JP4203030B2 - Power system step-out separation method and apparatus - Google Patents

Description

  The present invention relates to a power system that performs system separation in order to prevent a step-out phenomenon from spreading to other generators when a step-out phenomenon occurs in some generators due to a disturbance such as a fault in a transmission line. The present invention relates to a step-out separation method and apparatus.

  Examples of systems that prevent the expansion of the step-out phenomenon by system separation include a step-out separation relay and a system stabilization device.

  The former step-out separation relay is installed for each transmission line in the power system, and monitors whether the out-of-step locus has entered the monitoring target transmission line. The transmission line is cut off to prevent the step-out phenomenon from spreading.

  Here, when the out-of-step locus is in a simple two-machine system in which two generators are connected via a transmission line, the step-out progresses and the phase angle difference between the generators increases. Then, it means 180 degrees, and the voltage becomes zero at the midpoint of the transmission line.

  On the other hand, the latter system stabilizing device includes the following system (for example, Non-Patent Document 1).

This system targets one specific step-out mode that occurs in the target system, and the target system is a model consisting of two generators (two-machine model, separated system including the out-of-step generator and its effect). When the bus voltage phase of each representative electric station is measured momentarily and the phase angle difference between the two is calculated and the phase angle difference exceeds a preset threshold Then, it is determined that a step-out has occurred, and a fixed system separation is performed at a preset position to prevent the step-out phenomenon from spreading.
IEEJ Power Technology Study Group, “Development and Practical Use of Core System Stabilization Relay System”, PE-89-51, P161-170, (1989)

  In the step-out separation relay described above, when multiple out-of-step modes occur in the target system, or when the out-of-step phenomenon is complicated and there are a wide variety of transmission lines containing out-of-step locus, It is necessary to install a step-out separation relay. Furthermore, if the target system is a loop system, depending on the step-out mode, the step-out locus enters a large number of transmission lines, the step-out separation relays operate one after another, and as a result, the power system is subdivided and the operation cannot be continued. It can be a situation. In addition, because it detects that the out-of-step locus has entered, that is, the transmission line is cut off when the phase angle difference between both ends of the transmission line is 180 degrees or more, the step-out has progressed considerably when viewed from the entire power system. If possible, the stabilization effect will be higher if the system is separated earlier than this.

  In the case of the system stabilization device, since it is a step-out determination in a two-machine system model (step-out system and sound system) for a specific one step-out mode (step-out phenomenon), It cannot be applied to the power system where the step-out mode occurs.

  In order to solve the above-mentioned problems, the present invention obtains a phase angle difference between each point using phase angles of a plurality of points in a wide area of the power system, and extracts a step-out generator group from the phase angle difference. By estimating the generated out-of-step mode and performing system separation suitable for the generated out-of-step mode based on the estimation result, the system configuration and the number of out-of-step modes are not limited, and the system It is an object of the present invention to provide a power system step-out separation method and apparatus capable of performing separation.

  In order to achieve the above object, the present invention performs step-out separation of a power system by the following method and apparatus.

In the invention corresponding to claim 1, when some of the generators step out due to a disturbance such as a transmission line failure in a power system in which a plurality of synchronized generators are interconnected by a transmission line, this step-out phenomenon occurs. In the power system step-out separation method that separates the system so that it does not spread to other generators, the bus voltage phase angle of a predetermined electric power station in the power system is measured every moment, and the phase of the wide area of the power system is measured. to obtain information, those to calculate the phase angle difference between each substation from the phase information, and a first preset threshold and the phase angle difference compared respectively, said first threshold value If there is a phase angle difference exceeding the phase difference, it is determined that a step-out has occurred, and then, among the phase angle differences, phase angle differences other than those that have been determined to have caused the step-out by exceeding the first threshold value And a second threshold value set smaller than the first threshold value, respectively, Phase angle is determined that the step-out occurs if there is a phase angle difference, in excess of the first phase angle difference and said second threshold exceeds a threshold that exceeds the second threshold The out-of-step generator group is extracted from the difference, and the out-of-step mode is estimated from the combination of the extracted out-of-step generator group, and optimum system separation is performed.

