KR20170038410A

KR20170038410A - Energy Storage System Equipped with Frequency Adjusting and Peak Load Reducting Function, Its Reclosing Method

Info

Publication number: KR20170038410A
Application number: KR1020150137739A
Authority: KR
Inventors: 서훈철
Original assignee: 연암공과대학교산학협력단
Priority date: 2015-09-30
Filing date: 2015-09-30
Publication date: 2017-04-07
Also published as: KR101827390B1

Abstract

The present invention relates to a reclosing method of an energy storage system (ESS) having a frequency adjustment or maximum load reduction function. The method transmits an opening and closing operation command to a recloser and a system interconnection circuit breaker of the ESS through an inner operation performed in a control center when receiving an electric current of a system. Therefore, a power distribution system can be protected while ensuring power quality when connecting with the ESS having a frequency adjustment or maximum load reduction function.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy storage system and an energy recovery system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reclosing an energy storage system (ESS) having a frequency adjustment function or a maximum load reduction function, and more particularly, To the reclosing technique for performing the reclosing.

ESS is expected to grow very rapidly around the world, and many domestic companies are actively participating in the ESS market. In addition, several research institutes are actively conducting research on ESS system linkage. As mentioned above, various institutes are developing the impact analysis technology for grid linkage of ESS, but most of them are limited to the power quality and ESS operation field, and development of protection related technology is rarely performed. Therefore, the present invention overcomes the situation where the conventional technology development is limited only by the hardware aspect, and suggests a method to overcome the effect of the reclosing problem among the protection related issues in the ESS-related distribution system.

Similar prior art techniques for disclosing a reclosing method of an ESS with a frequency tuning or full load reduction function according to the present invention include KR 10-1129634 (B1); KR 10-1419845 (B1); KR 10-1467249 (B1); KR 10-2008-0069021 (A); KR 10-2011-0015090 (A); KR 10-2011-0097514 (A); KR 10-2011-0054229 (A); .

The above-described prior art fails to provide a reclosing method capable of protecting the power distribution system while securing the power quality in the grid connection of the ESS.

KR 10-1129634 (B1)

KR 10-1419845 (B1)

KR 10-1467249 (B1)

KR 10-2008-0069021 (A)

KR 10-2011-0015090 (A)

KR 10-2011-0097514 (A)

KR 10-2011-0054229 (A)

The present invention aims to satisfy the technical needs required from the background of the above-mentioned invention. Specifically, it is an object of the present invention to provide a method for protecting a power distribution system while ensuring power quality in a grid connection of an ESS having a frequency adjustment or a maximum load reduction function.

The technical objects to be achieved by the present invention are not limited to the above-mentioned problems, and other technical subjects not mentioned can be clearly understood by those skilled in the art from the following description. There will be.

In order to accomplish the above object, there is provided a method of reclosing an ESS including a frequency adjustment or a maximum load reduction function, comprising the steps of: (S10) receiving current and time in a system; If the current value is greater than or equal to a predetermined value after step S10, determining that an in-system fault current flows; If it is confirmed that the in-system fault current flows in step S20, a step S30 of simultaneously transmitting an open operation command to the recloser circuit breaker and the ESS; In step S40, it is determined whether the flow of the in-system fault current is removed to determine whether the open operation command performed in step S30 has been properly performed. If it is determined in step S40 that there is no flow of the fault current in the system, performing a closing operation of the reclosing breaker (S50; S60) within 0.5 seconds after the fault is cut off, which is the current reclosing time; Confirming whether or not a fault current flows due to the presence of a fault in the system even after the step S60 (S70); If the flow of the fault current in the system is reaffirmed in step S70, the step of performing the opening operation of the recloser circuit breaker again (S80); Performing the closing operation of the reclosing circuit breaker after 15 seconds (S90; S100) if the re-closing circuit breaker opening operation is performed again in the step S80; Confirming whether the in-system fault current remains after step S100 (S110); If it is determined in step S110 that the flow of the fault current in the system is confirmed, it is determined that the fault is a permanent fault and the closure operation of the reclosing breaker is performed (S120); If it is determined in step S70 and step S110 that the in-line fault current has been removed, the operation flow is terminated after moving to the closing operation step (S130) of the ESS.

