JP2014150694A - Voltage adjustment system and voltage adjustment method for power distribution system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently perform voltage management of each line voltage and correction of voltage unbalance, in a three-phase power distribution line.SOLUTION: A voltage adjustment system comprises: a voltage unbalance rate improvement device 21 which determines whether or not a voltage unbalance rate of three-phase line voltages at a control target point is larger than a predetermined reference value, boosts or drops line voltage selected from the three-phase line voltages after the lapse of first predetermined time when it is determined that the voltage unbalance rate is larger than the reference value, and performs adjustment so that the voltage unbalance rate at the control target point becomes equal to or smaller than the reference value; and a voltage adjustment device 22 which determines whether or not any of the three-phase line voltages at the control target point is out of a voltage management width, and performs adjustment so that the three-phase line voltages become within the voltage management width by boosting or dropping the three-phase line voltages in a lump after the lapse of second predetermined time longer than the first predetermined time when it is determined that some of the three-phase line voltages is out of the voltage management width.

Description

  The present invention relates to a voltage adjustment system and a voltage adjustment method for a distribution system, and in particular, management of line voltages appearing between three-phase lines (hereinafter simply referred to as “line voltage”) and voltage imbalance (hereinafter, referred to as “line voltage”). The present invention relates to a voltage adjustment system and a voltage adjustment method for a power distribution system that simply improve (also referred to as “unbalance”).

  In recent years, distributed power sources such as a photovoltaic power generation (PV) system for home use are becoming widespread and are expected to contribute to the maintenance of the global environment. However, when this distributed power source is connected to a distribution system, the demand and supply flow of power may be locally reversed to cause a reverse power flow in the distribution system.

  On the other hand, in the power distribution system, a voltage drop in a forward power flow is assumed, and the supply side voltage is set high in advance so as to compensate for the voltage drop. However, when a reverse power flow occurs, the assumed voltage drop disappears, and the voltage at the point where the distributed power source is connected to the power distribution system rises locally.

  This local voltage increase may spread to the surrounding area and increase the line voltage in the middle of the distribution system. When the degree of increase of the line voltage deviates from the specified tolerance, it causes various troubles. For this reason, the voltage adjustment apparatus is provided so that it may intervene in the feeder between the power transmission point in a distribution system, and a customer's power receiving point. The voltage regulator controls the voltage of the power distribution system so that the received voltage at the power receiving point of the customer is within the specified allowable range regardless of how the voltage of the power distribution system changes in the step-up and step-down directions. ing.

  The voltage management of the distribution system using the conventional voltage regulator is performed based on the line voltage value. Specifically, voltage control is performed so that the line voltage at the control target point in the distribution system is within the reference voltage ± allowable width. In addition, a control target point is arbitrarily set according to the load conditions etc. in a power distribution system. For such voltage adjustment of the distribution line, a load ratio control transformer (LRT) or automatic voltage regulator (SVR) is suitable.

  In general, the line voltage of the distribution system is voltage-controlled on the premise that it is balanced in three phases (hereinafter simply referred to as “three-phase balanced”). For this reason, the three phases are adjusted with a uniform control direction and a uniform control amount for any control element of the voltage step-up / step-down direction and the control amount. That is, control is performed in which the voltages of the respective phases are simultaneously adjusted in the same direction in the same direction of step-up or step-down (hereinafter referred to as “three-phase collective control”) (for example, see Patent Document 1).

JP 2009-177868 A

  However, when a distributed power source having the properties of a single-phase load or a single-phase load is biased and connected to any one of the three phases, the three-phase voltage becomes unbalanced. When an unbalance occurs in the three-phase line current, an unbalance also occurs in the line voltage. When the unbalance exceeds the limit, the power reception voltage at the power reception point of the consumer deviates from the allowable range, and as a result, there is a possibility that a failure such as adversely affecting the customer's equipment may occur. Therefore, a voltage regulator and a voltage regulation method for a distribution line that can satisfy both the maintenance of three-phase balance and the voltage management are desired.

  On the other hand, in the conventional voltage regulator as disclosed in Patent Document 1, when three-phase collective control is performed even though the three-phase voltage is unbalanced, the three voltage output from the voltage regulator is used. The voltage of the phase is adjusted in the same ratio for all phases. Therefore, in the conventional voltage regulator, if the three-phase voltage before adjustment is in an unbalanced state, the unbalanced state is maintained even after adjustment, and the three-phase voltage unbalance cannot be eliminated.

  For example, when a certain line voltage deviates from the allowable range and is extremely high (low), in order to keep it within the allowable range, the three-phase collective control in the descending (rising) direction is performed. The other line voltage may be low (high) from the allowable range. Thus, in the three-phase collective control, when the voltage unbalance of the distribution system is large, the improvement effect on the voltage unbalance is limited.

  The present invention has been made to solve the above-described problems, and by performing voltage control for a three-phase package after improving the voltage imbalance rate of the line voltage of the three-phase distribution line at the control target point. An object of the present invention is to provide a voltage adjustment system and a voltage adjustment method for a distribution system capable of efficiently accommodating all line voltages of a three-phase distribution line within a predetermined voltage management width.

  The voltage adjustment system of the distribution system of the distribution line according to the present invention adjusts the magnitude of the three-phase line voltage appearing between the lines of the three-phase distribution line at the control target point, and controls the line voltage as a predetermined voltage management. A voltage regulation system within a range, wherein it is determined whether a voltage unbalance rate of the three-phase line voltage at the control target point is larger than a predetermined reference value, and the voltage unbalance rate is If it is determined that the value is greater than the reference value, the line voltage selected from the three-phase line voltage is stepped down or stepped up after the first predetermined time has elapsed, thereby A voltage imbalance rate improving apparatus that adjusts the voltage imbalance rate to be equal to or less than the reference value, and whether any of the three-phase line voltages at the control target point is out of the voltage management range. The voltage management width in the three-phase line voltage If it is determined that there is an error, the voltage management width is reduced by stepping up or stepping up the three-phase line voltage collectively after a second predetermined time longer than the first predetermined time. And a voltage adjusting device that performs adjustment to fit in

  According to this voltage adjustment system, by controlling the voltage adjustment device that performs voltage control of the three-phase batch and the voltage imbalance rate improvement device that improves the voltage imbalance rate at the control target point, It is possible to correct the imbalance of the three-phase voltage appearing between the lines, and to perform voltage management that keeps the voltage within the reference voltage ± allowable width.