In the invention corresponding to claim 2, when some of the generators step out due to a disturbance such as a power transmission line failure in a power system in which a plurality of generators synchronized with each other are connected by the transmission line, this step-out phenomenon occurs. In a power system step-out separation device that separates the system so that it does not spread to other generators, the bus voltage phase angle of a predetermined electric power station in the power system is measured momentarily, and the phase of the wide area of the power system is measured. Phase information obtaining means for obtaining information, phase angle difference calculating means for calculating a phase angle difference between each electric station obtained by the phase information obtaining means, and each phase angle calculated by the phase angle difference calculating means by comparing the first threshold value set in advance and the difference respectively, said determining that step-out occurs if the first is the phase angle difference exceeds the threshold, then each phase angle difference Of which the first threshold is exceeded and it is determined that step-out has occurred. A phase angle difference other than the above is compared with a second threshold value set smaller than the first threshold value, and if there is a phase angle difference exceeding the second threshold value, the step-out is stepped out. It is determined that the out-of-step generator group is extracted, and the out-of-step generator group is extracted from the phase angle difference exceeding the first threshold value and the phase angle difference exceeding the second threshold value. A step-out mode determination unit that estimates a step-out mode from the combination and a system separation unit that performs system separation based on the step-out mode estimated by the step-out mode determination unit.

The power system step-out separation method and apparatus according to the present invention can estimate the step-out mode when the first step-out is detected, so there is no need for a timer to confirm the presence or absence of the generator group that is stepped out later. Therefore, system separation can be performed at an early stage, and the stabilization effect can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory diagram of the configuration of the power system step-out separation apparatus according to the first embodiment of the present invention.

  First, a schematic configuration of an electric power system to which the present invention is applied will be described. Reference numeral 103 denotes a plurality of power plants dispersed in a wide range. Electric power output from the power generator 101 of each power plant is mutually transmitted by a transmission line 104. A power system 100 is formed in which power is transmitted to a plurality of electrical stations (substations or switching stations) 102 connected to each other and power is supplied from each electrical station 102 to a load 105.

  In the present embodiment, when the step-out separation device 1 is installed at such a central monitoring station that monitors the entire power system 100, and a step-out phenomenon occurs in any of the generators 101 due to an accident in the transmission line 104, The transmission line connected to the generator is separated from other healthy transmission lines.

  The step-out separation apparatus 1 includes a system information acquisition unit 2, a phase angle difference calculation unit 3, a step-out mode determination unit 4, a system separation point selection unit 5, and a control output unit 6.

  The system information acquisition unit 2 captures and measures the bus voltage phase detected at a predetermined electric station in the power system and transmitted via the communication system as shown in the drawing.

  The phase angle calculation unit 3 calculates the phase angle difference between the electrical stations using the bus voltage phase measured by the system information acquisition unit 2.

  The step-out mode determination unit 4 compares each phase angle difference calculated by the phase angle difference calculation unit 3 with a preset threshold value, and determines that step-out has occurred when the threshold value is exceeded. After a certain period of time, the voltage phase measurement by the system information acquisition unit 2, the calculation of the phase angle difference by the phase angle difference calculation unit 3, and the comparison process with the above threshold value are repeated, and then the phase exceeding the threshold value The step-out generator group is extracted from the angle difference, and the step-out mode is estimated from the combination.

  The system separation point selection unit 5 determines an optimum system separation point according to the step-out mode.

  The control output unit 6 outputs a system separation command via a communication system to a system separation device installed at a planned location of the power system based on the selection result of the system separation point.

  On the other hand, before operating the step-out separation apparatus 1 of the present embodiment, the preset system 10 is obtained from the stability characteristic grasping means 11, the phase angle detection point selection means 12, and the step-out mode / system separation point selection means 13. The set value 14 is given to the step-out mode determination unit 4 and the system separation point selection unit 5.

  The stability characteristic grasping means 11 grasps the stability characteristic of the target system, arranges the step-out mode generated in the target system, and determines the step-out mode targeted by the present apparatus.

  For example, when the power system as shown in FIG. 2 is targeted, first, in order to grasp the transient stability characteristics of the target system, the transient stability simulation is repeatedly executed using the failure point / failure parameters as parameters. Check the step-out pattern that occurs in the grid.

