CN106711519A - Safety system of electric car battery unit structure, and control method thereof - Google Patents

Abstract

The invention provides a safety system of an electric car battery unit structure, and a control method thereof. The safety system comprises a battery system, a driving circuit, a relay, a sensor, a controller and a car state estimator. The battery system comprises a battery box layer, a battery bag layer and a battery module layer. Turn-on or cut-off of battery units in the charge/discharge process guarantees the consistence of the battery units; transformation of the connecting mode of the battery system in the parking process reduces the voltage of the battery system and prevents latent high voltage dangers; and connection of battery cells is broken when battery liquid leakage, insulation damage or local short circuit appears in the running process in order to prevent the high voltage dangers, and some battery units are selectively cut off in the bumping process according to the bumping degree in order to prevent the high voltage dangers.

Description

Safety system and control method for electric vehicle battery pack unit structure

technical field

The invention belongs to the field of drive control systems for electric vehicles, and in particular relates to a safety system and a control method for improving the safety and practicability of battery packs by means of on-off between battery pack units of electric cars.

Background technique

With the popularization and application of new energy technologies, the number of pure electric vehicles in road public transportation systems has increased rapidly. During the demonstration operation process, the problems exposed are also worthy of attention.

First of all, the problem of inconsistency. At present, the power battery of electric vehicles is generally composed of multiple cells called large-capacity single cells connected in series. Due to uneven materials in the process of manufacturing and differences in battery temperature and life during use, there must be inconsistencies in parameters such as internal resistance, terminal voltage, and capacity among individual batteries, thereby reducing the use level of the battery pack and seriously Affect the performance of electric vehicles and endanger the safety of electric vehicles. Therefore, it is very necessary to study an effective equalization charging method to make up for the inconsistency of the battery performance during the use of the battery, to maximize the utility of the power battery, to prolong the service life of the battery, and to increase the safety of the electric vehicle.

In practical applications, large-scale power battery systems are composed of multiple battery cells in series to ensure sufficient output voltage. Due to the constraints of the production process, there are inevitably inconsistencies between the individual cells. This inconsistency will gradually widen, resulting in a vicious circle, seriously affecting the performance and life of the power battery.

In a collision accident, the spontaneous combustion of the vehicle body due to the insulation failure of the high-voltage battery pack or the internal short circuit will seriously endanger the personal safety of passengers and drivers. In particular, in a collision accident, when the inner box of the battery is damaged, the stress of the battery cells is too large, resulting in an internal short circuit of the cells and leakage of electrolyte. Therefore, it is of great significance to study the collision safety control of the high-voltage power battery system of electric vehicles for the safety improvement and widespread promotion of electric vehicles.

During the application process, the battery pack experienced battery leakage, insulation damage, and local short circuit. After repeated use, safety hazards such as spontaneous combustion occurred. Therefore, when an abnormality of the battery pack is detected, the voltage level can be reduced by changing the connection mode of the battery cells between the battery packs to avoid potential risks.

During the parking process, although the battery system does not work and the accessory equipment of the vehicle is powered by a low-voltage power supply, there are also potential safety risks. At this time, changing the connection method of the battery pack and lowering the voltage level can effectively avoid potential safety risks.

Contents of the invention

In order to solve the deficiencies of the prior art, the object of the present invention is to provide a safety system and control method for the battery pack unit structure of an electric vehicle, so that it can maintain the performance requirements of the vehicle according to the driving conditions of the electric vehicle and the vehicle status. Next, the output of electric energy and the safety of the battery pack are guaranteed by controlling the on-off of the battery module.

In order to achieve the above object, the present invention provides a safety system for a battery pack unit structure of an electric vehicle, the safety system includes a battery system, a driving circuit, a relay, a sensor, a controller and a vehicle state estimator.

The battery system includes a battery box layer composed of several battery packs connected in series, a battery pack layer composed of several battery modules, a battery module layer and a battery cell layer composed of several battery cells. Relays are used to control the on and off of battery packs, battery modules and battery cells. Sensors are used to sense various operating conditions of the vehicle. The controller controls the on and off of the relay, adjusts the on and off of the battery module and the battery unit, and the output voltage of the battery pack according to the vehicle's operating conditions, the information fed back by the sensor and the battery system.

