JP2010140833A - Power storage device - Google Patents

Abstract

In overdischarge protection of each cell in which unit cells of a secondary battery and a capacitor are connected in series, the method of monitoring the voltage of each cell is different in potential, so that it can be directly connected to a control circuit of a charging / discharging device. Can not.
As an overdischarge protection device for a power storage device that balances the voltage of each cell of an assembled battery connected in series using a transformer having a plurality of secondary windings, the current of the transformer primary winding Is detected to determine the overdischarge state.
[Selection] Figure 1

Description

  The present invention relates to an overdischarge protection method for a battery pack configured by connecting a plurality of cells such as a secondary battery and a large capacity capacitor in series.

In recent years, the application of secondary batteries, large-capacity capacitors, and the like has been expanded with the demand for stabilization of power supply systems such as power storage devices, power fluctuation suppression devices, and uninterruptible power supply devices.
Secondary batteries and capacitors have a unit cell rated voltage as low as several volts, so when applied to the power supply stabilization system, it is common to use a battery pack consisting of multiple cells connected in series. Is. Since charge / discharge control as a system is performed at the battery connection end of the charge / discharge device, voltage imbalance caused by differences in unit cell characteristics and operation limit monitoring of each cell voltage (upper / lower limit voltage) are separately provided. Is required.

Hybrid type capacitors, which are one of secondary batteries and large-capacity capacitors, have upper and lower limit values for charge / discharge voltage. The deviation from the limit voltage not only greatly affects the life but also causes a failure. Therefore, the charge / discharge device performs the charge / discharge operation within the limit range.
FIG. 10 shows a protection circuit configuration of an assembled battery using a conventional technique. The content described in Patent Document 1 is a configuration in which a flyback type DC-DC converter is used as a voltage balance circuit of a unit battery.

An electromotive force of an assembled battery BA in which a plurality of secondary batteries (unit batteries) B1 to B3 are connected in series is transferred to the secondary batteries B1 to B3 using a transformer 31 having a plurality of secondary windings L21 to L23. A cell balance circuit unit 30 for equalizing the electromotive force between the secondary batteries by redistribution; a switch circuit 50 for controlling the energization according to the current direction by interposing in series with the charge / discharge path of the battery pack BA; When there is an overcharge / overdischarge detection means 40 for detecting whether any secondary battery in the assembled battery BA is overcharged or overdischarged, and when the detection means 40 detects overcharge When the charging path (switch S1) is cut off, and when the detection means 40 detects overdischarge, the discharge path (switch S2) is cut off, and when the detection means 40 detects either overdischarge or overcharge Above Operating the balancing circuit portion 30.

In addition to the above, there is the following patent document as a circuit for monitoring and protecting the cell voltage.
Patent Document 2 proposes to monitor the voltage of individual cells connected in series and to detect the full charge by comparing with the reference voltage created by the resistance voltage division of the assembled battery, and to cut off the charging path. ing.

  Patent Document 3 is to detect individual cell voltages of an assembled battery and convert the detection result to the same potential by a level shift circuit, thereby reducing the determination circuit required for the function shown in Patent Document 2. is suggesting.

Patent Document 4 proposes a cell voltage balance circuit and a protection circuit. As a reference voltage setting means for balance circuit operation, we have proposed a level shift circuit with an insulation amplifier, and as a protection circuit against overcharge and overdischarge, by isolating the determination signal of each cell with a photocoupler, A charge / discharge operation circuit having a different potential is operated.
JP 2004-88878 A JP-A-8-78060 JP 2004-134372 A JP 2006-20382 A

  Each prior art document shown in the prior art individually monitors the voltage of a plurality of cells connected in series, and stops or suppresses charging / discharging of an assembled battery (or assembled battery) when overcharging or overdischarging occurs Is proposed.

  However, since the potentials of the cells connected in series are different, they cannot be directly connected to the control circuit of the charge / discharge device. In order to capture the voltage of each cell connected in series to the control circuit, it is necessary to take measures such as using an insulating means or a level shift circuit. Conventionally, a protection circuit is provided for each cell as in Patent Document 2, or a common protection circuit is operated by providing a level shift circuit or an insulation circuit as in Patent Document 3 and Patent Document 4, This method also made the protection circuit complicated. The present proposal particularly proposes an overdischarge detection means and an overdischarge protection system using the detection means for solving the above-described problems with respect to overdischarge.