FIG. 3 shows an example of the result of arranging the step-out patterns. In the electric power system of FIG. 2, there are five steps-out patterns (step-out modes). generator group generator groups and within the area described as the generator group G _B in the area boxed described with machine group G _a is the sense of loss of synchronism together.

  Next, the phase angle detection point setting means 12 selects a phase angle detection point so that all target step-out modes can be detected. Specifically, one of the electric power generation buses in each out-of-step generator group area is selected as a phase detection point, and the generator group area that is not out of step (healthy system affected by out-of-step ) To select the phase angle detection point.

For example, based on the step-out pattern in Fig. 3, the generator group G _A as shown in FIG. 2, the generator group G _B, ..., if the step-out generator group is classified as such a generator group G _E, the a substation of the generator group G _a is in the area, the generator group G _B is selected the B power plant in the area as the phase angle detection point. The phase angle detection points in the generator area that does not step out may be any electrical station in the healthy system, but in FIG. 2, there are two F power stations and G substations.

  In step-out mode / system separation point selection 13, a system separation point corresponding to each step-out mode is selected under the following conditions.

      Necessary condition: System separation point where all generator groups to be stepped out are included on the separated system side.

Frequency condition: When there are multiple separation points that meet the above requirements, supply and demand imbalance
The separation point becomes smaller (the total tidal current of the transmission lines to be cut off is the smallest).

Voltage condition: If there are multiple separation points that meet the above requirements, system separation is performed.
Voltage rise exceeding the withstand voltage of transmission lines and equipment, or
A separation point where no voltage drop occurs.

  Note that the frequency condition and the voltage condition can be considered as necessary by the operation manager of the power system, and the system separation considering the frequency according to the frequency condition can be performed and the system separation considering the voltage according to the voltage condition can be performed. For example, FIG. 4 shows an example of the result of selection of the system separation point. Considering the above conditions, the step-out mode A selects L1, L2, and L3 transmission lines as the system separation point, and the step-out mode B includes L2, L3, and L3. L4 transmission line is selected.

  The above work is performed before the start of operation of the present apparatus, and the relationship between the step-out generator group and the step-out mode as shown in FIG. 3, the relationship between the step-out mode and the system separation point as shown in FIG. By setting this relationship in this device in advance (settling value 14), this device can handle a plurality of step-out modes and can select a system separation point suitable for the step-out mode. Yes.

  Details of the method for estimating the step-out mode and the method for selecting the system separation point suitable for the step-out mode will be described later.

  Next, the operation of each part constituting the out-of-step separating apparatus 1 for the power system will be described.

  First, the system information obtaining unit 2 measures the bus voltage phase 15 at the phase angle detection point (electrical station) determined as described above, and obtains it via the transmission system.

The phase angle calculation unit 3 obtains a phase angle difference between each electric station (phase angle detection point). For example, in the electric power system of FIG. 2, assuming that the phase angle of the A electric station (phase angle detection point A) is θ _A and the phase angle of the B electric station (phase angle detection point B) is θ _B , The phase angle difference between them is obtained as follows.

θ _AB = | θ _A −θ _B | (1)
As in the power system shown in FIG. 2, the phase angle detection points are 7 electrical stations (the phase angles of C, D, E, F, and G electrical stations are θ _C , θ _D , θ _E , θ _F , and θ _G ). ), The phase angle difference between the electrical stations is obtained in the same manner as in the equation (1), and a matrix as shown in FIG. 5 is created.

  The step-out mode determination unit 4 uses the phase angle difference calculated as described above to extract the step-out generator group and estimate the step-out mode.

  FIG. 6 is a diagram showing a processing flow of the step-out mode determination unit 4, and the operation of the step-out mode determination unit 4 will be described with reference to this figure.

In FIG. 6, in the step-out detection step (S41), each phase angle difference is compared with the step-out determination threshold value θ _α as shown in equation (2), and if it does not exceed θ _α , it is determined that the phase is stable. However, if it exceeds, it is determined that there is a step-out. Predetermined time Ts after it is determined that there out-the system information acquisition unit 2 of FIG. 1, the phase angle difference computing unit 3, repeats the processing of step-out mode determination unit 4, the phase angle difference exceeds the other theta _alpha Check if there is any.

