JP2815872B2 - Power system monitoring and control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a power system monitoring and control system that supports stable and reliable supply of high-quality electricity.

(Prior Art) When monitoring a system voltage with a conventional power system monitoring and control system, a current state of the system voltage is displayed, and whether or not this is within a range between an upper limit value and a lower limit value of a voltage target value. Is monitored, and an alarm is issued when it is out of the range.

(Problems to be Solved by the Invention) As described above, in the conventional system, no consideration is given to the stability of the system voltage at a future point several minutes to several hours ahead of the present. This is because there was no method for quantitatively predicting the state of the system at a future time, and there was no general method for obtaining the stability of the system voltage. Therefore, it is inevitable for the operator to determine whether or not the system voltage can be maintained stably at a future point in time. However, it is extremely difficult to make a correct determination in practice. There is a risk of missing the opportunity for the treatment necessary to perform the treatment.

The present invention has been made in view of the above circumstances, automatically predicts the state of the system at a future time, determines the stability of the system voltage, if the system voltage at the future time is determined to be unstable, Find the controlled equipment and control amount necessary for stabilization,
An object of the present invention is to provide a power system monitoring and control system that assists a more stable operation of a power system by preliminarily controlling a controlled device according to those results.

[Structure of the Invention] (Means for Solving the Problems) A structure for achieving the above object will be described with reference to FIG. 1. In the present invention, system information from a power system is transmitted to an electronic computer via an information transmission device. In the power system monitoring and control system that inputs and processes based on each of these information and outputs various data on the voltage stability to the display device, the system information is transmitted from the system information transmitted via the information transmission device (S10). A system state determining means (S20) for determining the state of the monitored power system, and storing the results of the system state determining means, and using the system state determining means for consuming the total demand and load at a future time several minutes to several hours later. The future system state prediction means (S30) for obtaining the control states of the power, reactive power, and voltage regulating devices, and the demand power P and the bus voltage V for the future power system state obtained by the future system state prediction means. -V curve The stability limit calculating means for calculating a stability limit voltage (S40) to the future system condition based on the line connecting the midpoint of the more enhanced solution and lower solution,
Stability monitoring means for determining the level of the voltage stability of the system at a future time point based on how far from the stability limit in the stability region the stability limit at the future time point determined by the future system state prediction means (S50) and the controlled equipment and control amount required to stabilize the voltage of the system at a future time when it is determined to be unstable, or to increase the stability when the voltage is determined to be close to unstable (S60), control amount transmitting means (S70) for transmitting a control signal corresponding to the control amount to the controlled device in the power system, and means for outputting the data to the operator ( S80).

(Operation) Various measurement values indicating the state of the power system measured at various points in the power system by the power system information transmitting means are collected and passed to the system state determining means. The system state determination means determines the state of the power system using a measurement value including an error in the state of the power system input from the power system information transmission means, and the future system state prediction means based on the result of the system state determination means. The system status at a future time is determined.

The stability limit calculation means obtains the voltage stability limit using the result of the future system state prediction means as an initial value, and the stability monitoring means uses the result of the future system state prediction means and the result of the stability limit calculation means to calculate the voltage stability limit in the future. The voltage stability of the power system at the time is determined. If it is determined that the system voltage at the future time is unstable, to make it stable, or if it is determined that the level is near unstable, the control amount calculation means uses the result of the stability monitoring means and the future system state prediction means. Using the results of (1) and (2), a controlled device and a control amount necessary for stabilizing the system voltage at a future time are obtained, and the control amount transmitting unit transmits the obtained control amount to the corresponding controlled device to transmit them. The output means outputs various results of the above means to a man-machine interface device (hereinafter referred to as an MMI device).

(Example) Hereinafter, an example is described with reference to drawings. FIG. 2 will be described for convenience of explanation. FIG. 2 is a configuration example of a power system monitoring and control system according to the present invention.

In FIG. 2, reference numeral 1 denotes a power system, which is an information transmission device 2 that measures the state of the power system and transmits the measured value.
1, an information transmission device 2-2 that receives the information via the transmission line 3, an electronic computer 4 that receives the information and performs a process related to the voltage stability, and a man that displays a processing result of the electronic computer 4. Machine interface device (MMI) 5
Consists of

The measurement information from the power system includes, for example, the voltage and output of the generator, the active power and reactive power of the load, the active power flow, the reactive power flow, the bus voltage, the open / closed state of circuit breakers and disconnectors, and the There are tap positions and the like. Therefore, the computer 4 inputs the respective current measurement information from the power system,
Based on this current information, the prediction data of the future power system state several minutes or several hours ahead is processed for voltage stability described later, and the resulting data on various voltage stability is displayed on the MMI device. I do.

