JP5819783B2 - Uninterruptible power supply system - Google Patents

Description

  The present invention relates to an uninterruptible power supply system, and more particularly to a power supply system including a plurality of uninterruptible power supply apparatuses.

  A power supply system configured to share a storage battery among a plurality of uninterruptible power supplies (UPS) has been proposed. For example, Japanese Patent Application Laid-Open No. 2004-357467 (Patent Document 1) discloses an uninterruptible power supply system including a plurality of uninterruptible power supply apparatuses and storage batteries commonly connected to the uninterruptible power supply apparatuses.

  Each uninterruptible power supply has an abnormality detection means. When the output voltage of the storage battery drops to the nominal voltage of the storage battery, the abnormality detection means determines that the converter has stopped in any of the plurality of uninterruptible power supplies. In this case, the abnormality detection means changes the DC voltage reference value of the other converter and the charging current reference of the storage battery.

JP 2004-357467 A

  According to the configuration described in Japanese Patent Application Laid-Open No. 2004-357467 (Patent Document 1), when one converter stops, even if a converter stop signal is not exchanged between a plurality of uninterruptible power supplies, The overdischarge of the storage battery can be prevented. However, a healthy uninterruptible power supply (that is, a converter that is normal) continues power supply while preventing overdischarge of the storage battery. For this reason, there is a possibility that the abnormality becomes delayed.

  Further, in the uninterruptible power supply with the converter stopped, if the inverter is normal, power is supplied from the storage battery to the inverter. For this reason, the electric current output from a storage battery increases compared with usual. If the current passing through the inverter is larger than usual, the efficiency of the inverter may be reduced. In addition, there is a concern that the deterioration of the storage battery proceeds due to an increase in the current output from the storage battery.

  In order to prevent a large current from being output from the storage battery, it is possible to disconnect abnormal (that is, the converter has stopped) uninterruptible power supply and storage battery from the system and continue power supply with a healthy uninterruptible power supply. It is done. However, when the storage battery is disconnected from the system, the storage battery cannot be charged by a sound uninterruptible power supply.

  An object of the present invention is to provide an uninterruptible power supply system capable of continuing reliable power supply.

An uninterruptible power supply system according to an aspect of the present invention is provided in common for a plurality of uninterruptible power supplies provided in parallel to a load and a plurality of uninterruptible power supplies, and charges and discharges DC power. A storage battery. Each of the plurality of uninterruptible power supplies converts AC power from an AC power source into DC power, and receives DC power from at least one of the converter and the storage battery, and a converter whose DC side is electrically connected to the storage battery. Thus, an inverter that converts the DC power into AC power supplied to a load, and a control circuit that monitors the operating state of the converter and controls the converter and the inverter based on the monitoring result. When the DC voltage (battery voltage) of the storage battery decreases despite the fact that the converter is normal, the control circuit increases the output power of the converter and increases the DC voltage. When the converter is stopped and the battery voltage is lowered, the control circuit stops the inverter in response to the first reference voltage being reached after the battery voltage is changed from being lowered to rising.

  ADVANTAGE OF THE INVENTION According to this invention, the uninterruptible power supply system which can continue highly reliable electric power feeding is realizable.

1 is a schematic configuration diagram of an uninterruptible power supply system according to an embodiment of the present invention. It is a 1st figure for demonstrating operation | movement of the uninterruptible power supply system 100 when abnormality arises in the converter 5a of the uninterruptible power supply 4a shown in FIG. It is a 2nd figure for demonstrating operation | movement of the uninterruptible power supply system 100 when abnormality arises in the converter 5a of the uninterruptible power supply 4a shown in FIG. FIG. 7 is a third diagram for explaining the operation of uninterruptible power supply system 100 when an abnormality occurs in converter 5a of uninterruptible power supply 4a shown in FIG. It is a figure explaining the 1st electric power feeding system compared with an embodiment of the invention. It is a figure explaining the 2nd electric power feeding system compared with an embodiment of the invention. It is a figure explaining the electric power feeding system which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram of an uninterruptible power supply system according to an embodiment of the present invention. Referring to FIG. 1, uninterruptible power supply system 100 according to an embodiment of the present invention includes a storage battery 2 and uninterruptible power supply apparatuses 4a and 4b. Uninterruptible power supplies 4a and 4b are connected to AC power supplies 1a and 1b, respectively. Each of storage battery 2 and load 3 is provided in common for uninterruptible power supplies 4a and 4b.

