JP4999639B2 - Uninterruptible power system - Google Patents

Description

  The present invention provides instantaneous voltage drop protection for supplying AC power to a load instead when the voltage of commercial AC power supplied from a commercial AC power source to the load temporarily decreases or when a power failure occurs temporarily. The present invention relates to an uninterruptible power supply such as a device.

  Conventionally, when the voltage of commercial AC power supplied to the load from a 100V or 200V commercial AC power supply is reduced for a short time or when it is interrupted for a short time, the instantaneous voltage drop that supplies AC power to the load instead Protection devices are widely used. For example, the instantaneous voltage drop protection device described in Patent Document 1 includes an auxiliary charging circuit including a step-up transformer and a diode rectifier, and an inverter unit that performs AC / DC mutual conversion, so that AC power from a commercial AC power supply is normal. In the supplied state, charging is first performed until the charging voltage of the electrolytic capacitor rises to some extent by the inverter unit, and thereafter, the voltage drop corresponding to the leakage current of the electrolytic capacitor is supplemented by the auxiliary charging circuit. When the voltage of commercial AC power from the commercial AC power supply drops instantaneously, the commercial AC power supply is disconnected from the load by a thyristor, and the electric energy stored in the electrolytic capacitor is converted to AC power by the inverter and supplied to the load. To do.

  In the conventional instantaneous voltage drop protection device, a thyristor, that is, a semiconductor AC switch is used to open and close the commercial AC power supplied from the commercial AC power supply and to open and close the compensated AC power supplied from the inverter unit. The advantage of using the semiconductor AC switch for opening and closing power in this way is that the time during which the power supplied to the load is cut off can be shortened because the on / off switching speed is fast. On the other hand, since the semiconductor AC switch has a voltage drop inside the element even when it is turned on (conductive), there is a disadvantage that power loss occurs in the element. In particular, when a large load current is supplied, this power loss cannot be ignored, and not only wasteful power consumption increases, but also a large cost for heat dissipation measures. Of course, the semiconductor AC switch has a problem that it is considerably more expensive than the relay described later.

  On the other hand, the instantaneous voltage drop protection device as described above is configured to switch between commercial AC power from the commercial AC power source and compensated AC power from the inverter using an electromagnetic relay instead of the semiconductor AC switch. Is also known. In the case of an electromagnetic relay, there is no problem of power loss because no voltage drop occurs when the relay is on. The price of the element itself is much cheaper than that of a semiconductor AC switch. However, with an electromagnetic relay, it is difficult to perform high-speed switching like a semiconductor AC switch.

  Specifically, for example, in a general single-stable relay, when the excitation coil is not energized, the movable piece is held in contact with one contact by the urging force of the return spring, and the excitation coil is energized. Then, the movable piece moves so as to contact the other contact by the magnetic force. When such a relay is used for an instantaneous voltage drop protection device, normally, commercial AC power is supplied to the load when the exciting coil is in a non-energized state, and compensated AC power is supplied to the load when the exciting coil is in an energized state. The relay is inserted on the feed line so that the connection is established. In general, such a relay requires a longer switching time for switching the contact when the energization of the exciting coil is interrupted than when switching the contact when starting energizing the exciting coil. For example, in the relay used by the inventors of the present application, the former is about 4 msec, while the latter is about twice that of 8 msec.

JP 2000-152519 A

  In the conventional instantaneous voltage drop protection device that employs an electromagnetic relay, the power supplied to the load is interrupted during the switching of the contacts. The tolerance for such a momentary power interruption varies depending on the load. Generally speaking, it is allowed to interrupt power for about 4 milliseconds at the time of occurrence of a momentary drop or the like. It is often unacceptable for power to be interrupted for about 8 milliseconds when commercial AC power is already supplied.

  The present invention has been made in view of these problems, and the purpose of the present invention is to connect to the output end even when an electromagnetic relay with a slow contact switching speed is used to eliminate power loss. An object of the present invention is to provide an uninterruptible power supply including an instantaneous voltage drop protection device capable of reducing the instantaneous interruption time of power supplied to a load.