As described above, the present invention overcomes the situation where the conventional technology development is limited only by the approach of the hardware aspect and not only secures the power quality of the power distribution system to which the ESS is connected, but also protects the distribution system related to the ESS It has the effect of providing a way to solve the impact on the reclosing problem among issues.

It is to be understood that the technical advantages of the present invention are not limited to the technical effects mentioned above and that other technical effects not mentioned can be clearly understood by those skilled in the art from the description of the claims There will be.

1 shows a reclosing mode of operation in a power distribution system;
Fig. 2 is a diagram showing an example of the configuration of a power distribution system to which an ESS is connected; Fig.
3 is a diagram illustrating an example of a reclosing configuration when the ESS according to the present invention is used for frequency adjustment or maximum load reduction;
4 is a flow chart of the reclosing method when the ESS according to the present invention is used for frequency adjustment or maximum load reduction;
5 is a simulation model of the reclosing method when the ESS according to the present invention is used for frequency adjustment or maximum load reduction;
FIG. 6 is a reference diagram of SOC waveform results among simulation results under steady state using the simulation model set in FIG. 5; FIG.
FIG. 7 is a reference diagram of a current waveform result in a simulation result under a steady state using the simulation model set in FIG. 5; FIG.
FIG. 8 is a reference diagram of the grid current waveform result among the simulation results for the first simulation condition; FIG.
FIG. 9 is a reference diagram of the results of the reclosing and the ESS open / close switch signal among simulation results for the first simulation condition; FIG.
FIG. 10 is a reference diagram of SOC waveform results among the simulation results for the first simulation condition; FIG.
11 is a reference diagram of the grid current waveform result among the simulation results for the second simulation condition;
FIG. 12 is a reference diagram of the results of the reclosing and the ESS open / close switch signal among simulation results for the second simulation condition; FIG.
13 is a reference diagram of SOC waveform results among the simulation results for the second simulation condition;
Fig. 14 is a reference diagram of the results of the grid current waveform among simulation results for the third simulation condition; Fig.
FIG. 15 is a reference diagram of the results of the reclosing and the ESS open / close switch signal among simulation results for the third simulation condition; FIG.
FIG. 16 is a reference diagram of SOC waveform results among the simulation results for the third simulation condition; FIG.
17 is a reference diagram of the grid current waveform results among the simulation results for the fourth simulation condition;
FIG. 18 is a reference diagram for the reclosing and ESS switch signal results among the simulation results for the fourth simulation condition; FIG.
FIG. 19 is a reference diagram for SOC waveform results among the simulation results for the fourth simulation condition. FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, It is not. In the following description of the present embodiment, the same components are denoted by the same reference numerals and symbols, and further description thereof will be omitted.

In the power distribution system, a recloser is used to restore the circuit after a breakdown in case of a momentary failure. The recloser operates at 0.5 second after the fault current interruption. If the fault is still present, it operates secondarily after 15 seconds after shutdown. If there is a fault after that, it is judged to be a permanent fault and is permanently closed.

The reclosing operation in the power distribution system will be described in more detail with reference to FIG. The reclosing method currently used in the power distribution system has a non-voltage time (10; 20) of 0.5 seconds after the first interruption and 15 seconds after the second interruption as shown in FIG. Since the recloser circuit breaker judges whether or not to remove the fault based on the current when the non-voltage time elapses and the recloser is turned off, there is a disadvantage in that if the fault is removed during the non-voltage time, the remaining non-voltage time must be waited. The attempt to develop a technique for shortening the non-voltage time of a reclosing circuit breaker has been mainly carried out in the transmission system, and a method of determining the second arc sole time using the rms value of the fault voltage, a total harmonic distortion (THD ) To identify the secondary arc extinction time, and so on. In the power distribution system, development of a technology for determining whether a fault has been removed by using a carrier signal has been performed. In the distribution system, the duration of the secondary arc caused by the capacitance is very short. In addition, it is difficult to apply the conventional technology to the reality, and most of the faults actually occurring are instantaneous faults. Therefore, in the present invention, except for the instantaneous / permanent failure determination method, most of the failures are intended to provide a reclosing method that is assumed to be an instantaneous failure.

