JP2633716B2 - Power flow calculation method with voltage adjustment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a power flow calculation method with voltage adjustment for calculating an appropriate bus voltage and an appropriate control amount of a voltage adjustment device.

(Prior art) In order to obtain a voltage solution that satisfies the conditions desired by the analyst as a result of the voltage flow calculation, the analyst needs to calculate the generator terminal voltage, phase adjustment equipment amount, transformer tap position, etc. Is adjusted, and the process of executing the voltage flow calculation and confirming the result is repeated to obtain a satisfactory result.

The optimal power flow calculation means applying an optimization method such as linear programming or quadratic programming adjusts the voltage reactive power balance by minimizing the transmission function or the voltage deviation of the objective function, and adjusts the appropriate voltage. It is possible to calculate the value and the control amount of the voltage adjusting device at that time, and it is applied to a total voltage control and the like by a computer.

(Problems to be Solved by the Invention) In order to repeatedly execute the voltage flow calculation while adjusting the calculation conditions to obtain a satisfactory voltage solution, the analyst requires advanced knowledge and experience, and particularly complicated Under the power system,
Even converging voltage flow calculations can be difficult,
A lot of effort has been spent on this work in the field of electricity.

On the other hand, the optimal power flow calculation method may cause the same difficulty as described above because a convergence solution of the voltage power flow calculation is required as an initial value.

In recent years, there has been a technological trend in which the supply and demand situation is predicted several hours ahead by the computer system at the dispatching center, and voltage power flow calculations are performed under these conditions to utilize it for reliability monitoring and control. In this case, it is difficult to obtain a convergence solution by automatically performing the adjustment of the voltage reactive power balance.

The present invention has been made in view of the above circumstances, and even under conditions where conventional voltage flow calculation cannot be converged, the control amount of the voltage adjustment device is automatically adjusted to adjust the calculation conditions, and the appropriate voltage is adjusted. The solution and the function to calculate the control amount of the voltage regulator required for that purpose not only make the operation of the system operation plan more efficient, but also monitor the reliability of the power system by computer system and control the reliability. It is an object of the present invention to provide a power flow calculation method with voltage adjustment that can also be applied.

[Structure of the Invention] (Means for Solving the Problems) In a voltage power flow calculation method for solving an electric power equation by an iterative approximation method and obtaining an absolute value and a phase angle of a bus voltage, an iterative approximation solution is within the lower and upper limits of operation of the bus voltage. Check if it is maintained, and if it deviates, adjust the input amount of the adjustment equipment group up to the preset number of control points so that the approximate solution satisfies the voltage allowable upper and lower limits, and Phase adjustment equipment group adjusting means for changing the node admittance matrix;
Similarly, the transformer tap adjusting means for adjusting the tap position of the transformer and changing the node admittance matrix so as to satisfy the voltage allowable upper and lower limit values, and the generator reactive power output obtained from the iterative approximate solution is the generator rated power. If it is out of the range, the generator bus is constrained by the reactive power output value so as not to deviate from the rated range, and a terminal voltage that can be balanced with the reactive power output value is obtained as a reference value of the automatic voltage regulator. And generator terminal pressure adjusting means for changing the node constraint condition.

(Operation) If deviations from the upper and lower limits are found in the iterative approximate solution whose accuracy has been successively improved by the iterative approximation method, appropriate control of the voltage regulator is performed to update the calculation conditions. . In the next iteration, since the iterative approximate solution is calculated under the updated calculation conditions, the deviation is reduced or eliminated.

When the above process is repeatedly performed, and there is no deviation from the lower limit in operation, and the error of the iterative approximate solution is sufficiently small and considered as a true solution, it is determined to be convergence, and the calculation is terminated.

In this way, a voltage solution that satisfies the lower limit of operation is obtained.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart for explaining one embodiment of a power flow calculation method with voltage adjustment according to the present invention.

In FIG. 1, 1 is a calculation condition input process, 2 is a voltage flow calculation pre-process, 3 is a process for determining the number of control points of the phase adjustment equipment group, 4
Is an iterative approximate solution calculation process, 5 is a phase adjustment facility group adjustment process, 6 is a transformer tap adjustment process, 7 is a generator terminal voltage adjustment process,
8 is a convergence determination process, 9 is a calculation result output process, 10 is a node admittance matrix, 11 is a node constraint condition, 12 is an approximate voltage solution, and 13 is the number of control points of the phase adjustment equipment group.

