JPS592530A - Control system for converter - 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 relates to a frequency conversion device or an inverse conversion device for DC power transmission equipment, which is used for switching the lower limit value of the control delay angle in response to various accidents. Regarding control method.

[Technical background of the invention]

Figure 1 shows a schematic diagram of DC power transmission equipment.
The converter 3.li11,1' is connected to a converter 3.1, which is composed of a series-parallel connection of a large number of thyristors, for example, via the converting transformers 2,2'.
3', and converts alternating current into direct current or vice versa by controlling the firing and phase of each thyristor. 4
．． 4' is a smoothing reactor, 5 is a DC transmission line, 6, 6'
is a potential transformer (PT), 7, 7' is a potential current transformer (
CT). The control device in such a main circuit configuration includes constant current control circuits (ACR) s, s', constant voltage control circuits (AVR) 9, 9', and the like.

The constant current control circuit and constant voltage control circuit each have a reference value Id.
The deviation between p, Edp and the detected values Id, Ed is converted into a control voltage Ec, and this control voltage Ee is input to the control voltage selection circuit 10.10'@the control voltage selection circuit 1
o, J6' is for automatically selecting the control system that advances the control angle the most among various controls, and the control voltage Ec selected here is the control voltage limiter 11, 11
The signal is input to the ignition phase control circuit 12°12' which is provided with upper and lower limiters at '. The ignition phase control circuit 1
2゜12' determines the firing phase proportional to the control voltage Ec and outputs the firing command to the thyristor.In the nine AC/DC converters configured in this way, as is well known, the current margin (ΔI) is switched. Accordingly, one is operated as a forward converter under constant current control, and the other is operated as an inverse converter under constant voltage control.

Now, in such a configuration, if the converter 3 is a forward converter and the converter 3' is an inverse converter, during normal operation, the forward converter 3 is connected to the constant current control circuit (hereinafter referred to as A
It is abbreviated as CR. ) 8 and the inverter 3' is
It is operated by the constant voltage control circuit (hereinafter abbreviated as AVR) 9'.

In conventional inverter-side control devices, the control delay angle (hereinafter referred to as
It is abbreviated as α. ) is limited to a range of 90 degrees and 1600 degrees in electrical angle. That is, it is limited to 90'≦α≦1600 by the control voltage limiter 11'. Incidentally, on the forward converter side, the control voltage limiter 11
It is limited to 0≦α≦120°・The reason why it is limited to α≧906 on the inverse converter side is ACR-? AVR
This is to prevent the reverse converter 3' from operating as a forward converter due to a circuit failure such as the above.

[Problems with background technology]

Now, in this state, if a ground fault occurs in the DC transmission line 5, the forward converter 3. And the DC voltage on the reverse converter 3' side becomes almost zero, but regarding the DC current, a current equivalent to the current setting value flows on the forward converter 3 side, but the current on the reverse converter 3' side is almost zero. becomes. Therefore, in such a state, (1) the current of the inverter 3' may be intermittent, leading to deterioration of the thyristor element.

(2) Since an amount equivalent to the current setting value, for example, the rated current, flows through the ground fault point, the arc at the time of a ground fault is difficult to extinguish.

There are other problems. The cause of this is the control voltage limiter 11
This is because ' is α≧90'. That is, when a ground fault occurs, the inverter 3' side selects the output of ACR8' and tries to flow a DC current corresponding to the value obtained by subtracting the current mark 2771 from the current setting value, but the control This is because the voltage limiter 11' limits α so that it does not become less than 9.0 The above explanation is for the case where a ground fault occurs in the DC transmission line, but A similar problem will occur if a ground fault or the like occurs on the AC bus 1.

Therefore, an easily conceivable way to solve the above problem is to eliminate the lower limiter value of the control voltage limiter, but if this is done, as mentioned above, both converters will be in forward converter operation due to circuit failure etc. Suddenly, a large current flows. Also, considering the case where a ground fault or the like occurs on the AC bus 1 of the forward converter 3, in recent years, in order to restart at high speed, when a ground fault occurs on the AC bus 1, an AC undervoltage relay, etc. A method is being considered in which the accident is detected, the forward converter 3 is placed in the bino 4 spare, and the accident is cleared and the system is restarted at high speed. When starting up, there is a risk of large disturbances occurring in the AC system. Because the accident continues,
That is, this is because the DC current during the spare period when the forward converter 3 is running is a value obtained by subtracting the current margin from the current setting value, that is, a value close to the rated current.

