JPH0612929B2 - Transmission control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses an automatic sequence control device applying a microcomputer or a digital relay as hardware to minimize power loss in a transmission line. The present invention relates to a power transmission control method for rationally performing an automatic tap switching operation of a transformer at a power transmission end and a power reception end from a software aspect.

[Conventional technology]

Conventionally, various automatic P-Q control devices or methods for controlling the active component P and the reactive component Q of electric power flowing on a power transmission line so as to minimize power transmission loss are known. These methods take various forms, but the basic idea is almost the same. First, the voltages and currents at both end nodes of the power transmission line, that is, at the power transmission end and the power reception end are measured by the F parameter. Correlate each other by simulating with a terminal circuit. Based on this, the transmission loss is derived as a function of the voltage of the transmission line and the flow rate of active and reactive power flowing therein, and from the relational expression, the reactive power Q at the receiving end node is approximately used as a condition for minimizing the transmission loss. It is obtained as a function of active power P as in the following equation.

Qa + bp + cp ² where a, b and c are constants determined by the F parameter described above.

Therefore, in the conventional method, the reactive power Q that minimizes the transmission loss is obtained as the target value from the above equation from the active power P as the power flow required at the time of controlling the transmission line, and the actual measured value of the reactive power is obtained. It is usual to perform tap switching operation of the transformer so that the target value becomes. Further, in such an automatic PQ control device including the setting of the above target value, its hardware is often composed of an analog circuit.

[Problems to be solved by the invention]

As is well known, the tap switching of the transformer cannot be made very fine, and the minimum voltage adjustment amount for one tap switching operation is about 1% of the total voltage. However, in the above-mentioned conventional method, the degree of the change in the reactive power due to this one-time switching operation is not always clear as to the degree of the effect of reducing the transmission loss. If this happens, the operation of the system will be hatched. Therefore, in order to avoid this extra operation, a dead zone is provided on the control operation to stabilize the control. However, in practice, it is not easy to set the width of this dead zone, and when this width is set to a slightly larger value, fine control becomes impossible, resulting in a decrease in control performance. Is more likely to occur.

Also, as described above, when the control device is assembled by an analog circuit, the constants a, b, and c in the above formula must be set and placed in the circuit, but it is difficult to set them, and it is unexpectedly troublesome. It takes time to settle the operation, and it is easy to get out of order during long-term operation. In addition, since the power transmission loss is composed of two lines and can be switched between one-line operation and two-line operation in many cases, double analog circuits should be provided for setting the above parameters a, b, and c. I have to.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and to stabilize control without providing a dead zone in operation and to easily set or set circuit parameters of a transmission line.

[Means for solving problems]

According to the present invention, as described above, when controlling power transmission so as to minimize power transmission loss via a voltage regulator provided at one of both end nodes of a power transmission line whose circuit parameters are known, A power detection means for detecting the flow rate of power consisting of both effective and ineffective components at a specific node, and the power detected by the means, the circuit parameter of the transmission line, and the adjusted voltage on the node side for adjusting the voltage. A transmission loss calculation means for calculating the power loss in the transmission line based on the transmission line, and an increase / decrease index indicating the amount and direction of increase / decrease in the transmission loss per unit increment of the adjusted voltage based on the circuit parameter of the transmission line and the adjusted voltage. Using the index calculation means for calculating, the transmission loss calculation means is provided with a current value as an adjusted voltage and a planned value obtained by changing the current value by a predetermined voltage adjustment amount by the voltage adjustment device, and corresponding to them. The current transmission loss and the predicted transmission loss after voltage adjustment are calculated respectively, and when the predicted transmission loss is lower than the current transmission loss and the increase / decrease index value exceeds a predetermined limit value, the positive / negative sign indicated by the increase / decrease index is given. Accordingly, the voltage is adjusted by increasing or decreasing the voltage to be adjusted by the voltage adjusting device.

