Microgrid system

Abstract

To provide a micro-grid system with reduced investment cost.SOLUTION: A micro-grid system 100 includes: a storage battery device (effective power supply device) 40 connected to a high-voltage distribution line 3 and configured to supply effective power; and a reactive power compensation device 30 connected to the high-voltage distribution line 3 and configured to supply reactive power. The use of both the storage battery device 40 and the reactive power compensation device 30 reduces a construction cost of the micro-grid system 100.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This specification discloses technologies related to a microgrid system.

Background Art

[0002] Patent Document 1 discloses a microgrid system including a power generation device and a battery device. The microgrid system of Patent Document 1 includes a thermal power generation device and a natural energy power generation device as power generation devices. In Patent Document 1, the operation timing of the thermal power generation device and the natural energy power generation device is controlled to generate power at a constant power by the thermal power generation device, thereby improving the fuel efficiency of the thermal power generation device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a microgrid system including a power generation device and a battery device as in Patent Document 1, in order to reliably supply power to consumers, it is necessary to design the power generation device, the battery device, etc. to be larger than the normally required capacity. In particular, when starting a power load such as a motor, a current several times the rated power may flow through the distribution system. In preparation for such a case, it is necessary to design the capacity of the power generation device, the battery device, etc. with a margin, and it is necessary to select a device with a larger capacity than the normally required capacity. As a result, it is necessary to select a large-sized device, and the cost of securing an equipment installation space, the equipment cost, and the investment cost for constructing the microgrid system increase. This specification provides a technology for realizing a microgrid system with suppressed investment costs.

Means for Solving the Problems

[0005] The microgrid system disclosed herein is formed within a power distribution system. This microgrid system includes an active power supply device connected to a high-voltage distribution system and supplying active power, and a reactive power compensation device connected to a high-voltage distribution system and supplying reactive power. [Brief explanation of the drawing]

[0006] [Figure 1] The microgrid system of the first embodiment is shown. [Figure 2] A microgrid system of the second embodiment is shown. [Modes for carrying out the invention]

[0007] The microgrid systems disclosed herein are formed within a distribution system supplied with electricity from a power plant. The microgrid systems can be connected to and disconnected from the power plant's distribution lines by switches. Therefore, while the microgrid systems are connected to the power plant's distribution lines, consumers within the microgrid can utilize electricity from the power plant. When the microgrid systems are disconnected from the power plant's distribution lines, consumers within the microgrid can utilize electricity generated within the microgrid.

[0008] A microgrid system is equipped with active power supply devices and reactive power compensation devices. The active power supply devices are connected to the high-voltage distribution system within the microgrid. That is, they are located downstream of the switches that connect to and disconnect the distribution lines from the power plant. Examples of active power supply devices include power generators and battery storage systems. Reactive power compensation devices are also connected to the high-voltage distribution system within the microgrid. Examples of reactive power compensation devices include SVCs, SVGs, TSCs, and TCRs.

[0009] A reactive power compensation device can supply reactive power to a high-voltage distribution system when the voltage of the high-voltage distribution system falls outside a predetermined range, thereby restoring the voltage of the high-voltage distribution system to within a predetermined range. For example, when a power load such as a motor is started, a large current flows through the high-voltage distribution system temporarily, and the voltage of the high-voltage distribution system may drop outside a predetermined range. In such cases, the voltage of the high-voltage distribution system can be maintained within a predetermined range by supplying reactive power from the reactive power compensation device to the high-voltage distribution system. Furthermore, a microgrid system may be equipped with a high-voltage power factor correction capacitor connected to the high-voltage distribution system within the microgrid. A high-voltage power factor correction capacitor can also supply voltage to the high-voltage distribution system and maintain the voltage of the high-voltage distribution system within a predetermined range. By using a high-voltage power factor correction capacitor, an even smaller (smaller) reactive power compensation device can be used.

[0010] As described above, by placing a reactive power compensation device within the microgrid, the voltage of the high-voltage distribution system can be maintained within a predetermined range. Typically, when starting a power load such as a motor, a large current (several times the normal current) flows through the high-voltage distribution system compared to normal operation. Therefore, the voltage of the high-voltage distribution system tends to drop when starting a power load. Conventionally, when designing a microgrid, a large-capacity active power supply device (such as a power generator) is used to stably supply power when starting a power load. However, a large-capacity active power supply device can be said to be over-engineered during normal operation. The above microgrid system uses both an active power supply device and a reactive power compensation device, allowing for the selection of an active power supply device that matches the normal operation of the power load. Therefore, the above microgrid system can use a small-capacity (small-sized) active power supply device. As a result, the installation space costs and equipment costs for constructing the microgrid system can be reduced. [Examples]