  The uninterruptible power supply 4a includes a converter 5a, an inverter 6a, a DC chopper 7a, a control circuit 8a, switches 9a, 10a, 11a, and current sensors 12a, 13a, 14a.

  Converter 5a converts AC power supplied from AC power supply 1a into DC power. Inverter 6 a converts DC power supplied from at least one of converter 5 a and DC chopper 7 a into AC power supplied to load 3. When DC power is supplied from the storage battery 2, the DC chopper 7a converts the voltage of the storage battery 2 into a DC voltage input to the inverter 6a. On the other hand, when charging the storage battery 2, the DC chopper 7 a converts the DC voltage output from the converter 5 a into a voltage input to the storage battery 2. Therefore, the DC side of converter 5a and the DC side of inverter 6a are electrically connected to storage battery 2 via DC chopper 7a. The voltage VB indicates the rated voltage of the storage battery 2. The normal voltage of the storage battery 2 is VB.

  Switch 9a is provided between AC power supply 1a and converter 5a. The switch 10a is provided between the storage battery 2 and the DC chopper 7a. The switch 11a is provided between the inverter 6a and the load 3.

  Current sensor 12a detects a current flowing between AC power supply 1a and converter 5a. The current sensor 13a detects a current flowing between the storage battery 2 and the DC chopper 7a. The current sensor 14 a detects a current flowing between the inverter 6 a and the load 3.

  The control circuit 8a controls the converter 5a, the inverter 6a, and the DC chopper 7a. The control circuit 8a includes an operation state determination unit 21a and a control unit 22a.

  The operating state determination unit 21a determines whether or not the converter 5a is operating normally by monitoring the converter 5a. Further, the operating state determination unit 21a monitors the voltage of the storage battery 2 and the current IB1 detected by the current sensor 13a. Control unit 22a controls converter 5a, inverter 6a, and DC chopper 7a based on a signal from current sensor 12a, a signal from current sensor 14a, and a determination / monitoring result of operation state determination unit 21a. In addition, well-known control, such as PWM control, can be applied to the control method of converter 5a, inverter 6a, and DC chopper 7a by control unit 22a.

  The uninterruptible power supply 4b has the same configuration as the uninterruptible power supply 4a. The uninterruptible power supply 4b includes a converter 5b, an inverter 6b, a DC chopper 7b, a control circuit 8b, switches 9b, 10b, and 11b, and current sensors 12b, 13b, and 14b. The control circuit 8b includes an operating state determination unit 21b and a control unit 22b. Converter 5b is connected to AC power supply 1b. Since the function of each element of uninterruptible power supply 4b is the same as the function of the corresponding element of uninterruptible power supply 4a, the following detailed description will not be repeated.

  In the configuration shown in FIG. 1, a DC chopper is provided in each uninterruptible power supply. However, a configuration in which the DC chopper is omitted can also be adopted as an embodiment of the present invention.

  When the uninterruptible power supply devices 4a and 4b are both normal, the switches 9a, 9b, 10a, 10b, 11a and 11b are turned on. In each of uninterruptible power supply devices 4a and 4b, a converter converts AC power from an AC power source into DC power. A part of the DC power is supplied to the storage battery 2 to charge the storage battery 2. The current IB indicates the current input to the storage battery.

  The remainder of the DC power generated by the converter is supplied to the inverter. The inverter converts the DC power from the converter into AC power and supplies it to the load 3.

  If any one of the uninterruptible power supply devices 4a and 4b becomes abnormal, the converter stops and the switch (one of the switches 9a and 9b) connecting the converter and the AC power supply is turned off. Below, the case where converter 5a of uninterruptible power supply 4a becomes abnormal is explained typically. The operation of the uninterruptible power supply system 100 when the converter 5b of the uninterruptible power supply 4b becomes abnormal will be described below except that the uninterruptible power supply 4a and the uninterruptible power supply 4b are replaced with each other. The operation is the same.

