JP4101788B2 - Voltage adjusting device and voltage adjusting method - Google Patents

Description

  The present invention relates to a voltage adjustment device and a voltage adjustment method for adjusting a voltage of a distribution system to a specified range.

  For the purpose of reducing the size and price of an automatic voltage regulator installed at the load end of a single-phase power distribution system, the output capacity of the voltage regulator constructed using a series transformer, inverter, and converter is adjusted to the rated capacity of the load. Japanese Patent Application Laid-Open No. H10-228688 discloses a technique for making the content about 10 to 20%.

  Also, a three-phase voltage phase adjustment device that is installed in the middle of the distribution line and adjusts the voltage phase is composed of a combination of a three-phase tap switching phase adjuster, a series transformer, and a three-phase static voltage regulator. A technique for adjusting the magnitude and phase of a voltage without being limited by the width is disclosed in Patent Document 2.

Japanese Patent Laid-Open No. 2001-5541

JP 2000-232735 A

  However, the above prior art does not clarify a voltage adjustment method, particularly a method for adjusting the voltage of the distribution (low voltage) system to an appropriate range when the distributed power source is connected to the distribution system. In particular, a low-voltage distribution system capable of maintaining an appropriate voltage over the entire low-voltage distribution system in which solar power generation is introduced has not been realized.

  An object of the present invention is to provide a low-voltage distribution system capable of maintaining an appropriate voltage over the entire area, and a voltage adjustment method and apparatus thereof in view of the current state of the prior art.

  The present invention that achieves the above object provides a voltage regulator for a power system that includes a pole transformer connecting a high-voltage distribution system and a low-voltage distribution system, a consumer load connected to the low-voltage distribution system, and a distributed power source. A series transformer having a primary side connected in series to a secondary side of the pole transformer, a regulated voltage control circuit that receives a voltage measurement value of a low-voltage distribution system, and an output of the regulated voltage control circuit And an adjustment voltage generation circuit for generating an adjustment voltage on the secondary side of the series transformer.

  In addition, a series transformer connected in primary to the secondary side of the pole transformer, a bypass switch connected between the secondary terminals of the series transformer, and a voltage measurement value of the low-voltage distribution system An adjustment voltage control circuit that receives the adjustment voltage, an adjustment voltage generation circuit that generates an adjustment voltage on the secondary side of the series transformer based on the output of the adjustment voltage control circuit, and the adjustment according to the voltage of the low-voltage distribution system In order to start or stop the voltage generation circuit, a protection circuit for opening or closing the bypass switch is provided.

  The adjustment voltage control circuit includes a sensor that detects a voltage of the low-voltage distribution system, a voltage calculation unit that calculates a voltage effective value from a voltage measurement value detected by the sensor, and a target voltage setting unit that sets a target voltage in advance. And an adjustment voltage calculation unit that calculates the adjustment voltage from the effective voltage value and the target voltage.

  The present invention is also a power system comprising a pole transformer connecting a high voltage distribution system and a low voltage distribution system, and a consumer load or a distributed power source connected to the low voltage distribution system, the pole transformer Includes the voltage regulator.

  The voltage adjustment method of the present invention is a voltage adjustment method for a power system in which a high voltage distribution system and a low voltage distribution system are connected by a pole transformer, and a consumer load and a distributed power source are connected to the low voltage distribution system, Obtain the effective value of the voltage from the measured value of the line voltage of the low-voltage distribution system, control the adjustment voltage generation circuit based on the deviation between the effective value and a predetermined target voltage, the secondary side of the pole transformer The output of the adjustment voltage generating circuit is supplied to the secondary side of the series transformer so that the primary side voltage of the series transformer connected to the primary side is equivalent to the deviation.

  Further, the effective value of the voltage is obtained from the measured value of the line voltage of the low-voltage distribution system, and the adjustment voltage generating circuit is controlled based on the deviation between the effective value and a predetermined target voltage. Supply the output of the regulated voltage generation circuit to the secondary side of the series transformer so that the primary side voltage of the series transformer connected to the primary side is equivalent to the deviation, and the voltage of the low-voltage distribution system The bypass switch between the adjustment voltage generating circuit and the series transformer is opened or closed according to the operation.

