JP2008154378A - Method and apparatus for load flow calculation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for load flow calculation wherein high speed and accuracy are ensured in a simulation of a system after accident in credible accident calculation for electric power systems constructed of a large number of nodes and branches. <P>SOLUTION: The following data is read from a database 9 by a data read unit 22: facility characteristic data of an electric power system constructed of a transmission line, a transformer, a generator, and a switch; and system state data indicating the output value of a generator, an amount of electric load, the switching state of a switch. The inverse matrix of the admittance matrix of an initial system is calculated from data read from the database by a calculation processing unit 20. The load flow of a changed system in which the state of at least one switch in the initial system has been changed is calculated by an input unit. In this calculation, the inverse matrix of the admittance matrix of the initial system, a row-transposed matrix, and its inverse matrix are used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the power system monitoring and control system, the present invention assumes a failure of the power distribution facility, calculates the flow direction and flow rate of the power flow after the failure, and whether there is a violation of the power flow constraint value of the transmission line and the transformer. The present invention relates to a tidal current calculation method and apparatus.

  Assumed accident calculation, for example, as described in [Patent Document 1], after creating an admittance matrix based on the connection state of the power system after the failure occurs, an inverse matrix of the admittance matrix is obtained, and the generator output value and power By multiplying the load amount by this inverse matrix, the phase angle of the bus is obtained, the power flow flowing through the transmission line and transformer is obtained from the obtained phase angle, and the limit value is compared with the power flow limit value of the transmission line and transformer. If the value exceeds the value, the operator is warned that the operation of the power system is hindered due to the occurrence of a failure, that is, there is a risk of continuing the operation. Moreover, since a failure may occur accidentally in all facilities, it is necessary to perform the above-described processing for all facilities.

  In the case of a power system composed of a large number of facilities, the degree of the admittance matrix becomes very large, and it takes time to calculate the inverse matrix. Therefore, the assumed accident calculation was performed in a long cycle of 30 minutes to 1 hour. On the other hand, since it is necessary to perform the risk management at the time of the equipment failure in a cycle of several seconds to several tens of seconds, an operation target value monitoring function which is a simple assumed accident calculation is introduced, or [Patent Document 2] As described, by using the severity of the assumed accident case, calculate the power flow of the case where the equipment that has a large impact on the system at the time of failure does not calculate the power flow for every failure. The method of shortening the calculation time was taken.

  Here, the operation target value monitoring function is a function that examines the influence when a failure occurs by fixing the connection of the power system in advance, and monitors the power flow based on the examination result.

  For example, in a radial power system that does not have a loop configuration, it is known that when a simple parallel two-line failure occurs, the power flow before the failure of that line flows to the remaining lines. Then, the total tidal current of two parallel lines was compared with each heat capacity limit value.

JP 2004-343901 A JP 2000-270477 A

  In an electric power system, it is assumed that a failure occurs accidentally for all electric power facilities such as lightning. These accidental failures may occur at multiple facilities at the same time, but may not be considered probabilistic in the power system, or to avoid a power outage when multiple failures occur simultaneously. Compared to investment, it is acceptable. Therefore, in the assumed accident power flow calculation function, it is common to assume that one facility failure occurs for all power facilities in the power system before the failure occurs. That is, in the power flow calculation of the assumed accident of the power system composed of N pieces of equipment, the admittance matrix changes if the equipment that fails, so it is necessary to calculate the inverse matrix of N times of the admittance matrix. Generally, this assumed level is referred to as an N-1 accident because one of the N facilities fails. In addition, the number of power facilities constituting the power system is not only spreading locally, but also a huge number. That is, since the order of the admittance matrix is proportional to the number of nodes installed, the order of the matrix in the actual power system is a very large value. Further, the number of inverse matrix computations is on the order of the square of the matrix order, and a long time computation is required to obtain the inverse matrix of the admittance matrix of the power system having a large degree.

  For this reason, a high-speed computer and a large amount of computing resources are required in order to provide the operator with the tidal current calculation results of the assumed accident in real time.

  If the power system is operated in a loop configuration, the range of influence at the time of failure will be complicated, so operation target value monitoring cannot be applied. When the two lines are not symmetric, there is a problem that the influence after the occurrence of the failure cannot be accurately grasped. The loop operation of the electric power system is one method for reducing the probability of supply failure when a failure occurs, and the fact that the loop operation cannot be performed can be a great restriction on stable supply. In addition, since the impact cannot be accurately simulated, the threshold is strictly monitored and the operation is performed on the safer side, and the facility efficiency that maximizes the capacity of the facility according to the actual load. Will be reduced.

  A first object of the present invention is to provide a power flow calculation method and apparatus capable of performing power flow calculation of an assumed accident in a cycle of several seconds to several tens of seconds and appropriately performing risk evaluation when a failure occurs.

