mode, unlike the resonance heating mode.

In one or more embodiments of the present invention, the first set point is 180 °, and it can be seen that the phase between the first control pulse sent to the first power switch and the fourth power switch and the second control pulse sent to the second power switch and the third power switch is 180 °.

In this embodiment, the lead resistance and loss are ignored, and the dc bus capacitor C is ignored _bus Ideally, the total current of the motor winding in the inductive heating mode of this embodiment is iLL (t).

Where t0 represents the current period start time, fL represents the first switching frequency.

In the inductive heating mode, the equivalent inductance is denoted as resonant inductance LL, and the current amplitude across the resonant inductance of this embodiment is denoted ILL.

Where L represents the inductance value of the resonant inductance LL and Irms represents the effective value of the self-heating current.

When the SOC of the battery is too high or too low, the battery is not suitable to be subjected to alternating-current self-heating by adopting high current, and the above formula shows that the embodiment can adjust the effective value Irms of the self-heating current by adjusting fL, and reduce the effective value of the self-heating current by increasing the switching frequency, so that the self-heating safety of the vehicle battery is ensured.

In addition, if the effective value Irms of the self-heating current required to be achieved in the inductive heating mode is known in the design stage, the switching frequency can be calculated The effective value Irms of the self-heating current can be determined according to the battery SOC in an off-line calibration mode, and it is required to ensure that the vehicle battery is not overcharged or overdischarged.

As shown in fig. 8, the waveform of the total current waveform IL of the three-phase winding of the motor, the waveform of the current waveform Ibat flowing through the battery, and the waveform of the output voltage waveform Vab of the motor in the induction heating mode are shown, wherein the abscissa indicates t (time) in seconds and the ordinate includes IL, ibat and Vab. As illustrated, the motor output voltage waveform Vab of the present embodiment represents output voltage waveforms of the parallel arms S11& S21& S31& S12& S22& S32 and S41& S42. As can be seen from fig. 8, when operating in the inductive heating mode, the present invention can achieve a suitable or even small self-heating current of the battery by adjusting the switching frequency.

Whether a resonance heating mode or an induction heating mode is adopted, the self-heating method for the vehicle battery provided by the invention further comprises the following steps: monitoring the real-time temperature of the vehicle battery, and stopping self-heating if the real-time temperature of the vehicle battery reaches the expected temperature Tc; and/or, receiving a heating stop instruction from the upper controller, and stopping self-heating, wherein the heating stop instruction of the upper controller can be generated based on a command issued by a driver to stop heating. In this embodiment, the process of stopping self-heating by the vehicle controller includes: the control of the first power switch, the second power switch and the third power switch to be turned off may specifically include control of the MOS transistor S11, the MOS transistor S21, the MOS transistor S31, the MOS transistor S12, the MOS transistor S22 and the MOS transistor S32 to be turned off; and the switch K1 can be closed, and the motor can execute the function of the motor in a three-wire four-wire system mode at the moment so as to meet the requirement of the electric automobile for entering a normal running mode. In this way, the present invention is also able to stop self-heating of the vehicle battery according to the actual battery temperature or the user's demand.

The invention can also control the switch to be in a closed state or an open state according to the battery SOC, and heat the vehicle battery through the induction heating mode when the switch is in the closed state, and heat the vehicle battery through the resonance heating mode when the switch is in the open state, wherein heating currents in the two different heating modes are different, for example, the maximum current flowing through the vehicle battery in the resonance heating mode shown in fig. 7 can reach 200A, for example, the maximum current flowing through the vehicle battery in the induction heating mode shown in fig. 8 can reach 40A, so that the aim of adjusting the self-heating current of the battery according to the battery SOC can be realized, and the safety of the battery can be further effectively ensured.

In summary, the invention can flexibly adjust the self-heating current of the battery according to the SOC and the requirement of the vehicle battery, realize higher heating rate with larger heating current under the condition of the safety of the SOC of the vehicle battery, and realize safer heating of the vehicle battery with controllable heating current when the SOC of the vehicle battery is too high or too low.

In this embodiment, a self-heating method for a vehicle battery is provided, which may be used for the controller in the self-heating system for a vehicle battery, and fig. 6 is a flowchart of the self-heating method for a vehicle battery according to an embodiment of the present invention, as shown in fig. 6, and the flowchart includes the following steps:

Step S100, receiving a self-heating instruction and state information of a vehicle battery sent by a battery management system, wherein the state information includes a state of charge, a voltage and a battery temperature, and the battery management system is used for collecting the state information of the vehicle battery.

