JPH03215124A - Calculating system of voltage margin and effective power margin - Google Patents

Abstract

PURPOSE:To operate margins of voltage and effective power under present condition of a system by a method wherein the condition of the power system is determined from a measured value containing an error while a P-V curve is operated from the results. CONSTITUTION:A system condition determining means S10 determines a power system condition at first by employing a measured value containing the error of information on the power system 1, which is inputted from an information transmitting device 2-1. A P-V curve operating means S20 changes the total amount of demand imaginarily by employing this result to operate the higher resolution and the lower resolution of a voltage with respect to different total amount of demand. On the other hand, the P-V curve operating means S20 operates the P-V curve by approximating the resolution according to some function. A voltage margin and effective power margin operating means S30 operates and outputs respective margins based on the results. According to this method, the voltage margin and the effective power margin under current system condition can be operated whereby stable power can be supplied even upon sudden change of a load.

Description

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

(Prior art) When monitoring grid voltage with a conventional power grid monitoring and control system, the current state of grid voltage is displayed and whether or not it is within the range of the upper and lower limits of the voltage target value. The system monitors the area and issues an alarm when it is out of range.

(Problem to be solved by the invention) The magnitude of the current voltage in the power system can be understood by measuring it, but it is necessary to calculate the current voltage margin value and active power margin value. Therefore, there was no way to maintain appropriate grid voltage when a unique power grid condition that had not been experienced in the past occurred, such as when an unexpectedly heavy load or a sudden change in load occurred. There was a risk of uncertainty.

The present invention was made in view of the above-mentioned concerns, and an object of the present invention is to provide a voltage margin value and active power margin value calculation method that makes it possible to determine the voltage margin value and active power margin value in the current system state. shall be.

[Structure of the Invention] (Means for Solving the Problems) The structure for achieving the above object will be explained with reference to FIG. In a system that calculates the value of grid voltage by calculating the power flow based on the input information, the system status determines the power grid status based on the measured values including errors input from the information transmission device. Determination means (S10
), the total demand is virtually changed using the results of the system state determination means, and solutions for increasing and decreasing voltage for different total demand values are calculated, and this solution is approximated by a certain function to calculate p -P-■ curve calculation means for calculating the v curve (S2
0) and the voltage margin which calculates the margin values of voltage and active power using the results of the P-■ curve calculating means. It consists of active power margin output means (330).

(Operation) First, the power system state is determined using the measured value including errors in the power system information inputted from the system state determination means or the information transmission device.

The p-v curve calculation means uses the results of the system state determination means to calculate a plurality of voltage increase solutions and voltage decrease solutions by virtually changing the total demand value. Next, a pv curve is calculated by approximating the obtained solution points with a curve of a certain function. The voltage margin and active power margin output means calculates and outputs each margin value using the P-■ curve obtained by the P-■ curve calculation means.

That is, active power margin 1 P - P max O Voltage margin 1 system voltage 1 eye field voltage limit voltage 1 (v, 1 + v, 1) /2 However, Po = total demand of the current system P: total demand limit value laX ■11 : Current voltage higher solution ■, 1: Current voltage lower solution This allows the voltage margin value and the active power margin value to be output.

(Example) An example will be described below with reference to the drawings. For convenience of explanation, the explanation will start from FIG. 2, which is a diagram showing an example of the configuration of a system to which the voltage margin and active power margin calculation method of the present invention is applied.

The system in FIG. 2 includes an information transmission device 2-1 that measures the state of the power system 1 and transmits the measured value, an information transmission device 2-1 that receives the information via a transmission path 3, and Electronic calculation Ii! that calculates the voltage margin and active power margin based on the information of It consists of an I4 and a man-machine interface device (8M1>5) that displays the processing results of the electronic calculation fi4.

Measurement information from the power system includes, for example, generator voltage and output, load active and reactive power, active power flow, and reactive power flow. Bus voltage. There are open/close states of disconnectors and disconnectors.

Therefore, the electronic calculation tll14 inputs each of the above-mentioned current measurement information from the power system, and based on this current information,
Calculate the voltage margin value and active power margin value, and the resulting voltage margin value. Data regarding the active power margin value is displayed on the old H device 5.

FIG. 1 is a flowchart showing the process of outputting the system voltage margin value and active power margin value.

