JP7679799B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

Patent document 1 discloses that a vehicle that runs on power from a main battery supplied to a traction motor is provided with a bidirectional DC/DC converter that boosts and outputs power from the auxiliary battery in a current path between the main battery and an inverter when the main battery is charged by the auxiliary battery.

JP 2016-201871 A

In the configuration described in Patent Document 1, when driving with the relay open and the main battery disconnected from the driving motor (during battery-less driving), it is necessary to maintain the voltage of the capacitor connected to the power line between the relay and the inverter. Therefore, as a control to maintain the capacitor voltage, it is possible to increase the torque of the power generation motor and decrease the torque of the driving motor, but in that case, if the motor rotation speed is high, it may be difficult to maintain the capacitor voltage.

The present invention was made in consideration of the above circumstances, and aims to provide a vehicle control device that can maintain the voltage of a capacitor connected to the power line between the relay and the inverter when driving with the main battery disconnected from the driving motor.

The present invention is a control device for a vehicle that includes a driving motor, an inverter that drives the driving motor, a main battery that supplies power to the driving motor, a boost converter that boosts the power supplied from the main battery and outputs it to the inverter, a relay that switches between electrical connection and disconnection between the main battery and the boost converter, a first power line that connects the relay and the boost converter, a second power line that connects the boost converter and the inverter, a first capacitor connected to the first power line, a second capacitor connected to the second power line, an auxiliary battery, and a bidirectional DC/DC converter that boosts the power from the auxiliary battery and outputs it to the first power line.The control device is characterized in that, during battery-less driving in which the vehicle is driven with the relay in an open state and the main battery disconnected from the driving motor, if the voltage of the first capacitor and the voltage of the second capacitor are equal to or lower than a threshold value, the bidirectional DC/DC converter is controlled to boost the power from the auxiliary battery and output it to the first power line.

In this invention, when driving with the main battery disconnected from the driving motor, the voltage of the capacitor connected to the power line between the relay and the inverter can be maintained.

FIG. 1 is a diagram for explaining a vehicle according to an embodiment. FIG. 2 is a diagram for explaining the control device for the vehicle. FIG. 3 is a flow chart showing control during battery-less running.

The vehicle control device according to the embodiment of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiment described below.

Figure 1 is a diagram for explaining a vehicle in an embodiment. The vehicle 1 includes a first motor (MG1) 2, a second motor (MG2) 3, a first inverter 4, a second inverter 5, a boost converter 6, a main battery 7, and a control device 8.

The first motor 2 and the second motor 3 are motors that function as a power source for driving, and are motor generators that have the functions of an electric motor and a generator. In the vehicle 1, the wheels can be driven by at least one of the power output from the first motor 2 and the power output from the second motor 3. For example, the first motor 2 and the second motor 3 are connected to different rotating elements of the three rotating elements of a planetary gear device, and the first motor 2 mainly functions as a generator, and the second motor 3 mainly functions as an electric motor. The vehicle 1 is equipped with a power transmission device that transmits the power output from the first motor 2 and the power output from the second motor 3 to the wheels. For example, the vehicle 1 is a hybrid vehicle that is equipped with a power split device that splits the power of the engine to the first motor 2 side and the wheel side, and can run by adding the torque output by the second motor 3 to the torque output by the engine.

The first and second motors 2 and 3 are each composed of a synchronous generator motor having a rotor with a permanent magnet embedded therein and a stator around which a three-phase coil is wound. The three-phase coil (U-phase, V-phase, W-phase) wound around the stator of the first motor 2 is electrically connected to the first inverter 4. The three-phase coil (U-phase, V-phase, W-phase) wound around the stator of the second motor 3 is electrically connected to the second inverter 5.

The first inverter 4 and the second inverter 5 are power conversion devices that convert DC power from the main battery 7 into AC power and supply it to the motor. The first inverter 4 and the second inverter 5 are connected to the high-voltage power line. The first inverter 4 is provided between the first motor 2 and the boost converter 6. The second inverter 5 is provided between the second motor 3 and the boost converter 6.

The first inverter 4 has six switching elements T41-T46 and six diodes D41-D46 so that three-phase current can be passed through the three-phase coils of the first motor 2. The switching elements T41-T46 are arranged in pairs of two, one on the source side and the other on the sink side of the positive bus bar PL2 and the negative bus bar NL2 of the high-voltage power line. The diodes D41-D46 are connected in parallel in the opposite direction to their corresponding switching elements T41-T46. In the first inverter 4, each of the three-phase coils of the first motor 2 is connected to each of the connection points between the paired switching elements.

The second inverter 5 has six switching elements T51-T56 and six diodes D51-D56 so that it can pass three-phase current through the three-phase coils of the second motor 3. The second inverter 5 is electrically connected to the main battery 7 via the boost converter 6, so that the second motor 3 is driven by power supplied from the main battery 7.