As a further description of the safety system of the present invention, preferably, the positive electrode of each battery pack is connected in series with the first relay, and the battery pack and the relay connected in series with the battery pack are connected in parallel with the second relay, and each battery pack can be switched on and disconnect.

As a further description of the safety system of the present invention, preferably, each battery module is placed side by side with the same polarity, and the negative pole of the next battery module is connected to the first relay, and then passes through the second relay and the adjacent battery module The first relay of the negative pole is connected, and the positive pole of the adjacent battery module is also connected through the third relay; the fourth relay is bridged between the second relay and the positive pole of the negative poles of two adjacent battery modules. More preferably, the battery modules can be connected in parallel or in series, and each battery module can be turned on and off.

As a further description of the safety system of the present invention, preferably, each battery unit is placed side by side with the same polarity, and the negative pole of the battery unit is connected to the first relay; then passes through the second relay and the adjacent battery module The first relay at the negative pole is connected, and the positive poles of the adjacent battery cells are also connected through the third relay; the fourth relay is bridged between the second relay and the positive poles of the negative poles of two adjacent battery cells. More preferably, the battery units can be connected in parallel or in series, and each battery unit can be turned on and off.

As a further description of the safety system of the present invention, preferably, the sensors include a vehicle speed sensor, an acceleration sensor, a vehicle height sensor, a roll angle sensor, a yaw angle sensor, a rotation angle sensor, a motor detection sensor, a battery voltage sensor, a battery Current sensor, battery insulation sensor, smoke sensor.

In addition, another object of the present invention is to provide a control method for the safety system, the control method includes the following steps: a) The vehicle sensor senses the operating condition of the vehicle, and converts it into an electrical signal and sends it to the vehicle state estimator ; b) the vehicle state estimator obtains the information sent by the vehicle sensor, obtains the state signal of the vehicle, and transmits the state signal to the controller; and c) the controller receives the state signal sent by the vehicle state estimator and the feedback from the battery system Information to control the on and off control of the drive circuit to the relay in the battery system.

Among them, c-1) When the battery pack is in the discharge process, the battery system receives the discharge instruction information from the controller, and according to the current energy demand, closes the relay to discharge all the batteries; when it is detected that K discharged batteries have reached the discharge The voltage thresholds V _o1 and V _o1 are determined according to the variation range of the battery voltage and the discharge characteristics of the battery cells. The relays (3) of K batteries are disconnected to stop charging, and the remaining batteries are still discharged until all batteries are discharged. Voltage threshold V _o1 ; then discharge all the batteries in the next stage; c-2) When the battery pack is in the charging state, close the relay to charge all the batteries according to the voltage of the battery module or battery unit fed back, When it is detected that K batteries have reached the charging voltage threshold V _i1 , V _i1 is determined according to the battery voltage variation range and charging characteristics of the battery cells, the relays of K batteries are disconnected to stop charging, and the remaining batteries are still charged. Until all the batteries reach the charging voltage threshold V _i1 ; then charge all the batteries for the next stage; c-3) When the vehicle is in the running state, first perform the vehicle running state detection; if the vehicle collision is detected, enter the collision control state; the battery system performs ladder discharge according to the information provided by the controller; when the voltage of the battery pack reaches the threshold value set for operation, the vehicle enters a limp state, and the battery pack is discharged in steps according to its own discharge capacity; c-4) when When the vehicle is in a parked state, the vehicle running state detection is carried out first; if a vehicle collision is detected, it enters the collision control state; If it is not detected that the vehicle does not collide, perform ladder discharge according to the low-voltage power supply requirements of the vehicle; and c-5) When the vehicle is in a collision state, judge the battery according to the information fed back by the sensor and the battery system, and based on the information of the high-voltage insulation fault and the smoke sensor. The degree of failure of the battery pack; when the battery is slightly damaged, only a few battery cells are damaged but the insulation failure of the battery pack or the serious failure of the battery fire is not caused, only the damaged battery is removed, and the remaining battery still provides power to maintain the normal operation of the vehicle Or in a limp state; when the battery is severely damaged, causing serious failures such as battery pack insulation failure or battery fire, cut off the high voltage of the vehicle and disconnect the connecting lines of all battery cells to prevent high voltage danger. Preferably, the V _i1 of the lithium iron phosphate can be regulated as V _i1 ≤ 3.2V, and the ternary battery can be regulated as V _i1 ≤ 3.7V. The lithium iron phosphate can be specified as V _o1 ≥ 3.2V, and the ternary battery can be specified as V _o1 ≥ 3.7V.

