JPS61102124A - Frequency controller for direct current transmission system - 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 control device for controlling a power plant side AC bus frequency to a constant value in a DC power transmission system.

[Technical Background of the Invention] In order to transmit large amounts of power over long distances from power plants that are installed at power plants located far from the load center, such as geothermal power plants, it is necessary to improve system safety and reduce transmission line installation costs. Due to the problem
Since DC power transmission is more advantageous than AC power transmission, DC power transmission has been adopted in many countries. When direct current power transmission is adopted, the generator is asynchronous with the load side, so the generator frequency tends to fluctuate due to fluctuations in the system status, etc. This fluctuation in the generator frequency is not only unfavorable for the operation of the auxiliary equipment in the power plant, but also when the width of the frequency fluctuation becomes large, a protection relay for stopping the generator is activated.

[Problems with the Background Art] Therefore, in the past, in order to control this fluctuation in the generator frequency, the AC bus frequency on one power station side was compared with a reference frequency, and the DC transmitted power was controlled based on the deviation. However, according to such a method, control is performed to return the frequency to the reference frequency only after frequency fluctuation occurs.

There was a slight time delay in the response speed, which was a problem that affected the power plant side.

[Object of the Invention] The present invention suppresses frequency fluctuations even when some kind of abnormality occurs in one of a plurality of DC transmission systems and the transmitted power of that DC transmission system decreases.

The purpose of the present invention is to provide a frequency control device for DC power transmission that can maintain stable system conditions.

[Summary of the Invention] Therefore, the present invention is characterized in that the power transmission command from the abnormal DC power transmission system is distributed to the normal DC power transmission system, thereby balancing the generated power and the transmitted power without time delay. It is said that

[Embodiment of the Invention] Fig. 1 shows a configuration diagram of a DC power transmission system according to an embodiment of the present invention, in which a synchronous generator l is connected to an AC bus on the power plant side, that is, on the mountain side, via a generator circuit breaker 2. Connected to mother a3. The mountain side busbar 3 is connected to forward converters 6A, 6B, which are composed of a large number of thyristors connected in series and parallel, via converter circuit breakers 4A, 4B and converter transformers 5A, 5B. The forward converters 6A, 68 convert AC power into DC power, and control the DC transmitted power by controlling the firing phase of each thyristor. The power converted to DC by the forward converters 6A and 6B is transferred to a smoothing reactor 7A,
7B, DC transmission line 8A, 8B, flat sliding axle 9A,
It is converted back into AC power via inverter +OA and IOB via 9B. The power converted into AC by the inverse converter 10A and IOC reaches the load-side AC bus, that is, the claw-side bus 13, via converter transformers 11A, IIB, and converter circuit breakers 12A, 12B.

In the DC power transmission system configured in this manner, the frequency control device includes a frequency detector 14. Reference frequency generator 15
, a computing unit 16, a controller 17, and a distribution circuit 18. The mountain side bus frequency f detected by the frequency detector 14 is inputted to the arithmetic unit 6 together with the reference frequency fθ which is the output of the reference frequency generator 15. Arithmetic unit 16 outputs frequency deviation Δf, which is input to controller 17 . The controller 17 inputs the frequency crotch 1 difference △f, performs PID control, and sets the DC system transmission power command value ΣP.
It outputs dρ.

Next, FIG. 2 shows the configuration of the distribution circuit. Distribution circuit] 8 is a multiplier 20, an operating pole number setting value 21, a comparator 22,
Six frequency deviations Δf made up of a bias setting value 23 and an arithmetic unit 24 are input to a comparator 22 and compared with a frequency high detection setting value Δfs. When the frequency deviation Δf is larger than Δfs, the comparator inputs '' to the output of the bias setting value 23 to the calculator 24 through the switch 25. ,
' is input to the multiplier 20 as the number of corrected operating poles. Multiplier 20
By inputting DC system transmission power command value ΣPdρ and ' as the corrected number of operating poles, outputs transmission power command values Pdp-A and Pdp-s for each operating pole.

It is now assumed that there is a two-pole DC power transmission system, system A and system B, and that DC power is being transmitted stably. At this time, the output of the M inversion film setter 21 is 2, and the comparator 22 is not operating, and the value 2 is input to the multiplier 20. In other words, the value of is the power transmission command for each type.