  FIG. 2 is a first diagram for explaining the operation of uninterruptible power supply system 100 when an abnormality occurs in converter 5a of uninterruptible power supply 4a shown in FIG. Referring to FIG. 2, control unit 22a stops converter 5a when converter 5a is abnormal. Further, the control unit 22a turns off the switch 9a. Thereby, control part 22a makes uninterruptible power supply 4a shift to direct-current operation. The direct current operation is an operation method in which direct current power is supplied from the storage battery 2 to the inverter 6a to continue the operation of the inverter 6a.

  As the inverter 6a continues to operate, the storage battery 2 outputs a current IBx. In other words, the inverter 6 a draws the current IBx from the storage battery 2. On the other hand, the current IB0 is supplied from the DC chopper 7b to the storage battery 2. However, since IB0 <IBx, the voltage of the storage battery 2 decreases from VB. The operating state determination unit 21b of the uninterruptible power supply 4b detects an abnormality of the converter 5a due to a decrease in the voltage of the storage battery 2. Control unit 22b controls converter 5b such that current IB2 increases in response to detection of abnormality of converter 5a by operating state determination unit 21b.

  FIG. 3 is a second diagram for explaining the operation of uninterruptible power supply system 100 when an abnormality occurs in converter 5a of uninterruptible power supply 4a shown in FIG. Referring to FIG. 3, converter 5b increases the DC power output from converter 5b so that the charging current output from DC chopper 7b increases by the same amount as the current drawn by inverter 6a. Therefore, the current IB2 output from the DC chopper 7b increases from IB0 to IB0 + IBx. Thereby, since the discharge of the storage battery 2 does not substantially occur, the voltage of the storage battery 2 is recovered. That is, the voltage of the storage battery 2 turns from a decrease to an increase.

  When the converter 5a is stopped and the battery voltage is recovered even though the storage battery 2 is being discharged, the operating state determination unit 21a is supplying power from the converter 5b to the inverter 6a. judge. In this case, the control unit 22a stops the inverter 6a based on the determination result of the operation state determination unit 21a. Further, the control unit 22a turns off the switches 10a and 11a.

  FIG. 4 is a third diagram for explaining the operation of uninterruptible power supply system 100 when an abnormality has occurred in converter 5a of uninterruptible power supply 4a shown in FIG. Referring to FIG. 4, when inverter 6 a stops, only uninterruptible power supply 4 b supplies power to load 5. The uninterruptible power supply 4b charges the storage battery 2 until the voltage of the storage battery 2 recovers. The uninterruptible power supply 4b bears 100% of the current supplied to the load 3. Therefore, the inverter 6b is configured to have a capacity equal to or greater than the capacity of the load 3. Similarly, the inverter 6a is configured to have a capacity equal to or greater than the capacity of the load 3. The capacity of converters 5a and 5b is determined according to the capacity of inverters 6a and 6b.

  According to the above configuration, an uninterruptible power supply system capable of continuing highly reliable power feeding can be realized. This point will be described based on a comparison with other methods. First, a power feeding method different from the uninterruptible power supply system according to the embodiment of the present invention will be described. In the following, a case where converter 5a of uninterruptible power supply 4a is stopped will be described. In addition, “UPS1 (abnormal number machine)” and “UPS2 (health number machine)” shown in the figure indicate the uninterruptible power supply 4a and the uninterruptible power supply 4b, respectively.

  FIG. 5 is a diagram illustrating a first power feeding method compared with the embodiment of the present invention. Referring to FIG. 5, uninterruptible power supply devices 4a and 4b are normal before time t1. Therefore, AC power from an AC power source is input to each of uninterruptible power supply devices 4a and 4b. This state is indicated as “AC input” in the “UPS operation state” graph. At time t1, converter 5a of uninterruptible power supply 4a stops. Thereby, the DC power from the storage battery 2 is input to the uninterruptible power supply 4a. This state is indicated as “DC input” in the “UPS operating state” graph.