The boost converter 6 is a boost device that boosts the power of the main battery 7 and supplies it to the first inverter 4 and the second inverter 5. The boost converter 6 is connected to a high-voltage side power line to which the first inverter 4 and the second inverter 5 are connected, and a low-voltage side power line to which the main battery 7 is connected. The low-voltage side power line is the first power line. The high-voltage side power line is the second power line. The boost converter 6 has two switching elements T61, T62, two diodes D61, D62 connected in parallel in the reverse direction to the switching elements T61, T62, and a reactor L. In the boost converter 6, the first switching element T61 of the upper arm and the second switching element T62 of the lower arm are connected in series. The first switching element T61 is connected to the positive bus PL2 of the high-voltage side power line. The second switching element T62 is connected to the first switching element T61, the negative bus NL2 of the high-voltage power line, and the negative bus NL1 of the low-voltage power line. The reactor L is connected to the connection point between the switching elements T61 and T62 and the positive bus PL1 of the low-voltage power line.

In addition, the boost converter 6 switches the first and second switching elements T61, T62 on and off under the control of the control device 8. That is, the control device 8 executes switching control of the boost converter 6. By executing this switching control, the power of the main battery 7 (power of the low-voltage side power line) can be boosted and supplied to the high-voltage side power line, or the power of the high-voltage side power line can be reduced and supplied to the low-voltage side power line (main battery 7). Furthermore, a first smoothing capacitor C1 is connected to the positive electrode bus bar PL1 and the negative electrode bus bar NL1 of the low-voltage side power line. A resistor R is connected in parallel with the first capacitor C1. A second smoothing capacitor C2 is connected to the positive electrode bus bar PL2 and the negative electrode bus bar NL2 of the high-voltage side power line.

The first capacitor C1 smoothes the voltage (hereinafter referred to as the battery voltage) VB of the main battery 7 and supplies it to the boost converter 6. The vehicle 1 is equipped with a voltage sensor that detects the voltage VL of the first capacitor C1. This voltage sensor detects the voltage VL across both ends of the first capacitor C1, i.e., the voltage (hereinafter sometimes referred to as the DC voltage) VL between the positive bus bar PL1 and the negative bus bar NL1 of the low-voltage side power line connecting the main battery 7 and the boost converter 6.

The second capacitor C2 smoothes the DC voltage supplied from the boost converter 6 and supplies it to the first and second inverters 4, 5. The vehicle 1 is equipped with a voltage sensor that detects the voltage VH of the second capacitor C2. This voltage sensor detects the voltage VH across both ends of the second capacitor C2, i.e., the voltage VH between the positive bus bar PL2 and the negative bus bar NL2 of the high-voltage power line connecting the boost converter 6 and each inverter 4, 5 (hereinafter sometimes referred to as the system voltage).

The main battery 7 is a DC power source that can be charged and discharged, and is composed of a secondary battery such as a nickel-metal hydride or lithium ion battery. The main battery 7 discharges power to the first and second inverters 4, 5 via the boost converter 6, or charges with power supplied from the first and second inverters 4, 5. During power running, the power stored in the main battery 7 can be supplied to the second motor 3. During regeneration, the second motor 3 functions as a generator, so that the power generated by the second motor 3 can be charged to the main battery 7. The vehicle 1 is equipped with a voltage sensor that detects the voltage VB of the main battery 7 and a current sensor that detects the input/output current of the main battery 7.

The vehicle 1 further includes a system main relay (hereinafter referred to as SMR) 9, an air conditioner (A/C) 10, an auxiliary battery 11, and a bidirectional DC/DC converter (bidirectional DDC) 12.

The SMR 9 switches between electrical connection and disconnection between the main battery 7 and the boost converter 6. The main battery 7 is connected to the low-voltage power line via the SMR 9. When the SMR 9 is in a closed state, the main battery 7 and the boost converter 6 are electrically connected by the low-power power line. When the SMR 9 is in an open state, the main battery 7 is disconnected from the boost converter 6. The SMR 9 switches between a closed state and an open state in response to a control signal from the control device 8. The SMR 9 includes a relay provided on the power line (positive bus bar PL1 of the low-voltage power line) between the positive terminal of the main battery 7 and the boost converter 6, and a relay provided on the power line (negative bus bar NL1 of the low-voltage power line) between the negative terminal of the main battery 7 and the boost converter 6.

The air conditioner 10 is connected to the low-power side power line between the SMR 9 and the boost converter 6. The air conditioner 10 includes a compressor, and operates the compressor in accordance with a control signal from the control device 8 to condition the air inside the vehicle cabin.

