JPH0611168B2 - Power system stabilizer - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention is directed to a power system stabilizing device, and in particular to a single system generated due to the occurrence of a route accident in the power system, and the frequency fluctuation amount thereof within a predetermined range. The present invention relates to a power system stabilizer that controls power supply and load in order to maintain the power supply.

[Technical background of the invention]

Recently, the power system has become large in scale with the increase of the power demand, and the power source and the load are unevenly distributed due to the restriction of the location of the power source, and the degree of difficulty is increasing from the viewpoint of maintaining the system stability.

Moreover, due to measures such as short-circuit capacity measures, the system configuration is becoming radial due to the limitation of the number of continuous routes in each region of the system. Therefore, when a route accident occurs, the power system is separated into multiple power systems, and the frequency of configuring a so-called independent system is expected to increase in the future.

When a single grid is configured, a power grid stabilization device (Sy) that limits the power and load according to the power supply and demand conditions in order to maintain the frequency in the grid at the rated frequency.
stem Stabilizing Controller. SSC) operates. In this case, when the power supply limit amount or the load limit amount as the control amount is calculated, conventionally, it is based on the route power flow before the occurrence of the route accident.

That is, if the tidal current is sent to the external system, the load amount is reduced by that amount after the transfer to the independent system, and therefore the power supply is limited by an equal amount. On the contrary, if the tidal current is received from the external system, it is the same as the amount of power generation decreased, so an equal amount of load is limited. As described above, in the conventional SSC, it is common to limit the power supply or load by the same amount as the route power flow in advance.

[Problems of background technology]

In the above-mentioned conventional method, when the voltage of the system significantly decreases due to the occurrence of a large disturbance such as a route accident, the load of the induction motor of a general consumer may be disconnected. This phenomenon is called load drop from the system operation point of view, and in recent measurements, it has reached about 20% of the preload amount at the substation end.

This load drop amount is a considerable amount when viewed as the total amount of the entire independent system, and naturally has a great influence on the finish of frequency control by SSC. That is, a frequency settling error corresponding to the amount of load drop occurs. Moreover, the amount of load drop is not always constant, but fluctuates throughout the year, and also fluctuates depending on the facility operation status on the customer side, so it is difficult to grasp this quantitatively.

Therefore, when considering the frequency control of a single system by SSC, the effect of this load drop cannot be ignored, and some improvement measures were expected.

[Object of the Invention] The present invention has been made to solve the above problems, and an object of the present invention is to provide a power system stabilizing device that enables highly accurate frequency control.

[Outline of Invention]

In the present invention, the frequency control of the SSC is a two-stage control, and in the first-stage control, the power supply or the load is limited by an amount commensurate with the prior flow of the route. In the second stage control, the frequency fluctuation of the independent system is detected again, and the correction control is further performed based on the fluctuation amount.

Example of Invention

Embodiments will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an embodiment of a power system stabilizing device according to the present invention.

In FIG. 1, 1 is the main system, 2 is the independent system that is the target of stabilization control, and is always connected by the route transmission line 3, and is separated from the main system 1 due to an accident in the route transmission line 3. To be done. Reference numeral 4 denotes a power system stabilizing device (SSC), which constantly monitors the preliminary power flow of the route power transmission line 3 by the power flow detector 5 and detects the frequency fluctuation of the independent power grid 2 by the frequency detector 6. Reference numeral 7 is a generator connected to a single grid and subject to power limitation, 8 is a circuit breaker of the generator that is opened by a control signal of SSC4, and 9 is a load that is connected to a single grid and is subject to load limitation. Is a load circuit breaker which is opened by the control signal of SSC4. The first
In the figure, only one generator 7 and one load 9 are drawn,
There are multiple units depending on the scale of the independent system 2.

Here, the first-stage control is an equal amount control in which the power flow detector 5 detects the route power flow in advance and limits the power supply or the load by an amount commensurate with this, and the description thereof is omitted because it is a conventional system. The newly added second stage control will be described.

FIG. 2 is a frequency fluctuation curve diagram after the load is dropped, and the vertical axis represents the frequency change Δ / Δ with respect to the frequency peak value.
_max and the horizontal axis represent time t. Then, the time when the frequency reaches the peak value Δ _max is set to the origin (zero), and the state of frequency change according to the passage of time thereafter is shown.

In FIG. 2, (201) shows a maximum fluctuation straight line of the frequency change Δ, which is a straight line passing through the peak point corresponding to the maximum value Δ _max and parallel to the time axis t. (202) is the ideal variation curve of the frequency that converges to zero over time,
This means a frequency variation curve in an ideal case in which the first stage control is performed without excess or deficiency in consideration of load drop.
(203) shows an actual variation curve, which is between (201) and (202). However, all the values are standardized by the maximum value Δ _max , and the corresponding value on the actual fluctuation curve (203) after a certain time t _{s has} passed from the origin (zero) is set as Δ _s / Δ _max . The ideal fluctuation curve (202) can be grasped in advance by performing a dynamic characteristic simulation of the system or based on past measured data. And these values is important to keep the normalized (delta _max corresponds to 1.0) the maximum value delta _max of the frequency as a base, the ideal time of peak after t _s of the frequency in the second drawing The value of the variation curve is α (0α1). It is obvious that the value of the maximum fluctuation straight line at the simultaneous points corresponds to 1.0.