  In order to solve the above-described problem, in the first invention, an assembled battery configured by connecting a plurality of unit cells of a secondary battery or a capacitor in series, and charging / discharging the charged battery to a predetermined voltage A power storage device comprising: a transformer having a plurality of secondary windings; a reference DC voltage source; a switching element that excites the primary winding of the transformer with the reference DC voltage source; A forward type DC / DC converter including a series circuit of a secondary winding and a diode of the transformer connected in parallel to a unit cell of the assembled battery, and a current of the primary winding of the transformer is detected. Current detection means and current determination means for comparing the detection result of the current detection means with a predetermined value, and determining from the output of the current determination means that the unit cell of the assembled battery is in an overdischarged state.

  In a second invention, in a power storage device comprising: an assembled battery configured by connecting a plurality of unit cells of a secondary battery or a capacitor in series; and a charging / discharging device that charges and discharges the assembled battery to a predetermined voltage. A transformer having a plurality of secondary windings, a reference DC voltage source, a switch element for exciting the primary winding of the transformer with the reference DC voltage source, and a series of two unit cells of the assembled battery A forward DC / DC converter comprising a series circuit of a secondary winding with an intermediate tap of the transformer and a diode connected in parallel with a circuit; and a current for detecting a current of the primary winding of the transformer Detecting means and current determining means for comparing the detection result of the current detecting means with a predetermined value, and determining from the output of the current determining means that the unit cell of the assembled battery is in an overdischarged state.

  In a third invention, in a power storage device comprising: an assembled battery configured by connecting a plurality of unit cells of a secondary battery or a capacitor in series; and a charging / discharging device that charges and discharges the assembled battery to a predetermined voltage. A transformer having a plurality of secondary windings, a reference DC voltage source, a switch element for exciting the primary winding of the transformer with the reference DC voltage source, and a series of two unit cells of the assembled battery A series circuit of a secondary winding with an intermediate tap of the transformer and a diode connected in parallel with a circuit, and a secondary winding and a diode of the transformer with an intermediate tap connected in parallel with a unit cell of the assembled battery; A forward DC / DC converter comprising: a current detection means for detecting a current of a primary winding of the transformer; and a current determination for comparing the detection result of the current detection means with a predetermined value. Means. It determines with the unit cell of the said assembled battery being an overdischarge state from the output of a flow determination means.

  In a fourth invention, in the first to third inventions, the discharge operation is stopped when it is determined from the output of the current determination means that the unit cell of the assembled battery is in an overdischarge state.

  In a fifth invention, in the first to third inventions, the reference DC voltage source is made from an assembled battery voltage formed by connecting a plurality of the unit cells in series using an insulated DC-DC converter circuit. .

  In a sixth aspect of the invention, an assembled battery configured by connecting a plurality of unit cells of a secondary battery or a capacitor in series, a transformer having a plurality of secondary windings, and a parallel connection with the unit cell of the assembled battery In a power storage device comprising a plurality of assembled battery units comprising a secondary circuit of the transformer and a series circuit of diodes, the outputs of the assembled battery units are connected in parallel via the shut-off means, In addition, the transformer primary winding of each assembled battery unit is connected in parallel via the current detection means and is excited by the reference DC voltage source and the switching element, and connected to the charging / discharging device. It is determined that the unit cell of the assembled battery is in an overdischarged state from the output of the current determination means for comparing the detection result of the means with a predetermined value.

  In a seventh invention, in the sixth invention, when it is determined from the output of the current determination means that the unit cell of the assembled battery is in an overdischarged state, the discharge operation of the corresponding assembled battery unit is stopped. .

  In an eighth aspect based on the sixth aspect, the reference DC voltage source is made by using a DC-DC conversion circuit from the point of being connected in parallel via the output blocking means of each assembled battery unit.

  In the present invention, a transformer having a plurality of secondary windings, a reference DC voltage source, a switching element for exciting the primary winding of the transformer with the reference DC voltage source, and a unit cell of the assembled battery, A forward DC / DC converter comprising a series circuit of a secondary winding and a diode of the transformer connected in parallel; a current detection means for detecting a current of the primary winding of the transformer; Current determination means for comparing the detection result of the current detection means with a predetermined value, and since it is determined that the assembled battery cell is in an overdischarge state from the output of the current determination means, There is no need to monitor the voltage of the unit cell.

  In addition, the overdischarge status of each cell can be detected with one circuit regardless of the number of cells, and each cell of the assembled battery and the discharge detection circuit are insulated in advance, so that the detection signal is protected without using an insulating means. Can be directly connected to different potentials such as circuits.