In the above configuration, the power transmission loss calculation means and the index calculation means are executed by software in a microcomputer incorporated in the automatic control device, and the circuit parameters of the transmission line are also stored in, for example, the ROM of the storage unit in the microcomputer. Stored in. Although it is necessary to use a conventional analog circuit for the power detection means to some extent, it is possible to provide a basic detection amount by a microcomputer after changing the analog digital. The specific node whose power is detected by this power detection means is usually the same as the node where the voltage regulator that performs tap switching of the transformer is placed, but in some cases, the node on the opposite side of the transmission line. But it doesn't matter. Further, the voltage adjusting device is usually placed at the power receiving end node, but may be at the power transmitting end node.

[Action]

In order to facilitate the understanding of the operation of the above-described configuration, the relationship between the electrical quantities treated by the present invention, which is slightly longer, will be described first by using equations. It should be noted that in the following, the quantities expressed in capital letters of the alphabet represent vector quantities or complex quantities, and the quantities expressed in lower case letters represent scalar quantities or practicum numbers.

As shown in FIG. 1, the transmission line 1 can be simulated by, for example, a Π-type equivalent circuit, and the currents 11 and 12 at the nodes N1 and N2 at both ends thereof are calculated by using the admittance matrix and the voltages V1 and V2 and the following equations. Can be related.

Of course, the admittance Y11 and the like are uniquely determined complex quantities converted from the admittances Y1 and Y2 and the impedance Z12 in the previous equivalent circuit. The current in the above equation
As shown in FIG. 1, I1 and I2 are both represented by a positive direction in which they flow into the transmission line 1.

From the equation (1), the tidal flow of electric power W1 and W2 flowing from the nodes N1 and N2 into the transmission line 1 Therefore, the power loss WL in the transmission line 1 is Becomes However, v1 = | V1 | and v2 = | V2 |.

The effective component in the power loss WL of the above equation (3) is represented by the transmission loss pL, and if the voltage V1 of the node 1 is taken as the reference voltage to be 1 in the unit method in order to simplify the equation, then Y12 = Considering that it is Y21, pL ＝ g11 + g12 ・ e2 + g22 ・ v2 ² ……………… (4) shows the transmission loss pL. However, Y11 ＝ g11 + j ・ b11 Y12 ＝ g12 + j ・ b12 Y22 ＝ g22 + j ・ b22 V2 ＝ e2 + j ・ f2 shall be replaced.

Power flow W2 at node N2 according to the second equation in (2) above
Is expressed as W2 = p2 + j · q2, and if this is rearranged in the same manner as above, the active power p2 and reactive power q2 at the receiving end node N2 are expressed by the following equations.

p2 ＝ g21 ・ e2 + b21 ・ f2 + g22 ・ v2 ² q2 ＝ －b21 ・ e2 + g21 ・ f2−b22 ・ v2 ² …… (5) Note that in relation to the above equation, v2 ² = e ² + f ² is there.

Now, returning to FIG. 1, it is assumed that the voltage adjusting device 10 which is a transformer with tap switching at the time of load is on the side of the power receiving end node N2 as shown in the figure, and the voltage V2 and the current I2 at this node are the voltage transformer. 4 and the current transformer 5, respectively. Of these, the absolute value v2 of the voltage V2 is the adjusted voltage adjusted by the voltage adjusting device, and the amount of voltage adjustment by one tap switching is Δ _v . The voltage regulator 100 shown by the alternate long and short dash line in the figure functionally shows various elements related to the implementation of the present invention and its operation. In the power controller, a power detector 20 and a transmission loss calculator are provided. The transmission line circuit parameter Y including the admittance Y11 and the like is stored.