To use the ESS for frequency adjustment or for maximum load reduction, the system must be in a normal operating state, not a transient in which the fault has occurred. If the ESS continues to be connected in the event of a fault, the ESS can not be used for frequency adjustment or maximum load reduction. Therefore, the ESS should be isolated prior to fault occurrence and reclosing. As shown in FIG. 2, if the ESS is connected to the power distribution system, if the ESS is disconnected from the circuit at the time of failure, the reclosing operation may be performed in the same manner as in the conventional method. After that, the ESS can be fully restored by reconnecting it to the distribution system and the ESS can be used again for frequency tuning or full load reduction. In the case described above, additional problems not previously considered are to be considered, and the main considerations are as follows. First, consideration should be given to the success or failure of ESS before reclosing. Second, we consider the re-entry time of the ESS after failure elimination and reclosing success. Third, consider the problem of continuity of the blackout time when the failure duration is prolonged or in case of permanent failure.

When the ESS is used for frequency tuning or for maximum load reduction, a new reclosing method is proposed to reflect the above considerations. Referring to FIG. 3, the driving method to be proposed will be described in more detail. The control center 100 receives the current i (t) 200 of the system as an input and performs an internal calculation to obtain a recloser 300 And an open and close operation command 110 to the grid-connected circuit breaker of the ESS 400. [

FIG. 4 shows the flow of the detailed reclosing control method using the circuit system used for the frequency adjustment or the maximum load reduction shown in FIG.

First, the current I and the time T are inputted (S10). If the current value is equal to or greater than the predetermined value (a) (S20), it is determined as a failure, and an opening operation command is simultaneously issued to the reclosing breaker and the ESS (S30). In order to prevent the current from flowing into the ESS from the ESS, it is confirmed that I = 0 (S40) in order to judge whether the opening operation of the ESS has been performed properly. If it is properly performed, the current reclosing time, Closing operation of the reclosure circuit breaker (S60) is performed. After that, it is confirmed that the reclosing is successful and the fault current does not flow in the system, then the ESS is re-turned on again. If it is confirmed that a fault exists in the system and a fault current flows (S70), the operation of opening the recloser circuit breaker (S80) is performed again and the closing operation of the reclosure circuit breaker (S100) is performed after 15 seconds . If there is a fault even after the second reclosing (S110), it is judged as a permanent failure and the recloser circuit breaker is locked out (S120). If the flow of the fault current is not detected in steps S70 and S110, the closing operation of the ESS is performed (S130), and then the operation flow is terminated.

In order to verify the flow of the reclosing method, a simulation model was set up as shown in FIG. 5 for a distribution system model in which the ESS was connected in a steady state. Line 1 (30) and Line 2 (40) are 10 km respectively, and the vessel type is ACSR 95 mm ² . The capacity of the ESS 400 is 1,000 kWh, assuming that a load of 1,000 kW is charged per second and the ESS is discharged for the maximum load reduction. FIG. 6 shows the SOC (state of charge) of the ESS, which is a simulation result under a normal state using the simulation model set in FIG. Referring to FIG. 6, it can be seen that the ESS starts discharging while the maximum load state is applied in one second. Also, referring to FIG. 7, it can be seen that the maximum value of the current increases as the instantaneous value waveform of the current flowing in the system reaches the maximum load state in one second.

In order to verify the reclosing method of the circuit system used for the frequency adjustment or the maximum load reduction shown in FIG. 4, the fault occurrence and the fault elimination conditions were classified into four cases and then the simulation was performed.

The first simulation condition is for the failure occurring at the time of charging. It is a condition that simulates the first recloser after the failure occurs at 0.7 second and the failure is removed at 0.8 seconds. The second simulation condition is for failure occurring during discharging. It is a condition to simulate the first recloser after the failure occurs at 1.2 seconds and the fault is removed at 1.3 seconds. The third simulation condition is for failure occurring during discharging. It is a condition that simulates a second recloser after a failure occurs in 1.2 seconds and the failure is removed in 4 seconds. The fourth simulation condition is for failure occurring during discharging. It is a condition simulating that failure occurs in 1.2 seconds and is maintained permanently.

