JP5076918B2 - Power storage device - Google Patents

Description

  The present invention relates to a power storage device that stores power in a power storage unit and discharges it when necessary.

  In recent years, automobiles (hereinafter referred to as vehicles) equipped with a regenerative system that collects braking energy as electric energy by generating electric power during braking have been developed in order to consider the environment and improve fuel efficiency. This regenerative system can reduce the amount of power generation other than during deceleration by charging the power generated by the generator when the vehicle is decelerating, thereby reducing the load on the engine and saving fuel.

  When such a regenerative system is applied to a conventional vehicle, the generated power at the time of deceleration is charged to the lead battery, but in the case of sudden deceleration, a large amount of power is generated in a short time, and rapid charging is insufficient The lead battery could not be charged efficiently.

  Therefore, in order to efficiently recover a large amount of power for a short time, a power control device for a vehicle regeneration system using a capacitor having excellent rapid charge / discharge characteristics as a preliminary power storage means has been proposed in, for example, Patent Document 1 below. Yes. FIG. 3 is a block circuit diagram of such a power control apparatus.

  The main power source 101 is a lead battery, and a load 105 is connected to the positive electrode via an ignition switch 103. A vehicle generator 107 is connected to the positive electrode of the main power supply 101. Since the generator 107 is mechanically connected to the engine 109, the generator 107 is driven by the operation of the engine 109. Further, the tire 109 is mechanically connected to the engine 109, and the tire 111 is rotated by the driving force of the engine 109 to drive the vehicle. Further, at the time of deceleration due to braking, the tire 111 rotates due to the inertia of the vehicle, whereby the engine 109 also rotates. The generator 107 is driven by this rotational energy, and power is generated by braking energy. The generator 107 performs constant voltage control (feedback control) of the output voltage, which is a general function.

  To such a vehicle, the power storage means 115 is connected to the generator 107 via the DC / DC converter 113 in order to efficiently recover the electric power generated by the braking energy. Since a large-capacity electric double layer capacitor is used for the power storage means 115, it is possible to efficiently recover a large amount of short-time power generated during sudden deceleration or the like. The DC / DC converter 113 is connected to an arithmetic device 117 for controlling its operation. Further, the arithmetic device 117 is provided with a signal receiving terminal 119 for receiving various signals from the vehicle side. Accordingly, the arithmetic unit 117 receives the vehicle running state, the engine 109 operating state, the voltage state of the main power supply 101, and the like from the signal receiving terminal 119, thereby controlling charging / discharging of the power storage means 115 according to those states. Is performed on the DC / DC converter 113.

By using the power control apparatus for a regenerative system with such a configuration, the power during deceleration including large power generated in a short time is once charged in the power storage means 115, and the power charged during times other than during deceleration is the main power. It can be supplied to the power source 101 and the load 105. As a result, efficient regeneration of braking energy is possible.
Japanese Patent No. 3465293

  According to the power control device described above, it is possible to reduce the fuel consumption of the vehicle through efficient regeneration. However, after regeneration, charging from the generator 107 to the power storage means 115 is completed, and the DC / DC converter 113 is turned on. When stopping, there were the following problems.

  FIGS. 4A and 4B are voltage-current characteristics over time when charging is completed from the state where the power storage unit 115 is charged, FIG. 4A is a time-dependent characteristic diagram with respect to the applied voltage of the load 105, and FIG. The time-dependent characteristic figure in the electric current to is shown, respectively.

  From time t0 to t1, while the regenerative power of the generator 107 is being charged into the power storage means 115 by the DC / DC converter 113, the output voltage of the generator 107 is a constant value Vb (for example, as shown in FIG. 4A). 14V). Thereby, since the constant voltage Vb is supplied to the load 105, it can operate | move stably.

  On the other hand, the power storage means 115 is charged with regenerative power from the generator 107. Here, the DC / DC converter 113 performs general constant current charging when charging the electric double layer capacitor. Therefore, the current Ic flowing through the power storage means 115 is constant as shown in FIG.