  In this voltage adjustment system, the voltage imbalance rate improving apparatus calculates a voltage imbalance rate calculating unit that calculates the voltage imbalance rate, and a voltage that determines whether the voltage imbalance rate is equal to or less than the reference value. On the condition that the voltage unbalance rate is determined to be greater than the reference value by the unbalance rate determination unit and the voltage unbalance rate determination unit, the maximum of the three-phase line voltages A line voltage selection unit for selecting a line voltage, and a voltage unbalance rate adjustment for stepping down the maximum line voltage selected by the line voltage selection unit and keeping the voltage unbalance rate below the reference value May be provided.

  According to this voltage regulation system, it is possible to efficiently correct voltage imbalance in a distribution environment where three-phase voltage imbalance is likely to occur due to the spread of distributed power sources such as household photovoltaic power generation systems. Can do.

  In this voltage adjustment system, the voltage imbalance rate improving apparatus calculates a voltage imbalance rate calculating unit that calculates the voltage imbalance rate, and a voltage that determines whether the voltage imbalance rate is equal to or less than the reference value. On the condition that the voltage unbalance rate is determined to be greater than the reference value by the unbalance rate determination unit and the voltage unbalance rate determination unit, the minimum of the three-phase line voltages A line voltage selection unit that selects a line voltage, and a voltage unbalance rate adjustment that boosts the minimum line voltage selected by the line voltage selection unit and keeps the voltage unbalance rate below the reference value. May be provided.

  According to this voltage regulation system, it is possible to efficiently correct voltage imbalance in a distribution environment where three-phase voltage imbalance is likely to occur due to the spread of distributed power sources such as household photovoltaic power generation systems. Can do.

  In this voltage regulation system, the voltage regulation device includes a line voltage measurement unit that measures each of the three-phase line voltages at the control target point, and the voltage imbalance rate is equal to or less than the reference value. As a condition, a line voltage determination unit that determines whether or not any of the three-phase line voltages measured by the line voltage measurement unit is out of the voltage management range; and a line voltage Three-phase batch voltage conversion that collectively lowers or boosts the three-phase line voltage when it is determined by the determination unit that any of the three-phase line voltages is out of the voltage management range. May be provided.

  According to this voltage regulation system, all line voltages can be efficiently kept within a predetermined voltage management range by performing three-phase voltage control only when the voltage imbalance rate is below the reference value. it can.

  In this voltage regulation system, the voltage regulator may step down or step up the three-phase line voltage at step intervals of the same change width.

  According to this voltage regulation system, efficient voltage management can be performed by controlling the step-up / step-down of the line voltage at step intervals of the same change width.

  In this voltage regulation system, the voltage management width may be set by reference voltage ± allowable width.

  According to this voltage adjustment system, the voltage management can be reliably performed by setting the voltage management width by the reference voltage ± allowable width.

  Further, the voltage adjustment method for the distribution system according to the present invention adjusts the magnitude of the three-phase line voltage appearing between the lines of the three-phase distribution line at the control target point, and sets the line voltage to a predetermined voltage management width. The voltage unbalance rate of the three-phase line voltage at the control target point is determined to be greater than a predetermined reference value, and the voltage unbalance rate is If it is determined that the voltage is greater than the value, the line voltage selected from the three-phase line voltage is stepped down or stepped up after the first predetermined time has elapsed, and thereby the voltage at the control target point is increased. Whether or not there is a voltage unbalance rate improvement stage for adjusting the unbalance rate to be equal to or less than the reference value, and any of the three-phase line voltages at the control target point is out of the voltage management range. Deviating from the voltage management width in the three-phase line voltage When it is determined that there is an object, adjustment is performed so that the three-phase line voltage is collectively reduced or boosted within the voltage management width after a second predetermined time longer than the first predetermined time has elapsed. And a voltage adjustment stage.

  According to this voltage adjustment method, by controlling the voltage adjustment stage for performing voltage control for the three-phase batch and the voltage imbalance ratio improvement stage for improving the voltage imbalance ratio at the control target point, It is possible to correct the imbalance of the three-phase voltage appearing between the lines, and to perform voltage management that keeps the voltage within the reference voltage ± allowable width.

  In this voltage adjustment method, the voltage unbalance rate improvement step calculates the voltage unbalance rate, and determines whether the voltage unbalance rate is equal to or lower than the reference value. On the condition that the voltage unbalance rate is determined to be greater than the reference value by the unbalance rate determination step and the voltage unbalance rate determination step, the maximum of the three-phase line voltages is determined. Line voltage selection stage for selecting line voltage, and voltage unbalance ratio adjustment for stepping down the maximum line voltage selected in the line voltage selection stage to keep the voltage unbalance ratio below the reference value And a stage.

  According to this voltage adjustment method, voltage disequilibrium can be corrected efficiently in a distribution environment where three-phase voltage imbalance is likely to occur due to the spread of distributed power sources such as household photovoltaic power generation systems. Can do.

  In this voltage adjustment method, the voltage unbalance rate improvement step includes a voltage unbalance rate step for calculating the voltage unbalance rate, and a voltage unbalance for determining whether the voltage unbalance rate is equal to or less than the reference value. The minimum line in the three-phase line voltage is determined on the condition that the voltage unbalance rate is determined to be greater than the reference value by the balance ratio determination step and the voltage unbalance rate determination step. A line voltage selection stage for selecting a line voltage, and a voltage unbalance ratio adjustment stage for boosting the minimum line voltage selected in the line voltage selection stage to keep the voltage unbalance ratio below the reference value. May be included.