If θ _AB <θ _α, it is judged as stable.If θ _AB ≧ θ _α, it is judged that there is a step-out.
(2)
For example, when the phase angle difference changes as shown in FIG. 7, FIG. 8 shows an example of the determination result when θ _α = 180 degrees and Ts = 100 ms. Θ _AG and θ _GA in seconds, and θ _BG and θ _GB exceed θ _α in 0.95 seconds. From this result, it is determined that the generator groups G _A and G _G (the generator group close to the G substation) and the generator groups G _B and G _G are out of step, and there is a step out (×) in the corresponding part of FIG. Is memorized. Other phase angle difference stability (○) are stored so does not exceed the theta _alpha.

  Next, in the step-out group determination step (S42), it is determined which of the detection points out of the detected points where the difference has been detected is out of phase with respect to the phase angle difference determined to have step-out. At the same time, the generated step-out mode is estimated. Specifically, with respect to the phase angle difference determined to have step-out, the change Δθ / Δt (= frequency Δf) in the unit time of the phase angle of both detection points where the difference was taken is obtained and compared to It is determined that the generator group at the detection point with the larger value is out of phase. As a result, the out-of-step generator group is known, and therefore the out-of-step mode is estimated using the combination of the out-of-step generator group and the relationship between the preset out-of-step generator group and the out-of-step mode.

For example, FIG. 9 shows an example of a step-out group determination result. As a result of step-out detection, θ _AG , θ _GA , θ _BG , and θ _GB are determined to have step-out, so both θ _AG and θ _GA are detected. Δθ _A / Δt, Δθ _G / Δt, θ _BG , θ _GB of both detection points Δθ _B / Δt, Δθ _G / Δt are obtained and compared, and θ _AG and θ _GA are detected at detection point A (A substation ) Is larger (Δθ _A / Δt = 30 degrees), and θ _BG and θ _GB are larger in the detection point B (B power plant) (Δθ _B / Δt = 25 degrees), so the detection point A is included. generator group G _B that contains the detection point B and the generator group G _a is judged to be out of step. Thus, since the generator group has lost synchronism is found, the relation of out-generator unit and the step-out mode shown in FIG. 3, step-out mode has occurred, the generator group G _A, is G _B It can be estimated that the step-out mode B is out of step.

  Next, the system separation point selection unit 5 selects a system separation point based on the step-out mode estimated as described above, and the relationship between the preset step-out mode and the system separation point suitable for the step-out mode.

For example, when the out-of-step mode B is estimated by step-out of the generator groups G _A and G _B , the L2, L3, and L4 transmission lines are connected to the system from the relationship between the step-out mode and the system separation point as shown in FIG. Determine the separation point.

  The control output unit 6 cuts off the transmission line selected by the system separation point selection unit 5.

  As described above, according to the first embodiment, a plurality of step-out modes can be targeted as compared with the conventional system stabilizing device, and the system separation according to the step-out mode can be performed. Moreover, since step-out detection and system separation can be performed earlier than in the step-out separation relay by using the wide-area phase information, the stabilization effect can be improved. Furthermore, by adding frequency conditions and voltage conditions to the system separation point selection conditions, system separation can be performed in consideration of frequency and voltage, so that the stable operation maintenance ability of the main system and the separated system after system separation can be improved. it can.

  Next, a second embodiment of the power system step-out separation apparatus according to the present invention will be described.

  In the present embodiment, when the step-out mode determination unit 4 in FIG. 1 described in the first embodiment determines the occurrence of step-out, the first threshold value set in advance is compared with each phase angle difference. If the first threshold value is exceeded, it is determined that step-out has occurred, and then the second threshold value set smaller than the first threshold value set in advance and each phase angle difference are determined. In comparison, the step-out generator group is extracted from the phase angle difference exceeding the first or second threshold.

  Note that the presetting system 10, the system information acquisition unit 2, the phase angle difference calculation unit 3, the system separation point selection unit 5, and the control output unit 6 are the same as those in the first embodiment, and thus description thereof is omitted here.

  FIG. 10 is a diagram showing a processing flow of the step-out mode determination unit 4 in the second embodiment of the present invention, and the operation of the step-out mode determination unit 4 will be described below with reference to this figure.

