JP2019146459A - Vehicle power supply system - Google Patents

Abstract

To prevent operation of an auxiliary machine 30 from being destabilized in performing precharge using a power supply of an auxiliary machine battery 15.SOLUTION: A power supply system 2 includes a controller 13 for actuating a step-up converter 14 prior to closing a relay 12 to perform precharge on capacitors 214, 23 of a power converter 20. The controller 13, prior to the precharge, acquires voltage differences between measured values of second voltage sensors 19a-19c and minimum operation voltage of an auxiliary machine 30 and acquires a measured value (voltage before precharge) of a first voltage sensor 18. During the precharge, the controller 13 adjusts output of the step-up converter 14 so that the measured value of the first voltage sensor 18 is not smaller than a value obtained by subtracting the minimum value of the voltage differences from the voltage before precharge.SELECTED DRAWING: Figure 1

Description

  The technology disclosed in this specification relates to a power supply system for a vehicle. In particular, the present invention relates to a power supply system including a high voltage power supply for a traveling motor and a low voltage power supply for an auxiliary machine.

  An electric vehicle (including a fuel cell vehicle and a hybrid vehicle) includes a high voltage power source (main power source) for a traveling motor and a low voltage power source (auxiliary power source) for an auxiliary machine. “Auxiliary equipment” is an in-vehicle device that operates at a voltage lower than the voltage of the traveling motor, and is a generic term for an in-vehicle device whose operating voltage is approximately 50 volts or less. The driving voltage of the traveling motor is greater 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 adopted as the auxiliary power source. A typical auxiliary power supply is a lead battery. Patent Documents 1 and 2 exemplify such a power supply system.

  The main power source 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 electrode and the negative electrode of the main power supply. The capacitor is provided for smoothing the current supplied from the main power supply, and is provided for temporarily storing power energy in a chopper type voltage converter or the like. When the main switch of the vehicle is switched from OFF to ON, when the system main relay is closed and the power converter is connected to the high voltage power source, a large current flows to the capacitor through the system main relay. If a large current suddenly flows, the system main relay may be welded. Therefore, in the power supply systems of Patent Documents 1 and 2, before switching the system main relay to the connected state, the capacitor is charged using the auxiliary power supply. Charging the capacitor before switching the system main relay from the open state to the connected state is called precharge.

  The power supply systems of Patent Documents 1 and 2 include a boost converter in which a low voltage end is connected to an auxiliary power supply and a high voltage end is connected to a power converter without passing through a system main relay. Prior to switching the system main relay to the connected state, the controller of the power supply system operates the boost converter and precharges the capacitor with the power of the auxiliary power supply.

  In the power supply system of Patent Document 2, the auxiliary equipment required for precharging is allowed to start and the other auxiliary machines are prohibited from starting so that the precharge can be executed even when the auxiliary power supply is low.

JP 2017-085810 A JP 2016-1335010 A

  The auxiliary power supply supplies power to various auxiliary machines. In addition to air conditioners, room lamps, car navigation systems, and the like, various controllers including a controller of the power supply system also belong to the auxiliary machine and operate by receiving power supply from the auxiliary machine power supply. The precharge should be completed as soon as possible. However, if the precharge is performed at a high speed, the boost converter requires a large current, and as a result, the voltage of the auxiliary battery decreases. When the voltage of the auxiliary battery decreases, the operation of main auxiliary machines such as the controller of the power supply system may become unstable. This specification provides a technique for preventing the operation of an auxiliary machine from becoming unstable when precharging using an auxiliary machine power supply.

  The power supply system disclosed in this specification includes a main power supply, an auxiliary power supply, a power converter, a relay, a boost converter, a controller, a first voltage sensor, and a second voltage sensor. The power converter is a device that converts the output power of the main power supply, and includes a capacitor connected between the positive electrode and the negative electrode of the main power supply. The relay switches between connection and disconnection between the power converter and the main power source. The auxiliary power supply has an output voltage lower than that 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 the boost converter to precharge the capacitor prior to switching the relay to the connected state. The first voltage sensor measures the voltage at the low voltage end of the boost converter. The second voltage sensor measures the input voltage of the auxiliary machine that operates by receiving power supply from the auxiliary machine power supply. A second voltage sensor is provided for each of the plurality of auxiliary machines.

  Prior to precharging, the controller acquires a voltage difference (margin voltage difference) between the measured value of the second voltage sensor and the minimum operating voltage of the auxiliary device for each of the plurality of operating auxiliary devices, The measurement value (voltage before precharge) of the first voltage sensor is acquired. During the precharge, the controller outputs the boost converter so that the measured value of the first voltage sensor (that is, the voltage at the low voltage end) does not fall below the value obtained by subtracting the minimum margin voltage difference from the pre-charge voltage. Adjust.