  According to this voltage adjustment method, voltage disequilibrium can be corrected efficiently in a distribution environment where three-phase voltage imbalance is likely to occur due to the spread of distributed power sources such as household photovoltaic power generation systems. Can do.

  In this voltage adjustment method, the voltage adjustment step includes a line voltage measurement step of measuring each of the three-phase line voltages at the control target point, and the voltage imbalance rate is equal to or less than the reference value. As a condition, a line voltage determination step for determining whether any of the three-phase line voltages measured by the line voltage measurement step is out of the voltage management range, and a line voltage Three-phase batch voltage conversion that collectively lowers or boosts the three-phase line voltage when it is determined by the decision step that the three-phase line voltage is out of the voltage management range. And a stage.

  According to this voltage adjustment method, all line voltages can be efficiently accommodated within a predetermined voltage management range by performing three-phase collective voltage control only when the voltage imbalance rate is below the reference value. it can.

  In this voltage adjustment method, the voltage adjustment step may step down or step up the three-phase voltage at a step interval having the same change width.

  According to this voltage adjustment method, efficient voltage management can be performed by controlling the step-up / step-down of the line voltage at the same change width step interval.

  In this voltage adjustment method, the voltage management width may be set by reference voltage ± allowable width.

  According to this voltage adjustment method, voltage management can be reliably performed by setting the voltage management width by the reference voltage ± allowable width.

  According to the present invention, by improving the voltage imbalance rate of the line voltage of the three-phase distribution line at the control target point, the voltage control of the three-phase distribution line is performed, whereby all the line voltages of the three-phase distribution line are set to the predetermined voltage. It is possible to provide a voltage adjustment system and a voltage adjustment method for a distribution system that can be efficiently accommodated within a management width.

  According to the present invention, by controlling the voltage adjustment device that performs voltage control of the three-phase package and the voltage imbalance rate improvement device that improves the voltage imbalance rate at the control target point, the line of the three-phase distribution line is controlled. In addition to correcting the three-phase voltage imbalance that appears between them, it is possible to perform voltage management that keeps the voltage within the allowable range of the reference voltage ± tolerance, thereby preventing the occurrence of faults in the distribution system. A voltage regulation system and a voltage regulation method can be provided.

  According to the present invention, there is provided a voltage adjustment system and a voltage adjustment method for a distribution system useful in a distribution environment in which a three-phase voltage imbalance is likely to occur due to the spread of a distributed power source such as a home solar power generation system. Can be provided.

It is a block block diagram of the simulation model which verifies the voltage adjustment system and voltage adjustment method of the distribution system which concern on embodiment of this invention. It is a block block diagram of the voltage adjustment system of the power distribution system which concerns on embodiment of this invention. It is a vector diagram for demonstrating the relationship between the line voltage and phase voltage of a control target point. It is a flowchart for demonstrating the process which a voltage imbalance rate improvement apparatus performs in the voltage adjustment system and voltage adjustment method of a distribution system which concern on embodiment of this invention. It is a flowchart for demonstrating the process which a voltage regulator performs in the voltage regulation system and voltage regulation method of a distribution system which concern on embodiment of this invention. It is a flowchart for demonstrating the process which a voltage regulator and a voltage imbalance rate improvement apparatus perform in the voltage regulation system and voltage regulation method of a distribution system which concern on embodiment of this invention. It is a flowchart for demonstrating in detail the process which a voltage imbalance rate improvement apparatus performs in the flowchart of FIG. It is the result of the simulation which shows the initial state of the line voltage distribution of each consumer in the simulation model of the voltage adjustment system and voltage adjustment method of the distribution system which concerns on embodiment of this invention. It is the result of the simulation which shows the line voltage distribution of each consumer at the time of performing the control method of the voltage adjustment system and the voltage adjustment method of the distribution system which concerns on embodiment of this invention. It is the result of the simulation which shows the line voltage distribution of the control target point at the time of performing the control method of the voltage adjustment system and the voltage adjustment method of the distribution system which concerns on embodiment of this invention.

<Model 100>
Hereinafter, the usefulness of the voltage regulation system according to the embodiment of the present invention was verified by simulation using the distribution system model 100 shown in FIG. 1 (hereinafter simply referred to as “model 100”). Will be described with reference to FIG.

  The model 100 is a distribution system that distributes three-phase AC 6.7 kV from the power supply source 20 to the consumers 1 to 10 via the feeder 30. The feeder 30 is connected with a load from the consumer 1 closest to the power supply source 20 to the remote customer 10 in numerical order. Electric power is supplied to each of the consumers 1 to 10 from the feeder 30 via a pole transformer (not shown). For the convenience of explanation, the part connected to the consumers 1 to 3 is referred to as a feeder 31, and the part connected to the consumers 4 to 10 is referred to as a feeder 32.

  As is well known, since the feeder 30 has an electrical resistance proportional to the length, it is inevitable that a voltage drop proportional to the current flowing through the feeder 30 occurs in the feeder 30. For this reason, the power supply source 20 supplies the feeder 30 with a high voltage of around 6.7 kV, which is obtained by adding a voltage drop in the feeder 30 and other intervening equipment (not shown) in advance. By carrying out like this, it becomes possible to supply the voltage of 101 +/- 6V prescribed | regulated by the electric power business law to a consumer by selecting the tap of a pole transformer appropriately.

  For the above-described reason, even in the case of a nominal 6.6 kV distribution system, the power supply source 20 supplies the feeder 30 with a higher voltage set in advance around 6.7 kV. Furthermore, in order to compensate for the voltage drop that cannot be handled by the tap of the pole transformer, the voltage regulator 22 made of, for example, SVR or LRT is interposed in the middle of the feeder 30 to compensate for the voltage drop in the middle of the feeder 30. To correct the pressure appropriately. That is, the voltage regulator 22 boosts the lowered voltage to an extent that it is possible to supply a voltage of 101 ± 6 V to a customer in a remote place by appropriately selecting the tap of the pole transformer. To feed power to the feeder 30. In this way, even if the electric power is transmitted from the power supply source 20 with a certain amount of power transmission loss, it is possible to supply a voltage within the range of 101 ± 6 V to the consumer 10 in the remote place. .

