JP2024024220A - Grid stabilization system and grid stabilization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grid stabilization system and a grid stabilization method that avoids grid frequency fluctuations and power outages by controlling the rate of change of power received at consumers in response to changes in a grid condition.

SOLUTION: The grid stabilization system is for stabilizing an on-premise power system 13 when the premise power system 13 that is disconnected from a commercial power grid 10 is in stand-alone operation and the entire grid is in low inertia. The grid stabilization system has low-inertia grid detection means (power receiving power detection unit 41) that detects that the entire grid to which the premise power system 13 is connected has become low inertia, a backup power source 21 with a PCS 23 that is connected to the premise power system 13 and controls charging and discharging of a power storage device 22, and a power receiving power monitoring and control device 40 that controls the output power from the backup power source 21 to the premise power system 13 to adjust the rate of change of the power receiving power to a predetermined value so that the fluctuation of the frequency of the premise power system 13 is within an acceptable range on the basis of at least the power receiving power detection value.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a grid stabilization system and a grid stabilization method for preventing grid frequency fluctuations and power outages from occurring when the load changes suddenly due to the inertia of the power grid. In particular, the present invention can be applied to power systems that inherently have low inertia, such as when an accident occurs in a power system resulting in islanding, or when a sudden change in load occurs in a power system that inherently has low inertia, such as a small-scale independent power system on a remote island or remote area. Related to technology for stabilizing the situation.

For example, Patent Document 1 discloses that when an accident occurs in the power transmission and distribution system and the on-premises power system of a factory that had been receiving power from the power transmission and distribution system becomes isolated, the supply and demand balance within the on-premises power system is A technique is disclosed that continues supplying power to a load while making adjustments.
In Patent Document 1, when an on-premises power system having multiple generators and loads is cut off from the power transmission system and becomes in an isolated state, the on-premises power system is stabilized based on the power flow state of the interconnection line between both systems. Calculate the amount of adjustment required (difference between total power generation and total load). If the deviation rate between the total power generation amount and the total load amount is greater than a predetermined value, the high-priority load is shut off depending on the magnitude relationship between the two (order or reverse of the power flow), or the above adjustment amount is adjusted. By taking measures such as apportioning power to each generator, we are striving to stabilize the on-site power system while adjusting the supply and demand balance.

Furthermore, in Patent Document 2, a power system monitoring unit in an external server constantly monitors the stability of the power system (inertia, reserve power, etc.), and when a commercial power supply is disconnected due to a system accident and the system stability decreases, , a technique has been disclosed for stabilizing the frequency of an islanding system by operating a PCS in a consumer that constitutes the islanding system and supplying power to a load from a distributed power source.

JP 2020-5336 ([0010] to [0026], Figures 1 to 3, etc.) JP2019-201453A ([0013] to [0105], Figures 1 to 4, etc.)

FIG. 4 shows a power transmission system 11 that has been disconnected from the commercial power system 10 due to the operation of the circuit breaker 12 due to an accident occurring between a commercial power system 10 consisting of a large-scale thermal power generator, etc., and a circuit breaker 12. It is a configuration diagram when the in-plant power system 13 of the factory 20 becomes an isolated system. It is assumed that the commercial power system 10 has a sufficiently large scale and a sufficiently large inertia.
This system configuration is basically the same as that assumed in Patent Documents 1 and 2 when a system accident occurs.

In FIG. 4, reference numeral 30 denotes a distributed power source connected to the power transmission system 11, such as a PCS (Power Conditioning System) 32, or a diesel generator (not shown) or the like. This distributed power source 30 may be installed as a facility within the factory 20.

A backup power supply 21 installed on the premises of the factory 20 is used to control the charging and discharging of the power storage device 22 such as a storage battery or a capacitor, and to transfer power between the on-premise power system 13 and the power storage device 22. The PCS 23 serves as a power converter.
Further, a load such as an AC motor is connected to the on-site power system 13.

