JP6834911B2 - Vehicle power supply system - Google Patents

Description

The technology disclosed herein relates to a vehicle power supply system. In particular, it relates to a vehicle power supply system having a high voltage power supply for a traction motor and a low voltage power supply for an auxiliary machine.

Electric vehicles (including fuel cell vehicles and hybrid vehicles) are equipped with a high-voltage power supply (main power supply) for a traveling motor and a low-voltage power supply (auxiliary power supply) for auxiliary equipment. "Auxiliary equipment" is a general term for in-vehicle devices having an operating voltage lower than that of a traveling motor and an operating voltage of approximately 50 volts or less. The drive voltage of the traction motor is higher than 100 volts, and the output voltage of the main power supply exceeds 100 volts. That is, the output voltage of the auxiliary power supply is lower than the output voltage of the main power supply. Typical main power sources are lithium-ion batteries and fuel cells. A rechargeable secondary battery is used as the auxiliary power supply. A typical auxiliary power source is a lead battery. Patent Documents 1 and 2 exemplify such a power supply system.

The main power supply is connected to the power converter via the system main relay. The power converter converts the power of the main power source into the driving power of the traveling motor. The power converter includes a capacitor connected between the positive and negative electrodes of the main power supply. The capacitor is provided to smooth the current supplied from the main power supply, or is provided to temporarily store electric power energy in a chopper type voltage converter or the like. When the main switch of the vehicle is turned on, if the system main relay is closed and the power converter is connected to the high voltage power supply, a large current flows through the system main relay to the capacitor. If a large current suddenly flows, the system main relay may be welded. Therefore, in the power supply system of Patent Document 1, the capacitor is charged by using the auxiliary battery prior to closing the system main relay. Charging the capacitor before closing the system main relay is called precharging.

The power supply system of Patent Document 1 includes a boost converter in which the low voltage end is connected to the auxiliary power supply and the high voltage end is connected to the power converter without going through the system main relay. The controller of the power system activates the boost converter and precharges the capacitor with the power of the auxiliary power source prior to closing the system main relay.

Japanese Unexamined Patent Publication No. 2017-08810 WO2012 / 104957

The auxiliary power supply supplies power to various auxiliary machines. In addition to air conditioners, room lamps, car navigation systems, etc., various controllers including the controller of the power supply system also belong to the auxiliary equipment and receive power from the auxiliary equipment power supply. Some auxiliary machines perform initialization processing at startup when the main switch of the vehicle is turned on. If the auxiliary power supply is deteriorated, when charging of the capacitor is started, the power supplied to the other auxiliary equipment may be insufficient, and the other auxiliary equipment may not be able to complete the initialization process. The present specification provides a technique capable of determining the performance deterioration of the auxiliary power supply at the stage of precharging before closing the system main relay.

The power supply system disclosed herein includes a main power supply, an auxiliary power supply, a power converter, a relay, a boost converter, and a controller. The power converter is a device that converts the output power of the main power supply, and has a capacitor connected between the positive electrode and the negative electrode of the main power supply. The relay switches the connection and disconnection between the power converter and the mains. The output voltage of the auxiliary power supply is lower than the output voltage of the main power supply. The boost converter has a low voltage end connected to the auxiliary power supply and a high voltage end connected to the power converter without a relay. The controller operates a boost converter to charge the capacitor prior to the relay connecting the power converter to the mains. When the voltage of the auxiliary power supply falls below a predetermined voltage threshold after starting charging of the capacitor, the controller lowers the output current of the boost converter until the voltage of the auxiliary power supply recovers to the voltage threshold. In the controller, if the output current falls below the predetermined first current threshold value before the auxiliary power supply voltage recovers to the threshold voltage, and the auxiliary power supply current falls below the predetermined second current threshold value, the auxiliary power supply is abnormal. Outputs a signal to notify.

