JP2006149115A - Control method of uninterruptible power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method for supplying a stable voltage to a load of an uninterruptible power supply system.
An uninterruptible power supply system includes an uninterruptible power supply device 10a, 20a, a changeover switch circuit 41, a CT 61 for detecting a current to a load 60, and the like. Are connected in series, the secondary current of the auxiliary CT 17 is input to the uninterruptible power supply 10a as a load current command value (i _L ^* ), and the shunt resistor 26 and the auxiliary CT 27 are connected in series to the secondary winding, When the secondary current of the auxiliary CT 27 is input to the uninterruptible power supply 20a as the load current command value (i _L ^* ), the operation to switch the power supply to the load 60 from the UPS power supply bus 30 to the power system 50 is performed. In addition, the currents of the UPS power supply bus 30 and the power system bus 50 are assigned to change into a first-order lag waveform, and the collapse of the voltage across the load 60 is eliminated.
[Selection] Figure 1

Description

  The present invention is connected to a plurality of uninterruptible power supply units (UPS) that can be operated in parallel, a UPS power supply bus connected in parallel to the output side of each of the uninterruptible power supply units, and an external AC power source such as a commercial power source. The present invention relates to a control method for an uninterruptible power supply system formed from a power system bus and a changeover switch circuit that switches power supply to a load to a UPS power supply bus or a power system bus.

  FIG. 5 is a circuit configuration showing a conventional example of this type of uninterruptible power supply system. In this figure, reference numeral 10 denotes an uninterruptible power supply (UPS1) comprising a rectifier circuit, a storage battery, an inverse conversion circuit, and a control circuit for controlling them. ), A peripheral circuit of the uninterruptible power supply 10 includes a CT (current transformer) 11 for detecting the output current of the uninterruptible power supply 10, a shunt resistor 12, an auxiliary CT 13, and an auxiliary switch 14, and 20 is nothing. An uninterruptible power supply (UPS2) having the same configuration as that of the uninterruptible power supply 10, and as a peripheral circuit of the uninterruptible power supply 20, a CT21 for detecting the output current of the uninterruptible power supply 20, a shunt resistor 22, an auxiliary CT23, and an auxiliary switch 24 30 is a UPS power supply bus, 31 and 32 are switches, 40 is a thyristor switch (thyristor SW) 71 and 73, circuit breakers 72 and 74, etc. Changeover switch circuit comprising, 50 power system bus connected to an external AC power supply such as a commercial power supply (not shown), 60 is the load of the UPS system.

  When the uninterruptible power supply system shown in FIG. 5 is in a normal state, from the uninterruptible power supply apparatuses 10 and 20 that are operating in parallel while generating a constant voltage AC voltage that is phase-synchronized with the AC voltage of the external AC power supply, respectively. Switches 31 and 32, UPS power supply bus 30, and thyristors SW71 and 73 that are closed when the uninterruptible power supply devices 10 and 20 are in an operating state, the circuit breaker 72 is closed, and the circuit breaker 74 is Power is supplied to the load 60 via the changeover switch circuit 40 in the open circuit state.

In this normal state, the auxiliary switches 14 and 24 are also closed in conjunction with the switches 31 and 32. At this time, the uninterruptible power supply 10 obtains the uninterruptible power supply through the shunt resistor 12 and the auxiliary CT13. The current control calculation based on the detected value (i _O ), which is the secondary current of CT11, is performed so that the output current corresponds to the output current command value (i _O ^* ) of 10. Similarly, in the uninterruptible power supply 20, the secondary current of the CT 21 is set so that the output current corresponds to the output current command value (i _O ^* ) of the uninterruptible power supply 20 obtained through the shunt resistor 22 and the auxiliary CT 23. A current control calculation based on a detected value (i _O ) that is a current is performed. That is, in this state, since the auxiliary switches 14 and 24 are closed, the secondary currents of the auxiliary CTs 13 and 23 include components that suppress the cross current between the uninterruptible power supply devices 10 and 20, respectively. Therefore, the two uninterruptible power supply devices 10 and the uninterruptible power supply device 20 as the plurality of units are operated in parallel, and the current to the load 60 is also shared.
JP 2002-27684 A (Page 2, Fig. 1)

  In the conventional uninterruptible power supply system shown in FIG. 5, in order to maintain the operational reliability of the uninterruptible power supply system, it is common to regularly perform maintenance and inspection work for the uninterruptible power supply devices 10 and 20. However, in this case, an operation for switching the power supply to the load 60 from the UPS power supply bus 30 to the power system 50 is necessary.