The auxiliary battery 11 is electrically connected to the low-voltage line EL. The auxiliary battery 11 is configured to be capable of being charged and discharged by a bidirectional DC/DC converter 12. The output voltage of the auxiliary battery 11 is lower than the output voltage of the main battery 7. The vehicle 1 is equipped with a voltage sensor that detects the voltage of the auxiliary battery 11.

The bidirectional DC/DC converter 12 is electrically connected between the positive bus PL1 and negative bus NL1 of the low-voltage side power line and the low-voltage line EL. The bidirectional DC/DC converter 12 is configured to be able to convert DC power in both directions between the low-voltage side power line connecting the SMR 9 and the boost converter 6 and the low-voltage line EL. The bidirectional DC/DC converter 12 steps down the power supplied from the low-voltage side power line and supplies it to the low-voltage line EL. The bidirectional DC/DC converter 12 steps up the power supplied from the low-voltage line EL and supplies it to the low-voltage side power line.

In the vehicle 1 equipped with the electric circuit configured in this manner, the DC power from the main battery 7 is boosted by the boost converter 6, and the boosted power is supplied to the first inverter 4 and the second inverter 5. The first inverter 4 converts the DC power supplied from the boost converter 6 into AC power and supplies it to the first motor 2. The first motor 2 is driven by the AC power supplied from the first inverter 4. Similarly, the second inverter 5 converts the DC power supplied from the boost converter 6 into AC power and supplies it to the second motor 3. The second motor 3 is driven by the AC power supplied from the second inverter 5. The first motor 2, the second motor 3, the first inverter 4, the second inverter 5, the boost converter 6, the SMR 9, and the bidirectional DC/DC converter 12 are all controlled by the control device 8.

The control device 8 is an electronic control device that controls the vehicle 1. This electronic control device is configured to include a microcontroller equipped with a CPU, RAM, ROM, and an input/output interface. The control device 8 performs signal processing according to a program pre-stored in the ROM. Signals from various sensors are input to the control device 8. Examples of signals input to the control device 8 include a voltage value from a voltage sensor that detects the voltage VB of the main battery 7, a voltage value from a voltage sensor that detects the voltage VL of the first capacitor C1 in the low-voltage power line, and a voltage value from a voltage sensor that detects the voltage VH of the second capacitor C2 in the high-voltage power line. The control device 8 then performs various controls based on the signals input from the various sensors.

For example, in the vehicle 1, during battery-less running in which the main battery 7 is disconnected as a fail-safe, the system voltage VH is maintained by the torque of the first motor 2 and the torque of the second motor 3. During battery-less running, the system voltage VH must be maintained by matching the amount of power generated and consumed (auxiliary load and drive power) through motor torque control. At that time, the control device 8 is configured to increase the system voltage VH even when the motor rotation speed is high.

Here, referring to FIG. 2, a comparison between batteryless running and normal running will be described. During batteryless running, the SMR 9 is in an open state and the main battery 7 is electrically disconnected from the second motor 3. Therefore, for example, when the motor rotation speed changes suddenly, the torque feedback control (F/B control) for balancing the power balance cannot follow well, and the DC voltage VL and the system voltage VH may drop. Normally, the DC voltage VL is maintained from the system voltage VH by the boost converter 6. In other words, when batteryless running is performed in fail-safe, the system voltage VH drops as the DC voltage VL drops. Therefore, when the DC voltage VL drops, the control device 8 supplies power to the first capacitor C1 from the bidirectional DC/DC converter 12 that is not affected by the rotation speeds of the first motor 2 and the second motor 3. That is, the bidirectional DC/DC converter 12 supplies power from the auxiliary battery 11 to the first capacitor C1 in the low-voltage side power line. In this circuit configuration, when the DC voltage VL of the first capacitor C1 on the low-voltage power line increases, the system voltage VH of the high-voltage power line increases via the diode D61 of the boost converter 6. In this way, the control of the control device 8 can increase the DC voltage VL without being affected by disturbances, and increase the system voltage VH of the second capacitor C2 via the diode D61 of the boost converter 6.

When the system voltage VH falls below the target value, control is executed to increase the power generation of the first motor 2 and reduce the power consumption of the second motor 3. However, since P = ωT, even if the motor torque (T) is changed, if the motor rotation speed (ω) fluctuates, the expected power (P) may not be obtained. This is more noticeable in systems with small capacitor capacity. Therefore, during battery-less driving, the control device 8 controls the bidirectional DC/DC converter 12 to maintain the system voltage VH using the power of the auxiliary battery 11.

Figure 3 is a flow chart showing the control during battery-less driving. The control shown in Figure 3 is performed by the control device 8.

The control device 8 determines whether or not the vehicle is running in a battery-less mode (step S1). In step S1, it is determined whether or not the SMR 9 is in an open state due to a fail-safe function and the vehicle is running using the torque of the second motor 3.