In FIG. 1, the system state determination means S10 uses a weighted least squares estimation method to determine the most probable system state values, that is, node voltages and voltage phase angles, from measured values including errors transmitted from the power system. , that is, determined by state estimation calculation.

Generally, measured values that include errors can be expressed as follows.

z = h (X) + ε...
...(1) However, Z: vector of measured values Vector of determination error In this case, the sum of squares of the residual error between the measured value and its estimated value, J=
(z−h(x) ) tw (z−h(x) ) −(
2) However, W: matrix of error weights of each measurement value Z-hfX)
:Vector of the residual error of the measured value t: Find the estimated value X of the state variable X that indicates the transposition of the hector. Next, the estimated value of the power flow is determined from the determined X.

Through the above procedure, the influence of errors included in the measured values is removed, and a more reliable state of the power system can be obtained.

Figure 3 is a diagram showing the relationship between demand and system voltage, with the vertical axis showing the voltage value, the horizontal axis showing the power demand value. From the above calculation results, the positions of ■ and ■ in FIG. 3 are determined. These ■ and ■ are solutions for increasing and decreasing the current grid voltage, respectively.

In the p-v curve calculation means S20, the system state determination means S1
From the current system status at the point ■ in FIG. That is, the output of the generator is determined by performing economic load distribution calculations for the increased demand, and the active power and 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.

A higher solution as a result of tidal flow calculations under those conditions is shown below. In this way, the demand is increased one after another until a solution to the power flow calculation cannot be obtained. The results are ■, ■,
■、■. Next, find lower solutions, ■, ■, ■, ■, corresponding to ■, ■, ■, ■. Generally, when finding solutions to equations of quadratic or higher order using an iterative correction method such as the Newton-Raphson method, which solution will be obtained among multiple solutions is determined by the initial value of the solution, that is, the first approximation value.
A lower solution (2) is obtained by reducing the initial values of the node voltage and its phase angle. The solution of ■ is used as the initial value for calculating the solution of ■, the solution of ■ is used as the initial value for calculating the solution of ■, and the solution of ■ is used as the initial value for calculating the solution of ■. Find the points of ■ and ■.

■,■,■,■,■,■,(Φ,
When (2) is approximated by a spline function curve, a P-(2) curve as shown in FIG. 3 is obtained.

Active power margin. In the voltage margin output means, this p-
Calculate the active power margin value and voltage margin value using the v curve. In other words, the P-axis upper value P na of the tip ■ of the P-■ curve
Let the difference between x and PO be the active power margin value. Further, the intermediate value [phase] between the current high voltage solution value ■ and the low voltage solution value ■ is taken as the limit voltage value, and the difference between the voltage increase solution and the limit voltage value is taken as the voltage margin value.

That is, active power margin 1 P −P Pax O Voltage margin 1 system voltage 1 limit voltage limit electric field 1<VH1+V11) ,/2 However, Po
: Current system total demand P : Total demand limit value max ■H1: Current voltage high solution v11: Current voltage low solution - Therefore, when the system is currently in the low voltage solution, ■The margin value becomes a negative value.

In this way, the voltage margin value and active power margin value in the current system can be determined.

[Effects of the Invention] As explained above, according to the present invention, regarding the grid voltage of the power system, the current system voltage margin value and active power value are determined and presented to the operator, which makes it easier for the operator. It becomes possible to monitor and operate a high-quality power system, and therefore, a more stable supply of power becomes possible.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing a method for calculating the voltage margin and active power margin according to the present invention, Fig. 2 is a configuration example diagram of a power system monitoring and control system implementing the present invention, and Fig. 3 is a diagram showing demand and grid system. It is a relationship diagram with voltage. 310...System state determination means S20...PV curve calculation means S30...Active power margin. Voltage margin output means Fig. 1

Claims (1)

[Claims] In a system that inputs grid information from the power grid to a computer via an information transmission device and calculates the power flow based on this information to determine the value of grid voltage, the error input from the information transmission device is A system state determination means for determining a power system state based on the measured values, and a solution for increasing voltage for different total demand values by virtually changing the total demand amount using the results of the system state determination means. A PV curve calculation means that calculates a lower solution and approximates this solution with a certain function to calculate a PV curve, and a margin value of voltage and active power using the results of the PV curve calculation means. A method for calculating a voltage margin value and an active power margin value, comprising a voltage margin and an active power margin output means for calculating the voltage margin and active power margin.