[Purpose of the invention]

Therefore, it is an object of the present invention to eliminate such drawbacks, and to solve the problem in the event of a DC transmission line accident.
It suppresses the current flowing to the ground fault point and prevents current interruption in the inverter, and in the event of an AC transmission line fault, it reduces the DC current to suppress disturbances to the AC system when restarting, and further prevents circuit failure. It is an object of the present invention to provide a control method for a converter device to prevent an increase in direct current caused by such factors as much as possible.

[Summary of the invention]

In order to achieve this object, the present invention is characterized in that the control delay angle lower limiter is switched in response to a DC power transmission line fault, an AC power transmission line fault, or the like.

[Embodiments of the invention]

Fig. 2 shows a control voltage limiter circuit showing an embodiment of the present invention, 13e14g15 is an upper and lower limiter circuit, and the upper limit and limit value are all the same value, but for the lower limiter value, for example, 13 is a control delay limiter circuit. Angle α90' equivalent value, 14
is the control delay angle α85' equivalent value, 15 is the control delay angle α70
"This is the equivalent value. Also, 16*17+18 is a switch,
For example, 16 is a switch that is turned on during normal operation and turned off in the event of a DC or AC transmission line accident, 17 is a switch that is turned on only in the event of an AC transmission line accident, and 18 is a switch that is turned on only in the case of a DC transmission line accident. In FIG. 2, the switch 16 is on during normal operation, so the control voltage is controlled by the upper and lower limiter circuit 13.
A limiter is applied at O, that is, due to a failure in the constant voltage control circuit, etc., for example, α=θ.

Even if the control voltage reaches a considerable level, the upper and lower limiter circuit 13 sets the control voltage to α=900, so that no large current flows. Further, when an AC power transmission line accident or the like occurs, the switch 17 is turned on by the accident detection signal, so that the control voltage becomes equivalent to α=850, and the system is operated at the minimum load current. Furthermore, when a DC transmission line fault occurs, the fault detection signal causes switch 18 to be activated.
is turned on, it is possible to flow a DC current close to the rated DC current value with a control voltage of α=700 phase.

In the above explanation, the upper and lower limit limits and the lower limit value of the circuit 14 and 15 were set to values equivalent to α = 850 and α = 700, respectively, but these values are based on the DC transmission line resistance value, minimum load current, or intermittent limit. It goes without saying that the decision is made taking into consideration the current value, etc.@Also, in reality, switches 17 and 18 are not linked to the accident detection signal, but when turning off the switches, there is a slight delay after the accident has been recovered. It is preferable to return it with.

〔Effect of the invention〕

As explained above, according to the present invention, by switching the lower limit value of the control delay angle limiter according to each operation mode during normal operation, during an AC power transmission line fault, and during a DC power transmission line fault, Expanded accidents due to circuit failures, etc. can be prevented.

■ It is possible to suppress the current flowing through the ground fault point in the event of a ground fault in the DC transmission line.

■ In the event of an AC system accident, disturbances to the AC system can be suppressed and a rapid restart can be achieved.

It has a remarkable effect.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a DC power transmission facility to which the present invention can be applied, and FIG. 2 is a block diagram showing only the main parts of the present invention. 1.1'... AC bus, 2,2'... Conversion transformer, 3.3'... Converter, 4-4'... Smoothing reactor 15... DC transmission line, 6 e 6'...Instrument transformer, 7゜7'...Instrument current transformer, 8 m B'・
...constant current control circuit, 9.9'...constant voltage control circuit,
10910'...Control voltage selection circuit, 1lall'.
...Control voltage limiter circuit, 12.12'...Ignition phase control circuit, J s *14*15...Upper/lower limit limiter circuit, 16*17*1B...Switch 0

Claims (1)

[Claims] In DC power transmission equipment equipped with an AC/DC converter that converts AC to DC and DC to AC, the lower limit value of the control delay angle limiter of the converter that is operated in reverse conversion mode should be set in the event of a DC circuit fault or AC circuit fault. A control method for a conversion device characterized by changing each.