阅读说明：本技术 一种给定值减幅阶跃的起励控制方法 (Excitation control method for given value amplitude reduction step ) 是由 余翔 赵先元 周筱珊 马小高 焦涵 高向鹏 于 2021-08-23 设计创作，主要内容包括：本发明提供一种给定值减幅阶跃的起励控制方法,包括起励流程开始时将当前给定值设置为目标给定值的25％；当发电机机端电压积分值低于25％目标给定值时强制控制角为最小角度,当发电机机端电压积分值不小于25％目标给定值时转为闭环控制；闭环控制中当发电机机端电压的瞬时值达到当前给定值,或者给定值保持在当前值的时间达到0.1秒,修改当前给定值；给定值增加的幅值为目标给定值与当前给定值差值的10％,如果给定值增加的幅值小于1％额定电压,则给定值增加的幅值为1％额定电压；起励流程中给定值爬升到0.98倍目标给定值后,将给定值设置为目标值,起励流程结束。本发明起励建压时间短,超调小,几乎没有振荡。(The invention provides a given value amplitude-reduction step excitation control method, which comprises the steps of setting a current given value to 25% of a target given value when an excitation starting process is started; when the voltage integral value at the generator terminal is lower than 25% of the target given value, the forced control angle is the minimum angle, and when the voltage integral value at the generator terminal is not less than 25% of the target given value, closed-loop control is performed; in closed-loop control, when the instantaneous value of the generator terminal voltage reaches the current set value, or the time for keeping the set value at the current value reaches 0.1 second, modifying the current set value; the amplitude value of the given value is 10% of the difference value between the target given value and the current given value, and if the amplitude value of the given value is less than 1% of the rated voltage, the amplitude value of the given value is 1% of the rated voltage; and after the given value in the excitation initiating process climbs to 0.98 times of the target given value, setting the given value as the target value, and ending the excitation initiating process. The invention has short excitation voltage-building time, small overshoot and almost no oscillation.)

1. An excitation control method for given value amplitude step is characterized by comprising the following specific steps:

recording a target given value and current time when an excitation initiating process starts, and setting the current given value to be 25% of the target given value;

when the voltage integral value at the generator terminal is lower than 25% of the target given value, open-loop control is executed, the forced control angle is the minimum angle, and when the voltage integral value at the generator terminal is not less than 25% of the target given value, closed-loop control is converted;

in closed-loop control, when the instantaneous value of the generator terminal voltage reaches the current set value, or the time for keeping the set value at the current value reaches 0.1 second, modifying the current set value, and recording the current time as the starting time of the next set value step;

the amplitude value of the given value is 10% of the difference value between the target given value and the current given value, and if the amplitude value of the given value is less than 1% of the rated voltage, the amplitude value of the given value is 1% of the rated voltage;

and after the given value in the excitation initiating process climbs to 0.98 times of the target given value, setting the given value as the target value, and ending the excitation initiating process.

2. A method of excitation control for a given value damped step according to claim 1 wherein said control angle is calculated by PID.

3. A method as claimed in claim 1, wherein the step of increasing the target set value by 10% of the difference between the target set value and the current set value is calculated by using the following formula if the amplitude of the increase of the set value is less than 1% of the rated voltage

Ref＝Ref+max{0.01U_n,0.1·(Ref₀-Ref)}

Where Ref is the current set point, Un is the generator nominal stator voltage, Ref₀Is a target set point.

4. The method of claim 1, wherein the initiation process is initiated by setting an initiation process flag into the initiation process, and setting a pulse flag to allow the rectifier bridge to output.

Technical Field

The invention relates to the field of excitation control of a generator, in particular to an excitation control method for given value amplitude reduction step.

Background

The excitation initiating process of the generator is a process of establishing the voltage of the generator after the generator enters an idle state, and the national standard GBT7409.3-2007 requires that the excitation initiating process has the regulation time not more than 10 seconds, the oscillation frequency not more than 3 times and the voltage overshoot not more than 15% of the rated voltage.

The excitation process mostly raises the terminal voltage to the rated voltage, and a small part of the excitation process also raises the terminal voltage to the system voltage for quick grid connection. In the test state, the excitation mode may be an excitation current mode, and the excitation current is raised to a preset value. The set value for the voltage mode actuation in the test state may not be the rated voltage, but may be a value within a set range allowed by the set value in the idle load state.

Integration is a common function in automatic control systems to filter out transient disturbances. This is typically accomplished in the controller by the following equation

V_av＝V_av+(V-V_av)·k

Where V is an instantaneous value, Vav is what may be called an integral value, and k is a coefficient corresponding to an inertial time constant T, typically less than 1. Specifically to the voltage integral value calculation, k may be set to 0.03, invoked in a cyclic task with a period of 0.01 seconds.