First, an outline of the embodiment will be described with reference to FIG. In order to clarify the features of the present invention in the examples,
Conventionally known voltage power flow calculation includes calculation condition input processing 1, voltage power flow calculation preprocessing 2, iterative approximate solution calculation processing 4, convergence judgment processing 8, calculation result output processing 9, node admittance matrix 1
It is noted here that it is composed of 0, node constraint condition 11, and approximate voltage solution 12.

Calculation condition input processing 1 inputs data defining the connection state and operation state of each facility of the power system and the rated constant of each facility, and edits and stores the data as internal data. Next, the voltage flow calculation preprocessing 2 performs a node No. optimal order for speeding up the inverse matrix calculation in the iterative approximate solution calculation processing 4, and defines specified values of voltage, active power, and reactive power of each node. A node admittance matrix 10 that defines the node constraint condition 11, the connection state of the power system, and the circuit constant is created and passed to the iterative approximate solution calculation processing 4.

The phase adjustment equipment group control point number determination processing 3 determines how much voltage reactive power imbalance exists in the input data given as the calculation condition, and accordingly, the phase adjustment equipment group adjustment processing 5 determines the voltage reactive power imbalance. The number of control points 13 is determined.

Since the power equation of the power system is established as a non-linear simultaneous equation relating to voltage, this is solved by an iterative approximation method, and the subsequent processing is executed in an iterative loop.

The iterative approximate solution calculation process 4 sequentially obtains a voltage approximate solution 12 with improved accuracy. The phase adjustment equipment group adjustment processing 5 performs the voltage approximation solution when the error of the voltage approximation solution 12 falls below the allowable range.
The input amount of the phase adjustment equipment group is adjusted so that 12 satisfies the voltage allowable upper and lower limits, and accordingly, the node admittance matrix 10
To change.

At this time, the number of adjustment points of the phase adjustment equipment group is the number of adjustment points
Limit not to exceed the number set in 13.

The transformer tap adjusting process 6 adjusts the transformer tap position so that the voltage approximate solution 12 satisfies the voltage allowable upper and lower limit values when the error of the voltage approximate solution 12 falls below the allowable range. To change the node admittance matrix 10.

The generator terminal voltage adjustment process 7 adjusts the terminal voltage so that the generator reactive power output does not deviate from the rated range when the pixel of the voltage approximate solution 12 falls below the allowable range. Change the constraint condition 11.

If the error of the voltage approximation solution 12 is sufficiently small and can be considered to be equal to the true solution, the convergence determination processing 8 exits the repetition loop and proceeds to the calculation result output processing 9 to edit the calculation result into a predetermined format. Then, the process is terminated. If not, the process returns to the iterative approximate solution calculation process 4. Although omitted for convenience of explanation, a limit value is set for the number of repetitions,
If convergence does not occur even after exceeding this, the processing exits from the repetitive loop and ends.

 Next, each process will be described in detail.

FIG. 2 shows a simple model system for executing the present embodiment.

In FIG. 2, the phase adjustment equipment groups C1 and C2
2, the voltage of N3 is controlled so as to stay within the upper and lower limits of the voltage allowable value, and the taps of the transformers T1, T2, T3 are connected to the node N.
It is assumed that the voltages of 5, N6 and N8 are controlled so as to stay within the upper and lower limits of the allowable voltage value. Also, the voltage of the node N1 is set as long as the reactive power output of the generator G1 does not deviate from the upper and lower limits of the rating.
It shall be restrained by the generator G1. Note that the node
N4 is a swing node.

FIG. 3 is a drawing showing calculation condition data input by the calculation condition input process 1 under the model system shown in FIG. Referring to FIG. 3, the phase adjustment equipment group data D4 will be described. The phase adjustment equipment group C1 is connected to the node N5, which is composed of four capacitors having a unit capacity of 0.08 (pu) and a unit capacity of 0.04 (pu). Are two groups, and as an initial state, two groups of capacitors are turned on. When the present embodiment is executed and the voltage of the node N2 deviates from the range of 1.035 to 1.065 (pu), as many capacitors and reactors as necessary to eliminate the deviation should be turned on / off. Is shown.