  Thereafter, when regeneration ends at time t1, the arithmetic unit 117 receives the information from the signal reception terminal 119. As a result, the arithmetic unit 117 controls the operation of the DC / DC converter 113 to stop. As a result, as shown in FIG. 4B, the current Ic flowing through the power storage means 115 immediately becomes 0A, and the charging ends. At this time, as shown in FIG. 4A, the voltage of the main power supply 101 rises once and then fluctuates back to the original voltage. This is caused by the power stored in the wiring inductance of the power control device in FIG. 3 or the filter capacitor or filter inductor built in the filter circuit not shown in FIG. 3 but generally used as a noise countermeasure. This is because the wiring system power stored in the wiring system other than the power storage means 115 due to the stored power is discharged when the DC / DC converter 113 is stopped. That is, since the DC / DC converter 113 is stopped, the wiring system power is discharged to the main power supply 101 side, and voltage fluctuation occurs temporarily. As a result, a voltage higher than the rated voltage is applied to the load 105, and there is a problem that the operation may become unstable.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a power storage device that can reduce voltage fluctuation to a load when charging of a power storage unit is stopped.

  In order to solve the conventional problem, a power storage device according to the present invention includes a DC / DC converter including an input / output terminal and a power storage unit terminal, and a power storage unit connected to the power storage unit terminal. When stopping the operation of the DC converter, the DC / DC converter reduces the charging current (Ic) to the power storage unit over time while keeping the voltage (Vb) of the input / output terminal constant. It is intended to stop.

  According to the power storage device of the present invention, the DC / DC converter reduces the charging current (Ic) to the power storage unit over time while keeping the input / output terminals at a constant voltage. The operation of discharging to the power storage unit is performed. After that, since the DC / DC converter is stopped, the wiring system power is not discharged to the main power source connected to the input / output terminals, and an effect of realizing a power storage device that can reduce voltage fluctuation to the load can be realized. Is obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a block circuit diagram of a power storage device according to an embodiment of the present invention. FIG. 2 is a time-dependent change diagram of the voltage and current of the power storage device according to the embodiment of the present invention. FIG. 2A is a time-dependent change diagram of the voltage at the input / output terminal, and FIG. (C) is a timing chart of the first switch, and (d) is a timing chart of the second switch. In FIG. 1, thick lines indicate power system wirings, and thin lines indicate signal system wirings.

  In FIG. 1, the power storage device 11 is connected to a main power supply 15, a load 17, and a generator 19 via a filter circuit 13 for noise reduction. The filter circuit 13 comprises two filter capacitors 21 connected between the ground and a filter inductor 23 connected between them, and constitutes a π-type filter circuit 13 as shown in FIG. ing. The main power source 15 is a vehicle battery having a rated voltage of 12 V, and the load 17 is various electrical components mounted on the automobile. The generator 19 is an alternator for a vehicle and is mechanically connected to the engine and driven by the power of the engine. At the time of braking, the generator 19 converts kinetic energy of the vehicle into electric energy to generate regenerative power. The generator 19 itself is configured to perform feedback control so that the generated voltage at this time is constant (for example, 14 V). A wiring inductance 25 is formed in the wiring system from the power storage device 11 to the filter circuit 13, the main power supply 15, the load 17, and the generator 19. In FIG. 1, a wiring inductance 25 is shown between the filter circuit 13 and the main power supply 15 as a representative in the wiring system.

  The power storage device 11 has the following configuration. The power storage device 11 includes a DC / DC converter 31 including an input / output terminal 27 and a power storage unit terminal 29, and a power storage unit 33 connected to the power storage unit terminal 29. The input / output terminal 27 is a terminal for charging / discharging power to / from the power storage unit 33, and the main power supply 15, the load 17, and the generator 19 are connected via the filter circuit 13.

