CN1119525C - Method for starting machine group comprising pump turbine and motor generator - Google Patents

Abstract

The invention relates to a method for starting a machine group comprising a pump turbine and a motor generator. The inventive method has the following characteristics: the flow in the pressure pipe of the turbine is delayed in order to increase the pressure in said pressure pipe; the machine group is synchronised, i.e. the generator voltage and mains voltage phases are matched; and the machine group is subjected to a load in the form of the supply of electrical energy to the network or in another form (e.g., through the generator brake).

Description

Method of starting a unit comprising a turbopump and a motor-generator

technical field

The invention relates to a method of starting a unit comprising a turbopump and a motor-generator.

Background technique

The characteristic curve family of such a turbine is usually represented in a diagram in which the variation of the unit flow Q1' with the unit speed n1' is drawn. In the case of several turbopumps, the characteristic curve, ie the guide vane opening line, is curved in an S-shape. This S-shaped curvature is particularly strong in the no-load range of the characteristic curve and in the extreme part-load range, but also in the transition range from phase compensation to turbine operation. This leads to the impossibility of stable steady-state operation at large values of n1' in these regions, ie at small pressure heads. In extreme cases this can even lead to the fact that it is not possible to synchronize and load the unit consisting of turbine and motor-generator because the turbine goes into braking operation or even in reverse operation of the pump.

As a remedy, attempts have been made to avoid unstable characteristic curve regions. To achieve this, the shut-off mechanism can only be partially opened, which necessitates a greater guide vane opening when unloaded. The result is increased wear on the shut-off mechanism. Attempts have also been made to temporarily alter the machine characteristic curve itself by adjusting the guide vanes asymmetrically. A prerequisite for this solution is that the guide vanes can be adjusted asymmetrically. In machines with only one guide vane ring but no single servomotor control of the deflector wheels, this solution was only possible with great effort.

DE2935480A1 describes a method for operating a turbopump between part load operation and pump reverse operation. This involves bringing the characteristic curve of the turbo pump to a stable characteristic line during start-up. This solution consists in at least temporarily removing at least one guide vane from the synchronous structure and pre-opening it.

Contents of the invention

The object of the present invention is to provide a method with which a unit comprising a turbopump and a motor-generator can be started without difficulty, without the risk of the turbine turning into braking operation or of the pump running in reverse, and without increasing the Risk of wear and no special mechanical or electrical costs.

The object of the invention is achieved by a method of starting a unit comprising a turbopump and a motor-generator, wherein the flow in the pressure pipe of the turbine is decelerated in order to cause a pressure rise in the pressure pipe; the unit is then synchronized Transformation, that is, to make the phase of the generator voltage consistent with the grid voltage; then load the unit.

Preferably, the unit is loaded by feeding in electrical energy.

Preferably, the aggregate is loaded by means of generator braking.

Preferably, at least some of the guide vanes are partially or completely closed in order to increase the pressure.

Preferably, there are two sets, which are fed by the same pressure pipe; and, two or more sets are used to support the start-up of another set.

The invention provides a method for starting a unit comprising a turbopump and a motor-generator, wherein: a torque is applied by means of electric motor braking, thereby shifting the no-load curve; the unit is synchronized, that is to say the generator voltage and the grid voltage The phases are consistent; the unit is loaded by feeding electric energy into the grid.

The present invention provides a method for starting a unit comprising a turbopump and a motor-generator, wherein: the rotation speed change process and the phase of the generator voltage are pre-calculated by prior simulation; the machine is first accelerated to a rotation speed lower than the rated rotation speed; The moment of further acceleration is determined in such a way that the voltage systems of the power grid and the generator are to be in phase when the generator reaches the rated speed.

Preferably, the speed to which the machine is accelerated is as close as possible to the rated speed, so that the no-load point lies outside the critical characteristic curve region.

Preferably, with the help of prior simulation of the speed change process and the phase of the generator voltage, the start time is selected in such a way that the voltage system of the joint network and the generator are in phase when the set reaches the rated speed after acceleration, and thus can be compared with the immediately following The loading is synchronized, in this case the guide vane opening is adjusted continuously as a result of the prior simulation.

Description of drawings

The drawing shows the characteristic curves of the turbine.

Detailed ways

The inventor has the following knowledge:

Curve with constant guide vane opening The above-mentioned S-shaped feature is not very obvious or does not exist at all in the case of large net head. It must therefore be ensured that the turbine is placed in this characteristic curve range at least temporarily. In order to achieve this according to the invention, the net pressure head rises sharply instantaneously. This is achieved by the sudden deceleration of the water mass flowing in the pressure tube. The deceleration of the flow necessarily leads to a sudden pressure rise upstream of the machine and thus to an increase in the net head.

According to the invention, this state is then fully utilized immediately to synchronize the units in this state.

Next, load the unit by opening the deflector. The result is increased flow and energy feeding into the grid. The operating point must be shifted to such an extent that it leaves the critical characteristic curve region after the pressure shock subsides, ie after returning to the original pressure head.

