JP2006094635A - Tidal current control method of low-voltage distribution system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tidal current control method of a low-voltage distribution system that can control a tidal current between low-voltage distribution line passages connected to different transformers. <P>SOLUTION: A tidal current control device 5 constituted by forming a connecting point 14 that closes the passage of an active filter 6 at the stop of the filter that is arranged in parallel with a primary winding 12 of the series transformer 11 of the series-type active filter 6 composed a converter 8, an inverter 10, a filter 13 and the series transformer 11 is connected between the low-voltage distribution systems 3, 4, and the tidal current of each low-voltage distribution system is controlled by making a corrective current flow between the low-voltage distribution systems 3, 4 through the tidal current control device 5. The tidal current control device 5 is constituted by connecting the series-type active filter 6 and a zero-phase current suppression device 7 in series. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power flow control method for a low voltage distribution system.

  The low-voltage distribution system in the factory premises is configured by connecting low-voltage distribution lines to the secondary sides of a plurality of transformers, and loads such as processing machines are dispersedly connected to the low-voltage distribution lines. The capacity of the transformer is determined according to the capacity of the load, but in the past, there was a margin for each distribution system considering the case of overload, and it is always very light load such as lighting etc. Regardless, large capacity transformers have been provided in preparation for the occasional operation of large equipment connected to the same low voltage distribution line. For this reason, there is a problem that the overall facility becomes excessive and the utilization rate is low, so the efficiency is low and the facility cost increases.

  In addition, factories are frequently reviewed due to economic conditions such as rapid technological innovation, shortening of product life and competition with overseas companies, and the addition and replacement of processing machines and changes in layout have come to be performed. For this reason, the load connected to each low-voltage distribution line changes significantly, and the load that has been properly distributed to each transformer at the time of facility planning becomes unbalanced, and each time it is required to respond. In addition, there is a problem that a large capacity load facility is operated only for a short period of time, and it is necessary to reinforce the low voltage distribution line and increase the transformer for the operation of the facility. . On the other hand, an emphasis is placed on high value-added work, and there is a strong demand for equipment in such processes to transmit power without interruption.

  For example, as shown in FIG. 11, low voltage distribution lines 44 and 45 are respectively connected to secondary sides of two transformers 42 and 43 having a rated capacity of 3000 A, and a load of 3000 A is connected to each of the low voltage distribution lines 44 and 45. In a factory facility in which 46 and a 1000 A load 47 are connected, even if an attempt is made to add a 1000 A load 48 to the low-voltage distribution line 44, the transformer 42 is overloaded and cannot be added. In order to add and operate the load 48 of 1000 A, it has been necessary to replace the transformer 42 and newly install a low-voltage distribution line from the transformer 42 to the load of 1000 A added.

  In such a case, if a correction current can be passed between the low-voltage distribution lines connected to different transformers and the power flow in each low-voltage distribution line can be controlled, it is necessary to allow the transformer to have an excessive capacity when newly installing low-voltage distribution equipment. This eliminates the need to add a transformer or newly install a low-voltage distribution line when adding a load or replacing a large-capacity load. As a technique for controlling the power flow in the distribution line, for example, a series-type active filter as disclosed in Patent Document 1 is connected between the distribution lines, and each distribution line is caused to flow a commercial frequency correction current between the distribution lines. There is a known method for controlling the current flow. According to the method disclosed in Patent Document 1, it is possible to control the current of each distribution line and to reduce the power loss of the distribution line by balancing the currents of the distribution lines.

However, what is shown in this Patent Document 1 is intended for a plurality of high-voltage distribution lines connected to a single transformer, and the current of the distribution line is controlled by controlling the power flow at the end of the distribution line far from the transformer. It is intended to level out, and it is not considered to control power flow between low-voltage distribution lines connected to different transformers. In addition, the low-voltage distribution system has characteristics that the high-voltage distribution system is not grounded, but is always grounded on the secondary side of the transformer, or that the short-circuit impedance of the transformer is low. There is a problem that it cannot be applied to a low voltage distribution system.
JP 2002-125318 A

  The present invention has been made to solve the above-described problems and to provide a power flow control method for a low-voltage distribution system that can control a power flow between low-voltage distribution lines connected to different transformers.