  It is a second object of the present invention to provide a power flow calculation method and apparatus capable of obtaining an accurate simulation result without limiting the configuration of the power system for risk evaluation at the time of failure occurrence. .

  A third object of the present invention is to provide a tidal current calculation method and apparatus capable of obtaining an inverse matrix of N admittance matrices at high speed and performing a tidal current calculation of an assumed accident without a high speed computer and a large amount of computer resources. There is.

  In order to achieve the above object, a power flow calculation method and apparatus according to the present invention store an inverse matrix of an admittance matrix of a power system before the occurrence of a failure in a power facility, and store an inverse matrix of the admittance matrix of the power system after the occurrence of a failure. , By correcting the inverse matrix of the power system admittance matrix before the failure occurs based on the partial change of the power system connection due to the failure, and calculating the inverse matrix of the calculated power system admittance matrix after the failure occurrence It is used to calculate power flow.

  According to the present invention, a power flow calculation of an assumed accident can be executed at intervals of several seconds to several tens of seconds, and risk evaluation at the time of occurrence of a failure can be performed appropriately.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic overall configuration diagram of a tidal current calculation device 1, FIG. 2 is a detailed configuration diagram of the tidal current calculation device, and FIG. 3 is a calculation processing flow diagram of a tidal current calculation method to which this embodiment is applied.

  The power flow calculation device 1 is roughly configured by a central processing unit 2 (also referred to as a CPU 2), a main storage device 3, an input / output device 4, and an external storage device 5. The calculation processing is processed by the central processing unit 2, and necessary processing programs, data used for calculation, and calculation results are held in the main storage device 3. Data necessary for the calculation is read from the external storage device 5 or set from the input / output device 4.

  Details of the tidal current calculation apparatus 1 will be described with reference to FIG. As shown in FIG. 2, the power flow calculation device 1 includes an input device 6, a display device 7, and a reading device 10 which are input / output devices 4, a database 9 stored in the main storage device 3 or the external storage device 5, and a CPU 2. The calculation processing unit 20 is provided.

  The calculation processing unit 20 is realized by the CPU 2 executing a program previously stored in the storage medium of the external storage device 5 and read into the main storage device 3 via the reading device 10. In addition to such a programmed general-purpose processor, the calculation processing unit 20 can be configured, for example, by a combination with a specific hardware device including a wired logic that executes each process.

  The input / output device 4 includes the input device 6 having a keyboard and a mouse shown in FIG. 2 and the display device 7 as an output device. In addition, the input / output device 4 includes an input device such as a pointing device and a touch sensor, and an output device such as a liquid crystal display device, a printer, and a speaker, which can be substituted or used together.

  The input device 6 accepts selection of options displayed on the display device 7, data input, and the like, and transmits them to the calculation processing unit 20. The display device 7 displays the data transmitted from the input device 6 and processed by the calculation processing unit 20.

The external storage device 5 includes a hard disk device, a floppy disk (registered trademark) device,
A CD-ROM (compact disc-read only memory) device, a DAT (digital video tape) device, a RAM (random access memory) device, a DVD (digital video disc) device, a nonvolatile memory, or the like can be used. The external storage device 5 includes a large-capacity storage device for holding the database 9 shown in FIG. 6, a storage medium for holding processing programs and the like, and a reading device 10 for reading information held in the storage medium. Use. In addition, both the database and the processing program can be held in one external storage device. As the storage medium, a floppy disk, CD-ROM, magnetic tape, optical disk, magneto-optical disk, DAT, RAM, DVD, nonvolatile memory, or the like can be used.

  The calculation processing unit 20 includes a control unit 21, a data reading unit 22 connected via the control unit 21, a system division determination unit 23, a virtual branch setting unit 24, an inverse matrix calculation unit 25, a phase angle calculation unit 26, a power flow A calculation unit 27 and a calculation result output unit 28 are provided. The calculation processing unit 20 is connected to the external power system 11 via the communication line 31, and the power system 11 is connected to the power system 12 that is an actual transmission / reception substation facility via the communication line 32. . Here, the control unit 21, the data reading unit 22 connected via the control unit 21, the system division determination unit 23, the virtual branch setting unit 24, the inverse matrix calculation unit 25, the phase angle calculation unit 26, and the power flow calculation unit 27. In order to represent the whole or a part of the calculation result output unit 28, for example, the processing units 22 to 28 and the processing units 24 to 28 are referred to.

The electric power system 11 is connected to an electric power system 12 which is an actual transmission / substation substation equipment, and includes a monitoring control system and a planning / operation system for the electric power system 12. Moreover, an internal database (not shown) for holding information indicating the power system 12 and the state of the power system 12 and the like is provided. The state of the power system 12 is detected by a relay, a sensor, or the like, notified to the power system 11 via the communication line 32, and stored in an internal database (not shown).