FIG. 1 is a flow chart showing the processing contents concerning the voltage stability of the electronic computer. In FIG. 1, the system information transmission processing S10 includes the generator output and voltage measured at various points in the power system, the active power consumed by the load, the reactive power, the active power flow flowing through the transmission line and the transformer, the reactive power flow, and the bus. Voltage,
It transmits the open / closed state of circuit breakers and disconnectors, and tap positions of transformers. Since the system status determination process S20 has a variation in the measurement value including the error and the measurement time input in the system information transmission process S10, the weighted least squares estimation is performed using the measurement values including the contradiction between these measurement values. The most probable state value of the power system is obtained by the method.

The future system status prediction process S30 stores the result of the system status determination process S20 as measurement data of the system status, and uses it by itself to obtain total demand at a future time several minutes to several hours later, active power consumed by the load, and reactive power. The power, generator output, and control status of the voltage regulator are determined. Stability limit calculation processing S40
Calculates a voltage stability limit for the future power system state obtained in the above-described future system state prediction processing S30 by using a PV curve of the demand power P and the bus voltage V. It should be noted that the PV curve created in this case is created in consideration of the morphological state at a future point in time, and is not the PV curve currently used.

The stability monitoring process S50 determines the level of the voltage stability of the system at the future time based on how far away from the stability limit in the stability region at the boundary of the voltage stability limit at the future time, and the control amount calculation process S60 When it is determined that the voltage of the system at a future time is unstable, the controlled device and the control amount necessary to stabilize the voltage or to increase the stability when the voltage is determined to be nearly unstable are determined. Control amount transmission processing S70
Sends the result of the control amount calculation processing S60 to the controlled device in the power system, and the output processing S80 is the processing S20, S30, S40, S50, S60
Are output to the MMI device 5. The details of the procedure for each process will be described below.

The measurement data of the power system received via the information transmission devices 2-1 and 2-2 usually includes a conversion error of the transducer, and an error due to a failure or an irregular measurement time. . Therefore, in the system state determination processing S20, the most probable system state values, that is, the node voltage and the phase angle of the voltage, are determined by the weighted least squares estimation method, that is, the state estimation calculation, from the measured values including these errors. . Generally, a measurement value including an error can be expressed as follows.

 z = h (x) + ε (1) where z is a vector of measured values.

x: True value of the state variable, that is, a vector of the node voltage and its phase angle.

h (x): Vector of functions for finding the true value of the measured value from x.

ε: vector of measurement error.

In this case, the sum of squares of the residuals between measured and the estimated value, J = (z-h ( x)) t w (z-h (x)) ...... (2) where, w: the respective measurement value Error weight matrix.

 zh (x): vector of residuals of measured values.

 t: Indicates transposition of a vector.

Is obtained as the estimated value x of the state variable x that minimizes Next, an estimated value of the power flow is obtained from the obtained x. By the above procedure, a more reliable state of the power system in which the influence of the error included in the measurement value is removed can be obtained.

Based on the current system state determined by the system state determination processing S20, the future system state prediction processing S30 determines the control state of the load power, the generator voltage, and the voltage adjustment device at a future point several minutes to several hours later by the following procedure. Ask.

(1) The load power after Δt with respect to the predicted current time t of the load power and the generator voltage at the future time is: _{Q L (i, t + Δt} ) = Q L (i, t) + _{[P LF (i, t + Δt} ) · P L (i, t + Δt) -P LF (i, t) P L (i, t) ] ...... (4) Here, P _L (i, t): active power at time t of load i.

Q _L (i, t): reactive power at time t of load i.

P _LF (i, t): Load power factor statistical value at time t of load i.

S _L (t): Total demand at time t.

At this time, the load power factor statistical value and the total demand use values statistically obtained from past data accumulated and classified according to season, day of week, time, and the like.
The result of 0 is accumulated and the statistical data is updated. Next, the generator voltage is selected from the operation value at the future time from the operation reference value pattern of the automatic voltage regulator (AVR), and the power flow is calculated under these constraints. It can be regarded as a future state of the system when the response of the voltage regulator is ignored.

(2) Prediction of control status of voltage regulators Determine the control status of voltage regulators such as capacitors, reactors, transformer taps, and generator exciters at a future time. Each of the voltage regulators responds so as to maintain the system voltage obtained from the power flow calculation performed in the above procedure (1) at the operation reference value. By introducing the amount of change in the system voltage when the amount is adjusted by the unit amount, that is, the voltage sensitivity coefficient _Aij , the value is obtained by solving the equation (5).