  The invention of claim 1 completed to solve the above-described problem is that when the active filter is stopped in parallel with the primary winding of the series transformer of the series-type active filter comprising a converter, an inverter, a filter, and a series transformer. A power flow control device configured by providing a closing contact is connected between the low-voltage distribution systems, and the power flow of each low-voltage distribution system is controlled by supplying a correction current between the low-voltage distribution systems through the power flow control device. Is. In the invention of claim 1, the power flow control device is configured by connecting a zero-phase current suppression device in series with a series-type active filter. The invention of claim 2 has a fuse in series with the power flow control device. The invention of claim 3 is connected.

  The invention of claim 4 made to solve the same problem is to detect the load current of each low-voltage distribution system in any one of the inventions of claims 1 to 3, and to provide a transformer of the low-voltage distribution system having a low load current. In order to solve the same problem, the invention of claim 5 is characterized in that in the invention of any one of claims 1 to 3, the power flow control device is installed downstream of the low-voltage distribution system. The correction current is calculated based on the load current that is connected and detected in the upstream portion of each low-voltage distribution system. Further, in order to solve the same problem, the invention of claim 6 is the invention of any one of claims 1 to 3, wherein a circuit breaker is provided on the high voltage side and the low voltage side of each transformer of the low voltage distribution system. The circuit breaker on the low pressure side is opened when the circuit breaker is opened.

  In the first aspect of the invention, the load current of each transformer can be optimally distributed by shifting the correction current between the low-voltage distribution systems by the power flow control device connected between the low-voltage distribution systems. There are advantages that can be minimized. The active filter that constitutes the power flow control device is provided with a contact that short-circuits the primary winding of the series transformer when the active filter is stopped, thus avoiding damage to the main circuit elements even if voltage is applied to the low-voltage distribution line when the active filter is stopped. be able to. In the invention of claim 2, since the zero-phase current suppression device is connected in series with the series-type active filter, the transition of the zero-phase current through the power flow control device is suppressed, and there is a leakage accident in any of the low-voltage distribution lines. In such a case, the low-voltage distribution line can be specified.

  When the power flow control device is connected, current is also supplied to the low-voltage distribution system from other transformers, and the maximum short-circuit current increases. Therefore, it is necessary to review the short-circuit breaking capacity of the circuit breaker and the like accordingly. Replacing such equipment would require considerable cost, but in the invention of claim 3, a fuse is connected in series with the power flow control device, so that in the event of an accident, it will be disconnected by the fuse and shut off. There is an advantage that it is not necessary to review or replace the device such as a vessel.

  Furthermore, in the invention of claim 4, since the load current of each low-voltage distribution system is detected and the transformer of the low-voltage distribution system having a low load current is disconnected, it is not necessary to excite the light load transformer, There is an advantage that loss can be reduced. In the invention of claim 5, the power flow control device is connected to the downstream part of the low-voltage distribution system, and the correction current is calculated based on the load current detected in the upstream part of each low-voltage distribution system. The line can optimally share the load current. Thus, there is an advantage that electric power can be supplied to a load that cannot be supplied by a single transformer without replacing the transformer or newly installing or adding a low-voltage distribution line.

  In the invention of claim 6, circuit breakers are provided on the high voltage side and the low voltage side of the transformer of each low voltage distribution system, and the circuit breaker on the low voltage side is opened when the circuit breaker on the high voltage side is opened. When the protection device is activated due to an abnormal condition and the high-voltage circuit breaker is opened, the low-voltage circuit breaker is also opened, the abnormal transformer is disconnected, and the power flow control device is installed in the low-voltage distribution system from which the transformer is disconnected. There is an advantage that power can be transmitted uninterrupted by supplying power from other transformers. In addition, when inspecting the transformer, if the circuit breaker on the high voltage side is opened by opening the circuit breaker, the circuit breaker on the low voltage side can also be opened, and the load can be transmitted uninterrupted, and the transformer is disconnected from the grid. There is an advantage that it can be safely checked in a voltage state.

