JPS6158437A - Overload protecting operating method of no-break power source - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a main circuit that combines a DC voltage obtained from an AC power source via a rectifier and a storage battery voltage, and supplies power to a load via a boost chopper J3 and an inverter. a constant voltage control circuit for controlling the step-up chopper so as to keep the output voltage of the inverter constant; and a constant voltage control circuit for controlling the step-up chopper so as to keep the output voltage of the inverter constant; The present invention relates to an overload protection operation method for an uninterruptible power supply equipped with a current control circuit that controls a current control circuit.

[Technical background of the invention and its problems]

There are various types of uninterruptible power supplies that match the DC voltage obtained from the AC power source via a rectifier with the storage battery voltage and supply power to the AC load via an inverter. There are two methods shown in FIGS. 6 and 7.

In the device shown in FIG. 6, a DC voltage is obtained from an AC type '&1 through a rectifier 2, and this is matched with the output voltage of a storage battery 3, and AC power is supplied to an AC load 7 through a DC filter 4 and an inverter 6. supply The rectifier 2 is composed of, for example, a Nyristor, and the output voltage can be controlled by controlling its firing angle. The DC filter 4 consists of a DC reactor 4a and a capacitor 4b. The inverter 6 variably controls the output DC voltage of the DC filter 4 using PWM (pulse width modulation) control.

The apparatus shown in FIG. 7 is obtained by replacing the DC filter 4 in the apparatus shown in FIG. 6 with an R1 pressure chopper 5.

The boost chopper 5 includes a DC reactor 5a, a self-extinguishing controllable 21I rectifier 5b, a diode 5c, and a capacitor 5d. The self-extinguishing type rectifying element 5b is composed of a gate turn-off thyristor, a power transistor, etc., which itself has an arc-extinguishing ability, or a thyristor to which an arc-extinguishing circuit is added to enable on/off control.

In the circuit system shown in FIG. 7, the input DC voltage to the inverter 6 is made higher than the output voltage of the storage battery 3 by the step-up chopper 5, so the element current of the inverter 6 is smaller than that in the circuit system shown in FIG. Become. Therefore, this method is advantageous in the case of large capacity loads. Further, in the circuit shown in FIG. 7, the boost chopper 5 can be provided with a voltage control function, and therefore the inverter 6 can be controlled with a fixed pulse width, thereby simplifying the inverter control circuit.

The method shown in Figure 7 has the advantage that both the main circuit and the control circuit are simpler than the system shown in Figure 6, but on the other hand, it is overloaded by load short circuits, motor starting current, transformer inrush current, etc. There are the following problems with protection when a situation occurs.

In the method shown in Figure 6, when an overload occurs, the inverter 6
By narrowing down the pulse width of the output 1. II hanging down,
Thereafter, constant current control is performed to wait until the overloaded load branch is released, and after the overloaded state is released, normal operation is resumed. However, in the method shown in FIG. 7, the pulse width of the inverter 6 is fixed, and the boost chopper 5 cannot output a voltage lower than the input voltage, and cannot reduce the output voltage when an overload occurs. . Therefore, it was necessary to prepare a separate auxiliary power source with a low voltage value and switch to the auxiliary power source in the event of an overload, or, if this was not possible, to shut down the device to protect the device.

[Purpose of the invention]

An object of the present invention is to provide an operating method that can achieve overload protection without stopping the device or switching to an auxiliary power source in the event of a short-circuit accident or overload in the system shown in FIG. 7, which has a simple circuit configuration. It is in.

[Purpose of the invention]

In order to achieve the above object, the present invention suppresses the output current of the inverter to below the current limit value of the current control circuit by turning off the inverter when a short circuit accident or overload occurs on the output side of the inverter. Turn off the boost chopper and turn off the storage battery, reduce the settings of the constant voltage control circuit and current control circuit to the minimum value, and after a predetermined period of time turn on the inverter and at least set the current control circuit. The output voltage of the inverter is gradually increased through the rectifier or boost chopper by gradually increasing the value, and the current below the limit current value is supplied to the load until the V1 short-circuit accident or overload is released, and the output voltage of the inverter is gradually increased through the rectifier or boost chopper. The feature is that the storage battery is turned on after the overload is released.

[Embodiments of the invention]

FIG. 1 shows an example of an apparatus for carrying out the method of the invention. The main circuit components indicated by numerals 1 to 7 are the same as those shown in FIG. The storage battery 3 is connected to the output side of the rectifier 2 via a switch 9. Further, a discharge resistor 23 is connected to the output side of the boost chopper 5 via a switch 22.

The switch 22 and the resistor 23 may be small, short-time rated ones. A current transformer 10 is provided to detect the output current BS of the inverter 6.