The voltage power flow calculation preprocessing 2 performs node number optimal ordering and speeds up the inverse matrix calculation in the iterative approximate solution calculation processing 4 and creates a node admittance matrix. The description is omitted here because it is well known in the technical field and does not relate to the features of the description described in the present embodiment. Also, the iterative approximate solution calculation processing 4 and the convergence determination processing 8 are both well-known as general processing functions of the voltage power flow calculation, and therefore description thereof is omitted for the same purpose as described above.

The phase control equipment group control point number determination processing 3 first calculates the total load active power under the calculation conditions.

In an actual power system, the total demand and the sum of the phases are in a relationship as shown in FIG. 4, so in the present embodiment, such information is stored in advance, and the sum of the load active power calculated in advance is calculated. On the other hand, it is necessary to find out how many phase adjustment equipment groups are appropriate in the entire power system. Next, if the sum of the initial input amounts of the phase adjustment equipment group under the calculation conditions is calculated, the excess or deficiency of the phase adjustment equipment quantity included in the calculation conditions is obtained,
Accordingly, if the excess or deficiency is large, the number of control points is increased, and if the excess or deficiency is small, the number of control points is reduced.

Next, the phase adjustment equipment group adjustment processing 5 will be described in detail with reference to FIG. In step S51, the maximum value of the reactive power residual of each node is checked, and if this is equal to or less than the allowable value, it is considered that the adjustment is possible. The reason for this is that when the reactive power residual is large, the accuracy of the voltage approximation solution is insufficient, so that it is impossible to appropriately adjust the phase adjustment equipment group. In step S52, the voltage of the monitoring node of each phase adjustment facility group is checked. If the voltage deviates from the upper and lower operation limits, the deviation is divided by the width of the upper and lower limits (dead zone width), and the normalized deviation is calculated. And passes it to step S53. In step S53, the phase adjustment equipment groups are rearranged in ascending order of the absolute value of the normalized deviation. According to this order, steps S54 and S55 determine the number of control points determined in the phase adjustment equipment group control point determination processing 3 by the number of control points. Is only repeated. In step S54, if the voltage drop, that is, the normalized deviation is a negative value, the capacitor 1 group is turned on or the reactor 1 group is opened, and if the voltage rises, that is, if the normalized deviation is a positive value, the capacitor 1 group is opened. Alternatively, one reactor is charged. In either case, the result is reflected in the diagonal components of the node admittance matrix 10. In step S55, first, it is checked whether or not the phase adjustment equipment group operated in step S54 has been operated at the last time before the return of the iterative approximation calculation.If the operation has been performed last time, If the operation is the reverse of the above, it is considered that hunting has occurred in the operation of the phase adjustment facility group, and the fact is passed to step S56. In step S56, if hunting is detected at any one point in the series of operation of the phase adjustment equipment group, step S57 is executed.In step S57, the number of control points is reduced by 1 and the next step of the iterative approximation calculation is repeated. Limit the number of control points of the phase adjustment equipment group in the first time.

In the present embodiment, the phase adjustment equipment group is controlled according to the voltage value of the monitoring node. However, the voltage value of the monitoring node is actually affected by all the phase adjustment equipment groups installed in the vicinity. The value alternates between the upper and lower limits. It may be impossible to converge. In this case, since it is effective to suppress the control amount of the phase adjustment equipment group, steps S55 to S
Each of the 57 processes is very effective.

Next, the transformer tap adjustment processing 6 will be described in detail with reference to FIG.

In step S61, the maximum value of the reactive power residual of each node is checked, and if it is equal to or smaller than the allowable value, it is considered that the adjustment is possible. That is, the process is the same as that in step S51. If it is determined in step S61 that the adjustment is possible, steps S62 to S66 are executed for all the transformers. In step S62, the voltage value of the monitoring node is checked. If the voltage value deviates from the upper and lower limit values, the deviation amount is stored.
Here, if there is no deviation as shown in step S63, the control of the transformer is not performed.