The power detection means 20 receives the detected values of the voltage V2 and the current I2 from the voltage transformer 4 and the current transformer 5, and then receives the node N2.
The effective component p2 and the ineffective component q2 of the electric power flow rate at are detected and given to the transmission loss calculation means 30 and the index calculation means 40. The transmission loss calculation means 30 calculates the transmission loss pL based on the active and reactive powers p2, q2 and the circuit parameters.
Since it is necessary to know the real component e2 of the voltage V2 in order to calculate this transmission loss pL using the previous equation (4), first use equation (5) with the given active and reactive powers p2 and q2 as known quantities. Solve as a simultaneous equation with both components e2 and f2 of voltage V2 as unknowns. At this time, the absolute value v2 of the voltage V2 in the equation (5) can use the value detected by the voltage transformer 4. After the real number component e2 of the voltage V2 is known, the transmission loss pL is calculated by Eq. (4) and this is set as the current transmission loss pLp. Then, operate the tap of the voltage regulator 10 once to set the absolute value v2 of the voltage V2 to the voltage adjustment amount Δ.
Calculate the predicted transmission loss when changing by _v . For this, the estimated voltage after change is set as v2 in Eq. (5), the corresponding real number component e2 is calculated, and then the predicted transmission loss p is calculated by Eq. (4).
Just ask for L.

Since the index calculation means 40 calculates the increase / decrease index d of the transmission loss pL with respect to the unit increment of the voltage V2 that is the adjusted voltage,
This can be achieved by differentiating the transmission loss pL with respect to the absolute value v2 of the voltage V2 by the equation (4).

Or as a more easily calculated form Becomes Even if the increase / decrease index d is obtained by this equation (7),
Since the real component e2 of the voltage V2 is required, the transmission loss calculation means
In the same manner as in the case of 30, the increase / decrease index d is calculated after obtaining this.

The comparators 51 and 52 and the AND gate 53 shown below the various means in FIG. 1 are schematic circuit elements of the function, and the comparator 51 calculates the current transmission loss pLp and the voltage calculated by the transmission loss calculating means 30. The comparator 52 determines the magnitude relationship with the predicted transmission loss pL after the adjusting operation via the adjusting device, and the comparator 52 compares the increase / decrease index d calculated by the index calculating means 40 with a predetermined limit value δ. If the predicted power transmission loss pL is larger than the current power transmission loss pLp, there is no meaning to make an adjustment operation, and the AND gate 53 is not opened. Further, since the current transmission loss pL is a value that has already been minimized, and therefore there is no point in performing the adjusting operation even when the increase / decrease index d is close to 0 and smaller than the limit value δ, the AND gate 53
Can't open. That is, in the present invention, the predicted transmission loss pL is smaller than the current transmission loss pLp and the increase / decrease index d is the limit value δ.
The AND gate 53 is opened to cause the voltage regulator 10 to perform the tap switching operation only when the voltage is larger than the above.

Of course, the above operation is repeated until the power transmission loss pL is minimized. When the power transmission loss pL is minimized, the increase / decrease index d falls below the limit value δ, or the predicted power transmission loss pL exceeds the current power transmission loss pL, and the voltage regulator 10 is no longer operated. In this manner, in the present invention, it is always checked whether or not the operation is effective before the voltage regulator 10 actually performs the tap switching operation, so that the wasteful tap switching operation is performed as in the conventional case. Therefore, the power transmission control is always stable and reliable, which solves the above-mentioned problems.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, as shown in FIG. 1, both end nodes of the power transmission line 1 connecting the power generation device 2 and the load 3. It is assumed that the voltage adjusting device 10 is placed on the power receiving end node N2 side in N1 and N2, and the specific node where the power flow is detected by the power detecting means 20 is also the power receiving end node N2.

FIG. 2 illustrates the hardware of the power control device 100 suitable for implementing the present invention. The detected values of the voltage V2 and the current I2 of the node N2 from the voltage transformer 4 and the current transformer 5 are input to the two terminals shown in the upper right part of the figure, and the three analogs shown below are input. It is provided by the transducers 61 to 63, which convert it into a DC voltage signal representing the active power p2, the reactive power q2 and the absolute value v2 of the voltage V2, respectively. These signals are further converted by the analog-to-digital converter 65 via the changeover switch 64 into a digital signal. The microcomputer 70 includes the power transmission loss calculating means 30 and the index calculating means 40 in the form of software according to the present invention, and includes a CPU 71, a bus 72, a ROM 73, a RAM 74, etc. as usual, and an input / output port 75.
A changeover command is issued to the above-mentioned changeover switch 64 via to read the values of active and reactive powers p2, q2 and voltage v2. RO
An area 73a for storing circuit parameters of the transmission line in M73
Is set. In addition to this, an operation display panel 80 and a printer 85 for data logging are provided in the power control device 100, and the operation display panel 80 has a keyboard 81 and a display 8.
2. An operation switch 83 and a printer controller 84 are included and connected to the input / output port 76 of the microcomputer 70. The output relay 90 receives a signal from the microcomputer 70 via the input / output port 75, and issues a tap raising / lowering operation command TC to the voltage regulator 10.

