JPH0447150B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a variable speed water turbine generator, and in particular, an induction generator is used as the generator, and the generation output range of the induction generator near the synchronous speed is The present invention relates to a variable speed water turbine generator suitable for operation with a minimum frequency converter capacity.

[Conventional technology]

This type of variable speed water turbine power generation device that has been generally employed in the past is known, for example, as described in Japanese Patent Application Laid-open No. 72998/1983. That is, as shown schematically in FIG. 4, there is a winding type induction generator 1 equipped with primary and secondary windings, and this induction generator is rotated by a water wheel 2 directly connected to its rotor. While being driven, the secondary winding 1 of the induction generator 1
b is a cycloconverter (frequency converter) 3
AC excitation current adjusted to a predetermined phase according to the rotational speed of the induction generator is supplied, and AC power with a frequency equal to that of the power grid 4 is output from the primary winding 1a of the induction generator 1. Variable speed operation is performed. 5 is a function generator, into which the power generation output command P _p given from the outside and the water level detection signal H are input, and the maximum rotation speed command for operating at maximum efficiency is input.
Generate Nao and optimal guide valve opening command Yao. 7 is an induction machine for slip phase detection, the rotor of which is directly connected to the induction generator 1, the primary winding 7a is connected to the output side of the induction generator 1, and the secondary winding 7a is connected to the output side of the induction generator 1;
It is formed to output a slip phase signal S _P from b. This slip signal S _P and the optimum rotational speed command Nao are given to the cycloconverter 3, and as described above, the phase etc. of the AC excitation current supplied to the secondary winding 1b of the induction generator 1 are controlled. On the other hand, the optimum guide valve opening command Yao is given to the guide valve drive device 8, which controls the opening of the guide valve 9 so that the water turbine output _PT becomes an optimum value.

[Problem that the invention seeks to solve]

In such a power generation device, if we consider the case where the induction generator 1 is operated at around synchronous speed, the current capacity of the cycloconverter 3 is such that the current is inversely parallel because the interval between current polarity changes is long. The flow flows through only one side of the cycloconverter 3 consisting of a converter, and as a result, the cycloconverter 3
The output current capacity will be significantly reduced. The rotational speed range in which the cycloconverter capacity decreases is called the cycloconverter output prohibition zone, and naturally, the capacity of a cycloconverter designed without an output prohibition zone is the same as that of a cycloconverter designed with an output prohibition zone. It is significantly larger than the one that was created.

Therefore, in the past, the cycloconverter was designed with an output forbidden band, and the capacity of the cycloconverter was made small, sacrificing the power generation output range in that region, or conversely, the entire power generation output range was To enable operation, a large capacity cycloconverter with no output forbidden band was used.

Therefore, there has been a demand for this type of power generation device that can use a small capacity cycloconverter without an output forbidden band.

The present invention has been conceived in view of this, and its object is to provide a variable speed water turbine power generation device of this type that can be realized with a minimum cycloconverter capacity even without an output forbidden band.

[Means for solving problems]

That is, in the present invention, on the rotation speed command side of the function generator that inputs the power generation output command Po and outputs the rotation speed command and the guide valve opening command, the rotation speed command exists in the above-mentioned cycloconverter output prohibition zone. A rotational speed command change rate setter is provided that can change the rate of change of the rotational speed command only in the cycloconverter output prohibition zone.

[Effect]

That is, the present invention will be explained using FIG. 5, which shows the rotation speed command set when the power generation output command and the head are input.
Normally, in order to operate the water turbine at the highest efficiency point, the frequency generator sets the rotation speed command as Nao. However, at this speed, the cycloconverter output prohibition zone is passed slowly, causing the above-mentioned problem. Therefore, in the present invention, the cycloconverter output prohibition band near the synchronous speed (rotational speed Nmin~
The rotation speed command Na is set so that only the rate of change (rate of change upon input) of the rotation speed command that exists in the range of Nmax) can be increased and output.

〔Example〕

The present invention will be explained in detail below based on the illustrated embodiments.

