RU1771032C - Method of antiemergency control of hydroelectric station - Google Patents

Abstract

Usage: in electrical engineering, in emergency control devices and hydrogenerators. Summary of the invention: in emergency mode, when unloading by active power is needed, the settings of automatic excitation controllers (ARV) are increased according to the voltage of the hydrogenerators for a time T 11 + Ta + Tz, where through Ti, determined by the time when the transmission angle reaches its maximum value, give a signal to close the guiding apparatus of the hydraulic turbines, which provides unloading by a predetermined value. After time T2, determined by the unloading time after the passage of the hydraulic shock, the ARV settings are reduced at a given speed for time T3, and after time T, the voltage on the busbars of the hydroelectric power station is set to be long-term acceptable. 1 ill. cl

Description

The invention relates to electrical engineering and, in particular, to emergency control methods for hydroelectric power plants and hydrogenerators.

In the event of an emergency change in the composition of power lines or in the event of an emergency unbalance of active power, the main emergency response to ensure the stability of the power system is the unloading of power plants. In the presence of hydropower plants in the power system, emergency unloading is carried out by shutting down part of the hydrogenerators. However, the frequent use of this technique leads to a decrease in the reliability of the operation of the main equipment of the hydroelectric station.

Unloading hydroelectric power stations by closing the guiding apparatuses of hydraulic turbines is not used as an emergency measure due to the impact of water hammer, which leads to a decrease in the level of stability in the initial phase of the process, and because of the low speed of the discharge of the power plant.

The purpose of the invention is to increase the efficiency of the emergency response manager of a hydroelectric power station.

The drawing shows dysgrs mma changes in operating parameters and ug-raoo

with

Yu

l impacts in emergency mode under the action of the proposed method:

d is the relative angle of electric transmission, departing from the tires of the hydroelectric power station;

U is the voltage on the tires of the hydroelectric power station,

Y is the controlling effect on increasing the settings of automatic excitation controllers (ARV) according to the voltage of hydroelectric generators;

P - active power transmission;

M - rotational hyoment on the shafts of hydroelectric generators;

TIME is a signal / floating by unloading a power plant in terms of active power, thereby closing the guiding apparatus1 of the hydraulic turbines;

PO is the output signal of the launch trigger revealing an emergency mode to ensure the stability of which the unloading of the hydroelectric power station is necessary.

The method is carried out as follows: After the occurrence of an emergency disturbance, the trigger, with a certain delay (at time ti), generates a control signal at its output, upon the occurrence of which the ARV settings of all (androgen generators) increase to a value corresponding to the maximum permissible level wiring on the tires of the power plant during the time T Ti + T2 h Tz. This operation achieves the maximum possible increase in the limit of static stability of power transmission, moreover, as According to the results of theoretical and experimental studies, the increase in the stability limit is almost proportional to the magnitude of the voltage increment on the tires of the power plant, unloading the power transmission by active power due to the increase in the local load of the power plant.

Ar au ay,

where Au is the voltage increment on the tires of the power plant;

and the regulating effect of the active power of the local voltage load.

The action of these factors ensures the full use of the potential capabilities of the excitation systems of hydrogenerators to maintain stability in the initial phase of the emergency process.

In order to maintain stability in the subsequent phases of the process, it is necessary to unload the power transmission by active power, since after a period of time T the voltage level on the tires of the power plant must be reduced; accordingly, the limit of the transmitted

power and the load of the power transmission will increase. However, despite the relatively low closing speeds of the hydraulic turbine guide vanes, a water hammer occurs at the beginning of the loading process, resulting in a temporary increase in the torque on the hydro generator shafts.

When unloading starts, simultaneously with an increase in the ARV settings for voltage, an increase in the torque on the hydraulic generator shafts caused by water hammer occurs when the relative angle of transmission increases, which leads to a decrease in the dynamic stability limit.

If the disengagement is performed with a delay TI, after the relative angle of the power transmission do not have its maximum value (time t2), then the moment is wound up during the braking of the generators in the second half-cycle of synchronous oscillations. In this case, the negative effect of water hammer on the conditions of dynamic stability is completely eliminated.

After the passage of the water hammer, the torque on the shafts of the hydraulic units begins to decrease (time instant t.z.), accordingly, the electric transmission is unloaded by the active power and the stability margin of the power system is increased.