If the circuit breaker 12 is not operating and is connected to the commercial power system 10, the inertia of the power transmission system 11 is sufficiently large, so as shown in _FIG . Even if the power received by the factory 20 suddenly decreases due to a sudden decrease in the received power, the frequency of the received power does not fluctuate much as shown by arrow a, and the frequency of the received power does not fluctuate much as shown by arrow a, resulting in a permissible level (permissible value of frequency size or permissible value of frequency fluctuation width). is within the range of

However, if, for example, an accident occurs between the commercial power system 10 and the circuit breaker 12 and the circuit breaker 12 operates and the on-premises power system 13 becomes an islanding system, the PCS 32 becomes a pseudo synchronous generator. When the control function is not provided or when the distributed power source 30 is a small-capacity diesel generator, the on-premise power system 13 is in a low inertia state.

FIG. 6 shows waveforms when received power suddenly decreases due to a sudden change in load amount in a low inertia state.
At this time, it is assumed that the output of the distributed power source 30 does not rise immediately after time _t1 , and that the output of the backup power source 21 remains unchanged (zero) before and after time _t1 .

In this case, the frequency of the on-premises power system 13 fluctuates as shown by arrow b in FIG. 6 and exceeds an allowable level, which may cause a relay (not shown) to operate and cause a power outage to the load 24.
That is, in the past, measures to stabilize the on-premise power system 13 were insufficient because no measures were taken in response to the decrease in system inertia.

Therefore, the problem to be solved by the present invention is to avoid fluctuations in the frequency of the power system and power outages when the load changes suddenly by adjusting the rate of change in the power received by consumers, and in particular to stabilize the low-inertia system. An object of the present invention is to provide a grid stabilization system and a grid stabilization method that can be maintained.

In order to solve the above-mentioned problems, the grid stabilization system of the present invention is a grid stabilization system for stabilizing the on-premises power system of a consumer connected to a commercial power system, which includes:
Received power detection means for detecting power received by the consumer from the commercial power system;
a backup power source that is connected to the on-premise power system and includes a power converter that controls charging and discharging of the power storage device;
Received power monitoring and control means for adjusting the rate of change in the received power of the customer to a predetermined value by controlling the power supplied from the backup power source to the on-premises power system based on at least a value detected by the received power detecting means. and,
It has the following.
More specifically, in order to keep the fluctuation in the frequency of the on-premises power system within an allowable range when the load within the consumer suddenly changes, the inertia of the entire system to which the on-premises power system is connected is determined. Based on this, the rate of change in the power received by the customer is adjusted to a predetermined value by controlling the power supplied to the on-premise power system from a backup power source that can control charging and discharging of the power storage device.

Further, the grid stabilization system of the present invention further includes a low inertia system detection means for detecting that the entire system to which the on-premises power system is connected has entered a low inertia state,
When the load amount suddenly changes while the low inertia system detection means detects that the entire system has become low inertia, the received power monitoring and control means adjusts the rate of change in the received power of the consumer to a predetermined value. It is something to be adjusted.

Furthermore, the system stabilization method of the present invention is a system stabilization method for stabilizing the on-premises power system of a consumer connected to a commercial power system, comprising:
Based on the detected value of the received power of the consumer and the magnitude of the inertia of the entire system to which the on-premises power system is connected, so that the fluctuation in the frequency of the on-premises power system falls within a permissible range when the load within the consumer suddenly changes. , the rate of change in the power received by the consumer is adjusted to a predetermined value by controlling the power supplied to the on-premises power system from a backup power source that can control charging and discharging of the power storage device.

Further, the system stabilization method of the present invention is a system stabilization method for stabilizing the on-premises power system of a consumer when the load suddenly changes while the entire system to which the on-premises power system of a consumer is connected has a low inertia. There it is,
When the load amount suddenly changes, the frequency of the on-premises power system can be adjusted by controlling charging and discharging power of the power storage device by a backup power source connected to the on-premises power system based on at least the detected value of received power of the customer. The change rate of the received power of the customer is controlled to a predetermined value so that the fluctuation of the power is within an allowable range.

According to the present invention, by adjusting the rate of change in power received by consumers when the load changes suddenly, fluctuations in the frequency of the power system and power outages can be avoided, and in the case of an islanding system, the islanding state can be stabilized. can be maintained.