In the power supply system disclosed herein, the controller monitors the voltage of the auxiliary power supply after starting charging of the capacitor. Then, the output current of the boost converter is lowered so that the voltage of the auxiliary power supply does not fall below a predetermined voltage threshold value. The controller compensates when the voltage of the auxiliary power supply does not recover even if the output current of the boost converter is lowered to the predetermined first current threshold value, and the current of the auxiliary power supply is lower than the predetermined second current threshold value. It is determined that the machine power supply has deteriorated, and a signal is output to notify the abnormality of the auxiliary machine power supply. This power supply system can detect deterioration of the auxiliary power supply before closing the relay. The voltage threshold value to be compared with the voltage of the auxiliary power supply is preset to a value higher than the voltage required for initializing the main devices of the vehicle. The first current threshold is preset to the output current value of the boost converter that can determine whether or not the performance of the auxiliary power supply is within the normal range. The second current threshold value is preset by multiplying the estimated value of the total current consumption consumed by the auxiliary machine in the initialization operation or the like when the main switch of the vehicle is turned on by the safety factor. The current of the auxiliary power supply is compared with the second current threshold when the auxiliary power supply consumes more current than expected, for example, when the air conditioner is operating at the maximum output. This is because a sufficient precharge current may not be supplied even if it is not deteriorated. The reason why the current of the auxiliary power supply is compared with the second current threshold value is to prevent erroneous determination that the auxiliary power supply is deteriorated in the above case. An example of a signal for notifying an abnormality of the auxiliary power supply is a command signal for lighting the warning lamp of the auxiliary power supply abnormality to the instrument panel.

Details of the techniques disclosed herein and further improvements will be described in the "Modes for Carrying Out the Invention" below.

It is a block diagram of the electric power system of the hybrid vehicle including the power supply system of an Example. It is a flowchart of the precharge process executed by a controller.

The power supply system 10 of the embodiment will be described with reference to the drawings. The power supply system 10 of the embodiment is mounted on the hybrid vehicle 100. FIG. 1 shows a block diagram of an electric power system of a hybrid vehicle 100 including a power supply system 10. The hybrid vehicle 100 includes a traveling motor 50 and an engine 51. The output torque of the traveling motor 50 and the output torque of the engine 51 are combined by the gear set 52 and transmitted to the axle 53.

The hybrid vehicle 100 includes a power supply system 10, a traveling motor 50, an engine 51, a main switch 41, an instrument panel 42, an engine controller 32, an air conditioner 33, and a car navigation system 34. The engine controller 32, the air conditioner 33, and the car navigation system 34 receive electric power from the auxiliary battery 15 through the auxiliary power line 31. As will be described in detail later, the controller 13 included in the power supply system 10 also receives power from the auxiliary battery 15. Auxiliary equipment A generic term for devices that receive power from the battery 15 is "auxiliary equipment." In the following, when auxiliary machines such as the engine controller 32, the air conditioner 33, the car navigation system 34, and the controller 13 are collectively referred to as the auxiliary machine 30, it is referred to as the auxiliary machine 30.

The power supply system 10 is a system that supplies electric power to the traveling motor 50 and the auxiliary equipment 30. The power supply system 10 includes a main battery 11, an auxiliary battery 15, a system main relay 12, a power converter 20, a boost converter 14, and a controller 13.

The main battery 11 is mainly a power source for the traveling motor 50. The main battery 11 is, for example, a rechargeable lithium-ion battery. The output voltage of the main battery 11 is, for example, 200 volts.

As described above, the auxiliary battery 15 is a power source for supplying electric power to the auxiliary machine 30. The output voltage of the auxiliary battery 15 is lower than the output voltage of the main battery 11, for example, 12 volts, 24 volts, or 48 volts. The auxiliary battery 15 is also a rechargeable secondary battery, for example, a lead battery. The auxiliary battery 15 supplies electric power to a large number of auxiliary machines (not shown) via the auxiliary power lines 31 stretched around the vehicle. The negative electrode of the auxiliary battery 15 and the negative electrode of the auxiliary machine 30 are connected via the ground. In the auxiliary power system, the body of the vehicle corresponds to the ground terminal.

