JP2012239249A - Uninterruptible power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an uninterruptible power supply system that can suppress an abnormal current at system switching in a relatively simple configuration and with high control reliability.SOLUTION: The uninterruptible power supply system includes: a converter 11; an inverter 12 for feeding a load via a first mechanical switch 13; a parallel circuit of a second mechanical switch 14 and a semiconductor switch 15 having an input of bypass input power supply and an output connected to the load; a bypass current detector 16; and switching control means 2. At a command to switch the load feed from the output of the inverter 12 to the bypass input power supply, the switching control means 2 starts phase control means 28 for the semiconductor switch 15 and outputs an off command to the first mechanical switch 13, and a predetermined time later, outputs an on command to the second mechanical switch 14. The phase control means 28 controls an ignition phase of the semiconductor switch 15 such that a current flowing through the bypass current detector 16 becomes equal to or lower than a predetermined current limit reference value.

Description

  The present invention relates to an uninterruptible power supply system capable of continuously supplying stable power to a load even when a commercial power supply becomes abnormal.

  In many cases, the load of a normal uninterruptible power supply system is, for example, a computer that does not allow an instantaneous power failure. Here, the uninterruptible power supply system is a system having at least one uninterruptible power supply. When operating the load, when the uninterruptible power supply fails or when the uninterruptible power supply needs to be maintained, it is necessary to quickly switch the system between the uninterruptible power supply and the commercial power supply.

  When the above system switching is performed, different systems are connected, so that abnormal currents such as cross currents are generated due to voltage or phase mismatch between the two systems at the system switching point. If this abnormal current is large, the system changeover switch may fail, or the uninterruptible power supply may stop due to an overcurrent failure.

  As a measure to suppress such abnormal current, when switching the system from the uninterruptible power supply to the commercial power supply, detect the deviation between the output current and the load current of the uninterruptible power supply so that the deviation becomes zero Proposals have been made to control the output voltage of the uninterruptible power supply (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-4544 (page 2-3, FIG. 1)

  The method disclosed in Patent Document 1 aims to smoothly shift the load from the uninterruptible power supply to the commercial power supply even in a light load state, but relies only on output voltage control. For example, when a capacitor is connected to the load, the response speed of the control may be a problem, and it may be difficult to cope with an abnormal phenomenon such as a short-time overcurrent on the load side. Therefore, there is a problem in the control reliability of the complicated control of performing the closed loop control of the output of the uninterruptible power supply.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an uninterruptible power supply system capable of suppressing an abnormal current during system switching with a relatively simple configuration and high control reliability. And

  In order to achieve the above object, an uninterruptible power supply system of the present invention includes a converter that converts an input voltage of an AC power source into a direct current, a direct current from the battery when the direct current or the alternating current power fails, and an alternating current. An inverter that supplies power to the load via one mechanical switch, a bypass input power supply as an input, and an output flows to the parallel circuit of the second mechanical switch and the semiconductor switch connected to the load, and to the bypass input power supply A bypass current detector for detecting current; and a switching control means for controlling the first mechanical switch, the second mechanical switch, and the semiconductor switch, wherein the switching control means supplies power to the load. When receiving a command to switch from the output of the inverter to the bypass input power source, the phase control means of the semiconductor switch is started and the second An off command is output to the mechanical switch, an on command is output to the first mechanical switch after a predetermined time has elapsed, and the phase control means has a current flowing through the bypass current detector that is equal to or less than a predetermined current limit reference value. The ignition phase of the semiconductor switch is controlled so that

  According to the present invention, it is possible to provide an uninterruptible power supply system that can suppress a cross current during system switching with a relatively simple configuration and high control reliability.

The circuit block diagram of the uninterruptible power supply system which concerns on Example 1 of this invention. The circuit block diagram of the uninterruptible power supply system which concerns on Example 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, an uninterruptible power supply system according to Embodiment 1 of the present invention will be described with reference to FIG.

  In FIG. 1, an uninterruptible power supply system main circuit 1 receives an AC input, a battery input, and a bypass input, and supplies the AC output to a load (not shown). The AC input is given to the converter 11 through the switch 52RC. The direct current output of the converter 11 is converted again into alternating current by the inverter 12 and becomes an alternating current output via the mechanical switch 13. When the AC input is healthy, power is supplied from the AC input to the load through the above-described route. The battery input is connected to the input of the inverter 12 via the switch 72B. When the AC input is lost due to a power failure, power is supplied from the battery input to the load. Note that illustration of the control circuit of the converter 11 and the inverter 12 is omitted.