In order to control the output voltage AS of the inverter 6 to be constant, the controllable rectifier 5b of the boost chopper 5 is connected to the constant voltage control circuit 1.
1, the ignition is controlled via the ignition circuit 13. A current control circuit 12 is provided to control the rectifier 2 and the boost chopper 5 in order to suppress the output current BS supplied from the inverter 6 to the load 7 below a predetermined current limit value. The ignition of the rectifier 2 is controlled by an ignition circuit 20 . The boost chopper 5 is controlled by the current control circuit 12 via the constant voltage control circuit 11, and the open control circuits 11 and 12 are connected via an analog switch 19. Ma lζ,
The control of the rectifier 2 by the current control circuit 12 is performed via the charging control circuit 17, and the control of the rectifier 2 by the current control circuit 12 is performed via the charging control circuit 17. An analog switch 18 is interposed between '17. Storage battery 3
and each output voltage VB, KS of rectifier 2 is voltage detector 1
6a.

16b and input to the comparator 21. Storage battery voltage V detected by voltage detector 16a
B is also introduced into the charging control circuit 17. The output current BS detected by the current transformer 10 is monitored by an overcurrent detection circuit 15, which sends an overcurrent signal C8 to the logic sequence circuit 14 in the case of an overcurrent. The output signal of the comparator 21 is also introduced into the logic sequence circuit 14 . The logic sequence circuit 14 makes a logical judgment as described below based on the meat input signal, and outputs a signal DS for controlling gate blocking or deblocking of the inverter 6, and an ignition circuit 13.
．． Signals ES and FS that control on/off of 20 output signals
, open/close signals for switches 9 and 22, open/close signals for analog switches 18.19, and on/off signals for each control circuit 11, 12, and 17, such as flip-flops, timers, AND circuits, OR circuits, and No. 2 lower circuits. It can be configured with a logic IC such as, or a microprocessor can be used. In addition, each control circuit 11.1
Let the output signals of 2.17 be GS, 1-IS, and JS, respectively.

Next, the control operation performed by the device shown in Fig. 1 is shown in Fig. 2 (rectification occurs when the rectifier is restarted, and the output current BS is set to the limiting current value ■H before the rectifier output voltage KS reaches the storage battery voltage VB.
) and Figure 3 (when the rectifier output voltage KS reaches the storage battery voltage VB when the rectifier is restarted, the output current B
The explanation will be given with reference to the operation waveform diagram (when S reaches the limit current value IH) and the flowchart of FIGS. 4(a> and 4(b)).

During the period from time 10 to t1, there is a steady operation state, and the switch 9
is on, switch 22 is off, and switches 18 and 19 are both off. The controllable rectifying element 5b of the boost chopper 5 is controlled to fire by the constant voltage control W circuit 11 so that the inverter output voltage As becomes a predetermined value. Note that the limiting current value IH1 set in the current control circuit 12 and the detection level IC set in the overcurrent detection circuit 15 are both determined mainly by the overload temperature of the inverter 6, and usually IC> It is 1.

It is assumed that a short-circuit accident or overload occurs on the load side at time t1 (step 81). As a result, the inverter output current 88 increases with a steep slope, and the inverter output voltage As rapidly decreases. When the voltage reaches 83-IC (time t2), the overcurrent detection circuit 15 operates and the signal C8 is turned on. At the same time, the inverter 6 is blocked via the logic sequence circuit 14 (
signal QDS off), the ignition circuits 13 and 20 are turned off (signals ES, FS off). As a result, the output voltage ΔS rapidly decreases to zero, and the output current 88 also rapidly decreases to zero. On the other hand, the output signal GS of the constant voltage control circuit 11,
The output signals H8 and J5 of the current control circuit 12 and the output signal JS of the charging control circuit 17 are rapidly reduced to the minimum level. Further, an off command is given to the switch 9, and the switch 9 is turned off at time t4 after the return rR interval T24. Further, at time 2, an on command is given to the switch 22 (step S2), and the switch 22 is turned on after the operating time T.
23, at time t3, the charge in the capacitor 5d of the boost chopper 5 is rapidly discharged via the discharge resistor 23,
The output voltage LS of the boost chopper 5 is lowered (step 83).

The logic sequence circuit 14 has a timer function, and starts counting at time t2. When time is up at time t5 after time T25 has elapsed, the signal DS is turned on and the inverter 6 is gate-deblocked, the switch 22 is turned off, and the signal FS is turned on to turn on the ignition circuit 20, and the signal FS is switched on. The ignition circuit 20 is turned on from 18, and the analog switch 18 is turned on (step 34). As a result, charging control circuit 1
The output signal JS of the rectifier 2 gradually rises from the minimum level as the initial value, and the output voltage KS of the rectifier 2 also gradually rises. -Return. At this time, since the inverter 6 is gate deblocked, the output voltage As of the inverter 6 also gradually increases in response to the upper R of the voltage KS, and a so-called soft start is performed here.