1 is a configuration diagram of a grid stabilization system according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of the operation when the circuit breaker is operated in FIG. 1 (when a low inertia system is configured due to the islanding state). FIG. 2 is an explanatory diagram of the operation when the circuit breaker operates in FIG. 1 (when a low-inertia system is configured due to the islanding state), and in particular, is an explanatory diagram of the operation when the remaining power storage capacity of the power storage device is smaller than a predetermined value. . FIG. 2 is a configuration diagram when the on-premise power system becomes an islanding system. FIG. 5 is an explanatory diagram of the operation when the power transmission system is healthy in FIG. 4; FIG. 5 is an explanatory diagram of the operation when the circuit breaker operates in FIG. 4 (when a low inertia system is configured due to the islanding state).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of the grid stabilization system according to this embodiment, and the same parts as in FIG. 4 are given the same reference numerals and explanations are omitted. Explain.

Note that the power converter in the distributed power source 30 in FIG. An inverter that transfers power by performing forward/reverse conversion (bidirectional power conversion) between the two may also be used. That is, the types of these power converters are not limited to so-called PCS.

In FIG. 1, a received power detection unit 41 is installed at a power receiving point of a factory 20. The received power detection unit 41 detects the received power of the factory 20 based on the current and voltage input from the power transmission system 11 or the distributed power source 30, and sends the detection result to the received power monitoring and control device 40 via a wireless line or a wired connection. It has the ability to transmit via line. Note that the received power monitoring and control device 40 can also acquire the on/off state of the circuit breaker 12.

The received power monitoring and control device 40 includes an arithmetic processing device such as a CPU, a memory, and a communication interface that executes a predetermined program based on the received power detection value received from the received power detection unit 41 and the on/off state of the circuit breaker 12. etc. Although the received power monitoring and control device 40 may be installed in conjunction with the factory 20, the received power monitoring and control device 40 may be installed in a higher-level system monitoring and control device that monitors and controls the entire power system including other consumers. It may also have a function.

The received power monitoring and control device 40 uses the inertia of the entire system to which the on-premise power system 13 (PCS 23 in the backup power supply 21) is connected, the received power detection value, and the on/off state of the circuit breaker 12 to When the load amount suddenly decreases, the rate of change in the received power of the factory 20 is adjusted.
Specifically, the received power monitoring control device 40 generates a charge/discharge control signal according to the power that the backup power supply 21 should output to the on-premises power system 13, transmits this charge/discharge control signal to the PCS 23, and transmits the charge/discharge control signal to the power storage device 22. By charging and discharging the power, the rate of change in the power flow of the received power in the factory 20 is adjusted.
Note that the sudden decrease in the load amount can be detected based on the received power detection value and information from the load 24.

The adjustment operation of the rate of change in received power when the load suddenly changes as described above is as follows:
(a) An accident occurs in the power transmission system 11 (including the power transmission line between the commercial power system 10 and the circuit breaker 12), the circuit breaker 12 is turned off, the on-site power system 13 becomes isolated, and the on-site When the entire system to which the power system 13 is connected becomes a low inertia system,
(b) When the on-premises power system 13 is in an isolated operation state, the entire system to which the on-premises power system 13 is connected becomes a low-inertia system, and the remaining power storage capacity of the power storage device 22 in the backup power source 21 is small (rated capacity of the power storage device 22 is small or SOC is large),
(c) When the power transmission system 11 is healthy, the circuit breaker 12 is in the on state, and the inertia of the entire system to which the on-premise power system 13 is connected is sufficiently large,
is executed in either case.

In (a) and (b) above, the fact that the entire system has become a low-inertia system means that the received power monitoring and control device 40 detects the OFF state of the circuit breaker 12 and the received power detected value by the received power detector 41. Detection is possible by receiving the information. The received power monitoring and control device 40 gradually reduces (gently decreases) the received power change rate when the load amount suddenly decreases when the entire system has low inertia.
Furthermore, in the case of (c) above, the received power may be reduced at a larger rate of change than in the cases of (a) and (b) above.
It goes without saying that when adjusting the rate of change in received power, a rate of change that can be realized within the range of the SOC of power storage device 22 is taken into account.