  The control unit 21 processes and processes data for smoothly transmitting and receiving data and processing programs between the power system 11 and each of the processing units 22 to 28, and controls the transmission and reception to normalize the entire processing. To work. In addition, the generator output of the power system 12, the load and the switching state of the switch are monitored, and the generator output data of the power system 12 and the switching state of the switch, which is the connection state of the system equipment, are captured from the power system 11. The fetched data is periodically stored in the database 9.

  The data reading unit 22 reads data held in the database 9 through the control unit 21, and these data are transmitted to the processing units 24 to 28 through the control unit 21.

  The database 9 stores the characteristics of the equipment constituting the system, which is equipment characteristic data, the switch opening / closing state, the generator output value, the power load amount, etc., which are system state data, and is changed from the initial system state. For example, preconditions such as equipment that causes an assumed failure in the assumed accident calculation, a change in generator output or load, and a new equipment to be added to the system are stored.

  In the present embodiment, data reading from the database 9 is performed via the data reading unit 22 unless otherwise specified.

  The calculation processing unit 20 generates a power plant based on the data transmitted from the input device 6, the data read from the database 9, the processing program read from the reading device 10, and the data transmitted from the power system 11. Create a supply and demand plan.

  The system division determination unit 23 determines whether or not the system is divided into two or more based on the value read from the data reading unit 22 and the system state change condition.

  The virtual branch setting unit 24 does not have a regular admittance matrix when the system division is determined by the system division determination unit 23. Therefore, the branch, the both-end nodes of the branch by the system change, or the system without the swing node by the system division A small admittance is set between the side node and the ground.

  The inverse matrix calculation unit 25 calculates the matrix of the first system state and holds the calculation result in the database 9 and the main storage device 3. Alternatively, instead of calculating the value of the inverse matrix, the forward / backward matrix necessary for calculating the inverse matrix for calculating the power flow calculation is calculated, and the calculation result is held in the database 9 and the main storage device 3.

  The phase angle calculation unit 26 calculates a permutation inverse matrix, and further calculates the phase angle of each node by multiplying the permutation matrix with the power injected by each node based on the generator output and load.

  The tidal current calculation unit 27 calculates the tidal current of the branch by multiplying the phase difference between both end nodes of each unit lunch by the admittance of the branch. Furthermore, the tidal current value of each branch is compared with the tidal current constraint value of that branch. If the tidal current value is larger, it is determined that the load is overloaded.

  Here, the processing contents in the processing units 23 to 27 will be described in detail.

  First, the failure of the power equipment in the power system and after the failure will be described. When a short-circuit failure or ground fault occurs in power facilities such as power transmission lines or transformers due to natural disasters such as lightning or strong winds, a protection device for the power system is used to prevent the occurrence of these failures and maintain power distribution. Operate the circuit breaker and so on to shut off the faulty equipment and healthy equipment.

  For example, when a short circuit failure occurs in a power transmission line, the protection device cuts off the circuit breaker that connects the power transmission line and the bus line, and disconnects the power transmission line in which the failure has occurred from a healthy system. The state in which this protective device is operating is the state after the occurrence of the failure. After the failure occurs, the connection state of the power equipment is different from that before the failure occurs, and therefore the direction and flow rate of the power flow are different before and after the failure occurs.

  Next, of the power flow calculation methods, DC method power flow calculation will be described. In the DC method power flow calculation, the power equipment is divided into nodes and branches, and the power injected into the node (power generation amount or load amount) and the phase angle of the node are simulated as shown in Equation 1.

ここで、θはノードの位相角を要素としたベクトル、Ｐはノードの注入電力を要素としたベクトル、Ｙはアドミタンス行列である。

Here, θ is a vector whose element is the phase angle of the node, P is a vector whose element is the injected power of the node, and Y is an admittance matrix.

  The admittance matrix is composed of the imaginary part of the admittance of the transmission line and the transformer, and expresses the connection state of the power system at the same time. In the DC method power flow calculation, since the admittance matrix is not regular, the admittance matrix Y is a cofactor matrix in which a swing node is determined and rows and columns corresponding to the swing node are deleted. In the swing node, balancing the injected power to each node (referred to as supply / demand balance) and maintaining the supply / demand balance is called “wrinkle removal”.

  Since the tidal current flowing in the power transmission line and the transformer can be obtained if the phase angles at both ends of the power transmission line and the transformer are known, θ is obtained from Equation 1 as shown in Equation 2.

ここで、Ｙ^-1はアドミタンス行列の逆行列である。

Here, Y ⁻¹ is an inverse matrix of the admittance matrix.

The tidal current flowing in a transmission line or transformer is (θ _i −θ _j ) · X, where θ _i and θ _j are the phase angles of both end nodes of the transmission line and transformer branch, and X _ij is the admittance of the branch. You can find it with _ij .

  For example, in the flow calculation of an assumed accident, it is necessary to obtain an inverse matrix of an admittance matrix after a failure for all failures.