  Note that, at the position of the customer 10 at the end of the feeder 30 in the power distribution system, it is assumed that the power is received at a low voltage that further drops from the nominal 6.6 kV. Therefore, it is possible to receive a voltage of 101 ± 6V on the low voltage side by setting the tap of the pole transformer to 6,450V and the transformation ratio to 6,450 / 105V. Here, the voltage drop on the low voltage side of the nominal 100V of the model 100 is expected to be 2.0V for the pole transformer, 3.0V for the low voltage trunk, and 3.0V for the low voltage lead-in.

  The voltage adjusting device 22 is inserted in the middle of the feeder 30, that is, between the feeder 31 and the feeder 32. The feeder 31 is on the side close to the power supply source 20 in the feeder 30, and consumers 1 to 3 are connected to the feeder 31. The feeder 32 is located on the far side of the feeder 30 from the power supply source 20, and the consumers 4 to 10 are connected to the feeder 32.

<Voltage adjustment system>
A configuration of the voltage regulation system 200 according to the embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the voltage regulation system 200 includes a voltage imbalance rate improvement device 21 installed at the position of the customer 10 as a control target point, and a voltage installed between the customer 3 and the customer 4. And an adjusting device 22.

<Voltage imbalance rate improvement device>
As shown in FIG. 2, the voltage imbalance rate improving apparatus 21 receives electric power from the feeder 32, and a main part is constituted by the control means 210.

  The control unit 210 includes a voltage unbalance rate calculation unit 211 that calculates a voltage unbalance rate of the three-phase line voltage at the control target point, and the voltage unbalance rate calculated by the voltage unbalance rate calculation unit 211 is a predetermined value. On condition that the voltage unbalance rate determination unit 212 determines whether or not it is equal to or less than the reference value, and the voltage unbalance rate determination unit 212 determines that the voltage unbalance rate is greater than the reference value, three The line voltage selection unit 213 for selecting the line voltage to be adjusted from the phase line voltage, and the line voltage selected by the line voltage selection unit 213 is stepped down or stepped up to increase the voltage unbalance. A voltage imbalance rate adjustment unit 214 that performs adjustment to keep the rate below a reference value.

  As will be described later, the reference value of the voltage imbalance rate is selected as a value that allows all the line voltages to fall within the voltage management width in the three-phase collective control by the voltage regulator 22.

As shown in Table 1, when the voltage increase can be confirmed at the control target point, the voltage imbalance rate adjustment unit 214 inserts a reactor between the two phases that bring the maximum line voltage as necessary. ing.

  Here, when the voltage rise can be confirmed at the control target point, for example, when a distributed power source such as a solar power generation system is connected to the distribution system, or when a consumer becomes lightly loaded at midnight etc. It is assumed that ferrant phenomenon occurs depending on the capacitor component such as the ground capacitance of the transmission line.

  On the other hand, when a voltage drop can be confirmed at the control target point, the voltage imbalance rate adjustment unit 214 inserts a capacitor between the two phases that provide the minimum line voltage as necessary. .

  Here, when the voltage drop can be confirmed at the control target point, for example, when a distributed power source such as a photovoltaic power generation system is not connected to the distribution system and no ferrant phenomenon occurs, Assume that the situation is heavy. In such a case, it is considered that a voltage drop has occurred at the control target point at the end of the power distribution system.

  Here, the relationship between the three-phase line voltage and the phase voltage will be described. In the three-phase equilibrium state, when a single-phase reactor is inserted between the ab phases of the three-phase voltages, the a-phase voltage is reduced in magnitude and delayed in phase, and the b-phase voltage is reduced in magnitude and phase. Advances. When this is confirmed by the line voltage, the magnitude relationship between the line voltages is: line voltage ab <line voltage ca≈line voltage bc. If this rule is used, the voltage imbalance rate can be improved by reducing the largest voltage among the line voltages in the unbalanced state.

  FIG. 3 is a vector diagram for explaining the relationship between the three-phase line voltage and the phase voltage at the control target point. In FIG. 3, ab, bc, and ca are vector representations of line voltages of unbalanced three-phase wirings at the control target point, and oa, ob, and oc are vector representations of phase voltages. Further, a′b ′, b′c ′, and c′a ′ are the vector display of the line voltage of the three-phase wiring at the control target point after the voltage unbalance rate is improved by the voltage unbalance rate improvement device 21. Oa ′, ob ′, oc ′ are vector representations of phase voltages.

  As shown in FIG. 3, when a single-phase reactor is inserted between the ab phases of the three-phase voltage, the phase voltage oa decreases in magnitude to the phase voltage oa ′ and the phase is delayed, and the phase voltage ob is the phase voltage ob ′. The phase is reduced and the phase advances. As a result, the line voltage ab is reduced to the line voltage a′b ′. As in the case of the above three-phase equilibrium state, in the example of FIG. 3, the amount of decrease in the line voltage ab is larger than other line voltages. This improves the voltage imbalance rate.

<Voltage adjustment device>
As shown in FIG. 2, the voltage adjusting device 22 receives power from the feeder 31 and outputs power to the feeder 32, and a main part is configured by the control means 220. The control unit 220 includes a line voltage measurement unit 221, a line voltage determination unit 222, and a three-phase collective voltage conversion unit 223.

  The voltage regulator 22 includes a single-phase transformer or a single-phase single-winding transformer (hereinafter referred to as “single-phase single-winding transformer”) three-phase connected to a Y-type, a three-phase transformer, Alternatively, the voltage is digitally adjusted by a semiconductor switch. For example, a single-phase autotransformer connected in a Y-phase three-phase connection is equipped with a control device that performs control to simultaneously adjust the voltage of each phase in the same direction of step-up or step-down and three-phase batch control Is possible.

