JP2008301648A - Power system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply system for avoiding degradation in storage capacity due to heavy load and increasing the battery life. <P>SOLUTION: This power supply system includes: a rectifier 2 and a battery pack 3 constituted of lead storage battery cells. The rectifier 2 converts AC power input from a commercial power supply 1 into DC power to be output, thereby feeding power to a load 4 and charging the battery pack 3. The charging path and the discharging path of the battery pack 3 are independently wired. The charging path is connected to a diode 5b in such a direction as to supply power only in the charging direction, while the discharging path is connected to a diode 5a in such a direction as to supply power only in the discharging direction. The output of the rectifier 2 is connected in parallel with the output of the battery pack 3 through the diode 5a at a connection point 6. When the commercial power supply 1 is effective, the output voltage of the battery pack 3 through the diode 5a is lower than the output voltage of the rectifier 2 at the connection point 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power supply system, and more particularly, to a power supply system that supplies DC power to a load and has a battery as a backup during a power failure.

  Generally, in a power supply system that supplies power to a DC load device, a rectifier that receives commercial AC power and outputs DC power such as DC 48V is used. Furthermore, a storage battery is provided at the output of the rectifier in order to continue power supply to the load device even when the commercial power fails.

  When a storage battery is applied to a DC power supply system, an assembled battery in which one or more storage batteries called single cells are connected in parallel is used.

  FIG. 4 shows a DC backup power supply system in which a rectifier and a storage battery are combined.

  In FIG. 4, the AC power of the commercial power source 1 is supplied to the rectifier 2, and the rectifier 2 converts the AC power into predetermined DC power and supplies it to the load 4. The assembled battery 3 is charged via the rectifier 2 when the commercial power source 1 is active, and discharges to the load due to a power failure of the commercial power source 1.

Patent Documents 1, 2, and 3 listed below describe a power supply device that includes a plurality of assembled batteries, a charge control unit, and a discharge control unit. Patent Document 1 describes the assembly based on the manufacturing date of the assembled battery. It is described that the battery usable period is calculated and the assembled battery replacement date is displayed, and Patent Document 2 describes that a battery monitoring unit for performing a discharge capacity test of the assembled battery is provided, and Patent Document 3 describes It is described that the battery monitoring means calculates the remaining capacity of the assembled battery and determines the auxiliary charging time of the assembled battery based on the result.
JP 2004-119112 A JP 2004-120856 A JP 2004-120857 A

  The problem of the power supply system combining the rectifier and the assembled battery will be described by taking the DC backup power supply system of FIG. 4 as an example. The rectifier 2 converts the commercial power supply 1 (AC power) into DC power, and the output voltage is set to 51V DC. The assembled battery 3 is configured by connecting lead storage battery cells in series. When the commercial power source 1 is valid, the rectifier 2 converts AC power from the commercial power source 1 into DC power, and supplies the battery 4 to the load 4 while charging the assembled battery 3 with the DC power.

  The wiring resistance from the rectifier 2 to the connection point 6 is 10 mΩ (for two wires), the wiring resistance from the connection point 6 to the load 4 is 10 mΩ (for two wires), and the wiring resistance from the connection point 6 to the assembled battery 3 is 10 mΩ ( 2).

  In the above power supply system, problems such as a decrease in power storage capacity and a reduction in battery life occur due to load fluctuations and heavy loads, as described below.

<Problem of storage capacity decline due to heavy load>
When the required current of the load 4 is 100 A, the current flowing from the connection point 6 to the load 4 is 100 A, and the current flowing from the rectifier 2 to the connection point 6, that is, the output current of the rectifier 2 is set in 100 A supplied to the load 4. A value obtained by adding the charging current of the battery 3 is obtained. When the charging of the assembled battery 3 is completed, the current output from the rectifier 2 is 100A required by the load 4, the voltage at the connection point 6 is 50V, and the supply voltage to the load 4 is 49V. At this time, the voltage of the assembled battery 3 is 50V.