  The power supply system disclosed in this specification monitors the input voltage of each auxiliary machine that is operating during precharge with a second voltage sensor, and boosts the input voltage so that it does not fall below the minimum operating voltage of the auxiliary machine. Adjust the output of the converter. Therefore, the operation of the auxiliary machine does not become unstable during precharging. In the power supply system disclosed in this specification, in particular, the input voltage of each auxiliary machine is measured by the second voltage sensor, so that the auxiliary machine is not considered in consideration of the voltage drop between the auxiliary machine power supply and each auxiliary machine. Prevent stabilization. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric power system of the hybrid vehicle containing the power supply system of an Example. It is a flowchart of a precharge pre-process. It is a flowchart of a precharge process.

  A power supply system 10 according to an embodiment will be described with reference to the drawings. The power supply system 10 according to the embodiment is mounted on the hybrid vehicle 100. FIG. 1 shows a block diagram of a 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 is provided with a main switch 41, an engine controller 32, an air conditioner 33, and a car navigation 34 in addition to the power supply system 10, the traveling motor 50 and the engine 51. The engine controller 32, the air conditioner 33, and the car navigation system 34 are supplied with power from the auxiliary battery 15 through the auxiliary power line 31. As will be described in detail later, the controller 13 provided in the power supply system 10 also receives power from the auxiliary battery 15. A generic term for devices that receive power supply from the auxiliary battery 15 is “auxiliary”. Hereinafter, auxiliary equipment such as the engine controller 32, the air conditioner 33, the car navigation system 34, and the controller 13 are collectively referred to as auxiliary equipment 30.

  The power supply system 10 is a system that supplies power to the motor 50 and the auxiliary machine 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 power supply system 10 includes a first voltage sensor 18 and a plurality of second voltage sensors 19a-19c.

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

  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 an auxiliary power line 31 stretched around the vehicle. Note that the negative electrode of the auxiliary battery 15 and the negative electrode of the auxiliary machine 30 are connected via a ground. In the auxiliary power system, the vehicle body 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 driving power for the motor 50. The power converter 20 includes a bidirectional DC-DC converter circuit 21, an inverter circuit 22, and a capacitor 23. The driving voltage of the motor 50 is between 200 volts and 600 volts. When the drive voltage target of the 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 drive voltage of the motor 50. The inverter circuit 22 converts the boosted DC power into AC power for driving the 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 steps on the brake pedal, the motor 50 generates power using the inertial force of the vehicle. The electric power generated by the motor 50 is referred to as 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 to DC power to the voltage of the main battery 11. The main battery 11 is charged with the reduced regenerative power.

  A circuit configuration of the bidirectional converter circuit 21 will be described. The bidirectional converter circuit 21 includes 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 terminals on the inverter side of the bidirectional converter circuit 21 (positive terminal 203 and negative terminal 204). 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 transistors 211 and 212 when they are off and 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 terminal 201 on the battery side of the bidirectional converter circuit 21. The capacitor 214 is connected between the positive terminal 201 and the negative terminal 202 on the battery side of the bidirectional converter circuit 21. The battery-side negative terminal 202 and the inverter-side negative terminal 204 of the bidirectional converter circuit 21 are directly connected.

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

  The capacitor 214 serves to temporarily store electric energy in the bidirectional converter 21 circuit. A capacitor 23 that smoothes 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 that connects or disconnects 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 switched on, the controller 13 closes the system main relay 12 after the capacitors 214 and 23 are precharged (described later), and connects the power converter 20 to the main battery 11. A dotted arrow line in FIG. 1 represents a signal line.

  Boost converter 14 has a low voltage end 142 connected to auxiliary battery 15 and a high voltage end 141 connected to power converter 20 on the power converter 20 side of system main relay 12. In other words, the high voltage terminal 141 of the boost converter 14 is connected to the power converter 20 without passing through the system main relay 12. Boost converter 14 can boost the output voltage of auxiliary battery 15 and supply it to power converter 20 (capacitors 214, 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 various processes can be executed by the CPU 131 executing a program stored in the memory 132.

  The power supply system 10 includes a first voltage sensor 18 that measures the voltage at the low voltage end 142 of the boost converter 14, and second voltage sensors 19 a to 19 c that measure the input voltage of each auxiliary machine 30. Is sent to the controller 13. Although not shown, a second voltage sensor is also provided at the power input terminal of the controller 13 belonging to the auxiliary machine and other main auxiliary machines. Further, although not shown, a voltage sensor is also connected between the positive electrode terminal 201 and the negative electrode terminal 202 on the battery side of the bidirectional converter circuit 21, and measurement data of the voltage sensor is also sent to the controller 13. . A voltage sensor between the positive terminal 201 and the negative terminal 202 measures the voltage across the capacitors 214 and 23 in a precharge process to be described later.

