JPH01298933A - Variable speed generator for valve water wheel - Google Patents

Abstract

PURPOSE:To obtain a variable speed generator having a brushless structure by controlling the output current of a frequency converter, and vector-controlling the amplitude and phase of the field current of an AC exciter. CONSTITUTION:An AC excited generator 1 is coupled directly or through a short shaft to the rotor of an AC exciter 2, and the field winding of the generator 1 is connected in reverse phase sequence to the armature winding of the exciter 2 on the rotor. The runners of a valve water wheel are connected to the main shaft of the generator 1, and so composed as to be rotatable integrally as a whole. The stator side armature winding of the generator 1 is connected to a power system having a predetermined frequency, and 3-phase AC exciting current of low frequency corresponding to the slip frequency is applied from a frequency converter 3 to the stator side field winding of the exciter 2.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a variable speed generator intended for application in cylindrical valve water turbines in hydroelectric power plants.

(Prior art) Generators in hydroelectric power plants are usually operated via brushes in the case of static exciters, or via brushes in the case of brushless exciters.
A rotating field type synchronous machine is used, which is rectified by a rotating rectifier via an AC exciter, excited by DC, and rotates at a constant speed.

In the case of a cylindrical valve water turbine, the synchronous generator (10) is directly connected to the movable vane valve water turbine 0) via the main shaft (9) as shown in Fig. 4, and is installed in the water guide section of the water turbine. It is stored in (11).

(Problem to be solved by the invention) Conventionally, cylindrical valve water turbines were used for low head (approximately 5 to 30 m), and high rotational speeds could not be achieved due to specific speed limitations. Therefore, synchronous generators also had low rotational speeds. The number of poles increases, and the outer dimensions of the rotor become extremely large due to restrictions on the size of the rotor.

Since the above synchronous generator is installed inside a cylinder in the water turbine flow path,
As the external dimensions increase, both the cylindrical inner and outer diameters of the valve turbine must be increased, and in order to reduce the flow path loss of the turbine, the external dimensions of the generator are normally set.

It is necessary to keep the size to 1 to 1.2 times the runner diameter.
Beyond that, the efficiency of the water wheel decreases. In addition, since the outer diameter of the cylinder becomes larger, the number of excavations required for civil engineering increases, which increases the construction cost of the hydroelectric power plant, making it uneconomical.

The present invention is intended to solve the above-mentioned problems, and provides a variable speed generator with a so-called brushless structure, which is constructed by directly connecting an AC excitation type generator and an AC exciter instead of a synchronous generator. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the variable speed generator for a valve water turbine according to the present invention comprises an alternating current excitation type generator (1) directly connected to a cylindrical valve water turbine as shown in FIG. , a rotating armature-type AC exciter ■ that rotates integrally with this generator, and a frequency converter 0 that excites the stator side field winding of this AC exciter ■ at a variable frequency, for example. The configuration includes a cycloconverter. The AC-excited generator (1) is an AC-excited generator (1) similar to conventional ones, with a 3-set rotor winding on the primary stator and a 3-phase field winding on the secondary cylindrical rotor. The AC exciter ■ is a rotating armature-type AC-excited generator that has a 3-set mecha winding on the primary cylindrical rotor and a 3-phase field winding on the secondary stator. .

The rotors of the AC excitation type generator (1) and the AC exciter ■ are coupled directly or via a short shaft, and the AC excitation type generator ■
The field winding of the AC exciter (2) and the armature winding of the AC exciter (2) are connected to each other in reverse phase order on the rotor. In addition, a runner of a valve water wheel is connected to the main shaft of the alternating current excitation type generator (1), and the runners of the valve water wheel are configured so that they can rotate as a whole.

The stator-side armature winding of an AC-excited generator (υ) is connected to a power system with a constant frequency, and the stator-side field winding of the AC exciter ■ is connected to a low frequency converter ■ corresponding to the slip frequency. Frequency three-phase AC excitation is applied.

(Function) In the generator configured as described above, the armature current of the AC exciter ■, i.e., is controlled by vector control of the magnitude and phase of the output current of the frequency converter ■, that is, the field current of the AC exciter ■. The field current of the AC excitation type generator ω changes, and the torque and armature current of the AC excitation type generator ■ change. Therefore, the speed and active/reactive power of the AC-excited generator can be controlled by controlling the thyristor gate of the frequency converter.

Now, if the number of poles of the AC excitation type generator ■ and the AC exciter ■ are Pl and P, respectively, and P2<Pl, and the frequency of the power supply system is Fl (Hz), then the rotation speed n (rpm)
The relationship between and the excitation frequencies Fs1 (Hz) and fsz (Hl) of the AC excitation type generator (υ and AC exciter ■) is as shown in FIG.

