KR102664096B1 - Control method of electric vehicle corresponding to BMS power disconnection - Google Patents

Abstract

The present invention relates to a control method when the BMS power supply of an electric vehicle is disconnected, and specifically, to control the vehicle in response to a disconnection that occurs in the circuit between the battery that provides driving power for the motor and the BMS (Battery Management System) for battery management. This relates to a control method when the BMS power supply of an electric vehicle is disconnected for safe control.

Description

Control method when BMS power disconnection of electric vehicle {Control method of electric vehicle corresponding to BMS power disconnection}

The present invention relates to a control method in case of BMS power disconnection of an electric vehicle, and specifically, to control the vehicle in response to disconnection that occurs in the circuit between the BMS (Battery Management System) for battery management and the battery that supplies power to the BMS. This relates to a control method when the BMS power supply of an electric vehicle is disconnected for safe control.

Electric vehicles are equipped with an electric motor and a high-voltage battery to generate driving force for driving, and the high-voltage battery supplies power to the electric motor and electronic loads through a battery relay.

In addition, electric vehicles are equipped with a BMS (Battery Management System) that diagnoses the status of the high-voltage battery and controls the battery relay that applies battery power to the electric motor and electric load. To run the vehicle, a VCU (Vehicle Control Unit) is installed. ) and MCU (Motor Control Unit), communication between the vehicle control unit and the BMS is essential.

Therefore, if a communication failure related to the BMS occurs while driving, a minimum amount of driving is possible to prevent accidents due to the vehicle suddenly stopping.

If the BMS leaves the vehicle's communication bus, a BMS communication timeout phenomenon occurs. At this time, the BMS maintains the battery relay in the operating state before the communication timeout phenomenon occurred. For example, when driving with the battery relay on, the battery relay is kept in the on state after a communication timeout occurs to enable driving. At this time, the VCU assumes that the battery relay maintains its previous operating state and continues to send motor torque commands to the MCU, but limits the motor output to 50% or less. In addition, the VCU blinks the ready lamp displayed on the vehicle instrument panel to make the driver aware that the vehicle is in an abnormal state, thereby encouraging the vehicle to be brought to a repair shop.

Meanwhile, the BMS receives power from the low-voltage battery of the vehicle, and the power of the low-voltage battery is supplied to the BMS through a battery fuse installed between the low-voltage battery and the BMS, and the BMS uses the power of the low-voltage battery to operate the battery relay. Controls the on/off operation of

When the battery fuse is blown, the BMS is unable to transmit signals for communication with the vehicle control unit because the power supply from the low-voltage battery is cut off, resulting in a communication timeout phenomenon, and the power supply to maintain the closed state of the battery relay. Because this is lost, the battery relay is in an open/off state regardless of the command. At this time, as a BMS communication timeout situation occurs, the VCU continuously transmits motor torque commands to the MCU to maintain the vehicle driving state and operates the ready lamp in blinking mode.

When the battery relay is opened due to a disconnection of the circuit between the low-voltage battery and the BMS, the power for driving the motor (high-voltage battery) is lost, and as the power for driving the motor is lost, the vehicle becomes impossible to drive.

However, there is a problem in which the driver perceives that the vehicle can continue to be driven by the VCU operating the ready lamp in a blinking mode even though the vehicle is in a situation where driving is impossible, and as a result, the vehicle suddenly becomes impossible to drive on the road. occurs.

The present invention was developed in consideration of the above points. When the vehicle is ready, the battery relay is diagnosed to be disconnected between the high-voltage battery and the inverter based on the voltage trend of the inverter capacitor according to the vehicle's driving conditions, and the battery relay is The purpose is to provide a control method when the BMS power is disconnected in an electric vehicle, which ensures driving safety by accurately recognizing the vehicle's undrivable state to the driver and inducing vehicle shutdown when a disconnection is diagnosed.