  As understood from the block diagram of FIG. 1, when the system main relay 12 is switched from the open state (open) to the connected state (closed), the power converter 20 is connected to the main battery 11 and the current of the main battery 11 is Flows into the capacitors 214 and 23 of the power converter 20. Even when 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 switched to the connected state 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 switched from OFF to ON, the controller 13 switches the auxiliary battery 15 and the boost converter 14 before switching the system main relay 12 from the open state (open) to the connected state (closed). Is used to charge the capacitors 214 and 23 in advance. The charging of the capacitors 214 and 23 before switching the system main relay 12 to the connected state is referred to as precharging.

  After the main switch 41 of the vehicle is switched from OFF to ON, the system main relay 12 cannot be switched to the connected state unless precharging is completed. Therefore, it is desirable that the precharge is achieved promptly.

  On the other hand, a large current is required to perform precharging at high speed. When the boost converter 14 for precharging consumes a large current, the voltage of the auxiliary battery 15 decreases. If the voltage of the auxiliary battery 15 is too low, the operation of the auxiliary machine 30 may become unstable. The auxiliary machine 30 includes important devices such as the controller 13 of the power supply system 10 and the engine controller 32. The power supply system 10 according to the embodiment can perform precharge without reducing the voltage of the auxiliary battery 15 to such an extent that the auxiliary machine 30 becomes unstable. Hereinafter, the precharge process performed by the power supply system 10 will be described.

  Prior to the precharge, the controller 13 executes the process shown in FIG. 2 (precharge preprocess). The flowchart of FIG. 2 will be described.

  The controller 13 acquires the voltage (input voltage) at the input end of each auxiliary machine 30 from the second voltage sensors 19a-19c (step S2). As described above, even for the auxiliary machine not shown in FIG. 1, the main auxiliary machine is provided with the second voltage sensor, and the controller 13 receives each auxiliary machine from the second voltage sensor. Get the input voltage. In addition, auxiliary machines that are not operating before precharging and auxiliary machines with low power consumption are not subject to input voltage acquisition.

  The power input terminal of the auxiliary machine 30 is connected to the auxiliary machine power line 31, but the voltage input to each auxiliary machine 30 due to the internal resistance of the auxiliary machine power line 31 is higher than the output voltage of the auxiliary machine battery 15. Lower. Further, the voltage input to each auxiliary machine 30 differs depending on the auxiliary machine depending on the length of the power line between the auxiliary battery 15. The power supply system 10 according to the embodiment precharges the auxiliary machine 30 so as not to become unstable in consideration of a difference in input voltage that is different for each auxiliary machine.

  The controller 13 stores in advance data on the minimum operating voltage of each auxiliary machine. The “minimum operating voltage” means a voltage at which the operation of the auxiliary machine becomes unstable or the operation of the auxiliary machine stops when the voltage input to the auxiliary machine falls below the value. The minimum operating voltage is a value unique to each auxiliary machine and is stored in the controller 13 in advance.

  The controller 13 calculates the voltage difference dV between the input voltage before precharging (that is, the measured value of each second voltage sensor 19a-19c) and the minimum operating voltage for each auxiliary machine 30 (step S3). Hereinafter, the voltage difference dV between the input voltage before precharging and the minimum operating voltage of each auxiliary machine may be referred to as a margin voltage difference dV. The “margin voltage difference dV” has a technical meaning that when the input voltage falls below the voltage difference dV, the operation of the accessory may become unstable. The controller 13 specifies the minimum voltage difference dVmin from the plurality of margin voltage differences dV (step S4). The minimum voltage difference dVmin is expressed as a minimum margin dVmin below.

  The controller 13 acquires the voltage at the low voltage end 142 of the boost converter 14 before precharging (step S5). The voltage at the low voltage end 142 can be obtained from the first voltage sensor 18. At this point, boost converter 14 is not operating. Hereinafter, the voltage at the low voltage terminal 142 of the boost converter 14 before the precharge is expressed as a precharge voltage Vdc0.

  When the precharge preprocessing in FIG. 2 is completed, the controller 13 continues to execute the precharge process. FIG. 3 shows a flowchart of the precharge process.

  The precharge process will be described with reference to FIG. The controller 13 activates the boost converter (step S12). When the boost converter 14 is activated, a current is output from the high voltage terminal 141, and the capacitors 214 and 23 start to be charged.