Next, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
FIG. 1 is a connection diagram showing a basic embodiment of the present invention. A power flow control device 5 is connected between the low-voltage distribution lines 3 and 4 connected to the secondary sides of the transformers 1 and 2, respectively. The power flow control device 5 is composed of a series-type active filter 6 and a zero-phase current suppressing device 7 (not shown). The series-type active filter 6 includes a converter 8 that converts AC power into DC, a capacitor 9 that is connected to the output side of the converter 8, an inverter 10 that converts DC power of the converter 8 into AC power, and an output waveform of the inverter 10 And a filter 13 that is sent to the primary winding 12 of the series transformer 11.

  The primary winding 12 of the series transformer 11 is connected to a normally closed contact 14 of an electromagnetic contactor that short-circuits the secondary winding 15 of the series transformer 11 and the zero-phase current suppressing device 7 in series. Connected and connected between the low voltage distribution lines 3 and 4. The electromagnetic contactor including the normally closed contact 14 is driven by a control device (not shown) of the active filter 6, and the input side of the converter 8 is connected to one low-voltage distribution line 3. The zero-phase current suppression device 7 can be a common mode reactor configured by winding three windings 17a, 17b, and 17c on a common iron core 16 as shown in FIG. As shown in FIG. 3, the secondary windings of three single-phase transformers 18a, 18b, and 18c can be connected in parallel and terminated with a termination impedance 19.

  In the figure, reference numerals 20 and 21 denote circuit breakers provided on the primary side of the transformers 1 and 2, which are connected to the high voltage distribution line 22 to open and close and protect the input side of the transformers 1 and 2. A protective relay is provided to open the circuit breakers 20 and 21 in the event of an abnormality of 1 or 2. The transformers 1 and 2 are also provided with a protection device for detecting an abnormality such as overheating, and the circuit breakers 20 and 21 are opened by the operation of the protection device. Reference numerals 23 and 24 are circuit breakers provided on the secondary side of the transformers 1 and 2 for opening / closing and protecting the low-voltage distribution lines 3 and 4 and incorporating a mechanism for tripping in the case of overload and overcurrent. ing.

  A load (not shown) is connected to each of the low-voltage distribution lines 3 and 4 in a state where the power flow control device 5 configured as described above is connected between the low-voltage distribution lines 3 and 4. When the circuit breakers 23 and 24 on the side are closed, power is supplied to a load (not shown). If the normally closed contact 14 of the magnetic contactor is closed while the active filter 6 is not operating, the primary winding 12 of the series transformer 11 is short-circuited and the secondary winding 15 of the series transformer 11 is low. The impedance becomes low, and the low-voltage distribution lines 3 and 4 are connected by the zero-phase current suppressing device 7. As a result, normal-phase and reverse-phase currents flow through the zero-phase current suppression device 7, and the load currents of the low-voltage distribution lines 3 and 4 are averaged. However, the degree of averaging is not sufficient due to the presence of the impedance of the transformers 1 and 2, the leakage reactance of the zero-phase current suppression device 7, and the residual reactance of the secondary winding 15.

  If the active filter 6 is operated while the normally closed contact 14 of the magnetic contactor is opened, the phase, direction and magnitude of the current flowing between the low voltage distribution lines 3 and 4 can be controlled by controlling the active filter 6. Can be controlled. When the capacities of the transformers 1 and 2 are the same, the load current can be averaged, and when the capacities of the transformers 1 and 2 are different, the sharing ratio of the transformers 1 and 2 can be controlled. In addition, when a leakage accident occurs in any of the low-voltage distribution lines 3 and 4, the flowing zero-phase current is suppressed by the zero-phase current suppressing device 7 and does not flow to the other low-voltage distribution line 4 or 3. The low voltage distribution line 3 or 4 in which the electric leakage accident has occurred can be specified.