Next, in FIG. 2, an accident occurs in the power transmission system 11, the circuit breaker 12 is turned off, and the on-premises power system 13 is disconnected from the commercial power system 10, which has a sufficiently large inertia, and the on-premises power system 13 is disconnected from the commercial power system 10, which has sufficiently large inertia. This figure shows the operation when the load amount suddenly decreases at time _t1 in the case of an inertial system.
The received power monitoring and control device 40 detects that the entire system to which the on-premise power system 13 is connected has become low inertia based on the received power detection value and the off information of the circuit breaker 12 received from the received power detection unit 41. If the amount of load suddenly decreases at time t ₁ in this state, the rate of change in received power is set so that the received power is gradually decreased after time t ₁ . Then, a charging/discharging control signal for the power storage device 22 is generated and transmitted to the PCS 23 so that the power received by the factory 20 is gradually reduced according to this set value, and the PCS 23 charges the power storage device 22, thereby increasing the power of the backup power source 21. The output is controlled to make the rate of change in received power match the set value.

In FIG. 2, the charging power to the power storage device 22 is increased at time _t1 , and thereafter, a charging/discharging control signal is given to the PCS 23 to gradually decrease the charging power until time _t2 , thereby gradually reducing the rate of change in received power. There is. Charging power P ₁ to power storage device 22 during this period (t ₁ to t ₂ ) is supplied by a current flowing from distributed power source 30 toward power storage device 22 via on-site power system 13 and PCS 23 .

As is clear from FIG. 2, after time _t1 , the sum of the received power and the output of the backup power supply 21 (the charging power _P1 to the power storage device 22) becomes equal to the load amount. In other words, the decrease in the received power during the period (t ₁ to t ₂ ) becomes the charging power P ₁ to the power storage device 22, and the power (load amount) supplied to the load 24 remains at a constant value after time t ₁ . It becomes.
Due to the operations of the received power monitoring control device 40 and the backup power supply 21 described above, the frequency of the received power no longer fluctuates as much as shown by the arrow c in FIG. I can do it.

Next, FIG. 3 shows the operation when the load amount suddenly decreases at time _t1 in a state where the entire system to which the on-premises power system 13 is connected has low inertia, as in FIG. 2. FIG. 4 is an explanatory diagram of operation when the remaining power storage capacity of the device 22 is small.
When the remaining power storage capacity of the power storage device 22 is smaller than a predetermined value (when the capacity of the power storage device 22 is originally small, or when the SOC of the power storage device 22 is large and the capacity that can be further charged is small), as shown in FIG. It is conceivable that charging power _P1 for gradually reducing the rate of change in received power cannot be secured.

Therefore, in such a case, as shown in FIG. 3, the received power is adjusted such that the charging power P ₂ to the power storage device 22 during the period (t ₁ to t ₃ ) is smaller than the charging power P ₁ in FIG. It is allowed to change the rate of change to a value larger than that in the case of FIG. In this case, the frequency of the received power fluctuates as shown by arrow d, but there is no particular problem in accepting this frequency fluctuation as long as it does not exceed the permissible level.
How much to increase the received power change rate when the remaining power storage capacity is smaller than a predetermined value may be determined based on the capacity, SOC, etc. of the power storage device 22.

Here, the rate of change in received power as shown in FIG. 3 is the same when the power transmission system 11 is healthy, the circuit breaker 12 is on, and the inertia of the entire system to which the on-premises power system 13 is connected is sufficiently large. Therefore, it is also applicable when the load amount suddenly decreases at time _t1 . In this case as well, even if the frequency of the received power fluctuates after time _t1 , there is no particular problem as long as it does not exceed the permissible level.

The rate of change in received power after time _t1 in FIGS. 2 and 3 is a value calculated in advance according to the magnitude of inertia of the entire system and the rate of change in load amount, taking into account the type and capacity of the distributed power source 30. Then, when the load amount actually changes suddenly at time _t1 , the received power change rate may be changed to the stored received power change rate.