  The controller 13 acquires the voltage Vdc of the low voltage end 142 of the boost converter 14 during precharging (step S13). The controller 13 acquires the voltage Vdc of the low voltage end 142 from the first voltage sensor 18. When boost converter 14 is activated, a current flows from auxiliary battery 15 to boost converter 14, so that the voltage of auxiliary battery 15 decreases and voltage Vdc at low voltage terminal 142 also becomes lower than pre-charge voltage Vdc0. When the voltage Vdc at the low voltage end 142 (that is, the measured value of the first voltage sensor 18) falls below the value obtained by subtracting the minimum margin dVmin from the pre-charge voltage Vdc0 (step S14: NO), the controller 13 14 is lowered (step S15). When the output of boost converter 14 is lowered, the current flowing from auxiliary battery 15 to boost converter 14 decreases, so that voltage Vdc at low voltage end 142 increases.

  The controller 13 gradually decreases the output of the boost converter 14 until the voltage Vdc at the low voltage end 142 (that is, the measured value of the first voltage sensor 18) exceeds the value obtained by subtracting the minimum margin dVmin from the precharge voltage Vdc0. . When the voltage Vdc at the low voltage terminal 142 exceeds the value obtained by subtracting the minimum margin dVmin from the pre-charge voltage Vdc0 (step S14: YES), the controller 13 continues to drive the boost converter 14 until the precharge is completed. During the precharge, the controller 13 monitors the voltage Vdc (that is, the measured value of the first voltage sensor 18) at the low voltage terminal 142 (step S13), so that the voltage Vdc does not always fall below “Vdc0−dVmin”. Then, the output voltage of the boost converter 14 is adjusted (step S14: NO, S15).

  As described above, the power supply system 2 includes the voltage sensor that measures the voltage across the capacitors 214 and 23, and the controller 13 determines that the voltage across the capacitors 214 and 23 is close to the voltage of the main battery 11. Then complete the precharge. The controller 13 ends precharging when the voltage across the capacitors 214 and 23 reaches, for example, 80% of the voltage of the main battery 11 (step S16: YES). When the precharge is completed, the controller 13 stops the boost converter 14 (step S17).

  When the precharge is completed, the controller 13 closes the system main relay 12 and connects the main battery 11 to the power converter 20. Since the capacitors 214 and 23 are charged to a predetermined voltage, a large current does not flow even when the system main relay 12 is closed. When the main battery 11 is connected to the power converter 20, the motor 50 is in a drivable state.

  If the voltage Vdc at the low voltage end 142 of the boost converter 14 falls below “Vdc0−dVmin”, the input voltage of any one of the auxiliary machines 30 falls below the minimum operating voltage. As a result, the operation of the auxiliary machine 30 may become unstable. Since the power supply system 10 of the embodiment adjusts the output of the boost converter 14 so that the input voltage of the auxiliary machine 30 does not fall below the minimum operating voltage, the operation of the auxiliary machine does not become unstable.

  Points to be noted regarding the technology described in the embodiments will be described. The second voltage sensor may be built in the auxiliary machine.

  Boost converter 14 may be a bidirectional DC-DC converter. In that case, after the system main relay 12 is switched to the connected state, the power of the main battery 11 can be stepped down to charge the auxiliary battery 15.

  The precharge process described in the embodiment may be executed by a plurality of computers that can communicate with each other via an in-vehicle network. That is, the actual state of the controller 13 described in the embodiment may be a plurality of computers connected to be able to communicate with each other via a network.

  The vehicle of the example was a hybrid vehicle including a traveling motor 50 and an engine 51. The vehicle power supply system disclosed in the present specification can be applied to a fuel cell vehicle and an electric vehicle that does not include an engine.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit 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 technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: Power supply system 11: Main battery 13: Controller 14: Boost converter 15: Auxiliary battery 18: First voltage sensor 19a-19c: Second 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 50: motor 51: engine 100: hybrid vehicle

Claims (1)

A main power supply,
A power converter for converting the output power of the main power supply, the power converter having a capacitor connected between a positive electrode and a negative electrode of the main power supply;
A relay for switching between connection and disconnection between the power converter and the main power source;
An auxiliary power source whose output voltage is lower than the output voltage of the main power source,
A boost converter in which a low voltage end is connected to the auxiliary power source, and a high voltage end is connected to the power converter without going through the relay;
A first voltage sensor for measuring a voltage at the low voltage end of the boost converter;
A plurality of second voltage sensors for measuring respective input voltages of a plurality of auxiliary machines operating by receiving power supply from the auxiliary power supply;
A controller for precharging the capacitor by operating the boost converter prior to connecting the relay;
With
Prior to the precharge, the controller
For each of the plurality of auxiliary machines in operation, the voltage difference between the measured value of the second voltage sensor and the minimum operating voltage of the auxiliary machine is acquired, and the measured value of the first voltage sensor (before precharging) Voltage)
The controller adjusts the output of the boost converter so that the measured value of the first voltage sensor does not fall below a value obtained by subtracting the minimum value of the voltage difference from the pre-charge voltage during the precharge. A vehicle power supply system.

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