V _si = V _oi + A _ij Δx _j (5) where A _{ij is} a voltage sensitivity coefficient of the bus i with respect to the voltage adjustment device j.

Δx _j : Control amount change of the voltage adjusting device j from the current time point to the future time point.

V _si : Operation reference voltage of bus i.

V _oi : The voltage of the bus i when the response of the voltage regulator is ignored.

Next, the voltage sensitivity coefficient is obtained by the following method. Before and after the adjustment, the sum F of the active power flowing into and out of the node and the sum G of the reactive power are always zero, so that before the adjustment: F (V, _Cq , θ) = 0 (6) G (V, C _q , θ) = 0 (7) Here, F and G are vectors.

Adjusted: the _{F (V + ΔV, C q} + ΔC q, θ + Δθ) = 0 ...... (8) G (V + ΔV, C q + ΔC q, θ + Δθ) = 0 ...... (9). Here, Δ indicates a change in each amount before and after adjustment, and V: node voltage.

 θ: phase angle of the node voltage.

C _q : a reactive power-related adjustment variable such as a capacitor (SC) and a reactor (ShR).

Then (8), Expanding retailer to (9), F (V + ΔV, C q + ΔC q, θ + Δθ) = F (V, C q, θ) + F v · ΔV + F cq · ΔC q + F θ · Δ θ ... ... the (10) G (V + ΔV , C q + ΔC q, θ + Δθ) = G (V, C q, θ) + G v · ΔV + G cq · ΔC q + G θ · Δ θ ...... (11). _{Here, F v, F cq, F} θ, G v, G cq, G θ: Taylor is a matrix of the expansion coefficients.

Thus, an _{F v · ΔV + F cq ·} ΔC q + F θ · Δθ = 0 ...... (12) G v · ΔV + G cq · ΔC q + G θ · Δθ = 0 ...... (13), on or release of the SC or ShR In the case of, since F _cq = 0, Δθ is eliminated from the expressions (12) and (13), and ΔV / ΔC _q = − (G _v −F _θ ⁻¹ · F _v ) ⁻¹ · G _cq . … (14) Here, V and θ use the result of the power flow calculation in the above procedure (1). From equation (14), the voltage sensitivity coefficient A of equation (5)
_ij is obtained as an element of the matrix ΔV / ΔC _q .

(3) Determination of the system state at a future time For the system state obtained in the above procedure (1), the control amount of the voltage regulator obtained in the above procedure (2) is set and power flow calculation is performed. The system status at the time is assumed. If the power flow calculation does not converge, the stability monitoring process S50
To that effect.

Next, what the stability limit calculation process S40 sets as an index indicating the voltage stability and how to obtain the index will be described.

The power flow equation is a nonlinear simultaneous quadratic equation, and it is generally known that a plurality of solutions exist. Here, the relation between the total power demand and the voltage of a certain bus in the system is expressed as shown in FIG. 3, and under a certain total demand cross section, the power flow equation is expressed by two voltages as shown in FIG. Has a solution. In this embodiment, a higher solution is referred to as a higher solution and a lower solution is referred to as a lower solution. The higher solution is a stable voltage solution and the lower solution is a unstable voltage solution.
Defined as the voltage stability limit.

First, a state when the demand is increased by a certain amount is obtained from the future system state at the point in FIG. 3 obtained by the future system state determination processing S30. In this case, a method of obtaining a future system state will be described with reference to FIG. 3 showing the relationship between the total demand and the system voltage. That is, an economic load distribution calculation is performed for the increased demand, the output of the generator is determined, and the active power and the reactive power of the load are determined based on the distribution coefficient and the power factor of the load with respect to the total demand of the load. It is a higher solution of the result of performing the tidal current calculation under the condition. As described above, the calculation is sequentially performed until the solution of the power flow calculation cannot be obtained by increasing the demand. The result is,

Next, a lower solution corresponding to ,,,
Ask for Generally, when solving a second-order or higher-order equation by a successive correction method such as the Newton-Raphson method, the initial value of the solution is determined as to which solution is obtained out of a plurality of solutions.
That is, since it is determined by the first approximation, a lower solution can be obtained by reducing the initial values of the node voltage and its phase angle. The solution of is taken as an initial value for finding the solution of, the solution of is taken as the initial value for finding the solution of, and the solution of is taken as the initial value for finding the solution of
Find the points of,. An intermediate point between the intermediate point of the intermediate point and the intermediate point of the intermediate point is defined as a stability limit.