  As is well known, the single-phase autotransformer constituting the voltage regulator 22 adjusts the voltage in a desired step by optimally selecting and controlling the tap of the autotransformer with a switching tap (not shown). It is possible to do.

  In the present embodiment, a method of stepping down or stepping up the three-phase line voltage at the same change width step interval is employed. In this embodiment, the one step voltage is 100V.

  The line voltage measuring unit 221 is configured to measure each line voltage between the phases at the control target point. The line voltage determination unit 222 is preset with the line voltage at the control target point measured by the line voltage measurement unit 221 on condition that the voltage unbalance rate at the control target point is equal to or less than the reference value. It is determined whether or not there is something outside the voltage management range. Further, the line voltage determination unit 222 identifies the direction in which the line voltage most deviating from the voltage management width deviates from the voltage management width.

  The three-phase collective voltage conversion unit 223 collects the three-phase line voltage when the line voltage decision unit 222 determines that there is a line voltage at the control target point that is out of the voltage management range. The voltage is stepped up or down to fall within the voltage management range.

<Voltage imbalance rate improvement method>
FIG. 4 is a flowchart showing a voltage imbalance rate improvement method for three-phase wiring executed by the voltage imbalance rate improvement apparatus 21 included in the voltage regulation system 200 according to the embodiment of the present invention. In the following description, it is assumed that the voltage imbalance rate adjustment unit 214 has a reactor.

  In step S1, the control means 210 of the voltage imbalance rate improving apparatus 21 defines the reference value of the voltage imbalance rate at the control target point and the operation settling time (first predetermined time) related to the adjustment of the voltage imbalance rate. To do. For example, the control target point is the position of the customer 10 shown in FIG. Further, as shown in Table 2, the reference value ref_1 of the voltage unbalance rate at the control target point is set to 1.2%, for example, and the operation settling time Δt1 is set to 15 (s).

  As will be described later, the operation settling time Δt1 is the time when the voltage unbalance rate improvement device 21 detects a voltage unbalance rate greater than the reference value ref_1, and starts adjusting the line voltage for improving the voltage unbalance rate. This is the time until

Further, the capacity of the single-phase reactor that is input at a time is 100 kVar, and the maximum capacity of the single-phase reactor that is input is 200 kVar. That is, the total number of reactors to be charged is any one of 0 kVar, 100 kVar, and 200 kVar. Note that these values are merely examples, and in the actual voltage regulation system 200, the capacity and the number of charging operations of a single-phase reactor that are charged at a time may be different from those described above.

Next, in step S <b> 2, the voltage unbalance rate calculation unit 211 of the control unit 210 calculates the voltage unbalance rate Vk at the control target point according to Equation 1.

  Furthermore, in step S2, the voltage unbalance rate determination unit 212 of the control unit 210 determines whether or not the voltage unbalance rate at the control target point is larger than the reference value ref_1. When the voltage imbalance rate at the control target point is larger than the reference value ref_1, the control unit 210 turns on the departure flag (step S3) and proceeds to the process of step S5. On the other hand, when the voltage imbalance rate at the control target point is equal to or less than the reference value ref_1, the control unit 210 turns off the departure flag (step S4) and executes the process of step S2 again.

  Next, in step S5, when the departure flag is turned on, the control unit 210 determines whether or not the operation settling time Δt1 has elapsed since the departure flag was turned on in step S3. When the operation settling time Δt1 has elapsed since the departure flag is turned on, the control unit 210 proceeds to the process of step S6. On the other hand, if the operation settling time Δt1 has not elapsed since the departure flag is turned on, the control unit 210 executes the process of step S5 again.

  Next, in step S6, the line voltage selection unit 213 of the control unit 210 selects the maximum line voltage among the line voltages ab, bc, and ca.

  Next, when the maximum line voltage selected by the line voltage selection unit 213 is the line voltage ab, the voltage imbalance ratio adjustment unit 214 of the control unit 210 converts the single-phase reactor of 100 kVar to the ab phase. When the maximum line voltage selected by the line voltage selection unit 213 is the line voltage bc, a single-phase reactor of 100 kVar is input to the bc phase (step S8). When the maximum line voltage selected by the voltage selection unit 213 is the line voltage ca, a 100 kVar single-phase reactor is input to the ca phase (step S9). And the control means 210 performs the process of step S2 again.

  In the flowchart of FIG. 4, it is assumed that a voltage increase can be confirmed at the control target point (see Table 1). When the voltage drop can be confirmed at the control target point, the process of step S6 is performed by the line voltage selection unit 213 of the control unit 210 to select the minimum line voltage among the line voltages ab, bc, and ca. replace. Moreover, the process of step S7-S9 is replaced with the process which throws in a capacitor | condenser between each phase.

  In the above description, in steps S7 to S9, the reactor or the capacitor is inserted between the phases. However, the reactor or the capacitor that is input may be opened depending on the situation. For example, when the voltage increase can be confirmed at the control target point, the line voltage can be decreased by releasing the already input capacitor.

  Similarly, when a voltage drop can be confirmed at the control target point, the line voltage can be increased also by releasing the reactor that has already been turned on.

<Three-phase batch control>
FIG. 5 is a flowchart showing a voltage adjustment method for three-phase wiring executed by the voltage adjustment device 22 included in the voltage adjustment system 200 according to the embodiment of the present invention.

  In step S21, the control means 220 of the voltage regulator 22 defines the reference voltage of the control target point and its allowable width, and the operation settling time (second predetermined time) related to the three-phase collective control. The control target point is the position of the customer 10 shown in FIG. Further, as shown in Table 3, the reference voltage ref_2 at the control target point is, for example, 6,450 (V), the allowable width tol is ± 96.75 V that is ± 1.5% of the reference voltage, and the operation settling time Δt2 is 50 ( s). Further, the voltage adjustment width in one step is set to 100V.

