JP3480620B2 - Variable speed power plant, control method therefor, and control device therefor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in a variable speed power plant, a control method therefor, and a control device therefor, and more particularly, to a variable speed power plant in which variable speed excitation and synchronous operation are performed by switching excitation of a generator. The present invention relates to a control method and its control device.

[0002]

2. Description of the Related Art As a conventional control method for a variable speed generator, a control method as described in, for example, Japanese Patent Laid-Open No. 1-271669 is known. This control method will be described with reference to FIG. 2 showing a system of a variable speed generator. The variable speed generator 2 is directly connected to the water turbine 3 and the phase detector 4, and the rotational energy generated in the water turbine 3 is supplied to the system 1.
Output as power energy to.

The excitation of the variable speed generator 2 is carried out via the cycloconverter 6 with the alternating current fed through the exciting transformer 8. Excitation is performed by three-phase alternating current,
This three-phase current is output from the phase detector 4 that outputs the difference between the voltage phase of the system 1 detected by the voltage detector 9 and the rotor winding phase during the variable speed operation, and the output of the system 1 Q-axis component current command value I _{q *} generated by the q-axis component current command generator 10 from the deviation between the output detection value P of 1 and the active power setting value P ₀ set by the operator from the outside, and the voltage effective of the grid 1 A current command generator with the d-axis component current command value I _{d *} generated by the d-axis component current command generator 11 from the deviation between the detected value V of the value and the voltage effective value set value V ₀ externally set by the operator. The currents I _{u *} and I of each phase calculated in 12
_{Based on v *} and I _{w *} , the power converter 6 is used to drive the variable speed generator 2
It is made to flow in an appropriate size through the collector ring 7 to the rotor.

In the variable speed operation controlled in this way, even if the phase of the system suddenly changes due to a system accident or the like, the system can be operated without step out, and reacts instantaneously to fluctuations in the active power of the system. Can be a very effective one.

On the other hand, however, in the case of a large fluctuation of the active power in this state, for example, when the load suddenly changes due to the rise of the water level at the time of starting the pumping, the variable speed operation range may be exceeded, and the fluctuation of the active power of the system may occur. Variable speed operation is inconvenient when it is desired to operate independently.

Conventionally, in such a case, in general, such a problem is solved by operating the variable speed generator as a synchronous generator. When the variable speed generator 2 is operated by the synchronous operation method, the phase detector output is set to the constant frequency generator 5 in order to suppress the disturbance of the rotation speed of the rotor.
First, the q-axis component current command generator 10 is switched to the constant q-axis component generator 15.

That is, the switches 13 and 14 are switched for synchronous operation. In this way, if a force that tries to disturb the synchronization acts on the variable speed generator that is operating in synchronization for some reason, the rotation speed is kept constant by the synchronizing force that tries to maintain the synchronization against this. I try to drive while maintaining it.

[0008]

When the variable speed generator is synchronously operated as described above, it is possible to operate at a constant rotation speed, but the variable speed generator has a cylindrical rotor. As shown in FIG. 5, in a general salient pole rotor, the magnetomotive force f ₁ in the magnetic pole 31 is constant, whereas in the cylindrical rotor 32, the magnetomotive force f ₂ is It is generated by a coil 33 in the slot, which plays the same role as the poles of a salient pole rotor.

That is, it is possible to consider a temporary magnetic pole 31, and at this time, since the magnetomotive force f ₂ is generated by the coil 33 in the slot, the magnetomotive force becomes smaller as it goes away from the center of the magnetic pole of the virtual magnetic pole 31. However, since the short-circuit ratio of the variable speed generator is extremely smaller than that of a general synchronous machine, the possibility of step-out is increased and the stability is lowered.

The present invention has been made in view of the above circumstances, and it is an object of the present invention that even when the variable speed generator is operated synchronously, a step-out is sufficiently avoided and stable operation is possible. A variable speed generator plant of this type capable of improving the reliability of the variable speed generator and the entire power system, a control method therefor, and a control device therefor are provided.