  On the other hand, when a failure occurs, the connection state of the power system changes partially. For example, since a transmission line is disconnected in a simple transmission line failure, one branch is deleted from the connection state before the failure, but the other connection state is not changed. Even in the case of a bus failure, the branch connected to the bus is simply deleted.

  By considering the characteristics of the power system, the inverse matrix before failure is corrected from the change in the connection state of the power system without obtaining the inverse matrix of Formula 2 from the beginning, and the inverse matrix after the assumed failure is obtained. A method will be described.

  We examine the difference between the admittance matrix before failure and the admittance matrix after assumed failure.

Focusing on the i-th row of the admittance matrix, the element X _{ij in the} j-th column is as follows. That is, when j ≠ i (non-diagonal element), the mutual admittance between the node i and the node j, and when j = i (diagonal element), the self-admittance of the node i.

  For example, when a fault occurs in a transmission line, the switches at both ends of the transmission line branch are opened, and this transmission line branch is deleted in the computer model. If i, j, the mutual admittance between the node i and the node j and the self admittance of the node i and the node j are changed. That is, in the case of a transmission line failure, the two rows (i-th row and j-th row) of the admittance matrix before the failure change from the admittance matrix after the failure, but the other elements are the same before and after the failure. .

  Since all faults generally result in the deletion of one or more branches, the admittance matrix after the fault is one with partial row permutation relative to that before the fault.

Since the admittance matrix is a square matrix, the row replacement operation of the admittance matrix is equivalent to multiplying the admittance matrix by the row replacement matrix from the left. That is, if the admittance matrix is Y ₀ and the row permutation matrix is E ₁ , then the matrix Y ₁ after the replacement of the row of Y ₀ is expressed by Equation 3.

From this, the inverse matrix Y ₁ ^-1 of Y ₁ can be expressed as Equation 4.

As described above, the deletion of the transmission line branch corresponds to the replacement of two rows. Therefore, if the operation of Equation 4 is repeated twice, the inverse matrix Y of the admittance matrix with the two rows replaced as shown in Equation 5. ₂ ^-1 can be obtained.

  As described above, the inverse matrix of the admittance matrix after the failure can be obtained by partially correcting the inverse matrix of the admittance matrix of the system before the failure by using the row permutation matrix.

Here, a method of calculating the inverse matrix E ⁻¹ of the permutation matrix E when A = E × B will be described. If the matrix shown in the upper left of FIG. 4 is the matrix B and the matrix shown in the upper right is A, it is assumed that the matrix equation is established by multiplying the matrix E shown in the lower part of FIG.

  However, it is assumed that the element rj of the matrix E satisfies the relationship Σri × bji = aj. At this time, the inverse matrix E-1 of the matrix E is as shown in the lower right of FIG. Here, it is assumed that the element in the j-th column of the inverse matrix E-1 satisfies the following condition. That is, when i ≠ j, rj + ri × dj = 0 to dj = −rj / ri, and when i = j, rj × dj = 1 to dj = 1 / rj.

  As described above, the row permutation matrix is a modification of only the row for which the unit matrix is to be replaced, so the number of operations for calculating the inverse matrix of this permutation matrix is very small, and the computation time is There is an advantage of being short.

In the description so far, description has been made on the assumption that the row permutation matrices E ₁ and E ₂ are regular, that is, an inverse matrix exists. In order to maintain the regularity of the permutation matrix, it is conceivable to make the admittance value very small instead of deleting the transmission line branch.

  FIG. 5 shows that the system after the failure cannot be simulated only by reducing the admittance of the failure facility. In FIG. 5, in order to simulate the state 202 in which the branch 2-3 has failed with respect to the state 201 before the failure, even if the admittance of the branch 2-3 is reduced, a state 203 flows in the branch. Therefore, the tidal current state 202 after the failure cannot be simulated.

  Next, the case where the row permutation matrix is irregular will be described.

  FIG. 6 shows a concept of a system conversion method for maintaining regularity of the admittance matrix. The system before the failure indicated by reference numeral 301 is divided due to the failure indicated by reference numeral 302, and the conversion of the system when the system indicated by reference numeral 303 is divided is shown.

Assume that the row permutation matrix becomes irregular when a row permutation that deletes a branch between the node i and the node j is performed. In this case, it is necessary to set the admittance of a branch (hereinafter referred to as B _ij ) between the node i and the node j to a minute value, and to further add a minute value to the self-admittance. This is equivalent to a power system in which branches (hereinafter referred to as B _iG and B _jG ) are added between the node i and the ground and between the node j and the ground, as indicated by reference numeral 303 in FIG. Here, “equivalent” means that there is no significant difference in tidal current. At this time, the admittance of B _ij is set to X _ij , B _iG , and the admittance of B _jG is set to X _iG , respectively.
_Assuming X _jG and the admittance of a general branch as X, the relationship among the values of X, X _iG , X _jG , and X _ij is set as shown in _Equation 6.

