JP2011130534A - Power supply device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize an electric double-layer capacitor of a power supply device for a vehicle, which includes a secondary battery and the electric double-layer capacitor. <P>SOLUTION: The electric double-layer capacitor includes the secondary battery 10 which feeds power to a load 1 mounted to a vehicle, the electric double-layer capacitor 20 connected to the secondary battery 10 in parallel therewith, a power converter 30 which is interposed between the secondary battery 10 and the electric double-layer capacitor 20, and switched in both directions so as to be chargeable and dischargeable between the secondary battery 10 and the electric double-layer capacitor 20, and a control unit 40 which outputs a charging/discharging switching command of the electric double-layer capacitor 20 to the power converter 30 on the basis of a load current of the load 1 and a capacitor current of the electric double-layer capacitor 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle power supply device that supplies power to a vehicle.

  In recent years, electric double layer capacitors have been used in combination with secondary batteries such as lead storage batteries and nickel metal hydride batteries as power supply devices for vehicles such as electric vehicles and hybrid vehicles. The secondary battery has the characteristic that the energy capacity is large but the energy density is low, whereas the electric double layer capacitor has the opposite characteristic that the energy density is small but the energy density is high.

  Patent Document 1 discloses a power storage device for a hybrid vehicle that includes an electric double layer capacitor and a secondary battery and is capable of charging and discharging between the electric double layer capacitor and the secondary battery. In this power storage device, electricity is supplied from an electric double layer capacitor to a load, and a secondary battery is used to charge the electric double layer capacitor.

Japanese Patent Laid-Open No. 2005-160154

  However, in a power storage device such as Patent Document 1, since power is directly supplied from an electric double layer capacitor to a load, a large number of electric double layer capacitor cells having a small energy capacity are connected in series to drive the load. Have gained. Therefore, the electric double layer capacitor may be increased in size in order to maintain a high voltage.

  Therefore, an object of the present invention is to reduce the size of an electric double layer capacitor of a vehicle power supply device including a secondary battery and an electric double layer capacitor.

  The present invention provides a secondary battery for supplying power to a load mounted on a vehicle, an electric double layer capacitor connected in parallel to the secondary battery, and between the secondary battery and the electric double layer capacitor. A power converter that is interposed and switches between the secondary battery and the electric double layer capacitor so as to be able to charge and discharge bidirectionally, and based on the load current of the load and the capacitor current of the electric double layer capacitor, And a control unit that outputs a switching command for charging and discharging the double layer capacitor to the power converter.

  According to the present invention, the electric double layer capacitor is connected via the power converter in parallel with the secondary battery that supplies current to the load. Since the terminal voltage of the electric double layer capacitor is boosted by the power converter and supplied to the load, there is no need to increase the voltage by connecting multiple terminals in series, and the electric double layer capacitor can be downsized.

  Since the secondary battery has a large energy capacity, a plurality of secondary batteries are not connected in series to obtain a desired voltage, and a high voltage of several hundred volts can be obtained independently. Therefore, it is suppressed that a secondary battery is connected in series and enlarged in order to obtain the voltage which can drive a load.

It is a lineblock diagram of the power supply device for vehicles concerning an embodiment of the invention. It is a block diagram of the control part in the power supply device for vehicles. It is a figure which shows the change of the charging / discharging electric current of the power supply device for vehicles.

  Below, the power supply device 100 for vehicles which concerns on embodiment of this invention is demonstrated, referring drawings.

  First, the configuration of the vehicle power supply device 100 will be described with reference to FIG.

  The vehicle power supply device 100 is a device that supplies power to a vehicle (not shown) such as an electric vehicle or a hybrid vehicle. The vehicle power supply device 100 needs to supply a high voltage and a large current in order to drive a vehicle drive motor (not shown).

  The vehicle power supply device 100 includes a secondary battery 10 that supplies power to a load 1, an electric double layer capacitor 20 that is connected in parallel to the secondary battery 10, and between the secondary battery 10 and the electric double layer capacitor 20. And a control unit 40 that controls the power converter 30.

  In this specification, the current generated by the load 1 and the current flowing through the load 1 are referred to as load current, the current generated by the secondary battery 10 and the current flowing through the secondary battery 10 are referred to as battery current, and the electric double layer capacitor 20 And the current flowing through the electric double layer capacitor 20 are referred to as capacitor current.

  The load 1 is an electrical equipment mounted on a vehicle such as a drive motor. When the load 1 is a driving motor, the driving voltage is about 200 V, for example, and the driving voltage is higher than other auxiliary devices mounted on the vehicle. The driving motor receives electric power to generate a driving force of the vehicle when the vehicle is accelerated or the like, and regenerates traveling energy to generate power as a generator when the vehicle is decelerated or the like. A load current sensor 2 for detecting the magnitude of the load current is connected to the load 1 in series.