Next, in step S64, the effect on the voltage value of the monitoring node when the tap of the transformer is operated by the unit amount, that is, the voltage sensitivity coefficient is obtained.

The voltage sensitivity coefficient is obtained by the following method. Before and after adjustment, the sum F of active power and the sum G of reactive power flowing into and out of the node are always 0. Before adjustment: F (V, C _q , θ) = 0... (1) G (V, C _q , θ) = 0 (2) Here, F and G are vectors.

Adjusted: the _{F (V + ΔV, C q} + ΔC q, θ + Δθ) = 0 ...... (3) G (V + ΔV, C q + ΔC q, θ + Δθ) = 0 ...... (4). Here, Δ indicates a change in each amount before and after the adjustment, V: node voltage θ: phase angle of the node voltage C _q : reactive power related adjustment variable of the transformer tap.

Next (3), Expanding retailer to (4), F (V + ΔV, C q + ΔC q, θ + Δθ) = F (V, C q, θ) + F v · ΔV + F cq · ΔC q + F θ · Δθ ... ... the (5) G (V + ΔV , C q + ΔC q, θ + Δθ) = G (V, C q, θ) + G v · ΔV + F cq · ΔC q + G θ · Δθ ...... (6). Here, F _v , F _cq , F _θ , G _v , G _cq , G _θ : a matrix of the Taylor expansion relation.

Therefore, F _v a _{· ΔV + F cq · ΔC q} + F θ · Δθ = 0 ...... (7) G v · ΔV + G cq · ΔC q + G θ · Δθ = 0 ...... (8), in the case of tap position changes F because it is _cq = 0 (7), erases the Δθ from equation _{(8), ΔV / ΔC q = - (} G v -F θ -1 · F v · G θ) -1 · G cq ...... ( 9) From where V and θ uses a voltage approximate solution 12 (9), the voltage sensitivity coefficient obtained as elements of the matrix [Delta] V / [Delta] C _q.

In step S65, the control amount of the tap necessary to eliminate the voltage deviation is obtained using the voltage sensitivity coefficient obtained in step S64. That is, Δn = ΔV / S (10) where, Δn: tap ratio control amount required to eliminate voltage deviation ΔV: voltage deviation amount S: voltage sensitivity coefficient of tap to voltage value of monitoring node In step S66, the tap is controlled according to the tap control amount obtained in step S65. At this time, the tap ratio is determined as a discrete value by cutting up in the voltage increasing direction if the voltage is low and cutting off the voltage in the voltage decreasing direction if the voltage is excessively high.

The result of the tap control is reflected on the diagonal components of the nodes at both ends of the transformer in the node admittance matrix 10 and the transition components between the nodes.

Next, the details of the generator terminal voltage adjustment processing 7 will be described with reference to FIG.

In step S71, as in steps S51 and S61, the maximum value of the reactive power residual of each node is checked to determine whether adjustment is possible. It should be noted that if added here, the judgment value for the check is defined as an individual value instead of referring to the same value in steps S51, S61, and S71. This will be mentioned at the end of the description.

If it is determined in step S71 that adjustment is possible, steps S72 to S74 are executed for all generators.

Here, all generators are initially set to PV
It is assumed that it is defined as a designated node. In addition, swing nodes are excluded here. Step S72
Then, it is determined whether or not the generator node specifies the PV. When the step is executed for the first time as described above, the step S73 is executed because the PV is always specified.

In step S73, a generator reactive power output is obtained from the approximate voltage solution, and this is compared with the generator reactive power upper and lower limits, and the process is performed as follows.

(1) When deviating from the upper limit value The generator node is changed to be constrained by P = specified value Q = upper limit value, and node constraint condition 11 is updated.

(2) When deviating from the lower limit value The generator node is changed to be constrained by P = specified value Q = lower limit value, and node constraint condition 11 is updated.

 In each case, the specified voltage value is stored.

Thus, for the generator changed to PQ designation in step S73, in the subsequent iteration of the iterative approximation calculation,
Step S74 is executed. In step S74, the voltage approximate solution is checked, and it is determined whether the terminal voltage has recovered to the specified voltage value before changing the constraint condition in step S73,
If it has recovered, it returns to the initial PV designation and updates the node constraint condition 11 again.