As will be described later, the operation settling time Δt2 is the time from when the voltage regulator 22 detects a line voltage outside the voltage management range to when the three-phase collective voltage control is started.

  Next, in step S22, the line voltage measuring unit 221 of the control unit 220 measures each of the line voltages ab, bc, ca between the phases at the control target point. Then, the line voltage determination unit 222 of the control means 220 has a voltage management width out of the line voltages ab, bc, ca at the control target point, that is, out of the range of the reference voltage ref_2 ± allowable width tol. Judge whether or not.

  If any of the line voltages ab, bc, ca at the control target point is out of the voltage management range, the control means 220 turns on the departure flag (step S23) and proceeds to the process of step S25. On the other hand, when none of the line voltages ab, bc, and ca at the control target point are out of the voltage management range, the control unit 220 turns off the departure flag (step S24) and executes the process of step S22 again. .

  Next, in step S25, when the departure flag is on, the control unit 220 determines whether or not the operation settling time Δt2 has elapsed since the departure flag was turned on in step S23. If the operation settling time Δt2 has not elapsed since the departure flag is turned on, the control unit 220 executes the process of step S25 again. On the other hand, when the operation settling time Δt2 has elapsed since the departure flag is turned on, the control unit 220 proceeds to the process of step S26.

  Here, the operation settling time Δt2 related to the three-phase collective control is set sufficiently longer than the operation settling time Δt1 related to the adjustment of the voltage imbalance rate. As a result, while the operation settling time Δt2 is being counted in step S25, the voltage imbalance rate of the line voltage is adjusted to a reference value or less.

  Next, in step S26, the line voltage determination unit 222 of the control unit 220 performs voltage management on the line voltage that deviates most from the voltage management range, that is, the line voltage having the largest absolute value of the difference from the reference voltage ref_2. Select the direction deviating from the width.

  Next, the three-phase collective voltage conversion unit 223 of the control unit 220 determines that the deviation direction selected by the line voltage determination unit 222 is the upper limit side of the voltage management width, that is, the line voltage that deviates most from the voltage management width. If the value obtained by subtracting ref_2 is positive, tap switching is performed to the 1-tap step-down side (step S27).

  On the other hand, if the deviation direction selected by the line voltage determining unit 222 is negative, the value obtained by subtracting the reference voltage ref_2 from the line voltage that deviates most from the voltage management width is negative. The three-phase collective voltage converter 223 of the means 220 performs tap switching to the 1-tap boost side (step S28). And the control means 220 performs the process of step S22 again.

  After step S25, as step S29, whether the line voltage determination unit 222 of the control means 220 is out of the voltage management range among the line voltages ab, bc, ca at the control target point. A process for determining again whether or not may be added. Here, the reason why the same processing as in step S22 is repeated is that the voltage imbalance rate is adjusted to a reference value or less while the operation settling time Δt2 is being counted in step S25, so that all the line voltages are This is because the voltage may be within the voltage management range.

  When there is a voltage that is outside the voltage management range among the line voltages ab, bc, and ca at the control target point, the control unit 220 proceeds to the process of step S26. On the other hand, when none of the line voltages ab, bc, and ca at the control target point are out of the voltage management range, the control unit 220 turns off the departure flag (step S24) and executes the process of step S22 again. .

  As described above with reference to the flowcharts of FIGS. 4 and 5, in the present invention, it is important that the improvement of the voltage imbalance ratio is performed prior to the three-phase batch voltage control. In order to realize this, in step S5 in the flowchart of FIG. 4 and step S25 in the flowchart of FIG. 5, the operation settling time Δt1 is set shorter than the operation settling time Δt2. The improvement of the voltage unbalance rate by 21 and the three-phase collective voltage control by the voltage regulator 22 are coordinated.

  As another method, it is conceivable that the operation of the voltage imbalance rate improving device 21 and the voltage adjusting device 22 is coordinated using communication using a dedicated line. The flowchart in this case is shown in FIGS.

  The flowchart of FIG. 6 is the same as the flowchart of FIG. 5 with respect to the processes of steps S21 to S24 and S26 to S29, and the processes of steps S21 to S24 and S26 to S29 are executed by the control means 220 of the voltage regulator 22. The The process of step S30 in the flowchart of FIG. 6 is obtained by replacing the process of step S25 of the flowchart of FIG. 5 with the process of the flowchart of FIG. 7, and is executed by the control unit 210 of the voltage imbalance rate improving apparatus 21. The

  7 is the same as the flowchart of FIG. 4 with respect to the processes of steps S1 to S3 and S5 to S9. The processes of steps S1 to S3 and S5 to S9 are controlled by the voltage imbalance rate improving apparatus 21. Performed by means 210. If the voltage unbalance rate at the control target point is equal to or less than the reference value ref_1 in step S2, the process is terminated and the process of the flowchart of FIG. 5 executed by the control means 220 of the voltage regulator 22 is performed. To come back.

  This provides the same effect as the method shown in the flowcharts of FIGS. 4 and 5 for providing a difference in the operation settling time. However, when cost and maintenance are taken into consideration, communication using a dedicated line is used. 4 and 5 are more preferable than the method of FIGS.

<Simulation of model 100>
Next, simulation is advanced by assigning specific numerical values to the model 100 shown in FIG. In the model 100, some of the consumers 1 to 10 have a single-phase load power demand that is largely biased with respect to the three-phase power distribution system. For this reason, the three-phase voltage in the model 100 has an unbalance that deviates from the allowable range. For this reason, the voltage regulation system 200 corresponds to both improving the imbalance and managing the voltage.

  In the model 100, the power supply source 20 is a system power supply of 6.7 kV, and the back impedance of the system is j0.389Ω. The power supply source 20 distributes power to consumers 1 to 10 connected at equal intervals of 0.5 km over the entire length of the feeder 30 of 4.0 km. Consumers 1 to 9 are connected to a balanced three-phase load of 300 kW. The customer 10 is connected to a photovoltaic power generation (PV) system of 360 kW between the bc lines and 310 kW between the ca lines.

