Uninterruptible Power Supply System

Abstract

To provide an uninterruptible power supply device system capable of being operated by the number of uninterruptible power supply devices that minimize total power loss of a system.SOLUTION: An uninterruptible power supply device includes: a plurality of uninterruptible power supply devices 1-1 to 1-3 that are connected in parallel to a load 3, supply power to the load, and being composed of N normal devices and M spare devices; a control unit 15 for controlling operation / stop of the plurality of uninterruptible power supply devices; and a storage battery 4 connected to the plurality of uninterruptible power supply devices. The uninterruptible power supply includes converters 11-1 to 11-3 for converting AC power of an AC power supply into DC power and inverters 12-1 to 12-3 for converting the DC power converted by the converters or DC power from the storage battery into AC power to supply it to the load, supplies power required by the load by the number of operating units that is a total of the normal device and the spare device that are actually operated, varies the number of the regular units that are actually operated by at least one or more, and performs operation by the number of operating units that becomes the smallest total power loss.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to uninterruptible power supply systems. [Background technology]

[0002] BACKGROUND ART In an uninterruptible power supply system, a method is known in which a plurality of uninterruptible power supplies are connected in parallel to operate in a redundant manner in order to improve the reliability of the system (Patent Document 1).

[0003] Fig. 6 is a schematic configuration diagram of an uninterruptible power supply system described in Patent Document 1. In Fig. 6, a plurality of uninterruptible power supplies (UPS) 1-1 to 1-3 are connected in parallel, an AC power supply 2 is connected to the input side, and a load 3 is connected to the output side.

[0004] The multiple uninterruptible power supplies 1-1 to 1-3 are composed of converters 11-1 to 11-3 that convert AC from an AC power supply 2 into DC, and inverters 12-1 to 12-3 that convert the DC converted by the converters 11-1 to 11-3 into AC and supply the converted AC to a load 3.

[0005] In Patent Document 1, as shown in the flowchart in Fig. 7, if the total amount of electric power is greater than the first rated total amount of electric power (YES in step S52), the inverters are started (step S53). If the total amount of electric power is less than the first rated total amount of electric power (NO in step S52), it is determined whether the second rated total amount of electric power is greater than the total amount of electric power (step S54).

[0006] If the second rated total power amount is greater than the total power amount (YES in step S54), the inverter is stopped (step S55). In this way, the operation of the uninterruptible power supply is controlled according to the flowchart shown in Fig. 7, thereby saving energy in the entire system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5732134 Summary of the Invention [Problem to be solved by the invention]

[0008] However, depending on the efficiency curve of the uninterruptible power supply against the load rate, there are conditions under which operating three uninterruptible power supplies will result in higher system efficiency than operating two uninterruptible power supplies, depending on the load conditions.

[0009] There are efficiency curves in which the efficiency increases as the load factor increases, as shown in Figure 8(a), and efficiency curves in which the efficiency is maximized at a certain load factor, as shown in Figure 8(b). In the case of the efficiency curve shown in Figure 8(b), system efficiency is higher when three uninterruptible power supplies are operated than when two are operated.

[0010] An object of the present invention is to provide an uninterruptible power supply system that can be operated with the number of uninterruptible power supplies that minimizes the total power loss of the system. [Means for solving the problem]

[0011] In order to solve the above problems, the uninterruptible power supply system of the present invention comprises a plurality of uninterruptible power supplies connected in parallel to a load and supplying power to the load, the uninterruptible power supply comprising N regular units and M spare units, a control unit that controls the operation and stop of the plurality of uninterruptible power supplies, and storage batteries connected to the plurality of uninterruptible power supplies, the uninterruptible power supplies each comprising a converter that converts AC power from an AC power source into DC power, and an inverter that converts the DC power converted by the converter or the DC power from the storage battery into AC power and supplies it to the load, and is characterized in that the power required by the load is supplied by the number of operating units, which is the sum of the regular units and spare units that are actually operating, and the number of regular units that are actually operating can be varied by at least one unit or more, and operation is carried out with the number of operating units that results in the smallest total power loss. [Effects of the Invention]