  Here, the power storage unit 33 has a configuration in which a plurality of electric double layer capacitors excellent in rapid charge / discharge characteristics are connected in series. The power storage unit 33 has a capacity capable of storing power larger than the sum of the regenerative power generated by one regeneration and the wiring system power stored in the wiring system (such as the filter circuit 13 and the wiring inductance 25) excluding the power storage unit 33. It was. As a result, the power storage unit 33 can be charged with as much regenerative power as possible, and the power storage unit 33 can sufficiently absorb the wiring system power that has been stored so far when the DC / DC converter 31 is controlled to be described later. It becomes. As a result, it is possible to contribute to voltage stabilization of the main power supply 15. The power storage unit 33 may be configured to increase or decrease the number of electric double layer capacitors or connect in series and parallel according to the power specifications required for the power storage device 11 and the like.

  Next, the detailed configuration of the DC / DC converter 31 will be described. An input / output terminal voltage detection circuit 35 is connected to the input / output terminal 27 of the DC / DC converter 31. This has a function of detecting and outputting the voltage of the input / output terminal 27 (corresponding to the voltage Vb of the main power supply 15). Specifically, two serial connections are made between the input / output terminal 27 and the ground. The resistor is provided. Therefore, the midpoint voltage can be detected as a voltage proportional to the voltage Vb of the main power supply 15.

  Further, one end of an inductor 37 is connected to the input / output terminal 27. One end of the first switch 39 and one end of the second switch 41 are connected to the other end of the inductor 37, respectively. Since the other end of the first switch 39 is connected to the ground, and the other end of the second switch 41 is connected to the power storage unit 33 via the power storage unit terminal 29, the first switch 39 and the second switch 41 are alternately controlled on and off. By doing so, the power storage unit 33 can be charged and discharged. Therefore, the first switch 39 and the second switch 41 need to be configured so as to be capable of on / off control from the outside. In this embodiment, an FET is used.

  A power storage unit voltage detection circuit 43 is connected to the power storage unit terminal 29. This has the same configuration as the input / output terminal voltage detection circuit 35, and detects and outputs a voltage proportional to the voltage Vc of the power storage unit 33. Further, a smoothing capacitor 45 is also connected to the power storage unit terminal 29.

  The input / output terminal voltage detection circuit 35, the first switch 39, the second switch 41, and the power storage unit voltage detection circuit 43 are connected to the control circuit 47 by signal system wiring. The control circuit 47 includes a microcomputer and peripheral circuits, and controls the overall operation of the DC / DC converter 47. That is, the control circuit 47 reads the voltage Vb of the input / output terminal 27 from the output of the input / output terminal voltage detection circuit 35 and reads the voltage Vc of the power storage unit 33 from the output of the power storage unit voltage detection circuit 43. Further, the control circuit 47 transmits a first switch control signal SW1 and a second switch control signal SW2 for ON / OFF control of the first switch 39 and the second switch 41, respectively. Furthermore, the control circuit 47 has a function of communicating with each other by performing transmission / reception of a data signal data with a vehicle-side control circuit (not shown).

  Next, a specific operation when the power storage device 11 is stopped will be described with reference to FIG.

  First, during time t0 to t1, the DC / DC converter 31 operates so that the regenerative power from the generator 19 generated by braking the vehicle is charged to the power storage unit 33 with a constant current. The output voltage of the generator 19 at this time is a constant value Vb (14 V) as shown in FIG. Thereby, since the constant voltage Vb is supplied to the load 17, it can operate | move stably.

  On the other hand, as described above, since the regenerative power from the generator 19 is charged to the power storage unit 33 with a constant current, the current Ic flowing through the power storage unit 33 is constant as shown in FIG.

  As shown in the timing charts of FIGS. 2 (c) and 2 (d), the first switch 39 and the second switch 41 are alternately turned on and off during normal current charging of the power storage unit 33 as described above. The control circuit 47 controls to repeat the above. In addition, in the time t0 to t1 of FIG. 2C and FIG.

