JPH0691706B2 - Controller of DC power transmission device for suppressing shaft twist of generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a DC power transmission control device, and particularly to control of a DC power transmission device suitable for suppressing twisting of a generator due to interference between a power generator and DC power transmission. apparatus.

[Conventional technology]

In 1977, a low-frequency shaft torsion resonance phenomenon occurred at a power plant near the forward conversion station of the Scare Butte DC transmission facility in the United States. Taking this opportunity, there is an urgent need to elucidate the shaft torsion resonance phenomenon due to the interference between the DC power transmission and the generator and to study suppression measures. According to the results of the studies so far, it is becoming clear that this phenomenon is caused by the control of the DC transmission system, but regarding the determination of the resonance phenomenon occurrence depending on the system state, the suppression measure of the shaft torsion resonance phenomenon, etc., There are many places to wait for future examination.

FIG. 2 (a) shows a DC power transmission system which is the object of the present invention. In the figure, 1 is a turbine, 2 is a generator, and 3 is a turbine 1.
, 4 is an impedance of an AC transmission line, 51 and 52 are AC / DC converters, 51 is a forward converter that converts AC into DC, and 52 is an inverse converter that converts DC into AC. . 53 and 54 are control devices of the forward conversion device 51 and the reverse conversion device 52, respectively, and I _P is a current command value that commands the transmission power of the DC transmission system, and is given to the forward conversion device and the reverse conversion device, respectively. As is well known, the inverse converter has a current command value which is smaller than I _P by a current margin ΔI.
The current command value of the inverse conversion device 52 is given by

FIG. 2 (b) shows a detailed block diagram of the control devices 53 and 54. 501 is an adder that takes the difference between the current command value I _P (I _P −ΔI is given as the command value in the control circuit of the inverse converter as described above) and the detected value I _f of the actual current flowing in the DC transmission system. , 502 are operational amplifier circuits, and 501 and 502 constitute a constant current control circuit. 503 is a constant margin angle control that calculates a control angle command value corresponding to the margin angle required for the converter to perform stable commutation from I _f and the consideration value E _f of the AC voltage applied to the converter. A circuit, 504 is a signal selection circuit that selects an optimum value from the outputs of the operational amplification circuit 502 and the constant margin angle control circuit 303, and 505 is a phase control that outputs a pulse according to the magnitude of the signal selected by 504. FIG. 2C shows the relationship between the input signal (control signal) and the phase angle of the output pulse in the circuit. In the signal selection circuit, a constant current control circuit is normally selected in the forward conversion device, and a constant margin angle control circuit is selected in the inverse conversion device to control each conversion device.

Note that, as a device related to this kind of device, for example, "HV
DC SYSTEM CONTROL FOR DAMPING OF SUBSYNdronus.osci
llations.IEEE Trans.Vol PAS-101 No. 7.1982 ”.

[Problems to be solved by the invention]

In such a system, if an accident occurs in the AC transmission line or the DC transmission line and the electric torque of the generator is excessive, the generator accelerates and the frequency of the AC system increases. However, in a DC power transmission system, generally, constant current control is usually performed, so that the remainder of the electric torque is applied to the shaft connecting the generator and the turbine as stress, and the shaft is twisted. Also, when the electric torque of the generator is insufficient due to an accident, stress is similarly applied to the shaft. If this stress is great, a shaft accident will result in a serious accident.

An object of the present invention is to provide a DC power transmission control device capable of stable power transmission in a steady and transient manner, except for the above-mentioned problems of the conventional art.

[Means for Solving Problems] One of the causes of the shaft twist phenomenon due to the interference between the generator and the DC transmission system is that the DC transmission system is normally operated by constant power control. That is, because of the constant power control, the electrical control command of the generator (= electrical torque change with respect to the change of the generator's angular velocity) becomes zero or negative, and transient vibration of the generator cannot be suppressed. It vibrates at the frequency of and causes an unstable phenomenon. As a countermeasure against this, as a result of eigenvalue analysis between the generator and the DC transmission system, a signal corresponding to the change in the angular velocity of the generator (further, it is better to add a signal corresponding to the change in the phase angle of the generator, which is the integral value) If the DC transmission power is controlled by the state feedback of
The electrical control coefficient of the DC transmission system becomes positive, and even if the electrical torque of the generator is excessive or insufficient, transient vibration is attenuated and the shaft twist phenomenon does not occur. Also, since the optimum coefficient value (gain) of the state feedback is changed depending on the DC transmission power,
The coefficient value is changed according to the signal corresponding to the DC transmission power.

[Action]

By correcting the current command value of the constant current control circuit with a signal obtained by multiplying the state quantity of the power transmission system by a coefficient (gain), the electrical control coefficient becomes positive and the shaft twist phenomenon does not occur.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Since the same numbers as in the previous figure indicate the same things, different ones will be explained. In FIG. 1 (a), 55 is a voltage transformer for detecting an AC voltage connected to the generator 2, and 56 is a voltage transformer. The current command value creating circuit creates a new current command value I _P ′ from the detected value E _W and the current command value I _P. This output is guided to the control device 53.