As a further description of the control method of the present invention, preferably, the sensors include a vehicle speed sensor, an acceleration sensor, a vehicle height sensor, a roll angle sensor, a yaw angle sensor, a rotation angle sensor, a motor detection sensor, a battery voltage sensor, a battery current sensor , battery insulation sensor, smoke sensor.

It can be seen that in the safety system provided by the present invention, the controller accepts the signal of the sensor under charging, running, parking and collision conditions; the controller controls the relay to control the battery cells of the battery pack On the one hand, it controls the consistency between battery cells, on the other hand, it reduces the voltage level and improves safety. In addition, the controller controls the on-off of the relay according to the running condition of the vehicle, the information fed back by the sensor and the battery system, and adjusts the working state of the battery module and the output voltage of the battery pack.

Therefore, the beneficial effect of the present invention is that by changing the connection mode of the battery pack, the consistency between the battery cells can be ensured in the charging/discharging process, and the life and safety of the battery pack can be improved; If the battery pack is abnormal, you can reduce the voltage level by changing the connection method of the battery pack; in the parking condition, disconnect the connection between the battery cells to avoid high voltage hidden dangers; Pass and cut off part of the battery, reduce the voltage level, and avoid the danger of high voltage. In addition, the control method of the present invention is universal, and only needs to change the control program or the set value of the control variable for different battery systems.

Description of drawings

Fig. 1 is the basic composition block diagram of the control system of electric vehicle of the present invention;

Fig. 2 is a structural schematic diagram of a battery box formed by connecting a plurality of battery packs in series according to the present invention;

Fig. 3 is a schematic structural view of arbitrarily disconnecting a battery pack from the battery box of the present invention;

4 is a schematic structural view of a battery pack composed of multiple battery modules according to the present invention;

5 is a schematic structural view of a battery module composed of a plurality of battery cells according to the present invention;

Fig. 6 is a structural schematic diagram of the battery pack of the present invention in which battery modules are connected in series;

Fig. 7 is a schematic structural diagram of the battery pack of the present invention in which battery modules are connected in parallel;

Fig. 8 is a schematic structural view of the battery pack of the present invention in which battery modules are connected in parallel;

FIG. 9 is a schematic structural diagram of disconnecting one of the battery modules in the composition of the battery pack of the present invention;

Fig. 10 is a flow chart of the step discharge control strategy of the present invention;

Fig. 11 is a flowchart of the step charging control strategy of the present invention;

Fig. 12 is a flow chart of the operation control strategy of the present invention;

Fig. 13 is a parking control strategy flow chart of the present invention;

Fig. 14 is a flowchart of the collision control strategy of the present invention.

The reference signs are explained as follows:

Battery system 1, drive circuit 2, relay 3, sensor 4, controller 5, vehicle state estimator 6, battery pack B1, battery module C1, battery unit D1, battery case layer 11, battery pack layer 12, battery module layer 13 .

detailed description

In order to enable the examiner to further understand the structure, features and other purposes of the present invention, the attached preferred embodiments are attached with accompanying drawings in detail as follows. The embodiments illustrated in the accompanying drawings are only used to illustrate the technical solution of the present invention , does not limit the present invention.

First, please refer to FIG. 1 , which is a block diagram of the basic composition of the electric steam control system of the present invention. As shown in FIG. 1 , the safety system of the present invention includes a battery system 1 , a driving circuit 2 , a relay 3 , a sensor 4 , a controller 5 and a vehicle state estimator 6 . The battery system 1 includes a battery box layer 11 composed of several battery packs B1 connected in series, a battery pack layer 12 composed of several battery modules C1, and a battery module layer 13 composed of several battery cells D1. The relay 3 is used to control the on and off of the battery pack B1, the battery module C1 and the battery unit D1. The sensor 4 is used to sense various operating conditions of the vehicle. The controller 5 controls the on and off of the relay 4 according to the running conditions of the vehicle, the information fed back by the sensor 4 and the battery system 1 , adjusts the on and off of the battery module C1 and the battery unit D1 , and the output voltage of the battery pack. A vehicle sensor 5 , a vehicle state estimator 4 , a controller 3 , a drive circuit 2 and a battery system 1 are electrically connected in sequence, and the battery system 1 is electrically connected to the controller 3 .