The types of faults set in the above four simulation conditions are all 1-line ground fault, fault resistance is 1?, And fault occurrence position is 5 km of the line 2 (40). Originally, simulation was performed by setting the second reclosing time to 15 seconds, but for convenience of simulation, it was set to 4 seconds. This applies only to the third and fourth simulation conditions. In order to reconfirm the successful operation of the ESS 400 after the success of the second reclosing, a scenario is set up in which a 1,000 kW load is removed in two seconds and then put back in six seconds.

FIG. 8 shows the grid current waveform among the simulation results for the first simulation condition. It can be confirmed that the failure has occurred in 0.7 seconds and the reclosing has been successfully performed in 1.25 seconds after the failure has been removed in 0.75 seconds.

FIG. 9 shows the reclosing and ESS open / close switch signals of the simulation result for the first simulation condition. After the reclosing at 1.25 seconds, the ESS is re- do.

FIG. 10 shows SOC waveforms among simulation results for the first simulation condition. No charge / discharge operation occurs after a fault is removed in 0.75 second. It can be confirmed that the discharging operation of the ESS is being performed successfully since the re-closing is succeeded and the ESS is reloaded and thereafter it is at the maximum load state.

FIG. 11 shows the grid current waveform among the simulation results of the second simulation condition, which indicates that the reclosing was successfully performed at 1.75 seconds after 0.5 second after the failure occurred at 1.2 seconds and the failure was successfully removed at 1.25 seconds Can be confirmed.

FIG. 12 shows the reclosing and ESS opening / closing switch signals of the simulation result for the second simulation condition, which shows that the reclosing is performed at 1.75 seconds after 1.25 seconds and then the reclosing is successful, and the ESS It can be confirmed that it is reintroduced.

FIG. 13 shows the SOC waveform of the second simulation condition. In FIG. 13, a 1000 kW load is applied to the ESS in a second, and the ESS performs a discharging operation. After the failure occurs in 1.2 seconds, the ESS is separated from the system. / Discharge operation does not occur. After reclosing at 1.75 seconds and re-entering the ESS, the ESS will again perform the discharging operation because the 1000 kW load is still connected.

FIG. 14 shows the grid current waveform among the simulation results for the third simulation condition, in which the failure occurs in 1.2 seconds and the failure is removed in 1.25 seconds. We try to reclose at 1.75 seconds, which is 0.5 second later. The second reclosure is attempted at 5.75 seconds after 4 seconds. At this time, the fault is removed and the steady state waveform appears again. Also, it can be confirmed that the load of 1000 kW is recharged in 6 seconds, and the steady-state current slightly increases.

FIG. 15 shows the reclosing and ESS open / close switch signals among the simulation results for the third simulation condition. In FIG. 15, a failure occurs and both signals are removed at 1.25 seconds simultaneously. In 1.75 seconds, reclosing is attempted. However, there is a failure, so an open signal is generated again. At this time, there is no re-input signal of ESS. After confirming that the reclosure has been successfully performed after the second reclosure at 5.75 seconds, it can be confirmed that the re-input signal of the ESS is generated.

FIG. 16 shows SOC waveforms among the simulation results for the third simulation condition. A 1000 kW load is applied to the discharge in a second. There is no change in SOC since no charging / discharging operation is performed even when the voltage-free time and the first reclosing are attempted after the separation at 1.25 seconds. After the second reclosure is successful at 5.75 seconds and the ESS is recharged, the ESS performs the charging operation. And the discharge operation is performed because the 1000 kW load is re-applied in 6 seconds. Therefore, it can be confirmed that it is completely restored to the normal state.

FIG. 17 shows the grid current waveform among the simulation results for the fourth simulation condition. After the failure occurs at 1.2 seconds, the first recloser attempts at 1.75 seconds and the second recloser attempts at 5.75 seconds. However, since it is a permanent failure, it can be confirmed that the circuit is blocked again.