Accordingly, the present invention provides a control method when the BMS power is disconnected in an electric vehicle that runs using a motor supplied with power from a high-voltage battery and driven through a battery relay controlled by a BMS (Battery Management System), comprising:

In the ready state of the electric vehicle, when a communication timeout of the BMS occurs, an inverter that converts the current applied from the high-voltage battery and supplies it to the motor, and a battery relay that applies the current applied from the high-voltage battery to the inverter. A first step of detecting the voltage of an inverter capacitor connected between the two and determining whether a voltage change in the capacitor occurs; When a voltage change in the capacitor occurs, a second step of determining the vehicle's driving mode as one of a stop mode, an acceleration driving mode, and a regenerative braking mode; A third step of determining that the battery relay is open when the voltage change value of the capacitor is greater than the reference voltage set according to the driving mode; A fourth step of shutting down the vehicle when it is determined that the battery relay is open provides a control method when the BMS power of an electric vehicle is disconnected.

Specifically, when the driving mode of the vehicle determined in the second step is the stop mode, in the third step, if the voltage of the capacitor falls more than the first reference voltage, it is determined that the battery relay has switched from the closed mode to the open mode, When the driving mode of the vehicle determined in the second step is the acceleration driving mode, in the third step, if the voltage of the capacitor falls more than the second reference voltage, it is determined that the battery relay has switched from the closed mode to the open mode. Here, the second reference voltage is set to a voltage value that is greater than the first reference voltage by a certain amount. In addition, when the driving mode of the vehicle determined in the second step is the regenerative braking mode, in the third step, when the voltage of the capacitor rises above the third reference voltage, it is determined that the battery relay has switched from the closed mode to the open mode; , the third reference voltage is set to a voltage value that is greater than the second reference voltage by a set value.

And the fourth step includes turning off the ready lamp indicating whether the vehicle is drivable to indicate that the vehicle is in a drivable state; When the vehicle speed reaches 0 (zero), manually shifting the vehicle's shift lever from drive range (D range) to park range (P range) and manually turning on the parking brake. .

In addition, the fourth step may be implemented as a step of automatically shifting the shift lever from drive to park when the vehicle speed is reduced to a certain vehicle speed when the electronic shift lever (SBW) is installed.

According to the control method when the BMS power of an electric vehicle is disconnected according to the present invention, the voltage trend of the inverter capacitor is monitored to diagnose whether the battery relay is disconnected, and vehicle status information (unable to drive) according to the diagnosis result is accurately provided to the driver. By ensuring that appropriate follow-up measures (vehicle shutdown) are taken, it is possible to quickly and safely respond to BMS power disconnection problems.

Figure 1 is a diagram showing the circuit configuration between the high-voltage battery and motor of an electric vehicle.
Figure 2 is a diagram showing the voltage trend of the inverter capacitor when the electric vehicle is in stop mode.
Figure 3 is a diagram showing the voltage trend of the inverter capacitor during the acceleration driving mode of the electric vehicle.
Figure 4 is a flowchart showing the control process when the BMS power supply of an electric vehicle is disconnected according to the present invention.

Hereinafter, the present invention will be described so that those skilled in the art can easily carry it out.

As shown in Figure 1, the electric vehicle is equipped with an electric motor 7 that generates driving force for driving and a high-voltage battery 1 that provides driving power to the electric motor 7, and the high-voltage battery 1 ) is in a state where power can be supplied to the electric motor (7) and the electrical load through the battery relay (4) when the vehicle is in a ready state. And the power of the high-voltage battery 1 can be supplied to the low-voltage battery 11 through a low-voltage DC-DC converter (LDC) 9.

The low-voltage battery 11 is connected to the BMS (Battery Management System) 8 through the battery fuse 2 and supplies control power to the BMS, and the BMS 8 diagnoses the state of the high-voltage battery 1. And the battery relay 4 for applying high-voltage power to the electric motor 7 and the high-voltage electric load is controlled on/off. Low-voltage driving power is selectively supplied to the battery relay (4) by the BMS (8). And an inverter capacitor 6 for current smoothing is connected between the inverter 5 for converting the current applied to the electric motor 7 and the battery relay 4.

The BMS 8 communicates with vehicle control units such as an MCU (Motor Control Unit) for controlling the electric motor 7 and a VCU (Vehicle Control Unit), which is a higher level controller and transmits a motor torque command to the MCU when driving. It will be performed.