In the case of an excitation system, the integrated value is used at a plurality of places. When the automatic mode taking the generator terminal voltage as a control object is switched to the manual mode taking the exciting current as a control object, the given value is set as the integral value of the current exciting current, and undisturbed switching can be realized.

Automatic control systems typically use an on-chip timer of the CPU incremented from 0 to a maximum value, with the cycle count being the common clock for each process. A 32-bit timer with a maximum count value of 2³²When the frequency of 84MHz is used for counting, the maximum counting time exceeds 51 seconds, and most timing requirements of high-speed control can be met.

The excitation processes of all manufacturers are different, even can be pure open-loop control, the control angle is gradually increased along with the rise of the voltage from the minimum control angle, the excitation process is ended when the voltage rises to be close to the rated value, and the voltage closed-loop control is switched to.

Disclosure of Invention

The invention aims to provide an excitation initiating control method for given value amplitude reduction step, which reduces the voltage overshoot of an excitation initiating process through a given value change curve which is steep at the front and flat at the back.

The technical scheme of the invention is as follows:

an excitation control method for given value amplitude reduction step comprises the following specific steps:

recording a target given value and current time when an excitation initiating process starts, and setting the current given value to be 25% of the target given value;

when the voltage integral value at the generator terminal is lower than 25% of the target given value, open-loop control is executed, the forced control angle is the minimum angle, and when the voltage integral value at the generator terminal is not less than 25% of the target given value, closed-loop control is converted;

in closed-loop control, when the instantaneous value of the generator terminal voltage reaches the current set value, or the time for keeping the set value at the current value reaches 0.1 second, modifying the current set value, and recording the current time as the starting time of the next set value step;

the amplitude value of the given value is 10% of the difference value between the target given value and the current given value, and if the amplitude value of the given value is less than 1% of the rated voltage, the amplitude value of the given value is 1% of the rated voltage;

and after the given value in the excitation initiating process climbs to 0.98 times of the target given value, setting the given value as the target value, and ending the excitation initiating process.

The control angle is calculated by PID.

The amplitude value of the given value is 10% of the difference value between the target given value and the current given value, and if the amplitude value of the given value is less than 1% of the rated voltage, the step of the amplitude value of the given value is 1% of the rated voltage is calculated by adopting the following formula

Ref＝Ref+max{0.01U_n,0.1·(Ref₀-Ref)}

Where Ref is the current set point, Un is the generator nominal stator voltage, Ref₀Is a target set point.

And setting an excitation starting process mark to enter the excitation starting process when the excitation starting process starts, and setting a pulse mark to allow the rectifier bridge to output.

Compared with the prior art, the invention has the beneficial effects that: the excitation voltage-building time is short, the overshoot is small, and almost no oscillation occurs.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention.

FIG. 2 is a schematic diagram of PID control according to the invention.

Fig. 3 is a diagram of an actual waveform of a given value step-off excitation of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-3, the present invention provides a technical solution:

as shown in fig. 1, when the excitation starting process starts, an excitation starting process flag is set to enter the excitation starting process, a pulse flag is set to allow the output of the rectifier bridge, a given value is set to be 25% of a target given value, and the current time is recorded as the starting time of the current given value. The target given value is a value which is expected to be reached by the generator terminal voltage at the end of the excitation starting process, for example, the excitation is started to the rated voltage, the target given value is the rated voltage, and the given value is set to be 25% of the rated voltage when the excitation starting process is started.

The open-loop control is performed before the voltage integral value at the generator terminal reaches 25% of the target given value, and the rectifier bridge control angle is set to be the minimum angle, so that the voltage rising speed can be accelerated.

And closed-loop control is performed after the voltage integral value at the generator terminal reaches 25% of the target set value, and the control angle is calculated by PID.

FIG. 2 shows a simplified PID control transfer function diagram for an excitation system, U being the instantaneous generator terminal voltage, Ref being the set point, T11<T12，(1+T₁₁s)/(1+T₁₂s) as an integration element, T13>T14，(1+T₁₃s)/(1+T₁₄s) is used as a differential link, K is a gain, and the output control quantity enters an inverse cosine link after amplitude limiting of (-1,1) to obtain a control angle of the rectifier bridge.

When the instantaneous value of the generator terminal voltage reaches the current set value or the duration of the current set value reaches 0.1 second, immediately recording the starting moment of the new set value at the current moment, and refreshing the set value according to the following company

Ref＝Ref+max{0.01U_n,0.1·(Ref₀-Ref)}

Where Ref is the current set point, Un is the generator nominal stator voltage, Ref₀Is a target set point.

And when the given value reaches 0.98 times of the target given value, setting the given value as the target given value, and ending the excitation starting process.

As can be seen in fig. 3, the excitation voltage buildup time is short, the overshoot is small, and there is almost no oscillation.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.