Next, referring to FIG. 3, the control operation according to the present invention will be described in accordance with the flowchart of FIG. FIG. 4 exemplifies the flow of the microcomputer 70, and the flow shown in the drawing is constantly repeated during the operation period of the transmission line.

In the first step S1 in FIG. 4, a changeover command is sent to the changeover switch 64 to read the value of the node voltage v2 from the analog transducer 63 via the analog digital converter 65, and this is read as the current voltage value v2p into the RAM 74. Remember. In the next step S2, 0 is set to the flow switching flag F shown in the figure. The following step S3 is the operation as the power detection means 20, and similarly to the previous step S1, sends a command to the sequential changeover switch 64, and the analog transducers 61, 62
The values of the active power p2 and the reactive power q2 from are read via the analog × digital converter 65. Note that the previous step S1
Including various values, various values v2, p2, q2 are assumed to be stored in the microcomputer 70 after being read and then normalized by the unit method. Further, in this step S3, the voltage value v2 is used as a kind of variable and the value of the current voltage v2p previously stored in FIG.

The next step S4 is a common operation step for the transmission loss calculation means 30 and the index calculation means 40, and the equation (5) is used as the known amount of the active and reactive powers p2 and q2 detected in the previous step S3. By solving the two binary components e2 and f2, the voltage V2
Compute the real part e2 of. The following step S5 is a step as the power transmission loss calculating means 30, which calculates the power transmission loss pL by the equation (4) using the voltage value v2 and the real part e2 that have just been obtained. Step S6 is a flow switching step, and it is determined whether or not the value of the flag F is 0. In this case, the flag F is still 0.
Therefore, the flow moves to step S6. This step S6 is an operation step as the index calculating means 40, and the number of increase / decrease index d is calculated by the formula (7) using the known quantities v2 and e2 as in the previous case. Then, in step S8, it is determined whether the absolute value of the calculated increase / decrease index d is smaller than the limit value δ. If the value of the transmission loss pL is close to the value that has already been minimized and the value of the increase / decrease index d is smaller than the limit value δ, there is no need to operate the voltage adjustment device 10, so in this embodiment, the flow The process returns to the first step S1 and the same operation as above is repeated until the need for operation arises.

When the value of the increase / decrease index d is greater than or equal to the limit value δ, the flow moves from step S8 to step S9, where flag F is set to 1 first.
Stand up. In the following step S10, the value of the power transmission loss pL calculated in step S5 is stored as the current power transmission loss pLp. In the next step S11, whether the increase / decrease index d is positive or negative is determined. If the increase / decrease index d is negative, the transmission loss pL tends to decrease to the right with respect to the voltage v2 as shown in FIGS. 3 (a) and 3 (c). Is replaced with a value obtained by adding the voltage adjustment amount Δ _v to If the increase / decrease index d is positive, as shown in Fig. 3 (b) and (d), transmission loss
pL replace in step S13 because there is a tendency of upward-sloping or downward to the left of the voltage v2 with the value obtained by subtracting it from the voltage adjustment amount delta _v. In any case, this replaced voltage v2 is the expected voltage after voltage adjustment,
After S12 or step S13, the flow is returned to step S4. In the second step S4, the replaced v2 is used as a new known quantity, and the equation (5) is solved in the same manner to obtain the value of the real part e2 corresponding to the value of the voltage v2. Based on both values v2 and e2 in step S5. Calculate the estimated transmission loss pL. From the following step S6,
Since the flag F was previously set to 1 in step S9, the flow goes to step S14.