In FIG. 10, in the step-out detection step (S41), as in the first embodiment, each phase angle difference is compared with the first step-out determination threshold value θ _α1, and the threshold value θ _α1 is exceeded. If it has not, it determines with it being stable, and repeats the process in the system | strain information acquisition part 2, the phase angle difference calculating part 3, and the step-out mode determination part 4 of FIG.

If the first step-out determination threshold value _θα1 is exceeded, it is determined that there is step-out, and then the second step-out determination threshold value for the phase angle difference other than that determined as having step-out. compared to theta _{[alpha] 2,} if you exceed this threshold theta _{[alpha] 2} is also judged that there is out-of. In this case, set in the relationship of θ _α1 > θ _α2 , and by making both values close to each other, it progresses in the same manner as the generator group including the detection point that is determined to be out of step by exceeding θ _α1 You can also find other generator groups that are out of step.

For example, when the phase angle difference changes as shown in FIG. 7, FIGS. 11A and 11B are examples of determination results when θ _α1 = 180 degrees and θ _α2 = 150 degrees. In 0.90 seconds after the accident occurred, θ _AG and θ _GA exceeded θ _α1, and as a result, the generator groups G _A and G _G (the generator group close to the G substation) were determined to be out of step. The presence of step-out (x) is stored in the corresponding part of FIG. Since the other phase angle differences do not exceed θ _α1 , stability (◯) is stored.

Next, since there is a phase angle difference that exceeds θ _α2 , a phase angle difference that does not exceed θ _α1 , that is, a phase angle difference other than θ _AG and θ _GA (hatched portion in FIG. 11B) is θ. Compared with _α2 , θ _BG and θ _GB exceed θ _α2, and as a result, the generator groups G _B and G _G are also determined to be out of step, and there is a step out at the corresponding location in FIG. ) Is stored.

  In the out-of-step group determination (S42), the generator group at which detection point out of the two detection points obtained for the phase angle difference determined to be out of step is stepped out as in the first embodiment. And the occurrence of the step-out mode is estimated. Since this is the same as in the first embodiment, a description thereof will be omitted.

  According to the second embodiment, the step-out mode can be estimated at the time when the first step-out is detected, so that it is possible to confirm the presence or absence of the generator group that steps out with a delay as in the first embodiment. Since the timer TS is not necessary, system separation can be performed at an early stage, and the stabilization effect can be improved.

  Next, a third embodiment of the power system step-out separation apparatus according to the present invention will be described with reference to FIG. The same parts as those in the step-out separation apparatus for the power system of FIG.

  In the third embodiment, as shown in FIG. 12, the phase angle difference calculated every moment by the phase angle difference calculation unit 3 is stored, and the phase angle difference at the near future time is predicted using the stored phase angle difference. In addition, a phase angle difference prediction unit 7 that provides this to the step-out mode determination unit 4 is provided.

  Next, the operation of the phase angle difference prediction unit 7 will be described with reference to the processing flow shown in FIG.

  As shown in FIG. 13, the phase angle difference prediction unit 7 stores the phase angle differences calculated by the phase angle difference calculation unit 3 in the memory in the phase angle difference storing step (S71) for storing the current and past calculated values. In addition, a prediction formula for predicting a phase angle difference at a future time is generated by a prediction formula creation step (S72) using the phase angle difference stored in the memory, and a phase angle difference prediction step S73 is performed using this prediction formula. To predict the phase angle difference in the future.

  The step-out mode determination unit 4 uses the phase angle difference prediction value to determine the occurrence of step-out and extract the group of step-out generators as described above.

  Note that the prediction formula and the creation method thereof may be a method used in a conventional system stabilizing device. As an example, consider a quadratic prediction equation such as equation (3), and use the current and past phase angle difference data to determine the coefficient k by the least squares method to obtain the phase angle difference δ (t) ( For example, a phase angle difference of 250 ms ahead) is predicted.

An example of the prediction formula: δ (t) = k ₀ + k ₁ · t + k ₂ · t ² (3)
Here, k ₀ , k ₁ , and k ₂ are calculated by the least square method.