  When the load 4 is stopped and no power is supplied, if the charging of the assembled battery 3 is completed, the rectifier 2 has almost no output current, so the voltage of the assembled battery 3 is 51V.

  Thus, when the required current of the load 4 is large, the full charge voltage of the assembled battery 3 is lowered. For this reason, when a load is large, there exists a problem that the electrical storage capacity of an assembled battery falls.

<Battery life reduction due to load fluctuations>
When the load 4 is stopped and no electric power is supplied, if the charging of the assembled battery 3 is completed, the rectifier 2 has almost no output current, so the voltage of the assembled battery 3 is 51V. Thereafter, when the load 4 is activated and the rectifier 2 starts supplying power to the load 4 and supplies 100 A to the load 4, the voltage at the connection point 6 is 50V and the power supply voltage to the load 4 is 49V. At this time, since the voltage (51V) of the assembled battery 3 is higher than the voltage 50V at the connection point 6, the assembled battery 3 takes part of the power supply to the load 4, and the assembled battery 3 is discharged. Thereafter, when the required current of the load 4 decreases to 50 A, the voltage at the connection point 6 becomes 50.5 V, and the assembled battery 3 is charged by this voltage. When the load 4 further stops, the output voltage 51V of the rectifier 2 becomes the charging voltage of the assembled battery 3.

  Thus, when the load fluctuates, the assembled battery 3 is repeatedly charged and discharged, and such an increase in charge / discharge cycles causes a reduction in battery life.

  The problem that the rectifier supplies power to the load and charges the battery to reduce the storage capacity of the battery and reduce the battery life is not limited to the case of a lead storage battery system, but a nickel hydride storage battery or a lithium ion battery. In a backup power supply system having an assembled battery formed by combining secondary batteries such as a battery system, and further supplying a load with power output from a plurality of assembled batteries formed by combining a plurality of batteries including a primary battery It is a problem that also occurs.

  The present invention has been made in view of the above-described problems that the rectifier supplies power to the load and charges the battery, thereby reducing the storage capacity of the battery and reducing the battery life. An object of the present invention is to provide a power supply system that avoids a decrease in power storage capacity due to a heavy load and extends battery life.

In order to solve the above problem, in the present invention, as described in claim 1,
An assembled battery formed by combining a plurality of batteries, a rectifier that converts alternating current power into direct current power to supply power to the load, and when the rectifier is stopped, power output from the assembled battery is supplied to the load In the power supply system, the rectifier when the discharge circuit for discharging the assembled battery from the rectifier to the power supply line to the load is connected in parallel at a first connection point, and the rectifier outputs a rated current. When the voltage drop from the first connection point to the first connection point is the first voltage drop, and the minimum voltage drop from the assembled battery to the first connection point is the second voltage drop, the rectifier output voltage The voltage obtained by subtracting the first voltage drop from the battery pack is larger than the voltage obtained by subtracting the second voltage drop from the assembled battery voltage.

In the present invention, as described in claim 2,
The power supply system according to claim 1, wherein the discharge circuit includes a first diode that passes power only in a discharge direction.

In the present invention, as described in claim 3,
2. The power supply system according to claim 1, wherein the discharge circuit outputs a power having a voltage lower than a voltage obtained by subtracting the first voltage drop from the rectifier output voltage to the first connection point. A power supply system including a DC / DC converter is configured.

In the present invention, as described in claim 4,
4. The power supply system according to claim 1, wherein the battery is a secondary battery, the rectifier also charges the assembled battery, and charges the assembled battery to a power supply line from the rectifier to the load. A charging power circuit is connected in parallel at a second connection point, and the charging power circuit includes a second diode or a charging DC / DC converter that passes power only in the charging direction.

In the present invention, as described in claim 5,
4. The power supply system according to claim 1, wherein the battery is a secondary battery, and includes a charging rectifier that converts AC power into DC power, and the charging rectifier charges the assembled battery. The power supply system characterized by this is configured.

Further, in the present invention, as described in claim 6,
4. The power supply system according to claim 1, 2, or 3, wherein the battery is a secondary battery.