  The bypass input is connected to the AC output (load) through the switch 52RS and a parallel circuit of the mechanical switch 14 and the semiconductor switch 15 connected in series. When the converter 11 or the inverter 12 breaks down or when maintenance is performed, the semiconductor switch 15 is turned on, the mechanical switch 13 is turned off, and the mechanical switch 14 is turned on to supply power from the AC input. Switch to power supply from bypass input.

  The mechanical switch 13, the mechanical switch 14, and the semiconductor switch 15 are operated according to a command from the switching control circuit 2. The switching control circuit 2 is given a current feedback signal by a bypass current detector 16 provided in the uninterruptible power supply system main circuit 1.

  The switching control circuit 2 is given a manual switching command from the manual switching sequence circuit 3 and an automatic switching command from the automatic switching logic circuit 4. Hereinafter, the internal configuration of the switching control circuit 2 will be described.

  The operation circuit 21 and the operation circuit 22 perform an on / off operation of the mechanical switch 13 and the mechanical switch 14, respectively. The manual switching command from the manual switching sequence circuit 3 and the automatic switching command from the automatic switching logic circuit 4 are given to the OR circuit 23, and when the switching command to bypass power feeding is given, the output of the OR circuit 23 is the operation circuit 21. In addition, an off command for the mechanical switch 13 is given to the operation circuit 22 and an on command for the mechanical switch 14 is given to the operation circuit 22 via the delay circuit 24. At the same time, a command to turn on an enable circuit 27 described below is given.

  The current feedback signal from the bypass current detector 16 is matched with the set current control reference signal, and the deviation is amplified by the current controller 25 and input to the enable circuit 26. The output of the enable circuit 26 is given to the phase control circuit 27. The phase control circuit 27 controls the ignition phase of the semiconductor switch 15 via the drive circuit 28.

  Next, the operation will be described. Usually, the uninterruptible power supply system turns on the mechanical switch 13 and supplies the load with the output of the inverter 12 as an AC output. At this time, the mechanical switch 14 and the semiconductor switch 15 are off. In this state, when the inverter 12 or the converter 11 fails or the inverter 12 detects an overload, a switching condition is created by the switching logic circuit 4. Then, the enable circuit 26 is instantly turned on, and the phase control of the semiconductor switch 15 by the output of the current controller 25 becomes effective.

  At this time, since the current feedback signal from the bypass current detector 16 is zero (no current flows) with respect to the current limit reference signal, the output of the current controller 26 swings to the minimum value, and the phase control circuit 27 The drive circuit 28 is driven with the minimum phase (maximum firing angle). At this time, if the output of the inverter 12 and the bypass input are synchronized, the bypass current of the load current phase or the like is smaller than the current limit reference signal, so that the phase control circuit 27 continues to drive the drive circuit with the minimum phase (maximum firing angle). 28 is driven.

  However, when the output of the inverter 12 and the bypass input are asynchronous and a transformer or a capacitor is connected to the load, the semiconductor switch 15 on the bypass input side is turned on and at the same time an excessive bypass current flows due to a sudden phase change. The drive circuit 28 is driven with an ignition phase that exceeds the limit reference signal and corresponds to the difference (the larger the difference, the longer the ignition phase and the longer the OFF period of the semiconductor switch 15). As a result, the bypass current is limited by the semiconductor switch 15. The excessive current due to the voltage phase difference at the time of non-synchronization is attenuated in, for example, several cycles in which the bias magnetism of the transformer connected to the load is restored. Even if the mechanical switch 14 is turned on, an excessive current does not flow from the bypass input, and power supply to the load can be continued by the bypass power source.

  In the control operation, the output of the inverter 12 is cut off by turning off the mechanical switch 13. The AC input and the bypass input wrap for a short time due to the inherent delay of the operation circuit 21 and the mechanical switch 13, but the meaning of wrapping during a normal failure or overload is insignificant. However, for example, it is possible to increase the lap period by delaying the operation of the mechanical switch 13 during manual switching.

  FIG. 2 is a circuit configuration diagram of the uninterruptible power supply system according to the second embodiment of the present invention. About each part of this Example 2, the same part as each part of the uninterruptible power supply system which concerns on Example 1 of this invention of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The second embodiment is different from the first embodiment in that the bypass input is not supplied from the AC power supply but from the standby uninterruptible power supply system 1B, and the inverter 12 of the uninterruptible power supply system main circuit 1A An inverter current detector 17 for detecting an output current is provided, and a difference from the bypass current detector 16 is calculated by a difference current detector 29 in the switching control circuit 2A, and this difference current is input to the current controller 25. This is the point.