The target voltage is set to 101V. Alternatively, the target voltage is set based on the load contract capacity connected to the low voltage system and the distributed power contract capacity. Alternatively, the target voltage is set according to equation (1).
Target voltage = load contract capacity / (load contract capacity + distributed power contract capacity) x 12 + 95 (1)
In addition, when the time during which the voltage of the low-voltage distribution system exceeds the minimum voltage setting value becomes longer than the timer setting value, the adjustment voltage generation circuit (power converter) is started or the bypass switch is opened. And

  In addition, when the voltage of the low voltage distribution system is larger than the dead band minimum voltage setting value and smaller than the dead band maximum voltage setting value, the bypass switch is short-circuited when the duration becomes longer than the timer setting value. Features.

  According to the voltage regulator and the voltage regulation method of the present invention, the system voltage of the low-voltage distribution system can be maintained in an appropriate range. As a result, measures such as increasing the capacity of the transformer, increasing the voltage of the low-voltage line, and dividing the system, which have been conventionally performed for maintaining an appropriate voltage, become unnecessary. In addition, the power generation efficiency of a distributed power source such as solar power generation in a low-voltage system can be improved. Further, it is possible to suppress the occurrence of flicker due to mutual interference between load change and inverter control.

  Further, according to the voltage regulator and the voltage regulation method of the present invention, the voltage regulator is prevented from restarting in an unstable system state, so that there is an advantage that the system can be stably restarted without causing disturbance to the system. is there.

  Further, according to the voltage regulator and voltage regulation method of the present invention, when voltage control is unnecessary, the voltage regulation device and the voltage regulation method are in a dormant state. There is an advantage that can be extended.

  FIG. 1 is a configuration diagram of a voltage adjusting apparatus showing an embodiment of the present invention. The primary side of the pole transformer 110 is connected to the lines 10u and 10v which are the two phases of the distribution line of the high voltage distribution system with a line voltage rating of 6kV, and the secondary side of the pole transformer 110 is a low voltage distribution line with a rating of ± 105V. 20a, 20b and neutral wire 20n. The voltage adjusting device 100 includes a pole transformer 110 and a voltage adjusting circuit 120.

  As shown below, the voltage adjustment circuit 120 includes series transformers 211 and 212, a bypass switch 220, an adjustment voltage generation circuit 230, a voltage sensor 213, an adjustment voltage control circuit 240, a protection device 214, a circuit that combines them, and information transmission Consists of means. The series transformers 211 and 212 are inserted in series in the low-voltage distribution lines 20a and 20b, respectively, on the primary side.

  The secondary sides of series transformers 211 and 212 are connected to the AC terminal of inverter 231 of adjustment voltage generation circuit 230. A bypass switch 220 is provided between the inverter 231 and the secondary side of the series transformers 211 and 212, and shorts and opens between the lines based on an opening / closing command from the protection device 214. The adjustment voltage generation circuit 230 includes an inverter 231, a converter 232, a DC capacitor 233, and a converter control device 234.

  The AC side terminal of the converter 232 is connected to the low voltage distribution lines 20 a and 20 b, and the DC terminal is connected to the DC capacitor 233. The DC terminal of the inverter 231 is also connected to the series capacitor 233. Control commands for inverter 231 and converter 232 are given by converter control device 234. The adjustment voltage control circuit 240 includes a voltage calculation unit 241, an adjustment voltage calculation unit 242, and a target voltage setting unit 243.

  In FIG. 1, the AC side terminal of the converter 232 is connected to the low voltage distribution lines 20a and 20b on the high voltage system side (between the pole transformer 110 and the series transformers 211 and 212) from the series transformers 211 and 212. However, you may connect with the low voltage distribution line 20a, 20b by the low voltage | pressure system side from the series transformer 211,212.

