JP2965253B2 - 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, since there was no way to know where the voltage stability limit was, when the power system 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 stably maintained 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. System state determination means (S10) for determining the current state of the system, and the state of the future power system several minutes or several hours ahead of the current system state obtained by the system state determination means and past results or total demand forecast results (S20) for predicting the future power system state and the future power system state determined by the future system state prediction means. A stability limit calculating means (S30) for determining a limit; and a distance from the stability limit in the stability region with respect to the determined voltage stability limit of the future predicted system state. Stability monitoring means (S40) for judging the degree of system voltage stability, effect amount calculating means (S50) for increasing the system voltage regulation by a device for adjusting the system voltage, and when the system voltage is unstable An adjustment amount calculating means (S60) for obtaining an adjustment amount for increasing the stability when it is determined that the level is necessary or close to unstable for stabilizing the data; And output means (S70).

(Operation) First, the system state determination means determines the current state of the monitored power system using the measurement value including the error of the power system information input from the information transmission device, and the future system prediction means determines the system state. A future state that is several minutes or several hours ahead of the current system state obtained by the determination means and past results or total demand prediction results is determined. Next, the voltage stability limit calculating means obtains a voltage stability limit based on the PV curve of the demand power P and the bus voltage V with respect to the future predicted system state determined by the future system state predicting means. Then, the stability monitoring means determines the degree of stability of the system voltage based on how far from the stability limit in the stable region with respect to the future predicted system state at the determined voltage stability limit. .

In addition, the effect amount calculation means obtains an effect amount for the device for adjusting the system voltage to increase the voltage stability, and the adjustment amount calculation means is required to stabilize the system voltage when the system voltage is unstable. If it is determined that the level is near or unstable, an adjustment amount is obtained to increase the stability, and 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 electronic computer 4. It consists of a machine interface device (MMI).

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 electric power system, and processes the prediction data of the future electric power system state several minutes or several hours ahead based on the current information with respect to the voltage stability described later. And displays the resulting data on the various voltage stability on the MMI device.

FIG. 1 is a flow chart showing the processing contents concerning the voltage stability of the electronic computer. In FIG. 1, in the system state determination processing (S10), the most probable current system state value of the power system, that is, as shown in FIG. The corresponding state is determined by a weighted least squares estimation method. The future power system state prediction process (S20) is based on the present power system state and the future power system state several minutes ahead or several hours ahead corresponding to FIG. 8 or FIG. Predict. Next, a stability limit calculation process (S30) obtains a voltage stability limit based on a PV curve of the demand power P and the bus voltage V for the future predicted system state determined by the future system state prediction process.

Then, the stability monitoring process (S40) determines the degree of stability of the system voltage based on how far from the stability limit in the stability region the future predicted system state will be at the determined voltage stability limit. Is determined. In the effect amount calculation process (S50), the device for adjusting the system voltage obtains the effect amount for increasing the voltage stability. Then, the adjustment amount calculation processing (S60) calculates an adjustment amount to increase the stability when the system voltage is unstable or is determined to be necessary to stabilize the system voltage or when the level is close to unstable. In the process (S70), various data as a result of each process 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, the system status determination processing (S1
In (0), 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 measurement 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.

At this time, 2 Nowari residual of measured values 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. The position shown in FIG. 8 is determined from the result.

The future system state prediction process (S20) is based on the current system state and the total demand forecast data at the future time, generator output, predicted distribution values such as interchange power, power system change schedule,
The power system model and the power system state data at the future time are obtained by making corrections using the AVR reference value pattern, etc.
Since the response of the VQC device etc. is not considered, the power flow is calculated using the obtained data and the prediction data of the individual control device of the previous prediction, and the power system state prediction data without the individual control device response is obtained. A response prediction calculation is performed by reflecting the response state of the individual control device in the data obtained here, and the response prediction data of the individual control device is obtained.Finally, the power system status data at the future time obtained above and the individual control device By performing the tidal flow calculation using the response prediction data,
Final power system state data at a future point in time simulating the response of the individual control device corresponding to FIG. 8 or FIG. 3 is obtained.