[0012] According to the present invention, power is supplied by the number of operating units, which is the sum of the regular and spare units, and the number of regular units actually operating is varied by at least one unit, so that the system operates with the number of operating units that results in the smallest total power loss. Therefore, the system can be operated with the number of uninterruptible power supplies that results in the smallest total power loss. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a configuration block diagram of an uninterruptible power supply system according to a first embodiment of the present invention. [Figure 2] 5 is a flowchart showing processing by a control unit of the uninterruptible power supply system according to the first embodiment of the present invention. [Figure 3] FIG. 6 is a configuration block diagram of an uninterruptible power supply system according to a second embodiment of the present invention. [Figure 4] 10 is a flowchart showing processing by a control unit of an uninterruptible power supply system according to a second embodiment of the present invention. [Figure 5] 10 is a flowchart showing processing by a control unit of an uninterruptible power supply system according to a third embodiment of the present invention. [Figure 6] FIG. 1 is a diagram illustrating a configuration of a conventional uninterruptible power supply system. [Figure 7] 7 is a flowchart showing operation control of the uninterruptible power supply in the uninterruptible power supply system shown in FIG. 6. [Figure 8] FIG. 2 is a diagram showing two examples of efficiency curves relative to the load factor of an uninterruptible power supply. DETAILED DESCRIPTION OF THE INVENTION

[0014] An uninterruptible power supply according to an embodiment of the present invention will now be described in detail with reference to the drawings.

[0015] (First embodiment) Fig. 1 is a configuration block diagram of an uninterruptible power supply system according to a first embodiment of the present invention. The uninterruptible power supply system shown in Fig. 1 includes a plurality of uninterruptible power supply devices 1-1 to 1-3, a control unit 15, and a storage battery 4. The number of the plurality of uninterruptible power supply devices is not limited to three, and may be four or more.

[0016] The plurality of uninterruptible power supplies 1-1 to 1-3 are connected in parallel and supply power to a load 3. A control unit 15 controls the operation and stop of the plurality of uninterruptible power supplies 1-1 to 1-3 based on measurement information from the plurality of uninterruptible power supplies 1-1 to 1-3. A storage battery 4 is connected to the plurality of uninterruptible power supplies 1-1 to 1-3.

[0017] The multiple uninterruptible power supplies 1-1 to 1-3 are equipped with converters 11-1 to 11-3 that convert AC power from an AC power source 2 into DC power, and inverters 12-1 to 12-3 that convert the DC power converted by the converters 11-1 to 11-3 or the DC power from a storage battery 4 into AC power and supply it to a load 3.

[0018] The multiple uninterruptible power supplies 1-1 to 1-3 supply the power required by the load with the number of operating units, which is the sum of the regular units N that are actually operating and the spare units M, and the number of regular units that are actually operating can be varied by at least one unit, and are operated with the number of operating units that results in the smallest total power loss. However, in general, the spare units M are often fixed at one or two units.

[0019] The control unit 15 stores a table of the efficiency curve of the uninterruptible power supply (conversion efficiency representing efficiency relative to load factor), calculates the total power loss of the system based on the conversion efficiency, power supply power, and power consumption, and controls the operation of the uninterruptible power supply based on the total power loss. To this end, the control unit 15 includes a memory 21, a total power loss calculation unit 22, a total power loss comparison unit 23, and an operating unit number control unit 24. The memory 21 stores the conversion efficiency representing efficiency relative to the load factor as shown in Figure 8(b).

[0020] The total power loss calculation unit 22 reads out the conversion efficiency stored in the memory 21, and calculates the total power loss of the system when a plurality of uninterruptible power supplies, consisting of N regular units and M spare units, with L units planned to be in operation, supply power to the load 3, based on this conversion efficiency, the power supply power per uninterruptible power supply unit, and the power consumption per unit.

[0021] The total power loss comparison unit 23 compares the first total power loss calculated by the total power loss calculation unit 22 when power is supplied to L units planned to operate, with the second total power loss when power is supplied when one of the L units planned to operate is stopped and the number of units planned to operate is set to L-1.

