JP2023150834A - Micro-grid system - Google Patents

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

This specification discloses technology related to a microgrid system.

Patent Document 1 discloses a microgrid system including a power generation device and a storage battery device. The microgrid system of Patent Document 1 includes a heat engine power generation device and a natural energy power generation device as power generation devices. In Patent Document 1, the operation timings of a heat engine power generator and a natural energy power generator are controlled, the heat engine power generator generates electricity at a constant rate, and the fuel efficiency of the heat engine power generator is improved.

Japanese Patent Application Publication No. 2015-015793

In a microgrid system equipped with a power generation device and a storage battery device as in Patent Document 1, in order to reliably supply power to consumers, it is necessary to design the power generation device, storage battery device, etc. to have a larger capacity than normally required. It is. In particular, when starting a power load such as a motor, a current several times the rated amount of electricity may flow through the power distribution system. In preparation for such a case, it is necessary to design the power generation device, storage battery device, etc. with a margin of capacity, and it is necessary to select a device with a larger capacity than normally required. As a result, it becomes necessary to select large-sized equipment, which increases the cost of securing equipment installation space, equipment cost, and investment cost for constructing a microgrid system. This specification provides a technique for realizing a microgrid system with reduced investment costs.

The microgrid system disclosed herein is formed within a power distribution system. This microgrid system includes an active power supply device that is connected to a high-voltage power distribution system and supplies active power, and a reactive power compensator that is connected to the high-voltage power distribution system and supplies reactive power.

1 shows a microgrid system according to a first embodiment. A microgrid system according to a second embodiment is shown.

The microgrid system disclosed herein is formed within a power distribution system that is supplied with power from a power plant. Microgrid systems can be connected to and separated from power distribution lines from power plants by switches. Therefore, while the microgrid system is connected to the distribution line from the power plant, consumers within the microgrid can utilize the power from the power plant. When the microgrid system is separated from the distribution line from the power plant, consumers within the microgrid can utilize the power generated within the microgrid.

The microgrid system includes an active power supply device and a reactive power compensator. The active power supply device is connected to the high voltage distribution system within the microgrid. That is, the active power supply device is provided downstream from a switch that connects to and separates from the power distribution line from the power plant. Examples of active power supply devices include power generation devices and storage battery devices. The reactive power compensator is also connected to the high voltage power distribution system within the microgrid. Examples of reactive power compensators include SVC, SVG, TSC, and TCR.

The reactive power compensator can supply reactive power to the high-voltage power distribution system to restore the voltage of the high-voltage power distribution system to within a predetermined range when the voltage of the high-voltage power distribution system is outside a predetermined range. For example, when starting a power load such as a motor, a large current temporarily flows through the high-voltage power distribution system, and the voltage of the high-voltage power distribution system may drop outside a predetermined range. In such a case, by supplying reactive power from the reactive power compensator to the high voltage power distribution system, the voltage of the high voltage power distribution system can be maintained within a predetermined range. Further, the microgrid system may include a high voltage phase advance capacitor connected to a high voltage power distribution system within the microgrid. The high voltage phase advance capacitor can also supply voltage to the high voltage power distribution system and maintain the voltage of the high voltage power distribution system within a predetermined range. By using a high-voltage phase advancing capacitor, a reactive power compensator with even smaller capacity (smaller size) can be used.

As described above, by arranging the reactive power compensator within the microgrid, the voltage of the high-voltage power distribution system can be maintained within a predetermined range. Typically, when starting a power load such as a motor, a larger current (several times higher than normal) flows through the high-voltage power distribution system than during normal operation. Therefore, when starting a power load, the voltage of the high-voltage power distribution system tends to drop. Conventionally, when designing a microgrid, a large-capacity active power supply device (such as a power generation device) is employed in order to stably supply power at the time of starting a power load. However, a large-capacity active power supply device can be said to have excessive performance during normal operation. By using the active power supply device and the reactive power compensator together, the microgrid system described above can select an active power supply device suitable for the normal operation of the power load. Therefore, the microgrid system can use a small-capacity (small) active power supply device. As a result, installation space costs and equipment costs for constructing a microgrid system can be reduced.

(First example)
The microgrid system 100 will be described with reference to FIG. 1. The microgrid system 100 includes a storage battery device 40 connected to a high-voltage distribution line 3 to which power is supplied from a power plant 2, and a reactive power compensator 30. The storage battery device 40 is an example of an active power supply device. The high voltage distribution line 3 is provided with automatic switches 5 and 7 that turn on and off the supply of electric power. The storage battery device 40 and the reactive power compensator 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. Even if the automatic switches 5 and 7 are opened (power supply is turned off), the consumers in the microgrid 10 can use electric equipment by supplying power from the storage battery device 40. In 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.

The high-voltage distribution line 3 has three high-voltage wirings (three-phase wiring) 4, 6, and 8. The low voltage distribution lines 12a, 14a, and 16a are connected to two phases of the first wiring (first phase) 4, the second wiring (second phase) 6, and the third wiring (third phase) 8. The low-voltage distribution lines 12a, 14a, and 16a can be classified into three groups depending on the high-voltage wiring to which they are connected. Specifically, the low voltage wiring of the first group 16 (the first low voltage distribution line 16a) is connected to the first wiring 4 and the second wiring 6. The low voltage wiring of the second group 14 (second low voltage distribution line 14a) is connected to the second wiring 6 and the third wiring 8. The low voltage wiring of the third group 12 (third low voltage distribution line 12a) is connected to the first wiring 4 and the third wiring 8.