With this setting, the power flow from the divided power systems A and B flows into B _iG or B _jG, and therefore does not flow into B _ij . That is, there is no significant power distribution between the divided power systems. In the power system including a swing node, “wrinkle removal” is performed at the swing node, and a balance between supply and demand is maintained.

In addition, in the divided power system, not only the system including the swing node but also the other system is operated as a single system. And add a branch between the ground. However, when the admittance of the branch and X _S, in order to accurately calculate the value of _{tide, X, X iG, X jG} , X ij, be set to the relationship between the values of X _S as in equation 7 I must.

  The processing result of the calculation processing unit 20 is sent to the display device 7 for display and stored in the database 9. The calculation result output unit 28 displays the calculation conditions set and calculated by the processing units 22 to 27, the calculation result, information for supporting data input from the input device 6, and the like on the display device 7. Further, the calculation result is sent to the power system 11 via the control unit 21.

  As this information, it is understood that the result of comparing the calculated tidal current value of each facility and the constraint value of the facility, the information indicating that the system has been changed, the changed admittance, the admittance before the change, and the virtual branch are set. Information, virtual branch admittance, information that identifies the node specified as a swing node, information about the presence or absence of a tidal constraint violation, information that identifies the equipment that has changed when a tidal constraint violation occurs, At least one of the tidal current value and the constraint value is output.

  When a power flow calculation is requested under the conditions set by the monitoring control system and operation / planning system of the power system 11, the calculation result and evaluation result created by the calculation processing unit 20 are also notified to the power system 11. The The power system 11 issues a command to change the on / off state of the switch that is a component of the power system 12 based on the notified calculation result or evaluation result, and changes the system configuration, and issues an output control signal to the generator. To control the generator. With this control, for example, an overload is prevented from occurring even if an accident occurs.

  Next, the operation will be described with reference to the processing flowchart shown in FIG.

  In the facility data reading of the process 101, the characteristics of branches of power transmission lines, transformers and the like stored in the database 9 and the constraint values of these branches are read. The characteristics of these facilities are basically fixed values, and can be set by the input device 6 as necessary. Also read the admittance value of the virtual branch. The numerical value shown in parentheses between the nodes in the system example indicated by reference numeral 401 in FIG. 7 is the admittance of each branch. Further, it is read that the rightmost node in the system example indicated by reference numeral 401 is a swing node.

  In the system state reading of the process 102, what changes from time to time is read from the database 9. From the database 9, the switching state of the switch, which is the state of the system, the output of the generator used as node injection power, and the load value are read. Here, in order to use the current state of the power system, the state of the system may be taken directly from the power system. Alternatively, a person may input these states from the input device 6.

  In the calculation change condition setting of the process 103, a faulty equipment group is set, or a generator or load value to be changed is set. For example, reference numeral 401 in FIG. 7 indicates the power system, the injected power, and the power flow before the failure. For simplicity, all branches have an admittance of 1.0.

  In the power system example indicated by reference numeral 401 in FIG. 7, it is read that the branches between nodes connected by solid lines such as node 1 and node 2 are connected. Further, a generator is connected to the node 1, 10 outputs are injected from the generator, a load having a load value of 20 is connected to the node 3, and a generator connected to each node, Or load and its value are read. Here, the output of the generator is positive injection power and the load is negative injection power.

  In the admittance inverse matrix calculation of the process 104, an initial admittance matrix for the initial state set in the processes 101 and 102 is set, and an inverse matrix of the initial admittance matrix is calculated.

In the power system example indicated by reference numeral 401 in FIG. 7, the initial admittance matrix Y ₀ is indicated by reference numeral 402, and the matrix indicated by reference numeral 403 is an inverse matrix Y ₀ ⁻¹ of the initial admittance matrix Y ₀ .

In order to finally calculate the power flow of each branch, the phase angle of each node is calculated by applying the node injection power to Y ⁻¹ in Equation 2. The phase angle is calculated by multiplying the inverse matrix of the permutation matrix of Equation 5 and the node injection power P first and then multiplying by Y ⁻¹ . Therefore, instead of calculating Y ⁻¹ itself, it is also possible to calculate L or L and U obtained by LD decomposition or LUD decomposition of the matrix Y.

The process 105 calculates the power flow of each branch in the initial system. As shown in Equation 2, the phase angle θ of each node is calculated using Y ⁻¹ calculated in the process 104 and the node injection power P, and then the difference between the phase angles θ of the nodes at both ends of each branch and By multiplying the admittance of a branch, the current of the branch can be calculated. The magnitude and direction of the tidal current are indicated by arrows near each branch of the power system example indicated by reference numeral 401 in FIG. In this way, the tidal current calculation result is displayed on the display device 7 as indicated by reference numeral 401 in FIG.