In FIG. 2, fst is equal to the slip frequency of the AC-excited generator and is given by F1P1n/120.

This becomes the output frequency of the AC exciter ■, so the stator side excitation frequency of the AC exciter is fs2" l fsl-
f2' l = I Fl-(p1+Pz)n/120
It becomes 1. Here, f2' is the armature output frequency when the P2-pole AC exciter (2) is DC-excited and operated at a rotational speed n, which is given by f, 1=Pzn/120. Also, f
The intersection N1 between ax and the horizontal axis is 120F, /p, which is the synchronous speed of the variable speed generator 0) with respect to the power supply frequency F1, and the intersection N1 between fsz and the horizontal axis is 120F1/ (P + p,) This is equivalent to the synchronous speed of the generator, which is equivalent to the number of poles (P1 + P2) for the power system frequency F1, and the value of fsz when n = N is FSz = P
It is given by z Nt / 120.

As explained above, by adjusting the excitation frequency of the AC exciter in the range from O, that is, DC to FSz, an integrated AC excitation type generator f! i machine and AC exciter (2N2
It is possible to operate at speeds in the range Nu)≦n<Nu. However, the rotation direction of the field of the AC exciter is opposite in the case of n)N and the case of n<N.

(Embodiment) FIG. 3 is an embodiment of the present invention, which is a main circuit single-line connection diagram of a hydroelectric power plant using a brushless variable speed generator. The AC excitation type generator (1) is connected to the power system via the main transformer (c) and the parallel circuit breaker 0.

The power supply side of the frequency converter (2) is connected to the AC excitation type generator circuit via the excitation power transformer (2), and the load side is connected to the stator side field winding of the AC exciter (2). In this embodiment, the variable speed operation of the generator is performed by controlling the thyristor of the frequency converter (1) with a gate control signal from the control device 0, and controlling the rotational speed of the alternating current excitation type generator (ω).

This is done by supplying an excitation current with a frequency of one phase and magnitude corresponding to the active power and reactive power to the field winding of the AC exciter (2).

For example, power system frequency 507, water turbine rated rotation speed 18
The generator required for 8 rpm is a synchronous generator with 3 poles.
It is a two-pole generator, and the number of poles of the synchronous generator is equal to the sum of the number of poles of the AC excitation type generator and the number of poles of the AC exciter, and in the case of an AC excitation type generator, the number of poles per generator. In order to minimize this, it is necessary to make the number of poles of the AC-excited generator and the AC-excited TIa machine equal.

In other words, by increasing the number of poles of the AC excitation type generator to 16 balls and the number of poles of the AC exciter to 16 balls, the restrictions on the rotor required to attach the poles are relaxed, and the diameters of the rotor and stator are reduced. The diameter of the inner and outer cylinders of the valve turbine can be reduced significantly.

Bulb turbines are used when the head is low, and the efficiency characteristics of the turbine change even with slight fluctuations in head.

In this case, the frequency converter is controlled so that the water turbine is operated at the optimal rotation speed based on efficiency characteristics, and the variable speed generator outputs power at the frequency required for the power grid.
Even if there is head fluctuation, the water turbine can be operated at the optimum efficiency characteristics at any head.

〔Effect of the invention〕

As described above, the variable speed generator of the present invention reduces the number of poles and does not require an excessively large cylinder diameter unlike conventional valve turbine generators, thereby improving the efficiency of the water turbine and reducing the amount of excavation for civil engineering. This will improve the overall economic efficiency of construction costs.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of the brushless variable speed power generation system for valve water turbines according to the present invention, and Fig. 2 shows the relationship between the rotation speed and the excitation frequency of the variable speed generator and the AC variable speed exciter. 3 is a main circuit single-line connection diagram of a power plant using a brushless variable speed generator showing an embodiment of the present invention, and FIG. 4 is an assembled sectional view of a valve water turbine and generator showing an example of the conventional technology. It is. 1...AC excitation type generator, 2...AC exciter 3...
- Frequency converter, 4... Valve water turbine 5... Main transformer, 6... Parallel circuit breaker 7... Excitation power transformer, 8... Control device 9... Main shaft,
1o...Synchronous generator 11...Cylindrical agent Patent attorney Rule Chika Ken Yudo Daishimaru Ken Figure 1 Number of times u (rPm) Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] An AC excitation type generator directly connected to a cylindrical valve water turbine, a rotating armature type AC exciter that rotates integrally with the generator, and a variable frequency excitation to the fixed field winding of this AC exciter. A variable speed generator for a valve water turbine, characterized in that it is equipped with a frequency converter that performs