Control method for inhibiting invalid action of primary frequency modulation of thermal power unit

Abstract

The present application relates to a kind of control methods for inhibiting primary frequency modulation invalid action of thermal power unit, comprising: by taking big function to judge frequency exceeds dead zone, by delay open logic and delay close logic combination, realize the signal selection of power grid frequency fluctuation time, if frequency exceeds dead zone and fluctuation time <t, then primary frequency modulation valve position factor, primary frequency modulation power factor is output as 0;By taking small function to realize the selection of exceeding dead zone A deviation signal, by taking big function, delay open logic and delay close logic combination, realize the signal selection of power grid frequency fluctuation period >=t and exceeding dead zone, if frequency fluctuation time >=t, and exceeding dead zone <=A small frequency difference signal, then primary frequency modulation valve position factor, power factor is automatically maintained current value, t takes one of 0-2s, A takes one of 0-1r / min.It can automatically lock primary frequency modulation action when automatically identifying power grid frequency invalid disturbance, inhibit primary frequency modulation invalid action of thermal power unit.

Description

TECHNICAL FIELD

[0001] The present application relates to a primary frequency modulation control method for a thermal power unit, in particular to a control method for suppressing invalid action of primary frequency modulation of a thermal power unit. BACKGROUND

[0002] The existing primary frequency modulation function of a thermal power unit is completed by a digital electro-hydraulic control system (DEH) and a coordinated control function (CCS); that is, a speed signal is used to generate a primary frequency modulation valve position factor by a speed inequality rate design function on the DEH side, and the valve position factor is superimposed on a total valve position instruction of a steam turbine. A power instruction in a power loop of the CCS also generates a primary frequency modulation power factor according to the speed inequality rate function and superimposes the power factor to a target load. A principle diagram is shown in Figure 1 .

[0003] The existing primary frequency modulation control strategy of a thermal power unit is involved in frequency disturbances of a power grid without difference for fast frequency fluctuations (fluctuation period ≤ 1 second) and small frequency differences (exceeding a dead zone by 0.1 r / min). Frequent participation of the thermal power unit in the invalid primary frequency modulation of the power grid easily causes fatigue damage of a speed regulation system of the thermal power unit, and frequent participation causes fluctuations of a boiler pressure of the unit, insufficient heat storage, further causes the primary frequency modulation performance for improving stability of the power grid to be affected, and even causes power oscillation. SUMMARY

[0004] The present application aims to provide a control method for suppressing invalid action of primary frequency modulation of a thermal power unit, so as to automatically lock the primary frequency modulation action when automatically identifying invalid disturbances of a power grid frequency (i.e. fluctuation time ≤ t or small frequency difference frequency disturbance exceeding a dead zone by ≤ A), and suppress invalid action of primary frequency modulation of the thermal power unit.

[0005] The technical solution of the present application is as follows:

[0006] A control method for suppressing invalid action of primary frequency modulation of a thermal power unit comprises the following steps:

[0007] A frequency exceeding a dead zone is determined by a maximum function, and signal selection of a power grid frequency fluctuation time is realized by combination of a delay-on logic and a delay-off logic. If the frequency exceeds the dead zone and the fluctuation time is less than t, the primary frequency modulation valve position factor and the primary frequency modulation power factor are output as 0.

[0008] Selection of a signal exceeding a dead zone A deviation is realized by a minimum function, and signal selection of a power grid frequency fluctuation period ≥ t and exceeding the dead zone is realized by combination of a delay-on logic and a delay-off logic through a maximum function. If the frequency fluctuation time is ≥ t and the small frequency difference signal exceeding the dead zone is ≤ A, the primary frequency modulation valve position factor and the power factor are automatically maintained at the current value. If the small frequency difference signal returns to the dead zone interval time is less than t, the primary frequency modulation action signal is only acted once, and is automatically maintained during frequent overshoot of the dead zone.

[0009] Wherein, t takes one of 0-2s, A takes one of 0-1r / min.