6. If the short-circuit accident continues, as the output voltage As increases, the output current BS also increases by 1" (step 35). As shown in FIG. 2, before the output voltage KS of the rectifier 2 reaches the storage battery voltage VB. When the output current BSS current control circuit 12 reaches the limit current 1 at time t6, the output current B
Thereafter, S is suppressed to the limiting current value 1 by the control action of the current control circuit 12 and the rectifier 2, and the output voltage AS does not rise any further (steps 36, 87, 88>. On the other hand, as shown in FIG. As shown, when the output voltage KS of the rectifier 2 gradually increases and the output voltage KS becomes equal to the storage battery voltage VB at time t7 before the output current 88 reaches the limit current value IH, the comparator 21 changes the operating output. As a result, the analog switch 18 is turned off and the analog switch 19 is turned on via the logic sequence circuit 14, an operation command is given to the constant voltage control circuit 11 and the ignition circuit 13, and from then on, the rectifier 2 operates as the ignition circuit. The boost chopper 5 increases the output voltage As of the inverter 6 until it reaches the normal voltage setting level VR. When the output current BS reaches the limit current value II-1 at time t8 during the voltage increase process by the chopper 5, the output current BS is changed to the limit current value II by the action of the current control circuit 12, as described above. -1, output voltage As
The boost chopper 5 is controlled so as not to increase the voltage any further (steps S10, 311, S12, 813).

When the short circuit accident or overload is canceled, the analog switch 19 is turned off and the switch 9 is turned on (step 14) after the output voltage As reaches the normal voltage setting level VR through the voltage increase process described above. ), the output voltage As is constant voltage controlled by the i control operation of the constant voltage control circuit 11 (step S15>).

If a short circuit or overload continues for a long time, if the short circuit or overload condition is canceled by tripping the circuit breaker on the load side (not shown in the diagram), the current control operation will switch to constant voltage control operation. The output voltage As of the inverter 6 recovers to the constant voltage setting level VR. In other words, in either case, the output current 88 of the inverter 6 is suppressed below the current limit value of the current control circuit 12, and the output current That is, selection and switching between constant voltage control operation and constant current control operation is automatically performed depending on the level of load current.

In the device shown in FIG. 1, an example has been described in which the phase of the rectifier is fixed and constant current control is performed using the boost chopper 5.
The phase of the boost chopper 5 may be fixed and the rectifier 2 may perform constant current control. This is because the output current BS and the output current of the rectifier 2 are in a proportional relationship while the switch 9 is off. In that case, as shown in FIG. 5, the current detected by the current transformer 24 provided on the output side of the rectifier 2 may be introduced into the current control tlj outlet 12.

[Effects of the Invention] As detailed above, according to the present invention, when a short circuit or overload occurs on the load side in an uninterruptible power supply using a step-up chopper, it is possible to stop the equipment or switch to an auxiliary power supply. Appropriate and reliable protective operations can be performed without causing damage.

Even with respect to the motor starting current and transformer inrush current, current limiting operation can be performed without using a current limiting resistor, and smooth starting and closing can be performed by soft start operation.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the configuration of an apparatus for implementing the method of the present invention, and FIGS. 2 and 3 are time charts showing different embodiments of the method of the present invention performed by the apparatus of FIG. 1. , FIGS. 4(a) and 4(b) are flowcharts for explaining the present invention in detail, FIG. 5 is a block diagram showing a second configuration example of an apparatus implementing the present invention, FIG. 6,'; Figure XX7 is a block diagram showing one different circuit configuration example of a known uninterruptible power supply. 1... AC power supply, 2... Rectifier, 3... Storage battery,
5... Boost chopper, 6... Inverter, 7...
Load, 9゜22... Switch, 10.24... Current transformer, 11... Constant voltage control circuit, 12... Current control circuit, 14... Logic sequence circuit, 15... Overload Current detection circuit, 16a, 16b...voltage detector, 17
... Charging control circuit, 18.19... Analog switch, 21... Comparator, 23... Discharging resistor,
KS... Rectifier output voltage, VB... Storage battery voltage, A
s...Inverter output voltage, 88...Inverter output current. Applicant's agent Kiyoshi Inomata Figure 2 Figure 3 Figure 4 (α)

Claims (1)

[Claims] A main circuit that matches a DC voltage obtained from an AC power supply via a rectifier with a storage battery voltage and supplies power to a load via a step-up chopper and an inverter, and a main circuit that makes the output voltage of the inverter constant. an uninterruptible power supply comprising: a constant voltage control circuit that controls the boost chopper; and a current control circuit that controls the rectifier or the boost chopper so as to limit the output current of the inverter to a predetermined limit current value or less. In the overload protection operation method, when a short circuit accident or an overload occurs on the output side of the inverter, the output current of the inverter is suppressed to below the limit current value by turning off the inverter, and the rectifier and The step-up chopper is turned off, the storage battery is disconnected, and each set value of the constant voltage control circuit and the current control circuit is reduced to a minimum value, and after a predetermined period of time, the inverter is turned on and at least the current control circuit is turned on. Gradually increasing the set value to gradually increase the output voltage of the inverter via the rectifier or step-up chopper, and supplying a current below the limit current value to the load until the short circuit or overload is removed. , after the short circuit accident or overload is removed,
An overload protection operation method for an uninterruptible power supply, characterized by introducing the storage battery.