  When operating the active filter 6 to perform power flow control, the inverter 10 is first operated in the 0V output mode, the electromagnetic contactor is operated to open the normally closed contact 14, and then the inverter 10 is set to the normal operation mode. . When the active filter 6 is not operating and the normally closed contact 14 of the magnetic contactor is closed, the AC power supplied to the converter 8 is converted to DC by the converter 8 and stored in the capacitor 9, and the inverter 10 This can be converted into alternating current. When the inverter 10 is operated in the 0V output mode, the main circuit switching elements of the plus side 3 arm or the minus side 3 arm of the bridge circuit constituting the inverter 10 are simultaneously turned on, whereby the primary winding 12 of the series transformer 11 is filtered. 13 will be short-circuited.

  This is done when the active filter 6 is operated in order to protect the main circuit elements constituting the active filter 6. That is, when a voltage is applied to the power flow control device 5 while the inverter 10 is not operating, a current that bypasses the low-voltage distribution lines 3 and 4 flows in the secondary winding 15 of the series transformer 11. When the normally closed contact 14 is not provided, a current induced in the primary winding 12 by this current flows into the inverter 10 and is rectified by the main circuit element to charge the capacitor 9 to generate a high voltage. This may damage the main circuit element. By short-circuiting the primary winding 12 with the normally closed contact 14, current induced in the primary winding 12 can be prevented from flowing into the inverter 10, and damage to the main circuit element can be avoided. Even when the power flow control by the active filter 6 is stopped, the inverter 10 is first shifted to the 0 V output mode, and then the electromagnetic contactor is opened and the primary winding 12 is short-circuited by the normally closed contact 14.

  FIG. 4 is a single line diagram showing an embodiment of the invention of claim 4, wherein the currents in the low-voltage distribution lines 3 and 4 downstream from the point where the power flow control device 5 is connected to the low-voltage distribution lines 3 and 4. Current sensors 25 and 26 for detection are provided. The detection signals of the current sensors 25 and 26 are sent to the control device 27, and the control device 27 controls the high-voltage circuit breakers 20 and 21 and the low-voltage circuit breakers 23 and 24 based on the detection signals. When the load current of the low-voltage distribution line 3 decreases and the detection signal of the current sensor 25 falls below a preset value, the detection signal of the current sensor 26 is checked, and if the total current can be supplied from the transformer 2, it is cut off The device 20 and the circuit breaker 23 are opened. Electric power is supplied to the load downstream of the low-voltage distribution line 3 from the transformer 2 via the power flow control device 5.

  At this time, the power flow control device 5 does not necessarily need to operate the active filter 6 as long as the normally closed contact 14 is closed. As a result, when the load is light, it can be operated with one transformer 2, and the light load transformer 1 can be disconnected, so that the loss of the transformer can be reduced. Similarly, when the load current of the low voltage distribution line 4 decreases and the detection signal of the current sensor 26 falls below a certain value, the total current of the low voltage distribution lines 3 and 4 can be supplied from the transformer 1 as well as the circuit breaker 21. The circuit breaker 24 is opened, and power is supplied to the load downstream of the low-voltage distribution line 4 from the transformer 1 via the power flow control device 5.