  Further, when comparing the tidal current of each branch with the tidal current constraint value of the corresponding branch read in the processing 101, if the tidal current is larger, the branch name where the tidal current constraint violation occurred, the tidal current value and the constraint value are shown in FIG. It is displayed at the lower left of the power system indicated by reference numeral 401. In the power system example indicated by reference numeral 401, since no tidal current constraint violation has occurred, “no tidal current constraint violation” is displayed as a message.

  The process 106 checks whether each of the calculation change conditions set in the process 103 includes a change in the state of the switch. Here, when the change of the switch is accompanied, the process proceeds to processing 107, and when the change of the switch is not accompanied, the process proceeds to process 113.

  In the process 107, it is checked whether or not the system division occurs with the change of the switching state of the switch. Cases in which system division does not occur with the opening and closing of the switch are the case where the branch constituting the loop is opened as in the example of the power system indicated by reference numeral 501 in FIG. However, the admittance may change when the one-line switch is opened. When the system does not divide, the regularity of the admittance matrix after the normal change is maintained. On the other hand, when the system is divided, the regularity of the admittance matrix is not maintained.

The process 112 is a process for correcting the admittance matrix when the system is not divided. The power system example indicated by reference numeral 501 in FIG. 8 is a power system in which the branch 3-5 in the power system example indicated by reference numeral 401 in FIG. When the branch 3-5 is released, the admittance matrix Y ₀ indicated by reference numeral 402 in FIG. 7 changes to an admittance matrix Y _A indicated by reference numeral 502 in FIG.

In the process 109, the inverse matrix Y _A ⁻¹ of the admittance matrix after the system change is calculated using the inverse matrix Y ₀ ⁻¹ of the initial admittance matrix and the permutation matrix E. From the power system example indicated by reference numeral 502 in FIG. 8, the admittance matrix after the branch between the nodes 3-5 is deleted includes the third and fifth lines of the admittance matrix before failure indicated by reference numeral 402 in FIG. You can see that it has changed.

The matrixes denoted by reference numerals 601 and 602 in FIG. 9 indicate a row permutation matrix E ₁ for transposing the third row of Y ₀ and its inverse matrix E ₁ ⁻¹ . Matrixes denoted by reference numerals 603 and 604 indicate a row permutation matrix E ₂ for transposing the fifth row of E ₁ · Y ₀ and its inverse matrix E ₂ ⁻¹ .

FIG. 10 shows that the inverse matrix of the row permutation matrix is multiplied from the right side by the inverse matrix of the admittance matrix before the failure, and the calculation result of Y ₀ ⁻¹ · E ₁ ⁻¹ · E ₂ ⁻¹ is shown in FIG. 8 indicates that it matches the inverse matrix Y _A ⁻¹ of the admittance matrix after failure indicated by reference numeral 503 of FIG.

Thus seeking admittance matrix Y _A of the power system after a failure indicated by the reference numeral 501 in FIG. 8, without calculating the inverse matrix Y _A ^-1 of the direct matrix Y _A, inverse pre-fault admittance matrix Y ₀ by operating the ^-1, as shown by the number 8, it can be calculated inverse matrix of admittance matrix Y _a ^-1 after failure.

  The process 110 is the same tidal current calculation process as the process 105. Since the system state has changed from the process 105, the data used for the calculation is different, but the calculation process is basically the same.

  The phase angle of each node is calculated using the inverse matrix of Equation 8 as shown in Equation 9.

Alternatively, as shown in Equation 10, there is also a method of calculating by multiplying the inverse matrix of the permutation matrix and the node injection power and finally multiplying by the inverse matrix Y ₀ ⁻¹ of the initial admittance matrix. In this case, the phase angle θ shown in Formula 10 can be calculated by forward and backward processing using the matrices L, U, and D in which Y ₀ has been subjected to LD decomposition or LUD decomposition in processing 104.

  The magnitude and direction of the tidal current are indicated by arrows near each branch of the power system example indicated by reference numeral 501 in FIG. The branch flow between the deleted nodes 3-5 is zero. This tidal current calculation result is displayed on the display device 7 as in the example of the power system indicated by reference numeral 501 in FIG.

  Further, when comparing the tidal current of each branch with the tidal current constraint value of the corresponding branch read in the processing 101, if the tidal current is larger, the branch name where the tidal current constraint violation occurred, the tidal current value and the constraint value are shown in FIG. It is displayed at the lower left of the power system indicated by reference numeral 401. Alternatively, when calculating the tidal current when each facility has failed for the assumed failure calculation in the process 103, which facility has failed in the tidal current calculation, whether or not the virtual branch is set, whether or not the system is divided, and Whether there is a facility that violates the tidal constraint, and when the constraint is violated, the facility, the tidal current value of the facility, and the constraint value are displayed. In the power system example indicated by reference numeral 501, the message indicates that there is a failure in the branch 3-5, there is no virtual branch, there is no system division, and there is no facility in which a tidal current constraint violation has occurred.

