JPS6066675A - Control circuit of cvcf inverter - Google Patents

Abstract

PURPOSE:To reduce the overcurrent withstand strength of a rectifier by invaliding a current control due to the input current of an inverter when the inverter is overloaded and raising the voltage of a DC intermediate circuit from a floating charging voltage to a uniform charging voltage. CONSTITUTION:When the output current of a thyristor inverter 18 becomes the prescribed value or higher, an overload detector 42 is operated, a normally closed contact 34 is opened to interrupt a detection current signal from a DC current transformer 30, thereby invaliding a current control system for controlling a thyristor rectifier 10, thereby eliminating the limit of the output current of the rectifier 10. Simultaneously, a normally open contact 24 is closed, and a uniformly charging voltage setter 22 is connected to a voltage control system. Accordingly, the voltage of a DC intermediate circuit is raised to the uniform charging voltage which is higher by 10% than the floating charging voltage from a battery 16. Thus, since the DC voltage decreases, the overcurrent withstand strength of the rectifier 10 can be decreased.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a rectifier connected to an AC power source, an inverter that supplies constant voltage constant frequency AC power to an AC load,
The present invention relates to a control circuit for a CvCF inverter comprising the rectifier and a battery connected to a DC intermediate circuit between the inverter.

[Prior art and intermediate points]

In a CVCF inverter, a rectifier is connected to an AC power supply, and the DC output of this rectifier is used to float charge the battery, and the DC power is converted to AC power with a constant frost and pressure constant frequency by an inverter. 1 of the so-called DC intermediate circuit between the inverter and the inverter. The voltage is normally controlled to maintain a constant value, and the current control system constantly monitors the current to protect the rectifier.

FIG. 1 is a circuit diagram showing a conventional CVCF' inverter control circuit. In FIG. 1, AC power from an AC power source is converted into variable voltage DC power by a thyristor regulator DIL device 10 which has a thyristor as a component, and this DC power is smoothed by a DC reactor 12. After ripples are removed by a smoothing circuit including a capacitor 14, the power is converted into constant voltage, constant frequency AC power by a thyristor inverter 18 and supplied to a load.

A DC intermediate circuit 16 is connected to the dual-current intermediate circuit that connects the thyristor rectifier 10 and the thyristor rectifier 18, and is constantly floatingly charged by this DC intermediate circuit voltage. In the event of a power outage, this battery 16 supplies direct current to the thyristor rectifier 10, so that the load of the thyristor inverter 1B is not interrupted.

The voltage of this DC intermediate circuit is detected by the insulated voltage detector, which is 20, and the deviation value between this detected voltage signal and the set voltage signal, which is set by the pressure setting device, is 21. It is calculated at point 25, and the calculation result is PI
The voltage is input to a voltage regulator 26 which is a regulator. The output signal of this voltage regulator 26 is given to a firing angle regulator 29 via a signal selector 28, and the output from the firing angle regulator 29 is applied to the thyristor rectifier 101; The output DC voltage, ie the DC intermediate circuit voltage, is the floating charge kt4. Pressure setting device 2
On the other hand, a DC current transformer 30 is installed on the DC input side of the iris inverter 18, and the detected current signal detected by the DC current transformer 30 and The deviation value between the setting from the current setting device 31, which sets the upper limit of the input current of the thyristor inverter 18, and the current signal is calculated at the addition point 35, and the calculation result is input to the current regulator 36, which is a PI regulator. Ru. The output signal of this current regulator 36 is passed through the signal selector 28 to the firing angle i#! l
lk unit 29.

Here, the signal selector 28 operates so that the signal with a lower level is selected and outputted between the signal from the voltage regulator 26 and the signal from the current regulator 36.
In the figure, the signal selector 28 is shown as independent for convenience of explanation, but in reality, it is often integrated into a circuit with the °C, pressure regulator 26, and current regulator 36. If the polarity of the signal set is as shown in FIG.
When the detected voltage signal and the detected current signal have positive polarity, and the detected current signal applied to the summing point 35 is smaller than the set current signal from the current setting device 31, the current regulator 36 has positive polarity. Therefore, if the DC intermediate circuit voltage is maintained at a predetermined floating charge voltage, the output signal of the voltage regulator 26 will have a lower level. Therefore, the output sum or voltage of the thyristor rectifier 10, that is, the DC intermediate circuit voltage, is controlled by the voltage regulator 26.

On the other hand, the thyristor inverter 1 detected by the DC current transformer 30
When the input current of 8 increases and the detected current signal exceeds the set current signal from the first-class setting device 31, the current regulator 3
6 outputs a negative polarity signal, which has a lower level than the output signal of the voltage regulator 26. Therefore, the signal selector 28 selects and outputs the output signal of the current v4 node 36, so the thyristor rectifier 10 The above detected current is the current setting device 31
current regulator 36 so that the current does not exceed the value set by
The current will be controlled by

As mentioned above, in the conventional CVCF inverter, the voltage setting value when performing voltage control is fixed, and when the input current of the thyristor inverter 180 exceeds the Flr fixed value, it shifts to current control, but the thyristor rectifier The current capacity of the thyristor rectifier 10 must be made larger than the current capacity of the thyristor inverter 18, and the current setting value that limits the current of the thyristor rectifier 10 must be set higher than the current controlled by the thyristor inverter 18. 10 had the disadvantage of requiring a large flow resistance i.

[Giant invention]

To provide a control circuit for a CVCF inverter comprising the inventive rectifier tube, an inverter, and a battery connected between the rectifier and the inverter, which can reduce the excess 1F current resistance of the rectifier compared to the conventional one. With the goal.