Steps S14 to S17 are steps for instructing a tap switching operation for the voltage regulator,
Before the command is issued, first, in step S14, the necessity of operation is determined based on whether the predicted power transmission loss pL is smaller than the current power transmission loss pLp. The judgment result is negative, that is, as shown in Figs. 3 (c) and (d), the voltage
If the power transmission loss is warped and becomes worse when v2 is operated, the operation is stopped and the flow is returned to step S2. During this return
The value of the adjusted voltage v2 at that time may be read again. When the value of the predicted transmission loss pL is smaller than the current value of the transmission loss pLp and it is worth operating the regulated voltage, the flow moves from step S14 to step S15. In this step S15, it is determined whether the voltage to be adjusted should be increased or decreased, as can be seen from FIGS. 3 (a) and 3 (b), based on whether the increase / decrease index d is positive or negative.
When the increase / decrease index d is negative, the tap-up command T is issued in step S16.
When the increase / decrease index d is positive, a tap down command TC is output through the output relay 90 in step S17.
To leave. Since it takes some time to switch the voltage adjusting device 10 based on this operation command TC, after the step S16 or step S17 on the side of the microcomputer 70, a slight margin time is provided as schematically shown by a chain line in the figure. After the operation of the soft timer for the operation or the step of waiting for the operation completion report from the voltage regulator, the flow proceeds to the first step S1.
Return to.

As described above, one tap switching operation for minimizing the power transmission loss is completed, but of course, the above operation is repeated until the power transmission loss is minimized. In addition, when calculating the quantities e2, pL, d in steps S4, S5, and S7 in the above-mentioned flow, Y is set as the circuit parameter of the transmission loss.
The values of the real part g11 and the imaginary part b11 of the admittance such as 11 are required, but these values are written in the ROM 73 in the microcomputer 70 and are transferred to the RAM 74 at the start of the flow of FIG. It is better to change it. Since the transmission line is often operated by switching between one line and two lines, two circuit parameters are set in advance for RO.
It is stored in M73, and one of them is designated in advance by the operation switch 83 on the operation display panel 80 according to the operating state of the power transmission line before starting the flow. In addition, these circuit parameters themselves are also stored in the ROM 73 after the impedance admittance of the power transmission line is input to the microcomputer 70 via the keyboard 81 in advance and converted into the circuit parameters as in the embodiment. In addition, the operation switch 83 allows the amount in the middle of the flow in FIG.
It is convenient to set it to be displayed on the screen 82 or to be logged by the printer 85.

In addition to the embodiments described above, the present invention can be carried out within the scope of the present invention in various modified modes. I mentioned above
The formulas (1) to (7) all differ depending on the type of equivalent circuit that simulates the transmission line and the method of inducing the formula. Since the formula for calculating is also different accordingly, any formula should be understood as an example of a calculation formula. The operation flow shown in FIG. 4 can be modified in various ways. For example, except for step S8, the operations from step S9 to step S13 are performed regardless of the value of the increase / decrease index d, and then step S6. From step S14 to step S14, whether or not the tap switching operation is necessary or not may be determined based on the magnitude relationship between the value of the current transmission loss pLp and the value pL + δ obtained by adding the limit value δ to the value of the predicted transmission loss pL. .

〔The invention's effect〕

As described above, in the present invention, the effective power flow rate at the specific node of the power transmission line by the power detection means,
Based on the detected values of both the reactive components, the voltage adjustment device calculation means calculates the current transmission loss and the predicted transmission loss when the adjusted voltage in the node where the voltage adjustment device is installed is calculated, and the index calculation means After calculating the increase / decrease index that shows the increase / decrease tendency of the transmission loss, when the increase / decrease index exceeds the limit value and the transmission loss is not minimized, and the predicted transmission loss is less than the current transmission loss Since the voltage adjustment device is made to perform the tap switching operation only for a limited time, there is no fear that the voltage adjustment operation of the wasteful transmission line is performed unlike the conventional case, and the transmission loss is minimized while operating the transmission line system stably. be able to. In addition, since it is essentially unnecessary to set a dead zone for control in order to avoid control hatching as in the conventional case, according to the present invention, transmission loss can be performed with high accuracy while fully utilizing the function of the voltage regulator. Can be minimized. Furthermore, all the main means used by the present invention are performed by a digital circuit such as a microcomputer in the power control device, and the circuit parameters of the power transmission line are also stored digitally, so that the setting of the circuit parameters can be performed for multiple lines. Also, there is no fear of causing an error and it is possible to easily make a fine change in the control operation on the transmission line.