  As described above, the voltage adjustment device 22 is installed between the customer 3 and the customer 4, and the voltage imbalance rate improvement device 21 is installed at the position of the customer 10. The control target point is the position of the customer 10.

  The transformation ratio of the pole transformer of the customer 10 is 6,450 / 105V, and the voltage drop on the low voltage side is as follows.

Pillar transformer: 2.0V
Low voltage main line: 3.0V
Low voltage lead-in wire: 3.0V
Thus, when the voltage management width 101 ± 6 V on the low voltage side is converted to the high voltage side, it becomes 6,327 V to 6,573 V.

  The setting conditions of the voltage imbalance rate improving device 21 and the setting conditions of the voltage adjusting device 22 by simulation are as already shown in Table 2 and Table 3, respectively. By setting the operation settling time Δt1 of the voltage unbalance rate improving device 21 to be shorter than the operation settling time Δt2 of the voltage adjusting device 22, the improvement of the voltage unbalance rate is executed prior to the three-phase batch voltage control. It is set to be.

Next, simulation results will be described.
FIG. 8 is a graph showing a simulation result in an initial state before voltage adjustment of the line voltage distribution of each consumer. As shown in FIG. 8, the line voltage bc and the line voltage ca deviate from the upper limit of the voltage management width at the position of the customer 10 as the control target point. The voltage imbalance rate at the control target point is 1.9%.

  Here, when the voltage control at the control target point is performed using only the voltage adjusting device 22 of the three-phase collective control, the line voltage ca and the line voltage bc are set to the voltage management width by performing the tap switching to the step-down side. In this case, the ab line voltage deviates from the lower limit of the voltage management width. Thus, when the difference between the maximum line voltage and the minimum line voltage at the control target point is large, in order not to improve the voltage imbalance rate at the control target point, all the line voltages must be It can be seen that the voltage management range cannot be accommodated.

  FIG. 9 is a graph showing a simulation result when voltage control is performed using the voltage adjustment device 22 after the voltage unbalance rate is improved to a reference value or less using the voltage unbalance rate improvement device 21. It can be confirmed that all the line voltages at the control target point can be controlled within the voltage management range. The voltage imbalance rate at this time is 1.0%.

  Here, as shown in Table 2, it is assumed that the input reactor capacity to the same phase of the voltage imbalance ratio improving device 21 is 100 kVar for the first time and 100 kVar for the second time. However, when the voltage unbalance rate is improved to a reference value or less by the first reactor introduction, the second reactor introduction is not performed. Further, 1.2% of the reference value of the voltage imbalance rate is selected as a value that allows all line voltages to fall within the voltage management width in the three-phase collective control.

  FIG. 10 is a graph showing the simulation result of the voltage change at the control target point. The first single-phase reactor is charged in the region surrounded by the broken line on the left side of the graph of FIG. 10 (around 15 s), and the second single phase is input in the region surrounded by the central broken line (around 30 s). Reactor is being introduced. As a result, the voltage unbalance rate at the control target point is improved to a reference value or less.

  Furthermore, three-phase collective voltage control is performed in a region surrounded by a broken line on the right side of the graph of FIG. After the three-phase collective control, it can be confirmed from the graph that the line voltages of all the phases are within the voltage management range.

  As described above, in the distribution system in which the voltage rise and the voltage imbalance are actualized, it is difficult to cope with the voltage control and the improvement of the voltage imbalance by controlling the output of the voltage regulator 22 in a three-phase manner. . However, the simulation has shown that the voltage control of the distribution system and the improvement of the voltage imbalance rate can be steadily performed by controlling the voltage adjustment device 22 and the voltage imbalance rate improvement device 21 in cooperation.

  The model 100 in the present embodiment is a distribution system that distributes power in one direction from the single power supply source 20 as shown in FIG. 1, but the model 100 is merely an example. The voltage adjustment system and voltage adjustment method for a distribution system according to the present invention can be applied to a distribution system in which distributed power sources are unbalanced and include the influence of reverse power flow or the like. For example, it is also suitable for the case where an unbalance caused by reverse flow of single-phase power obtained from a household solar power generation system to any one of the three phases of the distribution system is improved.

  Further, the voltage adjustment width of one step of the voltage adjustment device 22 is a predetermined fixed width 100V, but is not limited to the fixed width 100V, and is controlled so that an optimum voltage adjustment width can be set according to the situation. May be. The voltage adjustment range includes stepless.

  In the present embodiment, the voltage regulator 22 uses a single-phase single-wound transformer as a main component, but the present invention is not limited to this, and may be an equivalent function composed of a semiconductor. Absent. With such a semiconductor device, the voltage width of the above-described step voltage may be set in an arbitrary stepless manner.

  As described above, according to the present invention, by controlling the voltage adjustment device that performs voltage control of the three-phase package and the voltage imbalance rate improvement device that improves the voltage imbalance rate at the control target point, the control is performed. In addition to correcting the three-phase voltage imbalance that appears between the lines of the three-phase distribution line, it is possible to perform voltage management that keeps the voltage within the reference voltage ± tolerance, thereby preventing failure It is possible to provide a voltage adjustment system and a voltage adjustment method for a power distribution system that can be prevented.

  In particular, according to the present invention, a voltage adjustment system and a voltage adjustment method for a distribution system useful in a distribution environment in which a three-phase voltage imbalance is likely to occur due to the spread of a distributed power source such as a home solar power generation system. Can be provided.