[0022] When the first total power loss is higher than the second total power loss, the operating unit number control unit 24 subtracts one from the number of units scheduled to be in operation and calculates the total power loss in the total power loss calculation unit 22, determines the number of units to be in operation K when the first total power loss is lower than the second total power loss, and operates or stops the multiple uninterruptible power supplies 1-1 to 1-3 so that the determined number of operating units K is reached.

[0023] Next, the processing of the control unit 15 of the uninterruptible power supply system according to the first embodiment configured as described above will be described in detail with reference to the flowchart shown in FIG.

[0024] In this example, in an uninterruptible power supply system consisting of three or more uninterruptible power supplies, if the condition that inverter power supply is possible even if one of the load power supplies stops is met, the following processing is performed. The following example illustrates an uninterruptible power supply system consisting of multiple uninterruptible power supplies.

[0025] First, a predetermined number of uninterruptible power supplies are started (step S11). At this time, if the load capacity is unknown, the maximum number of units is started. Next, the control unit 15 calculates the actual system capacity according to the following calculation formula (1). In the following explanation, it is assumed that there are M spare units.

[0026] Actual system capacity = system capacity x (number of operating units - spare units M) / (number of regular uninterruptible power supplies) System capacity = Uninterruptible power supply capacity x number of regular uninterruptible power supplies ... (1) That is, the control unit 15 calculates: actual system capacity=uninterruptible power supply capacity×(number of operating units−standby units M) (step S12).

[0027] The control unit 15 determines whether the actual system capacity is greater than the actual load capacity (step S13). If the actual system capacity is greater than the actual load capacity (YES in step S13), the total power loss calculation unit 22 calculates the total power loss of the system when a plurality of uninterruptible power supplies, consisting of N regular units and M spare units, L units planned to be in operation, supply power to the load 3, based on the conversion efficiency, the power supply power per uninterruptible power supply unit, and the power consumption per unit read from the memory 21 (step S14).

[0028] Specifically, the total power loss calculation unit 22 calculates the power supply amount per uninterruptible power supply unit using the following formula (2).

[0029] When powering two units, the power supply per unit is Pout2=Pload / 2 When powering with (L-1) units, power supply per unit Pout L-1 =Pload / (L-1) When powering L units, the power supply per unit is Pout L =Pload / L …(2) where Pload is the load power.

[0030] Next, the total power loss calculation unit 22 calculates the power consumption per uninterruptible power supply unit using the following calculation formula (3).

[0031] When powering two units, power consumption per unit Ploss2=((1 / η)-1)×Pout2 When powered by (L-1) units, power consumption per unit Ploss (L-1) =((1 / η)-1)×Pout (L-1) When powering L units, power consumption per unit Ploss L =((1 / η)-1)×Pout L …(3) Here, η is the conversion efficiency at Pout that is previously measured information and stored in the memory 21.

[0032] Next, the total power loss calculation unit 22 calculates the total power loss of the system using the following equation (4).

[0033] Total power loss of the system when powered by two units Plossall2=Ploss2×2 Total power loss of the system when power is supplied from (L-1) units Plossall (L-1) =Ploss (L-1) ×(L-1) Total power loss of the system when power is supplied from L units Plossall L =Ploss L ×L …(4)

[0034] Next, total power loss comparison unit 23 compares the total power loss when powering L units with the total power loss when powering (L-1) units, calculated by total power loss calculation unit 22 (step S15). If the total power loss when powering L units is smaller than the total power loss when powering (L-1) units (YES in step S15), multiple uninterruptible power supplies are determined to be the number K of operating units (step S17).

[0035] On the other hand, if the total power loss when powering L units is greater than the total power loss when powering (L-1) units, it is possible that the total power loss can be reduced by reducing the number of operating units. Therefore, if the answer is NO in step S15, the planned number of operating units, L, is reduced by one (step S16), and again in steps S14 and S15, the total power loss when powering L units is compared with the total power loss when powering (L-1) units. Steps S14, S15, and S16 are repeated until the total power loss when powering L units becomes smaller than the total power loss when powering (L-1) units, or until the number of operating regular units is reduced to one, and the number of operating units, K, is determined.

[0036] In this way, the operating unit number control unit 24 determines the number of operating units K to be L units when the total power loss when powering L units becomes smaller than the total power loss when powering (L-1) units (step S17), and operates or stops multiple uninterruptible power supplies so that the determined number of operating units K is achieved (step S18).