  Thereafter, when regeneration ends at time t1, the control circuit 47 receives a regeneration stop signal issued from outside (here, the vehicle-side control circuit) as the data signal data. Thereby, the control circuit 47 stops the operation of the DC / DC converter 31 as follows.

  First, the control circuit 47 performs constant voltage control from constant current control so that the voltage Vb of the input / output terminal 27 becomes constant. The target constant voltage value at this time is the voltage value of the input / output terminal 27 immediately before receiving the regeneration stop signal. The control circuit 47 detects and stores the voltage Vb of the input / output terminal 27 by the input / output terminal voltage detection circuit 35 at regular intervals. Therefore, the voltage value of the input / output terminal 27 immediately before receiving the regeneration stop signal is known. The control circuit 47 reads the output of the input / output terminal voltage detection circuit 35 as the voltage Vb so that the voltage Vb of the input / output terminal 27 becomes the constant target constant voltage value obtained as described above, and performs feedback control. . At the same time, the control circuit 47 performs control so as to reduce the charging current Ic to the power storage unit 33 over time. Specifically, as shown in FIGS. 2C and 2D, the on-time of the first switch 39 is gradually shortened and the on-time of the second switch 41 is gradually lengthened from the time t1 to the time t2. Control to be. As a result, as shown in FIG. 2 (a), the voltage Vb at the input / output terminal 27 remains constant after time t1, and as shown in FIG. 2 (b), the charging current Ic to the power storage unit 33 changes with time. Will be reduced. As a result, the wiring system power stored in the filter circuit 13, the wiring inductance 25, and the like is charged into the power storage unit 33 by the DC / DC converter 31.

  Eventually, when the time t2 is reached, the charging of the power storage unit 33 with the wiring system power is completed. At this time, as shown in FIGS. 2C and 2D, the control circuit 47 stops the operation of the first switch 39 and the second switch 41 and turns off both. As a result, as shown in FIG. 2B, the current Ic to the power storage unit 33 becomes 0 A, and the operation of the DC / DC converter 31 is stopped. At this time, since regeneration has been completed, the generator 19 is driven by the engine and continues to generate power at the constant voltage Vb.

  From these facts, as shown in FIG. 2A, it can be seen that the voltage Vb at the input / output terminal 27 is always constant from the time t0 to the time t2 and thereafter, and no voltage fluctuation occurs. As a result, the load 17 is either regenerated (from time t0 to t1), charged to the power storage unit 33 of wiring system power (from time t1 to t2), or when the DC / DC converter 31 is stopped (after time t2). Since a constant voltage is also supplied at, the possibility that the load 17 performs an unstable operation is reduced.

  When regenerative power is generated again while the regenerative power stored in the power storage unit 33 is discharged and supplied to the main power supply 15 or the load 17 except during regeneration, the power remains in the power storage unit 33. Since regenerative power is charged, if the charging is continued as it is, the withstand voltage of the power storage unit 33 is exceeded, and the deterioration of the power storage unit 33 is promoted.

  In order to avoid this, in the present embodiment, the DC / DC converter 31 not only stops its operation by receiving a regeneration stop signal emitted from the outside, but also the power storage unit detected by the power storage unit voltage detection circuit 43. If the voltage at the terminal 29 (corresponding to the voltage Vc of the power storage unit 33) reaches a predetermined voltage, the operation is stopped. The stop operation of the DC / DC converter 31 at this time is the same as the stop operation by receiving the regeneration stop signal. Therefore, the power storage device 11 of the present embodiment is controlled to stop the DC / DC converter 31 when either the reception of the regeneration stop signal or the arrival of the voltage Vc of the power storage unit terminal 29 at the predetermined voltage occurs. doing.