  In the process 111, it is determined whether or not the calculation condition change target equipment or the node injection power change target set in the process 103 still remains, and if the power flow calculation is performed for all changes, the process ends. Whether or not the calculation condition change still remains is determined, for example, by determining whether or not the power flow calculation is performed when the necessary failure target facility is deleted in the assumed failure calculation.

  The process 108 is a process for setting the admittance of the virtual branch when the system division occurs in the process 107. At this time, the row permutation matrix is not regular, and the following processing is performed. In the example of the power system indicated by reference numeral 801 in FIG. 11, there is a system and a power flow in which there is a failure between the branches 2-3 and the branch 2-3 is deleted. This system is an example of being divided into two power systems by deleting the branch 2-3. Since the admittance matrix at this time is a matrix indicated by reference numeral 802, it can be seen that the second row is -1 times the first row, so that it is clearly not regular.

  FIG. 12 shows a power system and a power flow in which a minute impedance is given to the branch 2-3 and a minute admittance branch is added between the node 2 and the node 3 to the ground. Here, the parentheses indicate the given admittance. These minute admittances are values read in the processing 101, the deleted branch 2-3 is 0.000001, and both end nodes are 0.001. The admittance of other branches is 1, which satisfies the relationship of Equation 6. The admittance matrix is corrected in consideration of these minute admittances.

  FIG. 12 shows the power flow calculation result of the processing 110 when the minute admittance is added in the example of FIG. 11 in which system division occurs. By comparing the tidal values of each branch of FIGS. 11 and 12, it can be seen that there is no significant difference between the tidal current of the power system of FIG. 12 to which the virtual branch is added and the tidal current of FIG.

  FIG. 13 shows a power system obtained by adding a ground branch of a minute admittance to a swing node candidate node in the power system shown in FIG. The numerical values in parentheses in FIG. 12 indicate admittance. The minute admittance of the virtual branch is 0.000000001 for the branch 2-3, the minute admittance of the ground virtual branch at both end nodes of the deleted branch is 0.000001, and the minute admittance of the virtual branch of the node 1 set as the swing node is 0.00. 001, which satisfies the relationship of Equation 7. This shows that there is no significant difference from the current when node 1 is a swing node.

  The process 113 is a process in the case where the injection power to the node is changed instead of the switching state of the switch according to the calculation change condition of the process 103. In this case, since the admittance matrix is the same as the initial matrix, the power flow can be calculated in the process 110 by changing the node injection output. Thereby, it is possible to check whether or not a power flow constraint violation occurs when some of the injected power changes with respect to the power flow state of the initial system.

  In this way, it stores the inverse matrix of the admittance matrix of the power system before the system state change of the power equipment, and connects the partial matrix of the power system after changing the system to the inverse matrix of the admittance matrix of the power system after the system state change. By calculating the inverse matrix of the permutation matrix representing the change and the inverse matrix of the admittance matrix of the power system before the system state change, the admittance matrix after the system state change is calculated for each node without calculating the inverse matrix. Since the phase angle can be calculated and the tidal current of each branch can be calculated using the phase angle and the admittance matrix, the calculation time of the tidal current can be increased.

  As a result, it is possible to calculate the power flow of an assumed accident at intervals of several seconds to several tens of seconds, and to appropriately perform risk assessment when a failure occurs. Moreover, the configuration of the power system is not limited for risk evaluation when a failure occurs, and a highly accurate simulation result can be obtained. In addition, the inverse matrix of N admittance matrices can be obtained at high speed, and the power flow of an assumed accident can be calculated without a high speed computer and a large amount of computer resources.

1 is an overall configuration diagram of a tidal current calculation apparatus according to an embodiment of the present invention. The block diagram which shows the detailed structure of the tidal current calculation apparatus of a present Example. The figure which shows the processing flow of the tidal current calculation of a present Example. The figure explaining calculation of a permutation matrix. The figure which showed the example in which the tidal current calculation at the time of system division fails. The figure explaining the conversion method of the system | strain which used micro admittance at the time of system | strain division. The figure which shows the screen and admittance matrix of the tidal current calculation result before a system change. The figure which shows the screen and admittance matrix of a tidal current calculation result when the system division after a system change does not generate | occur | produce. The figure which shows a permutation matrix and its inverse matrix. The figure which shows the calculation example of the inverse matrix of an admittance matrix. The figure which shows the screen and admittance matrix of a tidal current calculation result when dividing a system after a system change. The figure which shows the screen of the tidal current calculation result when very small impedance is set to the virtual branch at the time of system division. The figure which shows the screen of the tidal current calculation result when setting a virtual branch to the swing node of the system | strain divided | segmented at the time of system | strain division.