The battery management system according to the present invention, specifically BMS (Battery Management System), reads the battery temperature Tb and the battery SOC of the vehicle through the BMS, determines whether there is a self-heating demand from the driver by receiving the current command from the upper controller, and generates the self-heating command according to the current command. The upper controller may be, for example, a VCU (Vehicle Control Unit ), and directly receives a control command sent by a driver through the upper controller. The BMS in this embodiment issues a self-heating instruction, a current vehicle battery temperature Tb, an acquired vehicle battery voltage Ubat, and a battery SOC to the motor controller, which selects a battery heating mode according to the battery SOC.

The self-heating instruction comprises a heating start instruction and a heating close instruction.

The embodiment of the invention can realize the self-heating function of the vehicle battery on the electric automobile under the condition of parking the electric automobile.

Step S200, determining whether to execute the step of determining the range of the state of charge of the vehicle battery according to the self-heating command and/or the battery temperature.

If the self-heating instruction is a heating start instruction and/or the battery temperature is less than or equal to the first preset temperature (Tb is less than or equal to Tmin), executing step S101 to realize the start of the battery self-heating system. If the self-heating command is a heating-off command and/or the battery temperature is greater than the first preset temperature (Tb & gt Tmin), returning to step S100.

After the battery self-heating system is started, the present embodiment can heat the vehicle battery to the desired temperature Tc, and the present invention can modify the desired temperature Tc and/or the first preset temperature Tmin by the instructions of the upper controller.

The first preset temperature is set according to the actual situation, for example, tmin= -5 ℃ (celsius degree), and the expected temperature may also be set according to the actual situation, for example, tc=5 ℃.

The embodiment of the invention can also reliably control whether the self-heating system of the vehicle starts the self-heating operation of the battery according to the self-heating instruction and/or the battery temperature.

Step S101, determining a range of a state of charge of a vehicle battery. The specific implementation process of this step S101 is already described in detail in this specification, and will not be described here again.

Step S102, judging whether the charge state of the vehicle battery is in a first preset range.

In this embodiment, if the state of charge of the vehicle battery is within the first preset range, the battery heating mode selected by the motor controller according to the battery SOC is a resonant heating mode, including the following steps S103 and S104; if the state of charge of the vehicle battery is not within the first preset range, the motor controller selects the battery heating mode according to the battery SOC to be the induction heating mode, including steps S105, S110 and S120 described below.

Step S103, if the state of charge of the vehicle battery is within the first preset range, the control switch is turned off. The specific implementation process of step S103 is already described in detail in this specification, and will not be described here again.

Step S104, transmitting third control pulses to the first power switch and the fourth power switch according to the second switching frequency, and transmitting fourth control pulses to the second power switch and the third power switch according to the second switching frequency; the first preset range is larger than the first preset value and smaller than the second preset value, and the difference value between the phase of the third control pulse and the phase of the fourth control pulse is a second set value. The specific implementation process of step S104 is already described in detail in this specification, and will not be described here again.

Step S105, if the state of charge of the vehicle battery is within the second preset range, controlling the switch to be closed, and returning to the step of determining the first switching frequency; the second preset range is smaller than or equal to the first preset value or larger than or equal to the second preset value. The specific implementation process of step S105 is already described in detail in this specification, and will not be described here again.

Step S110 determines a first switching frequency based on a voltage of a vehicle battery. The specific implementation process of step S110 is already described in detail in this specification, and will not be described here again.

Step S120, a first control pulse is sent to the first power switch and the fourth power switch according to the first switching frequency, and a second control pulse is sent to the second power switch and the third power switch according to the first switching frequency; the difference between the phase of the first control pulse and the phase of the second control pulse is a first set value. The specific implementation process of step S120 is already described in detail in this specification, and will not be described here again.

In the description of the present specification, a description referring to the terms "present embodiment," "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

Although embodiments of the present invention have been described in connection with the accompanying drawings, various modifications and variations may be made by those skilled in the art without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope of the invention as defined by the appended claims.