DESCRIPTION OF SYMBOLS 1-10 Consumer 20 Power supply source 21 Voltage imbalance rate improvement apparatus 22 Voltage adjustment apparatus 30, 31, 32 Feeder 100 Distribution system model 200 Voltage adjustment system 210,220 Control means 211 Voltage imbalance ratio calculation part 212 Voltage imbalance Rate determination unit 213 Line voltage selection unit 214 Voltage imbalance rate adjustment unit 221 Line voltage measurement unit 222 Line voltage determination unit 223 Three-phase collective voltage conversion unit oa, ob, oc Phase voltage ab, bc, ca Line voltage

Claims (12)

A voltage adjustment system that adjusts the magnitude of a three-phase line voltage that appears between the lines of a three-phase distribution line at a control target point, and keeps the line voltage within a predetermined voltage management range,
When it is determined whether the voltage unbalance rate of the three-phase line voltage at the control target point is greater than a predetermined reference value, and it is determined that the voltage unbalance rate is greater than the reference value The step-down or step-up of the line voltage selected from the three-phase line voltage after the first predetermined time has elapsed, thereby reducing the voltage unbalance rate at the control target point below the reference value. A voltage imbalance rate improvement device for adjusting
It is determined whether or not any of the three-phase line voltages at the control target point deviates from the voltage management width, and the three-phase line voltages deviate from the voltage management width. If it is determined that there is a voltage, the three-phase line voltage is collectively reduced or boosted within the voltage management width after a second predetermined time longer than the first predetermined time. A voltage regulation system comprising: a voltage regulation device that performs the operation. The voltage imbalance rate improving device is:
A voltage unbalance rate calculating unit for calculating the voltage unbalance rate;
A voltage imbalance rate determination unit for determining whether the voltage imbalance rate is equal to or less than the reference value;
A line for selecting the maximum line voltage among the three-phase line voltages on the condition that the voltage unbalance ratio is determined to be larger than the reference value by the voltage unbalance ratio determination unit. The voltage selection section,
The voltage unbalance rate adjustment unit that steps down the maximum line voltage selected by the line voltage selection unit and keeps the voltage unbalance rate below the reference value. The voltage regulation system described. The voltage imbalance rate improving device is:
A voltage unbalance rate calculating unit for calculating the voltage unbalance rate;
A voltage imbalance rate determination unit for determining whether the voltage imbalance rate is equal to or less than the reference value;
A line for selecting the minimum line voltage among the three-phase line voltages on the condition that the voltage unbalance ratio is determined to be larger than the reference value by the voltage unbalance ratio determination unit. The voltage selection section,
The voltage unbalance rate adjustment unit that boosts the minimum line voltage selected by the line voltage selection unit and keeps the voltage unbalance rate below the reference value. The voltage regulation system described. The voltage regulator is
A line voltage measuring unit for measuring each of the three-phase line voltages at the control target point;
Whether or not any of the three-phase line voltages measured by the line voltage measurement unit deviates from the voltage management width on condition that the voltage imbalance rate is equal to or less than the reference value. A line voltage determination unit for determining whether or not
Three-phase voltage step-down or step-up for the three-phase line voltage when the line voltage determination unit determines that any of the three-phase line voltages is out of the voltage management range. The voltage adjustment system according to claim 1, further comprising a collective voltage conversion unit.   5. The voltage regulation system according to claim 1, wherein the voltage regulation device steps down or boosts the three-phase line voltage at a step interval having the same change width. 6.   6. The voltage adjustment system according to claim 1, wherein the voltage management width is set by a reference voltage ± allowable width. A voltage adjustment method for adjusting the magnitude of the three-phase line voltage appearing between the lines of the three-phase distribution line at the control target point, and keeping the line voltage within a predetermined voltage management range,
When it is determined whether the voltage unbalance rate of the three-phase line voltage at the control target point is greater than a predetermined reference value, and it is determined that the voltage unbalance rate is greater than the reference value The step-down or step-up of the line voltage selected from the three-phase line voltage after the first predetermined time has elapsed, thereby reducing the voltage unbalance rate at the control target point below the reference value. Voltage imbalance rate improvement stage to make adjustments,
It is determined whether or not any of the three-phase line voltages at the control target point deviates from the voltage management width, and the three-phase line voltages deviate from the voltage management width. If it is determined that there is a voltage, the three-phase line voltage is collectively reduced or boosted within the voltage management width after a second predetermined time longer than the first predetermined time. A voltage adjustment step of performing a voltage adjustment step. The voltage imbalance rate improvement step includes:
A voltage unbalance rate calculating step for calculating the voltage unbalance rate;
A voltage unbalance rate determination step of determining whether the voltage unbalance rate is equal to or less than the reference value;
A line for selecting the maximum line voltage among the three-phase line voltages on the condition that the voltage unbalance ratio is determined to be larger than the reference value in the voltage unbalance ratio determination step. Voltage selection stage,
8. The voltage unbalance rate adjustment step of stepping down the maximum line voltage selected in the line voltage selection step so that the voltage unbalance rate falls below the reference value. The voltage adjustment method as described. The voltage imbalance rate improvement step includes:
A voltage unbalance rate stage for calculating the voltage unbalance rate;
A voltage unbalance rate determination step of determining whether the voltage unbalance rate is equal to or less than the reference value;
A line for selecting a minimum line voltage among the three-phase line voltages on the condition that the voltage unbalance ratio is determined to be larger than the reference value in the voltage unbalance ratio determination step. Voltage selection stage,
The voltage unbalance rate adjustment step of boosting the minimum line voltage selected in the line voltage selection step so that the voltage unbalance rate falls below the reference value. The voltage adjustment method as described. The voltage adjustment step includes:
A line voltage measurement stage for measuring each of the three-phase line voltages at the control target point;
Whether or not any of the three-phase line voltages measured by the line voltage measurement step is out of the voltage management range on condition that the voltage imbalance rate is equal to or less than the reference value. A line voltage determination stage for determining whether or not
Three-phase voltage step-down or step-up for the three-phase line voltage when it is determined in the line voltage determination step that there is one of the three-phase line voltages outside the voltage management range. The voltage adjustment method according to claim 7, further comprising a batch voltage conversion step.   11. The voltage adjustment method according to claim 7, wherein in the voltage adjustment step, the three-phase voltage is stepped down or stepped up at a step interval having the same change width.   12. The voltage adjustment method according to claim 7, wherein the voltage management width is set according to a reference voltage ± allowable width.

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