  As shown in the “charging current” graph, the charging current IB0 is supplied from the UPS 2 to the storage battery 2 even after the converter 5a of the UPS 1 is stopped. However, the discharge current IBx of the storage battery 2 is larger than the charging current IB0. Therefore, the battery voltage of the storage battery 2 falls from the rated voltage VB. In addition, in order to show discharge current, minus sign is attached | subjected to IBx.

  At time t2, the battery voltage reaches the end-of-discharge voltage. At this time, the UPS 1 is stopped and the storage battery 2 is disconnected from the UPS 2. As shown in the “load sharing” graph, before time t2, UPS1 and UPS2 bear 50% of the current supplied to the load. After time t2, the UPS 2 is operated independently, so the UPS 2 bears 100% of the current supplied to the load 3.

  According to this method, when the battery voltage of the storage battery 2 reaches the end-of-discharge voltage, the storage battery 2 is disconnected from the healthy machine (uninterruptible power supply 4b). Therefore, the storage battery 2 is not charged after time t2.

  FIG. 6 is a diagram illustrating a second power feeding method compared with the embodiment of the present invention. Referring to FIG. 6, converter 5a of uninterruptible power supply 4a stops at time t1. Thereby, as shown in the graph of “UPS operation state”, the DC power from the storage battery 2 is input to the uninterruptible power supply 4a. Therefore, the battery voltage of the storage battery 2 falls from the rated voltage VB.

  At time t4, the battery voltage reaches the first reference voltage VrefA. Thereby, converter 5b is controlled so that the charging current supplied from UPS 2 (health machine) to storage battery 2 increases. Specifically, the charging current supplied from the UPS 2 (health machine) to the storage battery 2 increases from IB0 to IB0 + IBx. That is, the UPS 2 increases the charging current by the same magnitude as the charging current supplied from the storage battery 2 to the UPS 1 (abnormal machine) in the period from time t1 to time t4.

  By increasing the charging current from the UPS 2, not only the storage battery 2 is not substantially discharged, but also the charging current IB 0 is supplied to the storage battery 2. Therefore, the battery voltage increases after time t4. At time t5, the battery voltage recovers to the rated voltage VB. Further, the current IBx is supplied to the uninterruptible power supply 4a.

  According to this method, as shown in the “UPS operating state” graph, after time t1, DC power is input to UPS1, and AC power is input to UPS2. As a result, the state where 50% of the current supplied to the load is borne by the UPS 1 and the UPS 2 is continued. However, there is a possibility that the stoppage of the converter 5a of the UPS 1 becomes delayed. Further, even if it can be detected that the input of the inverter 6a of the UPS 1 is different from the normal one, it is difficult to determine whether or not the converter 5a is abnormal.

  Furthermore, in preparation for the abnormality of the converter 5a of the UPS1, the converter 5b of the UPS2 (healthy machine) must operate so as to supply more current than usual to the storage battery 2. The same applies to the DC chopper 7b. Therefore, it is necessary to increase the size of converter 5b and DC chopper 7b. Conversely, in order to prepare for the abnormality of the converter 5a of the UPS 2, it is necessary to increase the size of the converter 5a of the UPS 1 and the DC chopper 7a. For this reason, there is a problem that the entire uninterruptible power supply system is enlarged. In addition, if the converter and the DC chopper are enlarged in order to cope with an abnormality, there is a concern that the operation efficiency of the converter and the DC chopper at a normal time is lowered.

  FIG. 7 is a diagram for explaining a power feeding method according to the embodiment of the present invention. Referring to FIG. 7, the operation before time t6 is the same as the operation shown in FIG. In the embodiment of the present invention, the second reference voltage VrefB is set during the recovery of the battery voltage. Note that VrefB> VrefA.

  After time t4, the magnitude of the charging current output from UPS2 (healthy machine) is (IB0 + IBx). That is, converter 5b increases the DC power output from converter 5b. In the period from time t4 to time t6, the UPS 2 supplies the charging current IBx to the UPS 1 instead of discharging the storage battery 2. Since the UPS 1 is stopped after the time t6, the storage battery 2 is supplied with a charging current having a magnitude of (IB0 + IBx) from the UPS 2. As a result, the battery voltage, that is, the DC voltage supplied to the inverter 6a turns from a decrease to an increase.