  A configuration in which the bypass input is fed from the standby uninterruptible power supply system 1B is called a series redundant system. Similar to the uninterruptible power supply system main circuit 1A, the standby uninterruptible power supply system 1B includes a converter 11B, an inverter 12B, mechanical switches 13B and 14B, and a semiconductor switch 15B.

  In such a configuration, when the lap is manually switched from the inverter 12 to the bypass power supply side, the outputs of the two inverters 12 and 12B wrap, causing interference in inverter output control and the rated current between the inverters. The above cross current may flow. At this time, the differential current between the bypass current detector 16 and the inverter current detector 17 in the uninterruptible power supply system main circuit 1A is detected by the differential current detection circuit 30, and this current is set to a current limit reference signal (for example, a rated current). The current controller 25 compares whether or not the current is within the current limit reference signal, and the bypass input side current is limited by phase control of the semiconductor switch 15 if it is equal to or greater than the current limit reference signal. When the inverter-side mechanical switch 13 is turned off after a certain period of time, the cross current disappears and the bypass current becomes equal to or lower than the rated current, so the mechanical switch 14 on the bypass input side is turned on.

  According to the above operation, according to the second embodiment, an excessive cross current does not flow even when wrapping between inverter outputs, and power supply can be switched from the inverter side to the bypass side without detecting an overcurrent.

  Also in the second embodiment, the output of the inverter 12 is cut off by turning off the mechanical switch 13, but the AC input and the bypass input wrap for a period of several cycles due to the inherent delay of the operation circuit 21 and the mechanical switch 13. If the bypass power supply is a generator that is slow in response to a sudden load change or an old type uninterruptible power supply, it may be necessary to delay the load transition at the time of switching, so the operation of the mechanical switch 13 is delayed. It is also possible to increase the lap period.

1. Uninterruptible power supply system main circuit 1A Regular uninterruptible power supply system main circuit 1B Backup uninterruptible power supply system 2, 2A Switching control circuit 3 Manual switching sequence circuit 4 Automatic switching logic circuit 11, 11B Converter 12, 12B Inverter 13, 13B Mechanical switch 14, 14B Mechanical switch 15, 15B Semiconductor switch 16 Bypass current detector 17 Inverter current detector 21 Operation circuit 22 Operation circuit 23 OR circuit 24 Delay circuit 25 Current controller 26 Enable circuit 27 Phase control circuit 28 Drive Circuit 29 Differential current detection circuit

Claims (3)

A converter that converts the input voltage of the AC power source to DC,
An inverter that converts direct current from the battery to alternating current when the direct current or the alternating current power supply fails, and supplies power to the load via the first mechanical switch;
A parallel circuit of a second mechanical switch having a bypass input power supply as input and an output connected to the load, and a semiconductor switch;
A bypass current detector for detecting a current flowing in the bypass input power supply;
Switching control means for controlling the first mechanical switch, the second mechanical switch, and the semiconductor switch,
The switching control means includes
When receiving a command to switch the power supply to the load from the output of the inverter to the bypass input power source, the phase control means of the semiconductor switch is started and an off command is output to the second mechanical switch. An on command is output to the first mechanical switch after a lapse of time,
The uninterruptible power supply system characterized in that the phase control means controls the ignition phase of the semiconductor switch so that the current flowing through the bypass current detector is not more than a predetermined current limit reference value. A converter that converts the input voltage of the AC power source into DC, an inverter that converts DC from the battery into AC when the DC or the AC power supply fails, and supplies power to the load via the first mechanical switch;
A parallel circuit of a second mechanical switch having a bypass input power supply as input and an output connected to the load, and a semiconductor switch;
A normal uninterruptible power supply system comprising switching control means for controlling the first mechanical switch, the second mechanical switch, and the semiconductor switch;
A backup uninterruptible power supply system having the same configuration as the normal uninterruptible power supply system, the output of which is the bypass input power supply of the normal uninterruptible power supply system,
The switching control means of the regular uninterruptible power supply system is:
When receiving a command to switch the power supply to the load from the output of the inverter to the bypass input power source, the phase control means of the semiconductor switch is started and an off command is output to the second mechanical switch. An on command is output to the first mechanical switch after a lapse of time,
The phase control means includes
The ignition phase of the semiconductor switch so that the differential current of each current detected by the bypass input current detector and the inverter output current detector provided in the normal uninterruptible power supply system is equal to or less than a predetermined current limit reference value. An uninterruptible power supply system characterized in that it is controlled.   When receiving an instruction to switch power supply to the load from an output of the inverter to the bypass input power supply side, an OFF instruction is output to the second mechanical switch after a predetermined delay. The uninterruptible power supply system according to claim 1 or 2.

Images