The power converter 20 is connected to the main battery 11 via the system main relay 12. The power converter 20 converts the output power of the main battery 11 into the drive power of the traveling motor 50. The power converter 20 includes a bidirectional DC-DC converter circuit 21, an inverter circuit 22, and a capacitor 23. The drive voltage of the traveling motor 50 is between 200 and 600 volts. When the drive voltage target of the traveling motor 50 is higher than the output voltage of the main battery 11, the bidirectional DC-DC converter circuit 21 boosts the output voltage of the main battery 11 to the driving voltage of the traveling motor 50. The inverter circuit 22 converts the boosted DC power into AC power for driving the traveling motor 50. Hereinafter, for convenience of explanation, the bidirectional DC-DC converter circuit 21 is simply referred to as a bidirectional converter circuit 21.

When the driver depresses the brake pedal, the traveling motor 50 generates electricity by utilizing the inertial force of the vehicle. The electric power generated by the traveling motor 50 is called regenerative electric power. The inverter circuit 22 can also convert AC regenerative power into DC power and send it to the bidirectional converter circuit 21. The bidirectional converter circuit 21 steps down the regenerative power converted into DC power to the voltage of the main battery 11. The main battery 11 is charged with the reduced regenerative power.

The circuit configuration of the bidirectional converter circuit 21 will be described. The bidirectional converter circuit 21 is composed of two transistors 211 and 212, two diodes 215 and 216, a reactor 213, and a capacitor 214. The two transistors 211 and 212 are connected in series between the terminals (positive electrode terminal 203 and negative electrode terminal 204) on the inverter side of the bidirectional converter circuit 21. The diode 215 is connected to the transistor 211 in antiparallel and the diode 216 is connected to the transistor 212 in antiparallel. The diodes 215 and 216 are provided to bypass the off transistors 211 and 212 to allow current to flow.

One end of the reactor 213 is connected to the midpoint of the series connection of the transistors 211 and 212, and the other end is connected to the positive electrode terminal 201 on the battery side of the bidirectional converter circuit 21. The capacitor 214 is connected between the positive electrode terminal 201 and the negative electrode terminal 202 on the battery side of the bidirectional converter circuit 21. The negative electrode terminal 202 on the battery side and the negative electrode terminal 204 on the inverter side of the bidirectional converter circuit 21 are directly connected.

The transistor 211 on the positive electrode side of the series connection is mainly involved in the step-down operation, and the transistor 212 on the negative electrode side is mainly involved in the step-up operation. Since the circuit configuration and operation of the bidirectional converter circuit 21 of FIG. 1 are well known, detailed description thereof will be omitted.

The capacitor 214 serves to temporarily store electrical energy in the bidirectional converter 21 circuit. A capacitor 23 for smoothing the current sent from the main battery 11 is connected in parallel between the bidirectional converter circuit 21 and the inverter circuit 22. As shown in FIG. 1, the capacitors 214 and 23 are connected between the positive electrode and the negative electrode of the main battery 11 via the system main relay 12.

The system main relay 12 is a switch for connecting and disconnecting between the power converter 20 and the main battery 11. The system main relay 12 is controlled by the controller 13 of the power supply system 10. When the main switch 41 of the vehicle is turned on, the controller 13 closes the system main relay 12 after precharging the capacitors 214 and 23 (described later), and connects the power converter 20 to the main battery 11. The dotted arrow line in FIG. 1 represents a signal line.

In the boost converter 14, the low voltage end 142 is connected to the auxiliary battery 15, and the high voltage end 141 is connected to the power converter 20 on the power converter 20 side of the system main relay 12. In other words, the high voltage end 141 of the boost converter 14 is connected to the power converter 20 without going through the system main relay 12. The boost converter 14 can boost the output voltage of the auxiliary battery 15 and supply it to the power converters 20 (capacitors 214 and 23).