The present invention, which has been made to solve the above problems, stores electric energy in a charging means when commercial AC power is supplied from a commercial AC power source and outputs the commercial AC power to a load. In the uninterruptible power supply that outputs to the load as compensated AC power instead of the commercial AC power by converting the electric energy stored in the charging means into DC / AC when the voltage temporarily decreases,
a) connecting a commercial AC power supply line to which the commercial AC power is supplied when the excitation coil is in a non-energized state and a load line for outputting power to the load, and when the excitation coil is in an energized state A first electromagnetic relay that switches contacts so as to connect the compensated AC power supply line to which the compensated AC power is supplied and the load line;
b) a second electromagnetic relay that opens and closes a contact so as to connect or disconnect the compensation AC power supply line and the load line;
c) The compensation electromagnetic power supply line and the load line are connected by the first electromagnetic relay and the second electromagnetic relay is closed in a state where the voltage by the commercial AC power supply is reduced. When the voltage recovery by the commercial AC power supply is detected in the state, the energization to the exciting coil of the relay is first stopped so as to switch the contact by the first electromagnetic relay, and then the predetermined time Control means for controlling the operation of the first and second electromagnetic relays so that the second electromagnetic relay is opened after elapse of
It is characterized by having.

  Here, the predetermined time is in the first electromagnetic relay, and when the energization is stopped while the excitation coil is energized, the commercial AC power supply line and the It is set in advance according to the length of the switching time until the switching of the contact is completed so that the load line becomes conductive. From the time when the second electromagnetic relay in the closed state is instructed to open and the energization of the exciting coil of the second electromagnetic relay is stopped, the contact is actually opened. The predetermined time is preferably determined in consideration of the response delay time.

  Specifically, assuming that the predetermined time is t, the switching time of the first electromagnetic relay is t1, and the response delay time of the second electromagnetic relay is t2, under the condition of t + t2 <t1, It is preferable to set t as large as possible.

  In the uninterruptible power supply according to the present invention, the first electromagnetic relay has a contact so that the compensating AC power line and the load line are connected in the event of a voltage drop of the commercial AC power supply or a short-time power failure. In this state, the second electromagnetic relay is closed so that the compensating AC power line and the load line are connected. In this state, compensated AC power obtained by DC / AC conversion of the electrical energy stored in the charging means by, for example, an inverter circuit is supplied to the load through the load line.

  When the voltage of the commercial AC power supply recovers, the control means that detects the recovery of the voltage first stops energization of the exciting coil of the relay so as to switch the contact by the first electromagnetic relay. As a result, the movable piece of the first electromagnetic relay starts to operate, and the connection between the load line and the compensation AC power supply line is disconnected, but the load line and the commercial AC power supply line are still connected. It does not reach. That is, there is a period during switching of the contacts. During that time, neither commercial AC power nor compensation AC power is supplied to the load line through the first electromagnetic relay, but since the second electromagnetic relay is closed at this time, the second electromagnetic relay Through this, compensated AC power is supplied to the load line, and power is continuously supplied to the load.

  The control means opens the second electromagnetic relay when a predetermined time has elapsed from the time when the energization of the exciting coil of the first electromagnetic relay is stopped. As a result, there is no supply of compensated AC power to the load line through the second electromagnetic relay, and the power supply to the load is temporarily interrupted. At that time, the load line and commercial AC are used in the first electromagnetic relay. The power supply line is on the verge of being connected. Therefore, immediately after that, the load line and the commercial AC power supply line are connected in the first electromagnetic relay, and the commercial AC power starts to be supplied to the load through the first electromagnetic relay.

  As described above, according to the uninterruptible power supply according to the present invention, even if it takes time to switch the contact of the first electromagnetic relay, the second electromagnetic relay is used in many ranges during the switching. Necessary power can be supplied to the load. Thereby, the period when the electric power supplied to load is interrupted can be shortened. Therefore, it is possible to suppress power loss and reduce costs by using an electromagnetic relay that hardly causes a voltage drop at the time of conduction while switching the power supply while keeping the instantaneous power supply interruption time to the load short.

  An instantaneous voltage drop protection device that is an embodiment of the uninterruptible power supply according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic block diagram of an instantaneous voltage drop protection device according to this embodiment.

  This instantaneous voltage drop protection device protects even when the voltage of the AC power supplied to the load 40 from the commercial AC power supply 1 of 100V or 200V temporarily drops (for example, about 1 second at the maximum). is there. In FIG. 1, a commercial AC power supply line 2 to which commercial AC power is supplied from an external commercial AC power source 1 is connected to a b terminal of a first relay 3 that is an electromagnetic relay, and a load line 4 leading to a load 40 is a first one. 1 is connected to the c terminal of the relay 3. The compensated AC power supply line 5 connected to the terminal a of the first relay 3 is connected to an inverter unit 7 including a plurality of switching elements via a filter 11 composed of an inductance and a capacitor.

