JP7652030B2 - Voltage imbalance suppression support method and voltage imbalance suppression support device - Google Patents

Description

The present invention relates to a method for supporting voltage imbalance suppression in a three-phase power distribution system, and a device for supporting voltage imbalance suppression.

In a power distribution system, three-phase distribution lines are installed on poles in a horizontal or vertical arrangement to transmit three-phase AC power, and three-phase or single-phase AC power is supplied to electricity consumers such as ordinary homes, factories, and stores via pole-mounted transformers installed within the distribution area. The pole-mounted transformers are connected to any two of the three phases of the three-phase distribution line. Hereinafter, the single-phase portion following the pole-mounted transformer is referred to as the "single-phase load."

When multiple single-phase loads are connected to two of the three phases of a three-phase distribution line, the current imbalance increases, and the degree of three-phase voltage imbalance (hereinafter referred to as voltage imbalance) of the three-phase AC voltage increases. In order to deal with such voltage imbalance and voltage fluctuations in three-phase distribution lines, the introduction of thyristor type automatic voltage regulators (TVRs) has been progressing in recent years (for example, Patent Document 1).

Patent No. 6666109

Conventionally, automatic voltage regulators (SVRs: Step Voltage Regulators) have been installed as a countermeasure against voltage drops in power distribution systems. SVRs do not have the function of suppressing voltage imbalance because they switch the taps of all three phases at once, but the recently developed V-Y connected TVR can suppress voltage imbalance by switching the taps for two phases independently. In order to take measures to prevent voltage imbalance in a power distribution system by installing equipment, it is necessary to install the equipment in an appropriate location. However, because the optimal installation location differs depending on the power distribution system, in order to achieve efficient operation, it is necessary to derive the optimal installation position of the TVR in advance through simulation.

The present invention has been made in consideration of the above, and aims to provide a voltage imbalance suppression support method and a voltage imbalance suppression support device that can realize a simulation of suppressing voltage imbalance in a three-phase distribution line using a TVR with a V-Y connection.

In order to achieve the above object, a voltage imbalance suppression support method according to one embodiment is a voltage imbalance suppression support method that uses a power flow calculation method to perform a simulation of voltage imbalance suppression in a three-phase distribution line in accordance with an arrangement position of a thyristor-type automatic voltage regulator, the thyristor-type automatic voltage regulator comprising: a Y-connected series transformer having a secondary winding connected in series to each of a first phase, a second phase, and a third phase, a V-connected voltage regulating transformer connected in parallel between the first phase and the second phase and between the second phase and the third phase, respectively, and a thyristor-type tap changer connected to the secondary winding of the voltage regulating transformer and the primary winding of the series transformer, and the method further comprises: setting a target voltage of the first phase voltage to ground as E _a , a target voltage of the second phase voltage to ground as E _b , a target voltage of the third phase voltage to ground as E _c , an adjusted first phase voltage to ground as E _A , and an adjusted second phase voltage to ground as E _{B ,} When the adjusted third phase voltage to ground is E _C , the tap value of the voltage regulating transformer connected in parallel between the first and second phases is a _Rab , and the tap value of the voltage regulating transformer connected in parallel between the second and third phases is a _Rbc , a simulation of voltage imbalance suppression for the three-phase distribution line is performed using the following equations (1) and (2).

As a desirable mode, a simulation of suppressing voltage imbalance on the three-phase distribution line is performed assuming that the thyristor-type automatic voltage regulator is placed at one of the multiple nodes from the distribution substation to the end of the three-phase distribution line.

As a preferred embodiment, a voltage imbalance suppression simulation for the three-phase distribution line, assuming that the thyristor-type automatic voltage regulator is placed at one of the multiple nodes, is performed for all of the multiple nodes.

In order to achieve the above object, a voltage imbalance suppression support device according to one embodiment is a voltage imbalance suppression support device that uses a power flow calculation method to perform a simulation of voltage imbalance suppression on a three-phase distribution line in accordance with an arrangement position of a thyristor-type automatic voltage regulator, the thyristor-type automatic voltage regulator comprising: a Y-connected series transformer having a secondary winding connected in series to each of a first phase, a second phase, and a third phase, a V-connected voltage regulating transformer connected in parallel between the first phase and the second phase and between the second phase and the third phase, respectively, and a thyristor-type tap changer connected to the secondary winding of the voltage regulating transformer and the primary winding of the series transformer, and the device defines a target voltage of the first phase voltage to ground as E _a , a target voltage of the second phase voltage to ground as E _b , a target voltage of the third phase voltage to ground as E _c , an adjusted first phase voltage to ground as E _A , an adjusted second phase voltage to ground as E _{B ,} When the adjusted third phase voltage to ground is E _C , the tap value of the voltage regulating transformer connected in parallel between the first and second phases is a _Rab , and the tap value of the voltage regulating transformer connected in parallel between the second and third phases is a _Rbc , a simulation of voltage imbalance suppression for the three-phase distribution line is performed using the following equations (1) and (2).

