JPH0213532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current setting value control device for changing the current setting value of a DC power transmission system, for example, when starting or stopping the system.

Conventionally, there has been a current setting value control device having the configuration shown in FIG. In the figure, 1 and 2 are conversion transformers, 3 and 4 are AC/DC converters, 5 and 6 are DC reactors, 7 and 8 are DCCTs, 9 is a current command setter, 10 and 11 are adders, 12 and 13 It is assumed that only one of 12 and 13 is closed in the current margin setting device. 14 and 15 are ignition phase control devices including constant current control, and 16 and 17 are transmission devices that transmit the current command value to the other end.

Next, the operation will be explained. Current command setter 9
The current command value I _F set in is transmitted not only to the own end but also to the other end via transmission devices 16 and 17, and added to adders 10 and 11, respectively. Further, in response to a signal specifying whether to operate the forward converter or to operate the reverse converter, only one of the contacts 12 and 13, which is to be operated as the reverse converter, is closed and the current margin ΔI is subtracted.
The outputs of the DCCTs 7 and 8 are further input with negative polarity to the adders 10 and 11, and the firing phases of the thyristor valves are controlled by constant current control devices 14 and 15.

The current setting value I ^* changes as shown in Fig. 3a when starting/stopping or when changing the current command value. At this time, the current setting value I _REF = I _F - ΔI on the inverse converter side is smaller than that on the forward converter side by the current margin, so the constant current control system does not operate, and only the constant current control system on the forward converter side operates. A DC transmission current is determined. The current setting value on the inverter side only exists for backup purposes in the event of an AC voltage drop or a fault in the DC transmission line.

However, due to a failure in the transmission device or line, the current command value on the forward converter side is not updated during startup, and the current setting value on the inverse converter becomes larger than that on the forward converter side. If the current command value is raised locally at each end, the same result will occur due to the difference in time constants of the control systems of both converting stations. As a result, the predetermined forward converter-inverse converter cannot be operated.

The present invention has been made in order to eliminate the drawbacks of the conventional ones as described above, and when changing the current setting value on the inverter side, the DC transmission current smoothly changes to the vicinity of the current setting value. After checking this, change the current command value on the inverter side, and in particular, let it evacuate to near zero immediately after starting the current setting value on the inverter side, and the DC transmission current will increase to around the set value and go smoothly. After detecting that the converter is activated, the current command value on the inverter side is increased.

In addition, in the case of a stop, the current command value on the reverse converter side is set to zero, so that the current command value on the forward converter side is always larger than that of the reverse converter, thereby preventing operation failure due to insufficient current margin. The purpose is to provide a set value control circuit.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, the same reference numerals as in FIG. 1 indicate the same or equivalent parts, 18 and 19 are contacts that close when the forward converter is operating, and 20 and 21 are contacts that are closed when the reverse converter is operating. , 22 and 23 are adders that add with the polarity shown in the figure, 24 and 25 are detectors that detect the rise of the DC transmission current, 26 and 27 are their contacts, and 28 and 29 are forced to zero when stopped. This is a switch for changing the current.

FIG. 3 is a diagram for explaining temporal changes in the current setting value, in which a shows a conventional method and b shows a method according to an embodiment of the present invention.

Here, conventionally, the current command value at the time of starting and stopping is gradually increased or decreased while maintaining a constant value (current margin) between the forward converter and the inverse converter. On the other hand, in one embodiment of the present invention, at startup, the current command value on the forward converter side is first raised, and after confirming that the DC line current flows, the current command value on the inverse converter side is raised. When stopping, immediately lower the current command value on the reverse converter side to near zero, so that no matter what pattern the current command value on the forward converter side decreases, it will not fall below that on the reverse converter side. ing.

Next, the operation when the converter 3 is in forward conversion operation and the converter 4 is in reverse conversion operation will be described. Since the contact 18 is closed at the converter station where forward converter operation is being performed, the current changes according to the command value from the current command setter 9, similar to the conventional method shown in FIG. Adder 23 at a converter station performing inverse converter operation
Although the current margin ΔI is subtracted, it is not input to the adder 11 until the DC current value rises to near the command value by the current detector 25. When it rises to near the command value, contact 27 closes and Iref
Input −ΔI to the adder. When stopping next time, the switch 29 is changed and the zero current command value is forcibly set. By doing this, a relationship as shown in FIG. 3b is obtained, and the current margin will not be lost due to a failure of the transmission device or line.

It is clear that the same control can be performed when converter 3 is in reverse conversion operation and converter 4 is in forward conversion operation.

In the above embodiment, only the case of starting and stopping has been described, but it goes without saying that the present invention can also be applied to cases where the current command value is increased or decreased. Further, the present invention is intended to prevent insufficient current margin on the inverse converter side due to malfunction in current setting adjustment on the forward converter side when changing the current setting value. Therefore, when the current command value is steady, a predetermined current margin is secured, but if the transmission device or line breaks down and the current command value itself becomes abnormal, the current setting according to the present invention Unlike abnormalities when changing values, this is protected by a separate failure detection circuit.

As described above, according to the present invention, when changing the current setting value, the current command value on the inverter side is not input until the DC current reaches a predetermined value, and is immediately set to zero when the DC current is stopped, thereby preventing insufficient current margin. It is possible to prevent the vehicle from becoming inoperable due to

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional configuration, FIG. 2 is a diagram showing an embodiment of the current setting value control device of the present invention, and FIG.
The figure is a diagram showing temporal changes in the current setting values of the forward/inverse converter using the conventional device and the device of the present invention. 1, 2... Conversion transformer, 3, 4... AC/DC converter, 5, 6... DC reactor, 7, 8...
DCCT, 9...Current command setter, 10, 11, 2
2, 23... Adder, 12, 13... Current margin setter, 14, 15... Constant current control circuit, 1
6, 17...transmission device, 18, 19, 20, 21
... Contact, 24, 25 ... Current detector, 26, 2
7... Current detector output contact, 28, 29... Stop signal switch. In addition, in the figure, the same reference numerals are the same,
or a corresponding portion.

Claims (1)

[Claims] 1. A current command setter that generates a current setting value for the DC transmission line, a first computing unit that subtracts a current margin from the current setting value, and an output of the first computing unit and the detected current of the DC transmission line. A second arithmetic unit that compares the values and a second arithmetic unit that detects the current of the DC transmission line when the current setting value is varied and detects the current value when the current value rises and reaches a predetermined value. a current detector that closes the contact of the DC transmission line; a constant current control circuit that controls the firing of the inverter of the DC transmission line in accordance with the deviation output of the second computing unit; A current setting value control device for a DC power transmission line, comprising means for forcibly setting the output of the first computing unit to zero.