JPS64897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling current setting values of both converting stations via a transmission line in DC power transmission.

FIG. 1 shows a configuration diagram of a DC power transmission system to which the present invention is applied. 1, 1' are conversion transformers, 21, 2
2 is a power conversion device consisting of a thyristor valve, 3
1 and 32 are DC reactors, 41 and 42 are control devices, 5 is a transmission device, and 6 is a current setting value.

During normal operation, one end is used as a forward converter, the other end is used as an inverse converter, the current command value Idp is given to the forward converter side, and the current margin ΔI is reduced to the inverse converter side.
Constant current control is performed by giving Idq - ΔI. This current setting value Idp must have the same value at both ends, and is usually used by transmitting the current setting value to the other end through a transmission line such as a micro line or power line carrier.

Figure 2 shows a diagram showing the operating characteristics of a DC power transmission system. The operating point in the steady state is point P, which is made stable by making the current setting value given to the inverse converter side smaller than that on the forward converter side by a current margin ΔI. If this current margin is not always maintained even when the current setting value is changed, as is clear from the figure, there will be no operating point and operation will become impossible. However, since a transmission device is used to send the current setting value to the other end, if this time delay is not taken into consideration,
When the current setting value is suddenly changed, there is a possibility that the above-mentioned current margin disappears.
Conventionally, in order to compensate for this transmission delay, measures have been taken such as delaying the current setting value signal on the transmitting side for a certain period of time before inputting it to the control device 41.

However, in the case of transmission methods such as CDT transmission,
The transmission delay time varies, and it is impossible to change the current setting values at both ends completely at the same time. Further, when a transmission line or a transmission device breaks down, the current setting value signal does not reach the other end, and only the current setting value of the own end is changed, resulting in a loss of current margin.

The present invention has been made to eliminate the above-mentioned conventional drawbacks, and provides a device that can ensure a current margin not only when changing the current setting value but also when a transmission line or transmission device fails. The purpose is to

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In Fig. 3, 7 and 9 are adders that add with the polarity shown, and 8 is a limiter, -K≦input≦K.
In the range of , the output is equal to the input, and if the input is K or more, the output is limited to K, and if the input is -K or less, the output is limited to -K. Reference numerals 10 and 11 are transmission devices, representing a transmission line and a reception line, respectively. 12 and 13 are current setting values output to the control device at each end.

FIG. 4 shows another embodiment of the present invention, in which the same reference numerals as in FIG. 3 indicate the same or corresponding parts. 14 is a limiter which has the characteristic that the output is equal to the input in the range where the input is smaller than K, and limits to K when the input is K or more, and the limiter 15 has the characteristic that the input is -
For ranges greater than K, the output is equal to the input, −K
It has the characteristic of being limited to -K for the following inputs. 16 is a contact that closes during INV operation, 17
is a closed contact during REC operation.

Next, the operation will be explained. In a steady state, Idp at both ends match, and the values of signals 12 and 13 are equal. When Idp6 is suddenly increased in FIG. 3, the signal transmitted by the transmission device 10 is limited to Idpo+K by the effect of limiter 8, where Idp is the current command value before the change. At this time, the current setting value is Idpo+K at the own end, and remains at Idpo at the opposite end. Only after the transmitted signal reaches the other end, the current setting value of the other end becomes Idpo + K.
This data will be sent back. Until it is returned, both ends have the current setting value of Idpo+K. When the return data Idpo+K reaches its own end, limiter 8 will allow (Idpo+K)+K=Idpo+2K to pass through. In this way, the current setting value can be increased while maintaining the difference between the current setting values at both ends within ±K.

If Idp6 suddenly decreases, limiter 8
When reaching the lower limit of , the current set value can be decreased by the same procedure as above while keeping the difference between both ends within ±K.

Next, considering the case where the transmission line or transmission device fails, the limiter range does not change because the reply data received by the transmission device 11 is not updated, regardless of whether the transmission line or the reply line is out of order. , the current set values 12 and 13 at both ends are held between ±K.

To explain another embodiment of FIG. 4,
Decreasing the current setting value of a converter station in INV operation and increasing the current setting value of a converter station in REC operation both work in the direction of increasing the current margin. It is configured so that the current setting value can be changed quickly without any effect.

Although the above embodiment describes a current set value control circuit in a DC power transmission system, it is clear that the present invention can also be applied to other control signals such as a power set value control circuit in a constant power control system having a power margin ΔP.

As described above, according to the present invention, the transmitted value of the current setting value is limited to ±K of the reply data from the other end, so the difference between the current setting values at both ends can be kept within ±K at all times, including when there is a transmission error. It becomes possible to secure a current margin and enable stable operation.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a DC transmission system, FIG. 2 is a diagram showing the operating characteristics of the DC transmission system, FIG. FIG. 4 is a diagram showing another embodiment of the present invention. In the figure, 11 and 12 are conversion transformers, 2
1 and 22 are power converters, 31 and 32 are DC reactors, 6 is a current setting value, 7 and 9 are adders, 8,
14 and 16 are limiters, 10 and 11 are transmission devices,
12 and 13 are current setting values at each end. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A current setting value for controlling the current of the DC transmission line generated at one end of a DC transmission line having power conversion devices at both ends is compared with a current setting value of the power conversion device at the other end. a first adder that calculates the difference between the two;
A limiter that limits the output to a predetermined value or less when the output of the adder is greater than a predetermined value, and a limiter that outputs the output by limiting the output to a predetermined value or less, and adds the output of this limiter to the current setting value of the power converter at the other end to generate a current of the own end. a second adder that receives the current setting value from the other end; a first transmission device that transmits the output of the adder to the other end and uses it as the current setting value; and a second transmission device for supplying the current to the second adder. 2. When the power converter at its own end is in forward conversion operation, the limiter limits the output of the first adder to a predetermined value or less when the output of the first adder has negative polarity and is greater than or equal to a predetermined value. When the power conversion device is in reverse conversion operation, when the output of the first adder is positive and is equal to or greater than a predetermined value, the output is limited to a predetermined value or less. Range 1
A current setting value control device for a DC power transmission line as described in 2.