In the present invention, as described in claim 7,
The power supply system according to claim 4, 5 or 6, wherein the secondary battery is a lead storage battery, a nickel hydride storage battery, or a lithium ion storage battery.

  According to the power supply system of the present invention, the following effects can be obtained.

  For example, since charging is performed by a charger, the storage capacity is not reduced by a heavy load, and the assembled battery output voltage is higher than the rectifier output voltage at the connection point as long as the output of the rectifier is within the rated output. As a result, the battery pack will not discharge unless the rectifier stops, and it will be possible to provide a power supply system that will not repeatedly charge and discharge due to load fluctuations. It is possible to provide a power supply system that extends the length.

  In the power supply system according to the present invention, for example, the assembled battery is charged via a charging rectifier or a DC / DC converter. Further, for example, a discharge diode or a DC / DC converter is provided at the assembled battery output, and the output voltage of the discharge diode or the DC / DC converter at the connection point between the load power supply rectifier and the power supply line to the load is the load power supply rectifier. The output voltage should be lower. Therefore, for example, when the load power supply rectifier outputs the maximum current, the voltage drop from the load power supply rectifier to the connection point is defined as the first voltage drop, and the voltage drop from the assembled battery to the connection point is the first voltage drop. When the voltage drop is 2, the voltage value obtained by subtracting the first voltage drop from the load power supply rectifier output voltage is greater than the voltage value obtained by subtracting the second voltage drop from the assembled battery output voltage. Configure the system.

  Hereinafter, embodiments of the present invention will be described by way of examples in which the assembled battery is a lead storage battery, a nickel hydride storage battery, or a lithium ion storage battery, but the present invention is not limited thereto.

<Embodiment 1>
FIG. 1 is a diagram for explaining an embodiment of the present invention. In FIG. 1, a battery pack 3 is configured by connecting 24 lead acid battery cells (single cell 2.0 V, 1000 Ah) in series. The rectifier 2 converts AC power input from the commercial power source 1 into DC power, outputs DC 49V and a rated output 100A, and supplies power to the load 4 and charges the assembled battery 3 by the output.

  The charging circuit and the discharging circuit of the assembled battery 3 are separately wired, and the charging circuit has a diode 5b that is a second diode that passes power only in the charging direction, and the discharging circuit passes the power only in the discharging direction. 1 diode 5a which is 1 diode. The output of the rectifier 2 and the output of the battery pack 3 via the diode 5a are connected in parallel at the connection point 6 which is the first connection point and output to the load 4.

  The diodes 5a and 5b have a performance of stepping down at least 1V. Therefore, during normal operation (when receiving commercial power), the assembled battery 3 is charged until the voltage reaches 48 V obtained by subtracting the voltage drop of the diode 5b from the output voltage of the rectifier 2, and charging stops there.

  When the commercial power source 1 is interrupted, the output voltage of the rectifier 2 is reduced, so that the discharge from the assembled battery 3 to the load 4 is performed. However, due to the voltage drop of the diode 5a, the output voltage of the assembled battery 3 via the diode 5a The maximum is 47V. In this case, the second voltage drop that is the minimum value of the voltage drop from the assembled battery 3 to the connection point 6 that is the first connection point is 1V. The voltage output from the assembled battery 3 at the connection point 6 is 47 V at the maximum. This voltage (47V) is the maximum value of the voltage obtained by subtracting the second voltage drop from the battery voltage of the assembled battery 3.