[Key points of the invention]

This invention consists of a rectifier, a battery, and an inverter.
In a VCF inverter, when the inverter is overloaded to a predetermined level or more, the current control by the inverter input current is disabled to prevent the rectifier from limiting its output current, and the set value of the DC intermediate circuit voltage is increased. By reducing the current flow in the DC intermediate circuit, the overcurrent of the rectifier can be made smaller than in the past. FIG. 2 is a circuit diagram showing an embodiment of the invention.

In this FIG. 2, there is a Lyris rectifier 10 that converts the CvCF inverter line AC power by 1'' and converts the direct current of 1 pressure into force, a DC reactor 12 and a smoothing capacitor 14 for smoothing the DC output of the thyristor rectifier 10.
, a thyristor inverter 18 that converts smoothed direct current into constant voltage and constant frequency alternating current power, and a patch ')-16 connected to a direct current intermediate circuit located between the thyristor rectifier 10 and the thyristor inverter 18. has been done.

The detected atmospheric pressure signal from the insulation voltage detector 20 that detects the DC intermediate circuit voltage and the set voltage signal from the floating charging voltage setter 21 are input to the voltage regulator 26 via the addition point 25f, and this voltage regulator 26 A control signal that makes the deviation between both voltage signals zero is output, and this control signal is sent to the signal selector 28.
It is applied to the firing angle adjuster 29 through the. In addition, the input current of the thyristor inverter 18 is detected by the DC current transformer 30, and this detected current signal and the set current signal from the current setting device 31 are combined through the addition point 35 to adjust the current! ! The output signal of the current regulator 36 is supplied to the firing angle regulator 29 via the signal selector 28, which selects the signal from the voltage regulator 26 and the signal from the voltage regulator 26. Of the signals from the current regulator 36, selecting and outputting the signal with the lower level is the same as in the conventional example shown in FIG. 1. In the present invention, as shown in FIG. A current transformer 40 for detecting the output current is provided on the output side of the thyristor inverter 18. Thyrist inverter 1
When the thyristor rectifier 1o is under current control because the input current of the thyristor inverter 8 increases above the set current, when the output current of the thyristor inverter 18 exceeds a predetermined value, the overload detector 42 operates. Due to the operation of the overload detector 42, the normally closed contact 34 is opened and the detected current signal from the DC current transformer 3o is cut off. Ineffective use causes the output of the thyristor rectifier 10 to become unrestricted. At the same time, the normally open contact 24 is closed and the equal charging voltage setter 22 is connected to the voltage control system, so that the voltage of the DC intermediate circuit is no longer 1 than the voltage at which the battery 16 is floatingly charged.
Increases to 0% higher uniform light 11L pressure. Since the DC current decreases as the voltage of the DC intermediate circuit increases, the thyristor rectifier 10 can reduce the overcurrent withstand capacity compared to the conventional one.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. In FIG. 3, thyristor rectifier 10, DC reactor 12, smoothing capacitor 14, battery 16, thyristor inverter 18, insulation voltage detector 20, floating charging voltage setter 21, normally open contact 24, summing points 25 and 35
, voltage regulator 26, signal selector 28, firing angle regulator 29
, DC current transformer 30, current setting device 31, normally closed contact 34,
Since the names, operations, and functions of the current regulator 36, current transformer 40, and overload detector 42 are all the same as in the embodiment shown in FIG. 2, their explanations will be omitted.

In FIG. 3, a function generator 23 is provided in place of the voltage setter 22 of the uniform light beam 11 in FIG. This function generator 23 outputs a signal corresponding to the output current of the thyristor inverter 18 as a set voltage signal, so that the overload detector 42 operates, the normally open contact closes, and the function generator 23 is connected to the voltage control system, the clear intermediate circuit voltage is gradually equalized in response to the increase in the output current of the thyristor alternator 18. Since the voltage is increased toward the charging voltage, the voltage change in the DC intermediate circuit becomes smooth.

〔Effect of the invention〕

In this invention, when the inverter output current provided on the output side of the CVCF inverter exceeds a predetermined value,
The current control system controlling the rectifier is disabled, and the voltage of the DC intermediate circuit is increased from the floating charging box voltage to the uniform voltage, and is controlled by the voltage control system. 6. DC in response to the rise in DC intermediate circuit voltage. Because the flow decreases,
Rectifiers can withstand overcurrents smaller than conventional ones.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing control of a conventional CVCF inverter, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a circuit diagram showing a second embodiment of the invention. 10... Zyristor rectifier, 16... Battery, 18... Zyristor inverter, 2
0... Insulated voltage detector, 21... Floating charge voltage setter, 22... Equal light %-pressure setter, 23... Function generator , 26...press Ml! ij unit, 28... Signal selector, 29.
...Ignition angle adjuster, 30...DC current transformer, 31...Current setting device, 36...Jun,
Flow adjustment rice, 40...Current transformer, 42...
Overload detector, 44... Rectifier circuit. Figure 1 Jt) ``Figure 22

Claims (1)

[Claims] a rectifier that converts alternating current power into variable voltage direct current power; an inverter that converts the rectifier direct current output into constant voltage constant frequency alternating current power; and a battery connected to a direct current intermediate circuit that couples the inverter and the rectifier. If the DC intermediate circuit voltage is the floating light of the battery, 1. a voltage regulator that issues a signal to control the rectifier so that the DC intermediate circuit current is equal to or higher than the set current; a current regulator that issues a signal to the rectifier; current detecting means for detecting that the inverter output current is equal to or higher than a predetermined value; and voltage raising means for raising the DC intermediate circuit voltage to a predetermined voltage value higher than the battery floating charging voltage using the output signal of the current detecting means. CVCF inverter control circuit.