Here, the necessity of determining the voltage stability with respect to the future system state will be described. First, the reason from the point of operation of the power system will be described. If measures are taken after the voltage becomes unstable, control of the voltage regulator will not be effective in restoring the voltage stability due to the characteristics of the power system. Only the undesired measures of stabilizing the rest of the system are effective. Therefore, when the voltage stability of the system is predicted in the future and it is predicted that the voltage will be used in an unstable state, if the control is performed preventively before the voltage becomes unstable, it will be stabilized by controlling the voltage regulator. And the above-mentioned undesirable countermeasures can be avoided.

Next, the reason why the voltage stability at the future time cannot be predicted by using the PV curve in the current state will be described in terms of the technology of the voltage stability analysis. When the power flow calculation for plotting the PV curve is repeated, the equipment related to the adjustment of the reactive power and the voltage, that is, the input amount of the phase adjusting capacitor and the reactor, the tap position of the transformer, the synchronous phase adjuster voltage and the generator voltage. In general, the power flow is calculated while fixing the state.

That is, only the active power and reactive power of the load and the generator output accompanying the increase in the total demand change the condition. This means that even if the active power and reactive power of the load and the generator output are the same, the bus voltage will be different if the input of the phase-adjustment capacitor and reactor, the tap position of the transformer, the synchronous phase adjuster voltage and the generator voltage are different. Different, different P-
Since it becomes a V curve, the amount of input of phase-adjusting capacitors and reactors to evaluate voltage stability under certain conditions,
It is a typical method to calculate the PV curve by fixing the tap position of the transformer, the synchronous phase adjuster voltage and the generator voltage.

For the current system state, a PV curve is created using the input amounts of phase adjustment capacitors and reactors, transformer tap positions, synchronous phase adjuster voltage, and generator voltage determined by the system state determination process S10. It is usual to do. For the predicted future system state, the current system state is calculated using the input amount of the phase-adjusting capacitor and reactor, the tap position of the transformer, the synchronous phase adjuster voltage and the generator voltage determined by the future system state predicting means S20. Create a PV curve different from that of. In the current system status and the predicted future system status,
If the value of the total demand is different, for example, when the demand increases, the system voltage will decrease. Therefore, the operation of individual control equipment, such as individual VQC, the input of the phase-adjustment capacitor and reactor, the tap position of the transformer, the voltage of the synchronous phaser, and the power generation The machine voltage is usually adjusted.

According to the present invention, the response of the voltage regulator is predicted, and the input amount of the phase-adjusting capacitor and the reactor with respect to the future system state,
The transformer tap position, synchronous phase adjuster voltage and generator voltage are determined. As described above, if the magnitude of the total demand differs between the current state and the predicted future system state, the input amounts of the phase-adjusting capacitors and reactors, the tap positions of the transformers, the synchronous phaser voltage, and the generator voltage are different. As shown in FIG. 5, different PV curves are obtained.

That is, the current system PV curve is a curve of, and the future predicted system PV curve is a curve of. The current state on the current system PV curve is a point determined by the system state determination means S10, and the predicted current state at a future point on the future predicted system PV curve is determined by the future system prediction means S20. Is a point. The above is the reason why it is necessary to predict the system state and determine the voltage stability at a future time.

The stability monitoring process S50 determines the voltage stability at a future time. If the power flow calculation performed in step (3) of the future system state prediction processing S30 does not converge, there is no voltage solution under such demand, that is, the power system cannot be operated. Therefore, it is determined that the voltage is unstable.

On the other hand, if the voltage is not unstable, the voltage stability of the power system at a future time is different from the stability limit voltage VSL as shown in FIG. 4 obtained by the stability limit calculation process S40. Is evaluated for the following items.

(1) voltage stability _{IVS = V t -VSL (P t} ) ...... (15) V t: future system voltage.

 VSL (P): stability limit voltage.

 P: Gross demand.

P _t : Future total demand.

(2) Determination of stability level The stability level of the system voltage of the future power system is determined using the voltage stability IVS. That is, the state of the voltage stability of the future prediction system, that is, which of the areas of the stable state, the stability attention, and the stability warning shown in FIG. 4 is included in the magnitude of the IVS is determined. I do.

The stable state, stability caution, and stability warning areas shown in FIG. 4 are levels at which the operator can know how stable the power system is in operation, and are determined based on the operation plan for the year. .

When the stability monitoring process S50 determines that the system voltage at the future time is unstable, the control amount calculation process S60 obtains the load cutoff amount necessary to maintain the stability. In the operation of the power system, the load to be cut off in an emergency is determined in advance based on a certain weight.
If the load is gradually cut off until the power flow calculation in the procedure (3) of the future system state prediction processing S30 converges, a necessary load cutoff amount is obtained.

On the other hand, if it is determined by the stability monitoring process S50 that the system voltage at a future time is in the stable region, the control amount calculation process S60 includes a capacitor, a reactor, a tap of a transformer,
A device for adjusting the system voltage, such as a generator exciter, determines the amount of the effect of increasing the voltage stability. As can be seen from FIG. 4, the voltage stability is increased by increasing the voltage of the power system. That is, the higher the system voltage is above the stability limit voltage, the more stable the system voltage becomes.

Therefore, how much the system voltage rises when the voltage adjusting device is adjusted by a unit amount, that is, the voltage sensitivity coefficient is an effect amount for improving the stability. The voltage sensitivity coefficient is obtained by the same method as shown in the procedure (2) of the future system state prediction processing S30. Further, when it is determined by the stability monitoring process S50 that it is necessary to improve the stability of the system voltage, the control amount calculation process S60 obtains an adjustment amount R necessary for improving the stability.

The determination of the necessity of the stability improvement is performed as follows. For example, when the voltage stability level of the future system is at the stability alert level in FIG. 4, or at the stability alert level or the stability alert level. The actual level at which improvement is required is determined by the grid operator. The amount of voltage increase VUP required to maintain the system voltage sufficiently stable is determined as follows from the voltage stability IVS obtained by the stability monitoring process S50.

 VUP = −IVS + α (16) α: safety factor.

Next, when stabilizing by turning on the capacitor (SC), control is performed by R = VUP ÷ (ΔV / ΔC _q ) (17) using ΔV / ΔC _q shown in the procedure (2) of the process S30. Determine the quantity R.

The control amount transmission process S70 sends the result of the control amount calculation process S60 to a controlled device included in the power system to control. Output processing
S80 converts the various results of the processes S20, S30, S40, S50, S60 into CRs.
Display on the T screen. In short, according to the present embodiment, the system state and the voltage stability at the future time are automatically calculated, and based on the result, the controlled device is controlled in advance to stably maintain the system voltage. Electric power can be supplied more stably.

[Effect of the Invention] As described above, according to the present invention, the control of the voltage of the power system is performed in advance, so that the operator can be notified of the operation state of the system in advance. As a result, higher quality power supply becomes possible.

[Brief description of the drawings]

FIG. 1 is a flow chart showing the contents of processing relating to voltage stability performed by the present invention, FIG. 2 is a diagram showing an example of the configuration of a power system monitoring and control system according to the present invention, and FIG. 3 is a diagram showing the relationship between demand and system voltage. FIG. 4 is a diagram showing a voltage stability level, and FIG. 5 is a diagram showing a PV curve at a present time and a P-V curve at a future time.
It is a figure which shows the relationship of -V curve. S10 ... System information transmission processing, S20 ... System state determination processing S30 ... Future system state prediction processing, S40 ... Stability limit calculation processing S50 ... Stability monitoring processing, S60 ... Control amount calculation processing S70 ... Control amount transmission processing, S80 …… Output processing

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Kato 1-3-3 Uchisaiwai-cho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Inventor Tadashi Ichikawa 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba-fu Naka Factory (72) Inventor Masahiro Sato 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Nakashi Plant, Toshiba Fuwa Co., Ltd. (72) Wakako Suzuki 1-1-1, Shibaura, Minato-ku, Tokyo Inside the Toshiba head office (56) References JP-A-62-110838 (JP, A) JP-A-61-121720 (JP, A) JP-A-55-159270 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name ) H02J 3/00

Claims (1)

(57) [Claims] 1. A power system which inputs system information from a power system to an electronic computer via an information transmission device, processes the information based on the information, and outputs various data on voltage stability to a display device. In the monitoring and control system, a system state determination unit that determines a current system state of the monitored power system from system information transmitted via the information transmission device, and a state of a future power system based on the current system state described above. Future system state prediction means for predicting, stability limit calculation means for obtaining a voltage stability limit based on a PV curve of demand power P and bus voltage V for the future system state, and stability limit calculation means A stability monitoring method that determines the voltage stability level of the system at a future time point based on how far away from the stability limit in the stability region at a predetermined voltage stability limit at the future time. When the voltage of the system at a future point in time is determined to be unstable, a controlled device and a control amount required to stabilize the voltage or to increase the stability when the voltage is determined to be close to unstable are determined. A control amount calculating unit, a control amount transmitting unit that transmits a control signal corresponding to the control amount to a controlled device of a power system, and a unit that outputs the data to an operator. Grid monitoring and control system.