  In order to perform this switching operation, first, the circuit breaker 72 in the closed state is opened while the thyristor SW71 in the changeover switch circuit 40 is turned on. After the circuit breaker 72 is opened, the circuit breaker 72 is turned on while the thyristor SW73 is turned on. The circuit 74 is closed from the open circuit, the thyristor SW 71 is turned off, the circuit breaker 74 is closed, and then the thyristor SW 73 is turned off.

  FIG. 6 is an operation waveform diagram when the power supply to the load 60 is switched from the UPS power supply bus 30 to the power system 50. In this figure, the current from the UPS power supply bus 30 indicates that the thyristor SW71 is switched from the on state to the off state. At the changed timing, it becomes zero almost instantly (specifically, within a half cycle of the voltage across the load 60) and switches to the current from the power system bus 50. At this time, as shown in FIG. There is a depression in the voltage. The depression of the voltage is caused by the sudden change in the load of the power system 50 with the start of power supply from the power system bus 50.

  6 is also generated when the power supply to the load 60 is switched from the power system bus 50 to the UPS power supply bus 30 (not shown). This is an undesirable phenomenon.

  An object of the present invention is to provide a control method for an uninterruptible power supply system that eliminates a voltage depression when power supply to a load is switched to a UPS power supply bus or a power system bus.

The first invention includes a plurality of uninterruptible power supplies (UPS) capable of operating in parallel, a UPS power supply bus connected in parallel to the output side of each of the uninterruptible power supplies, and an external AC power supply such as a commercial power supply. In an uninterruptible power supply system formed from a power system bus connected to the power supply and a changeover switch circuit that switches power supply to a load to a UPS power supply bus or a power system bus,
When switching the power supply to the load from the UPS power supply bus to the power system bus, or when switching from the power system bus to the UPS power supply bus, the load is supplied in parallel from both the buses to the load for a predetermined period. Control method.

The second invention is the control method of the uninterruptible power supply system of the first invention,
In the parallel power feeding period, control is performed such that the current from the UPS power feeding bus gradually increases or decreases.

  According to the present invention, when the power supply to the load is switched to the UPS power supply bus or the power system bus, the load is controlled so that the load can be supplied in parallel to the load from both the buses for a predetermined period. By causing the current to increase or decrease smoothly, the collapse of the voltage across the load can be almost eliminated.

  FIG. 1 is a circuit configuration diagram of an uninterruptible power supply system showing a first embodiment of the present invention. In this figure, components having the same functions as those of the conventional configuration shown in FIG. The description thereof is omitted here.

  That is, in the uninterruptible power supply system shown in FIG. 1, the uninterruptible power supply 10a is obtained by adding the functions described later to the uninterruptible power supply 10 described above, and the uninterruptible power supply 20 is also an uninterruptible power supply 20a. In the changeover switch circuit 41, the thyristor SW71 in the changeover switch circuit 40 described above is omitted, and a CT61 is inserted in the path from the changeover switch circuit 41 to the load 60. The contact of the auxiliary switch 62 is connected to the secondary side of the CT61. One end is connected.

Further, the other end of the contact of the auxiliary switch 62 is connected to one end of each contact of the auxiliary switch 15, 25 linked to the auxiliary switch 14, 24. The other end of the contact of the auxiliary switch 15 is connected to the shunt resistor 16. CT17 is connected in series, and the secondary current of the auxiliary CT17 is input to the uninterruptible power supply 10a as a load current command value (i _L ^* ). Similarly, a shunt resistor 26 and an auxiliary CT 27 are connected in series to the other end of the contact of the auxiliary switch 25, and the secondary current of the auxiliary CT 27 is input to the uninterruptible power supply 20a as a load current command value (i _L ^* ). .

  Here, when the uninterruptible power supply 10a and the uninterruptible power supply 20a are manufactured with the same specifications, the shunt resistor 12 and shunt resistor 22, the auxiliary CT12 and auxiliary CT22, the shunt resistor 16 and shunt resistor 26, and the auxiliary CT17 and auxiliary. Each CT27 is manufactured with the same specifications.

  When the uninterruptible power supply system shown in FIG. 1 is in a normal state, each of the uninterruptible power supply apparatuses 10a and 20a operating in parallel while generating a constant voltage AC voltage that is phase-synchronized with the AC voltage of the external AC power supply, respectively. Switches 31 and 32, UPS power supply bus 30, and circuit breaker 72 are closed, thyristor SW73 is off, and circuit breaker 74 is open. Power is supplied to the load 60 via the changeover switch circuit 41 in FIG.