In the READY state of the electric vehicle, that is, in a state in which the electric vehicle is ready to drive, that is, in a state in which the electric vehicle can be driven, the low-voltage battery 11 and the battery fuse 2 are blown. When the circuit between the BMS (8) is disconnected and the driving voltage of the battery relay is lost or the signal connector for signal transmission from the BMS (8) is removed, the battery relay (4) is converted to an open state.

The electric vehicle is determined to have entered the ready state when the battery relay 4 is in closed mode and the conditions for applying power to the electric motor 7 and the high-voltage electric load through the battery relay 4 are satisfied. do.

Accordingly, in the present invention, when the vehicle is ready, the circuit disconnection of the battery relay (4) is diagnosed based on the voltage trend of the inverter capacitor (6) according to the vehicle's driving conditions, and as a result of the diagnosis, the vehicle cannot be driven due to the circuit disconnection. When the condition is determined, the driver is accurately informed of the vehicle status and the vehicle is shut down to ensure driving safety.

To this end, the control method when the BMS power supply of an electric vehicle is disconnected according to the present invention includes a first method of determining whether a voltage change in the inverter capacitor 6 occurs when a communication timeout of the BMS 8 occurs in the ready state of the vehicle. Step, the second step of determining the driving mode of the vehicle when the voltage change of the inverter capacitor 6 occurs, if the voltage change value of the inverter capacitor 6 is higher than the reference voltage set according to the driving mode, the high voltage battery 1 It includes a third step of determining that the battery relay (4) connected between and the inverter capacitor (6) is switched open, and a fourth step of shutting down the vehicle when the battery relay (4) is determined to be open. The control process may be performed by a vehicle control unit such as VCU.

The inverter capacitor (6) converts the current applied from the high-voltage battery (1) into three-phase alternating current and supplies it to the electric motor (7), and the inverter (5) supplies the current supplied from the high-voltage battery (1) to the inverter ( It is connected and arranged between the battery relays (4) that apply to 5).

The VCU determines that a communication timeout of the BMS 8 has occurred if there is no signal transmitted from the BMS 8 for a certain period of time in the vehicle's ready state. In the first step, when it is determined that a communication timeout of the BMS 8 has occurred when the vehicle is in a ready state for driving, the voltage of the inverter capacitor 6 is detected in real time to determine the voltage change of the capacitor 6. Determine whether this occurs.

In the second step, if the voltage fluctuation of the inverter capacitor 6 continues to occur, the vehicle's driving mode is determined by dividing it into one of the stop mode, acceleration driving mode, and regenerative braking mode (or deceleration driving mode). .

When the driving mode of the vehicle is determined to be a stop mode in which the vehicle speed is 0 (zero), the battery relay 4 switches from the closed mode to the open mode when the voltage value of the inverter capacitor 6 falls above the first reference voltage. It is judged that it has been done. When the vehicle is ready to drive, the battery relay 4 is maintained in the closed mode. In the stop mode, the shift lever is located in the drive range.

When the battery relay (4) is switched to open mode, a disconnection occurs between the high-voltage battery (1) and the inverter (5) by the battery relay (4), and the battery relay (4) in closed mode The charge amount and voltage of the inverter capacitor (6) decrease due to the operation of the high-voltage electrical components that were receiving power from the high-voltage battery (1). While the vehicle is stopped, only high-voltage electrical components such as the LDC (Low-Voltage DC-DC Converter) (9) and the air conditioner compressor (10) use the power of the inverter capacitor (6), so the inverter capacitor (6) ) has a relatively low voltage drop rate (see Figure 2).

If the driving mode of the vehicle is determined to be an acceleration driving mode in which the vehicle speed increases, it is determined that the battery relay 4 has switched from the closed mode to the open mode when the voltage value of the inverter capacitor 6 falls above the second reference voltage. do.