FIG. 1B shows a detailed control block diagram of the inside of the current command value generation circuit 56. In the figure, 506 is an angular velocity change detection circuit that detects a signal corresponding to the magnitude of the angular velocity of the generator from the AC voltage detection value E _W , 507 is an amplifier that multiplies the detected value of 506 by a set value, and 508 is In the adder that adds the above-mentioned current command value I _P and the output of the amplifier 507, this output becomes the new current command value I _P ′ and is guided to the adder 501. Explaining the operation of this control device, when an accident occurs in the AC transmission line (or DC transmission line) and the electric torque of the generator is excessive and the generator accelerates, the output of the angular velocity change detection circuit 506 becomes large. This value is multiplied by the specified gain and added to the current command value I _P. Therefore, in the DC transmission system, the transmission power increases by an amount proportional to the increase in the angular velocity of the generator, and the surplus electric torque of the generator is absorbed. Therefore, no stress is applied to the shaft that connects the generator and the turbine. Conversely, if the electrical torque of the generator is insufficient due to an AC transmission line accident, the generator will decelerate and the output of the angular velocity detection circuit 506 will decrease, so the DC transmission power will decrease and the insufficient electrical torque of the generator will occur. To make up for. Therefore, no stress is applied to the shaft that connects the generator and the turbine.

Another embodiment of the present invention is shown in FIG. FIG. 3 shows an apparatus in which a status feedback corresponding to the change of the phase angle of the generator is further introduced to the current command value of the DC transmission system described in FIG. Since the same numbers as in the previous figure represent the same things, a different new one will be described.509 is an integrator that integrates the output of the angular velocity change detection circuit 506, and 510 is the integrator output. It is an amplifier that multiplies the value by the coefficient. The output of the amplifier 510 is summed is directed to the adder 508 to the current command value I _P, create a new current command value I _P '.

According to this control device, the detected value of the angular velocity change is integrated, and the current command value I _P of the DC transmission system is changed also by the signal corresponding to the change of the phase angle of the generator. The electric torque fluctuates and the angular velocity of the generator does not change significantly, but when the phase angle changes, the transmission power of the DC transmission system changes in proportion to the amount of change. Therefore, the finer control of the DC power transmission system can be performed as compared with the above-described embodiment, and the twisting of the shaft connecting the generator and the turbine can be prevented.

FIG. 4 shows still another embodiment of the present invention. Fourth
The drawing introduces a circuit in which the gain of the amplifier of the control device described in FIG. 1 is changed according to the DC transmission power. This is because the feedback gain of the optimum state quantity (in this case, the signal corresponding to the angular velocity and the phase angle of the generator) changes depending on the DC transmission power.
In the figure, the same numbers as in the previous figure represent the same things, so let us explain about different things.511 is a variable gain amplifier in which the gain of the amplifier changes by the signal COM corresponding to the magnitude of the DC transmission power. is there. As the signal COM, the detected value of the actual DC transmission power, the current command value I _P , the detected current value
I _f , whichever is fine. Calculation results show that the signal CO
As for the relationship between the magnitude of M and the amplifier gain, as shown in the schematic diagram of FIG. 5, the gain may be small when the DC transmission power is large, that is, when the COM is large, and may be large when the COM is small.

Incidentally, although FIG. 4 shows the one based on the embodiment of FIG. 1, it is clear that this idea can be applied to the one based on the embodiment of FIG. 3 as well, so a detailed control block diagram is omitted. is doing.

〔The invention's effect〕

As described above, according to the present invention, the unstable phenomenon due to the interference between the generator and the DC transmission system can be prevented by adding a simple control circuit, so that the energy of the generator can be stably transmitted as DC.

[Brief description of drawings]

FIG. 1 is an explanatory view of a DC power transmission facility equipped with a control device for suppressing shaft twist of a generator of the present invention, and FIG. 2 is an explanatory view of a DC power transmission system to which the present invention is directed, FIGS. FIG. 4 is a diagram showing a control device according to another embodiment of the present invention, and FIG. 5 is a characteristic diagram of the variable gain amplifier in FIG. 1 ... Turbine, 2 ... Generator, 3 ... Shaft, 4 ... AC transmission line impedance, 51, 52 ... AC converter, 53, 54 ... Control device, 55 ... Voltage transformer, 56 ... DC command value creation circuit, 501,50
8 ... Adder, 502 ... Operational amplifier, 503 ... Constant margin angle control circuit, 504 ... Signal selection circuit, 505 ... Phase control circuit, 506 ... Angular velocity detection circuit, 507, 510 ... Amplifier, 509 ... Integrator, 511 ...
Variable gain amplifier.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsukushi Hara 1-3-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Within Tokyo Electric Power Co., Inc. (72) Hiroo Konishi 4026 Kujicho, Hitachi City, Ibaraki Japan Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Hisao Amano 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (56) Reference JP 57-211937 (JP, A) JP 58- 198120 (JP, A) JP-A-59-53025 (JP, A)

Claims (3)

[Claims] Claim: What is claimed is: 1. Control of a DC power transmission device of a power transmission system for transmitting rotation of a turbine to a generator via a shaft to generate electric energy and transmitting the electric energy generated by the generator to a load place by DC power transmission. In the device, by correcting the current command of the constant current control circuit with a signal obtained by multiplying a signal corresponding to a change in the angular velocity of the generator and the turbine as a state quantity of the transmission system or a signal corresponding to the change, a shaft between the turbine and the generator. A controller for a DC power transmission device for suppressing shaft twist of a generator, characterized in that it suppresses the occurrence of twist. 2. The state quantity of the power transmission system according to claim 1, in addition to a signal corresponding to a change in the angular velocity of the generator and the turbine or a signal corresponding thereto, a phase angle of the generator or a signal corresponding thereto. A control device for a DC power transmission device for suppressing shaft twist of a generator, characterized by being used. 3. A direct current for suppressing shaft twist of a generator according to claim 1 or 2, wherein a coefficient value for multiplying a signal by a coefficient is changed according to transmission power of direct current transmission. Control device for power transmission device.