The time intervals for synchronization and loading are not very long. It is usually 1 to 2 seconds. These processes must therefore be completed quickly. It is therefore more expedient to combine the synchronizer in the turbo regulator.

Furthermore, it is expedient if the above-mentioned pressure shocks are produced by adjusting the guide vanes. As a result, the angle of attack of the guide vanes is temporarily reduced and thus slows down the flow in the pressure tube.

If the plant consists of two or more units, it is also possible to temporarily change the net pressure head by changing the operating point of an adjacent unit connected to the same pressure pipe.

When synchronizing after a pressure shock, the following should be observed: The resulting pressure wave propagates from the guide vane at the speed of sound (ie at a speed of approximately 1200 m/s) in the pressure pipe. Pressure waves are reflected at discontinuities (changes in cross section, containers, etc.) and return with negative amplitude. This leads to a reduction of the net pressure head relative to the original value after the so-called reflection time has elapsed. This means that for the entire process (synchronization and loading) at most half the reflection time is available. So syncing and loading is rushed.

This fact should also be taken into account when selecting a synchronizer. Today's general synchronizers mostly work with very low phase change speeds between the motor generator and the voltage system of the grid. A relatively long time therefore elapses before the generator voltage is brought into phase with the grid voltage and before the circuit breaker can be closed. It is therefore necessary to use a high-performance synchronizer which, as already mentioned above, is integrated in the turbo regulator.

Important measures that can be taken individually or in combination are as follows:

*Calculate the pressure, speed and phase change process in advance;

*Simultaneous monitoring of all hydraulic and electrical parameters;

*The position of the guide vane is controlled in this way, that is, the increase of the net pressure head and the synchronization can be completed at the same time;

*Using the generator brake as a supporting component to obtain a counter torque and thus to move the operating point within the characteristic curve family;

*The shape of the pressure wave is influenced by the control program to change the position of the guide vane. In this case the control program is optimized so that the machine is pressurized for as long as possible.

There are three basic solutions according to the invention. A first solution is contained in claims 1 and 5 . One can call this the "pressure shock protocol (Drucksto β-Loesung)".

A second solution is defined in claim 6 . One can refer to this as a "generator braking concept (Generatorbremsen-Loesung)".

Independently of these, there is a third option. It is described in claims 7 to 9.

The invention will be further described below with reference to the accompanying drawings, specifically for the pressure shock scheme and the generator braking scheme. The drawing shows the characteristic curves of the turbine. The ordinate represents the unit flow rate Q1', and the abscissa represents the unit speed n1'.

Curves 1 to 6 are curves when the opening of the guide vanes is constant. The two lines 10, 20 are the lines for constant net pressure head. Between these two lines is the normal operating zone.

Curve 30 represents the no-load curve.

Curve 40 is a curve obtainable according to the invention.

Curve 50 is the no-load curve after the alternator has been moved by braking. It is outside the critical region for all guide vane openings. In this case allow normal sync and load.

Claims (9)

1. one kind is started a method that comprises the unit of turbine pump and motor generator set, and it has following feature:

1.1 make the mobile deceleration in the turbine pressure tube, so that the pressure in the build-up of pressure pipe rises;

1.2 make the unit synchronizing then, just make generator voltage consistent with the phase place of line voltage;

1.3 then load to unit.

2. it is characterized in that in accordance with the method for claim 1: load to unit by the feed-in electric energy.

3. according to each described method in the claim 1 to 2, it is characterized in that: described unit is loaded by means of generator brake.

4. according to each described method in the claim 1 to 2, it is characterized in that:, make the guide vane of part partly close or close fully at least in order to improve pressure.

5. according to each described method in the claim 1 to 2, it is characterized in that: be provided with two units, they are supplied with by same pressure tube; And, use two or more units to support the starting of another unit.

6. one kind is started a method that comprises the unit of turbine pump and motor generator set, and it has following feature:

6.1 apply a moment of torsion, thereby mobile no-load curve by motor brake;

6.2 make the unit synchronizing, that is to say that to make the phase place of generator voltage and line voltage consistent;

6.3 by electric energy feed-in electrical network is loaded to unit.

7. one kind is started a method that comprises the unit of turbine pump and motor generator set, and it has following feature:

7.1 calculate the phase place of rotation speed change process and generator voltage in advance by prior simulation;

7.2. machine is at first accelerated to a rotating speed that is lower than rated speed;

7.3 the moment that beginning is further quickened determines in such a way, promptly the electrical voltage system of interconnected power system and generator should be when generator reaches rated speed homophase.

8. in accordance with the method for claim 7, it is characterized in that: the as close as possible rated speed of that rotating speed that machine accelerates to is not in outside the critical characteristic curve district so that there is loading point.

9. in accordance with the method for claim 7, it is characterized in that: by means of simulating rotation speed change process and generator voltage phase place in advance, select starting in such a way constantly, promptly, the electrical voltage system homophase of interconnected power system and generator when unit quickens back arrival rated speed, and thereby can with the loading synchronous of and then carrying out, adjust the guide vane aperture in this case continuously as prior Simulation result.

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