  The secondary battery 10 is a rechargeable chemical battery. The voltage of the secondary battery 10 is adjusted to a voltage necessary for driving the load 1. When the load 1 is a driving motor, the voltage is adjusted to about 200V, for example. The secondary battery 10 has a characteristic that the energy capacity is large but the energy density is low as compared with the electric double layer capacitor 20. Therefore, the secondary battery 10 is superior to the electric double layer capacitor 20 in the ability to continue supplying a constant current for a long time.

  The terminal voltage of the secondary battery 10 is maintained at a substantially constant voltage with almost no change until the energy capacity becomes empty. The secondary battery 10 is a chemical battery that stores electricity using a chemical reaction, and is easily deteriorated when charging and discharging are performed at a high frequency.

  The electric double layer capacitor 20 is formed by stacking a plurality of capacitor cells in which electrolyte ions between two electrodes, an anode and a cathode, form an electric double layer and store electricity, and are connected in series. Thus, the voltage is adjusted to a desired voltage, and a plurality of them are connected in parallel to adjust to a desired energy capacity.

  The electric double layer capacitor 20 has a characteristic that the energy density is small but the energy density is high compared to the secondary battery 10. Therefore, the electric double layer capacitor 20 is superior to the secondary battery 10 in the ability to rapidly charge and discharge a large amount of current.

  The terminal voltage of the electric double layer capacitor 20 varies in proportion to the square root of the stored energy. The electric double layer capacitor 20 stores electricity as electrons, and hardly deteriorates even when charging and discharging are repeated. It is known that the life of the electric double layer capacitor 20 depends on the holding voltage. The higher the holding voltage, the shorter the life. The withstand voltage of each capacitor cell of the electric double layer capacitor 20 is about 3V. Therefore, in order for the electric double layer capacitor 20 to obtain a voltage of 200 V, it is necessary to connect several tens of capacitor cells in series.

  The electric double layer capacitor 20 includes a protection circuit (not shown) that stops charging when the terminal voltage becomes higher than the first voltage and stops discharging when the terminal voltage becomes lower than the second voltage.

  The first voltage is a high voltage when the electric double layer capacitor 20 is fully charged. By providing the protection circuit, the electric double layer capacitor 20 is further charged from the fully charged state to be prevented from being overcharged, and the life is prevented from being shortened due to overcharging.

  The second voltage is a low voltage at which the electric double layer capacitor 20 cannot supply power to the load 1. That is, the second voltage is set lower than the first voltage. By providing the protection circuit, all electric power is supplied from the secondary battery 10 to the load 1 when the energy capacity of the electric double layer capacitor 20 is empty.

  The electric double layer capacitor 20 is provided with a capacitor current sensor 21 for detecting a capacitor current in series.

  The power converter 30 is a bidirectional DC / DC converter that switches between the secondary battery 10 and the electric double layer capacitor 20 so as to be chargeable / dischargeable in both directions.

  When electric power is supplied from the electric double layer capacitor 20 to the load 1 and when the electric double layer capacitor 20 charges the secondary battery 10, the power converter 30 supplies electric power supplied from the electric double layer capacitor 20 to The voltage is boosted to a voltage equivalent to that of the secondary battery 10. As a result, even when the terminal voltage of the electric double layer capacitor 20 varies depending on the amount of stored energy, the electric double layer capacitor 20 is boosted to a certain voltage regardless of the terminal voltage of the electric double layer capacitor 20 to increase the load. 1 can be supplied.

  On the other hand, when the load 1 or the secondary battery 10 charges the electric double layer capacitor 20, the power converter 30 lowers the power supplied from the load 1 or the secondary battery 10 than the withstand voltage of the electric double layer capacitor 20. Step down to voltage. This prevents the electric double layer capacitor 20 from being charged until the withstand voltage is exceeded.

  In general, a large number of electric double layer capacitors 20 are connected in series and adjusted to a high voltage (for example, 200 V) terminal voltage. Since most of the electric energy stored in the electric double layer capacitor 20 is necessary to maintain a high voltage, only a part of the electric energy can be used to drive the load 1.

  On the other hand, in the vehicle power supply device 100, since the electric double layer capacitor 20 is connected in parallel to the secondary battery 10 via the power converter 30, the output voltage of the electric double layer capacitor 20 is the power converter 30. Boosted. Therefore, since it is not necessary to connect a plurality of cells of the electric double layer capacitor 20 in series and adjust the voltage to a high voltage, the electric double layer capacitor 20 can be downsized.

  Note that the secondary battery 10 is not connected in series in order to obtain a desired voltage, but can obtain a voltage of several hundred volts independently, so that the electric double layer capacitor 20 is downsized. As a result, the secondary battery 10 is prevented from being enlarged.