Here, the wiring from the rectifier 2 to the connection point 6 so that the voltage drop from the rectifier 2 to the connection point 6 when the rectifier 2 outputs the rated output of 100 A, that is, the first voltage drop is smaller than 2V. Is selected. In this way, when the commercial power source 1 is effective, the voltage (greater than 47V) obtained by subtracting the first voltage drop (smaller than 2V) from the output voltage (49V) of the rectifier 2 is the assembled battery. 3 is larger than the voltage obtained by subtracting the second voltage drop from the voltage 3 (maximum 47V), and at the connection point 6, the output voltage of the rectifier 2 is always higher than the output voltage from the assembled battery 3 via the diode 5a. As long as the output of the rectifier 2 is within the rated output, discharge from the assembled battery 3 does not occur. Since the voltage drop of the wiring is obtained by the product of the wiring resistance and the current, for example, the material, the wire diameter, and the length of the wiring may be determined based on the rated output current of the rectifier 2 and the voltage drop limit value. In other words, in order to make the first voltage drop smaller than 2V, the wiring resistance is R _L and R _L × 100A <2V is satisfied. However, this is a case where the output-side internal resistance of the rectifier 2 is ignored, and when the output-side internal resistance R _{OUT of} the rectifier 2 cannot be ignored, (R _OUT + R _L ) × 100A <2V is established. There must be.

  Thus, even if there is an output fluctuation (within the rated output) of the rectifier 2 during commercial power supply, the assembled battery 3 is not discharged, so that it is possible to prevent deterioration of the battery due to the charge / discharge cycle.

  In the present embodiment, the voltage drop of the diodes 5a and 5b is the same 1V. However, if the output voltage through the diode 5a of the assembled battery 3 is lower than the output voltage of the rectifier 2 at the connection point 6, the diode The voltage drop values of 5a and 5b may be different values.

<Embodiment 2>
FIG. 2 is a diagram for explaining an embodiment of the present invention. In FIG. 2, 40 assembled nickel-metal hydride storage battery cells (single cell 1.2 V, 100 Ah) are connected in series to form a battery pack 3. The rectifier 2 converts AC power input from the commercial power source 1 into DC power and outputs a direct current of 52 V and a rated output of 100 A. The output of the assembled battery 3 via the power supply to the load 4 and the charger 8 is output. Charge the battery. A charging electric circuit and a discharging electric circuit of the assembled battery 3 are wired separately, a charger 8 is provided in the charging electric circuit, and a discharging device 7 is provided in the discharging electric circuit.

  The output of the rectifier 2 and the output of the discharger 7 are connected in parallel at the connection point 6, which is the first connection point, and output to the load 4.

  The charging circuit is connected in parallel to the power supply line from the rectifier 2 to the load 4 at the connection point 6 ′, which is the second connection point, and the charger 8 detects a decrease in the storage capacity of the assembled battery 3 and supplies commercial power. Charging is sometimes started, the assembled battery 3 is charged with a constant current of 20 A, charging is stopped upon determining full charge. Since the fully charged voltage of the assembled battery 3 reaches a maximum of 64 V, when the voltage is insufficient, charging is performed by boosting the output voltage of the rectifier 2 by the charging DC / DC converter provided in the charger 8.

  The discharger 7 has a DC / DC converter for discharge, and thereby has a function of stepping down so that the output voltage does not exceed 50V. Therefore, the voltage obtained by subtracting the second voltage drop from the battery voltage of the assembled battery 3 is 50V or less.

Here, the wiring from the rectifier 2 to the connection point 6 so that the voltage drop (first voltage drop) from the rectifier 2 to the connection point 6 when the rectifier 2 outputs 100 A which is the rated output is smaller than 2V. Is selected. In this way, when the commercial power source 1 is effective, the discharging DC / DC converter is configured such that the voltage (50 V) obtained by subtracting the first voltage drop (smaller than 2 V) from the output voltage (52 V) of the rectifier 2. Voltage of 50V or less, which is a voltage obtained by subtracting the second voltage drop from the battery voltage of the assembled battery 3, and the output voltage of the rectifier 2 is released at the connection point 6. Since it always becomes higher than the output voltage of the electric device 7, the discharge from the assembled battery 3 does not occur as long as the output of the rectifier 2 is within the rated output. Since the voltage drop of the wiring is obtained by the product of the wiring resistance and the current, for example, the material, the wire diameter, and the length of the wiring may be determined based on the rated output current of the rectifier 2 and the voltage drop limit value. In other words, in order to make the first voltage drop smaller than 2V, the wiring resistance is R _L and R _L × 100A <2V is satisfied. However, this is a case where the output-side internal resistance of the rectifier 2 is ignored, and when the output-side internal resistance R _{OUT of} the rectifier 2 cannot be ignored, (R _OUT + R _L ) × 100A <2V is established. There must be.