The stability limit calculation process (S30) has multiple solutions because the power flow calculation of the power system is a non-linear system of quadratic equations,
When a power flow is calculated for a given demand, a solution with a higher voltage and a solution with a lower voltage are obtained as shown in FIG.
The intermediate point is 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 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 prediction processing (S20). That is, the economic load distribution calculation is performed on 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 importance of the load. It is a higher solution of the result of performing the tidal current calculation under the condition. In this way, the calculation is sequentially performed until the demand is increased and the solution of the power flow calculation cannot be obtained. The result is, next,
Find a lower solution, ,, corresponding to,,,.

In general, when a solution of a quadratic or higher-order equation is obtained by a sequential 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 approximate value. Is obtained by reducing the initial values of the node voltage and its phase angle. The points of,... Are sequentially determined as the initial value for obtaining the solution of, the initial value for obtaining the solution of, and the initial value for obtaining the solution of. An intermediate point between the intermediate point and the intermediate point between and is defined as the stability limit.

When repeating the power flow calculation for plotting the PV curve, fix the input states of the phase adjustment capacitors and reactors, the tap positions of the transformers, the synchronous phase adjuster voltage, that is, the equipment state related to the adjustment of the reactive power and voltage. It is common to calculate the tidal current by using 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. Since different and different PV curves are obtained, in order to evaluate the voltage stability under a certain condition, the input amount of a capacitor and a reactor for phase adjustment, a tap position of a transformer, a voltage of a synchronous phase shifter and a generator voltage. It is a typical method to calculate the PV curve while fixing.

Although not directly related to the present invention, for the current system state, the input amounts of the phase-adjusting capacitors and reactors determined by the system state determination process (S10), the tap positions of the transformer, the voltage of the synchronous phase adjuster And generating the PV curve using the generator voltage. For the predicted future system state, the input of the phase-adjusting capacitors and reactors, the tap position of the transformer, the synchronous phase adjuster voltage, and the generator voltage determined by the future system state prediction process (S20) are used.
Create a V-curve. In the current system state and the future system state, if the value of the total demand is different, for example, if the demand increases, the system voltage will decrease. Therefore, the operation of individual control devices, such as individual VQC, the input amount of phase-adjusting capacitors and reactors, transformers The tap position, synchronous phase shifter voltage and generator voltage are usually adjusted.

According to the present invention, the input amounts of the phase-adjusting capacitors and reactors, the tap positions of the transformers, the synchronous phase shifter voltage, and the generator voltage are predicted with respect to the future system state by predicting the response of individual devices. In this way, in the future predicted system state, if the current system state and the total demand value determined by the system state determination process (S10) are different, for example, if the demand increases from the current state, the input amount of the phase-adjusting capacitors and reactors , Transformer tap position, synchronous phaser voltage and generator voltage are different, resulting in different PV curves as shown in FIG. That is, the current system PV curve becomes a curve of, and the curve of the future prediction system PV becomes a curve of. The current state on the current system PV curve is a point determined by the system state determination processing (S10), and the future predicted system P
The predicted current state at a future point on the -V curve is a point determined by the future system prediction process (S20).

FIG. 4 is a diagram showing the levels of voltage stability. The stability monitoring process (S40) uses the voltage stability limit curve as shown in FIG. 4 obtained by the stability limit calculation process (S30). On the other hand, the following items will be evaluated on the voltage stability of the system status in the future.

(1) Voltage stability _{IVS = V t -VSL (P t} ) V t: future system voltage, i.e., voltage corresponding to Figure 8.

 VSL (P): Stability limit voltage at the time of total power demand P.

P: Gross demand _Pt : Future gross demand, that is, gross power demand corresponding to the one shown in FIG.

(2) Determination of stability level The stability level of the system voltage of the power system in the future system state is determined using the voltage stability IVS. That is, the state of the voltage stability of the future system, that is, whether the magnitude of the IVS is included in each of the stable state, stability attention, stability alert, and unstable areas shown in FIG. judge.

In the effect amount calculation process (S50), a device for adjusting a system voltage such as a condenser, a reactor, a tap of a transformer, a generator voltage or the like obtains an amount of an effect of increasing 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, the higher the stability limit voltage is. Therefore, how much the system voltage rises when the voltage regulator is adjusted by a unit amount, that is, the voltage sensitivity coefficient ΔV / ΔC _q is the effect amount of the improvement of 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 ...... (5) G (V = ΔV, C q + ΔC q, θ + Δθ) = 0 becomes ... (6). Where: 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).