[0010] Preferably, t is 1s, and A is 0.1r / min.

[0011] Preferably, by introducing the slip as the switching condition, the slip>0, the logic is automatically taken small between the holding value and the actual value; the slip<0, the logic is automatically taken large between the holding value and the actual value, realizing the self-adaptive tracking of 2r / min≤rotational speed deviation≤2.1r / min.

[0012] The beneficial effects of the present application are:

[0013] 1. The present application realizes the discrimination of invalid fluctuation signals of power grid, invalid disturbance of power grid frequency exceeding dead zone and fluctuation time<1s, primary frequency modulation inaction. Fluctuation time≥1s, and small frequency difference frequency continuous disturbance of exceeding dead zone≤0.1r / min, realizing the automatic optimal processing of the automatic taking small between the holding value and the actual value of the unit, inhibiting the frequent action of the primary frequency modulation of the unit, avoiding the damage of the speed regulation system, and improving the service life of the speed regulation system. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a primary frequency modulation control principle diagram of the prior art thermal power unit.

[0015] Figure 2 It is one of the logic diagrams of a control method for inhibiting invalid action of primary frequency modulation of thermal power unit.

[0016] Figure 3 It is the second of the logic diagrams of a control method for inhibiting invalid action of primary frequency modulation of thermal power unit.

[0017] Figure 4 It is the third of the logic diagrams of a control method for inhibiting invalid action of primary frequency modulation of thermal power unit. DETAILED DESCRIPTION

[0018] The present application will be described in the form of examples with reference to the accompanying drawings to assist the technicians in the technical field to understand and implement the present application. Except otherwise stated, the following examples and technical terms therein should not be understood beyond the background of the technical knowledge in the technical field.

[0019] Example 1: a control method for inhibiting invalid action of primary frequency modulation of thermal power unit, the logic relationship diagram is seen in Figure 4The control method comprises three parts, one is to suppress invalid disturbance of power grid frequency exceeding dead zone and fluctuation time < 1 second. The frequency exceeding the dead zone is judged by taking the maximum function (HISP = 2). The invalid fluctuation signal suppression of power grid frequency fluctuation time < 1 second is realized by combining the delay-on logic (TD ON) and the delay-off logic (TD OFF). If the frequency exceeds the dead zone, the fluctuation time over the dead zone is ≥ 1 second (the delay-on logic acts), and the frequency fluctuation returns to the dead zone and continues to act for 1 second (the delay-off logic acts), the primary frequency modulation action signal is sent out, the primary frequency modulation valve position factor and power factor signals are sent out, and the primary frequency modulation control function of the unit is completed. If the frequency exceeding the dead zone time < 1 second, the frequency disturbance is judged as invalid disturbance, and the primary frequency modulation valve position factor and the primary frequency modulation power factor are output as 0. The logic is shown in Figure 2

[0020] One is to suppress small frequency difference frequency continuous disturbance of power grid frequency fluctuation time ≥ 1 second and exceeding dead zone ≤ 0.1 r / min. The deviation signal exceeding the dead zone 0.1 r / min is selected by taking the minimum function (LOSP = 2.1), that is, the frequency deviation ≤ 2.1 r / min, the signal acts; the signal selection of power grid frequency fluctuation cycle ≥ 1 second and exceeding the dead zone is realized by combining the delay-on logic and the delay-off logic by taking the maximum function (HISP = 2). The logic of the above two logics is taken, the signal of the small frequency difference of the frequency fluctuation time ≥ 1 second and the exceeding dead zone ≤ 0.1 r / min is selected, the primary frequency modulation valve position factor and the power factor are automatically kept at the current value, and the primary frequency modulation of the unit is not frequently involved in action. If the frequency fluctuation duration time ≥ 1 second and the small frequency difference of the exceeding dead zone ≤ 0.1 r / min return to the dead zone interval time < 1 second, the continuous frequency fluctuation signal, the primary frequency modulation action signal only acts once, and is automatically kept during the primary frequency modulation frequent dead zone. The logic is shown in Figure 3 .