  At time t6, the battery voltage reaches the second reference voltage VrefB. Thereby, the control circuit 8a of the UPS1 stops the inverter 6a of the UPS1.

  At time t7, the battery voltage reaches the rated voltage VB. Thereby, the control circuit 8b of the UPS 2 switches the charging current supplied to the storage battery 2 from (IB0 + IBx) to IB0. That is, the converter 5b of the UPS 2 decreases the output power and returns the charging current supplied to the storage battery 2 to the level before the battery voltage of the storage battery 2 is lowered.

  According to the embodiment of the present invention, since the battery voltage of the storage battery 2 does not drop to the discharge end voltage, it is not necessary to disconnect the storage battery 2 from the system. For this reason, the storage battery 2 can be charged by a sound uninterruptible power supply.

  Furthermore, the charging current from a healthy uninterruptible power supply increases only in a limited section. That is, the period during which the charging current increases is only from the time when the battery voltage decreases to the first reference voltage VrefA to the time when the battery voltage recovers to the original rated voltage VB. Thus, since the period during which the charging current increases is limited, the increase in charging current can be accommodated without increasing the size of the converter and the DC chopper. Therefore, it is possible to prevent a decrease in efficiency of the uninterruptible power supply system during normal times.

  In addition, according to the embodiment of the present invention, when an abnormality occurs in the converter of a certain uninterruptible power supply, the inverter of the uninterruptible power supply also eventually stops. Therefore, it is possible to detect that an abnormality has occurred in the uninterruptible power supply.

  In the above embodiment, a configuration in which the number of uninterruptible power supply devices is two is shown, but the number of uninterruptible power supply devices may be three or more. In such a configuration, when an abnormality occurs in the converter of one uninterruptible power supply, the charging current IBx shown in FIG. 7 may be borne by the entire other uninterruptible power supply (sound unit). . Therefore, the increase amount of the charging current per one healthy machine can be reduced.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1a, 1b AC power supply, 2 storage battery, 3 load, 4a, 4b uninterruptible power supply, 5a, 5b converter, 6a, 6b inverter, 7a, 7b DC chopper, 8a, 8b control circuit, 9a, 10a, 11a, 9b, 10b, 11b switch, 12a, 13a, 14a, 12b, 13b, 14b Current sensor, 21a, 21b Operation state determination unit, 22a, 22b control unit, 100 Uninterruptible power supply system.

Claims (4)

A plurality of uninterruptible power supplies provided in parallel to the load;
A common storage battery for the plurality of uninterruptible power supply units, and a storage battery for charging and discharging DC power,
Each of the plurality of uninterruptible power supplies is
A converter in which AC power from an AC power source is converted into DC power, and a DC side is electrically connected to the storage battery;
An inverter that receives DC power from at least one of the converter and the storage battery, and converts the DC power into AC power supplied to the load;
A control circuit that monitors the operating state of the converter and controls the converter and the inverter based on a monitoring result;
The control circuit increases the output voltage of the converter to increase the DC voltage when the DC voltage of the storage battery decreases despite the converter being normal,
When the converter is stopped and the DC voltage decreases, the control circuit switches the inverter in response to the first reference voltage being reached after the DC voltage has changed from a decrease to an increase. Uninterruptible power supply system to be stopped. The uninterruptible power supply system according to claim 1, wherein the control circuit increases the output power of the converter when the DC voltage drops below a second reference voltage even though the converter is normal. . When the DC voltage is lower than the second reference voltage even though the converter is normal, the control circuit outputs the output of the converter when the DC voltage is restored to the rated voltage. The uninterruptible power supply system according to claim 2, wherein the electric power is reduced to return the charging current to the storage battery to a level before the DC voltage is lowered. Before Stories second reference voltage is lower than said first reference voltage, the uninterruptible power supply system according to claim 2 or claim 3.

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