In this normal state, the auxiliary switches 14 and 24 are also closed in conjunction with the switches 31 and 32. At this time, the uninterruptible power supply 10a obtains the uninterruptible power supply through the shunt resistor 12 and the auxiliary CT13. Current control calculation based on the detected value (i _O ), which is the secondary current of CT11, is performed so that the output current corresponds to the output current command value (i _O ^* ) of 10a. Similarly, in the uninterruptible power supply 20a, the secondary of the CT21 is set so that the output current corresponds to the output current command value (i _O ^* ) of the uninterruptible power supply 20a obtained through the shunt resistor 22 and the auxiliary CT23. A current control calculation based on a detected value (i _O ) that is a current is performed. Therefore, in this state, since the auxiliary switches 14 and 24 are closed, the secondary currents of the auxiliary CTs 13 and 23 include components that suppress the cross current between the uninterruptible power supply devices 10a and 20a, respectively. Accordingly, the two uninterruptible power supply devices 10a and the uninterruptible power supply device 20a as the plurality of units are operated in parallel, and the current to the load 60 is also shared.

  Also in the uninterruptible power supply system shown in FIG. 1, in order to maintain the operational reliability of the uninterruptible power supply system, it is common to regularly perform maintenance and inspection work for the uninterruptible power supply devices 10a, 20a, etc. In this case, an operation for switching the power supply to the load 60 from the UPS power supply bus 30 to the power system 50 is necessary.

  For this switching operation, first, when the circuit breaker 72 in the changeover switch circuit 41 is in the closed state, the circuit breaker 74 is closed from the open state, and after that, about 5 to 10 cycles of the voltage across the load 60 have elapsed. The circuit breaker 72 is opened.

  In the uninterruptible power supply system shown in FIG. 1, the auxiliary switch 62 is in a closed state when power is supplied to the load 60 from the UPS power supply bus 30, that is, the uninterruptible power supplies 10 a and 20 a, and then the load 60 As an operation state when the power supply to the UPS power supply bus 30 is switched from the power supply bus 30 to the power system bus 50, the circuit breaker 72 in the changeover switch circuit 41 is in the closed state, the water switch SW73 is turned on, or the circuit breaker 74 is closed. When the power is temporarily supplied in parallel to the load 60, the auxiliary switch 62 is opened.

  In addition, as an operation state when the power supply to the load 60 is switched from the power system bus 50 to the UPS power supply bus 30, when the circuit breaker 74 in the changeover switch circuit 41 is in a closed state, the circuit breaker 74 is closed, When the parallel power is temporarily supplied from the bus to the load 60, the auxiliary switch 62 is closed.

  FIG. 2 is a detailed circuit configuration diagram of the current calculation unit 80 as a function added to the control circuit of the uninterruptible power supply 10a. Reference numerals 81, 84, and 85 denote addition calculators, 82 denotes an auxiliary switch, and 83 denotes a first-order lag filter. It is. The auxiliary switch 82 is closed only during a period in which both the circuit breaker 72 and the circuit breaker 74 in the changeover switch circuit 41 are closed for the switching operation.

  In the uninterruptible power supply system shown in FIG. 1, the power supply 50 is supplied from the UPS power supply bus 30 to the load 60 while referring to the circuit configuration diagram shown in FIG. 2 and the waveform diagram shown in FIG. The operation when switching to is described.

First, since the auxiliary switch 82 in the current calculation unit 80 is in the open state in the normal state described above, the output of the first-order lag filter 83 is zero, and therefore, as the shared current command value that is the output of the addition calculator 84. The output current command value (i _O ^* ) appears. As a result, the adder 85 performs a deviation calculation between the output current command value (i _O ^* ) and the detected value (i _O ), and a current regulator (not shown) performs an adjustment calculation for reducing the deviation to zero. Yes.

Next, when the operation of switching the power supply to the load 60 from the UPS power supply bus 30 to the power system 50 is performed and both the circuit breaker 72 and the circuit breaker 74 in the changeover switch circuit 41 are closed, the auxiliary switch 62 Is closed to open, and the auxiliary switch 82 is opened to closed so that the first-order lag filter 83 is input with a value opposite in polarity to the output current command value (i _O ^* ). The envelope increases in the form of a first order lag wave with a value of reverse polarity. Therefore, the shared current command value has the same polarity as the output current command value, and its envelope is reduced to a first-order lag waveform, and eventually becomes zero.