[0011] (First embodiment) Referring to Figure 1, the microgrid system 100 will be described. The microgrid system 100 includes a battery storage device 40 and a reactive power compensation device 30 connected to a high-voltage distribution line 3 supplied with power from a power plant 2. The battery storage device 40 is an example of an active power supply device. The high-voltage distribution line 3 is equipped with automatic switches 5 and 7 for turning the power supply on and off. The battery storage device 40 and the reactive power compensation device 30 are connected to the high-voltage distribution line 3 between the automatic switches 5 and 7. Therefore, a microgrid 10 is formed between the automatic switches 5 and 7. Consumers within the microgrid 10 can use their electrical equipment even when the automatic switches 5 and 7 are open (power supply off) due to the power supply from the battery storage device 40. Within the microgrid 10, low-voltage distribution lines 12a, 14a and 16a are connected to the high-voltage distribution line 3, and consumers receive power from the low-voltage distribution lines 12a, 14a and 16a.

[0012] High-voltage distribution line 3 has three high-voltage lines (three-phase lines) 4, 6, and 8. Low-voltage distribution lines 12a, 14a, and 16a are connected to two of the first line (first phase) 4, second line (second phase) 6, and third line (third phase) 8. Low-voltage distribution lines 12a, 14a, and 16a can be classified into three groups according to the high-voltage lines they are connected to. Specifically, the low-voltage line of the first group 16 (first low-voltage distribution line 16a) is connected to the first line 4 and the second line 6. The low-voltage line of the second group 14 (second low-voltage distribution line 14a) is connected to the second line 6 and the third line 8. The low-voltage line of the third group 12 (third low-voltage distribution line 12a) is connected to the first line 4 and the third line 8.

[0013] A sectionalizing switch (PAS) 20 is provided between the high-voltage distribution line 3 and each of the low-voltage distribution lines 12a, 14a, and 16a. The sectionalizing switch 20 opens the circuits between the high-voltage distribution line 3 and each of the low-voltage distribution lines 12a, 14a, and 16a when an electrical fault occurs within the customer 25. A power receiving panel 22 is provided between the sectionalizing switch 20 and the customer 25. Typically, the power receiving panel 22 is located on the premises of the customer 25. The power receiving panel 22 is equipped with a fused switch (LBS) 23 and a transformer (pole transformer) Tr. The fused switch 23 automatically opens when an electrical fault occurs in the load 24 used by the customer 25, preventing cascading faults. The transformer Tr converts the high-voltage distribution line 3 to low voltage and supplies it to the low-voltage distribution lines 12a, 14a, and 16a.

[0014] In the microgrid system 100, consumers 25 normally use electricity supplied from the power plant 2. While power is being supplied from the power plant 2, the battery storage device 40 is charged. In the event of a disaster, electrical accident, etc., the automatic switches 5 and 7 are opened, and the power supply from the power plant 2 to the microgrid 10 is stopped. When the automatic switches 5 and 7 are opened, power is supplied to each consumer 25 from the battery storage device 40. Subsequently, when the power supply from the power plant 2 is restored, the automatic switches 5 and 7 are closed, and the power supply from the battery storage device 40 is stopped.

[0015] While power is being supplied from the battery storage device 40 to the high-voltage distribution line 3, the reactive power compensation device 30 monitors the voltage of the high-voltage distribution line 3. When the voltage of the high-voltage distribution line 3 falls outside a predetermined range, the reactive power compensation device 30 supplies reactive power to the high-voltage distribution line 3 to restore the voltage of the high-voltage distribution line 3 to within the predetermined range. The reactive power compensation device 30 can immediately restore the voltage of the high-voltage distribution line 3 to within the predetermined range when the voltage falls outside the predetermined range.

[0016] The capacity of the battery storage device 40 is selected according to the power used by each customer 25. Therefore, while power is being supplied from the battery storage device 40, the voltage of the high-voltage distribution line 3 is normally maintained within a predetermined range. However, if a load 24 such as a motor is directly connected to the high-voltage distribution line 3, several times the rated current flows through the high-voltage distribution line 3 when the load 24 starts up. Therefore, when the load 24 starts up, the voltage of the high-voltage distribution line 3 may drop below a predetermined range. In such cases, reactive power is supplied to the high-voltage distribution line 3 from the reactive power compensation device 30, and the voltage of the high-voltage distribution line 3 is restored to within a predetermined range.

[0017] As described above, replacing the battery storage device 40 with a high-capacity battery storage device 40 capable of handling the startup of the load 24 (excessive power compared to normal use) would increase the construction cost of the microgrid system 100. Therefore, by using the battery storage device 40 and the reactive power compensation device 30 in combination, the construction cost of the microgrid system 100 can be reduced.

[0018] (Second example) Referring to Figure 2, the microgrid system 100a will be described. The microgrid system 100a is a modified version of the microgrid system 100, and the structure within the microgrid 10a differs from that of the microgrid 10 of the microgrid system 100. In the following description, features of the microgrid system 100a that are common to the microgrid system 100 may be omitted from the description by assigning the same reference number as the microgrid system 100.

