JP3573274B2 - Power storage device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a power storage device that individually charges assembled batteries in which storage battery modules are connected in series, and has a configuration in which a flyback transformer and a rectifying element are provided in each of the storage battery modules, whereby variations in the charging voltage of each storage battery module are kept constant. It relates to a power storage device that limits the value.
[0002]
[Prior art]
As an energy source for an electric vehicle or a communication power supply device that requires a high voltage, an assembled battery in which a plurality of storage battery modules are connected in series is used. When a plurality of battery modules are connected in series and charged and discharged, the voltage of each battery module is irregularly distributed due to variations in battery characteristics, and overcharge or overdischarge of a specific battery module occurs. Therefore, when a storage battery module is used as an assembled battery, it is necessary to use a combination of storage battery modules with small variations in characteristics. In practice, the arrangement of each storage battery module deteriorates the heat radiation and raises the temperature, which affects the storage battery module characteristics and the degree of deterioration of the storage battery modules used for a long period of time is not uniform, so the storage battery module characteristics are made uniform. It is difficult. Therefore, in order to reduce the variation in the voltage of each storage battery module, equal charging (charging performed to eliminate the variation in the state of charge that has occurred in each storage battery module of the assembled battery) is required.
[0003]
As a typical power storage device for charging the storage battery modules equally, (1) a multi-winding transformer having the same number of secondary windings as each storage battery module (a primary winding and a plurality of secondary windings on the same core) From a wound transformer) to a secondary winding connected to each storage battery module via a diode, and (2) a dc / dc converter connected to each of the storage battery modules.
[0004]
The configuration of {circle around (1)} is described in [“Balanced Charge of Series Connected Battery Cells”, INTELEC'98, p. 311-315], a multi-winding transformer (a transformer in which one primary winding and a plurality of secondary windings are simultaneously wound on one magnetic core) is provided, and the secondary winding is converted from the multi-winding transformer. The wires are drawn out and connected to the positive and negative electrodes of the individual storage battery modules via diodes to charge the individual storage battery modules.
[0005]
The configuration of (2) is described in ["Dynamic Equalization Technologies for Series Battery Stacks Stacks", INTELEC'96, pp. 146-64. 514-521], a flyback dc / dc converter or a forward dc / dc converter is connected to each battery pack, and each dc / dc converter charges or discharges an individual storage battery module. . Further, this document also discloses a configuration in which charging and discharging are performed by one dc / dc converter (referred to as bi-directionally isolated flyback dc-dc converters).
[0006]
[Problems to be solved by the invention]
In order to apply the above-described conventional technology to an assembled battery including a large number of storage battery modules, there are problems such as complicated wiring of a transformer and an increase in the number of parts of a charging device.
[0007]
That is, according to the configuration of (1), since the secondary winding needs to be wound around one magnetic core in a concentrated manner, the wiring of the secondary winding connected to each storage battery module becomes long, and it is easy to get tangled. There was a problem. In a flyback transformer, the current energy supplied from the primary winding is temporarily stored in one magnetic core and then distributed to a plurality of storage battery modules. There was a problem that the core became large and the installation space was limited. Further, when the storage battery module is separated from the magnetic core, the wiring length of the secondary winding is increased, so that there is a problem that a voltage drop and a loss due to a resistance component increase.
[0008]
In the configuration of (2), the dc / dc converter is connected in accordance with the number of storage battery modules. Therefore, the number of components of the dc / dc converter (the main component is that between the primary winding and the secondary winding of the transformer. Flyback or forward transformer to insulate, photocoupler to detect battery module voltage, error amplifier to compare detected voltage to reference voltage to amplify differential voltage, and adjust on / off ratio of switch element of dc / dc converter by output of error amplifier Transmitters and switch elements).
[0009]
In view of the above circumstances, the present invention provides a power storage device that mainly charges a low-voltage storage battery module with a simple configuration, and charges each storage battery module equally after the voltage of each storage battery module becomes constant. The purpose is to provide. It is another object of the present invention to provide a power storage device for preventing a fully charged storage battery module from being overcharged when there are individual differences in conditions under which each storage battery module reaches full charge.