  As described above, according to the third embodiment, the step-out can be detected early by detecting the step-out using the predicted phase angle difference at the future time point, so that the system separation can be performed early as a result. Thus, the stabilization effect can be improved.

The block diagram which shows 1st Embodiment of the out-of-step separation apparatus of the electric power system by this invention. The figure which shows an example of the electric power system with which the step-out separation apparatus of the embodiment is applied, and a phase detection point. The figure which shows an example of the relationship between a step-out generator and a step-out mode in the electric power system shown in FIG. The figure which shows an example of the relationship between a step-out mode and a system | strain separation point in the embodiment. The figure which expressed the phase angle difference calculated | required by the phase angle difference calculating part in the matrix form in the same embodiment. The figure which shows the processing flow of the step-out mode determination part in the embodiment. The figure which shows the change of a phase angle difference in the same embodiment. The figure which shows an example of the determination result at the time of step-out in step-out detection in the same embodiment. The figure which shows an example of the determination result in a step-out group determination in the same embodiment. The block diagram which shows 2nd Embodiment of the out-of-step separation apparatus of the electric power system by this invention. The figure which shows an example of the determination result at the time of step-out in step-out detection in the same embodiment. The block diagram which shows 3rd Embodiment of the out-of-step separation apparatus of the electric power system by this invention. The figure which shows the processing flow of the phase angle estimation part in the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Step-out separation apparatus, 2 ... System information acquisition part, 3 ... Phase angle difference calculating part, 4 ... Step-out mode determination part, 5 ... System separation point selection part, 6 ... Control output part, 7 ... Phase angle difference prediction , 10 ... Pre-setting system, 11 ... Stability characteristic grasping means, 12 ... Phase angle detection point selecting means, 13 ... Step-out mode / system separation point selecting means, 14 ... Setting value, 15 ... Phase angle information, 16 ... System separation command

Claims (2)

When some generators step out due to disturbances such as power transmission line faults in the power system where multiple synchronized generators are linked by transmission lines, this step-out phenomenon will not spread to other generators. In the step-out separation method of the power system for performing system separation,
Obtain the phase information of a wide area of the power system by measuring the bus voltage phase angle of a predetermined electric station in the power system every moment,
To calculate the phase angle difference between the substation from these phase information, and a first preset threshold and the phase angle difference compared respectively, the phase angle exceeds the first threshold value If there is a difference, it is determined that a step-out has occurred, and then, among the phase angle differences, the phase angle difference other than the one that has exceeded the first threshold and has been determined to have step-out, and the first A second threshold value set smaller than the threshold value is respectively compared, and if there is a phase angle difference exceeding the second threshold value, it is determined that a step-out has occurred, and the first threshold value is determined. A step-out generator group is extracted from the phase angle difference exceeding the threshold value and the phase angle difference exceeding the second threshold value, and the step-out mode is estimated from the combination of the extracted step-out generator groups. A step-out separation method for electric power systems, characterized in that optimal system separation is performed. When some generators step out due to disturbances such as power transmission line faults in the power system where multiple synchronized generators are linked by transmission lines, this step-out phenomenon will not spread to other generators. A phase information obtaining means for obtaining phase information in a wide area of the power system by measuring a bus voltage phase angle of a predetermined electric station in the power system every moment in a step-out separation device for a power system for performing system separation; ,
A phase angle difference calculating means for calculating a phase angle difference between the electrical stations obtained by the phase information obtaining means;
Each phase angle difference calculated by the phase angle difference calculating means is compared with a first threshold value set in advance, and if there is a phase angle difference exceeding the first threshold value, the phase angle difference is removed. Next, the phase angle difference is set to be smaller than the first threshold value and the phase angle difference other than the phase angle difference that has exceeded the first threshold value and is determined to be out of step. Each of the second threshold values is compared, and if there is a phase angle difference exceeding the second threshold value, it is determined that step-out has occurred, and the phase angle exceeding the first threshold value is determined. A step-out mode determining means for extracting a step-out generator group from the difference and the phase angle difference exceeding the second threshold, and estimating a step-out mode from the combination of the step-out generator group;
A power system step-out separation apparatus comprising: system separation means for performing system separation based on the step-out mode estimated by the step-out mode determination means.

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