[0021] By introducing the slip as the switching condition, the logic automatically takes the minimum between the kept value and the actual value at high frequency (slip > 0); the logic automatically takes the maximum between the kept value and the actual value at low frequency (slip < 0). The speed deviation 2 r / min ≤ speed deviation ≤ 2.1 r / min is realized, the optimal value output is kept, and the adaptive tracking is kept. The logic is shown in Figure 4 .

[0022] (1) For the suppression of invalid disturbance of power grid frequency exceeding dead zone and fluctuation time < 1 second. The logic judges that this kind of signal is invalid action signal, directly outputs the primary frequency modulation power factor and the valve position factor of the unit as 0, and the unit does not participate in the primary frequency modulation action.

[0023] (2) The suppression of the continuous disturbance of the small frequency difference of the grid frequency fluctuation time greater than or equal to 1 second and exceeding the dead zone less than or equal to 0.1 r / min. The unit enters the automatic maintaining state through the logic, and the automatic optimal processing of the maintaining value and the actual value is realized through the high-low selection logic, the frequent action of the primary frequency modulation of the unit is suppressed, the damage of the speed regulation system is caused, and even the grid oscillation is caused.

[0024] The application can set part of parameters in the logic according to the field conditions, and the settable parameters include:

[0025] (1) The suppression of the grid frequency fast fluctuation signal, the settable range is 0-2 seconds, the recommended value is 1 second according to the regional grid operation and the two rule examinations;

[0026] (2) The suppression of the grid frequency fast and continuous fluctuation signal, the settable range is 0-1 r / min, the recommended value is 0.1 r / min according to the regional grid operation and the two rule examinations;

[0027] (3) The automatic optimal processing of the maintaining value and the actual value in response to the grid frequency fast and continuous fluctuation signal is realized through the high-low selection logic of the grid frequency fast and continuous fluctuation signal.

[0028] The application is described in detail above in combination with the drawings and the embodiments. It should be understood that all possible embodiments cannot be described exhaustively in practice, and the application concept is illustrated as much as possible by way of examples. The technical personnel in the technical field can select and combine the technical features in the above-described embodiments, change the specific parameters through tests, or replace the disclosed technical means of the application with the existing technology in the technical field to form specific embodiments without departing from the application concept of the application and without creative labor.

Claims

1. A control method for inhibiting invalid action of primary frequency modulation of a thermal power unit, characterized in that, The method comprises the following steps: The signal selection of power grid frequency fluctuation time is realized by taking the large function to judge the frequency exceeding the dead zone, and combining the delay-on logic and the delay-off logic, if the frequency exceeds the dead zone and the fluctuation time is less than t, the primary frequency modulation valve position factor and the primary frequency modulation power factor are output as 0; The selection of the signal exceeding the dead zone A deviation is realized by taking the small function, and the signal selection of the power grid frequency fluctuation period being greater than or equal to t and exceeding the dead zone is realized by taking the large function, combining the delay-on logic and the delay-off logic, if the small frequency difference signal of the frequency fluctuation time being greater than or equal to t and exceeding the dead zone being less than or equal to A, the primary frequency modulation valve position factor and the power factor are automatically maintained at the current value, if the interval time of the small frequency difference signal returning the dead zone is less than t, the primary frequency modulation action signal only acts once, and is automatically maintained during the primary frequency modulation frequently exceeding the dead zone; Wherein, t is one of 0-2s, and A is one of 0-1r / min; By introducing the slip as the switching condition, when the slip is greater than 0, the logic is automatically taken small between the maintained value and the actual value; when the slip is less than 0, the logic is automatically taken large between the maintained value and the actual value, the adaptive tracking of 2r / min to 2.1r / min of the speed deviation is realized.

2. The control method for inhibiting the invalid action of primary frequency modulation of a thermal power unit according to claim 1, characterized in that, t is 1s, and A is 0.1r / min.

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