As a result, it is possible to detect and protect the overdischarge of the assembled battery simply by monitoring the current of the transformer primary winding, and the protection circuit can be simplified even when the number of unit cells in series is large. Become.
It is also possible to determine in which assembled battery an overdischarge has occurred when a plurality of assembled batteries in which unit cells are connected in series are connected in parallel.

  The gist of the present invention is that a transformer primary winding is used as an overdischarge protection device for a power storage device that balances the voltage of each cell of an assembled battery connected in series using a transformer having a plurality of secondary windings. The overcurrent state is determined by detecting this current.

FIG. 1 shows a first embodiment of the present invention. This is a configuration in which a capacitor module 5 in which four capacitors C1 to C4 are connected in series is used as an assembled battery.
The circuit shown in the embodiment includes a reference DC voltage source 1 having a different potential from the capacitors C1 to C4, a switch element 2 such as a MOSFET, and the same number of secondary cells as the number of series cells of the capacitor whose secondary winding is a protection target. Transformer 3 having windings W21 to W24, secondary current rectifying diodes D1 to D4, detection resistor 8 for converting the current of the primary winding into a voltage signal, and detection converted by the detection resistor 8 The comparator 10 compares the signal with a predetermined level.

Next, the circuit operation of the embodiment will be described.
First, the switch element 2 is turned on / off according to the overdischarge protection monitoring timing, and the output voltage V1 of the reference DC voltage source 1 is applied to the primary winding W1 of the transformer 3. When the switch element 2 is turned on, a combined current (hereinafter, primary current) of the excitation current of the primary winding W1 and the primary conversion current of the secondary winding current flows to the primary winding. The primary current I1 is converted by the detection resistor 8 into a primary winding current detection signal V (I1) having the same potential as the reference DC voltage source 1. The comparator 10 determines that this detection signal has reached a level exceeding the exciting current of the primary winding.
Here, FIG. 2 shows a primary winding current waveform when the turn ratio of the transformer 3 is set so that the secondary winding voltage becomes the cell lower limit voltage Vx of the capacitor.

  FIG. 2 (a) shows the primary current waveform when the voltages of the cells C1 to C4 constituting the capacitor module 5 all exceed Vx. Since the current from each cell is blocked by the rectifying diodes D1 to D4, the secondary winding current becomes zero, and only the transformer exciting current ILm flows through the primary winding.

  FIG. 2B shows a primary current waveform when one cell (second cell C2) of the cells constituting the capacitor module 5 falls below the lower limit voltage Vx. When the cell falls below the secondary winding voltage Vx, a current for charging the cell flows through the secondary winding. As a result, a current obtained by adding the current converted to the turn ratio of the cell charging current indicated by diagonal lines to the exciting current of the transformer 3 flows as the primary current I1. Therefore, it is possible to determine that the capacitor module constituent cell is in an overdischarged state by detecting the primary current of the transformer 3 and detecting a conduction current equal to or higher than the exciting current of the transformer 3 by the comparator 10. It becomes possible. FIG. 3 is a circuit that cuts off the charge / discharge switch 11 of the capacitor module using the overdischarge determination signal shown in FIG.

  FIG. 4 shows a configuration when the reference DC voltage source in the circuit of FIG. 1 uses the capacitor module 5 as a power source. The voltage of the capacitor module 5 is input to the insulated power supply circuit 1a. The insulated power supply circuit 1a is constituted by a so-called insulation type DC-DC converter composed of a switching circuit, an insulation transformer, a rectifier diode, and the like, and this output can be used as the reference DC voltage source 1 of FIG.

  As described above, the secondary winding voltage of the transformer 3 is set to the lower limit voltage of the cell, the transformer 3 is excited at a predetermined monitoring timing, and only the primary current is monitored, so that a plurality of cells The overdischarge state can be collectively determined. Further, since the potential of the overdischarge detection circuit is the potential of the reference DC voltage source 1 insulated from the capacitor side potential by the transformer, the control circuit potential of the charge / discharge device and the drive circuit of the charge / discharge switch It becomes possible to connect directly to the potential. As a result, the complication of the protection circuit, which has been a problem in the past, can be solved.

5 and 6 show a second embodiment of the present invention.
The difference from the first embodiment is that the secondary winding of the transformer 3a is a winding with an intermediate tap. The intermediate tapped winding consisting of windings W21a and W22a is a series circuit of capacitors C1 and C2 via diodes D1a and D2a, and the intermediate tapping winding consisting of windings W23a and W24a is a capacitor via diodes D3a and D4a. Each is connected to a series circuit of C3 and C4.
Since the operation of the circuit is the same as that of the first embodiment, a description thereof will be omitted.
Even in a configuration in which a winding with an intermediate tap is used as a transformer and the number of terminals of the transformer is reduced, overdischarge protection can be realized by detecting the transformer primary current in the same manner.