[0019] The high-voltage distribution line 3 is equipped with a battery device 40, a high-voltage shunt capacitor 42, and a reactive power compensation device 30a. The reactive power compensation device 30a is smaller in size and has a smaller capacity than the reactive power compensation device 30. That is, the reactive power compensation device 30a is lower in cost than the reactive power compensation device 30. In the microgrid system 100a, when the voltage of the high-voltage distribution line 3 goes out of the predetermined range, the high-voltage shunt capacitor 42 and the reactive power compensation device 30a supply reactive power to the high-voltage distribution line 3. The high-voltage shunt capacitor 42 supplies the reactive power corresponding to the difference in capacity between the reactive power compensation device 30 and the reactive power compensation device 30a to the high-voltage distribution line 3. For example, when the capacity difference between the reactive power compensation device 30 and the reactive power compensation device 30a is 100 kvar, a high-voltage shunt capacitor 42 with a capacity of 100 kvar is used. By using the high-voltage shunt capacitor 42, the construction cost of the microgrid system 100a can be further reduced.

[0020] (Other modifications) In the above embodiment, an example of using a battery device as the active power supply device has been described. However, instead of the battery device, or in addition to the battery device, a power generation device (generator) using fossil fuel may be used. Also, a natural energy power generation device (such as a solar power generation device, a wind power generation device, etc.) may be connected to the high-voltage distribution line in the microgrid.

[0021] In the above second embodiment, the high-voltage shunt capacitor may be removed and the reactive power compensation device may be controlled at a constant power factor. In this case, the reactive power compensation device may supply lagging reactive power to the high-voltage distribution line by the capacity of the high-voltage shunt capacitor with respect to the power factor calculation result.

[0022] The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. Also, the technical elements described in this specification or the drawings exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Further, the technology illustrated in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of those objectives itself has technical utility.

Description of Reference Numerals

[0023] 3: High-voltage power distribution line 30: Reactive power compensation device<00,00101>40: Active power supply device 100: Microgrid system

Claims

1. A microgrid system formed within a power distribution system, An active power supply device that is connected to the high-voltage distribution system and supplies active power, A reactive power compensation device that is connected to the high-voltage distribution system and supplies reactive power, Equipped with, When the power supply from the power plant is interrupted in the high-voltage distribution system, an automatic switch installed in the high-voltage distribution system switches over, and power is supplied to the high-voltage distribution system from the active power supply device. While power is being supplied from the active power supply device to the high-voltage distribution system, the reactive power compensation device monitors the voltage within the high-voltage distribution system. When the voltage in the high-voltage distribution system falls outside a predetermined range, the reactive power compensation device is a microgrid system that supplies lagging reactive power to the high-voltage distribution system to restore the voltage within the high-voltage distribution system to within a predetermined range.

2. A microgrid system formed within a power distribution system, An active power supply device that is connected to the high-voltage distribution system and supplies active power, A reactive power compensation device that is connected to the high-voltage distribution system and supplies reactive power, A high-voltage power factor correction capacitor connected to a high-voltage power distribution system, Equipped with, When the power supply from the power plant is interrupted in the high-voltage distribution system, an automatic switch installed in the high-voltage distribution system switches over, and power is supplied to the high-voltage distribution system from the active power supply device. While power is being supplied from the active power supply device to the high-voltage distribution system, the reactive power compensation device monitors the voltage within the high-voltage distribution system. A microgrid system that, when the voltage in a high-voltage distribution system falls outside a predetermined range, uses a high-voltage power factor correction capacitor to supply reactive power to the high-voltage distribution system, and a reactive power compensation device to supply lagging reactive power to the high-voltage distribution system to restore the voltage in the high-voltage distribution system to within a predetermined range.

3. A microgrid system formed within a power distribution system, An active power supply device that is connected to the high-voltage distribution system and supplies active power, A reactive power compensation device that is connected to the high-voltage distribution system and supplies reactive power, A high-voltage power factor correction capacitor connected to a high-voltage power distribution system, Equipped with, When the power supply from the power plant is interrupted in the high-voltage distribution system, an automatic switch installed in the high-voltage distribution system switches over, and power is supplied to the high-voltage distribution system from the active power supply device. While power is being supplied from the active power supply device to the high-voltage distribution system, the reactive power compensation device monitors the power factor within the high-voltage distribution system. A microgrid system that, when the power factor in a high-voltage distribution system falls outside a predetermined range, uses a high-voltage power factor correction capacitor and a reactive power compensation device to supply lagging reactive power to the high-voltage distribution system to restore the power factor within the high-voltage distribution system to within a predetermined range.

4. A microgrid system according to any one of claims 1 to 3, wherein the active power supply device is a battery storage device.

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