For the battery system 1 , please refer to FIGS. 2 to 5 for details. As shown in Figure 2, the battery box is composed of multiple battery packs B1 in series to ensure a sufficient voltage level. The positive pole of each battery pack B1 is connected in series with the first relay 3, and the relay 3 connected in series between the battery pack B1 and the battery pack B1 The second relay 3 is connected in parallel, and each battery pack B1 can be switched on and off. When the controller 3 gets a signal that the voltage level needs to be lowered, see Figure 3, a battery pack B1 can be disconnected and turned on arbitrarily in the battery box, thereby changing the voltage level of the battery pack and controlling the consistency of the charging and discharging process sex.

As shown in Figures 3 and 4, the battery pack is composed of multiple battery modules. Each battery module C1 is placed side by side with the same polarity. The negative pole of the next battery module C1 is connected to the first relay 3, and then passes through the second relay. 3 is connected to the negative pole of the first adjacent relay 3, the positive pole of the adjacent battery module C1 is also connected through the third relay 3, and the fourth relay is connected between the positive pole of the battery module C1 and the negative pole of the second relay 3 3. The battery modules C1 can be connected in parallel or in series, and each battery module C1 can be turned on and off.

As shown in FIG. 5 , the structural form of the battery pack is the same as that of the battery module. Thus, the structural variant of the battery module can be the same as the structural variant of the battery pack. The battery module layer 13 is composed of a number of battery cells D1, each battery cell 1 is placed side by side with the same polarity, and the negative pole of the next battery cell D1 is connected to the first relay 3; then passes through the second relay 3 and the adjacent first The negative poles of the two relays 3 are connected, and the positive poles of the adjacent battery unit D1 are also connected through the third relay 3; the fourth relay 3 is bridged between the positive pole of the battery unit D1 and the negative pole of the second relay 3. The battery cells D1 can be connected in parallel or in series, and each battery cell D1 can be turned on and off.

Taking the structure of the battery pack as an example, how to change the connection mode of the battery pack by controlling the on and off of the relay 3 in the battery pack to change the voltage level and control the consistency of the charging and discharging process. As shown in FIG. 6 , when the corresponding relay 3 is turned off and turned on accordingly, the battery pack can be formed by connecting battery modules C1 in series. As shown in FIG. 7 , when the corresponding relay 3 is turned off and on accordingly, the battery pack B1 can be formed by parallel connection of the battery modules C1 . As shown in FIG. 8 , when the corresponding relays 3 are turned off and on accordingly, the battery pack B1 can be composed of battery modules C1 in parallel. As shown in FIG. 9 , when the corresponding relay 3 is turned off and on accordingly, any one or more battery modules C1 in the battery pack can be disconnected, and the remaining battery modules C1 can be connected in a desired manner.

By changing the connection mode of the battery pack in the present invention, the consistency between the battery cells is guaranteed during the charging/discharging process, and the life and safety of the battery pack are improved; The connection mode of the battery pack can reduce the voltage level; under the parking condition, disconnect the connection between the battery cells to avoid high voltage hidden danger; in the case of a collision, according to the degree of collision and the damage of the battery, select the conduction and cut-off of some batteries to reduce the Voltage level, to avoid high voltage danger.

The control method of the electric vehicle battery safety structure system will be described in detail below in conjunction with the control flow chart.

(1) As shown in Figure 10, the battery system 1 receives the discharge instruction information from the controller 5, and closes a certain number of relays 3 according to the current energy demand to start the first stage of discharge. When it is detected that K of the currently discharged batteries have reached the discharge threshold V _o1 of the first stage, V _o1 is determined according to the battery voltage variation range and discharge characteristics of the battery cells, such as lithium iron phosphate can be specified as V _o1 ≥ 3.2V, the ternary battery can be specified as V _o1 ≥ 3.7V and so on. Disconnect these batteries while closing the other K batteries that have not yet been discharged. By analogy, when all the batteries in the battery pack are discharged and reach the discharge threshold V1 of the _first stage, the discharge of the second stage is carried out. As mentioned above, after multiple stages of discharge, when all the batteries reach the discharge threshold V _min , the battery will no longer discharge.

