JP3425221B2 - Power system stabilizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power system stabilizing device, and more particularly to a power system stabilizing device for improving the stability of a system immediately after stabilizing control at the time of system out-of-vibration.

[0002]

2. Description of the Related Art FIG. 5 shows a power system model to be controlled by a power system stabilizer. As shown in FIG.
A case is considered in which two power systems, that is, the system 1 and the system 2 are connected by interconnection lines, and power is exchanged between the systems to operate the system. In this case, an accident in one system makes it difficult to exchange power between the systems, which may lead to step-out between the systems.

If this is left unchecked, the effects of the accident will spread to the entire system. Therefore, by measuring and monitoring the phase difference between the two systems, the system out-of-step is detected, stabilization control such as power supply limitation and load limitation is performed, and the out-of-system out-of-system is maintained while the interconnection between the systems is maintained. To prevent from occurring.

FIG. 6 is a functional block diagram for explaining the configuration of the prior art. The instantaneous voltages at points representing the system 1 and the system 2 are respectively measured, and the measured values are used as the power system stabilizing device 1
And input to the inter-system phase difference calculation unit 10. The inter-system phase difference calculator 10 calculates the phase difference δ between the two systems using the instantaneous voltages of the systems 1 and 2.

The step-out determination unit 11 predicts the future δ from the change history of the phase difference δ, and performs the inter-system step-out determination promptly, and predicts the future δ from the history of the change of δ. It comprises a prediction section 111 and a comparison section 112 for comparing the δ prediction value obtained by the δ prediction section 111 with a threshold value δlimit. The control output unit 12 outputs a control output in response to the determination result of the step-out determination unit 11.

FIG. 7 shows a case where a step-out occurs between systems.
FIG. 9 shows a change in inter-system phase difference δ when stabilization control according to a conventional technique is performed. This figure shows the stabilization control effect of the prior art in the vibration step-out mode, in which step-out between systems is eliminated and stabilization is achieved.

[0007]

In the above prior art, the stabilization control is performed immediately after the step-out is detected (after the step-out prediction is detected). However, depending on the situation of the change of the phase difference δ between the systems, if the stabilization control is performed in consideration of the timing, the system fluctuation immediately after the execution of the stabilization control can be reduced. Therefore, in the related art, it is possible to prevent step-out between systems, but there is a possibility that a large system fluctuation such as a change in system frequency or a change in the phase angle inside the generator immediately after the control is performed. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power system stabilization device capable of reducing system fluctuation immediately after stabilization control and improving the dynamic stability of the system.

[0008]

According to a first aspect of the present invention, there is provided an electric power system stabilizing apparatus which obtains a voltage phase difference between systems using instantaneous voltages at respective representative points in a plurality of electric power systems. A phase difference calculation unit, a phase difference prediction unit that calculates a predicted value of a phase difference after a predetermined prediction time from a change history of the voltage phase difference obtained by the inter-system phase difference calculation unit, and the inter-system phase difference calculation unit. A step-out detection unit that detects step-out of the power system based on the obtained voltage phase difference or the predicted phase difference obtained by the phase difference prediction unit, and the predicted phase difference when the step-out detection unit detects step-out. A control timing determining unit that determines a control output timing according to the predicted time and the finishing time of the stabilization control based on the minimum value of the control timing and outputs a control execution signal; and a power execution system based on a control execution signal from the control timing determination unit. Prevent loss of synchrony And a control output unit for carrying out the stabilization control of the fit.

According to a second aspect of the present invention, in the power system stabilizing apparatus according to the first aspect, when the control timing determining unit detects the minimum value of the predicted phase difference, the control time determining unit traces back the finishing time from the predicted time. The control timing determination unit determines the control output timing of the control execution signal,
When detecting the minimum value of the predicted phase difference, the control timing determining unit determines that the control output timing of the control execution signal is determined by going back to the finishing time from the predicted time, and detects the minimum value of the predicted phase difference. At this time, the control output timing of the control execution signal is determined by going back the finishing time from the predicted time.

[0010]

According to a third aspect of the present invention, there is provided an electric power system stabilizing apparatus, comprising: an inter-system phase difference calculating unit for obtaining a voltage phase difference between the systems using instantaneous voltages at respective representative points of a plurality of electric power systems; A step-out detecting unit that detects step-out of a system, a control timing determining unit that outputs a control execution signal at a minimum value of the voltage phase difference when the step-out detecting unit detects step-out, and the control timing determining unit. And a control output unit for performing stabilization control for preventing out-of-step of the power system in advance by a control execution signal from the control system.