  The compensating AC power supply line 5 and the load line 4 are also connected via a parallel circuit of a resistor 12 and a second relay 13 that is an electromagnetic relay. A power storage unit 8 including an electrolytic capacitor 9 is connected to the inverter unit 7, and the inverter unit 7 reverses the function of charging the electrolytic capacitor 9 by converting commercial AC power supplied through the resistor 12 to DC during normal operation. It also has a function of converting the electric energy held in the electrolytic capacitor 9 into DC / AC conversion.

  Similarly, in order to charge the electrolytic capacitor 9 of the power storage unit 8, the transformer 14, the bidirectional thyristor 15 connected in series to the primary side winding of the transformer 14, and the rectification connected to the secondary side winding of the transformer 14. A supplementary charging unit 10 including a diode 16, a capacitor 17, a resistor 18, and the like is provided. The electrolytic capacitor 9 can be charged from either the inverter unit 7 or the auxiliary charging unit 10. The bidirectional thyristor 15 of the auxiliary charging unit 10 is controlled to be turned on / off by a drive signal given by the auxiliary charging drive unit 22. Each switching element of the inverter unit 7 is controlled to be turned on / off by a drive signal supplied from the inverter drive unit 24.

  The input voltage detection unit 21 monitors the amplitude (peak value or effective value) of the voltage on the commercial AC power supply line 2 and gives the amplitude value to the control unit 20. The charging voltage detector 23 detects the charging voltage held in the electrolytic capacitor 9 and inputs the voltage value to the controller 20. The output voltage detection unit 26 detects the voltage on the load line 4 and inputs the amplitude (peak value or effective value) of the voltage to the control unit 20. The load current supplied to the load 40 is detected by a current transformer 6 and a load current detection unit 27 provided on the load line 4, and the current value is input to the control unit 20. The control unit 20 is configured mainly with a CPU, RAM, ROM, and the like, and executes various controls and processes described later according to a control program stored in advance.

  The first relay 3 is a single-stable electromagnetic relay that switches between a bc connection state in which the b terminal and the c terminal are connected and an ac connection state in which the a terminal and the c terminal are connected. is there. Specifically, as shown in FIG. 3, the conductive movable piece 30 having one end fixedly connected to the c terminal is pulled by the urging force of the return spring 31, and the other movable end is in contact with the b terminal. It has become. When the excitation coil 32 is energized, the movable piece 30 is pulled against the urging force of the return spring 31 by the magnetic force of the excitation coil 32, and the movable end contacts the a terminal. Therefore, switching from the bc connection state to the ac connection state is performed by the action of magnetic force by energizing the excitation coil 32, and conversely, switching from the ac connection state to the bc connection state is performed by the excitation coil 32. This is performed by the urging force of the return spring 31 in a state where there is no magnetic force due to.

  On the other hand, the second relay 13 is considered to be the electromagnetic relay shown in FIG. 3, with the b terminal open, the load line 4 connected to the a terminal, and the compensated AC power supply line 5 connected to the c terminal. That's fine. The switching operation of the first and second relays 3 and 13 is controlled by the drive current supplied from the switching drive unit 25.

  Next, the power compensation operation in the instantaneous voltage drop protection device of this embodiment will be described with reference to FIG. 2, (a) to (d) are schematic timing diagrams of the main part of the instantaneous voltage drop protection device of this embodiment, and only (e) is a conventional one (that is, the second relay 13 in this embodiment is provided). FIG. 6 is a schematic timing diagram of the instantaneous voltage drop protection device (when not).

  The control unit 20 measures the voltage value of the commercial AC power by the input voltage detection unit 21 at predetermined time intervals, and determines whether the measured value is within a predetermined normal value range or normal. When it is normal, since the drive current is not output from the switching drive unit 25, the first relay 3 is in the bc connection state, and the second relay 13 is in the open state. Thereby, commercial AC power is supplied from the load line 4 to the load 40. At this time, since commercial AC power is supplied to the inverter unit 7 via the resistor 12, the electrolytic capacitor 9 is charged based on the commercial AC power, and electric energy is stored in the electrolytic capacitor 9.

