JPS62255583A - Variable speed hydraulic turbine generator - Google Patents

Abstract

PURPOSE:To realize a maximum power generation output range with a cyclo converter of minimum capacity, by slidingly providing operation points avoiding a cyclo converter output prohibiting zone in the vicinity of a synchronous speed CONSTITUTION:When a hydraulic turbine characteristic function generator 5 produces an output which enters into the output prohibiting zone of a cycle converter 3, a history function generator 19 replaces the output with a rotational speed command which turns away the prohibiting zone. Then, a correction calculator 11 produces a correction signal so that an actual rotational speed coincides with the corrected rotational speed command. Further, a prohibiting zone kick back element 20 corrects a power generation output command when the actual rotational speed tries to enter into the prohibiting zone so that it kicks back the rotational speed to the outside of the prohibiting zone by primarily increasing or decreasing an output applied to a generator 1, i.e., a load imposed on a water turbine. With this arrangement, the capacity of the cyclo converter 3 can be set at the condition that the output prohibiting zone is provided and further a power generation output range is the same as the case wherein the output prohibiting zone is not provided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable speed water turbine power generation device, and in particular, an induction motor is used in the generator, and the power 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. 5, there is a winding type induction generator 1 with a -9 secondary winding, and this induction generator is rotationally driven by a water wheel 2 directly connected to its rotor. At the same time, the induction generator 1
An AC excitation current adjusted to a predetermined phase according to the rotational speed of the induction generator is supplied by a cycloconverter (frequency converter) 3 to the secondary winding 1b of the induction power generator Ia1.
Variable speed operation is performed so that AC power having the same frequency as that of the power system a4 is output from the primary winding fila. 5 is a water turbine characteristic function generator; 1 is a rotational speed signal N detected by a rotational speed detector 6; and a power generation output command Po given from the outside.
and the water level detection signal H are input, and the optimum rotational speed command Nao and the optimum guide valve opening command Y are input to operate at maximum efficiency.
generate ao. 7 is an induction machine for slip phase detection, the rotor of which is directly connected to the induction generator 1, the primary winding M, 7a is connected to the output side of the induction generator 1, and the slip phase is detected from the secondary winding 7b. It is formed to output a phase signal Sp. This slip signal Sp and the optimum rotational speed command Nao are given to the cycloconverter 3,
As mentioned above, the phase etc. of the AC excitation current supplied to the secondary winding lb of the induction generator 1 are controlled. On the other hand, the optimum guide valve opening degree command Yao is given to the guide valve drive device 8, and controls the opening degree of the guide valve 9 so that the water turbine output PT becomes the 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 the synchronous speed, the current polarity change interval of the cycloconverter 3 is long, so the current is higher than that of the anti-parallel converter. The current flows through only one side of the cycloconverter 3, and as a result, the output current capacity of the cycloconverter 3 is significantly reduced. like this.

The rotational speed range that causes a decrease in cycloconverter capacity is called the cycloconverter output prohibition band.

Naturally, the capacity of a cycloconverter designed with an output forbidden band is significantly larger than one designed with an output forbidden band.

Therefore, based on the conventional technology, the cycloconverter is designed with an output forbidden band, the capacity of the cycloconverter is made small, and the power generation output range in that region is sacrificed, or conversely, all the power generation There is no choice but to use a cycloconverter with a large capacity that can operate within the output range and has a large output prohibited heat zone.

Therefore, there is a need for this type of power generation device that can use a cycloconverter with a small capacity of output-inhibited heat.

The present invention has been conceived in view of this, and its purpose is to provide a variable speed single water power generator of this type which can be realized with a minimum cycloconverter capacity even in the output prohibited zone heat.

[Means for solving problems]

That is, the present invention focuses on the fact that when the same head and the same output are set as the water turbine operation conditions, the rotation speed can be set freely to a certain extent by allowing a slight decrease in efficiency. That is, to explain using Fig. 3, this Fig. 3 shows the output-rotation speed characteristic for a certain head H using the guide valve opening degree as a parameter. When the head H1 output Ps is given as the operating point, the optimum rotational speed is determined at the point, Nz of A. However, since the decrease in turbine efficiency for a deviation of one rotational speed is slight, the cycloconverter output prohibition zone near the synchronous speed (Rotational speed in the range of Nmtn to Nwaax),
For example, even if it is set by sliding it to the operating point A', no problem will occur.