In a preferred embodiment, the voltage imbalance suppression support device performs a voltage imbalance suppression simulation for the three-phase distribution line, assuming that the thyristor-type automatic voltage regulator is placed at one of multiple nodes from the distribution substation to the end of the three-phase distribution line.

In a preferred embodiment, the voltage imbalance suppression support device performs a voltage imbalance suppression simulation for the three-phase distribution line, assuming that the thyristor-type automatic voltage regulator is placed at one of the multiple nodes, for all of the multiple nodes.

In a preferred embodiment, the voltage imbalance suppression support device outputs the results of a voltage imbalance suppression simulation of the three-phase distribution line performed for all of the plurality of nodes.

The present invention provides a voltage imbalance suppression support method and a voltage imbalance suppression support device that can simulate the suppression of voltage imbalance in a three-phase distribution line using a TVR with a V-Y connection.

FIG. 1 is a diagram showing an example of a three-phase power distribution system to which a voltage imbalance suppression support method according to the present embodiment is applied. FIG. 2 is a diagram illustrating an example of a load connected to a three-phase distribution line. FIG. 3 is a diagram showing an example of a horizontal mounting. FIG. 4 is a diagram showing an example of a vertical mounting. FIG. 5 is a diagram showing an example of a double-line mounting pole (multiple-line mounting pole). FIG. 6 is a voltage vector diagram showing an example of a voltage unbalance occurring in a three-phase distribution line. FIG. 7 is a voltage vector diagram showing an example of a voltage unbalance occurring in a three-phase distribution line. FIG. 8 is a diagram showing a single-phase power distribution line modeled as a ladder circuit to explain the concept of the FBS method. FIG. 9 is a flowchart showing an example of a power flow calculation process using the FBS method. FIG. 10 is a schematic diagram illustrating an example of a TVR applied in the voltage imbalance suppression support method according to the embodiment. FIG. 11 is a voltage vector diagram showing an example of interphase voltages before and after adjustment of the TVR. FIG. 12 is a diagram illustrating an example of a functional block of a voltage imbalance suppression support device according to an embodiment. FIG. 13 is a flowchart illustrating an example of a voltage imbalance suppression support process in the voltage imbalance suppression support method according to the embodiment. FIG. 14 is a diagram showing an example of a voltage imbalance suppression simulation result. FIG. 15 is a diagram showing an example of a voltage imbalance suppression simulation result. FIG. 16 is a diagram showing an example of a voltage imbalance suppression simulation result.

The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the following modes for carrying out the invention (hereinafter, referred to as embodiments). Furthermore, the components in the following embodiments include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

Figure 1 is a diagram showing an example of a three-phase power distribution system to which the voltage imbalance suppression support method according to the present embodiment is applied. In the three-phase power distribution system 100, three-phase power is sent from a distribution transformer 200 installed in a distribution substation to a three-phase power distribution line 101. The three-phase power distribution line 101 is divided into a plurality of sections (six sections in Figure 1) at a predetermined interval X (for example, 1 km). In Figure 1, the boundaries of each section of the three-phase power distribution line 101 are nodes ND1, ND2, ND3, ND4, and ND5, respectively, and the end of the three-phase power distribution line 101 is node ND6. Hereinafter, when there is no particular distinction between the nodes ND1, ND2, ND3, ND4, ND5, and ND6, they will be referred to as nodes ND. Note that the interval X between adjacent nodes ND does not necessarily have to be equal.

The distribution transformer 200 is a device that transforms, for example, the voltage on the primary side at a predetermined transformation ratio and outputs the transformed voltage from the secondary side. The distribution transformer 200 has a transformation ratio set so that, for example, a voltage of 66 kV is transformed to a voltage of 6600 V.

The three-phase distribution line 101 is a power line for supplying power from the distribution transformer 200 to the loads 2 connected to each section, and is mounted, for example, on utility poles (not shown) arranged at predetermined intervals. The loads 2 connected to each section each include one or more single-phase loads. In the example shown in FIG. 1, three-phase power is supplied from the left end side of the three-phase distribution line 101. Hereinafter, the left end side of the three-phase distribution line 101 will also be referred to as the "upstream side," and the right end side of the three-phase distribution line 101 will also be referred to as the "downstream side."

Each section of the three-phase distribution line 101 is, for example, a vertical pole section in which the three-phase distribution lines, a, b, and c, are mounted vertically on poles, or a horizontal pole section in which the three-phase distribution lines are mounted horizontally on poles.

