JPH04289741A - Switch controlling circuit for straightforward by-pass circuit - Google Patents

Abstract

PURPOSE:To eliminate a difficulty in switching operation from a power converting device to a straightforward by-pass circuit by using a second set value added with a signal which compensates a quantity of change in rated voltage as a new second set value even if a voltage in the straightforward by-pass circuit fluctuates. CONSTITUTION:In this circuit, a straightforward voltage detecting transformer 21 is installed to detect a voltage of a straightforward by-pass circuit and the voltage detected by the transformer 21 is inputted into a correction voltage generating circuit 22. The correction voltage generating circuit 22 outputs a correction signal which corrects a difference between the rated voltage and the detected voltage and a calculator 23 adds the correction signal to a second set value set by a straightforward current setting device 15. The adding result of this calculator 23 is inputted into a straightforward current detector 16 as a new set value. By comparing the new set value with a current detected by a straightforward-side current transformer 14, the straightforward by-pass circuit is prevented from being affected by the fluctuation of voltage.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching control circuit for a direct bypass circuit when supplying alternating current power to a load from either a power conversion means or a direct bypass circuit.

0002

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional switching control circuit for power conversion means having a direct feed bypass circuit. In FIG. 3, after AC power from an AC power supply 2 is rectified into DC by a rectifier 3, it is converted back into AC by an inverter 4 as a power conversion means, and this AC power is passed through an AC switch 5 and a circuit breaker 6. is supplied to load 7. By the way, since the rectifier 3 and the inverter 4 are composed of semiconductor elements, if an excessive current exceeding the rated value flows, they will be damaged in a short period of time. Therefore, a direct bypass circuit is provided in parallel to the circuit of these rectifier 3 and inverter 4,
If an abnormality occurs in the load 7 and excessive current flows, the AC switch 5 switches the circuit, and the circuit is configured such that AC power from the AC power source 2 is directly supplied to the load 7 via a direct bypass circuit. Although the illustration is simplified, the AC switch 5 actually consists of an inverter-side thyristor 5A, which is a thyristor connected in anti-parallel, and a direct-feed-side thyristor 5B, which is also a thyristor connected in anti-parallel. By opening one side and closing the other at the same time in response to a signal, the circuit can be switched without interruption.

The switching operation of the circuit is as follows. That is, when the inverter side thyristor 5A is closed and the direct feed side thyristor 5B is open and the inverter 4 is supplying AC power to the load, the first set value set by the inverter current setting device 12 (for example, the rated value of the inverter 4) When the inverter side current transformer 11 detects a current higher than (current value),
Inverter current detector 13 consisting of a comparator
operates and issues a switching signal to the switch operation circuit 17, so the command from the switch operation circuit 17 opens the inverter side thyristor 5A and at the same time closes the direct feed side thyristor 5B, and no AC power is supplied to the load 7. In the event of a power outage, inverter 4 switches to the direct feed bypass circuit. In this state, if the current value detected by the direct current transformer 14 decreases below the rated current value of the inverter 4, it is safe to use the inverter 4 to supply power.
6 issues a switching signal to the switch operation circuit 17, the direct feed side thyristor 5B is opened, the inverter side thyristor 5A is closed, and the inverter 4 supplies power to the load again. That is, the second
The set value may be set to the rated current value of the inverter 4 similarly to the first set value. However, if the values are set to the same value, fluctuations will occur in the operation, so the second set value is set to a value slightly smaller than the first set value.