(2) As shown in Figure 11, when the battery pack is in the charging state, close the relay 3, the first stage is closed to charge all the batteries, when it is detected that K batteries have reached the charging threshold V _i1 of the first stage, V _i1 according to The variation range and charging characteristics of the battery cell voltage are determined. For example, the lithium iron phosphate can be specified as V _i1 ≤ 3.2V, and the ternary battery can be specified as V _i1 ≤ 3.7V. These batteries are disconnected, the remaining batteries are still charged, and so on, until all batteries reach the first-stage charging threshold V _i1 , and then all batteries are charged in the second stage. As mentioned above, after charging in multiple stages, when all the batteries reach the charging threshold V _max , the batteries will no longer be charged.

(3) Regardless of whether the vehicle is in the running state or in the parking state, the running state of the vehicle must be detected first, as shown in Figure 14. When the vehicle is detected to be collided, the severity of the collision is first judged. If the battery is seriously damaged, such as battery fire, insulation failure, etc., causing personal safety problems, first disconnect the high-voltage output and cut off all battery connections to prevent high-voltage accidents. If the battery is slightly damaged, the damaged battery is removed from the system, the remaining battery works normally, and the vehicle can still be powered in running or parked state.

(4) As shown in Figure 12, when the vehicle is in the running state, when the detected vehicle is collided, it enters into the collision control in Figure 14 . According to the current needs of the vehicle, the battery pack is discharged stepwise. When the voltage of the battery pack reaches the minimum threshold value set for operation, the vehicle enters a limp state, and the battery pack discharges step by step according to its own discharge capacity until the discharge ends or stops running.

(5) As shown in Figure 13, the vehicle is in a stopped state, and when it is detected that the vehicle is collided, it enters into the collision control in Figure 14 . If no collision is detected, it is detected that it is currently in a charging state, and step charging is performed. If both are not detected, carry out ladder discharge according to the low-voltage power supply requirements of the vehicle.

It can be seen that the control method of the present invention is universal, and only needs to change the control program or the set value of the control variable for different battery systems.

It should be declared that the above summary of the invention and specific implementation methods are intended to prove the practical application of the technical solutions provided by the present invention, and should not be interpreted as limiting the protection scope of the present invention. Those skilled in the art may make various modifications, equivalent replacements or improvements within the spirit and principle of the present invention. The protection scope of the present invention shall be determined by the appended claims.

Claims (9)

1. A safety system of an electric vehicle battery pack cell structure, characterized in that the safety system comprises a battery system (1), a drive circuit (2), a relay (3), a sensor (4), a controller (5) and a vehicle state estimator (6); wherein,

the battery system (1) comprises a battery box layer (11) formed by connecting a plurality of battery packs (B1) in series, a battery cladding (12) formed by a plurality of battery modules (C1), and a battery module layer (13) formed by a plurality of battery units (D1);

the relay (3) is used for controlling the on and off of the battery pack (B1), the battery module (C1) and the battery unit (D1);

the sensor (4) is used for monitoring information of the vehicle under various operating conditions;

the controller (5) controls the on-off of the relay (3) according to the running condition of the vehicle, the sensor (4) and the information fed back by the battery system (1), adjusts the on-off of the battery pack (B1), the battery module (C1) and the battery unit (D1), and outputs the voltage of the battery pack.

2. The safety system as claimed in claim 1, characterized in that the positive pole of each battery pack (B1) is connected in series with a first relay (3), and a second relay (3) is connected in parallel to the relay (3) in which the battery pack (B1) and the battery pack (B1) are connected in series, each battery pack (B1) being capable of being switched on and off.

3. The safety system according to claim 1, characterized in that each battery module (C1) is placed side by side with the same polarity, connected to the first relay (3) next to the negative pole of the battery module (C1), connected to the first relay (3) of the negative pole of the adjacent battery module via the second relay (3), and connected to the positive pole of the adjacent battery module (C1) via the third relay (3); and a fourth relay (3) is bridged between the negative poles and the positive poles of the second relay (3) and the positive poles of the two adjacent battery modules (C1).

4. The safety system according to claim 3, wherein the battery modules (C1) are connected in parallel and in series, and each battery module (C1) is turned on and off.