As described above, the generator terminal voltage is maintained so as to maintain the original specified value as much as possible within a range where the reactive power output does not deviate from the upper and lower limits of the rating.

When the calculation is converged by a series of processes as described above, the calculation result output process 9 edits the control amount of each voltage adjusting device into a predetermined format together with the voltage absolute value, the phase angle, the branch power flow, and outputs the result. Then, the calculation according to the present embodiment ends.

Finally, a determination constant for determining whether or not adjustment is possible with the maximum reactive power residual value in steps S51, S61, and S71 will be described below.

Generally speaking, these constants are convergence determination constants, and are values for determining whether the accuracy of the solution is acceptable. However, the value is about 10 to 100 times larger than the convergence determination constant used in the convergence determination processing 8. The reason is,
This is because a convergence solution is obtained by the voltage adjustment function under the condition that the voltage reactive power imbalance is large and cannot converge. In addition, each determination constant can be given a priority to the voltage regulator depending on the magnitude of the value. For example, phase adjustment equipment group adjustment processing 5
It is obvious from the principle of the present invention that the adjustment effect of the phase adjustment equipment group becomes dominant if the determination constant in step S51 in is larger than the other two. Therefore, in the present embodiment, each determination constant is defined independently.

[Effects of the Invention] As described above, according to the present invention, the voltage is automatically adjusted under the condition that the convergence is difficult due to the voltage reactive power imbalance or the condition that the voltage value is uncertain. By adjusting the adjusting device, it is possible to calculate an appropriate voltage solution.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining one embodiment of a power flow calculation method with voltage adjustment according to the present invention, FIG. 2 is a model system diagram for performing calculations in the embodiment, and FIG. 3 is a model diagram shown in FIG. FIG. 4 is a characteristic diagram showing the relationship between the total amount of phase adjustment and the total power demand in the power system, FIG. 5 is a flowchart for explaining details of the phase adjustment equipment group adjustment processing, FIG. FIG. 6 is a flowchart for explaining the details of the transformer tap adjustment process, and FIG. 7 is a flowchart for explaining the details of the generator terminal voltage adjustment process. 1 ... Calculation condition input processing 2 ... Voltage flow calculation preprocessing 3 ... Phase equipment group control number determination processing 4 ... Iterative approximate solution calculation processing 5 ... Phase equipment group adjustment processing 6 ... Transformer tap Adjustment process 7: Generator terminal voltage adjustment process 8: Convergence determination process, 9: Calculation result output process 10: Node admittance matrix 11: Node constraint condition, 12: Approximate voltage solution

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadashi Ichikawa 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu factory (56) References JP-A-63-18928 (JP, A)

Claims (1)

(57) [Claims] 1. A connection state and an operation state of each equipment constituting a power system are inputted, and a node constraint condition and a node admittance matrix are created in a pre-processing of a voltage flow calculation, and a power consumption is calculated based on these conditions. In the voltage power flow calculation method that solves the equation using the iterative approximation calculation method with the initial solution as the starting point and obtains the magnitude and phase angle of the bus voltage of the gravity system, how much input data given as calculation conditions Determines whether there is a voltage reactive power imbalance, determines the number of control points of the phase adjustment equipment according to this amount, and the number of phase control equipment group control point determination means, and the error of the iterative approximate solution is within a certain value. When it is determined whether or not the iterative approximate solution satisfies the operational upper and lower limit value of the bus voltage, if this is not satisfied, the phase adjustment equipment group so that the voltage approximate solution satisfies the voltage allowable upper and lower limit value. Pre-input amount A phase adjustment equipment group adjusting means for adjusting the set number of control points as a limit and changing the node atom matrix, and adjusting a tap position of the transformer so as to satisfy the voltage allowable upper and lower limits. Transformer adjusting means for changing the node admittance matrix;
When the generator reactive power output obtained from the iterative approximate solution is out of the range of the generator rating, the generator bus is constrained by the reactive power output limit value so as not to deviate from the rated range. And a generator terminal voltage adjusting means for obtaining a terminal voltage which can be balanced as a reference value of the automatic voltage regulator and changing the node constraint condition.