In the above embodiment, the case where the consumer is the factory 20 has been described, but it goes without saying that the present invention is also applicable to cases where the consumer is an office building, a large-scale commercial facility, etc. .
Further, in the above embodiment, as an example of a low-inertia system being configured, a case where a power system disconnected from the commercial power system 10 enters an islanding state is exemplified, but for example, in a remote island or a remote area, Power systems to which power is supplied from diesel generators and the like that inherently have low inertia are also included in the above-mentioned low-inertia systems, and the present invention is effective when the load suddenly changes in these low-inertia systems.

10: Commercial power system 11: Power transmission system 12: Circuit breaker 13: On-premises power system 20: Factory 21: Backup power supply 22: Power storage device 23: PCS
24: Load 30: Distributed power source 31: Solar cell 32: PCS
40: Received power monitoring control device 41: Received power detection unit

Claims (11)

A system stabilization system for stabilizing the on-premise power system of a consumer connected to a commercial power system, the system comprising:
Received power detection means for detecting power received by the consumer from the commercial power system;
a backup power source that is connected to the on-premise power system and includes a power converter that controls charging and discharging of the power storage device;
Received power monitoring and control means for adjusting the rate of change in the received power of the customer to a predetermined value by controlling the power supplied from the backup power source to the on-premises power system based on at least a value detected by the received power detecting means. and,
A grid stabilization system characterized by having. In the grid stabilization system according to claim 1,
A grid stabilization system characterized in that a distributed power source is connected to a power receiving point of the consumer. A system stabilization method for stabilizing a premises power system of a consumer connected to a commercial power system, the method comprising:
Based on the detected value of the received power of the consumer and the magnitude of the inertia of the entire system to which the on-premises power system is connected, so that the fluctuation in the frequency of the on-premises power system falls within a permissible range when the load within the consumer suddenly changes. , a system stabilization system characterized in that the rate of change in the power received by the consumer is adjusted to a predetermined value by controlling the power supplied to the on-premise power system from a backup power source that can control charging and discharging of a power storage device. Method. In the grid stabilization system according to claim 1 or 2,
further comprising low inertia system detection means for detecting that the entire system to which the on-premise power system is connected has entered a low inertia state,
When the load amount suddenly changes while the low inertia system detection means detects that the entire system has become low inertia, the received power monitoring and control means adjusts the rate of change in the received power of the consumer to a predetermined value. A grid stabilization system that features adjustment. In the grid stabilization system according to claim 4,
A system stabilizing system, wherein the received power detection means functions as the low inertia system detection means. In the grid stabilization system according to claim 4,
System stabilization comprising means for detecting on/off information of a circuit breaker installed between the commercial power system and the consumer, the means functioning as the low inertia system detection means. system. In the grid stabilization system according to claim 2,
A grid stabilization system characterized in that when the load amount suddenly changes, charging power to the power storage device is supplied from the distributed power source via the on-premises power system. In the grid stabilization system according to claim 1 or 2,
The grid stabilization system is characterized in that the received power monitoring control means changes the rate of change of the received power in accordance with the remaining power storage capacity of the power storage device. A system stabilization method for stabilizing the on-premises power system of a consumer when the load suddenly changes in a state where the entire system to which the on-premises power system of a consumer is connected has a low inertia, the method comprising:
When the load amount suddenly changes, the frequency of the on-premises power system can be adjusted by controlling charging and discharging power of the power storage device by a backup power source connected to the on-premises power system based on at least the detected value of received power of the customer. 1. A system stabilization method, comprising: controlling a rate of change in power received by the consumer to a predetermined value so that fluctuations in power fall within an allowable range. In the system stabilization method according to claim 9,
A system stabilization method, characterized in that when the load amount suddenly changes, charging power to the power storage device is supplied from a distributed power source connected to a power receiving point of the consumer via the on-premises power system. In the system stabilization method according to claim 9 or 10,
A system stabilization method characterized in that the rate of change of the received power is changed according to the remaining power storage capacity of the power storage device.

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