  Further, since the electric power supplied from the electric double layer capacitor 20 is boosted by the power converter 30, it can be used as it is even if the terminal voltage is lowered, and can be used until the energy capacity of the electric double layer capacitor 20 becomes empty. Therefore, loss due to leakage current can be reduced, and the life of the electric double layer capacitor 20 can be extended.

  Since the vehicle power supply device 100 is obtained by connecting the electric double layer capacitor 20 to the secondary battery 10 via the power converter 30, the secondary battery 10, which has been conventionally used, is used alone as the load 1. It can also be obtained by mounting the power converter 30 and the electric double layer capacitor 20 on a system for supplying electric power.

  Next, the configuration of the control unit 40 will be described with reference to FIG.

  The control unit 40 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and I / O interface (input / output interface). The RAM stores data in the processing of the CPU, the ROM stores a control program of the CPU in advance, and the I / O interface is used for input / output of information with the connected device. Control of the power supply device 100 for vehicles is implement | achieved by operating CPU, RAM, etc. according to the program stored in ROM.

  The control unit 40 outputs a charge / discharge switching command for the electric double layer capacitor 20 to the power converter 30 based on the load current and the capacitor current. The control unit 40 is a difference obtained by comparing the load current and the battery current command value with a low-pass filter 41 that derives a battery current command value that is a primary delay element of the load current and is a command value of the battery current. A comparison unit 42 that calculates a capacitor current command value that is a value and a current control unit 43 that outputs a switching command to the power converter 30 are provided.

  The low-pass filter 41 cuts a frequency having a frequency higher than a set frequency based on the load current detected by the load current sensor 2 and obtains an output of a first-order lag element with respect to a square-wave step input. . Therefore, when the load current changes to a square wave, the square wave input is dulled by the low-pass filter 41 to become a first-order lag element, and is output as a battery current command value.

  The low-pass filter 41 is controlled by software processing in the control unit 40, but it is also possible to perform the same control by providing a low-pass filter outside the control unit 40.

  The actual load current value detected by the load current sensor 2 and the battery current command value output from the low-pass filter 41 are input to the comparison unit 42. The comparison unit 42 subtracts the battery current command value from the load current to calculate a capacitor current command value that is the difference between them.

  The current control unit 43 receives the actual capacitor current detected by the capacitor current sensor 21 and the capacitor current command value output from the comparison unit 42. Current control unit 43 compares the actual capacitor current with the capacitor current command value calculated by comparison unit 42, and outputs a switching command to power converter 30 so that the actual capacitor current becomes the capacitor current command value. Depending on the switching command, the power converter 30 supplies power to the load 1 from the electric double layer capacitor 20, so that the load 1 charges the electric double layer capacitor 20, or the secondary battery 10 and the electric double layer capacitor 20 Switching to and from the two-way power.

  Here, since the battery current command value is a value for calculating the capacitor current command value, the battery current of the secondary battery 10 is not controlled based on the battery current command value. However, since the sum of the battery current and the capacitor current is the load current, the battery current is determined by the load current and the capacitor current. That is, if the capacitor current is controlled based on the load current, the battery current is also controlled at the same time. Therefore, when the power converter 30 is controlled so that the actual capacitor current of the electric double layer capacitor 20 becomes the capacitor current command value, the current of the secondary battery 10 becomes the battery current command value.

  Below, the effect | action of the power supply device 100 for vehicles is demonstrated, referring FIG.

  In FIG. 3, the horizontal axis represents time, the vertical axis represents the charge / discharge current, the load current change is indicated by a thin solid line, the battery current change is indicated by a thick solid line, and the capacitor current change is indicated by a broken line. Yes. In FIG. 3, the capacitor current and the battery current are schematically shown as straight lines.

  At time A in FIG. 3, a square-wave charging current is input from the load 1 as a load current. This is the case in an electric vehicle or a hybrid vehicle in which a regenerative brake works and the drive motor becomes a generator to generate electricity.

  Since the current value of the battery current charged in the secondary battery 10 is a primary delay element of the load current, it is zero at the start of charging, but becomes larger with the passage of time and eventually becomes equal to the load current. On the other hand, the current value of the capacitor current charged in the electric double layer capacitor 20 is adjusted to the difference obtained by subtracting the battery current from the load current by the control unit 40. As it gets larger, it becomes relatively smaller and eventually becomes zero. That is, the electric double layer capacitor 20 having a high energy density and capable of charging / discharging with a large current is rapidly charged, and the secondary battery 10 having a large energy capacity is slowly charged.