If it is determined that the vehicle is not running in battery-less mode (step S1: No), this control routine ends.

If it is determined that the vehicle is running in batteryless mode (step S1: Yes), it is determined whether the system voltage VH on the high-voltage power line and the DC voltage VL on the low-voltage power line have dropped (step S2). In step S2, it is determined whether the system voltage VH is lower than the first threshold and whether the DC voltage VL is lower than the second threshold based on the signal from the voltage sensor. This is because the lower the DC voltage VL, the lower the system voltage VH is. Therefore, it is determined whether the voltage VH of the second capacitor C2 and the voltage VL of the first capacitor C1 have dropped to below the threshold. The first threshold is a threshold used for comparison with the system voltage VH and is a preset value. This first threshold is a value greater than the second threshold. The second threshold is a threshold used for comparison with the DC voltage VL and is a preset value.

If it is determined that the system voltage VH on the high-voltage power line and the DC voltage VL on the low-voltage power line have not decreased (step S2: No), this control routine repeats the processing of step S2.

When it is determined that the system voltage VH on the high-voltage power line and the DC voltage VL on the low-voltage power line have dropped (step S2: Yes), the control device 8 supplies power from the auxiliary battery 11 to the first capacitor C1 via the bidirectional DC/DC converter 12 (step S3). In step S3, the power from the auxiliary battery 11 is boosted by the bidirectional DC/DC converter 12 and output to the low-voltage power line. In this way, the power of the auxiliary battery 11 is boosted and supplied to the first capacitor C1, thereby supplying power that increases the DC voltage VL on the low-voltage power line.

Then, the control device 8 judges whether the motor rotation speed fluctuates greatly and the DC voltage VL does not increase (step S4). In step S4, it is judged whether the rotation speeds of the first motor 2 and the second motor 3 fluctuate greatly and the voltage VL of the first capacitor C1 does not increase. The rotation speed of the first motor 2 can be calculated by the control device 8 based on an input signal from a rotation angle sensor provided in the first motor 2. The rotation speed of the second motor 3 can be calculated by the control device 8 based on an input signal from a rotation angle sensor provided in the second motor 3. The control device 8 judges whether the DC voltage VL does not increase as expected despite the processing of step S3 being performed.

If it is determined that the motor rotation speed fluctuates significantly and the DC voltage VL is not in a state of not increasing (step S4: No), the control routine returns to step S2.

If it is determined that the motor rotation speed fluctuates greatly and the DC voltage VL is not increasing (step S4: Yes), the control device 8 controls the bidirectional DC/DC converter 12 to further increase the charge amount of the first capacitor C1 (step S5). In step S5, the bidirectional DC/DC converter 12 is controlled so that the amount of power supplied from the auxiliary battery 11 to the first capacitor C1 is further increased. In step S5, the control device 8 controls the bidirectional DC/DC converter 12 so that more power is output to the low-voltage side power line than the power supplied in the processing of step S3. After the processing of step S5 is performed, this control routine ends.

As described above, according to the embodiment, when the motor rotation speed fluctuates greatly during battery-less driving, control failure can be prevented by switching the control amount of the bidirectional DC/DC converter 12. In this case, by supplying power to the first capacitor C1 from the bidirectional DC/DC converter 12, which is not affected by the motor rotation speed, the DC voltage VL can be reliably increased, and the system voltage VH can be increased via the diode D61 of the boost converter 6.

The vehicle 1 is not limited to a hybrid electric vehicle (HEV), but can also be applied to a battery electric vehicle (BEV) or a fuel cell electric vehicle (FCEV).

1 Vehicle 2 First motor (MG1)
3. Second motor (MG2)
Reference Signs List 4 First inverter 5 Second inverter 6 Boost converter 7 Main battery 8 Control device 9 System main relay 11 Auxiliary battery 12 Bidirectional DC/DC converter (bidirectional DDC)
C1 First capacitor C2 Second capacitor D61 Diode

Claims (1)

A driving motor;
an inverter that drives the driving motor;
a main battery that supplies power to the driving motor;
a boost converter that boosts the power supplied from the main battery and outputs the boosted power to the inverter;
a relay for switching between electrical connection and disconnection between the main battery and the boost converter;
a first power line connecting the relay and the boost converter;
a second power line connecting the boost converter and the inverter;
a first capacitor connected to the first power line;
a second capacitor connected to the second power line;
An auxiliary battery;
a bidirectional DC/DC converter that boosts the power from the auxiliary battery and outputs the boosted power to the first power line;
A control device for a vehicle comprising:
and controlling the bidirectional DC/DC converter to boost power from the auxiliary battery and output it to the first power line when the voltage of the first capacitor and the voltage of the second capacitor are equal to or lower than a threshold value during battery-less running in which the vehicle is running with the relay in an open state and the main battery disconnected from the traction motor.

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