[Effect]

For this reason, the present invention provides a power generation output detector for detecting the power generation output on the primary side of the induction generator, and also detects the deviation between the output signal of the power generation output detector and the power generation output command signal on the secondary side. a power control device that controls the excitation current of the secondary winding accordingly; a water turbine characteristic function generator that directly or indirectly inputs at least the power generation output command and outputs an optimal rotation speed command;
If the optimum rotational speed command falls within the above-mentioned prohibited zone, the Ii! i Appropriate rotation speed Rotation speed command correction element for replacing the rotation speed command with a rotation speed command at or slightly smaller than the lower limit of the rotation speed command band, or conversely replacing the optimum rotation speed command with a rotation speed command at or slightly larger than the upper limit of the prohibited band. and a correction calculator which inputs the correction rotational speed command and the deviation of the rotational speed detection value and outputs a correction signal that makes this deviation zero, and the rotational speed is detected by the rotational speed detector 6. When the actual rotational speed increases, i.e., when entering the prohibited zone from below, the power generation output command is increased near the lower limit of the prohibited zone, i.e., just before or after entering the prohibited zone, and the output applied to the generator, i.e., the load applied to the water turbine. It temporarily increases the rotational speed and kicks the rotational speed back out of the prohibited zone, and conversely, when the actual rotational speed decreases and attempts to enter the prohibited zone from above, it is near the upper limit of the prohibited zone, that is, the prohibited zone. Immediately before or immediately after entry, a prohibited zone kickback circuit is provided which acts to decrease the power generation output command, temporarily reduce the output applied to the generator, that is, the load applied to the water turbine, and kick the rotational speed back out of the prohibited zone. It is prepared.

〔Example〕

The present invention will be described 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. 5 indicate the same or equivalent components, and a description thereof will be omitted. The power generation output command Po and the water level detection signal H are inputted to the water turbine characteristic function generator 5 as in the conventional case, and the optimum rotational speed command Nao and the optimum guide valve opening command Ya are output on the output side.

occurs. At this time, if the power generation output command Po is an increase command and the optimal rotational speed command after increasing the power generation output is Nz and is within the cycloconverter output prohibition zone, the history installed at the rear of the water turbine characteristic function generator As shown in FIG. 4, the output of the function generator 19 is a rotational speed command Na (=N
-tll).

If the rotational speed command value Nao falls and enters the forbidden zone from above, the rotational speed command Na is held at N+aax until Nao falls to N□1 as shown in FIG.

This rotational speed command N& is compared with the actual rotational speed signal N detected by the first rotational speed detector 6 by a comparator 10, and the deviation ΔN (=Na−N) is inputted to a calculator 11. The arithmetic unit 11 includes a proportional element, an integral element Kx/S, a differential element KaS, and an adder 12.
A correction signal ΔC for correcting the optimum guide valve opening command Yao is output so as to make it zero' as long as there is a value. This correction signal ΔC is added to the optimum guide valve opening command Yao in an adder 13, and the output from the adder 13, that is, the corrected guide valve opening command (Yao+ΔC) is input to the guide valve driving device 8. The guide valve drive device 8 includes an adder 14 and an integral element K.
a/S, the output of which is negatively fed back to the adder 14. Further, the power generation output command P.

is combined with the output signal Pt of the forbidden zone kickback circuit 20 in the adder 21, becomes P'o, is also input to the comparator 15, and is the other input, the actual power generation detected by the power generation output detector 16. It is compared with the output signal Pa, and its deviation ΔP (
=Po'-Pc) is input to the power control device 17. The power control device 17 has a proportional element 5. It consists of an integral element 8/S and an adder 18, the output of which is input to the cycloconverter 3.

In the control device of this embodiment configured in this way, for example, at time t in FIG. Figure 2 (a)
When the output is raised in a stepwise manner as shown in FIG.
a is one power generation output command P' as shown in Fig. 2 (g)
It rises following the change in o. In order to simplify the explanation, the explanation of the 20 prohibited zone kickback element will be given later, and the following explanation will be made assuming that the output PJ is zero for the time being. That is, the integral element included in the power control device 17 is 6/S, the power control device 17, the cycloconverter 3, and the induction generator 1.
The deviation ΔP (=P'o-Pc) is generated by the negative feedback circuit composed of the one-shot power generation output command 16 and the comparator 15.
gradually decreases and becomes Pa:P'o at steady state.