  FIG. 5 is a single line diagram showing an embodiment of the invention of claim 5, and the power flow control device 5 is close to the point where the large capacity load 28 downstream of the low voltage distribution line 3 is connected and the low voltage distribution line 4. Connected between the points to be. The low-voltage distribution lines 3 and 4 are provided with current sensors 29 and 30 for detecting the current of the low-voltage distribution lines 3 and 4 at the most upstream part, and the detection signals of the current sensors 29 and 30 are sent to the control device 31. The difference between the current in the low-voltage distribution line 3 and the current in the low-voltage distribution line 4 is calculated. Data on the difference between the calculated current of the transformer 1 and the current of the transformer 2 is sent to the power flow control device 5 through the communication line 32. If this data transmission is performed by serial communication using digital signals, it is advantageous that the communication line 32 can be installed at low cost.

  The control device 31 calculates the difference between the current of the transformer 1 and the current of the transformer 2, but since the effective component and the invalid component are calculated, the power flow control device 5 receives the data through the communication line 32. When the capacities of the transformers 1 and 2 are the same, the values are controlled to be lower. As a result, the difference between the current in the most upstream part of the low-voltage distribution line 3 and the current in the most upstream part of the low-voltage distribution line 4 is reduced, and the transformers 1 and 2 and the low-voltage distribution line 3 and 4 are connected to the large capacity load 28 to be connected. The current will be shared equally. Therefore, power is supplied to the load 28 having a capacity that cannot be supplied by a single transformer 1 or 2 without replacing the transformer 1 or 2 or constructing the low-voltage distribution line 3 or 4. be able to.

  FIG. 6 is a single line diagram showing an embodiment of the invention of claim 6 and is configured such that when the high-pressure circuit breaker 20 or 21 is opened, the low-pressure circuit breaker 23 or 24 is opened in conjunction therewith. Has been. When an abnormality occurs in the transformer 1 or 2 with such a configuration, the protective device provided in the transformer 1 or 2 or the protective relay attached to the high-voltage circuit breaker 20 or 21 is activated. The circuit breaker 20 or 21 on the side is opened. As a result, the circuit breaker 23 or 24 on the low voltage side is also opened and the transformer 1 or 2 is disconnected, and power flow control is applied to the load connected to the low voltage distribution line 3 or 4 from which the transformer 1 or 2 is disconnected. Power is supplied from the transformer 2 or 1 through the device 5.

  Therefore, even if an abnormality occurs in the transformer 1 or 2 in the load connected to the low-voltage distribution line 3 or 4, power is supplied from the other transformer 2 or 1 connected through the power flow control device 5. It is possible to transmit power without a power failure. Since the abnormal transformer 1 or 2 is completely disconnected, no fault current is supplied from the low-voltage distribution line 3 or 4. When the transformer 1 or 2 is inspected or replaced, if the circuit breaker 20 or 21 on the high voltage side is operated and opened, the circuit breaker 23 or 24 on the low voltage side is also opened, and the load is transmitted without interruption. The transformer 1 or 2 can be safely inspected or replaced in a no-voltage state disconnected from the system.

  In the above-described embodiment, if the ground phase of the transformers 1 and 2 is connected and grounded at one place so that the zero-phase current can be managed, the low-voltage in which the leakage accident has occurred without providing the zero-phase current suppressing device The distribution line 3 or 4 can be specified. Moreover, in the said embodiment, although each low voltage distribution line is connected to the secondary side of a separate transformer, a tidal current control apparatus is provided between the downstream parts of each low voltage distribution line connected to one transformer. It can also be connected to level the current in the low voltage distribution line. In such a case, since there is only one ground point, it is not necessary to provide the zero-phase current suppressing device 7.

  FIG. 7 is a single line diagram showing the first embodiment, and the low voltage distribution lines 3 and 4 are connected to the secondary side of the transformers 1 and 2 having a rated capacity of 1500A. The primary sides of the transformers 1 and 2 are connected to the high voltage distribution line 22 via the circuit breakers 20 and 21, and the circuit breakers 23 and 24 are provided on the secondary side of the transformers 1 and 2. A load 33 of 1200 A and a load 34 of 600 A are connected to the low voltage distribution lines 3 and 4, respectively, and a power flow control device 5 is connected between the low voltage distribution lines 3 and 4. When the power flow control device 5 is not connected, the transformers 1 and 2 supply currents of 1200A and 600A, respectively, as shown in parentheses, but when the power flow control device 5 is connected, the power flow control device 5 reduces the pressure. A 300 A correction current flows from the distribution line 4 to the low-voltage distribution line 3, and both the transformers 1 and 2 share 900A. Thus, the operating rates of the transformers 1 and 2 can be made uniform, and the overall loss can be reduced.