0004

It is now assumed that when the output voltage of the inverter 4 is the rated value V and the impedance value of the load 7 is Z, the inverter 4 is flowing the rated current value I to the load 7. If load 7 fails and its impedance value decreases to 83% of the rating, inverter 4
The current becomes 120% of the rated value, but since this value exceeds the first set value, the power source is naturally switched to the direct feed bypass circuit side. By the way, the direct bypass circuit is AC power supply 2.
That is, since it is directly connected to the commercial power supply, voltage fluctuations cannot be avoided. Therefore, when the power supply is switched to the direct feed bypass circuit side, the direct feed bypass circuit voltage is 2
If the current value has increased by 0%, even if the fault in the load 7 is recovered and its impedance value returns to the original value Z, the current value detected by the direct current transformer 14 is set by the direct current setting device 15. higher than the second setting value (120% of rating)
), the switch operation circuit 17 does not output a command to switch the power source to the inverter 4 side. That is,
Even though the failure of the load 7 is recovered and the operation of the inverter 4 can be restarted, a problem occurs in which the power source is not switched. In addition, if the direct feed bypass circuit voltage is lower than the rated value, a failure occurs in which the impedance value of the load 7 decreases as described above, and when the power source is switched from the inverter 4 to the direct feed bypass circuit side, the load 7
Even though the fault has not been recovered, only a current smaller than the rated current of the inverter 4 (that is, a current smaller than the second set value) flows through the direct feed bypass circuit, so the direct feed current detector 16 is operated by the switch. A switching signal is output to the AC switch 5 via the circuit 17, and the AC power to the load 7 is again supplied by the inverter 4. However, if the load 7 is still out of order, a current greater than the first set value set by the inverter current setting device 12 flows through the inverter 4, so the AC switch 5 is switched to the direct bypass circuit side again. That is, a problem arises in that switching between the inverter 4 and the direct feed bypass circuit is repeated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent the switching operation between the power conversion means and the direct feed bypass circuit from being hindered due to load failure even if the voltage of the direct feed bypass circuit fluctuates. be.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the switching control circuit of the present invention includes a power conversion means for supplying AC power to a load, and a direct transmission means for supplying AC power from a commercial power source to the load. a bypass circuit, a circuit switching means for selecting either the power conversion means or the direct bypass circuit to connect the load to the power conversion means; and if the current from the power conversion means to the load exceeds a first set value, the power conversion a switching operation means for emitting a switching signal from the direct feeding bypass circuit to the power conversion means, and generating a switching signal from the direct feeding bypass circuit to the power conversion means when the current flowing from the direct feeding bypass circuit to the load becomes equal to or less than a second set value; In the apparatus, there is provided a direct feed voltage detection means for detecting the voltage of the direct feed bypass circuit, a correction signal generation means for outputting a signal for correcting the difference between the detected voltage and the rated voltage, and a correction signal generating means for outputting a signal for correcting the difference between the detected voltage and the rated voltage, and a correction signal generating means for outputting a signal for correcting the difference between the detected voltage and the rated voltage, or a dividing means for calculating the ratio between the direct feed bypass circuit detection voltage and the rated voltage, and a value obtained by multiplying the output of the dividing means by the second set value as a new second set value. and a multiplication means for setting a set value.

[0007]

[Operation] This invention detects how much the voltage fluctuation of the direct feed bypass circuit is with respect to the rated voltage, and adds a signal to compensate for this fluctuation to the second set value and generates a new signal. The voltage fluctuation of the direct feed bypass circuit can be controlled by setting the second set value or by determining the voltage fluctuation rate of the direct feed bypass circuit and multiplying the second set value by this voltage fluctuation rate as the new second set value. This eliminates the influence of the above, so that there is no problem in switching between the power conversion means and the direct feed bypass circuit.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a first embodiment of the present invention. Inverter side current transformer 11, inverter current setter 12, inverter current detector 13, direct feed side current transformer 14, direct feed current setter 15, direct feed current detector 16, and switch operation circuit 1
Since the name, purpose, and function of circuit 7 are the same as those of the conventional circuit described in FIG. 3, their explanation will be omitted.

In the first embodiment circuit shown in FIG. 1, a direct voltage detection transformer 2 is used to detect the voltage of the direct bypass circuit.
1 is provided, and this detected voltage is input to the correction voltage generation circuit 22. Since the correction voltage generation circuit 22 outputs a correction signal for correcting the difference between the rated voltage and the detected voltage, the adder 23 applies this correction signal to the second setting value set by the direct current setting device 15 to add. This adder 2
The direct current detector 16 uses the addition result of step 3 as a new setting value.
By inputting the current into the current and comparing this with the current detected by the direct feed side current transformer 14, the influence of voltage fluctuations in the direct feed bypass circuit can be removed.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. The names, uses, and functions of the side current transformer 11, inverter current setting device 12, inverter current detector 13, direct feed side current transformer 14, direct feed current setting device 15, direct feed current detector 16, and switch operation circuit 17 are shown in the figure. Since this is the same as the case of the conventional circuit described in Section 3, a description thereof will be omitted.