On the other hand, the opening Y responsiveness of the guide valve 9 to the guide valve opening command Ya is slower than the responsiveness of the power generation output PC to the power generation output command Pa described above.
As shown in Fig. 2(f), the rotational speed N becomes smaller after the sudden change in the power generation output command Po.
It is temporarily decelerated, and then at time t1, as shown in Fig. 2(d), one power generation output Pa and the water turbine output PT become almost equal, so the decrease in one rotation speed N stops.However, at one time t1, the actual rotation The speed N is lower than the 1-rotation speed command Na, the deviation ΔN (= N a N ) is positive, and the calculation unit 1
Since the correction signal ΔC output from 1 is positive, the guide valve opening command (Yao+ΔC
) becomes larger than the optimum guide valve opening command Yao, and eventually the water turbine output PT becomes larger than the power generation output Pa. Therefore, the rotational speed N increases and approaches the 2nd rotational speed command N&, and the correction signal ΔC also approaches zero, and finally the guide valve opening Y matches the optimum guide valve opening command Yao, and the rotational speed N
becomes equal to the rotational speed command Na. That is, the integral element included in the arithmetic unit 11 is 2/S, the adder 12, the adder 13, the guide valve drive device 8, the guide valve 9, the water turbine 2, the induction generator 1, the rotation speed detector 6, and the comparator. Due to the negative feedback circuit constituted by 10, the deviation ΔN (=N&N) gradually decreases and becomes N=N a during steady state. Also,
At steady state, the deviation ΔY (=Yao Y)20, that is, Yao''Y, is achieved as follows: (a) Optimal guide valve opening command Ya output from the water turbine characteristic function generator 5
Of course, o corresponds to the power generation output command Pa. (b) As mentioned above, Pa=Po in steady state. (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 generated output PG, and is a kind of integral element. Moreover, as mentioned above, the arithmetic unit 11. Adder 13, guide valve drive device 8. Guide valve 9
, water turbine 21 heavy electric machinery 11 rotation speed detector 6 and comparator 1
0 constitutes a negative feedback circuit, so Pt=Pc in steady state. (d) Guide valve opening Y is water turbine output P
It corresponds to T. Combining the above (a) to (d), the deviation ΔY (= Yao Y) = O1, that is, Y
ao=Y.

On the other hand, if the optimum rotational speed command Nao falls within the cycloconverter output prohibition zone when lowering the power generation output command, the output of the history function generator 19 is a rotation equal to the cycloconverter output prohibition zone upper limit rotational speed. Speed command Na
(= N-ax).

As mentioned above, the actual rotational speed N of the water turbine eventually becomes equal to the rotational speed command Na corrected by the history function generator and is out of the forbidden zone, but transiently the actual rotational speed N of the water turbine becomes equal to the rotational speed command Na corrected by the history function generator, but temporarily It temporarily enters the forbidden zone.

One of the objects of the present invention is to minimize this temporary entry and to quickly escape.

Furthermore, as shown in Fig. 8, the power generation output command PO increases, and as a result, the optimum rotational speed command NaO crosses the forbidden zone from the bottom to the top, or the power generation output command PO decreases, resulting in the optimum rotation speed command NaO. The objective is to shorten the time required for the rotational speed N to pass through the prohibited zone when the rotational speed command Nao crosses the prohibited zone from the top to the bottom.

If the transit time can be shortened, the time during which one side of the inverse parallel converter of the cycloconverter is used can be shortened, thereby limiting the amount of heat dissipation and reducing the capacity of the cycloconverter.

FIG. 7 is an explanatory diagram of a forbidden zone kickback circuit which is a requirement of the present invention.

First, let us consider the case where the optimum rotational speed command Nao is set across the forbidden zone from the bottom to the top as shown in FIG. 8(a).

As Nao increases, the actual rotational speed N also increases, but N
When reaches the lower limit of the prohibited band in Figure 7, that is, Nm1°, it is prohibited i*
When the output P+ of the repeating circuit 20 begins to appear, as shown in the figure, when N goes deep into the prohibited band, the seed output P+ increases.

The maximum value Ptmax of P1 should be as large as possible when setting the speed command to cross the forbidden zone, but generally it is 20 to 3 of the rated output.
It is best to keep it to around 0%.

When PL increases, P'o increases, and as a result, the generator output Pa increases.

This means that as the load on the water turbine increases, the momentum of the increase in the rotational speed N is greatly weakened and the brakes are applied near the lower limit of the forbidden zone, N*tn.

Even so, the speed did not stop increasing and N became N□. When we reach +ε,
The output P+ of the forbidden zone kickback element that has been output so far is set to zero.

As a result, PG and Po decrease rapidly in a stepwise manner.