[0010]
[Means to solve the problem]
In order to solve the above problem, a power storage device of the present invention is a power storage device that connects a plurality of storage battery modules each having one or more storage battery cells connected in series and charges and discharges the storage battery modules. A flyback transformer and a rectifying element are provided, and a secondary winding of the flyback transformer is connected to a positive electrode and a negative electrode of the storage battery module via the rectifying element, and a primary winding of each of the flyback transformers is are connected in parallel with one switch element and the drive circuit and the DC power supply at both ends of the circuit connected in series, each said drive circuit of said rectifying element is connected to the rectifier element control circuit, the rectifier element control circuit each A full charge detection circuit that receives a signal of a charge state detection circuit provided in the storage battery module .
[0011]
[Action]
The present invention is different from the conventional invention in that a flyback transformer corresponding to a plurality of storage battery modules is used one-to-one, and the primary winding side of the flyback transformer is commonly turned on and off by one switch element.
[0012]
That is, in the present invention, since the flyback transformer is installed in each storage battery module, the secondary winding connected to the storage battery module can be shortened, so that it is not necessary to consider the power loss due to the voltage drop and the resistance. In addition, since most of the charging structure of the storage battery module is placed in the immediate vicinity of the storage battery module, it is not necessary to route the secondary winding, and the secondary winding is connected in advance to the anode and the cathode of the storage battery module. It is also possible to avoid the problem of incorrect wiring. Furthermore, the excitation current of the flyback transformer can be adjusted with a single switch element, and the power of the secondary winding side of the flyback transformer can be adjusted so that the fully charged storage battery module is not excessively charged. It becomes possible to limit with a MOS FET. Turning the power MOS FET on and off in synchronization with the switch element until the storage battery module reaches a full charge is a so-called synchronous rectification method, which also reduces the loss of the power storage device.
[0013]
The invention according to claim 1 aims to charge the storage battery modules prior to full charge and eliminate variations in the charging voltage of each storage battery module, but the storage battery modules that do not reach full charge are too fast. May be charged. In order to avoid this, in the invention according to claim 2, when the number of storage battery modules that have reached a full charge increases, the switching element is turned on and off by a signal of a full charge detection circuit.
It has a function to adjust the ratio. For example, when the number of storage battery modules that have reached a full charge increases, if the ON time of the switch element is shortened, the exciting current of the flyback transformer decreases and is supplied to the storage battery module during the OFF period of the switch element. The charging current can be reduced.
[0014]
According to the third aspect of the present invention, in the power storage device, the rectifying element is a power MOS FET, and is turned on / off by a rectifying element control circuit before each storage battery module is fully charged. The power MOS FET is cut off.
[0015]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
(Example 1)
FIG. 1 shows a first embodiment in which a diode 2 and a flyback transformer 1 are connected to a storage battery module 3 of the present invention. This drawing shows an example in which three sets of storage battery modules are connected in series, and a switch element 4, a drive circuit 5, and a DC power supply 6 are used as external circuits for charging the storage battery modules. In this figure, the reason why the capacitor 20 is connected in parallel with the storage battery module is to absorb the pulsating current of the flyback transformer 1, and the capacitor 20 is not always necessary.
[0017]
The secondary winding of each flyback transformer 1 is provided corresponding to the storage battery module 3, and the primary winding is connected in parallel between the DC power supply 1 and the switch element 4 in order.
[0018]
The flyback transformer 1 and the diode 2 are provided corresponding to each storage battery module 3 with the polarity shown. That is, the present circuit operates so that the exciting current is accumulated in the flyback transformer 1 when the switch element 4 is turned on, and the uniform charging current flows to the secondary winding side when the switch element 4 is turned off. Since the primary windings of the flyback transformers 1 are connected in a forward direction, there is no need to route connecting wires from both ends of each primary winding to the DC power supply 6 and the switch element 4, and the upper and lower flyback transformers 1 It is sufficient to connect the primary windings in sequence.
[0019]
Since the characteristics of the flyback transformer 1 do not necessarily have to be uniform as described later, the flyback transformer 1 may be mass-produced.
[0020]
FIG. 2 shows an equivalent circuit in which the exciting inductance of the flyback transformer 1 is shifted to the secondary winding side. This equivalent circuit shows a case where two sets of storage battery modules 3 are charged so that the operation of the circuit can be described at a minimum. The description of the operation shown in FIG. 2 is based on the case where the voltages of the storage battery modules are equal.
[0021]
As shown in FIG. 2A, a case where the switching element is turned on and the exciting current 7 flows through the flyback transformers 1a and 1b is defined as an operation start point. At this time, since the DC power supply voltage is applied to the exciting inductance, the exciting current 7 increases linearly with the ON time of the switch element. Further, currents from the storage battery modules 3a, 3b are blocked by the diodes 2a, 2b. Since this state continues until the switching element is turned off, it is necessary to design the magnetic cores of the flyback transformers 1a and 1b not to be saturated by the exciting current.