[0011]

That is, the present invention provides a constant frequency generator for the output of the phase detector and a constant q-axis component generator for the q-axis component current command generator when the variable speed generator is synchronously operated. At the same time as the switching, the excitation of the rotor is strengthened to be excited to increase the step-out torque to achieve the intended purpose.

That is, specifically, a field current lower limit value settler is provided in the control device, and the lower limit value of the d-axis component current command value is increased to a size at which the variable speed generator is not out of step only during synchronous operation. The field current is increased or a voltage effective value set value setter is provided to increase the voltage effective value set value only during the synchronous operation to increase the field current.
Alternatively, a multiplier is provided, and the field current is increased by increasing the d-axis component current command value by the multiplier only during synchronous operation.

[0013]

In other words, with such a control method, the field current becomes large when the variable speed generators are synchronously operated.
That is, with the strong excitation, step-out of the variable speed generator can be sufficiently prevented, stable synchronous operation can be performed, and the reliability of the variable speed generator and the entire power system can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows the system of the variable speed generator. In the figure, 2 is a variable speed generator connected to the AC system 1, and a water turbine 3 is directly connected to this variable speed generator.

Further, the phase detector 4 detects a slip phase equal to the difference between the voltage phase of the AC system 1 and the rotation angle represented by the electrical angle of the variable speed generator 2.

The q-axis component current command generator 10 provided on the secondary side of the variable speed generator 2 has an output detection value P of the AC system 1 and an active power set value P ₀ set by an operator from the outside. The q-axis component current command value Iq * is generated from the deviation.

The switch 14 is designed to switch to the constant q-axis component generator 15 instead of the q-axis component current command generator 10. In addition, the d-axis component current command value Id * is generated by the d-axis component current command value Id * from the deviation between the detected value V of the voltage effective value of the AC system 1 and the voltage effective value setting value V ₀ set by the operator from the outside. Is output.

The field current lower limit value setter 18 sets the lower limit value of the d-axis component current command value Id *, and the current command generator 12
The current Iu *, Iv *, Iw * of each phase is calculated based on the signals Iq *, Id * and the output of the phase detector 4, and based on this, the power converter 6 causes the rotor of the variable speed generator 2 to rotate. Then, a field current having an appropriate magnitude is passed through the collector ring 7.

During the synchronous operation, the output of the phase detector 4 is switched to the constant frequency generator 5, and the q-axis component current command generator 10 is switched to the constant q-axis component generator 15. This switching is performed by the switches 13 and 14 that operate in conjunction with each other.

The field current lower limit value setter 18 raises the lower limit value of the d-axis component current command value Id * when a signal of the synchronous operation mode is received, and outputs Id * _' to the current command generator 12.

Step-out torque P of the variable speed generator during synchronous operation
_m can be represented by the following formula as described in, for example, "Handbook of Electrical Engineering" (written by The Institute of Electrical Engineers of Japan).

[0022]

[Equation 1]

From this equation, x _d is the reciprocal of the short-circuit ratio SCR, and therefore it is understood that the larger the short-circuit ratio SCR, the larger the step-out torque P _m and the more difficult it is for the generator to step-out.

Further, as described above, in the variable speed generator and the constant speed synchronous generator having the same output, the short circuit ratio of the variable speed generator is considerably smaller than that of the constant speed synchronous generator. It is understood that the possibility of step-out increases when the synchronous operation is performed.

In order to suppress this, the step-out torque P _m may be increased only when the variable speed generator is synchronously operated. As a method of increasing P _m , (1)
From the equation, control may be performed so as to increase the nominal induced electromotive force e _d . Incidentally, the nominal induced electromotive force e _d is induced by the electromotive force M _d of the field. The magnitude of the field electromotive force M _d and the field current I _find are equal.