[0012]

The power system stabilizing device according to the first aspect of the present invention predicts a future δ from a change history of the phase difference δ between the systems in the step-out determination unit. The change of the amplitude of the predicted value is monitored, and the vibration step-out is detected when the amplitude is increasing and exceeds the threshold value. Here, when vibration out-of-step is detected,
The control timing is determined from the transition of the inter-system phase difference δ prediction value so that the system fluctuation immediately after the stabilization control is reduced. This control timing is a minimum value of the predicted inter-system phase difference.

Further, the power system stabilizing device according to claim 2 obtains the minimum value of the phase difference between the systems in advance, and determines the minimum value retroactively from this.

In the power system stabilizing device according to the third aspect of the present invention, when step-out is detected, the control timing determination unit outputs the control execution signal at the minimum value of the voltage phase difference.
Step-out can be prevented beforehand.

[0015]

FIG. 1 is a functional block diagram of an embodiment of a power system stabilizing apparatus according to claim 1 of the present invention. In FIG. I do. In this embodiment, a vibration step-out detection unit is provided in the step-out determination unit 11.
It is characterized in that a control timing decision unit 114 and a control timing decision unit 114 are added. Then, the vibration out-of-step detection unit 113 detects vibration out-of-step from the output from the δ prediction unit and the threshold limit, and the control timing determination unit 114 outputs the output from the vibration out-of-step detection unit 113 and the output from the δ prediction unit. And outputs a control execution signal such that the control timing is optimized. Where δ
Focusing on minimizing system fluctuations immediately after the control is performed when the control timing is set to the time when the control value becomes a minimum value, the present embodiment detects the time point at which the predicted δ value becomes the minimum value, and based on the optimal control timing output base value. And

FIG. 2 shows the phase difference δ between the systems and the detection of the step-out when the stabilization control according to the present invention is performed at the time of the system out-of-vibration synchronization.
It shows the temporal relationship between control output and control finish. In the figure, the actual system phase difference δ is indicated by a solid line,
The predicted value is indicated by a dotted line. A voltage oscillation having a period of about 4 seconds occurs due to the occurrence of the accident. Amplitude increase within a predetermined detection time,
If the amplitude is larger than the threshold value δlimit, a step-out is detected.

However, if the stabilization control is left as it is, the phase difference δ increases more and more as shown by a dashed line and goes out of step. However, as in the present invention, the minimum value of δ is determined at a predetermined control timing. By predicting and controlling when
As shown by the solid line, the system fluctuation after the stabilization control is performed can be reduced. In this case, the control timing is determined in consideration of (predicted time)-(predetermined operation time) in order to finish the control when the phase difference δ becomes a minimum value (near the minimum value). The control finishing time (predetermined operation time) is generally about 200 to 250 msec, and the timing of the control command output (control execution signal) is a predetermined time (for example, 20 msec) starting from the detection of the minimum value of the predicted δ value.
c) The output may be extended.

The operation will be described with reference to FIG.
The instantaneous voltage at the representative point is input to the inter-system phase difference calculation unit 10. The inter-system phase difference calculation unit 10 calculates the inter-system phase difference δ and passes it to the δ prediction unit 111. The δ prediction section 111 predicts δ in the future (for example, 220 to 270 msec) from the change history of δ and passes it to the vibration out-of-step detection section 113.

The process of the vibration step-out detecting unit will be described with reference to the flowchart of FIG. First, the δ prediction value obtained by the δ prediction unit 111 is read (step S31). The maximum value and the minimum value are detected while observing the change in the read δ prediction value (step S3).
2) Save the detected extreme value of the predicted δ value (step S3)
3). The amplitude value of the vibration is obtained from the stored extreme value (step S34). It is determined whether or not the amplitude value thus obtained tends to increase and exceeds the threshold value δlimit set in advance, leading to vibration step-out (step S35). As a result of step S35, if the out-of-step determination is established, an output with vibration out-of-step determination is output to the control timing determination unit 114 (step S36).