[0037] Therefore, the system can be operated with the number of uninterruptible power supplies that minimizes the total power loss, thereby improving the efficiency of the system.

[0038] If it is determined in step S13 that the actual system capacity is smaller than the actual load capacity, all the uninterruptible power supplies are operated (step S19).

[0039] In the first embodiment, when stopping a plurality of uninterruptible power supplies 1-1 to 1-3, control unit 15 stops converters 11-1 to 11-3 and inverters 12-1 to 12-3, but it may also stop only inverters 12-1 to 12-3, for example.

[0040] (Second embodiment) Fig. 3 is a configuration block diagram of an uninterruptible power supply system according to a second embodiment of the present invention. In the uninterruptible power supply system according to the second embodiment, a control unit 15a shown in Fig. 3 is different from the control unit 15 shown in Fig. 1 in that it further includes a counter 25 and a time determination unit 26.

[0041] Once the number K of operating uninterruptible power supplies has been determined, counter 25 counts time. Time determination unit 26 determines whether the time counted by counter 25 has exceeded a designated time, and if the counted time has exceeded the designated time, causes total power loss calculation unit 22 to calculate the total loss.

[0042] Next, the processing of the control unit 15a of the uninterruptible power supply system according to the second embodiment configured as above will be described in detail with reference to the flowchart shown in FIG.

[0043] The processing in steps S12 to S18 is the same as the processing in steps S12 to S18 shown in FIG. 2, so only the processing in steps S21 to S24 will be described here.

[0044] First, a predetermined number of uninterruptible power supplies are started (step S21). Next, the control unit 15a determines whether the power supply of the K operating uninterruptible power supplies is sufficient to supply power to the current load (step S22).

[0045] If the power supply power of the K operating uninterruptible power supplies can supply power to the current load (YES in step S22), the counter 25 counts the time (step S23).

[0046] Next, the time determination unit 26 determines whether the time counted by the counter 25 has exceeded the designated time (step S24). If the counted time has exceeded the designated time (YES in step S24), the process proceeds to step S12. That is, the total power loss calculation unit 22 calculates the total power loss.

[0047] If the counted time does not exceed the specified time (NO in step S24), the process returns to step S21. Also, if the power supply power of the K operating uninterruptible power supplies is not enough to supply power to the current load in step S22 (NO in step S22), all uninterruptible power supplies are operated (step S25).

[0048] As described above, the uninterruptible power supply system according to the second embodiment calculates the actual system capacity in step S12 and the total power loss of the system in step S14 at each specified time, so that the system can be operated with the number of uninterruptible power supplies that minimizes the total power loss of the system depending on the current load state, thereby improving the efficiency of the system.

[0049] (Third embodiment) Fig. 5 is a flowchart showing the processing of a control unit of an uninterruptible power supply system according to a third embodiment of the present invention. The uninterruptible power supply system according to the third embodiment differs from the flowchart of the uninterruptible power supply system according to the second embodiment shown in Fig. 4 in that the processing of step S26 is added between step S22 and step S23.

[0050] Here, only the processing of step S26 will be explained. The load power at the current time is compared with the load power a predetermined time before the current time, for example, one second before (step S26). If the load power at the current time and the load power one second before the current time are the same value (YES in step S26), the processing proceeds to step S23.

[0051] On the other hand, if the load power at the current time and the load power one second before the current time are not the same value (NO in step S26), the process returns to step S21.

[0052] As described above, according to the uninterruptible power supply system of the third embodiment, if the load power at the current time and the load power one second prior to the current time are not the same value, and if the load power changes due to a sudden change in load, the number of operating uninterruptible power supplies can be appropriately changed. As long as it is possible to detect a change in the load power one second prior, the time may be changed arbitrarily depending on the conditions of use.