Next (5), when the (6) to Taylor expansion, F (V = ΔV, C q + ΔC q, θ + Δθ) = F (V, C q, θ) + F v · ΔV + F cq · ΔC q + F θ + Δθ ... ... the (7) 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), if the up or release of the SC or ShR is F _cq =
Since 0 (9), (10) erases the Δθ from equation, ΔV / ΔC _q = - a ^{_{(G v -F θ -1 · F}} v) -1 · G cq ...... (11). Here, G _V , F _θ , F _v , and G _cq are calculated using V and θ obtained as a result of the process (S40). FIG. 5 shows an example of the effect amount obtained by the adjustment device thus improving the stability of the system voltage.

The adjustment amount calculation process (S60) is for restoring to a stable state when the system voltage is determined to be unstable by the process (S40), that is, when the current and future system voltages are lower than the voltage stability limit curve. Is obtained for the adjustment amount R required. The amount of voltage rise VUP required to make the system voltage higher than the voltage stability limit voltage curve shown in FIG.
Is obtained from the voltage stability IVS obtained as follows.

 VUP = −IVS + α (12) α: safety factor.

Next, when stabilization is performed by turning on the capacitor (SC), ΔV / ΔC _{q in} equation (11), which is the result of the processing (S50),
The adjustment amount R is obtained by using the following equation: R = VUP ÷ (ΔV / ΔC _q ) (13)

The output process (S70) includes the processes (S10), (S20), (S
30) The results of (S40), (S50) and (S60) are output to an MMI device such as a CRT display device. For example, an alarm message corresponding to the degree of stability of the system voltage determined in the process (S40) is displayed. FIG. 6 shows an example in which the future value of the system voltage determined by the process (S20) and the time-series change of the status of the stability limit voltage curve determined by the process (S30) 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 the present embodiment, the adjustment amount calculation processing S60 is omitted. That is, the operator can determine the necessary adjustment amount by looking at the effect amount. Others are the same as FIG.

[Effects of the Invention] As described above, according to the present invention, the current and future voltage stability limits are determined with respect to the system voltage of the power system, and based on this, the effect amount for improving the stability and the stabilization are needed for stabilization. The adjustment amount is displayed, so that the operator can monitor and operate the power system with higher quality.
Therefore, more stable power supply is possible.

[Brief description of the drawings]

FIG. 1 is a flow chart showing the contents of processing relating to the 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. 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, and FIG. 8 shows the relationship between the PV curve at the present time and the PV curve at a future time. FIG. S10: System status determination process, S20: Future system status prediction process S30: Stability limit calculation process, S40: Stability monitoring process S50: Effect amount calculation process, S60: Adjustment amount calculation process S70 ... Output processing

Continued on the front page (72) Inventor Masahiko Amamiya 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Co., Inc. (72) Inventor Toshio Kato 1-3-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Inventor Kensei Kudo 1-1-1, Shibaura, Minato-ku, Tokyo Inside the Toshiba head office (72) Inventor Ken Kenki 1 Toshiba-cho, Fuchu-shi, Tokyo Tokyo Inside the Toshiba Fuchu factory (72) Inventor Masahiro Sato 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu factory (56) References JP-A-60-228287 (JP, A) JP-A-62-83628 (JP, A) JP-A 62-83628 2129 (JP, A)

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 control system, a system state determining unit that determines a current system state of a monitored power system from system information transmitted via an information transmission device, and a current system state and a past performance obtained by the system state determining unit. Alternatively, a future system state prediction means for predicting a state of a future power system several minutes or several hours ahead of the total demand prediction result, and a future power system state determined by the future system state prediction means, P and P- of bus voltage V
A stability limit calculating means for obtaining a voltage stability limit based on a V curve, and a future prediction system state based on how far from the stability limit in the stability region the voltage stability limit of the determined future prediction system state is bounded. A stability monitoring means for determining the degree of stability of the system voltage, an effect amount calculating means for an apparatus for adjusting the system voltage to calculate an effect amount for increasing the voltage stability, and the effect amount Adjustment amount calculation means for obtaining an adjustment amount necessary for stabilizing the system voltage when the system voltage is unstable, or when it is determined that the level is close to unstable when the system voltage is unstable. And an output means for outputting various data as the calculation result.