FIG. 6 is a circuit that cuts off the charge / discharge switch 11 of the capacitor module using the overdischarge determination signal shown in FIG.
Also in this embodiment, it goes without saying that the insulated power supply circuit 1 a shown in FIG. 4 can be used as the reference DC voltage source 1.

7 and 8 show a third embodiment of the present invention.
The difference from the first embodiment and the second embodiment is that the configuration of the secondary winding of the transformer 3b includes the windings W21b, W22b with intermediate taps and the winding W23b without intermediate taps. A winding with an intermediate tap composed of windings W21b and W22b is connected in parallel to a series circuit of capacitors C1 and C2 via diodes D1b and D2b, and winding W23b is connected to a capacitor C3 via a diode D3b. Since the operation of the circuit relating to overdischarge protection is the same as in the first and second embodiments, the description thereof is omitted.
Similar to the second embodiment, the number of transformer terminals can be reduced with respect to the first embodiment. However, the second embodiment can be applied only to an even number of capacitors, whereas the second embodiment has a series number of capacitors. It can also be applied to an odd number.

FIG. 9 shows a fourth embodiment of the present invention.
Capacitor module 5b in which three capacitors C1a to C3a are connected in series, transformer 3c having three secondary windings W21c to W23c, and diodes D1c to D3c connected in series to each secondary winding of the transformer An assembled battery unit A composed of a series circuit of the capacitor, a capacitor module 5c in which three capacitors C1b to C3b are connected in series, a transformer 3d including three secondary windings W21d, W22d, and W23d, and a transformer The battery pack unit B including a series circuit of diodes D1d to D3d connected in series with each of the secondary windings is connected in parallel. The outputs of the assembled battery units A and B are connected in parallel via charge / discharge switches 11a and 11b, respectively, and further connected to the charge / discharge device 7. Moreover, the primary windings W1c and W1d of the transformers 3c and 3d of the assembled battery units A and B are connected in parallel via the current detectors 8a and 8b, and are excited by the reference DC voltage source 1 and the switch element 2. It is a configuration. Here, in the same way as the circuit shown in FIG. 4, the reference DC voltage source is an isolated DC-DC converter circuit from the point of being connected in parallel via the charging / discharging switches 11a and 11b of the respective assembled battery units A and B. Can be made using.

It can be detected from the output of the voltage comparators 10a and 10b that the detection results of the respective current detectors 8a and 8b are compared with the set values of the setting devices 9a and 9b to detect that the cell of the assembled battery unit is in an overdischarged state. When the current of the current detector 8a is larger than the set value, the charge / discharge switch 11a of the output of the assembled battery unit A is opened with the output signal of the comparator 10a, and when the current of the current detector 8b is larger than the set value, The overdischarge can be protected by opening the charge / discharge switch 11b of the output of the assembled battery unit B by the output signal of the comparator 10b. Furthermore, the output signals of the comparators 10a and 10b can be used to determine which assembled battery unit has undergone overdischarge. If the number of assembled battery units is large, maintainability is ensured by providing a display device, etc. Needless to say, this can be improved.
The case where there are two assembled battery units has been described above, but overdischarge can be detected and protected similarly when the number of parallel battery increases.
In addition, although the Example demonstrated the capacitor module, the same effect is acquired also in a secondary battery. Needless to say, a current detector such as a shunt resistor, a current transformer, or a hall CT can be used as a primary current detection method.

It is a circuit block diagram which shows the 1st Example of this invention. A waveform diagram showing the operation example of FIG. 1 and an explanatory diagram thereof are shown. FIG. 2 is a circuit diagram in which the configuration of FIG. 1 is extended to a protection circuit. The block diagram at the time of using an insulated power supply circuit as a reference DC voltage source is shown. It is a circuit block diagram which shows the 2nd Example of this invention. FIG. 6 is a circuit diagram in which the configuration of FIG. 5 is extended to a protection circuit. It is a circuit block diagram which shows the 3rd Example of this invention. FIG. 8 is a circuit diagram in which the configuration of FIG. 7 is extended to a protection circuit. It is a circuit block diagram which shows the 4th Example of this invention. The circuit block diagram which shows a prior art example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reference direct-current voltage source 1a ... Insulation power supply circuit 2, 36, S1, S2 ... Switch element A, B ... Assembly battery unit 3, 3a, 3b, 3c, 3d, 31 ... Transformer
5, 5a, 5b, 5c ... Capacitor modules D1-D4, D21-D23, D51, D52 ... Diodes D1a-D4a, D1b-D3b, D1c-D3c, D1d-D3d ... Diodes C1-C4, C1a to C3a, C1b to C3b ... capacitors (cells)
7, 20 ... Charge / discharge device 8 ... Resistance 8a, 8b ... Current detector 9, 9a, 9b ... Setting circuit 10, 10a, 10b ... Comparator BA ... Collective battery 11 , 11a, 11b ... charge / discharge switches B1-B3 ... secondary batteries (unit batteries) 30 ... cell balance circuit 40 ... overcharge / overdischarge detection means 50 ... switch circuit