As a result, the composite output command so far P'o=Po+P+max
A positive deviation of P 1max suddenly occurs between the water turbine output Pt, which was almost balanced, and the rotational speed N begins to rise rapidly, crossing the prohibited zone at once and reaching a new optimal rotational speed (above the prohibited zone). Follow.

As described above, the increase in the rotational speed N is suppressed by the forbidden zone kickback element between Nmtn and Nmin+ε, and is accelerated as soon as it exceeds Nln+i.

Conversely, if the optimum rotational speed command Nao is set across the prohibited zone from top to bottom as shown in (b) of Fig. 8, then N max'=
Suppression is applied to the decrease in the rotational speed N between Naax-ε, and as soon as Nsaaε is exceeded, the engine accelerates and immediately runs through the prohibited zone and follows the new optimal rotational speed (below the prohibited zone).

Is it still prohibited? The iFu repeat element 20 is N→PI as shown in Figure 7.
It consists of a function generator and a circuit for determining whether the rotational speed N is increasing or decreasing (an incomplete differential circuit with a small time constant).

Figure 7 shows an example of a prohibited zone kickback circuit.As mentioned above, when the rotational speed N attempts to enter the prohibited zone, the P command is modified to measure pushback at the entrance, and if pushback cannot be achieved, the Any type of device that stops pushing back and encourages rapid passage through the prohibited zone will do.

FIG. 6 shows a side port of another speed command function generator which is an alternative to the history function generator 19 shown in FIG. 4 and which inputs the optimum rotational speed command Nao and outputs a rotational speed command N& that avoids the forbidden zone.

When the input N is between Nwa t n and N c, the output N is N mi . Then, while the input N is Nc-Nmax, the output N is set to Nmax.

〔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 provided when the generator rotational speed is around the synchronous speed, and in addition, the cycloconverter output is prohibited within one generation output range. Since this is the same as when there is no belt force grass, the maximum power generation output range can be achieved with the minimum cycloconverter capacity.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a rapidly variable speed water turbine power generation device according to an embodiment of the present invention, FIG. A diagram showing an example of the relationship between output, rotation speed, and guide valve opening degree, FIG. 4 is a diagram showing an example of the relationship between input and output of a history function generator, and FIG. 5 is an example of a conventional variable speed water turbine power generation device. Block diagram showing 6th
The diagram shows the side entrance of the speed command function generator used in place of the history function generator in Figure 4, Figure 7 is an explanatory diagram of the action of the prohibited zone kickback element, and Figure 8 is the optimum rotation across the prohibited zone. This is the side entrance where the speed command setting was changed. 1... Wound induction generator, 2... Water turbine, 3...
Cycloconverter, 4... Power system, 5... Water turbine characteristic function generator, 6... Rotation speed detector, 7... Induction machine for slip phase detection, 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... History function generator, 2o.
・Prohibited zone kick return element, 21...Adder, P″0・
... Revised power generation output command. Patent attorney Katsuo Ogawa's phase change 1 all N (II No. 5)

Claims (1)

[Claims] 1. An induction generator equipped with a primary winding and a secondary winding, with the primary winding connected to the power system, a water turbine that drives the induction generator, and 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, and a rotation speed detector that detects the rotation speed of the induction generator, and at least a rotation speed signal and a power generation output of the rotation speed detector. By inputting a command signal and controlling the amount of alternating current excitation current applied to the secondary winding of the induction generator and the opening degree of the guide valve, the induction generator rotates at an optimum rotational speed while connecting the primary winding to the power grid. In a variable speed water turbine power generator configured to generate alternating current power of the same frequency, a power generation output detector for detecting the power generation output is provided on the primary side of the induction generator, and a power generation output detector for detecting the power generation output is provided on the secondary side of the induction generator. A power control device that controls an excitation current of a secondary winding according to a deviation between an output signal of an output detector and the power generation output command signal, and a water turbine characteristic that inputs the power generation output command and outputs an optimum rotation speed command. a function generator;
A rotation speed command corrector inputs the optimum rotation speed command and corrects the actual speed setting command to a value such that the slip of the induction motor does not become too small, and a deviation between the corrected rotation speed command and the detected rotation speed value. A correction calculator inputs and outputs a correction signal that makes this deviation zero, and the rotation speed approaches the rated value and the slip of the induction motor is below a predetermined value (
A variable speed water turbine power generation device comprising a forbidden zone kick-back element that modifies the power generation output command so as to kick back the rotational speed and maintain the slip above a predetermined value when the rotation speed reaches the prohibited zone.