  FIG. 3 shows a state in which the currents of the UPS power supply bus 30 and the power system bus 50 at this time share the voltage of both ends of the load 60 for about five cycles while changing to the shape of the first-order lag waveform. No voltage depression occurs in the voltage across the load 60.

Further, when an operation of switching the power supply to the load 60 from the power system bus 50 to the UPS power supply bus 30 is performed and both the circuit breaker 72 and the circuit breaker 74 in the changeover switch circuit 41 are closed, the auxiliary switch 62 , 82 are opened to closed, the shared current command value has the same polarity as the output current command value, and its envelope increases to a first-order lag waveform, and eventually the same value as the output current command value ( _io ^* ). It becomes.

  As is clear from the circuit configuration of the uninterruptible power supply system shown in FIG. 1, the changeover switch circuit 41 can omit the thyristor SW71 as compared with the conventional changeover switch circuit 40. I can measure down.

  FIG. 4 is a circuit configuration diagram of an uninterruptible power supply system showing a second embodiment of the present invention. In this figure, components having the same functions as those in the circuit configuration shown in FIG. The description is omitted here.

  That is, the uninterruptible power supply system shown in FIG. 4 differs from the uninterruptible power supply system shown in FIG. 1 in that the load is a plurality of loads 63 (load 1) and loads 64 (load 2). 35, switches 36 and 37, changeover switch circuit 42, CT65, and auxiliary switches 18, 19, 28, 29 and 66 are additionally provided.

  Here, the switches 18 and 19 operate in conjunction with the switch 36 that is closed when the uninterruptible power supply 10a is in an operating state. Similarly, the switch 18 and 19 are closed when the uninterruptible power supply 20a is in an operating state. The switches 28 and 29 operate in conjunction with the switch 37.

  Therefore, this uninterruptible power supply system can be operated only by either the load 1 or the load 2, and the operation at this time is the same as the uninterruptible power supply system shown in FIG.

  When power is supplied to the load 1 and the load 2, an operation for switching the power supply to the load 63 from the UPS power supply bus 30 to the power system 50 and a power supply to the load 64 are switched from the UPS power supply bus 35 to the power system 51. If the operation is performed at the same time, even in this uninterruptible power supply system, no voltage collapse occurs in the voltage across the loads 63 and 64 during the switching operation.

The circuit block diagram of the uninterruptible power supply system which shows 1st Embodiment of this invention Partial detailed circuit configuration diagram of FIG. Waveform diagram explaining the operation of FIG. The circuit block diagram of the uninterruptible power supply system which shows 2nd Embodiment of this invention Circuit diagram of uninterruptible power supply system showing conventional example Waveform diagram explaining the operation of FIG.

Explanation of symbols

10, 10a, 20, 20a ... uninterruptible power supply, 11, 21 ... CT, 12, 22 ... shunt resistance, 13, 23 ... auxiliary CT, 14, 24 ... auxiliary switch, 15, 25 ... auxiliary switch, 16, 26 ... Shunt resistance, 17, 27 ... Auxiliary CT, 18, 19, 28, 29 ... Auxiliary switch, 30, 35 ... UPS feed bus, 31, 32, 36, 37 ... Switch, 40, 41, 42 ... Changeover switch circuit, 50, 51 ... Power system bus, 60 ... Load, 61 ... CT, 62 ... Auxiliary switch, 63 ... Load 1, 64 ... Load 2, 65 ... CT, 66 ... Auxiliary switch, 71, 73 ... Thyristor SW, 72, 74 DESCRIPTION OF SYMBOLS ... Circuit breaker, 80 ... Current calculation part, 81 ... Addition calculator, 82 ... Auxiliary switch, 83 ... First order lag filter, 84, 85 ... Addition calculator.

Claims (2)

A plurality of uninterruptible power supplies (UPS) that can be operated in parallel, a UPS power supply bus connected in parallel to the output side of each of the uninterruptible power supplies, and a power system bus connected to an external AC power supply such as a commercial power supply And an uninterruptible power supply system formed of a changeover switch circuit that switches power supply to a load to a UPS power supply bus or a power system bus,
When switching the power supply to the load from the UPS power supply bus to the power system bus, or when switching from the power system bus to the UPS power supply bus, the load is supplied in parallel from both the buses to the load for a predetermined period. Control method of uninterruptible power supply system. In the control method of the uninterruptible power supply system according to claim 1,
A control method for an uninterruptible power supply system, wherein the current from the UPS power supply bus is controlled to gradually increase or decrease during the parallel power supply period.

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