After the power supply is unloaded to the value corresponding to the required safety margin in the emergency mode, defined for a long-term acceptable voltage level on the spikes

power plants, it becomes possible to begin to reduce the voltage on the tires of the power plant by lowering the ARV voltage settings. The specified sequence of operations provides the minimum

the time during which the maximum voltage level is maintained, while maintaining the reached margin of stability. The time interval from the start of unloading of power plants to the beginning

the voltage drop of the ARV is Ta.

In the case when the required unloading of the power transmission is ensured only by increasing the voltage on the tires of the power plant in the initial phase of the process, the reduction of the ARV settings should begin immediately after the passage of the hydraulic shock.

The speed of decreasing the ARV settings should be such that at the moment of the end of unloading, the specified values of the settings in the emergency mode corresponding to the long-term allowable voltage level on the power plant tires are reached. Changing the settings at the indicated speed will allow switching to the post-emergency voltage level without fluctuating the active power transmission power, since the decrease in power transmission load caused by the unloading of the power plant is compensated by the increase in load due to the decrease in power consumption by the local load while reducing the voltage. The outcome of these conditions is Y

Beat, speed, setpoint reduction ARV ()

defined by the expression

d Y 1 d PC

d t ai d t - discharge rate of the power plant

by active power.

In practical implementation, changes in the ARV settings for the voltage of all hydroelectric generators can be carried out using an emergency control system for the voltage level on the power plant tires, and unloading of hydroelectric power stations can be done using a group active power controller. In addition, the time intervals TI, T2, Tz and the total time T Th + T2 + Tz must be determined. This time determines the maximum permissible level to which the voltage on the tires of the hydroelectric power station can be increased in the initial phase of the process with an increase in the ARV settings. The lower T, the higher the permissible voltage level in the initial phase of the transient process, the higher the ARV settings can be increased and the higher the efficiency of emergency control.

The duration of Ti depends on the intensity of the disturbance and the mode of the power system. The maximum duration Ti can be preliminarily determined by calculation for the ultimate in dynamic stability of the emergency disturbance leading to the most severe post-emergency mode. Moreover, in most cases, the unloading is started not at the moment when the relative angle reaches its maximum value, but a little later, as a result of which the quality of damping of the accidental oscillations may decrease slightly, but the total effect of the emergency control will not change.

The time interval T2 from the moment of starting the unloading of the power plant to the unloading of the power transmission by a predetermined amount (or before the start of the reduction of the moment on the shafts

hydraulic units after the passage of hydroblow, for those cases when, to ensure the required safety margin in the emergency mode, unloading achieved by increasing the voltage is sufficient) is practically constant. Its duration can be determined either by calculation or experimentally.

The time interval Tk is determined

based on the accepted levels of voltage increase in the initial and final phases of the process, the magnitude of the regulating effect of the local load on the voltage and the discharge speed of the hydroelectric power station.

It follows from the foregoing that the proposed method makes maximum use of the potential capabilities of the excitation systems of hydrogenerators to provide dynamic stability in the initial phase of the emergency process; allows you to use the unloading of hydropower plants by closing the guiding devices as an emergency response, while providing the necessary margin

stability of the power system in the emergency mode at maximum unloading of the hydroelectric power station, the negative effect of water hammer and excessive power fluctuations caused by changes in the voltage on the tires of the hydroelectric power station are excluded.

Claims (1)

SUMMARY OF THE INVENTION A method for emergency control of a hydroelectric power plant, comprising detecting an emergency mode in which to ensure stability, it is necessary to unload the power plant in terms of active power, to increase the settings of automatic excitation controllers (ARV) with respect to the voltage of all hydrogenerators, and unloading the power plant by active power, characterized in that, in order to increase the efficiency of emergency control, the ARV settings for the voltage of the hydrogenerator are increased to value corresponding to the maximum allowable voltage level on the tires of the power plant for a given time T Ti + T2 + Tz, where Ti is the time interval determined by the time the relative angle of transmission reaches its maximum value; Ta is the time interval determined by the time of unloading the power transmission by a given value; Тз is the time interval determined by the reduction of the ARV settings for voltage at a given speed to values corresponding to the maximum permissible voltage level on the tires of the power plant for a long time, after a time interval Ti, the guiding apparatuses of hydraulic turbines are closed, which ensure that the power transmission is unloaded by a specified value; after a time interval Ti + T2, the ARV settings for the voltage of the hydrogenerators begin to decrease at a rate proportional to the ratio of the discharge speed of the power plant and the regulating effect of the local voltage load, through the time interval T - Ti + T2 + Tz, the voltage on the tires of the power plant is set equal to the maximum allowable level for a long time.