If the battery relay (4) switches to open mode while driving in acceleration mode, a disconnection occurs between the high-voltage battery (1) and the inverter (5) by the battery relay (4), and the inverter is The charge amount and voltage of the capacitor 6 decrease. During acceleration, the power of the inverter capacitor 6 is consumed by the driving of the electric motor 7 in addition to high-voltage electrical components such as the LDC 9 and the air conditioner compressor 10, so the voltage of the inverter capacitor 6 momentarily decreases. It drops sharply (see FIG. 3), and the power of the capacitor 6 is consumed at a faster rate than in the stop mode.

Here, the second reference voltage is set to a voltage value that is greater than the first reference voltage by a certain amount. For example, the first reference voltage may be set to 30V and the second reference voltage may be set to 150V. The first and second reference voltages are set to a voltage value smaller than the normal voltage value of the inverter capacitor 6 when the battery relay 4 is in closed mode.

By setting the reference voltage values in the stopping mode and the acceleration driving mode differently and setting the first reference voltage to a value smaller than the second reference voltage, it is possible to quickly diagnose whether the battery relay 4 is open in the stopping mode. This makes it possible to increase the accuracy of diagnosing whether the battery relay 4 is open in acceleration driving mode.

Also, if the driving mode of the vehicle is determined to be a regenerative braking mode (or deceleration driving mode) in which the vehicle speed is reduced, the battery relay 4 is switched in the closed mode when the voltage value of the inverter capacitor 6 rises above the third reference voltage. It is judged that it has switched to open mode.

When the driver takes his or her foot off the accelerator pedal and coasts (coasting) or decelerates (braking) by stepping on the brake pedal, the electric motor is activated by regenerative braking with the battery relay (4) open (off). Back electromotive force is applied to (7), causing the voltage and charge of the inverter capacitor (6) to increase. Therefore, when the electric vehicle is driven in regenerative braking mode, if the voltage value of the inverter capacitor 6 rises above the third reference voltage, it can be determined that the battery relay 4 has been switched to open mode.

Here, the third reference voltage is set to a voltage value that is greater than the second reference voltage by a set value. For example, the third reference voltage may be set to a voltage value that is approximately 50V greater than the normal voltage of the inverter capacitor 6. When the battery relay 4 is in closed mode, that is, when the power of the inverter capacitor 6 is not consumed by a high-voltage electric load, the voltage value of the inverter capacitor 6 is the normal voltage value of the inverter capacitor 6.

In this way, it can be determined that the battery relay 4 is switched to open mode based on the voltage trend of the inverter capacitor 6 according to the driving mode of the vehicle, and the battery relay 4 is opened to operate the electric motor 7. If it is determined that driving power has been substantially lost, the vehicle is shut down to ensure driving safety and driver safety.

The step of controlling the shutdown of the vehicle (the fourth step) includes turning off the ready lamp that indicates whether the vehicle can be driven, and when the vehicle speed reaches 0 (zero), the shift lever of the vehicle is shifted from the drive range (D range). This may include moving to the parking range (P range) and turning on the parking brake.

Before shutting down the vehicle, the ready lamp displayed on the instrument panel is first turned off to let the driver know that the vehicle is in an undriveable state. The ready lamp is controlled to ON and lights up when the vehicle is in a drivable state.

The driver, who recognizes that the vehicle is in a non-driving state, shifts the vehicle's shift lever to the park range (P range) and turns the parking brake on to lock the wheels so that they do not rotate, in order to park the vehicle when the vehicle is stopped.

In addition, in the case of an electric vehicle equipped with an electronic shift lever (SBW), when the vehicle speed decreases and reaches a certain vehicle speed below the stopping level (for example, 2 kph), the shift lever is automatically shifted to park, thereby preventing the vehicle from being pushed off the slope. It can be prevented.

Here, with reference to FIG. 4, the control process when the BMS power supply of an electric vehicle is disconnected is summarized as follows.