FIG. 18 shows the reclosing and ESS open / close switch signals among the simulation results for the fourth simulation condition. The failure occurs at 1.2 seconds and is simultaneously shut off at 1.25 seconds. 1.75 seconds and 5.75 seconds, but there is a failure and an open signal is generated again. Since it is in the state of permanent failure, it can be confirmed that the ESS input signal does not occur during the reclosing process.

FIG. 19 shows the SOC waveform among the simulation results for the fourth simulation condition, and the charge / discharge operation is normally performed 1.2 seconds before. No charge / discharge operation occurs after the fault occurs in 1.2 seconds and the fault is removed in 1.25 seconds. 1.75 seconds and 5.75 seconds, the discharge operation is attempted at the moment of the reclosing attempt. However, since the circuit is shut off again, it can be confirmed that no charge / discharge operation is performed.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, will be. Accordingly, the true scope of the present invention should be determined only by the appended claims.

100: Control center 200: Current in the system
300: recloser breaker 400: ESS

Claims

A method of reclosing an ESS having a frequency adjustment function or a maximum load reduction function,
Upon receipt of the current i (t) 200 of the system as input, the control center 100 performs an internal calculation to transmit the opening / closing operation command 110 to the grid interrupter of the recloser circuit breaker 300 and the ESS 400 Wherein the ESS is a reclosing device.

A method of reclosing an ESS having a frequency adjustment function or a maximum load reduction function,
A step (S10) of receiving a current (I) and a time (T) in the system;
Checking the current flow (S20);
A step S30 of opening the current flow at step S20;
A current flow reconfirming step (S40) for verifying the validity of the step S30;
Blocking the reclosing when the current reclosing time elapses after the step S40 (S50, S60);
A current flow reconfirming step (S70) for verifying the validity of the step S60;
After the step S70, re-opening the reclosure (S80);
(S90; S100) of re-closing the reclosing after 15 seconds after the step S80;
After the step S100, a step (S110) of checking the residual fault current in the system is performed;
If it is determined in step S110 that the fault current flows in the system, it is determined that the fault is a permanent fault and the closure operation of the recloser circuit breaker 300 is performed (S120);
If the flow of the fault current is not detected in steps S70 and S110, the flow is terminated by moving to the closing operation step (S130) of the ESS 400. [ .

3. The method of claim 2,
The method of claim 20, wherein if it is determined that the current flows after step S10, it is determined that the in-system fault current flows.

3. The method of claim 2,
The operation of step S30 is such that if it is confirmed that the in-system fault current flows in step S20, the ESS 400 simultaneously transmits an open operation command to the recloser circuit breaker 300 and the ESS 400. [ Reclosing control method.

3. The method of claim 2,
Wherein the operation of step S40 is to confirm whether the flow of the fault current in the system has been removed to determine whether the open operation command performed in step S30 has been properly performed.

3. The method of claim 2,
If it is determined in step S40 that there is no flow of the in-system fault current in step S50, the shutdown operation of the reclosure circuit breaker 300 is performed in 0.5 seconds after the breakdown, which is the current reclosing time To the ESS.

3. The method of claim 2,
Wherein the execution of step S70 is to reaffirm whether or not a fault current flows due to the continued existence of the fault in the system even after the step S60.

3. The method of claim 2,
In the step S80, if the flow of the in-system fault current is re-confirmed in step S70, the reclosing operation of the reclosing breaker 300 is performed again.

3. The method of claim 2,
The operation of steps S90 and S100 may be performed by repeating the operation of opening the reclosing breaker 300 again in step S80 so as to perform the closing operation of the reclosing circuit breaker 300 after 15 seconds Method of reclosing control of ESS.

3. The method of claim 2,
The operation of step S130 is performed when it is confirmed that the reclosing is successfully performed in steps S60 and S100 and the flow of the fault current is completely shut off. .

3. The method of claim 2,
Verification data of the implementation flow of the ESS reclosing control method with frequency adjustment or full load reduction function includes the grid current waveform data, the reclosing switch and the ESS link switch operation signal data, and the SOC waveform data Method of reclosing control of ESS.