[0022]
FIG. 2B shows the flow of the exciting current 7 when the switch element is turned off. Excitation current 7 flows as a continuation flow into storage battery modules 3a and 3b through diodes 2a and 2b, and charges storage battery modules 3a and 3b. This state continues until the exciting current becomes zero, and when the exciting current becomes zero, the state remains stationary until the switch element is turned on.
[0023]
Next, FIG. 3 shows an explanatory diagram of the operation of this circuit when the voltages of the storage battery modules 3a and 3b are different.
[0024]
In FIG. 3, it is assumed that the voltage of the upper storage battery module 3a is slightly lower than the voltage of the lower storage battery module 3b. When the switch element is turned off, the exciting current accumulated when the switch element is turned on starts charging the storage battery modules 3a and 3b as in FIG. However, the excitation current of the lower flyback transformer 1b (indicated by a dotted line) sneaks toward the storage battery module 3a having a lower voltage and charges the upper storage battery module 3a together with the excitation current of the upper flyback transformer 1a. , The charging of the upper storage battery module 3a is promoted. Eventually, as shown in FIG. 2, the storage battery modules 3a and 3b are charged to the same voltage, and the storage battery modules 3a and 3b are charged along a route as shown in FIG. 2B. Since the switching of the path of the exciting current for compensating for the insufficient charging mainly depends on the voltage of the storage battery module 3a, the same effect can be obtained even if the characteristics of the flyback transformers 1a and 1b are not uniform.
[0025]
FIG. 4 shows the effect of the embodiment having the configuration of FIG. FIG. 4 shows a storage battery module with a DC power supply voltage of 24 V, a magnetizing inductance of a flyback transformer (converted value on the secondary winding side: about 60 μH), an on time of the switch element: about 2 μs, and an off time of the switch element: about 3 μs. This is an example in which a 200 μF electrolytic capacitor is used as a simulation. The solid line corresponds to the storage battery module with a slightly lower voltage, and the broken line corresponds to the storage battery module with a higher voltage. The reason why the waveform is not smooth is that the charging current of the storage battery module is discontinuous, and the effect of the present invention that the voltage of the storage battery module becomes uniform over time is shown.
[0026]
(Examples 2 and 3)
Next, second and third embodiments of the present invention will be described. Although it has been shown that the voltage of the storage battery modules having different voltages can be equalized by the circuit of the first embodiment of the present invention, the case where the storage battery modules are equalized is not always the optimum state of charge. For example, it is assumed that a certain storage battery module reaches full charge at a lower voltage than another storage battery module. If the storage battery module that has reached full charge is further charged, it becomes overcharged, which affects the life. Second and third embodiments assuming such a case will be described with reference to FIG.
[0027]
The difference between FIG. 1 and FIG. 5 is that a power MOS FET (rectifying element) 13 is used in place of the diode 2, and each storage battery module has a charge state detection circuit 9 and a full charge detection circuit 11 that receives a signal from the charge state detection circuit And the rectifying element control circuit 12 is added. Further, the rectifying element control circuit has a function of controlling the drive circuit 5 to adjust the on / off ratio of the switch element. Hereinafter, each effect will be described.
[0028]
Normally, the rectifying element control circuit 12 sends an ON signal to the rectifying element 13 when the ON signal of the switch element 4 changes to an OFF signal. When the off signal of the switch element 4 changes to an on signal, the off signal is sent to the rectifying element 13. That is, the switching element 4 and the rectifying element 13 operate with signals having opposite phases.
[0029]
The charge state detection circuit 9 converts the measurement result of the temperature or the charge voltage of the storage battery module 3 into an electric signal and sends it to the full charge detection circuit 11.
[0030]
Full charge detection circuit 11 receives a signal from the charge state detection circuit and determines whether each storage battery module is in a fully charged state. Here, the determination as to whether or not the battery is fully charged is made by a quick charge control method for a nickel-metal hydride battery or the like. The rapid charging control method is roughly classified into a-△ V method and a method using a temperature rise of the battery, and the-△ V method utilizes a phenomenon in which the voltage of the battery reaches a peak at the end of charging and then decreases. The method using the temperature rise detects a temperature rise value (ΔT) or a temperature rise rate (dT / dt) from the start of charging.