  Here, the electric double layer capacitor 20 has a characteristic that the internal resistance is small. Therefore, the energy recovery rate can be improved by rapidly charging the electric double layer capacitor 20 with a large amount of power simultaneously with the start of charging.

  At time B in FIG. 3, the square-wave load current becomes zero, and the load 1 does not charge the electric double layer capacitor 20 and the secondary battery 10.

  Since the current value of the battery current is a first-order lag element of the load current, it does not become zero at the same time as the load current becomes zero, but gradually becomes smaller and eventually becomes zero. At this time, since the load 1 does not generate a charging current, the electric double layer capacitor 20 supplies power to the secondary battery 10 via the power converter 30 after the load current becomes zero, and the secondary battery 10 is charging.

  At time C in FIG. 3, a square wave current is output to the load 1. This is a case where the drive motor is driven in an electric vehicle or a hybrid vehicle.

  Since the current value of the battery current discharged from the secondary battery 10 is a primary delay element of the load current, it is zero at the start of discharge, but becomes larger with the passage of time and eventually becomes equal to the load current. On the other hand, the current value of the capacitor current discharged from the electric double layer capacitor 20 is adjusted to the difference obtained by subtracting the battery current from the load current by the control unit 40. As it gets larger, it becomes relatively smaller and eventually becomes zero. That is, the electric double layer capacitor 20 having a high energy density and capable of charging / discharging a large current is rapidly discharged, and the secondary battery 10 having a large energy capacity is slowly discharged.

  At time D in FIG. 3, the square-wave load current becomes zero, and the electric double layer capacitor 20 and the secondary battery 10 are not discharged to the load 1.

  Since the current value of the battery current is a first-order lag element of the load current, it does not become zero at the same time as the load current becomes zero, but gradually becomes smaller and eventually becomes zero. Since the load 1 does not consume power, the secondary battery 10 supplies power to the electric double layer capacitor 20 via the power converter 30 and charges the electric double layer capacitor 20 after the load current becomes zero. is doing.

  As described above, the electric double layer capacitor 20 bears the transient power at both the charging time when the load 1 generates power and the discharging time when the load 1 consumes electric energy, and the secondary power is supplied as the secondary power. The battery 10 bears. The electric double layer capacitor 20 is excellent in the performance of rapid charge and discharge with a large current, and the secondary battery 10 has a characteristic that the electric capacity is large. Therefore, in the vehicle power supply device 100, the characteristics of the electric double layer capacitor 20 and the secondary battery 10 are utilized.

  Moreover, since the charging / discharging current of the secondary battery 10 changes gradually, the energy throughput of the secondary battery 10 can be suppressed and the life of the secondary battery 10 can be extended.

  According to the above embodiment, the following effects are produced.

  In vehicle power supply device 100, electric double layer capacitor 20 is connected via power converter 30 in parallel with secondary battery 10 that supplies current to load 1. Since the terminal voltage of the electric double layer capacitor 20 is boosted by the power converter 30 and supplied to the load 1, it is not necessary to increase the voltage by connecting multiple terminals in series, and the electric double layer capacitor 20 can be downsized. It is.

  Note that the secondary battery 10 is not connected in series in order to obtain a desired voltage, but can obtain a voltage of several hundred volts independently, so that the electric double layer capacitor 20 is downsized. As a result, the secondary battery 10 is prevented from being enlarged.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The vehicle power supply device according to the present invention can be used as a power supply device for a vehicle such as an electric vehicle or a hybrid vehicle.

DESCRIPTION OF SYMBOLS 100 Vehicle power supply device 1 Load 10 Secondary battery 20 Electric double layer capacitor 30 Power converter 40 Control part 41 Low pass filter 42 Comparison part 43 Current control part

Claims (3)

A secondary battery for supplying power to a load mounted on the vehicle;
An electric double layer capacitor connected in parallel to the secondary battery;
A power converter that is interposed between the secondary battery and the electric double layer capacitor, and switches between the secondary battery and the electric double layer capacitor in a bidirectionally chargeable and dischargeable manner;
A vehicle power supply comprising: a control unit that outputs a switching command for charging and discharging the electric double layer capacitor to the power converter based on a load current of the load and a capacitor current of the electric double layer capacitor. apparatus. The controller is
A low-pass filter that is a primary delay element of the load current and derives a battery current command value that is a command value of the current of the secondary battery;
A comparator that subtracts the battery current command value from the load current to calculate a capacitor current command value that is a command value of the capacitor current;
The vehicle power supply device according to claim 1, further comprising: a current control unit that sends a switching command to the power converter based on the capacitor current and the capacitor current command value. The electric double layer capacitor includes a protection circuit that stops charging when it is higher than a first voltage and stops discharging when it is lower than a second voltage set lower than the first voltage. The vehicle power supply device according to claim 1 or 2.

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