  Next, an outline of voltage adjustment by the voltage adjustment apparatus 100 will be described. The line voltage between an and bn of the low-voltage system is measured by the voltage sensor 213, and the measured signal is sent to the voltage calculation unit 241 of the adjustment voltage control circuit 240 and converted into the voltage effective value Ve and the voltage phase θ. The Ve is sent to the adjustment voltage calculation unit 242 and the protection device 214, and θ is sent to the converter control device 234. A target voltage Vref is set in advance in the target voltage setting unit 243, and this Vref is sent to the adjustment voltage calculation unit 242. The adjustment voltage calculation unit 242 calculates a voltage deviation ΔV to be adjusted by the voltage adjustment device 100. That is, the deviation between the target voltage Vref and the voltage Ve of the low voltage system is calculated and used as the output of the adjustment voltage calculator 242. The ΔV signal is sent to the converter control device 234, and the converter control device 234 controls the inverter 231 and the converter 232 so that the primary side voltages of the series transformers 211 and 212 are equivalent to ΔV.

  That is, if the transformation ratio of the series transformers 211 and 212 is primary: secondary is 1: m, a control command is given to the inverter 231 and the converter 232 so that the output voltage of the inverter 231 becomes ΔV × m. At this time, ΔVa applied to the a phase is controlled to be in phase with the phase θa of the voltage V′an between an. Further, ΔVb applied to the b phase is a voltage whose phase is inverted by 180 ° from ΔVa. In this way, the voltages ΔVa and ΔVb are generated on the primary side of the series transformers 211 and 212.

  When the low-voltage distribution system is balanced, the primary-side voltages ΔVa and ΔVb of the series transformers 211 and 212 are added to the secondary-side voltages Va and Vb of the pole transformer 110, whereby the low-voltage system voltage V ′ an and V′bn are controlled to be the target voltage Vref.

  Further, in the voltage adjustment circuit 120, even when the series transformers 211 and 212, the bypass switch 220, and the inverter 231 of the adjustment voltage generation circuit 230 are configured independently between an and bn, the voltage V′an of the low voltage system , V′bn can be controlled to be the target voltage Vref. Further, the converter control device 234 of the adjustment voltage control circuit 240 and the adjustment voltage generation circuit 230 is configured to calculate and output the voltage deviation ΔV to be adjusted by the voltage adjustment device 100 independently between an and bn. . Thereby, even when the low voltage system is unbalanced, the voltages V′an and V′bn of the low voltage system can be controlled to be the target voltage Vref.

  The protection device 214 gives an opening / closing command for the bypass switch 220 and a switch start / stop command to the converter control device 234 based on the voltage Ve calculated by the voltage calculation unit 241. The processing algorithm of the protection device 214 will be described later.

  The response speed of the converter control device 234 needs to be limited to a certain value or less in order to suppress mutual interference with other inverter devices linked to the low-voltage system and generation of voltage flicker. For example, flicker is likely to occur due to voltage oscillations in the vicinity of 10 Hz at which the human visibility coefficient is the largest, so it is a guideline to set a response speed of about 1 second or more sufficiently slower than this.

  Next, the configuration of the power distribution system to which the voltage regulator 100 of the present invention is applied will be described with reference to the single-line connection diagram shown in FIG. The primary side (high voltage side) of the voltage regulator 100 is connected to the high voltage distribution line 10 connected to the distribution substation 11, and the low voltage distribution line 20 is connected to the secondary side (low voltage side). A service line 21 to the customer is connected to the low-voltage distribution line 20, and a customer load 22 and solar power generation equipment 23 are connected to the end of the service line 21.

  According to the provisions of the Electricity Business Law, the voltage at the end of the lead-in line to the consumer needs to be kept within 101 ± 6V. Now, considering the case of a distribution system to which the solar power generation 23 is not connected, the highest voltage of a customer receiving power via the high-voltage distribution line 10 may be set to 107 V or lower, and the lowest voltage may be set to 95 V or higher. When a load is connected to the distribution line, a voltage drop occurs according to the impedance of each line or transformer due to the load current. In this case, for example, if the configuration of the distribution system is such that the voltage drop is smaller than the voltage drop amount distribution (100 V converted value) as shown in FIG. 3, the voltage at the consumer end falls within the above-mentioned 101 ± 6V. It will be.