As shown in FIG. 4, when a communication timeout of the BMS 8 occurs in the ready state of the electric vehicle and a voltage change in the inverter capacitor occurs, the driving mode of the vehicle is determined. If the vehicle is stopped (vehicle speed = 0), the vehicle is shut down when the voltage drop value of the inverter capacitor becomes more than the first reference voltage, and if the vehicle is running (vehicle speed ≠ 0), the driving mode is determined depending on whether or not it is accelerating. If the vehicle is accelerating (acceleration > 0), the vehicle is shut down when the voltage drop value of the inverter capacitor becomes more than the second reference voltage, and if the vehicle is under regenerative braking, the voltage rise value of the inverter capacitor becomes more than the third reference voltage. When shutting down the vehicle.

When shutting down a vehicle, the ready lamp is first turned off to let the driver know that the vehicle is in an undriveable state. The driver, who recognizes that the vehicle is in an undriveable state, shifts the vehicle's shift lever from drive to park and turns on the parking brake when the vehicle speed reaches zero.

Although it is possible to drive temporarily when driving in regenerative braking mode, if the back electromotive force applied to the electric motor is continuously allowed, there is a risk of damage to the inverter power module, so it is necessary to immediately shut down the vehicle and end the inverter operation.

As the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to the above-described embodiments, and various modifications and modifications by those skilled in the art using the basic concept of the present invention as defined in the following patent claims are made. Improvements are also included in the scope of the present invention.

1: High voltage battery
2: Battery fuse
4: Battery relay
5: inverter
6: Inverter capacitor
7: Electric motor
8:BMS
11: Low voltage battery

Claims (6)

A control method when the BMS power is disconnected in an electric vehicle that runs using a motor supplied with power from a high-voltage battery and driven through a battery relay controlled by a BMS (Battery Management System), comprising:
In the ready state of the electric vehicle, when a communication timeout of the BMS occurs, between an inverter that converts the current applied from the high-voltage battery and supplies it to the motor and a battery relay that applies the current applied from the high-voltage battery to the inverter. A first step of detecting the voltage of an inverter capacitor connected to and determining whether a voltage change in the capacitor occurs;
If it is determined that the voltage of the capacitor has changed in the first step, a second step of determining the vehicle's driving mode as one of a stop mode, an acceleration driving mode, and a regenerative braking mode;
A third step of determining that the battery relay has switched from a closed mode to an open mode if the voltage change value of the capacitor is greater than the reference voltage set in the driving mode of the vehicle determined in the second step;
A fourth step of shutting down the vehicle when it is determined that the battery relay has been switched to open mode;
Control method when the BMS power of an electric vehicle is disconnected, including.
In claim 1,
When the driving mode of the vehicle determined in the second step is the stop mode, in the third step, if the voltage of the capacitor falls above the first reference voltage, it is determined that the battery relay has switched from the closed mode to the open mode. Control method when the BMS power of an electric vehicle is disconnected.
In claim 2,
When the driving mode of the vehicle determined in the second step is the acceleration driving mode, in the third step, if the voltage of the capacitor falls more than the second reference voltage, it is determined that the battery relay has switched from the closed mode to the open mode, A control method in case of BMS power disconnection of an electric vehicle, characterized in that the second reference voltage is set to a voltage value that is greater than the first reference voltage by a certain amount.
In claim 3,
When the driving mode of the vehicle determined in the second step is the regenerative braking mode, in the third step, when the voltage of the capacitor rises above the third reference voltage, it is determined that the battery relay has switched from the closed mode to the open mode, A control method in case of BMS power disconnection of an electric vehicle, characterized in that the third reference voltage is set to a voltage value greater than the second reference voltage by a set value.
In claim 1,
The fourth step is,
Turning off a ready lamp indicating whether the vehicle is drivable to indicate that the vehicle is in a drivable state;
When the vehicle speed reaches 0 (zero), manually shifting the shift lever of the vehicle from drive range (D range) to park range (P range) and manually turning on the parking brake;
A control method when the BMS power supply of an electric vehicle is disconnected, comprising:
In claim 1,
The fourth step is,
Turning off a ready lamp indicating whether the vehicle is drivable to indicate that the vehicle is in a drivable state;
If an electronic shift lever (SBW) is installed, automatically shifting the shift lever from drive to park when the vehicle speed is reduced to a certain speed or less;
A control method when the BMS power supply of an electric vehicle is disconnected, comprising:

Images