When detecting that one of the storage battery modules has reached full charge, the rectifier control circuit 12 shuts off the on / off signal of the rectifier 13 connected to the storage battery module. At the time of conduction of the rectifying element 13 before being cut off, the charging current (the voltage drop due to the current flowing through the on-resistance divided by the current flowing through the on-resistance / the voltage drop of the built-in diode until reaching the voltage drop of the built-in diode). Since the built-in diode is also used at a higher current via the resistor), after the cutoff, it can not flow except the built-in diode 16, so that the voltage drop increases. For this reason, it becomes substantially equivalent to a state where a large voltage is connected in series with the storage battery module, the charging current of the storage battery module is reduced, and overcharging can be prevented.
[0031]
FIG. 6 shows an example in which the invention of FIG. 5 is applied to a power storage device having the same circuit constants as FIG. 4, and shows changes in charging voltages of two sets of storage battery modules after the battery modules indicated by solid lines reach full charge. ing. It can be seen that the voltage rise value of the solid line where the signal of the power MOS FET is cut off is suppressed lower than the voltage rise rate of the broken line where the signal is not cut off, thereby preventing overcharging.
[0032]
In order to further reduce the rate of voltage rise and prevent overcharging, it is effective to reduce the on / off ratio of the switch element by the signal 12 of the rectifying element control circuit and reduce the exciting current of the flyback transformer 9. is there.
[0033]
【The invention's effect】
As described above, according to the present invention, the following effects can be achieved.
[0034]
(1) In a power storage device for connecting a plurality of storage battery modules formed by connecting one or more storage battery cells in series and charging / discharging the storage battery modules, one end connected to both ends of a series circuit of a DC power supply and a switch element. As described above, since the exciting current of the flyback transformer is diverted so as to mainly charge the storage battery module having a low charging voltage, the charging voltage of each storage battery can be quickly equalized.
[0035]
In addition, since most of the charging structure of the storage battery module is placed close to the storage battery module, it is not necessary to route the secondary winding, and the secondary winding is connected in advance to the positive and negative electrodes of the storage battery module. This also makes it possible to avoid the problem of incorrect wiring.
[0036]
(2) If the full charge voltage of the storage battery module is expected to vary, use the on-resistance of the power MOS FET connected to the secondary side of the flyback transformer and the characteristics of the built-in diode to achieve full charge first. The reached storage battery module can be prevented from being overcharged further.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a first embodiment of the present invention.
FIG. 2 is a basic explanatory diagram of the first embodiment.
FIG. 3 is a detailed explanatory diagram of the present invention.
FIG. 4 is an experimental result showing the effect of the first embodiment.
FIG. 5 is a circuit diagram of the second and third embodiments.
FIG. 6 is an experimental result showing the effect of the second embodiment.
[Explanation of symbols]
1, 1a, 1b: flyback transformer,
2, 2a, 2b: diode,
3, 3a, 3b: storage battery module,
4: switch element,
5: drive circuit,
6: DC power supply,
7, exciting current,
8, the shunting excitation current,
9: Charge state detection circuit,
10: Common control unit,
11: Full charge detection circuit
12: rectifying element control circuit,
13: Power MOS FET (including built-in diode 16)
14: rectifier on / off signal,
15: ON / OFF ratio adjustment signal of the switch element,
16: Built-in diode,
20: condenser.

Claims (3)

In a power storage device for connecting a plurality of storage battery modules each having one or more storage cells connected in series and charging / discharging the storage battery modules, a flyback transformer and a rectifying element are provided for each of the storage battery modules; connected back transformer secondary winding via the rectifying device to a positive electrode and a negative electrode of the battery module, the primary winding of each of said flyback transformer connected in series a DC power supply and one switch element and the driving circuit Each of the rectifying elements and the driving circuit are connected to a rectifying element control circuit, and the rectifying element control circuit receives a signal of a charge state detecting circuit provided in each storage battery module. A power storage device connected to a full-charge detection circuit . The rectifying element control circuit has a function of controlling the drive circuit to adjust the on / off ratio of the switch element, and a rectifier connected to the storage battery module when detecting that one of the storage battery modules has reached a full charge. electrical storage device according to claim 1, characterized in that it has a function of blocking off signal of the element. The rectifying element, the electric storage device according to claim 1 or claim 2, wherein the Power MOS FET der Turkey.

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