FIG. 4 is a flowchart showing the processing of the control timing determining section. The control timing determination unit 114 receives the output with vibration out-of-step determination from the vibration step-out detection unit 113 (step S41), and determines whether the predicted δ value is a minimum value (step S42). When the δ predicted value becomes the minimum value, the delay time required from the output of the control execution signal to the completion of the control (predetermined operation time: transmission delay time, processing time at the terminal device, CB opening time) is calculated. Considering in advance (finish time (predetermined operation time) is generally 200 to 250
msec), and outputs a control execution signal to the control output unit 12 so that the control is completed at the optimal control timing (step S43). For example, if the predicted time of δ is 250 msec before,
Assuming that the control finish time is 200 msec, 50 msec (250−20) from the time when the predicted δ value becomes the minimum value.
0) Later, a control execution signal is output.

The control output unit 12 includes a control timing determination unit 114
And outputs a control output in response to the control execution signal from. Thereby, the stabilization control can be performed at the timing when the actual phase difference δ between the systems is minimized.

As described above, according to this embodiment, the voltage phase difference is detected and the phase difference δ is predicted using the instantaneous voltage at the representative point between the systems, and the amplitude tends to increase and is larger than the predetermined value. Is determined, the control output is derived so that the control is completed near the time when the predicted value of the δ has reached a minimum value, so that the system fluctuation immediately after the stabilization control during inter-system vibration step-out is reduced. However, it is possible to improve the dynamic stability of the system.

In the above embodiment, the output timing of the control execution signal is controlled so that the control is finished to the minimum value of δ with the aim of minimizing the system fluctuation after the execution of the stabilization control. Even in this case, there is an effect that the system oscillation can be sufficiently reduced as compared with the related art. Also from this, the present invention can be implemented and effects can be obtained even if the step-out determination unit does not use the predicted δ value. That is, the output of the δ calculation unit 10 and the output of the out-of-step determination unit of another method are input to the control timing determination unit, and when the out-of-step determination unit of another method determines out-of-step, the minimum value of δ (or near) Then, the control execution signal may be output.

[0024]

As described above, according to the present invention, the timing of the control command output (control execution signal) is controlled so that the control can be finished at or near the minimum value of the phase difference between the systems at the time of step-out determination. Therefore, it is possible to reduce the system fluctuation after the stabilization control and improve the dynamic stability of the system.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of one embodiment of a power system stabilizing device according to claim 1 of the present invention.

FIG. 2 is a diagram illustrating stabilization control according to the present invention.

FIG. 3 is a flowchart showing processing contents of a vibration step-out detecting unit in the embodiment of the present invention.

FIG. 4 is a flowchart showing processing contents of a control timing determination unit in the embodiment of the present invention.

FIG. 5 is a power system model to be controlled by the power system stabilization device.

FIG. 6 is a functional block diagram for explaining the configuration of the related art.

FIG. 7 is a diagram showing the effect of the stabilization control according to the related art.

[Explanation of symbols]

1 Power system stabilizer 10 Inter-system phase difference calculator 11 Step-out judgment unit 111 δ prediction unit 113 Vibration step-out detector 114 Control timing decision unit 12 Control output section 112 Comparison section

Claims (3)

(57) [Claims] An inter-system phase difference calculating unit for obtaining a voltage phase difference between systems using instantaneous voltages at respective representative points in a plurality of power systems, and a voltage phase difference obtained by the inter-system phase difference calculating unit. A phase difference prediction unit for obtaining a predicted value of a phase difference after a predetermined prediction time from a change history of the system, and a voltage phase difference obtained by the inter-system phase difference calculation unit or a prediction phase difference obtained by the phase difference prediction unit. A step-out detection unit that detects step-out of the power system; and a pole of the predicted phase difference when the step-out detection unit detects step-out.
A control timing determining unit that determines a control output timing according to the predicted time and the finishing time of the stabilization control based on the small value and outputs a control execution signal; and disconnection of the power system by the control execution signal from the control timing determining unit. A power system stabilizing device, comprising: a control output unit for performing stabilization control for preventing keying. 2. The control timing determining section, when detecting a minimum value of the predicted phase difference, determines a control output timing of the control execution signal by going back the finishing time from the predicted time. 2. The electric power system stabilizing device according to 1. 3. An instant of each representative point of a plurality of power systems.
Finding the phase difference between systems using voltage
A calculation unit, and the step-out detection unit for detecting a step-out of the power system, the
When the step-out detection unit detects step-out, the voltage phase difference is minimized.
A control timing determining unit that outputs a control execution signal with a value,
In response to a control execution signal from the control timing determination unit,
Implement stabilization control to prevent power system step-out
A power system stabilizing device, comprising: