JP2647156B2 - 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, the stability of the system voltage is left to the judgment of the operator. However, there was no way to know where the voltage stability limit was, so when the power system state became unusual in the past, such as when the load became unpredictably heavy or when the load suddenly changed Occurs, it may be uncertain whether the system voltage can be maintained stably depending on the situation.

The present invention has been made in view of the above circumstances, and provides various data regarding the stability of voltage of a power system, and provides a power system monitoring and control system capable of monitoring and operating a higher quality power system. It is an object.

[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. A power system monitoring and control system that inputs, processes based on each of these information, and outputs various data on voltage stability to a display device. A system state determining means (S10) for obtaining a state of the system, and a PV curve showing a relationship between a system demand P and a system voltage V based on the obtained system state. A stability limit calculating means (S20) for determining a voltage stability limit based on a line connecting an intermediate point between a higher solution and a lower solution of the curve, and how much from the stability limit in the stability region with respect to the voltage stability limit Cheap depending on how far away Stability monitoring means for determining the stability of the system voltage to determine the level of degree and (S30),
An effect amount calculating means (S40) for obtaining an effect amount indicating how much the system voltage rises when the device for adjusting the system voltage is adjusted by a unit amount; An adjustment amount calculating means (S50) for obtaining an adjustment amount required for stabilizing the device when in a stable state;
And output means (S60) for outputting various data as the results of the respective calculations.

(Operation) First, the system state determination means determines the information of the power system using the measurement value including the error of the information of the power system input from the information transmission apparatus, and then the voltage stability limit calculation means determines the system state of the power system. The voltage stability limit is obtained using the result of the determination means as an initial value. Next, the stability monitoring means determines the level of the voltage stability of the power system using the system state determination means and the result of the voltage stability limit calculation means, and the effect amount calculation means further uses the result of the system state determination means. The voltage regulator determines the effect amount for increasing the voltage stability, and the adjustment amount calculating means uses the result of the stability monitoring means and the effect amount calculating means to adjust the amount of adjustment necessary for stabilizing the unstable voltage state. Finally, the output means outputs various results of the above means to a man-machine interface device such as a CRT.

(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 electric computer 4. It consists of a machine interface device (MMI). The measurement information from the power system includes, for example, generator voltage and output, load active power and reactive power, active power flow, reactive power flow, bus voltage, open / closed state of circuit breakers and disconnectors, and There are tap positions and the like.
Accordingly, the computer 4 receives the information from the power system, performs a process relating to voltage stability described later, and displays various data relating to the voltage stability on the MMI device as a result.

FIG. 1 is a flow chart showing the processing contents concerning the voltage stability of the electronic computer. In FIG. 1, in a system state determination process S10, a most probable state value of a power system is obtained by a weighted least squares estimation method using measurement information including an error of the power system input from the information transmission apparatus. In the stability limit calculation processing S20, the above-described system state determination processing S10
Using the result of (1) as an initial value, a voltage stability limit is obtained. In the stability monitoring process S30, the current state of the stability of the power system is determined using the results of the processes S10 and S20. In the effect amount calculation processing S40, the voltage regulator uses the result of the processing S10 to obtain an effect amount that increases the voltage stability. In the adjustment amount calculation process S50, when the system voltage is unstable using the results of the processes S30 and S40, an adjustment amount of the voltage adjustment device necessary for stabilization is obtained, and in the output process S60, the result of each of the processes is obtained. Are displayed on 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 S10, the most probable system state value, 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: vector of measured value x: true value of state variable, that is, vector of node voltage and its phase angle h (x): x vector function ε obtaining: this vector measurement error when, the square sum of the residuals between measured and the estimated value, J = (z-h ( x)) t w (z-h (x)) ...... ( 2) Here, w: matrix of error weights of the measured values z−h (x): vector of residuals of measured values t: indicating transposition of vector The estimated value x of the state variable x that minimizes is calculated. 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. The position shown in FIG. 3 is determined from the result.

When calculating the power flow based on each measured value, first, the demand is slightly increased based on the current power flow value, and the ratio of the active power and the reactive power to the increase is calculated. Then, the system voltage with respect to the increase in the demand is obtained and plotted. In this manner,... Are sequentially determined to be a PV curve.

Here, FIG. 3 is a diagram in which the demand (MW) is plotted on the horizontal axis, and how the system voltage (KV) plotted on the vertical axis changes with the change in the demand.

The stability limit calculation process S20 has a plurality of solutions because the power flow calculation of the power system is a non-linear quadratic simultaneous equation. When the power flow calculation is performed for a given demand, as shown in FIG. A solution with a higher voltage and a solution with a lower voltage are obtained, and the intermediate point is defined as the voltage stability limit. That is, when the voltage is higher than the stability limit shown in FIG. 3, the voltage is in a stable state, and when the voltage is lower, the voltage is in an unstable state. First, the third state obtained by the system state determination processing S10
The state when the demand is increased by a certain amount is obtained from the current system state at the point in the figure. That is, the economic load distribution calculation is performed for the increased demand, the output of the generator is determined,
The active power and the reactive power of the load are determined based on the distribution coefficient for the total demand of the load and the power factor of the load. In this way,
Calculate until the demand is increased and the power flow solution cannot be obtained. The result is: next,,
Find the lower solution corresponding to, In general, when a solution of a quadratic or higher-order equation is determined by a successive correction method such as the Newton-Raphson method, which solution is obtained among a plurality of solutions is determined by an initial value of the solution, that is, an initial approximation value. A lower solution is obtained by reducing the initial values of the node voltage and its phase angle. The solution is used as an initial value for obtaining a solution, the solution is used as an initial value for obtaining a solution, and the solution is used as an initial value for obtaining a solution. An intermediate point between the intermediate point and the intermediate point between and is defined as a stability limit.

FIG. 4 is a diagram showing the levels of voltage stability. The stability monitoring process S30 is performed based on the voltage stability limit curve as shown in FIG. 4 obtained by the stability limit calculation process S20. Evaluate the following items regarding the voltage stability of the power system.

(1) Voltage stability _{IVS = V t -VSL (P t} ) V t: current voltage VSL (P): stability limit voltage P when the total power demand P: total demand P _t: current total demand ( 2) Determination of stability level The stability level of the system voltage of the current power system is determined. That is, it is determined which of the stable state, stability attention, stability warning, and unstable areas shown in FIG. 4 is included.

The effect amount calculation processing S40 obtains an amount of an effect that a device for adjusting a system voltage such as a condenser, a reactor, a tap of a transformer, a generator voltage or the like increases 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 more stable the system voltage is to the stability limit voltage. Therefore, how much the system voltage rises when the voltage adjusting device is adjusted by a unit amount, that is, the voltage sensitivity coefficient ΔV / ΔC _q is an effect amount for improving the stability. The voltage sensitivity coefficient is obtained by the following method. Before and after the adjustment, the sum F of the active power and the sum G of the reactive power flowing into and out of the node are always zero. Before the adjustment: F (V, _Cq , θ) = 0 (3) G (V, C _q , θ) = 0 (4) Here, F and G are vectors.

Adjusted: F (V + ΔV, C q + ΔC q, θ + Δθ) = 0 becomes ...... and (5) G (V + ΔV , C q + ΔC q, θ + Δθ) = 0 ...... (6). Here, V: node voltage θ: phase angle of node voltage C _q : a reactive power-related adjustment variable such as a capacitor (SC) and an actuator (ShR).

Next (5), Expanding retailer to (6), F (V + ΔV, C q + ΔC q, θ + Δθ) = F (V, C q, θ) + F V · ΔV + F cq · ΔC q + F θ · Δθ ...... (7) the _{G (V + ΔV, C q} + ΔC q, θ + Δθ) = G (V, C q, θ) + G v · ΔV + G cq · ΔC q + G θ · Δθ ...... (8). _{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 ...... (9) G v · ΔV + G cq · ΔC q + G θ · Δθ = 0 ...... (10), on or releasing the SC or ShR In the case of, F _cq =
Since 0 (9), (10) erases the Δθ from equation, ΔV / ΔC _q = - and ^{_{(G v -F θ -1 F v}} · G θ) -1 · G cq ...... (11) Become. Here, G is calculated using V and θ obtained as a result of the process S10.
_v, F _θ, perform the F _V, the calculation of G _cq. An example of the effect amount of the adjusting device obtained in this way for improving the stability of the system voltage is shown in FIG.
Shown in the figure.

When the system voltage is determined to be unstable by the process S30, that is, when the current system voltage is lower than the voltage stability limit curve, the adjustment amount calculation process S50 calculates the adjustment amount R necessary for restoring to a stable state. Ask. The amount of voltage increase VUP required to make the system voltage higher than the voltage stability limit voltage curve shown in FIG. 4 is determined as follows from the voltage stability IVS obtained by the stability monitoring process S30.

VUP = −IVS + α (12) α: safety factor Next, when stabilizing by turning on the capacitor (SC), R = VUP using ΔV / ΔCq of the equation (11), which is the result of processing S40.調整 (ΔV / ΔC _q ) The amount of adjustment R is obtained by (13).

The output process S60 outputs the results of the processes S10, S20, S30, S40, S50 to an MMI device such as a CRT display device. FIG. 6 shows an example in which the current value of the system voltage determined by the process S10 and the time-series change of the status of the stability limit voltage VSL determined by the process S20 are displayed on a CRT display device.

As described above, according to the present embodiment, it is possible to appropriately provide the operator with various data relating to the voltage stability regarding the system voltage of the power system.

FIG. 7 is a flowchart showing the processing content of another embodiment according to the present invention.

In this embodiment, the adjustment amount calculation processing S50 is omitted. That is, the operator looks at the effect size,
This is because a necessary adjustment amount can be determined. Others are the same as FIG.

FIG. 8 is a flowchart showing the processing content of still another embodiment according to the present invention.

In this embodiment, the system state determination means is omitted in consideration of the case where the error of the measurement data of the state of the power system is sufficiently small. That is, when the error in the measurement data is sufficiently small, the power flow calculation can be performed directly using the measurement data to find the voltage stability limit, so that the system state determination processing S10 can be omitted as shown in FIG.

FIG. 9 is a flowchart showing the processing content of still another embodiment according to the present invention.

In the present invention, the system state determination processing S10 and the adjustment amount determination processing S50 are omitted at the same time along with FIGS. 7 and 8.

[Effects of the Invention] As described above, according to the present invention, the voltage stability limit is determined for the system voltage of the power system, and based on this, the effect amount for improving the stability and the adjustment amount required for the stabilization are determined. Since the display is performed, the operator can monitor and operate the power system with higher quality, and thus can more stably supply the power.

[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, FIG. 4 is a diagram showing a voltage stability level, FIG. 5 is a diagram showing an example of an effect amount of the adjusting device, FIG.
FIG. 7 is a diagram showing an example of display on the MMI, FIG. 7 is a flowchart showing the processing content of another embodiment according to the present invention, FIG. 8 is a flowchart for confining the processing content of still another embodiment, and FIG. 6 is a flowchart showing the processing contents of the embodiment. S10: System status determination processing S20: Stability limit calculation processing S30: Stability monitoring processing S40: Effect amount calculation processing S50: Adjustment amount calculation processing S60: Output processing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Kato 1-3-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company, Inc. (72) Inventor Ken Ken Fujiki 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba-fu Naka Factory (72) Inventor Masahiro Sato 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Nakashi Plant of Toshiba Fuso Co., Ltd. (72) Inventor Yukio Kishida 1-1-1 Shibaura, Minato-ku, Tokyo Inside Toshiba head office (56) References JP-A-62-110838 (JP, A) JP-A-61-121720 (JP, A) JP-A-55-159270 (JP, A)

Claims (1)

(57) [Claims] 1. A power system monitoring 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 control system, a system state determining means for obtaining a state of the monitored power system from system information transmitted via the information transmission device, and a system demand P and a system voltage V based on the obtained system state. And a stability limit calculating means for determining a voltage stability limit based on a line connecting an intermediate point between a higher solution and a lower solution of the PV curve. A stability monitoring means for determining the level of the stability and determining the stability of the system voltage according to how far the vehicle is from the stability limit in the stability region, and a device for adjusting the system voltage in a unit amount. Only tone When the system voltage is in an unstable state based on the effect amount, it is necessary to stabilize the system voltage based on the effect amount. An electric power system monitoring and control system, comprising: an adjustment amount calculating unit that obtains an adjustment amount; and an output unit that outputs various data as the respective calculation results.