  The influence on the voltage distribution when a distributed power source such as the photovoltaic power generation 23 is connected to the power distribution system designed in this way will be described. FIG. 4 is a graph showing an example of the voltage distribution of each component (FIG. 2) of the power distribution system. The horizontal axis represents a representative location of the power distribution system, and the vertical axis represents a voltage value converted to 100 V rating.

  A graph 410 shows the voltage distribution when the voltage drop is the largest due to the voltage drop distribution of FIG. 3 when there is no distributed power source. In other words, when a voltage of 107 V in the constant voltage system in the immediate vicinity of the distribution substation is used as the delivery voltage of the distribution substation 11, a voltage drop equivalent to 4 V occurs in the high voltage system, and the pole transformer is 103 V on the high voltage side. As a result, a voltage drop corresponding to 2V occurs, causing a voltage drop of 101V on the low voltage side, similarly 3V on the low voltage line, and 3V on the lead-in line. Eventually, the power distribution system can be configured so that the voltage is maintained at 95 V at most at the consumer end.

  However, when a distributed power source such as the solar power generation 23 is connected and the load is small, the direction of the current of the distribution line flows from the terminal customer side to the distribution substation side due to the reverse power flow from the distributed power source. As a result, the voltage at the end of the power distribution system may increase. For example, the voltage distribution in the graph 411 shows an example in which the photovoltaic power generation having the same capacity as the consumer load capacity is rated output and the consumer load is zero. In this case, the voltage exceeds 107 V near the customer end of the service line.

  Under such circumstances, the voltage distribution when the voltage adjusting device 100 controls the voltage at the low-voltage line delivery point to 101 V is as shown in a graph 412. The total voltage increase of the low-voltage line and the lead-in line is 6V at most if the general power generation equipment capacity does not exceed the customer load capacity. The power distribution system can be configured to be within 101 ± 6V.

  Next, a voltage control method when the contract capacity of the load 22 connected to the low-voltage system 12 and the contract capacity of the distributed power source 23 are known will be described. FIG. 5 shows an example of voltage distribution during voltage control of a low-voltage system in which the contracted capacity of the distributed power source is 1/3 of the contracted capacity of the load. Here, the contracted capacity of the load 22 connected to the low-voltage system 12 is set such that a maximum voltage drop of 6 V occurs between the low-voltage line 20 and the lead-in line 21 when the load current is maximum.

  In this case, when the load current is 0 and the output of the distributed power source is the maximum, the voltage increase generated in the low voltage line 20 and the lead-in line 21 due to the current flowing from the distributed power source 23 to the pole transformer is the maximum load current. 1/3 of the voltage drop at that time. That is, a voltage increase of about 2V, which is 1/3 of 6V, occurs. Therefore, in this low-voltage system, it can be seen that the total voltage drop of the low-voltage line 20 and the lead-in line 21 is 6 V at the maximum and the voltage increase is 2 V at the maximum. In this case, it is desirable that the margins up to the specified voltage values of 95V and 107V are provided at the same ratio in both the upper and lower sides.

Therefore, the control voltage target value Vref of the voltage regulator 100 may be obtained by equation (1).
Vref = WL / (WL + WG) × 12 + 95 (1)
Here, WL represents the contract capacity of the load, and WG represents the contract capacity of the distributed power source. The expression (1) means that the voltage at the low-voltage system delivery point (low voltage side of the voltage regulator 100) is shifted from 101V in accordance with the ratio of the load 22 and the distributed power source 23.

For example, in the example of FIG. 5, since WG is 1/3 of WL, it is understood that Vref is obtained as shown in Equation (2), and the low-voltage side end of voltage regulator 100 may be set to 104V.
Vref = WL / (WL + (1/3) WL) × 12 + 95 = 104 (V) (2)
Next, processing of the protection device 214 will be described. FIG. 6 shows a processing flow of the restart algorithm when a system failure or power failure is recovered. Here, V is a voltage of the power distribution system, Vlow is a minimum voltage set value that serves as a standard for restart, τ is a time counter, and τmin is a timer set value.