  FIG. 8 is a single line diagram showing Example 2, except that the rated capacity of transformer 1 is 3000 A, the rated capacity of transformer 2 is 1000 A, and loads 33 and 34 are both 1000 A. Is the same. In the state where the power flow control device 5 is not connected, both the transformers 1 and 2 supply a current of 1000 A as shown in parentheses. However, in the state where the power flow control device 5 is connected, the power flow control device 5 supplies the low-voltage power distribution. A correction current of 500 A is supplied from the line 3 to the low-voltage distribution line 4, and the transformer 1 shares 1500 A and the transformer 2 shares 500 A. Thus, both the transformers 1 and 2 share the current of half of the rating, the operating rates of the transformers 1 and 2 can be made uniform, and the overall loss can be reduced.

  FIG. 9 is a single line diagram showing the third embodiment, which is basically the same as the first embodiment, but the rated capacities of the transformers 1 and 2 are both 3000 A, the load 33 is 3000 A, and the load 34 is 1000 A. In addition, a load 35 of 1000 A is further connected to the low-voltage distribution line 3. If the load 35 is not connected when the power flow control device 5 is not connected, the transformers 1 and 2 supply currents of 3000 A and 1000 A, respectively, as shown in parentheses. Since the transformer 1 is overloaded, it cannot be connected. If the load 35 is connected in a state where the power flow control device 5 is connected, the power flow control device 5 causes a correction current of 1500 A to flow from the low-voltage distribution line 4 to the low-voltage distribution line 3, and the transformers 1 and 2 That is, 5000A, which is a half, is shared by 2500A.

  The third embodiment is a case where the load 35 of 1000 A is added to the load 33 of 3000 A. However, the case where the load 33 of 3000 A is replaced with a load of 4000 A can be similarly handled. The load 35 to be added or the load 33 to be replaced needs to be connected to the connection point between the low-voltage distribution line 3 and the power flow control device 5, otherwise, the current flowing in the low-voltage distribution line 3 will exceed the initial capacity. Occurs. Since the load current can be shared by the transformers 1 and 2 in this way, the transformer 1 can be replaced or the low-voltage distribution line 3 can be used for loads 33 and 35 that cannot be supplied by a single transformer 1 alone. There is an advantage that power can be supplied without newly installing or adding.

  FIG. 10 is a single line diagram showing the fourth embodiment, in which the low-voltage distribution system is divided into three systems. The configuration of each distribution system is the same as that of the first embodiment, and the low voltage distribution lines 3, 4, 37 are connected to the secondary side of the transformers 1, 2, 36, and between the low voltage distribution lines 3, 4 Tidal flow control devices 5 and 38 are connected between the low voltage distribution lines 4 and 37. In the figure, 39 is a circuit breaker on the high voltage side of the transformer 36, 40 is a circuit breaker on the low voltage side, and 41 is a load connected to the low voltage distribution line 37. The rated capacity of the transformer 1 is 3000A, the rated capacity of the transformers 2 and 36 is 1000A, and the loads 33, 34, and 41 of 1000A, 800A, and 700A are connected to the low-voltage distribution lines 3, 4, and 37, respectively. .

  When the power flow control devices 5 and 38 are not connected, the transformers 1, 2 and 36 supply currents of 1000 A, 800 A and 700 A, respectively, as shown in parentheses, but the power flow control devices 5 and 38 are connected. In this state, the power flow control device 5 flows a correction current of 500 A from the transformer 1 to the low voltage distribution line 4, and the power flow control device 38 flows a correction current of 200 A from the low voltage distribution line 4 to the low voltage distribution line 37. In this way, the transformers 1, 2 and 36 all share a half of the rated current, so that the operating rates of the transformers 1, 2 and 36 can be equalized, and the overall loss is reduced. Can do.