  Thus, even if there is an output fluctuation (within the rated output) of the rectifier 2 during commercial power supply, the assembled battery 3 is not discharged, so that it is possible to prevent deterioration of the battery due to the charge / discharge cycle. In addition, since the battery pack 3 is charged by the charger 8, even if the input voltage of the battery charger 8 decreases due to an increase in the load, the battery pack 3 can be boosted and charged to effectively use the storage capacity of the battery pack 3. Become.

<Embodiment 3>
FIG. 3 is a diagram for explaining an embodiment of the present invention. In FIG. 3, 12 assembled lithium ion storage battery cells (single cell 4.0 V, 80 Ah) are connected in series to form the assembled battery 3. The rectifier 2 converts AC power input from the commercial power source 1 into DC power, outputs DC 49V and a rated output 100A, and supplies power to the load 4.

  The charging rectifier 9 converts the AC power input from the commercial power source 1 into DC power and outputs DC 48V to charge the assembled battery 3, and the voltage of the assembled battery 3 reaches the output voltage 48V to be charged. Stop. The power output from the assembled battery 3 is connected to the connection point 6 via a diode 5a that passes power only in the discharging direction. The output of the rectifier 2 and the output of the assembled battery 3 via the diode 5 a are connected in parallel at the connection point 6 and output to the load 4. The diode 5a has a performance of stepping down at least 1V.

  When the commercial power source 1 fails, the output voltage of the rectifier 2 decreases, so that the discharge from the assembled battery 3 to the load 4 is performed. However, the output voltage of the assembled battery 3 via the diode 5a is maximum due to the voltage drop of the diode 5a. But it is 47V. That is, the voltage output from the assembled battery 3 at the connection point 6 is 47 V at the maximum. This voltage (47V) is the maximum value of the voltage obtained by subtracting the second voltage drop from the battery voltage of the assembled battery 3.

Here, the wiring from the rectifier 2 to the connection point 6 so that the voltage drop from the rectifier 2 to the connection point 6 when the rectifier 2 outputs the rated output of 100 A, that is, the first voltage drop is smaller than 2V. Is selected. In this way, when the commercial power source 1 is effective, the voltage (greater than 47V) obtained by subtracting the first voltage drop (smaller than 2V) from the output voltage (49V) of the rectifier 2 is the assembled battery. 3 is larger than the voltage obtained by subtracting the second voltage drop from the voltage 3 (maximum 47V), and at the connection point 6, the output voltage of the rectifier 2 is always higher than the output voltage from the assembled battery 3 via the diode 5a. As long as the output of the rectifier 2 is within the rated output, discharge from the assembled battery 3 does not occur. Since the voltage drop of the wiring is obtained by the product of the wiring resistance and the current, for example, the material, the wire diameter, and the length of the wiring may be determined based on the rated output current of the rectifier 2 and the voltage drop limit value. In other words, in order to make the first voltage drop smaller than 2V, the wiring resistance is R _L and R _L × 100A <2V is satisfied. However, this is a case where the output-side internal resistance of the rectifier 2 is ignored, and when the output-side internal resistance R _{OUT of} the rectifier 2 cannot be ignored, (R _OUT + R _L ) × 100A <2V is established. There must be.

  Thus, even if there is an output fluctuation (within the rated output) of the rectifier 2 during commercial power supply, the assembled battery 3 is not discharged, so that it is possible to prevent deterioration of the battery due to the charge / discharge cycle. Further, since charging of the assembled battery 3 is performed by the charging rectifier 9, it is possible to effectively use the storage capacity of the assembled battery 3 regardless of the output of the rectifier 2.