Explanation of symbols

1 Current flow calculation device 2 Central processing unit CPU
3 Main storage device 4 Input / output device 5 External storage device 6 Input device 7 Display device 8 Printing device 9 Database 10 Reading device 11 Power system 12 Power system 20 Calculation processing unit 21 Control unit 22 Data reading unit 23 System division determination unit 24 Virtual Branch setting unit 25 Inverse matrix calculation unit 26 Phase angle calculation unit 27 Power flow calculation unit 28 Calculation result output unit

Claims (10)

  A data reading unit for reading power system equipment characteristic data and system state data recorded in the database, an input unit for setting calculation change conditions, and a power system equipment characteristic read by the data reading unit and the input unit Obtain and store the inverse matrix of the initial system admittance matrix from the data and system state data, and multiply the inverse matrix of the initial system admittance matrix by the row permutation matrix and the inverse matrix of the row permutation matrix obtained from the calculation change condition setting. The inverse matrix calculation unit for calculating the admittance matrix after setting the calculation change condition and the phase angle for calculating the phase angle of each node from the admittance matrix after setting the calculation change condition and the node injection power calculated by the inverse matrix calculation unit A tidal current provided with a calculation unit and a tidal current calculation unit that calculates the tidal current of the branch from the phase angle calculated by the phase angle calculation unit and the admittance of the branch Calculation apparatus.   A database for storing facility characteristic data of a power system composed of transmission lines, transformers, generators and switches, and a database for storing system output data of generator output values, power load amounts, and switching states of switches The data reading unit for reading data from these databases, and the inverse matrix of the admittance matrix of the initial system are calculated from the data read from the database, and at least one switch state of the initial system is changed by the input unit A tidal current calculation apparatus comprising a calculation processing unit that calculates a tidal current after a system change using an inverse matrix and a row permutation matrix of the admittance matrix of the initial system and the inverse matrix thereof.   The system division determination unit that determines whether or not the power system is divided by changing the switch state, and the admittance matrix is changed according to the system state when the system is not divided, and the system is divided when the system is divided When setting the admittance of the branch between the power grids and the virtual branch between the nodes at both ends of the branch and the ground and dividing the grid, a new swing node candidate is set, and the admittance is set on the virtual branch between the swing node and the ground. The tidal current calculation device according to claim 1, further comprising a virtual branch setting unit to be set.   Comparison result of tidal current calculation value of each equipment and constraint value of the equipment, information showing that the system has been changed, changed admittance, admittance before the change, information showing that the virtual branch has been set, information on the virtual branch Admittance, information that identifies the node specified as a swing node, information on whether or not a tidal constraint violation has occurred, information that identifies the equipment that has changed when a tidal constraint violation occurs, tidal current value and constraint value of a facility that has a tampering constraint violation The tidal current calculation apparatus according to claim 3, further comprising a calculation result output unit that outputs at least one of the two.   The data reading unit reads the facility characteristic data and system state data of the power system, the inverse matrix calculation unit obtains and stores the inverse matrix of the admittance matrix of the initial system, and is obtained from the calculation change condition setting input by the input unit. The admittance matrix and the node after the calculation change condition is set by the phase angle calculation unit by calculating the admittance matrix after setting the calculation change condition by multiplying the row permutation matrix and the inverse matrix of the row permutation matrix by the inverse matrix of the admittance matrix of the initial system A power flow calculation method of calculating a phase angle of each node from injected power, and calculating a power flow of a branch from a phase angle calculated by the phase angle calculation unit and a branch admittance by a power flow calculation unit.   Data reading unit reads facility characteristic data of the power system consisting of transmission lines, transformers, generators, and switches, system output data of generators, power load, and switch status of the switch from the database. Then, the calculation processing unit calculates the inverse matrix of the admittance matrix of the initial system from the data read from the database, and the flow after the system change in which at least one switch state of the initial system is changed by the input unit, A tidal current calculation method of calculating using an inverse matrix and a row permutation matrix of the initial system admittance matrix and an inverse matrix thereof.   If the power system does not break due to a change in the switch state, store the inverse matrix of the admittance matrix of the initial system, and partially correct the admittance matrix in response to the change in the connection of the power system due to the change in the switch state The tidal current calculation method according to claim 5 or 6, wherein an inverse matrix of the admittance matrix after system change is calculated.   When the power system is divided into two or more by changing the switch state, the number of rows and columns of the admittance matrix used for power flow calculation after the system change is the same as the number of rows and columns of the admittance matrix of the initial system The tidal current calculation method according to claim 5 or 6 set to.   By connecting the divided power systems with a virtual branch with minute admittance, and connecting a virtual branch with minute admittance between the nodes at both ends of the branch and the ground, the admittance matrix in the DC method power flow calculation The tidal current calculation method according to claim 8, wherein regularity is maintained and a swing node in a divided system is included.   The power flow calculation method according to claim 9, wherein a virtual branch having a minute admittance between the ground is added in advance to the swing candidate node.

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