  The time counter τ is reset to 0 at S1. In S2, it is monitored whether the system voltage V is equal to or higher than Vlow, and if the result is less than Vlow, the process returns to the beginning to continue monitoring. If it is Vlow or higher, the time counter is incremented in S3. If the time counter τ is less than the constant value τmin in the determination process of S4, the process returns to the determination process S2 to determine the magnitude of the voltage again. If the time counter τ is equal to or greater than a certain value τmin, a command to turn off the bypass switch 220 is issued in S5, and an inverter activation command is given to the converter controller 234 in S6.

  Thereby, the voltage regulator 100 is restarted. By providing such a processing flow, when the voltage regulator 100 is temporarily stopped at the time of a system failure or power failure, the system state is sufficiently stabilized without restarting more quickly than necessary after the system recovery ( After the load or solar power is restarted), the voltage regulator 100 is restarted. That is, the system recovery is detected, the system state is confirmed to be stable, and the system is restarted.

  FIG. 7 shows a processing flow of the loss reduction algorithm of the voltage regulator. Where V is the voltage of the distribution system, Vmin is the minimum dead band voltage setting value that serves as a guide for shutdown, Vmax is the maximum dead band voltage setting value that serves as a guide for shutdown, τ is the time counter, and τmin is the timer setting value. .

  In S11, the time counter τ is reset to zero. In S12, it is monitored whether or not the system voltage V is in the dead band range of Vmin or more and Vmax or less. As a result, if it is outside the dead band, the process returns to the beginning to continue monitoring. If it is within the dead zone, the time counter is incremented in S13. If the time counter τ is less than the constant value τmin in the determination process of S14, the process returns to the determination process S12 to determine the magnitude of the voltage again. If the time counter τ is greater than or equal to the constant value τmin, an inverter stop command is given to the converter controller 234 in S15, and a command to turn on the bypass switch 220 is issued in S16.

  Thereby, the voltage regulator 100 is stopped. By providing such a processing flow in the voltage regulator 100, there is an effect that the loss generated in the converter part of the voltage regulator can be reduced and the life of the voltage regulator can be extended.

  According to the voltage regulator of the present embodiment, even when a distributed power source is newly installed in the distribution system, the voltage of the distribution system can be maintained within a specified range without changing the distribution line path or the system configuration. Moreover, it can be applied as a pole transformer having such a voltage adjustment function. Furthermore, it is possible to configure a power distribution system with good facility efficiency by installing it in a power distribution system having a large voltage fluctuation and reducing the amount of voltage fluctuation.

The block diagram of the voltage regulator by one Example of this invention. The block diagram of the distribution system which applied the voltage regulator. Explanatory drawing which showed distribution of the voltage drop amount of a power distribution system. The graph which showed the example of the voltage distribution of each component of a power distribution system. The graph which showed the example of the result of the voltage control by a voltage regulator. The processing flow figure of the restart algorithm of a voltage regulator. The processing flowchart of the loss reduction algorithm of a voltage regulator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... High voltage distribution line, 11 ... Distribution substation, 12 ... Distribution system, 20 ... Low voltage distribution line, 21 ... Service line, 22 ... Consumer, 23 ... Distributed power sources, such as photovoltaic power generation, 100 ... Voltage regulator, 110 ... pole transformer, 120 ... voltage regulator, 211, 212 ... series transformer, 213 ... voltage sensor, 214 ... protection device, 220 ... bypass switch, 230v regulator voltage generator, 231 ... inverter, 232 ... converter, 233 DESCRIPTION OF SYMBOLS ... DC capacitor, 234 ... Converter control apparatus, 240 ... Adjustment voltage control circuit, 241 ... Voltage calculation part, 242 ... Adjustment voltage calculation part, 243 ... Target voltage setting part.