FIG. 1 is a block diagram of a power generation device according to an embodiment of the present invention. Note that in FIG. 1, the same reference numerals as in FIG. 4 indicate the same or equivalent components, and a description thereof will be omitted. The function generator 5 receives the power generation output command Po as before.
and the water level detection signal H are input, and the optimum rotational speed command Nao and the optimum guide valve opening command Yao are generated on the output side. At this time, as shown in Figure 5, the rotation speed command Nao is set according to the power generation output command Po, but since the cycloconverter output prohibition zone is passed, the speed set by the rotation speed command change rate setting device is changed. let In other words, the rotational speed command Nao is reset as the rotational speed command Na so that only the rate of change of the rotational speed command (rate of change upon input) existing in the cycloconverter output prohibition zone becomes a sufficiently large rate of change, and the rotational speed command Na is output. Therefore, since the rate of change is increased only in the portion existing in the cycloconverter output forbidden band, the thermal influence on the cycloconverter element is slight, and the object of the present invention can be fully achieved.

The rotational speed command Na obtained in this way is the actual rotational speed command N detected by the rotational speed detector 6.
are compared by the comparator 10, and the deviation ΔN (=Na
-N) is input to the arithmetic unit 11. The calculator 11 includes a proportional element K ₁ , an integral element K ₂ /S, a differential element K ₃ S, and an adder 12, and outputs an optimum guide valve opening command so that the deviation ΔN becomes zero as long as the deviation ΔN exists.
Outputs a correction signal ΔC that corrects Yao. This correction signal ΔC is used as an optimum guide valve opening command in an adder 13.
Yao and the output from the adder 13, that is, the corrected guide valve opening command (Yao+ΔC) is input to the guide valve drive device 8. Guide valve drive device 8
consists of an adder 14 and an integral element K ₄ /S, the output of which is negatively fed back to the adder 14. Further, the power generation output command Po is also input to the comparator 15,
It is compared with the actual power generation output signal _PG detected by the power generation output detector 16, which is the other input, and the deviation ΔP (=Po− _PG ) is input to the power control device 17. The power control device 17 includes a proportional element K ₅ , an integral element K ₆ /S, and an adder 18 , the output of which is input to the cycloconverter 3 .

As mentioned above, ΔN → arithmetic unit 11 → adder 13,
The control group consisting of the guide valve drive device 8 → guide valve 9 → water turbine 2 → rotational speed command unit 6 → N → ΔN is a negative feedback loop, and is controlled steadily by the integrator K ₂ /S in the calculator 11. So that ΔN becomes zero, that is, N=
Controlled to become Na.

In this way, the actual rotational speed N always settles outside the prohibited zone, and even when the setting is changed across the prohibited zone, the prohibited zone can be passed in a short time, so the cycloconverter capacity can be reduced. Ability to economically design systems.

The power generation output command Po is composed of an integral element K ₆ /S included in the power control device 17, the power control device 17, the cycloconverter 3, the induction generator 1, the power generation output detector 16, and the comparator 15. Due to the negative feedback circuit, the deviation ΔP (=Po−P _G ) gradually decreases, and becomes P _G =Po in steady state. The opening Y responsiveness of the guide valve 9 to the guide valve opening command Ya is the power generation output to the power generation output command Po described above.
Slower than Po's responsiveness. By the way, during steady state, the deviation ΔY (=Yao-Y)=0, that is, Yao=Y, is achieved as follows. (a) The optimal guide valve opening command Yao output from the function generator 5 naturally corresponds to the power generation output command Po. (B)
As mentioned above, in steady state P _G =Po. (c) The inertia effect of all rotating parts such as the runner of the water turbine 2 and the rotor of the generator 1 is accelerated or decelerated by the difference between the water turbine output _PT and the power generation output _PG . It can be seen as a kind of integral element, and as described above, the arithmetic unit 11, the adder 13, the guide valve drive device 8, the guide valve 9, the water turbine 2, the generator 1, the rotation speed detector 6, and the comparator 10. Therefore, since a negative feedback circuit is configured, P _T =P _G in steady state.
(d) The guide valve opening degree Y corresponds to the water turbine output P _T. Combining the above (a) to (d), deviation ΔC = (Yao
-Y)=0, that is, Yao=Y.