Figure 2 is a diagram showing an example of a load connected to a three-phase distribution line. Three-phase AC power, in which the amplitude of each line voltage is equal and the phases of the line voltages differ by 120°, is supplied from a distribution transformer 200 to three-phase distribution lines a, b, and c that make up the three-phase distribution line 101.

The pole transformer 21 is a transformer that transforms, for example, the voltage on the primary side with a predetermined transformation ratio and outputs the transformed voltage from the secondary side. The transformation ratio of the pole transformer 21 is set so that, for example, a voltage of 6600 [V] is transformed to a voltage of 100 [V] or 200 [V]. The primary side of the pole transformer 21 is connected to any two of the three-phase distribution lines a, b, and c (i.e., any two of the a-phase, b-phase, and c-phase). Figure 2 shows an example in which the primary side of the pole transformer 21 is connected to distribution line a (a-phase) and distribution line b (b-phase).

The load 22 is an electric power load provided in the three-phase power distribution system 100. The load 22 is connected to the three-phase power distribution line 101 via the pole transformer 21. The load 22 is an electric power load that operates by being supplied with electric power transformed by the pole transformer 21. The load 22 operates by being supplied with electric power of any two phases, for example, a and b phases, b and c phases, or c and a phases, via the pole transformer 21.

For ease of explanation, a three-phase power load that is different from the above-mentioned load 2 and is connected to the three-phase power distribution system 100 is omitted. A three-phase power load is a power load that is connected to all three distribution lines a, b, and c of the three-phase power distribution line 101 and operates when power from all three phases, a, b, and c, is supplied to it.

Figure 3 is a diagram showing an example of a horizontal pole mounting. In a horizontal pole mounting, as shown in Figure 3, the a-phase, b-phase, and c-phase distribution lines of a three-phase distribution line 101 are mounted horizontally relative to the ground.

Figure 4 shows an example of a vertical pole mounting. In a vertical pole mounting, the a-phase, b-phase, and c-phase distribution lines of the three-phase distribution line 101 are mounted vertically to the ground as shown in Figure 3.

Figure 5 is a diagram showing an example of a double-circuit pole (multiple-circuit pole). In a double-circuit pole (multiple-circuit pole), multiple three-phase distribution lines 101 are laid in parallel, and the a-phase, b-phase, and c-phase distribution lines of the three-phase distribution lines 101 are mounted horizontally or vertically.

Next, we will explain the voltage imbalance in the three-phase power distribution system 100. In the three-phase power distribution system 100, there are two factors that cause voltage imbalance: asymmetry of phase arrangement and imbalance of load distribution. Here, "phase arrangement" refers to the positional relationship of each distribution line a, b, c of the three-phase power distribution line 101, and "voltage imbalance due to asymmetry of phase arrangement" refers to voltage imbalance caused by the mutual impedance between lines becoming asymmetric due to the arrangement of distribution lines a, b, c in a horizontal pole or vertical pole, or the influence of distribution lines of other lines in a two-circuit pole (multi-circuit pole). In addition, "load distribution" refers to the distribution of load capacity for each connection phase, and "voltage imbalance due to imbalance of load distribution" refers to voltage imbalance caused by imbalance of the total capacity of single-phase loads connected to each connection phase. In the following explanation, there is no distinction between voltage imbalance caused by asymmetric phase arrangement and voltage imbalance caused by imbalance in load distribution, and they are simply referred to as "voltage imbalance."

Here, we will first use Figures 6 and 7 to explain the voltage unbalance that occurs in the three-phase distribution line 101. Figures 6 and 7 are voltage vector diagrams showing an example of a voltage unbalance that occurs in a three-phase distribution line. Figure 6 shows the phase voltages of distribution lines a, b, and c. Figure 7 shows the interphase voltages of distribution lines a, b, and c.

6 and 7, the horizontal axis indicates the real axis Re, and the vertical axis indicates the imaginary axis Im. Here, the explanation will be made using the symmetric coordinate method. The positive-phase voltage of the three-phase distribution line 101 can be expressed by the following equation (2) using the voltage vectors of the a-phase, b-phase, and c-phase, and the vector operator shown in the following equation (1). The negative-phase voltage of the three-phase distribution line 101 can be expressed by the following equation (3) using the voltage vectors of the a-phase, b-phase, and c-phase, and the vector operator shown in the following equation (1).

The voltage unbalance rate ε of the three-phase distribution line 101 can be expressed as the ratio of the positive-phase voltage to the negative-phase voltage of the three-phase distribution line 101, as shown in the following equation (4).

The voltage unbalance rate ε of the three-phase distribution line 101 can be expressed by the following equations (5) to (8) using the interphase voltages of the distribution lines a, b, and c.