5. Safety system according to claim 1, characterized in that each battery unit (D1) is placed side by side with the same polarity, the first relay (3) being connected next to the negative pole of the battery unit (D1); then the second relay (3) is connected with the first relay (3) of the cathode of the adjacent battery unit, and the anode of the adjacent battery unit (D1) is connected with the third relay (3); and a fourth relay (3) is bridged between the negative poles and the positive poles of the second relay (3) and the positive poles of the two adjacent battery units (D1).

6. A safety system as claimed in claim 5, characterized in that the battery cells (D1) are connectable in parallel and in series, each battery cell (D1) being switchable on and off.

7. Safety system according to claim 1, characterized in that the sensors (4) comprise a vehicle speed sensor, an acceleration sensor, a vehicle height sensor, a roll angle sensor, a yaw angle sensor, a turning angle sensor, a motor detection sensor, a battery voltage sensor, a battery current sensor, a battery insulation sensor, a smoke sensor.

8. A control method for a safety system according to any one of claims 1 to 8, wherein the control method comprises the steps of:

a) the vehicle sensor (4) senses the running condition of the vehicle and transmits corresponding information to the vehicle state estimator (6);

b) the vehicle state estimator (6) obtains information sent by the vehicle sensor (4), obtains a state signal of the vehicle, and transmits the state signal to the controller (5); and

c) the controller (5) receives a state signal sent by the vehicle state estimator (6) and a power signal fed back by the battery system (1), and controls the drive circuit (2) to control the on and off of the relay (3) in the battery system (1); wherein,

c-1) when the battery pack is in a discharging process, the battery system (1) receives discharging instruction information from the controller (5), and the relay (3) is closed according to the current energy requirement, so that all or part of the batteries are discharged; when K discharged batteries are detected to reach the discharge voltage threshold value V_o1，V_o1According to the variation range and the discharge characteristic of the battery voltage of the single batteries, the relays (3) of the K batteries are switched off to stop discharging, and the rest batteries are still discharged until all the batteries reach the discharge voltage threshold value V_o1(ii) a Then give all toThe battery is discharged in the next stage;

c-2) when the battery pack is in a charging state, according to the voltage condition of the battery module (C1) or the battery unit (D1) which is fed back, closing the relay (3) to charge all the batteries, and when K batteries are detected to reach the charging voltage threshold value V_i1，V_i1According to the variation range and charging characteristics of the battery voltage of the single batteries, the relays (3) of the K batteries are switched off to stop charging, and the rest batteries are charged until all the batteries reach the charging voltage threshold value V_i1(ii) a Then all the batteries are charged in the next stage;

c-3) when the vehicle is in the running state, firstly, detecting the running state of the vehicle; entering a collision control state if a vehicle collision is detected; the battery system (1) performs step discharge according to the information provided by the controller (5); when the voltage of the battery pack reaches a threshold value day inch set by operation, the vehicle enters a limp state, and the battery pack performs step discharge according to self discharge capacity;

c-4) when the vehicle is in a parking state, detecting the running state of the vehicle firstly; entering a collision control state if a vehicle collision is detected; if no vehicle collision is detected and the battery system (1) is in a charging state, performing step charging; if neither vehicle collision nor vehicle charging is detected, carrying out step discharge according to the low-voltage power supply requirement of the vehicle; and

c-5) judging the fault degree of the battery pack according to information fed back by the sensor (4) and the battery system (1) when the vehicle is in a collision state; when the damage degree of the battery is light, only individual battery cells are damaged but the insulation failure of the battery pack is not caused or the battery is in fire serious failure, only the damaged battery is cut off, and the residual battery still provides electric energy to keep the normal running or limp state of the vehicle; when the damage degree of the battery is heavy, and the battery pack has insulation fault or serious faults such as battery ignition and the like, the high voltage of the whole vehicle is cut off, and the connecting lines of all the battery monomers are disconnected, so that the high voltage danger is prevented.

9. A control method according to claim 9, characterized in that the sensors (4) comprise a vehicle speed sensor, an acceleration sensor, a vehicle height sensor, a roll angle sensor, a yaw angle sensor, a rotation angle sensor, a motor detection sensor, a battery voltage sensor, a battery current sensor, a battery insulation sensor, a smoke detector.