The controller 13 controls the system main relay 12 and the boost converter 14. The controller 13 includes a CPU 131 and a memory 132, and the CPU 131 can execute various processes by executing the program stored in the memory 132. The power supply system 10 includes a voltage sensor 17 that measures the voltage of the auxiliary battery 15 and a current sensor 16 that measures the current of the auxiliary battery 15, and the data of these sensors is sent to the controller 13. The controller 13 is also connected to the instrument panel 42, and when it detects an abnormality in the auxiliary battery 15 described later, it outputs a signal (abnormality notification signal) for notifying the abnormality to the instrument panel 42. Upon receiving the abnormality notification signal, the instrument panel 42 lights a lamp for notifying the occupant of the abnormality of the auxiliary battery 15.

As can be seen from the block diagram of FIG. 1, when the system main relay 12 is closed, the current of the main battery 11 flows into the capacitors 214 and 23 of the power converter 20. Even if the transistor 211 is off, the current of the main battery 11 flows into the capacitor 23 through the diode 215. When the system main relay 12 is closed with the capacitors 214 and 23 completely discharged, the current of the main battery 11 suddenly flows into the capacitors 214 and 23 through the system main relay 12. If a large current flows through the system main relay 12, the system main relay 12 may be welded. Therefore, when the main switch 41 is turned on, the controller 13 charges the capacitors 214 and 23 in advance using the auxiliary battery 15 and the boost converter 14 prior to closing the system main relay 12. Charging the capacitors 214 and 23 before closing the system main relay 12 is called precharging.

A corresponding amount of electric power is required to charge the capacitors 214 and 23. Further, after the main switch 41 of the vehicle is turned on, the system main relay 12 cannot be closed unless the precharge is completed. Therefore, precharging should be achieved as quickly as possible using a large current.

On the other hand, when the main switch 41 of the vehicle is turned on, various auxiliary machines in the vehicle perform initialization processing at startup. As mentioned above, the various auxiliary machines operate by receiving power from the auxiliary battery 15. For example, the engine controller 32 performs a self-check of its own circuit and a confirmation of energization of the injector device of the engine 51 as an initialization process at the time of startup. In addition, the electric shift device belonging to the auxiliary machine operates an actuator that moves the shift lever in order to reset the shift position to the zero point. In addition, the electronically controlled brake device belonging to the auxiliary machine accumulates preliminary pressure in the accumulator.

If the performance of the auxiliary battery 15 is deteriorated, the power supplied to the other auxiliary equipment may be insufficient due to the start of charging of the capacitors 214 and 23, and the initialization process may not be completed. Therefore, the controller 13 of the power supply system 10 of the embodiment is equipped with a process of determining the performance deterioration of the auxiliary battery 15 at the time of precharging.

The precharge process executed by the controller 13 will be described with reference to FIG. FIG. 2 is a flowchart of the precharge process. The process of FIG. 2 is started when the main switch 41 of the vehicle is turned on. The controller 13 activates the boost converter 14 to start precharging (step S2). Next, the controller 13 acquires the output voltage (voltage Vd) of the auxiliary battery 15 from the voltage sensor 17 and the output current (current Id) of the auxiliary battery 15 from the current sensor 16 (step S3).

Next, the controller 13 compares the voltage Vd of the auxiliary battery 15 with the voltage threshold Vx (step S4). The voltage threshold value Vx is set to a voltage value required for initializing a specific auxiliary machine that receives power from the auxiliary machine battery 15, such as the engine controller 32. When the voltage Vd of the auxiliary battery 15 being precharged exceeds the voltage threshold value Vx (step S4: YES), the controller 13 continues precharging (step S5). The controller 13 repeatedly monitors the voltage Vd of the auxiliary battery 15 and compares it with the voltage threshold Vx (step S5: NO, step S3) until the precharge is completed. When the precharge is completed, the controller 13 stops the boost converter 14 and ends the precharge process (steps S5: YES, S6). When the precharge is complete, the controller 13 closes the system main relay 12 and connects the power converter 20 to the main battery 11. When the power converter 20 is connected to the main battery 11, the hybrid vehicle 100 is ready to travel.