In this disclosure, for example, in the three-phase power distribution system 100 shown in FIG. 1, a simulation is performed in which thyristor type step voltage regulators (TVRs, hereinafter also simply referred to as "TVRs") are placed at each node ND1, ND2, ND3, ND4, ND5, and ND6, and a voltage imbalance suppression simulation is performed for the three-phase power distribution system 100 using the FBS (Forward/Backward Sweep) method (or the BSF (Backward/Forward Sweep) method, which will be unified as the "FBS method" in this disclosure), which is one of the power flow calculation methods in power systems. Here, for ease of explanation, the concept of the FBS method will first be explained using a single-phase power distribution line as an example.

Figure 8 shows a ladder circuit model of a single-phase power distribution line to explain the concept of the FBS method. Figure 9 is a flowchart showing an example of a power flow calculation process using the FBS method.

In Fig. 8, node ND ₁ indicates the sending point of a distribution substation. The sending voltage _Vs of the distribution substation at node ND ₁ is set to 6600 [V]. Also, in Fig. 8, node ND _N indicates the end of a single-phase distribution line. _{Z n,n+1} indicates a known inter-node impedance of the single-phase distribution line. S _n indicates a known load (P _n [kW], Q _n [kVar]) connected to the single-phase distribution line.

In FIG. 8, the load current I _n and voltage V _n at an arbitrary node ND _n , and the currents I _{n-1 and n} at nodes ND _{n-1 and} n are respectively expressed by the following equations (9), (10), and (11).

In the FBS method, first, the voltage (=V _n+1 ) at an arbitrary node ND _n+1 is initialized to a target voltage of 6600 [V] (step S11), and the above equations (9), (10), and (11) are executed for the node ND _n (step S12).

Thereafter, the above formulas (9), (10), and (11) are repeatedly executed up to node ND _2. Specifically, after step S12, n is decremented (step S13), and it is determined whether n has become 2 (step S14).

If n is greater than 2 (step S14; No), return to step S12 and repeat the process up to step S14.

When n becomes 2 (step S14; Yes), the current I _n-1,n calculated in the above formula (10) is then used to execute the following formula (12) up to the node ND _N (step S15).

Thereafter, the above formula (12) is repeatedly executed up to the node ND - _{- N.} Specifically, after step S15, n is incremented (step S16), and it is determined whether n has become N+1 (step S17).

If n is equal to or less than N (step S17; No), return to step S15 and repeat the process up to step S17.

When n becomes N+1 (step S17; Yes), the difference |V _s -V ₁ | between the distribution substation's sending voltage V _s and the voltage V ₁ at node ND ₁ is calculated (step S18), and it is determined whether the difference |V _s -V ₁ | is less than or equal to a predetermined value α (step S19).

If the difference |V _s -V ₁ | is greater than the predetermined value α (step S19; No), the process returns to step S12, and the processes up to step S19 are repeatedly executed.

When the difference |V _s -V ₁ | becomes equal to or smaller than the predetermined value α (step S19; Yes), the power flow calculation process ends.

The above-described power flow calculation process allows a voltage simulation of the single-phase power distribution line shown in FIG. 8 to be performed. Note that, although a single-phase power distribution line has been described as an example here, a voltage simulation can also be performed using a similar concept in the three-phase power distribution system 100.

In this disclosure, for example, in the three-phase power distribution system 100 shown in FIG. 1, it is assumed that a TVR is placed at any one of the nodes ND1, ND2, ND3, ND4, ND5, and ND6, and a voltage imbalance suppression simulation for the three-phase power distribution system 100 is performed using the above-mentioned FBS method. Here, an overview of the TVR (thyristor-type automatic voltage regulator) applied to the three-phase power distribution system 100 will be described with reference to FIG. 10.

Figure 10 is a schematic diagram showing an example of a TVR applied in the voltage imbalance suppression support method according to the embodiment. As shown in Figure 10, this embodiment targets a TVR3 with a so-called V-Y connection, in which the upstream side is a Y connection and the downstream side is a V connection.

The TVR3 includes series transformers 31A, 31B, and 31C with a Y connection that connects secondary windings in series to each phase of the three-phase power distribution system 100, voltage regulating transformers 32ab and 32bc with a V connection that are connected in parallel between each phase of the three-phase power distribution system 100, and a thyristor tap changer 33 that is connected to the secondary windings of the voltage regulating transformers 32ab and 32bc and the primary windings of the series transformers 31A, 31B, and 31C.

The thyristor tap changer 33 includes multiple thyristors (not shown). When the voltage of the distribution line fluctuates due to load fluctuations, the thyristor tap changer 33 performs tap switching of each thyristor so as to reduce the difference between the primary voltage of the distribution line and the reference voltage.