Claims (10)

In a voltage regulator for a power system composed of a pole transformer connecting a high-voltage distribution system and a low-voltage distribution system, and a consumer load and a distributed power source connected to the low-voltage distribution system,
Based on the series transformer connected in series to the secondary side of the pole transformer, the adjustment voltage control circuit that receives the voltage measurement value of the low-voltage distribution system, and the output of the adjustment voltage control circuit An adjustment voltage generation circuit for generating an adjustment voltage on the secondary side of the series transformer is provided. In a voltage regulator for a power system composed of a pole transformer connecting a high-voltage distribution system and a low-voltage distribution system, and a consumer load and a distributed power source connected to the low-voltage distribution system,
Input the voltage measurement value of the low-voltage distribution system, the series transformer connected in series to the secondary side of the pole transformer, the bypass switch connected between the secondary terminals of the series transformer An adjustment voltage control circuit for generating an adjustment voltage on the secondary side of the series transformer based on the output of the adjustment voltage control circuit, and the adjustment voltage generation according to the voltage of the low-voltage distribution system And a protection circuit that opens or closes the bypass switch in order to start or stop the circuit.   3. The adjustment voltage control circuit according to claim 1, wherein the adjustment voltage control circuit includes a sensor that detects a voltage of the low-voltage distribution system, a voltage calculation unit that calculates a voltage effective value from a voltage measurement value detected by the sensor, and a target voltage in advance. A voltage regulator comprising: a target voltage setting unit to be set; and an adjustment voltage calculation unit that calculates the adjustment voltage from the voltage effective value and the target voltage. In the voltage regulation method of the power system, connecting the high-voltage distribution system and the low-voltage distribution system with a pole transformer, and connecting the consumer load and the distributed power source to the low-voltage distribution system,
Obtain the effective value of the voltage from the measured value of the line voltage of the low-voltage distribution system, control the adjustment voltage generation circuit based on the deviation between the effective value and a predetermined target voltage, the secondary side of the pole transformer A voltage adjusting method comprising: supplying an output of the adjustment voltage generating circuit to a secondary side of the series transformer so that a primary side voltage of a series transformer connected to the primary side of the inverter is equivalent to the deviation. In the voltage regulation method of the power system, connecting the high-voltage distribution system and the low-voltage distribution system with a pole transformer, and connecting the consumer load and the distributed power source to the low-voltage distribution system,
Obtain the effective value of the voltage from the measured value of the line voltage of the low-voltage distribution system, control the adjustment voltage generation circuit based on the deviation between the effective value and a predetermined target voltage, the secondary side of the pole transformer The output of the regulated voltage generation circuit is supplied to the secondary side of the series transformer so that the primary side voltage of the series transformer connected to the primary side corresponds to the deviation, and according to the voltage of the low-voltage distribution system A voltage adjustment method comprising: opening or closing a bypass switch between the adjustment voltage generation circuit and the series transformer.   6. The voltage adjustment method according to claim 4, wherein the target voltage is set based on a load contract capacity and a distributed power contract capacity connected to a low voltage system. 6. The voltage adjustment method according to claim 4, wherein the target voltage is set according to equation (1).
Target voltage = load contract capacity / (load contract capacity + distributed power contract capacity) x 12 + 95 (1)   6. The adjustment voltage generation circuit is activated or the bypass switch is opened when a time during which the voltage of the low-voltage distribution system exceeds a minimum voltage set value becomes longer than a timer set value. Voltage adjustment method.   6. The bypass switch according to claim 5, wherein when the voltage of the low voltage distribution system is larger than the dead band minimum voltage set value and smaller than the dead band maximum voltage set value, the duration is longer than the timer set value. A voltage adjustment method characterized by: A power system composed of a pole transformer connecting a high-voltage distribution system and a low-voltage distribution system, and a consumer load or a distributed power source connected to the low-voltage distribution system,
The said pole transformer includes the voltage regulator in any one of Claims 1-3, and is comprised, The electric power system characterized by the above-mentioned.

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