A section 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 sectional switch 20 opens the electrical circuit between the high voltage distribution line 3 and each of the low voltage distribution lines 12a, 14a, and 16a when an electrical accident occurs within the consumer 25. A power receiving panel 22 is provided between the sectional switch 20 and the consumer 25. Typically, the power receiving board 22 is placed within the premises of the consumer 25. The power receiving board 22 includes a fuse-equipped switch (LBS) 23 and a transformer (pole transformer) Tr. The fuse-equipped switch 23 automatically opens when an electrical accident occurs in the load 24 used by the consumer 25 to prevent a spillover accident. The transformer Tr converts the high voltage distribution line 3 into low voltage and supplies it to the low voltage distribution lines 12a, 14a, and 16a.

In the microgrid system 100, the consumer 25 usually uses the power supplied from the power plant 2. While power is being supplied from the power plant 2, the storage battery device 40 is charged with power. When a disaster, electrical accident, etc. occurs, 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 supply from the storage battery device 40 to each customer 25 is started. Thereafter, when the power supply from the power plant 2 is resumed, the automatic switches 5 and 7 are turned on, and the power supply from the storage battery device 40 is stopped.

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

The capacity of the storage battery device 40 is selected according to the power normally used by each consumer 25. Therefore, while power is being supplied from the storage battery device 40, the voltage of the high-voltage power distribution line 3 is normally maintained within a predetermined range. However, when a load 24 such as a motor is directly connected to the high voltage distribution line 3, a current several times the rated current flows through the high voltage distribution line 3 when the load 24 is started. Therefore, when the load 24 is started, the voltage of the high-voltage power distribution line 3 may fall below a predetermined range. In such a case, reactive power is supplied from the reactive power compensator 30 to the high voltage distribution line 3, and the voltage of the high voltage distribution line 3 is restored to within a predetermined range.

As described above, if the storage battery device 40 is replaced with a storage battery device 40 with a large capacity (excessive power than normally used) that can handle the start-up of the load 24, the construction cost of the microgrid system 100 will increase. Therefore, by using the storage battery device 40 and the reactive power compensator 30 together, the construction cost of the microgrid system 100 can be reduced.

(Second example)
The microgrid system 100a will be described with reference to FIG. 2. The microgrid system 100a is a modification of the microgrid system 100, and the structure within the microgrid 10a is different from 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 designated by the same reference numbers as the microgrid system 100, and the description thereof may be omitted.

The high voltage distribution line 3 is equipped with a storage battery device 40, a high voltage phase advance capacitor 42, and a reactive power compensator 30a. The reactive power compensator 30a is smaller than the reactive power compensator 30 and has a smaller capacity. That is, the reactive power compensator 30a is lower in cost than the reactive power compensator 30. In the microgrid system 100a, when the voltage of the high voltage distribution line 3 falls outside a predetermined range, the high voltage phase advance capacitor 42 and the reactive power compensator 30a supply reactive power to the high voltage distribution line 3. The high-voltage phase advance capacitor 42 supplies the high-voltage distribution line 3 with reactive power equal to the difference in capacity between the reactive power compensator 30 and the reactive power compensator 30a. For example, when the difference in capacity between the reactive power compensator 30 and the reactive power compensator 30a is 100 kvar, a capacitor with a capacity of 100 kvar is used as the high voltage phase advance capacitor 42. By using the high voltage phase advance capacitor 42, the construction cost of the microgrid system 100a can be further reduced.

(Other variations)
In the above embodiment, an example in which a storage battery device is used as an active power supply device has been described, but instead of or in addition to the storage battery device, a power generation device (generator) using fossil fuel may be used. Moreover, a natural energy power generation device (solar power generation device, wind power generation device, etc.) may be connected to the high voltage distribution line within the microgrid.

In the second embodiment, the high-voltage phase advance capacitor may be omitted and the reactive power compensator may be controlled with a constant power factor. In this case, the reactive power compensator may supply lagging reactive power to the high voltage distribution line by the capacity of the high voltage phase advancing capacitor based on the power factor calculation result.

Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above. Further, the technical elements described in this specification or the drawings exhibit technical usefulness singly or in various combinations, and are not limited to the combinations described in the claims as filed. Furthermore, the techniques illustrated in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of the objectives has technical utility in itself.

3: High voltage distribution line 30: Reactive power compensator 40: Active power supply device 100: Microgrid system

Claims (3)

A microgrid system formed within a power distribution system,
an active power supply device connected to a high voltage power distribution system and supplying active power;
a reactive power compensator connected to a high voltage distribution system and supplying reactive power;
A microgrid system with The microgrid system according to claim 1, further comprising a high voltage phase advance capacitor connected to the high voltage distribution system. The microgrid system according to claim 1 or 2, wherein the active power supply device is a storage battery device.

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