[Brief description of drawings]

The drawings are all related to the present invention. FIG. 1 is a schematic circuit diagram showing a power transmission line and a functional configuration of the present invention, and FIG. 2 is a hardware configuration example of a power control device suitable for carrying out the present invention. Fig. 3 is a block circuit diagram showing Fig. 3, Fig. 3 is a diagram showing an example of the relationship between power transmission loss and regulated voltage, and Fig. 4 is a flow chart illustrating the operation of the present invention. In the figure, 1: transmission line, 2: power generator, 3: load, 4: voltage transformer for voltage detection of specific node, 5: current transformer for current detection of specific node, 10: voltage regulator or tap at load Switching transformer, 20: Power detection means, 30: Transmission loss calculation means, 4
0: exponent calculation means, 61: active power detection analog transducer, 62: reactive power detection analog transducer, 63: voltage detection analog transducer, 64:
Changeover switch, 65: Analog-to-digital converter, 70:
Microcomputer, 73: ROM, 73a: Circuit parameter storage area of transmission line, 80: Operation display panel, 85: Data logging printer, 90: Output relay, b, b11, b12, b2
2: imaginary part of admittance, d: increase / decrease index, δ: limit value for increase / decrease index, e2: real part of voltage at specific node,
f2: imaginary part of voltage at specific node, g, g11, g12, g22: real part of admittance, 11: current at node N1, 1
2: Current at specific node N2, N1: Power transmission end node, N
2: Power receiving end node or specific node, pL: Transmission loss or predicted transmission loss, pLp: Current transmission loss, p2: Effective power flow rate at specific node, q2: Reactive power flow rate at specific node, S3: Power detection means Operation step as
S4: Operation step shared by transmission loss calculation means and index calculation means, S5: Operation step as transmission loss calculation means, S
7: Operation step as exponent calculation means, V1: Node N1
, V2: voltage of the specific node N2, v2: absolute value of the specific node voltage or the adjusted voltage, Δ _v : one-time voltage adjustment amount by the voltage adjusting device for the adjusted voltage, Y, Y11, Y12, Y2
2: Admittance as a transmission line circuit parameter, W
1: power flow at node N1, W2: power flow at node N2.

Claims (1)

[Claims] 1. A method for controlling power transmission so as to minimize power transmission loss through a voltage regulator provided at one of both end nodes of a power transmission line having known circuit parameters, the method being effective at a specific node. , A power detection means for detecting a flow rate of power composed of both reactive components, and a power transmission line based on the power detected by the means, the circuit parameter of the power transmission line, and the adjusted voltage on the node side for which the voltage should be adjusted. Transmission loss calculation means for calculating the power loss of the transmission line, and index calculation means for calculating an increase / decrease index indicating the amount and direction of increase / decrease in the transmission loss per unit increment of the adjusted voltage based on the circuit parameter of the transmission line and the adjusted voltage. And the current value as the adjusted voltage and the planned value obtained by changing the current value by the predetermined voltage adjustment amount by the voltage adjusting device are given to the transmission loss calculating means, and the corresponding current transmission loss and the voltage adjustment corresponding to them are given. When the predicted transmission loss is less than the current transmission loss and the increase / decrease index value exceeds a predetermined limit value, the voltage regulator is adjusted according to the positive / negative sign of the increase / decrease index. A power transmission control method, wherein a voltage is increased or decreased by the voltage adjustment amount.