In this state, it is assumed that some abnormality occurs in the A-system DC power transmission system and the transmitted power of the A-system decreases. That is,
Transmission power Pdc-A of system A and transmission power Pdc-s of system B
The sum of

Pdc-A + Pdc-a <ΣPdp. As a result, the balance between the load and the transmitted power is disrupted, the mountain side bus frequency f increases, and the 1-frequency deviation Δf also increases. This situation is shown in FIG. When the frequency deviation Δf becomes larger than the frequency high detection setting value Δfs, the comparator 22 operates, and the output of the bias setter 23 is inputted to the calculator 24. The calculator 24 calculates -K"=2-1=1 to obtain the corrected number of operating poles.
(=1) is output to the multiplier 20. As a result, A series,
The transmission power commands Pdp-A and Pdp-B of system B are both Σ
Pdp, and the frequency increase is suppressed by increasing the transmitted power of the B system, which is the healthy pole side (load shift).

Thereafter, when the frequency deviation Δf decreases and becomes smaller than the frequency high detection setting value Δfs, the comparator 22 performs a return operation, and the output of the bias setter 23 is no longer sent to the calculator 24. the result.

Pdp-A and Pdp-a are each ΣP dp/2
Therefore, if the failure in system A has been recovered, stable power transmission will be possible.

In the above embodiment, an example was described in which the DC power transmission system was configured with two poles connected in parallel.

Of course, the present invention can also be applied to a DC power transmission system configured with two or more poles connected in parallel.

In that case, it goes without saying that the number of corrected operation poles is not limited to one, but is the same as the number of abnormal DC power transmission systems. To do this, for example, in FIG. 2, the comparison result from the comparator 22 may be transmitted to the bias setter 23, and when the deviation does not decrease, the output of the bias setting value 23 may be sequentially increased by '.

In addition, in the above embodiment, the frequency deviation Δf is input to the comparator 22 in FIG. 2, but the circuit configuration is such that the mountain side bus frequency f is input and the comparator operates when the frequency f exceeds a set value. However, the present invention can be implemented. Further, regarding the comparator operation, the operation value and the return value may be set to different values. Furthermore, instead of the comparator explained in the above embodiment, the mountain side bus frequency f or the frequency deviation △
The present invention can also be implemented by detecting the rate of change of f and providing the same function as the above embodiment.

In addition, in the above embodiment, it was explained that the operating pole number setting device sets the operating pole number in advance, but the operating pole number setting device automatically sets the operating pole number based on the operating information on the pole side or the signal such as the transmitted power of the DC transmission system. It may also be used to judge.

Further, in the above embodiment, the transmission power command value to each DC system is taken out from the common multiplier 20, but as shown in FIG. , 20B may issue a transmission power command to each DC system. In such a case, each transmission power command value can be changed according to the state of the grid at that time.

[Effects of the Invention] As described above, according to the present invention, when an abnormality occurs in the DC power transmission system, the number of operating poles is corrected based on the frequency deviation between the mountain side bus frequency and the 151 frequency. It becomes possible to stably control the frequency of the DC power transmission system, and as a result, it becomes possible to eliminate the influence on the power plant side when adopting a DC power transmission system.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a DC power transmission system according to an embodiment of the present invention, Fig. 2 is a detailed block diagram of the distribution circuit shown in Fig. 1, and Fig. 3 is an explanation of the operation when an abnormality occurs in the DC power transmission system shown in Fig. 1. Figure, 4th
The figure is a detailed block diagram of a distribution circuit according to another embodiment of the present invention. 1...Synchronous generator, 2...Generator circuit breaker, 3...
Mountain side bus bar, 4A, 4B, 12A, 12B... Converter circuit breaker, 5A, 5B, IIA, IIB... Converter transformer, 6A, 6B... Forward converter, 7A, 7B, 9
A, 9B...Smoothing reactor, 8^, 8B...DC transmission line, IOA, IOB...Inverse converter, 13...
- Claw side bus bar, 14... Frequency detector, 15... Reference frequency generator, 16.24... Arithmetic unit, 17... Controller, 18... Distribution circuit, 20... Multiplication Vessel, 21・
・・Operation pole number setting value, 22・・Comparator, 23・
...Bias setting value. ,・−゛・ ′〜−−ノ′ Figure 3: Troubleshooting I dispute 4th cause

Claims (1)

[Claims] In a device for controlling a power plant side AC bus frequency to a constant in a DC power transmission system that transmits power in parallel from a power plant side AC bus to a load side AC system via a plurality of DC transmission systems, means for setting the number of operating poles; Means for detecting the AC bus frequency on the power plant side and correcting the number of operating poles according to the detected value; and means for distributing the DC system transmission power command value by the corrected number of operating poles to each DC transmission system. 1. A frequency control device for a DC power transmission system, comprising: means for controlling a frequency of a DC power transmission system.