In the second embodiment circuit shown in FIG. 2, a direct voltage detection transformer 2 is used to detect the voltage of the direct bypass circuit.
1 is provided in the same manner as in the first embodiment circuit described above, but in this second embodiment circuit, the above-mentioned detected voltage is divided by the rated voltage set by the reference voltage setting device 31 in the divider 32. By doing so, the ratio between the two is calculated. Next, the multiplier 33 multiplies the calculation result of the divider 32 by the second setting value set by the direct current setting device 15, and uses this multiplication result as a new setting value for the direct current detector 16. This makes it possible to eliminate the influence of voltage fluctuations in the direct bypass circuit.

0012

[Effects of the Invention] According to the present invention, in a circuit configured to switch to a direct bypass circuit when an overcurrent occurs in the power conversion means supplying AC power to a load, and to continue supplying power to the load without interruption. By configuring the control circuit to remove the effects of voltage fluctuations even when the direct feed bypass circuit voltage fluctuates, even if the direct feed bypass circuit voltage differs from the rated value, the direct feed bypass circuit can be removed from the power conversion means. It is possible to achieve the effect that the switching operation to the circuit and the switching operation from the direct feed bypass circuit to the power conversion means can be performed appropriately and smoothly.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

[Fig. 2] A circuit diagram showing a second embodiment of the present invention.

[Fig. 3] A circuit diagram showing a conventional switching control circuit of a power conversion means equipped with a direct feed bypass circuit.

[Explanation of symbols]

2 AC power source as commercial power source 4 Inverter 5 as power conversion means
AC switch 5A Inverter side thyristor 5B Direct feed side thyristor 7 Load 11 Inverter side current transformer 12 Inverter current setting device 13 Inverter current detector 14 Direct feed side current transformer 15 Direct feed current setting device 16 Direct feed current detector 17 Switch operation circuit 21 Direct feed Voltage detection transformer 22 Correction voltage generation circuit 31 Reference voltage setter 32 Divider 33 Multiplier

Claims (2)

[Claims] 1. A power conversion means for supplying alternating current power to a load, a direct bypass circuit for supplying alternating current power from a commercial power source to the load, and a power conversion means for selecting either the power conversion means or the direct supply bypass circuit. a circuit switching means connecting the load to the load; and a circuit switching means for connecting the power converting means to the load;
If the set value is exceeded, a switching signal is issued from the power conversion means to the direct feed bypass circuit, and when the current from the direct feed bypass circuit to the load falls below the second set value, a switch signal is issued from the direct feed bypass circuit to the power conversion means. A device comprising: a direct feed voltage detection means for detecting the voltage of the direct feed bypass circuit; a correction signal generating means for outputting a signal to correct the difference between the detected voltage and the rated voltage; A switching control circuit for a direct feed bypass circuit, comprising: an addition means for adding a correction signal to the second set value. 2. A power conversion means for supplying alternating current power to a load, a direct bypass circuit for supplying alternating current power from a commercial power source to the load, and a power conversion means or direct bypass circuit for selecting the power converting means or the direct supply bypass circuit. a circuit switching means connecting the load to the load; and a circuit switching means for connecting the power converting means to the load;
If the set value is exceeded, a switching signal is issued from the power conversion means to the direct feed bypass circuit, and when the current from the direct feed bypass circuit to the load falls below the second set value, a switch signal is issued from the direct feed bypass circuit to the power conversion means. A device comprising: a direct feed voltage detection means for detecting the voltage of the direct feed bypass circuit; a dividing means for calculating a ratio between the detected voltage and the rated voltage; 1. A switching control circuit for a direct feed bypass circuit, comprising: multiplication means for setting a new second set value to a value multiplied by a second set value.