  Although the fourth embodiment has three low-voltage distribution systems, it is also possible to sequentially connect a larger number of low-voltage distribution systems using a power flow control device. As a result, when a load can be covered by one transformer on a holiday, etc., the load current can be supplied from one transformer to each low-voltage distribution line, and all other transformers can be disconnected, reducing loss. be able to. Moreover, the transformer can be operated in an efficient state by increasing or decreasing the number of transformers to be operated according to the load. In addition, when installing a new facility or renewing a transformer, it is only necessary to consider the relationship between the total capacity of the transformers connected by the power flow control device and the load capacity. There is an advantage that equipment costs can be reduced.

It is a connection diagram which shows basic embodiment of this invention. It is a block diagram which shows the example of a zero phase current suppression apparatus. It is a block diagram which shows another example of a zero phase current suppression apparatus. FIG. 6 is a single line diagram showing an embodiment of the invention of claim 4. FIG. 6 is a single line diagram showing an embodiment of the invention of claim 5. It is a single line figure which shows embodiment of invention of Claim 6. 1 is a single line diagram illustrating Example 1. FIG. 6 is a single line diagram showing Example 2. FIG. 6 is a single line diagram showing Example 3. FIG. 10 is a single line diagram showing Example 4. FIG. It is a single line figure which shows the example of the conventional low voltage power distribution system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Transformer 3, 4 Low voltage distribution line 5 Power flow control apparatus 6 Active filter 7 Zero phase current suppression apparatus 8 Converter 9 Capacitor 10 Inverter 11 Series transformer 12 Series transformer primary winding 13 Filter 14 Electromagnetic contactor usual Closed contact 15 Secondary winding of series transformer 16 Iron core 17a, 17b, 17c Winding 18a, 18b, 18c Single phase transformer 19 Termination impedance 20, 21 High voltage side circuit breaker 22 High voltage distribution line 23, 24 Low voltage side Circuit breaker 25, 26 Current sensor 27 Control device 28 Large capacity load 29, 30 Current sensor 31 Control device 32 Communication line 33, 34, 35 Load 36 Transformer 37 Low voltage distribution line 38 Power flow control device 39 High voltage side circuit breaker 40 Low pressure Side circuit breaker 41 Load

Claims (6)

  Connected between low-voltage distribution systems with a power flow control device configured with a contact that closes when the active filter is stopped in parallel with the primary winding of the series transformer of the series-type active filter consisting of a converter, inverter, filter, and series transformer A power flow control method for a low-voltage distribution system, wherein the power flow of each low-voltage distribution system is controlled by supplying a correction current between the low-voltage distribution systems through the power flow control device.   2. The power flow control method for a low-voltage distribution system according to claim 1, wherein the power flow control device is configured by connecting a zero-phase current suppression device in series with a series active filter.   The power flow control method for a low-voltage distribution system according to claim 1 or 2, wherein a fuse is connected in series with the power flow control device.   4. The method for controlling a power flow in a low-voltage distribution system according to claim 1, wherein a load current of each low-voltage distribution system is detected and a transformer of the low-voltage distribution system having a low load current is disconnected.   4. The low-voltage distribution system according to claim 1, wherein a power flow control device is connected to a downstream portion of the low-voltage distribution system, and a correction current is calculated based on a load current detected in an upstream portion of each low-voltage distribution system. Tidal current control method. 4. The low voltage distribution system according to claim 1, wherein circuit breakers are provided on the high voltage side and the low voltage side of the transformer of each low voltage distribution system, and the low voltage circuit breaker is opened when the high voltage circuit breaker is opened. System power flow control method.

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