10, the thyristor tap changer 33 controls the ab-phase interphase voltage and the bc-phase interphase voltage separately. As a result, the V-Y connected TVR 3 can suppress voltage imbalance in the three-phase power distribution system 100. If the voltages between the phases are V _ab , V _bc , and V _ca , respectively, the vector calculation formula for the adjusted interphase voltages V _AB , V _BC , and V _CA is given by the following formula (13).

In the above formula (13), a _Rab represents the tap value of the voltage regulating transformer 32ab, and a _Rbc represents the tap value of the voltage regulating transformer 32bc.

In the above-mentioned voltage simulation, the power flow calculation process is performed using the voltage to ground, i.e., the voltages of each phase. The voltages V _ab , V _bc , and V _ca between each phase are expressed by the following equation (14) using the reference voltages E _a , E _b , and E _c that are the target voltages of each phase (e.g., 6600 V).

Moreover, the adjusted phase voltages E _A ', E _B ', and E _C ' are expressed by the following equation (15).

From the above equations (14) and (15), the following equation (16) is derived.

The V-Y connected TVR3 shown in Figure 10 has the characteristic that the zero-phase voltage does not change before and after adjustment. In the above equation (16), the neutral point information is lost. For this reason, it is necessary to add a correction term to the above equation (16) to set the zero-phase voltage to "0" and to prevent the neutral point voltage from changing. Figure 11 is a voltage vector diagram showing an example of the interphase voltages before and after TVR adjustment.

The zero-phase voltage of the three-phase distribution line 101 is expressed by the following equation (17) using the symmetric coordinate method described with reference to Figures 6 and 7.

Therefore, the vector calculation equation for each phase voltage _EA , _EB , and _EC after adjustment is given by the following equation (18) by adding the correction term for the zero-phase voltage shown in the above equation (17) to the above equation (16).

On the other hand, the vector calculation equation for the adjusted phase currents I _A ', I _B ', and I _C ' is given by the following equation (19).

Similarly, in the above formula (19), the neutral point information is lost. Therefore, it is necessary to add a correction term to the above formula (19) to set the zero-phase current to "0" and to prevent the neutral point voltage from changing. Therefore, the vector calculation formula for each phase current I _A , I _B , and I _C after adjustment is the following formula (20) which adds a correction term for the zero-phase current to the above formula (19).

Here, we will explain a specific example of the voltage imbalance suppression support process for the three-phase power distribution system 100, assuming that the TVR3 shown in FIG. 10 is placed at each of the nodes ND1, ND2, ND3, ND4, ND5, and ND6 of the three-phase power distribution system 100 shown in FIG. 1.

Figure 12 is a diagram showing an example of a functional block of a voltage imbalance suppression support device according to an embodiment. As shown in Figure 12, the voltage imbalance suppression support device 1 according to this embodiment has, for example, an input unit 11, an output unit 12, a display unit 13, a memory unit 14, a connection phase determination unit 15, and a control unit 16.

The input unit 11 is, for example, a keyboard for inputting information to the voltage imbalance suppression support device 1.

The output unit 12 is, for example, a printer for outputting information to the outside of the voltage imbalance suppression support device 1.

The display unit 13 is, for example, a monitor for displaying information input to the voltage imbalance suppression support device 1 and information output from the voltage imbalance suppression support device 1.

The memory unit 14 is, for example, a ROM (Read Only Memory), a hard disk drive, or a flash memory, or a combination of these.

The storage unit 14 stores, for example, a program for operating the voltage imbalance suppression support device 1. The storage unit 14 further stores, for example, a program for performing voltage imbalance suppression support processing (hereinafter also referred to as the "voltage imbalance suppression support processing program").

In addition, the memory unit 14 stores various types of information related to the three-phase power distribution system 100 in advance. The various types of information related to the three-phase power distribution system 100 include, for example, known node-to-node impedances of the three-phase power distribution line 101 and known loads connected to the three-phase power distribution line 101. The memory unit 14 also has a function of storing various types of data calculated in the voltage imbalance suppression support process.

The processing unit 15 performs voltage imbalance suppression support processing based on various information about the three-phase power distribution system 100 stored in the memory unit 14.

The control unit 16 controls the operation of the voltage imbalance suppression support device 1 based on, for example, a program for operating the voltage imbalance suppression support device 1, which is stored in the memory unit 14. In addition, the control unit 16 starts the voltage imbalance suppression support processing program, and the processing unit 15 executes the voltage imbalance suppression support processing.

The processing unit 15 and the control unit 16 can be configured, for example, by combining a CPU (Central Processing Unit) and memory.

Figure 13 is a flowchart showing an example of a voltage imbalance suppression support process in a voltage imbalance suppression support method according to an embodiment.

When the voltage imbalance suppression support processing program is started by the operator of the voltage imbalance suppression support device 1, the processing unit 15 reads various information related to the three-phase power distribution system 100 stored in the memory unit 14 and executes the voltage imbalance suppression support processing shown in FIG. 13.