Claims (8)

  A power storage device comprising: an assembled battery configured by connecting a plurality of unit cells of a secondary battery or a capacitor in series; and a charging / discharging device that charges and discharges the assembled battery to a predetermined voltage. A transformer comprising the transformer, a reference DC voltage source, a switch element that excites a primary winding of the transformer with the reference DC voltage source, and a secondary of the transformer connected in parallel with a unit cell of the assembled battery A forward type DC / DC converter comprising a series circuit of a winding and a diode; current detection means for detecting a current of a primary winding of the transformer; and a detection result of the current detection means as a predetermined value. And a current determination unit for comparing and determining, wherein the unit cell of the assembled battery is determined to be in an overdischarged state from an output of the current determination unit.   A power storage device comprising: an assembled battery configured by connecting a plurality of unit cells of a secondary battery or a capacitor in series; and a charging / discharging device that charges and discharges the assembled battery to a predetermined voltage. A transformer comprising a unit, a reference DC voltage source, a switching element that excites a primary winding of the transformer with the reference DC voltage source, and the unit cell series circuit of the assembled battery connected in parallel with the unit cell A forward DC / DC converter comprising a series circuit of a secondary winding with a middle tap of a transformer and a diode, current detection means for detecting a current of the primary winding of the transformer, and the current detection Current determination means for comparing the detection result of the means with a predetermined value, and determining from the output of the current determination means that the unit cell of the assembled battery is in an overdischarged state.   A power storage device comprising: an assembled battery configured by connecting a plurality of unit cells of a secondary battery or a capacitor in series; and a charging / discharging device that charges and discharges the assembled battery to a predetermined voltage. A transformer comprising a unit, a reference DC voltage source, a switching element for exciting a primary winding of the transformer with the reference DC voltage source, and the unit cell series circuit of the assembled battery connected in parallel with the unit cell A series circuit of a secondary winding with an intermediate tap of a transformer and a diode, and a series circuit of a secondary winding without an intermediate tap of the transformer and a diode connected in parallel to a unit cell of the assembled battery Forward type DC / DC converter, current detection means for detecting the current of the primary winding of the transformer, and current determination means for comparing the detection result of the current detection means with a predetermined value, Output of current judgment means And determining that the unit cell of the assembled battery is in an overdischarged state.   4. The power storage device according to claim 1, wherein when the unit cell of the assembled battery is determined to be in an overdischarge state from the output of the current determination unit, the discharge operation is stopped.   4. The power storage device according to claim 1, wherein the reference DC voltage source is made from an assembled battery voltage formed by connecting a plurality of the unit cells in series using an insulated DC-DC conversion circuit.   An assembled battery comprising a plurality of unit cells of secondary batteries and capacitors connected in series, a transformer having a plurality of secondary windings, and two transformers connected in parallel with the unit cells of the assembled battery. In a power storage device including a plurality of assembled battery units each including a series circuit of a secondary winding and a diode, the outputs of the assembled battery units are connected in parallel via a blocking means, and further connected to a charging / discharging device. In addition, the transformer primary winding of each assembled battery unit is connected in parallel via the current detection means, and is excited by the reference DC voltage source and the switching element, and the detection result of each current detection means is a predetermined value. And determining whether the unit cell of the assembled battery is in an overdischarged state from the output of the current determining means for comparing and determining.   7. The power storage device according to claim 6, wherein when the unit cell of the assembled battery is determined to be in an overdischarge state from the output of the current determination unit, the discharge operation of the corresponding assembled battery unit is stopped. .   The power storage device according to claim 6, wherein the reference DC voltage source is made by using an insulated DC-DC conversion circuit from the point where the outputs of the assembled battery units are connected in parallel through a cutoff means.

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