JPS64898B2 - - 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. 11, 12 are conversion transformers, 21,
22 is a power conversion device consisting of a thyristor valve;
31 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 sequential converter, the other end is used as an inverse converter, and the current command value Idp is on the forward converter side.
is given, and Idp - ΔI, which is obtained by subtracting the current margin ΔI, is given to the inverter side to perform constant current control. 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 steady state operating point is point P, which is made stable by making the current setting value given to the inverse converter side smaller than that of 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, there is a possibility that the current margin mentioned above will disappear when the current setting value suddenly changes. be. Conventionally, in order to compensate for this transmission delay, the current setting value signal on the transmitting side is delayed for a certain period of time before being transmitted to the control device 4.
Countermeasures are being taken, such as inputting information into

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

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, 6 is a current set value generated by a current set value generation circuit, 7 is a sample hold circuit for transmission, 8 and 9 are transmission devices, and 10 is a 2
This circuit selects the minimum value of two inputs, and may be a circuit composed of two diodes as shown in the figure, for example. Reference numeral 11 denotes a circuit for selecting the maximum value of two inputs, and for example, it may be a circuit composed of two diodes as shown in the figure. 12 is a contact that is closed during INV operation, 13 is a contact that is closed during REC operation, 14 is a signal used as the current setting value of the own end, and 15 is a signal used as the current setting value of the opposite end.

Next, the operation will be explained using FIG. 4 as well. In order to transmit the current command value Idp6, it is sampled by the sample and hold circuit 7 before being input to the transmission device 8. The sampled signal when the current command value increases or decreases has a step-like waveform as shown in FIGS. 4a and 4b. The signal transmitted to the other end has a waveform delayed by the transmission delay time. The signal transmitted in the opposite direction from the other end has a waveform further delayed by the transmission delay time. Even if the transmission delay time varies somewhat depending on the transmission timing, the time relationship of the waveforms does not change.

Now, considering the case where the own end is in INV operation, 10
The minimum value selection circuit selects the waveform when Idp increases and the waveform when Idp decreases. At this time, the other end is in REC operation and the Idp is changing as shown in the waveform. Therefore, always
The relationship of Idp at the INV end ≦ Idp at the REC end is established,
At the INV end, a signal obtained by further subtracting the current margin ΔI is input to the constant current control device, so the current margin at both ends is always ensured.

Considering the case where the own end is in REC operation, the maximum value selection circuit 11 selects the waveform when Idp increases and the waveform when Idp decreases.
At this time, as mentioned above, the Idp at the REC end is always
The relationship ≧Idp at the INV end is established, and the current margin at both ends is ensured.

Note that in the above embodiment, the signal passed through the sample and hold circuit No. 7 was used as the signal at the own end.
As is clear from FIG. 4, the signal before passing through the sample and hold circuit may be used. Further, although a circuit using diodes as the minimum value selection circuit and maximum value selection circuit is illustrated, it goes without saying that a circuit that selects the maximum value and minimum value by other means may be used.

As described above, according to the present invention, by selecting the minimum or maximum value of the current setting value transmitted and the reply value from the other end and setting it as the current setting value of the own end, a current margin is always ensured and stability is achieved. This makes it possible to drive with ease.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a DC power transmission system, FIG. 2 is a diagram showing the operating characteristics of the DC power transmission system, FIG. 3 is a diagram showing an embodiment of the current setting value control circuit according to the present invention, and FIG.
The figure is a diagram showing the relationship among transmission data, reception data, and reply data. 11 and 12 are conversion transformers, 21 and 22 are power conversion devices, 31 and 32 are DC reactors, 6 is a current setting value, 7 is a sample and hold circuit, 8 and 9 are transmission devices, 10 is a minimum value selection circuit, 11 is a maximum selection circuit, and 14 and 15 are current setting values at each end.
In addition, in the drawings, the same reference numerals indicate the same or opposite parts.

Claims (1)

[Claims] 1. A first transmission device that transmits a current setting value generated at its own end to the other end to control the current of a DC transmission line and uses it as a current setting value of a power conversion device at the other end, and a current setting value at the other end. a second transmission device that transmits the value to the own end; a minimum value selection circuit that selects the minimum value between the output of the second transmission device and the current setting value generated at the second end; It is equipped with a maximum value selection circuit that selects the maximum value between the output of the transmission device and the current setting value generated at the own end, and when the power conversion device at the own end is in forward conversion operation, the output of the maximum value selection circuit is A current set value control device for a DC power transmission line, characterized in that during inverse conversion operation, the output of the minimum value selection circuit is given as a power set value to the power converter at its own end for control.