Since the capacitors 214 and 23 are charged by precharging, a large inrush current does not flow when the system main relay 12 is closed. In precharging, it is desirable to charge the capacitors 214 and 23 to a voltage equivalent to the output voltage of the main battery 11. In the precharge, the controller 13 sets the target voltage on the output side of the boost converter 14 to a voltage equivalent to the output voltage of the main battery 11. It is desirable that the capacitors 214 and 23 be charged to a voltage equivalent to the output voltage of the main battery 11, but the capacitors may be charged to a predetermined ratio with respect to the voltage of the main battery 11.

On the other hand, when the voltage Vd of the auxiliary battery 15 after the start of precharging is lower than the voltage threshold Vx (step S4: NO), the controller 13 lowers the output current of the boost converter 14 (step S7). Next, the controller 13 compares the output current Ip of the boost converter 14 with the first current threshold value Ipd, and compares the current Id of the auxiliary battery 15 with the second current threshold value Ix (step S8). The first current threshold value Ipd is preset to the output current value of the boost converter 14 that can determine whether or not the performance of the auxiliary battery 15 is within the normal range. That is, if the output current Ip of the boost converter 14 exceeds the first current threshold value Ipd (step S8: NO), it can be determined that the performance of the auxiliary battery 15 has not deteriorated. The boost converter 14 includes a current sensor (not shown) for measuring the output current, and the controller 13 can acquire the measured value of the output current from the boost converter 14.

On the other hand, the second current threshold value Ix is set to a value obtained by multiplying the total current consumption of the initialization process of the auxiliary machine 30 which can be normally assumed such as the engine controller 32 by a predetermined safety factor (for example, 1.2). There is. The current Id of the auxiliary battery 15 is compared with the second current threshold Ix when the boost converter 14 outputs when the current Id of the auxiliary battery 15 is within the total current consumption of the normal auxiliary battery 30 that can be assumed. This is to determine whether or not the first current threshold value Ipd can be secured as the current.

For example, when the total current consumption of the auxiliary machine is larger than expected, such as when the air conditioner 33 is operating at the maximum output, the first output current of the boost converter 14 is set even if the auxiliary machine battery 15 maintains the normal capacity. There is a possibility that the current threshold Ipd cannot be secured. When the current Id of the auxiliary battery 15 exceeds the second current threshold value Ix, the determination in step S8 is NO. In this case, even if the output current Ip of the boost converter 14 is set to a value lower than the first current threshold value Ipd, the controller 13 secures the output voltage Vd exceeding the voltage threshold value Vx (step S4: YES) and pre-installs it. Continue charging.

If the output current Ip of the boost converter 14 exceeds the first current threshold value Ipd, or the current Id of the auxiliary battery 15 exceeds the second current threshold value Ix (step S8: NO), the controller 13 determines. The process returns to step S3. That is, the controller 13 again acquires the voltage Vd of the auxiliary battery 15, and compares the voltage Vd with the voltage threshold Vx (steps S3 and S4). When the voltage Vd of the auxiliary battery 15 recovers to the voltage threshold Vx (step S4: YES), the controller 13 continues precharging. That is, when the voltage Vd of the auxiliary battery 15 falls below the voltage threshold Vx after starting the precharge, the controller 13 lowers the output current Ip of the boost converter 14 until the voltage Vd recovers to the voltage threshold Vx. When the voltage Vd recovers to the voltage threshold Vx, precharging is continued at the output current Ip of the boost converter 14 at that time.

By lowering the output current of the boost converter 14, the output current falls below the first current threshold Ipd before the voltage Vd of the auxiliary battery 15 recovers to the voltage threshold Vx, and the current Id of the auxiliary battery 15 becomes the second. If it is below the current threshold Ix (step S8: YES), the controller 13 determines that the output of the auxiliary battery 15 is insufficient. In this case, the controller 13 outputs an abnormality notification signal for notifying the abnormality of the auxiliary battery 15 to the instrument panel 42 (step S9). As described above, the instrument panel 42 that has received the abnormality notification signal lights the lamp that notifies the occupant of the abnormality.