  Here, the predetermined voltage is set to be smaller than a value obtained by subtracting the voltage increase when the power storage unit 33 charges the wiring system power stored in the wiring system excluding the power storage unit 33 from the full charge voltage of the power storage unit 33. Has been decided. Thereby, when the voltage Vc of the power storage unit 33 reaches a predetermined voltage and the DC / DC converter 31 is stopped, even if the power storage unit 33 charges the wiring system power and the voltage Vc of the power storage unit 33 increases, the predetermined value is maintained. Since the voltage subtracts the voltage increase from the full charge voltage, the voltage Vc does not exceed the full charge voltage when the DC / DC converter 31 is stopped. Therefore, deterioration of the power storage unit 33 can be reduced, and high reliability can be obtained.

  With the above configuration and operation, the DC / DC converter 31 reduces the charging current Ic to the power storage unit 33 over time while keeping the input / output terminal 27 at a constant voltage. 33 is discharged, and then the DC / DC converter 31 is stopped. Therefore, the wiring system power is not discharged to the main power supply 15 connected to the input / output terminal 27, and voltage fluctuation to the load 17 is prevented. The power storage device 11 that can be reduced can be realized.

  In the present embodiment, the electric storage unit 33 uses an electric double layer capacitor as an electric storage element, but may be another capacitor such as an electrochemical capacitor.

  Further, in the present embodiment, the case where the power storage device 11 is used for recovering the regenerative electric power of the vehicle has been described. It may be used as an auxiliary power source for driving a system starter motor, an electric turbo motor, etc.) or as a backup power source for an electronically controlled brake system or the like.

  Moreover, in this Embodiment, although the case where the electrical storage apparatus 11 was applied to the vehicle was described, it is not restricted to them, For example, to the emergency power supply apparatus etc. which supply electric power to a load at the time of a power failure of system power supply (AC power supply etc.) Is also applicable. In this case, when the system power supply is normal, the voltage fluctuation of the system power supply can be reduced when the DC / DC converter 31 is stopped after charging the power storage unit 33 from the system power supply, and is connected to the system power supply. The possibility that the operation of a large number of loads becomes unstable can be reduced.

  The power storage device according to the present invention can reduce voltage fluctuations to the load when charging of the power storage unit is stopped, and thus is particularly useful as a power storage device for recovering regenerative power during vehicle braking.

1 is a block circuit diagram of a power storage device in an embodiment of the present invention. FIG. 4 is a time-dependent change diagram of voltage and current of the power storage device according to the embodiment of the present invention, in which (a) is a time-dependent change diagram in the voltage at the input / output terminal, (b) is a time-dependent change diagram in current to the power storage unit, and (c) is Timing chart of the first switch, (d) is the timing chart of the second switch Block diagram of a conventional power control device It is a voltage current aging characteristic figure of the conventional power control device, (a) is a aging characteristic figure in the applied voltage of a load, (b) is a chronological characteristic figure in the current to an electrical storage means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Power storage device 27 Input / output terminal 29 Power storage unit terminal 31 DC / DC converter 33 Power storage unit

Claims (6)

A DC / DC converter having an input / output terminal and a power storage unit terminal;
The power storage unit connected to the power storage unit terminal,
When stopping the operation of the DC / DC converter, the DC / DC converter changes the charging current (Ic) to the power storage unit over time while keeping the voltage (Vb) of the input / output terminal constant. A power storage device that stops after being reduced. The power storage device according to claim 1, wherein the power storage unit includes a capacitor. The power storage device according to claim 1, wherein the DC / DC converter stops operation by receiving a regeneration stop signal emitted from the outside. The power storage device according to claim 3, wherein the power storage unit has a capacity capable of storing power larger than a sum of regenerative power generated by one regeneration and wiring system power stored in a wiring system excluding the power storage unit. The power storage device according to claim 1, wherein the DC / DC converter stops operating when a voltage (Vc) of the power storage unit terminal reaches a predetermined voltage. The predetermined voltage is less than a value obtained by subtracting a voltage increase when the power storage unit is charged from a full charge voltage of the power storage unit, and a wiring system power stored in a wiring system excluding the power storage unit. The power storage device described.

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