Therefore, the correction control amount by frequency is calculated as the second stage control. This is to perform the first-stage control (equal amount control) as usual, and to perform correction control based on the variation based on the frequency change in the independent system 2 separated from the main system.

That is, the relationship between the power variation ΔP in the independent system and the accompanying frequency variation (final set value) Δ (∞) is represented by ΔP = K _ss · Δ (∞) (1) And Here, K _ss is a system constant of a single system and is unique to the system, and is basic data of the system that can be calculated by actual measurement or the like. And the correction control amount Δ
P _'N is calculated by the following equation.

As is clear from FIG. 2, the meaning in () of the above equation indicates the degree of deviation from the ideal fluctuation curve (202) at the time point t _s after the time point (origin) at which the frequency fluctuation peaks. Is a coefficient that represents Corresponding to.

Therefore, if the frequency fluctuation in the independent system matches the ideal fluctuation curve (202), ▲ ▼ = 0, so (2)
From the equation, the correction control amount ΔP ′ _N = 0, and the second stage control is unnecessary. In this case, the first stage control (equal amount control) is performed without excess or deficiency, which means that the correction amount by the second stage control is unnecessary. If the frequency fluctuation matches the maximum fluctuation straight line (201), ▲ ▼ = 1-α, and therefore the correction control amount ΔP ′ _N = K _ss · Δ _max is obtained from the equation (2). In this case, the frequency in the independent system has reached the maximum value Δ _max despite performing the first-stage control, so that the correction control amount ΔP ′ for the second-stage control is set according to the system constant K _{ss. N} means maximum.

Here, consider the frequency settling value after a sufficient time has elapsed. This corresponds to the case of t _s → ∞ in FIG. 2, and α → 0 of the ideal fluctuation curve (202) and the value of the maximum fluctuation straight line (201) are 1.0, which is the same as the expression (2). The value of the correction control amount ΔP ′ _N of ΔP ′ _N = K _ss · Δ _s (3) where t → ∞. From the comparison between Eq. (3) and Eq. (1), it is clear that there will be no frequency settling error if the control corresponding to ΔP ' _N in Eq. . If Δ _s = 0 at t → ∞, the value in () of the equation (2) is zero, and thus the correction control amount ΔP ′ _N = 0. On the contrary, if Δ _S = Δ _max , the value in () is 1.0.
The correction control amount ΔP ′ _N = K _ss · Δ _max . From this, the coefficient in () of Eq. (2) does not depend on the passage of time,
It can be said to represent the degree of deviation of the frequency fluctuation from the ideal fluctuation curve (202). It is therefore clear that it takes a value of zero when there is no deviation and a value of 1.0 when it is maximum. Therefore, from the equation (2), the correction control amount ΔP ′ _N by the second stage control is calculated according to the degree of this deviation.

FIG. 3 is a flowchart for explaining the operation. When a route accident occurs in the route power transmission line 3 and the independent system 2 is configured, first, in step 31, the first-stage control is performed based on the same amount control as in the conventional method, and the load dropout is expected to be a constant value. . Next, at 32, the frequency detector 6 detects the frequency change of the isolated system 2 separated from the main system, and the value of the maximum frequency change Δ _max and the frequency change Δ _s at the time when a certain time t _{s has} elapsed from that time point. To detect.

Next, in step 33, using Δ _max and Δ _s
The correction control amount ΔP ′ _N is calculated from the equation (2), and the power source limit or the load limit, which is the second stage control by the amount corresponding to this, is executed and the process is ended.

〔The invention's effect〕

As described above, according to the present invention, the first control which is the equal amount control is performed.
The frequency variation of the independent system after the stage control is performed is detected, and the correction control amount corresponding to the frequency variation is calculated based on the maximum value and the frequency change value after a lapse of a certain time from the maximum value generation. Since it is configured to perform step control, it is possible to provide a power system stabilizing device that enables extremely highly accurate frequency control.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of a power system stabilizing device according to the present invention, FIG. 2 is a frequency fluctuation curve diagram after load drop, and FIG. 3 is a flowchart for explaining the operation. 1 ... main system, 2 ... independent system, 3 ... route transmission line, 4 ... power system stabilizing device, 5 ... tidal current detector, 6 ... frequency detector, 7 ... generator, 8, 10: Breaker, 9: Load.

Claims (1)

[Claims] 1. A power system stabilizing device that limits a power source and a load in order to maintain the amount of frequency fluctuation in a single system separated from this system within a predetermined value. Frequency control is performed in two stages. In the 1st stage control, the load drop amount of the entire single system is controlled by a predetermined value by the equal amount control that limits the power supply or the load in proportion to the route flow in advance, and in the 2nd stage control, after the separation. An electric power system stabilizing device characterized by detecting a frequency fluctuation of an independent system and performing a correction control by obtaining a correction control amount according to the following formula according to the fluctuation amount. However, Δf: frequency change Δf _max : peak value of frequency K _ss : system constant of independent system α: value of ideal variation curve, after a predetermined time from the peak of frequency (0 ≦ α ≦ 1). The value of the maximum fluctuation line at the simultaneous point is 1, and the value of the actual fluctuation curve is between 1 and α.