  A feature of the power supply system according to the present invention is that, for example, the assembled battery is charged via a charging rectifier or a charging DC / DC converter, a discharging diode or a discharging DC / DC converter is provided at the assembled battery output, and the load The output voltage of the discharge diode or the DC / DC converter at the connection point between the power supply rectifier and the power supply line to the load is set to be lower than the output voltage of the load power supply rectifier.

  Due to this feature, for example, the assembled battery is charged via the charging rectifier or the charging DC / DC converter, so that the storage capacity is not reduced by a heavy load, and the assembled battery output voltage is the first connection. Since it becomes lower than the rectifier output voltage at a point, it is possible to provide a power supply system in which the assembled battery is not discharged unless the rectifier stops, and charging / discharging is not repeated due to load fluctuations.

  As described above, the embodiment of the present invention has been described by way of example in which the battery is a lead storage battery, a nickel hydride storage battery, or a lithium ion storage battery, but the present invention is not limited to this.

  Below, the effect produced by this invention is demonstrated.

  (1) When the rectifier performs both power feeding to the load and charging of the assembled battery, a problem arises in that the full charge voltage of the assembled battery decreases due to the large required current of the load, and the storage capacity of the assembled battery decreases. To do.

  According to the present invention, for example, charging is performed by a charger including a DC / DC converter, so that it is possible to provide a power supply system in which the storage capacity is not reduced by a heavy load.

  (2) When the rectifier performs both power feeding to the load and charging of the assembled battery, the assembled battery repeats charging and discharging when the load fluctuates, and an increase in charge / discharge cycles leads to a reduction in battery life. The problem occurs.

  According to the present invention, since the assembled battery output voltage is lower than the rectifier output voltage at the connection point, it is possible to provide a power supply system in which the assembled battery does not discharge unless the rectifier stops and does not repeatedly charge and discharge due to load fluctuations. It becomes.

It is a figure explaining the example of embodiment of this invention. It is a figure explaining the example of embodiment of this invention. It is a figure explaining the example of embodiment of this invention. It is a block diagram of the power supply system which a rectifier performs both the electric power feeding to load, and charge of an assembled battery.

Explanation of symbols

  1: commercial power supply, 2: rectifier, 3: assembled battery, 4: load, 5a, 5b: diode, 6, 6 ': connection point, 7: discharger, 8: charger, 9: charging rectifier.

Claims (7)

An assembled battery formed by combining a plurality of batteries, a rectifier that converts alternating current power into direct current power to supply power to the load, and when the rectifier is stopped, power output from the assembled battery is supplied to the load Power system
A discharge circuit for discharging the assembled battery to a power supply line from the rectifier to the load is connected in parallel at a first connection point,
A voltage drop from the rectifier to the first connection point when the rectifier outputs a rated current is a first voltage drop,
When the minimum value of the voltage drop from the assembled battery to the first connection point is the second voltage drop,
The power supply system, wherein a voltage obtained by subtracting the first voltage drop from the rectifier output voltage is larger than a voltage obtained by subtracting the second voltage drop from the assembled battery voltage. The power supply system according to claim 1,
The power supply system, wherein the discharge circuit includes a first diode that passes power only in a discharge direction. The power supply system according to claim 1,
The discharge circuit includes a discharge DC / DC converter that outputs electric power having a voltage lower than a voltage obtained by subtracting the first voltage drop from the rectifier output voltage to the first connection point. Power system. The power supply system according to claim 1, 2, or 3,
The battery is a secondary battery;
The rectifier also charges the assembled battery,
A charging circuit for charging the assembled battery from the rectifier to the load is connected in parallel at a second connection point,
The power supply system according to claim 1, wherein the charging circuit includes a second diode or a charging DC / DC converter that passes power only in a charging direction. The power supply system according to claim 1, 2, or 3,
The battery is a secondary battery;
A power supply system comprising a charging rectifier that converts AC power into DC power, and the charging rectifier charges the assembled battery. The power supply system according to claim 1, 2, or 3,
The power supply system, wherein the battery is a secondary battery. The power supply system according to claim 4, 5 or 6,
The secondary battery is a lead storage battery, a nickel hydride storage battery, or a lithium ion storage battery.

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