Here, between the nominal induction motor power e _d and the field electromotive force M _d

[0027]

[Equation 2] | e _d | = | M _d | = | I _find | (2) Therefore, it is sufficient to increase the field current I _find . Specifically, _assuming that the step-out torque P _m1 of the constant speed synchronous generator having a certain output and the step-out torque P _m2 (P _m1 > P _m2 ) of the variable speed generator having the same output in the synchronous operation state are: In order to make the step-out torque of the variable-speed generator equal to the step-out torque of the constant-speed synchronous generator, the field current I _find of the variable-speed generator can be calculated from the relationship of the above-mentioned equation (2).

[0028]

[Number 3] I _find may be set to _{'= (P m1 / P m2} ) I find ...... (3) consisting of field current I _find'.

The field current lower limit value settler 18 is provided with the current command generator 1 so that the power converter 6 can flow the field current I _{find '.}
The signal of the d-axis component current command value Id * _' is sent to the current command generator 12 so that 2 acts.

As described above, according to this embodiment, when the variable speed generator is synchronously operated, the control for increasing the field current I _{find '} , that is, the strong excitation is performed, and the variable speed generator is operated in the synchronous operation mode. In this case, it is possible to prevent the out-of-step of the variable speed generator.

Next, another embodiment of the present invention will be described with reference to FIG. This figure is an example in which a voltage effective value set value converter 16 is provided in FIG. 2 of the conventional example.

When the signal of the synchronous operation mode is input, the voltage effective value set value converter 16 increases the voltage effective value set value V ₀ set by the operator from the outside during the variable speed operation to obtain a new voltage effective value. The set value V _{0 '} is output.

The new voltage effective value set value V _{0 ′} is such that the d-axis component current command generator 11 causes the power converter 6 to pass a field current having a magnitude such that the variable speed generator is not out of step. It is preset by an operator from the outside so as to output the axial component current command value Id *. By increasing the field current in this way, it is possible to prevent step-out of the variable speed generator.

Next, a third embodiment of the present invention will be described with reference to FIG. This figure shows a conventional example in which a switch 19, a multiplier 20 and a contact 21 are provided between the d-axis component current command generator 11 and the current command generator 12 of FIG.

The switching device 19 and the contact 21 are the other switching devices 1.
It is linked with 3 and 14 and is switched during synchronous operation. The multiplier 20 receives the d-axis component current command value Id * from the d-axis component current command generator 11 during variable speed operation, and holds the value in the multiplier.

When the synchronous operation is performed, the d-axis component current command value Id * held during the variable speed operation is increased to a size Id * _' at which the variable speed machine is not out of step, and the current command generator 12 is used.
Output to. Also in this embodiment, the field current is made large, which can prevent the step-out of the variable speed generator.

[0037]

As described above, according to the present invention, the excitation of the rotor of the variable speed generator is strengthened to be excited in the synchronous operation state. Therefore, the variable speed generator performs the synchronous operation method. In this case, it is possible to have a step-out torque similar to that of a constant-speed synchronous generator, and it is possible to avoid step-out when the variable-speed generator uses the synchronous operation method. It is possible to improve the sex.

[Brief description of drawings]

FIG. 1 is a system diagram of a variable speed generator for illustrating a control method of the variable speed generator, showing an embodiment of the present invention.

FIG. 2 is a system diagram of a conventional variable speed generator.

FIG. 3 is a system diagram of a variable speed generator for illustrating another embodiment of the present invention and for explaining a control method for the variable speed generator.

FIG. 4 is a system diagram of a variable speed generator for illustrating another embodiment of the present invention and for explaining a control method for the variable speed generator.

FIG. 5 is a diagram showing a relationship between magnetomotive forces of a cylindrical rotor and a salient pole rotor.