FIG. 2 shows another embodiment of the invention and is a modification of FIG. 1.

Here, instead of inputting the output ΔC of the arithmetic unit 11 that performs optimization control of the rotational speed N in the form of correcting the guide valve operation signal, it is inputted in the form of correcting the power generation output signal Po. Other details are the same as in Figure 1.

Regarding the method of giving ΔC, considering that the rotational speed N varies depending on (hydraulic output P _T - actual power generation output P _G ), the optimization control of N can be performed using P _T as shown in Figure 1. You can see that it doesn't matter if you do it on the side or on the P _G side as shown in Figure 2.

In the case of Fig. 2, ΔC becomes zero and Po
The relationship =P′o=P _G is obtained.

Furthermore, in Fig. 2, it is possible to consider a modification such as removing the tracking of P _G with respect to Po from the excitation control system of the cycloconverter and moving it to the guide valve control system and inputting it in the form of correction of the optimum guide valve opening command Yao. The gist is also applicable to these modifications.

Also, in Fig. 2, the power generation output command Po adder 25
The present invention can also be applied to a simplified system in which P′o=ΔC is not given.

〔Effect of the invention〕

As explained above, according to the present invention, the cycloconverter capacity can be set under the condition that a cycloconverter output prohibition zone is set when the generator rotational speed is around the synchronous speed, and the power generation output range is within the cycloconverter output prohibition zone. Since this is the same as when there is no belt, the maximum power generation output range can be achieved with the minimum cycloconverter capacity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a variable speed water turbine power generation device according to one embodiment of the present invention, FIG. 2 is a block diagram of a variable speed water turbine power generation device according to another embodiment of the present invention, and FIG. 3 is a block diagram of a variable speed water turbine power generation device according to another embodiment of the present invention. A diagram showing an example of the relationship between output, rotation speed, and guide valve opening degree. FIG. 4 is a block diagram showing an example of a conventional variable speed water turbine generator. FIG. 5 is a diagram showing an example of the relationship between output, rotation speed, and guide valve opening. This is a graph showing how the settings are changed. 1... Wound induction generator, 2... Water turbine, 3...
...cycloconverter, 4...power system, 5...
Function generator, 6... Rotation speed detector, 7... Slip phase detection induction machine, 8... Guide valve drive device,
9... Guide valve, 10... Comparator, 11... Arithmetic unit, 13... Adder, 15... Comparator, 16...
Power generation output detector, 17... Power control device, 19...
...Rotation speed command change rate setter, 25...Adder.

Claims (1)

[Claims] 1. An induction generator comprising a primary winding and a secondary winding, the primary winding being connected to the power system and the secondary winding being excited with alternating current; a water turbine that drives the induction generator; A guide valve that adjusts the amount of water supplied to the water turbine, a guide valve drive device that controls and drives the opening degree of the guide valve, a rotation speed detector that detects the rotation speed of the induction generator, and at least the power generation output command. or a function generator that outputs a rotation speed command according to the actual power generation output, and a rotation speed control device that inputs the rotation speed signal of the rotation speed detector and the rotation speed command, and according to the output of the rotation speed control device. In a variable speed water turbine power generation device that adjusts the rotational speed of the induction generator by controlling the amount of AC excitation given to the secondary winding of the induction generator or the opening degree of the guide valve, the rotational speed set by the function generator. Enter the command and
When the rotational speed command is greater than the upper limit speed set to be larger than the synchronous speed of the generator, or when the rotational speed command is smaller than the lower limit speed set to be smaller than the synchronous speed of the generator, the function is generated. A rotation speed command that gives the output of the device as a rotation speed command to a rotation speed control device, and makes the rate of change of the output larger than the rate of change of the input when the rotation speed command exists between the upper limit speed and the lower limit speed. A variable speed water turbine power generation device characterized by being equipped with a change rate setting device.