The processing unit 15 performs a voltage imbalance suppression simulation assuming that the TVR 3 is placed at an arbitrary node NDn (for example, node ND1) of the three-phase power distribution system 100. Specifically, the processing unit 15 assumes that the TVR 3 is placed at the node NDn, and sets the target voltages (respective phase reference voltages E _a , E _b , E _c ) of the respective phases at the node NDn to, for example, 6600 [V] (step S1). Then, the processing unit 15 calculates the respective phase voltages E _A , E _B , and E _C after adjustment using the above-mentioned formulas (16) and (17), and calculates the respective phase currents I _A , I _B , and I _C after adjustment using the above-mentioned formulas (19) and (20) (step S2). The processing of steps S1 and S2 corresponds to the initial setting (step S11) of the power flow calculation processing shown in FIG. 9.

The processing unit 15 executes a power flow calculation process (see FIG. 9) for each phase using the phase voltages _EA , _EB , and _EC and the phase currents _IA , _IB , and _IC calculated in step S2 (step S3).

The data calculated in the power flow calculation process is stored in the memory unit 14 as appropriate. Then, the processing unit 15 calculates the voltage unbalance rate εx for each node NDx using the above equations (1) to (8) based on the data stored in the memory unit 14 (voltage unbalance rate calculation process) and stores it in the memory unit 14 (step S4).

The processing unit 15 determines whether or not the voltage imbalance suppression simulation (power flow calculation process (step S3) and voltage imbalance rate calculation process (step S4)) assuming placement of TVR3 at all nodes NDx has been completed (step S5). If the voltage imbalance suppression simulation assuming placement of TVR3 at all nodes NDx has not been completed (step S5; No), the processing unit 15 returns to step S1 and repeatedly executes the processes from step S1 to step S5 until the voltage imbalance suppression simulation assuming placement of TVR3 at all nodes NDx has been completed.

When the voltage imbalance suppression simulation assuming placement of TVR3 at all nodes NDx is completed (step S5; Yes), the processing unit 15 generates charts, for example, as shown in Figures 14, 15, and 16, from the various data stored in each node memory unit 14, and performs output processing, such as displaying the charts on the display unit 13 or outputting the charts from the output unit 12 as the voltage imbalance suppression simulation results (step S6), and terminates the voltage imbalance suppression support processing.

Figures 14, 15, and 16 show examples of the results of a voltage imbalance suppression simulation.

In Fig. 14 and Fig. 15, the horizontal axis indicates the relative distance of each node ND to the distribution substation of the three-phase power distribution system 100 shown in Fig. 1, and the vertical axis indicates the line voltage. Fig. 14 shows a simulation result of the line voltage when it is assumed that a TVR 3 is placed at the node ND2 of the three-phase power distribution system 100 shown in Fig. 1. Fig. 15 shows a simulation result of the line voltage when a TVR 3 is not placed at any of the nodes ND of the three-phase power distribution system 100 shown in Fig. 1. In Fig. 14 and Fig. 15, the solid line indicates the line voltage _Vbc , the dashed line indicates the line voltage _Vca , and the dashed line indicates the line voltage _Vab .

In FIG. 16, the horizontal axis indicates the relative distance of each node ND to the distribution substation of the three-phase power distribution system 100 shown in FIG. 1, and the vertical axis indicates the voltage unbalance rate. In FIG. 16, the solid line indicates the simulation result of the voltage unbalance rate when it is assumed that a TVR3 is placed at node ND2 of the three-phase power distribution system 100 shown in FIG. 1, and the dashed line indicates the simulation result of the voltage unbalance rate when a TVR3 is not placed at any node ND of the three-phase power distribution system 100 shown in FIG. 1.

As shown in Fig. 14 and Fig. 16, voltage imbalance is suppressed at node ND2 where TVR3 is assumed to be placed. As a result, as shown in Fig. 16, it can be seen that the voltage imbalance rate of node ND2 where the voltage imbalance rate is maximum when TVR3 is placed at node ND2 is half or less (approximately 0.7% or less in the example shown in Fig. 16) of the voltage imbalance rate of node ND6 where the voltage imbalance rate is maximum when TVR3 is not placed at any node ND in the three-phase power distribution system 100 (approximately 1.4% in the example shown in Fig. 16).

14 and 15, it can be seen that the variations in the line voltages V ab , V bc , and V ca at the end of the three-phase distribution line 101 (node ND6 in the example shown in FIG. 1) when it is assumed that the TVR 3 is placed at node ND2 are smaller than the variations in the line voltages _{V ab ,} V _bc , _and V _ca at the end of the three-phase distribution line 101 (node ND6 in this case) when no TVR 3 is placed at any node ND in the three- _phase distribution system 100. This makes it possible to increase the control margin for the voltage control value (95 [V] to 105 [V]) when converted to 100 [V], for example.