  Here, the charging procedure of the electrolytic capacitor 9 will be briefly described. That is, when the voltage value detected by the charging voltage detection unit 23 is equal to or less than the first predetermined value V1, the control unit 20 operates the inverter unit 7 via the inverter drive unit 24, and the inverter unit 7 DC electric energy obtained by DC conversion is stored in the electrolytic capacitor 9. At this time, the bidirectional thyristor 15 is turned off and the auxiliary charging unit 10 is not operated. When the voltage value detected by the charging voltage detection unit 23 reaches the rated voltage Vf (Vf> V1), the operation of the inverter unit 7 is stopped and the charging operation is stopped.

  Even when the switching element of the inverter unit 7 is in the OFF state, the electric energy of the electrolytic capacitor 9 charged to the rated voltage Vf is gradually reduced by natural discharge. Therefore, when the charging voltage decreases due to spontaneous discharge and the voltage value decreases to the second predetermined value V2 (normally V1 <V2 <Vf), this is based on the voltage value detected by the charging voltage detector 23. The recognized control unit 20 causes the bidirectional thyristor 15 to conduct through the auxiliary charging drive unit 22. Then, an alternating current flows through the primary side winding of the transformer 14, and a predetermined alternating voltage is generated at both ends of the secondary side winding. This voltage is converted into a direct current by the rectifying diode 16 and starts to charge the electrolytic capacitor 9 via the resistor 18. At this time, the inverter unit 7 is not operated, and the charging voltage of the electrolytic capacitor 9 starts to recover only by the auxiliary charging unit 10. When the voltage value detected by the charging voltage detection unit 23 reaches the rated voltage Vf, the operation of the auxiliary charging unit 10 is stopped and the charging operation is stopped.

  If the commercial AC voltage temporarily drops or the power supply is temporarily cut off due to an abnormality in the power supply provider's power supply, etc., it is determined that the input voltage is out of the normal range, that is, abnormal It is determined that a significant voltage drop has occurred (a momentary drop is detected), and the control unit 20 starts control to supply compensated AC power instead of commercial AC power. First, a drive current starts to flow from the switching drive unit 25 to the exciting coils of the first relay 3 and the second relay 13, contacts are set so that the first relay 3 is in the ac connection state and the second relay 13 is in the closed state. Switch. At the same time, the inverter unit 7 is operated by the inverter driving unit 24 so that the voltage held in the electrolytic capacitor 9 is DC / AC converted to be output.

  Although a certain amount of switching time is required for the contacts of the first relay 3 and the second relay 13 to be switched (the first switching period shown in FIG. 2B), in this embodiment, the switching time is The maximum is about 4 milliseconds. Therefore, as shown in FIG. 2 (d), the power supplied to the load 40 is interrupted only for a period of about 4 milliseconds at maximum, and then the compensated AC power whose waveform is shaped through the filter 11 passes through the load line 4. The load 40 is supplied.

  When the voltage drop or power failure of the commercial AC power from the commercial AC power supply 1 is resolved, the control unit 20 detects the return of power by a signal from the input voltage detection unit 21 and supplies the commercial AC power instead of the compensated AC power. Perform control to return to That is, first, the supply of drive current from the switching drive unit 25 to the first relay 3 is stopped, and the contact is switched so that the first relay 3 is in the bc connection state. On the other hand, the supply of the drive current to the second relay 13 continues, and the operation of the inverter unit 7 continues as before. When the energization to the exciting coil 32 of the first relay 3 is cut off, the movable piece 30 of the relay 3 starts to move as described above, and the connection between the a-c terminals is cut, but the second is still Since the relay 13 is in a closed state, the compensated AC power is supplied from the compensated AC power supply line 5 to the load line 4 only through the second relay 13 and applied to the load 40.

  The controller 20 stops the supply of the drive current to the second relay 13 when 6 milliseconds have elapsed from the stop of energization of the first relay 3 (see FIG. 2C). That is, the stop of energization to the second relay 13 is delayed by 6 msec from the stop of energization to the first relay 3. The delay time t of 6 milliseconds is the switching time t1 required for the first relay 3 to completely switch from the ac connection state to the bc connection state, and the energization of the excitation coil of the second relay 13 is stopped. And t + t2 <t1 is determined according to the delay time t2 until the contact is actually opened. Here, based on actual measurement or the like, it is assumed that the switching time t1 is 8 ms, the delay time t2 is 1 ms or less, and the delay time t is set to 6 ms. If the delay time t is too short with respect to the switching time t1, the time during which the power supplied to the load 40 is interrupted becomes long. Conversely, if the delay time t is too long with respect to the switching time t1, the commercial AC power supply line is connected to the load line 4. 2 and the compensated AC power supply line 5 are connected at the same time, and normal power is not supplied to the load 40. Therefore, it is desirable to determine an appropriate delay time t in consideration of such matters.