[Explanation of symbols]

1 ... AC system, 2 ... Variable speed generator, 3 ... Water turbine, 4 ... Phase detector, 5 ... Constant frequency generator, 6 ... Cyclo converter (power converter), 7 ... Collector ring, 8 ... Excitation transformer, 9 ... voltage detector, 10 ... q-axis component current command generator, 11 ... d-axis component current command generator, 12 ... current command generator, 13 ... switcher, 14 ... switcher, 15 ... constant q-axis component generator .

Front page continuation (72) Inventor Taisho Ohno 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Hiroto Nakagawa 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Inventor Toshifumi Kaneda 3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka Kansai Electric Power Co., Inc. (56) Reference JP-A 1-271669 (JP, A) JP-A-55 -83495 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 9/04 F03B 15/08

Claims (6)

(57) [Claims] 1. A variable speed power plant capable of variable speed operation in which the exciting circuit of the rotor of a variable speed generator is excited by an alternating current and the rotating frequency of the rotor is changed by changing the exciting frequency of the exciting circuit. In the control method of, when the variable speed generator is operated as a synchronous machine, the rotation
Force the excitation current of the child to be stronger than that during variable speed operation.
A method for controlling a variable speed generator, comprising: 2. A variable speed power plant capable of performing a variable speed operation in which the exciting circuit of the rotor of the variable speed generator is excited by an alternating current and the rotating frequency of the rotor is changed by changing the exciting frequency of the exciting circuit. In the control method, the excitation frequency of the excitation circuit is kept constant, and the variable speed power generation is performed.
When the machines are operated in synchronous operation, the excitation of the excitation circuit is
Variable speed power generation characterized by strong excitation
Plant control method. 3. A variable speed operation capable of changing the rotational speed of the rotor by exciting the exciting circuit of the rotor of a variable speed generator driven by a water turbine with an alternating current and changing the exciting frequency of the exciting circuit. In a control method of a variable speed power plant, the excitation frequency of the excitation circuit is made constant, and when the variable speed generator is operated in a synchronous operation state, the excitation circuit of the rotor
To make the excitation stronger than when driving at a variable speed.
Control method for variable speed power plant characterized by
Law. 4. The exciter circuit of the rotor of the variable speed generator is AC.
To change the excitation frequency of the excitation circuit.
Change the rotation speed of the rotor by
During operation, the voltage phase of the power system and the phase of the rotor
Phase detector that outputs the difference, and the output detection value of the power system
P and active power setting set by the operator from outside
Generates q-axis component current command value I _{q *} from the deviation from the constant value P ₀
And the q-axis component current command generator to control the excitation circuit.
In the control method of the variable speed power plant to be controlled, when operating the variable speed generator in the synchronous operation state,
A constant frequency that generates a constant frequency for the phase detector output
Constant output of q-axis component current command generator to output of generator
Of the constant q-axis component current command generator that generates the q-axis component of
At the same time each perating the Came ra switching to the force, the excitation of the rotor
It is designed so that it is operated with stronger excitation than during variable speed operation.
A method for controlling a variable speed power plant, comprising: 5. The exciter circuit of the rotor of the variable speed generator is AC.
To change the excitation frequency of the excitation circuit.
Allows variable speed operation by changing the rotation speed of the rotor
In the control method of the variable speed power plant, the excitation frequency of the excitation circuit is kept constant and the variable speed generation is performed.
D-axis component current only when the machine is operated in synchronous operation
Increase the command value to operate the rotor exciting current at variable speed.
I tried to drive as stronger excitation than time
A method of controlling a variable speed power generation plant characterized. 6. The exciter circuit of the rotor of the variable speed generator is AC.
To change the excitation frequency of the excitation circuit.
Enables variable speed operation by changing the rotation speed of the rotor
In the control method of the variable speed power plant, the excitation frequency of the excitation circuit is kept constant and the variable speed generation is performed.
Effective voltage setting only when operating the machine in synchronous operation
Increase the value to increase the exciting current of the exciting circuit.
Variable to drive as excitation
Control method for fast power plant.