In the above example, in order to simplify the chart, FIG. 14 shows the simulation result of the line voltage when it is assumed that the TVR3 is placed at node ND2 of the three-phase power distribution system 100, and FIG. 15 shows the simulation result of the line voltage when the TVR3 is not placed at any node ND. However, for example, the simulation result of the line voltage when it is assumed that the TVR3 is placed at node ND2 of the three-phase power distribution system 100 shown in FIG. 14 and the simulation result of the line voltage when the TVR3 is not placed at any node ND shown in FIG. 15 may be displayed superimposed on the display unit 13 or output from the output unit 12. This makes it easy to compare the presence and absence of the TVR3. Also, FIG. 14, FIG. 15, and FIG. 16 may be displayed superimposed on each other, or may be output from the output unit 12. This improves the visibility of the simulation results.

Note that, here, FIG. 14 shows an example of a chart showing the results of a simulation of line voltages when it is assumed that a TVR3 is placed at node ND2 of the three-phase power distribution system 100 shown in FIG. 1. In the voltage imbalance suppression support process described above, the processing unit 15 generates charts, for example, as shown in FIG. 14 and FIG. 16, as the results of a voltage imbalance suppression simulation when it is assumed that a TVR3 is placed at all nodes NDx, and performs output processing such as displaying the charts on the display unit 13 or outputting the charts from the output unit 12. This makes it possible to consider the locations (nodes ND) where the TVR3 is placed in the actual three-phase power distribution system 100.

The form of the chart generated as the result of the voltage imbalance suppression simulation is not limited to the forms shown in Figs. 14, 15, and 16. For example, the form may include more data than is calculated in the power flow calculation process, or a threshold value may be set for the voltage imbalance rate, and a chart may be generated that can determine whether the voltage imbalance rate at each node ND has cleared the threshold value by the voltage imbalance suppression simulation described above.

As described above, the voltage imbalance suppression support method according to this embodiment uses a power flow calculation method to perform a voltage imbalance suppression simulation of a three-phase distribution line 101 according to the arrangement position of the V-Y connected TVR3, and performs a voltage simulation with a correction term added to prevent the neutral point voltage from changing, using the target voltage E _a for the a-phase voltage to ground of TVR3, the target voltage _{E b for} the b-phase voltage to ground, the target voltage E _c for the c-phase voltage to ground, the adjusted a-phase voltage to ground E _A , the adjusted b-phase voltage to ground E _B , the adjusted c-phase voltage to ground E C, the tap value a _Rab of the voltage regulating transformer 32 ab connected in parallel between the a-phase and b-phase, and the tap value a _Rbc of the voltage regulating transformer 32 bc connected in parallel between the b-phase and c-phase.

This makes it possible to realize a voltage imbalance suppression simulation for a three-phase distribution line 101 using a V-Y connected TVR3.

In addition, the voltage imbalance suppression support method according to this embodiment performs a voltage imbalance suppression simulation for the three-phase distribution line 101, assuming that a TVR3 is placed at one node NDn among multiple nodes NDx from the distribution substation to the end of the three-phase distribution line 101.

More specifically, a voltage imbalance suppression simulation for a three-phase distribution line 101, assuming that a TVR3 is placed at one of the multiple nodes NDx, is performed for all of the multiple nodes NDx.

Furthermore, when the voltage imbalance suppression support device 1 of this embodiment uses a power flow calculation method to perform a voltage imbalance suppression simulation of a three-phase distribution line 101 according to the arrangement position of the V-Y connected TVR3, it performs a voltage simulation with a correction term added to prevent the neutral point voltage from changing, using the target voltage E _a for the a-phase voltage to ground of TVR3, the target voltage _{E b for} the b-phase voltage to ground, the target voltage E _c for the c-phase voltage to ground, the adjusted a-phase voltage to ground E _A , the adjusted b-phase voltage to ground E _B , the adjusted c-phase voltage to ground E C, the tap value a _Rab of the voltage regulating transformer 32 ab connected in parallel between the a-phase and b-phase, and the tap value a _Rbc of the voltage regulating transformer 32 bc connected in parallel between the b-phase and c-phase.

This makes it possible to realize a voltage imbalance suppression simulation for a three-phase distribution line 101 using a V-Y connected TVR3.

The voltage imbalance suppression support device 1 according to this embodiment performs a voltage imbalance suppression simulation for the three-phase distribution line 101, assuming that a TVR3 is placed at one node NDn among multiple nodes NDx from the distribution substation to the end of the three-phase distribution line 101.

More specifically, a voltage imbalance suppression simulation for a three-phase distribution line 101, assuming that a TVR3 is placed at one of the multiple nodes NDx, is performed for all of the multiple nodes NDx.