  When the second relay 13 is opened, it is not necessary to supply compensated AC power. Therefore, the energization to the exciting coil of the second relay 13 is stopped and the inverter is configured to stop the DC / AC conversion operation by the inverter unit 7. The drive unit 24 is controlled.

  Now, after the energization of the second relay 13 is stopped after the delay of 6 msec, the relay 13 is opened immediately, and as expected, the relay 3 b- c Assume that the contact is switched to the connected state. In this case, as shown in FIG. 2 (d), the load 40 is applied to the load 40 only for a maximum period of about 2 milliseconds from when the second relay 13 is opened until the bc connection state of the first relay 3 is established. The supplied power is interrupted, and then the supply of commercial AC power is resumed. On the other hand, when the second relay 13 is not provided as in the prior art, or when the delay time is zero even if the second relay 13 is provided, as shown in FIG. The period during which the power supplied to the load 40 is interrupted when the commercial power supply voltage is restored is 8 ms. Thus, according to the instantaneous voltage drop protection device of the present embodiment, it can be seen that the power interruption period can be greatly reduced as compared with the conventional case.

  The above-described embodiment is an example of the present invention, and it is a matter of course that modifications, corrections, and additions may be appropriately made within the scope of the present invention, and included in the scope of the claims of the present application.

  For example, the above embodiment has been described with respect to an instantaneous voltage drop protection device that temporarily supplies power by using electric energy stored in a capacitor, but the present invention uses, for example, electric energy stored in a storage battery, It is obvious that the present invention can be generally applied to an uninterruptible power supply that supplies power for a longer time.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block block diagram of the instantaneous voltage drop protection apparatus which is one Example of the uninterruptible power supply which concerns on this invention. The schematic timing diagram of the principal part in the instantaneous voltage drop protective device of a present Example. The schematic block diagram of the electromagnetic relay currently used for the 1st relay in the instantaneous voltage drop protective device of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Commercial alternating current power supply 2 ... Commercial alternating current power supply line 3 ... 1st relay 30 ... Movable piece 31 ... Returning spring 32 ... Excitation coil 4 ... Load line 5 ... Compensation alternating current power supply line 6 ... Current transformer 7 ... Inverter part 8 ... Power storage unit 9 ... Electrolytic capacitor 10 ... Supplementary charging unit 11 ... Filter 12 ... Resistor 13 ... Second relay 20 ... Control unit 21 ... Input voltage detection unit 22 ... Supplementary charging drive unit 23 ... Charge voltage detection unit 24 ... Inverter drive unit 25 ... switching drive unit 26 ... output voltage detection unit 27 ... load current detection unit 40 ... load

Claims (2)

When commercial AC power is supplied from a commercial AC power source, electrical energy is stored in the charging means, and the commercial AC power is output to a load. When the voltage from the commercial AC power supply temporarily decreases, the electrical energy is stored in the charging means. In the uninterruptible power supply that converts the electrical energy into DC / AC and outputs it to the load as compensated AC power instead of the commercial AC power,
a) connecting a commercial AC power supply line to which the commercial AC power is supplied when the excitation coil is in a non-energized state and a load line for outputting power to the load, and when the excitation coil is in an energized state A first electromagnetic relay that switches contacts so as to connect the compensated AC power supply line to which the compensated AC power is supplied and the load line;
b) a second electromagnetic relay that opens and closes a contact so as to connect or disconnect the compensation AC power supply line and the load line;
c) The compensation electromagnetic power supply line and the load line are connected by the first electromagnetic relay and the second electromagnetic relay is closed in a state where the voltage by the commercial AC power supply is reduced. When the voltage recovery by the commercial AC power supply is detected in the state, the energization to the exciting coil of the relay is first stopped so as to switch the contact by the first electromagnetic relay, and then the predetermined time Control means for controlling the operation of the first and second electromagnetic relays so that the second electromagnetic relay is opened after elapse of
An uninterruptible power supply comprising:   The predetermined time is in the first electromagnetic relay, and when the energization is stopped while the excitation coil is energized, the commercial AC power supply line and the load line from the energization stop point. The uninterruptible power supply according to claim 1, wherein the uninterruptible power supply device is preset in accordance with the length of switching time until the switching of the contacts is completed so as to be conductive.

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