Claims

1. A vehicle battery self-heating system, the system comprising:

a vehicle battery (100) having a first end and a second end;

a first switching device group (200) comprising a first power switch (201) and a second power switch (202); a first source-drain electrode of the first power switch (201) is connected with the first end, a second source-drain electrode of the first power switch (201) is connected with a third source-drain electrode of the second power switch (202), and a fourth source-drain electrode of the second power switch (202) is connected with the second end;

A second switching device group (300) comprising a third power switch (301) and a fourth power switch (302); a fifth source-drain electrode of the third power switch (301) is connected with the first end, a sixth source-drain electrode of the third power switch (301) is connected with a seventh source-drain electrode of the fourth power switch (302), and an eighth source-drain electrode of the fourth power switch (302) is connected with the second end;

a controller (400); a first grid electrode of the first power switch (201), a second grid electrode of the second power switch (202), a third grid electrode of the third power switch (301) and a fourth grid electrode of the fourth power switch (302) are respectively connected with the controller (400);

a motor (500) having a first side and a second side; the second source drain electrode and the third source drain electrode are respectively used for connecting the first side, and the sixth source drain electrode and the seventh source drain electrode are respectively used for connecting the second side;

a resonant capacitor (600) having a third terminal and a fourth terminal; wherein the third end is connected with the second side of the motor (500), and the sixth source drain electrode and the seventh source drain electrode are respectively connected with the fourth end;

a switch (700); the switch is connected in parallel with the resonance capacitor (600).

2. The self-heating system of a vehicle battery according to claim 1, wherein,

the motor (500) is a three-phase four-wire motor, the first side comprises an A phase, a B phase and a C phase, and the second side is a central line of the three-phase four-wire motor;

the first power switch (201) comprises a first sub-switch, a second sub-switch and a third sub-switch which are arranged in parallel, and the second power switch (202) comprises a fourth sub-switch, a fifth sub-switch and a sixth sub-switch which are arranged in parallel;

3. The vehicle battery self-heating system according to claim 1 or 2, characterized in that the system further comprises:

a cooling liquid circulation pipeline, which comprises a first pipeline (801), a second pipeline (802) and a third pipeline (803), wherein the cooling liquid circulation pipeline is filled with circulating cooling liquid;

the first pipeline (801) is arranged beside the motor (500), the second pipeline (802) is arranged beside the resonance capacitor (600), and the third pipeline (803) is arranged beside the vehicle battery (100).

4. The vehicle battery self-heating system according to claim 1 or 2, characterized in that the system further comprises:

and the two ends of the direct current bus capacitor (900) are respectively connected with the first end and the second end.

5. A vehicle battery self-heating method, characterized by being applied to the controller in the vehicle battery self-heating system according to any one of claims 1 to 4, the method comprising:

determining a first switching frequency based on a voltage of the vehicle battery;

transmitting a first control pulse to the first power switch and the fourth power switch according to the first switching frequency, and transmitting a second control pulse to the second power switch and the third power switch according to the first switching frequency;

6. The method according to claim 5, wherein the motor and the resonance capacitor are sequentially connected in series between the first switching device group and the second switching device group, the resonance capacitor being connected in parallel to a switch;

before the determining the first switching frequency based on the voltage of the vehicle battery, the method further includes:

Determining a range of states of charge of the vehicle battery;

if the state of charge of the vehicle battery is within a first preset range, the switch is controlled to be turned off, a third control pulse is sent to the first power switch and the fourth power switch according to the second switching frequency, and a fourth control pulse is sent to the second power switch and the third power switch according to the second switching frequency;

the first preset range is larger than a first preset value and smaller than a second preset value, and the difference value between the phase of the third control pulse and the phase of the fourth control pulse is a second set value;

if the state of charge of the vehicle battery is within a second preset range, controlling the switch to be closed, and returning to the step of determining the first switching frequency;

7. The method of self-heating a vehicle battery according to claim 6, wherein prior to said determining the range of state of charge of the vehicle battery, further comprising:

receiving a self-heating instruction and state information of the vehicle battery, wherein the state information comprises the state of charge, the voltage and the battery temperature, and the battery management system is used for acquiring the state information of the vehicle battery;

And judging whether to execute the step of determining the range of the charge state of the vehicle battery according to the self-heating instruction and/or the battery temperature.

8. The vehicle battery self-heating method according to claim 6 or 7, characterized in that the second switching frequency is half of a resonance frequency of a resonance unit formed by an equivalent inductance of the motor together with the resonance capacitance.

9. The method of self-heating a vehicle battery according to claim 5, wherein said determining a first switching frequency based on a voltage of said vehicle battery comprises:

where fL represents the first switching frequency, ubet represents the voltage of the vehicle battery, L represents the inductance value of the equivalent inductance of the motor, irms represents the effective value of the self-heating current that needs to be reached.

10. The vehicle battery self-heating method according to claim 6, wherein the second switching frequency is fLC;