Then, the voltage imbalance suppression support device 1 outputs the results of the voltage imbalance suppression simulation of the three-phase distribution line 101 performed for all of the multiple nodes NDx.

This makes it possible to consider the location (node ND) where the TVR3 should be placed in an actual three-phase power distribution system 100.

1 Voltage imbalance suppression support device 2 Load 3 TVR (thyristor type automatic voltage regulator)
REFERENCE SIGNS LIST 11 Input section 12 Output section 13 Display section 14 Memory section 15 Connection phase determination section 16 Control section 21 Pole transformer 22 Loads 31A, 31B, 31C Series transformers 32ab, 32bc Voltage regulating transformer 33 Thyristor tap changer 100 Three-phase power distribution system 101 Three-phase power distribution line 200 Power distribution transformer

Claims (7)

A voltage imbalance suppression support method for performing a voltage imbalance suppression simulation of a three-phase distribution line according to an arrangement position of a thyristor-type automatic voltage regulator using a power flow calculation method, comprising:
The thyristor type automatic voltage regulator comprises:
a series transformer having a Y connection in which a secondary winding is connected in series to each of the first phase, the second phase, and the third phase;
a V-connection voltage adjusting transformer connected in parallel between the first phase and the second phase and between the second phase and the third phase, respectively;
a thyristor tap changer connected to a secondary winding of the voltage regulating transformer and a primary winding of the series transformer;
Equipped with
A simulation of voltage imbalance suppression for the three-phase power distribution line is performed using the following equations (1 ₎ and (2 ₎ , where the target voltage of the first phase voltage to ground is _Ea , the target voltage of the second phase voltage to ground is _Eb , the target voltage of the third phase voltage to ground is _Ec , the adjusted first phase voltage to ground is _EA , the adjusted second phase voltage to ground is _EB , the adjusted third phase voltage to ground is EC, the tap value of the voltage regulating transformer connected in parallel between the first and second phases is _aRab , and the tap value of the voltage regulating transformer connected in parallel between the second and third phases is aRbc:
Voltage imbalance suppression assistance method.

A voltage imbalance suppression simulation for the three-phase distribution line is performed on the assumption that the thyristor-type automatic voltage regulator is disposed at one of a plurality of nodes from a distribution substation to a terminal of the three-phase distribution line.
The voltage imbalance suppression support method according to claim 1 . performing a voltage imbalance suppression simulation for the three-phase distribution line, assuming that the thyristor-type automatic voltage regulator is disposed at one of the plurality of nodes, for all of the plurality of nodes;
The voltage imbalance suppression support method according to claim 2 . A voltage imbalance suppression support device that performs a voltage imbalance suppression simulation of a three-phase distribution line according to the arrangement position of a thyristor-type automatic voltage regulator using a power flow calculation method,
The thyristor type automatic voltage regulator comprises:
a series transformer having a Y connection in which a secondary winding is connected in series to each of the first phase, the second phase, and the third phase;
a V-connection voltage adjusting transformer connected in parallel between the first phase and the second phase and between the second phase and the third phase, respectively;
a thyristor tap changer connected to a secondary winding of the voltage regulating transformer and a primary winding of the series transformer;
Equipped with
The voltage imbalance suppression support device is
A simulation of voltage imbalance suppression for the three-phase power distribution line is performed using the following equations (1 ₎ and (2 ₎ , where the target voltage of the first phase voltage to ground is _Ea , the target voltage of the second phase voltage to ground is _Eb , the target voltage of the third phase voltage to ground is _Ec , the adjusted first phase voltage to ground is _EA , the adjusted second phase voltage to ground is _EB , the adjusted third phase voltage to ground is EC, the tap value of the voltage regulating transformer connected in parallel between the first and second phases is _aRab , and the tap value of the voltage regulating transformer connected in parallel between the second and third phases is aRbc:
Voltage imbalance suppression support device.

The voltage imbalance suppression support device is
A simulation of voltage imbalance suppression for the three-phase distribution line is performed on the assumption that the thyristor-type automatic voltage regulator is disposed at one of a plurality of nodes from a distribution substation to a terminal of the three-phase distribution line.
The voltage imbalance suppression assist device according to claim 4. The voltage imbalance suppression support device is
performing a voltage imbalance suppression simulation for the three-phase distribution line, assuming that the thyristor-type automatic voltage regulator is disposed at one of the plurality of nodes, for all of the plurality of nodes;
The voltage imbalance suppression support device according to claim 5. The voltage imbalance suppression support device is
outputting a result of the voltage imbalance suppression simulation of the three-phase distribution line performed for all of the plurality of nodes;
The voltage imbalance suppression assist device according to claim 6.

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