The controller 13 executes a predetermined error response process (step S10) and ends the process of FIG. In the error response process (step S10), for example, a signal indicating that the output of the auxiliary battery 15 is insufficient to complete the initialization of the system of the entire vehicle is transmitted to the instrument panel, and a diagnostic memory (not shown) is used. Stores message data notifying the abnormality of the auxiliary battery 15. The diagnostic memory is a memory that the staff refers to during vehicle maintenance, and the staff can grasp the state of the vehicle by looking at the data in the diagnostic memory.

As described above, the power supply system 10 can determine the performance deterioration of the auxiliary battery 15 at the precharge stage before closing the system main relay. Whether or not the performance of the auxiliary battery 15 has deteriorated is determined by multiplying the assumed total current consumption of the auxiliary machine by the safety factor (that is, the second) of the current Id of the auxiliary battery 15 during precharging. If it is larger than the current threshold Ix), it is not performed. This is because if the total current consumption of the auxiliary machine is larger than expected, it may not be possible to secure a sufficient current for quick precharging even if the performance of the auxiliary machine battery 15 is within the normal range.

The first current threshold Ipd for determining whether the performance of the auxiliary battery 15 is within the normal range is set to a value at which it is determined that the performance deterioration of the auxiliary battery 15 is not so serious as to completely stop the vehicle system. If it is set, the precharge may be continued instead of the process of step S10. In that case, it is preferable that another function capable of determining the severe deterioration of the auxiliary battery 15 is added.

The points to be noted regarding the technique described in the examples will be described. A branch process may be provided between steps S4 and S7 of FIG. 2 or between steps S7 and S8 to shift to another error response process when the output current Ip is zero. In this process, even if the current Id of the auxiliary battery 15 exceeds the second current threshold value (step S8: NO) and the output current Ip of the boost converter 14 continues to be lowered, the voltage Vd of the auxiliary battery 15 remains voltage. This is a measure when the threshold Vx is not recovered. If the voltage Vd of the auxiliary battery 15 does not recover the voltage threshold Vx even if the output current Ip of the boost converter 14 is lowered to zero, there is a possibility that the auxiliary battery 15 does not have enough power to initialize the vehicle system. In such a case, some measures are taken by another emergency response process.

The boost converter 14 may be a bidirectional DC-DC converter. In that case, after closing the system main relay 12, the power of the main battery 11 can be stepped down to charge the auxiliary battery 15.

The vehicle of the embodiment was a hybrid vehicle including a motor 50 and an engine 51. The vehicle power supply system disclosed herein can also be applied to fuel cell vehicles and electric vehicles without an engine.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described herein or in the drawings exhibit their technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in the present specification or drawings can achieve a plurality of purposes at the same time, and achieving one of the purposes itself has technical usefulness.

10: Power supply system 11: Main battery 13: Controller 14: Boost converter 15: Auxiliary battery 16: Current sensor 17: Voltage sensor 20: Power converter 21: Bidirectional DC-DC converter circuit 22: Inverter circuit 23: Capacitor 30 : Auxiliary machine 31: Auxiliary machine power line 32: Engine controller 33: Air conditioner 34: Car navigation 41: Main switch 42: Instrument panel 50: Driving motor 51: Engine 100: Hybrid vehicle

Claims (1)

Main power supply and
A power converter that converts the output power of the main power supply and has a capacitor connected between the positive electrode and the negative electrode of the main power supply.
A relay that switches the connection and disconnection between the power converter and the main power supply,
Auxiliary power supply whose output voltage is lower than the output voltage of the main power supply,
A boost converter whose low voltage end is connected to the auxiliary power supply and whose high voltage end is connected to the power converter without the relay.
A controller that operates the boost converter to charge the capacitor prior to closing the relay.
Is equipped with
When the voltage of the auxiliary power supply falls below a predetermined voltage threshold after starting charging of the capacitor, the controller outputs current of the boost converter until the voltage of the auxiliary power supply recovers to the voltage threshold. The output current falls below the predetermined first current threshold before the voltage of the auxiliary power supply recovers to the voltage threshold, and the current of the auxiliary power supply falls below the predetermined second current threshold. A power supply system for vehicles that outputs a signal notifying the abnormality of the auxiliary power supply.

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