[0053] The present invention is not limited to the uninterruptible power supply systems according to the first to third embodiments. In the uninterruptible power supply systems according to the first to third embodiments, the control units 15, 15a calculate the operating time of each uninterruptible power supply and assign the uninterruptible power supply with the longest operating time the first priority in the order of candidates for shutdown. In Figures 2, 4, and 5, when the conditions for shutting down the uninterruptible power supplies are met, the uninterruptible power supply with the longest operating time may be shut down. [Explanation of symbols]

[0054] 1-1~1-3 Uninterruptible power supply (UPS) 2 AC power supply 3. Load 4. Storage battery 11-1~11-3 Converter 12-1~12-3 Inverter 21 Memory 22 Total power loss calculation section 23 Total power loss comparison section 24 Operating vehicle number control unit 25 Counter 26 Time determination section

Claims

1. a plurality of uninterruptible power supplies connected in parallel to a load to supply power to the load; a control unit that controls operation and shutdown of the plurality of uninterruptible power supplies; a storage battery connected to the plurality of uninterruptible power supply devices; Equipped with Each of the plurality of uninterruptible power supplies a converter that converts AC power from an AC power source into DC power; an inverter that converts the DC power converted by the converter or the DC power from the storage battery into AC power and supplies the AC power to the load; Equipped with The control unit controls the number of the plurality of uninterruptible power supply devices to be operated to be at least one or more, based on the total power loss, and controls the number of devices to be operated so as to result in the smallest total power loss. Uninterruptible Power Supply Systems.

2. a plurality of uninterruptible power supplies connected in parallel to a load to supply power to the load; a control unit that controls operation and shutdown of the plurality of uninterruptible power supplies; a storage battery connected to the plurality of uninterruptible power supply devices; Equipped with Each of the plurality of uninterruptible power supplies a converter that converts AC power from an AC power source into DC power; an inverter that converts the DC power converted by the converter or the DC power from the storage battery into AC power and supplies the AC power to the load; Equipped with The control unit a total power loss calculation unit that calculates a total power loss of the system when the plurality of uninterruptible power supplies, the number of which is L and is planned to be in operation, supplies power to the load based on a conversion efficiency that indicates efficiency with respect to a load factor; a first total power loss when power is supplied to the L number of units scheduled to operate, calculated by the total power loss calculation unit; and a total power loss comparison unit that compares the second total power loss during power supply when one of the L number of scheduled operating units is stopped and the number of scheduled operating units is set to L-1; an operating unit number control unit that operates or stops the plurality of uninterruptible power supply devices so that the determined number of operating units K is reached; and Equipped with The control unit controls the number of the plurality of uninterruptible power supply devices to be operated to be at least one or more, based on the total power loss, and controls the number of devices to be operated so as to result in the smallest total power loss. Uninterruptible Power Supply Systems.

3. The total power loss calculation unit calculates the total power loss of the system when power is supplied to the load with the number of units L planned to be in operation, based on the power supply power per unit, the power consumption per unit, and the conversion efficiency.

3. The uninterruptible power supply system of claim 2.

4. The control unit Once the number of operating units (K) is determined, a counter that counts the time is set. a time determination unit that determines whether the time counted by the counter has exceeded a designated time, and, if the counted time has exceeded the designated time, causes the total power loss calculation unit to calculate a total loss; 4. The uninterruptible power supply system according to claim 2, further comprising:

5. The control unit compares a first load power at a current time with a second load power at a predetermined time before the current time, and when the first load power and the second load power have the same value, causes the counter to count time.

5. The uninterruptible power supply system of claim 4.

6. The control unit stops only the inverter when stopping the plurality of uninterruptible power supply devices.

2. The uninterruptible power supply system of claim 1.

7. A plurality of uninterruptible power supplies connected in parallel to a load and supplying power to the load; a control unit that controls operation and shutdown of the plurality of uninterruptible power supplies; a storage battery connected to the plurality of uninterruptible power supply devices; Equipped with Each of the plurality of uninterruptible power supplies a converter that converts AC power from an AC power source into DC power; an inverter that converts the DC power converted by the converter or the DC power from the storage battery into AC power and supplies the AC power to the load; Equipped with The control unit The number of the plurality of uninterruptible power supply units in operation is varied based on the total power loss to at least one unit, and the number of units that results in the smallest total power loss is operated; When the plurality of uninterruptible power supply devices are to be stopped, control is performed so that only the inverter is stopped. Uninterruptible Power Supply Systems.

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