Generator circuit breaker control method based on short-circuit fault current symmetry

Abstract

The present invention discloses a generator circuit breaker control method based on short-circuit fault current symmetry, the method comprising: a control device collects the current on the generator outlet side in real time, when a short-circuit fault occurs, when the fault current rises to a peak value, the time of inputting the transfer current is calculated based on the current symmetry method, the time of inputting the transfer current is corrected by a correction coefficient, and then the circuit breaker opening time is calculated to achieve precise control of the generator circuit breaker. The present invention mainly aims at the situation that the existing control method cannot effectively cope with the complex short-circuit fault current on the generator outlet side, and fills the gap of effective methods for short-circuit control of generator circuit breakers.

Description

Technical Field

[0001] The invention belongs to the field of generator output circuit breakers and relates to a generator fast circuit breaker control method based on short-circuit current symmetry. Background Art

[0002] In recent years, with the continuous development of the power system, the voltage level has been continuously improved, and the single-unit capacity of the generator has been continuously increased, resulting in very serious short-circuit faults on the generator outlet side. It is urgent to use generator circuit breakers to interrupt the short-circuit current, minimize the impact of the short circuit, and protect the normal and stable operation of the generator and the power system.

[0003] At present, the generator outlet circuit breakers on the market generally adopt the traditional SF6 method, which has a long fault breaking time and a low breaking current level, which does not meet the development requirements of environmental protection of power equipment in the future. The current transfer generator outlet circuit breaker composed of power electronic components and mechanical circuit breakers can break short-circuit faults with higher current levels, and has a fast breaking speed, which can effectively solve the problems of traditional circuit breakers. However, the current transfer circuit breaker puts higher requirements on the control method. The existing control method relies too much on the short-circuit current calculation expression, and the short-circuit fault current calculation expression on the generator outlet side is too complicated, and the prediction of the opening time is not fast and accurate enough.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes a generator circuit breaker control method based on short-circuit fault current symmetry, which has strong versatility and is less affected by interference.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A generator circuit breaker control method based on short-circuit fault current symmetry comprises the following steps:

[0008] Step 1: The generator circuit breaker is provided with a main branch and a transfer branch. The correction coefficient α is set based on the short-circuit fault simulation at the generator outlet and the measured short-circuit current data. The early tripping time threshold ε is set according to the requirements of the generator outlet circuit breaker. The transfer current value I zy and waiting time for circuit breaker to open β;

[0009] Step 2: Real-time acquisition of the generator outlet current. A short circuit fault occurs at the generator outlet. 0 Moment, when I N-1 <I zy <I N, when the capture current is rising, the current value is equal to the transfer current value I zy The time is recorded as T 1 Moment, when I N，-2 <I N，-1 >I N， When the short-circuit current rises to its peak value, the moment is captured and recorded as T 2 At the moment, the current at the generator outlet is collected in a discrete manner, causing a short circuit fault T at the generator outlet. 0 Time, recorded as the 0th sampling point, then I N-1 Indicates the current value of the N-1th sampling point, I N Indicates the current value of the Nth sampling point, I N，-2 Indicates the current value of the N′-2th sampling point, I N，-1 Represents the current value of the N′-1th sampling point, I N， represents the current value of the N′th sampling point. By converting the discrete time coordinate to the continuous time coordinate, we can get T 1 ≈(N-1)Δt+δ, T 2 ≈(N′-1)Δt+δ, where Δt is the sampling interval;

[0010] Step 3: When the current peak is collected, the time T at which the transfer current is started is predicted. 4 And the main branch advance opening time T 3 , the correction coefficient α is used to adjust the time T of inputting transfer current 4 Make corrections, T 4 =α·(T 2 -T 1 )+T 2 The advance opening time T of the main branch is predicted by the advance opening time threshold ε 3 =T 4 -ε, calculate the generator circuit breaker opening waiting time T wait ,

[0011] T wait =T 3 -T 2 =α·(T 2 -T 1 )-ε, where α is the correction coefficient; ε is the early trip time threshold; T 1 is the moment when the short-circuit current rises to the transfer current value; T 2 is the peak moment of short-circuit current;

[0012] Step 4: Waiting time T for the generator circuit breaker to open after the short-circuit current peak moment wait Execute the circuit breaker opening command;

[0013] Step 5, when the current drops to the transfer current Izy When the transfer current is input through the transfer branch, the short-circuit current on the main branch is quickly reduced to 0, so that the main branch is quickly disconnected;

[0014] Step 6: Wait for a fixed time β after the transfer current is turned on. At time T 5 The circuit breaker disconnects the fault circuit.

[0015] In the method described, in step 1, the correction coefficient α is 0.85-1.

[0016] In the method described, in step 1, when the generator short-circuit fault current is an axisymmetric waveform, the correction coefficient α is 1.

[0017] In the method described, in step 1, the early opening time threshold ε is the shortest time threshold for the generator circuit breaker contacts to be successfully opened, and the early opening time threshold ε is a constant value.

[0018] In the method described, in step 2, the current peak value is the current peak value in the first half-wave.

[0019] In the method described, in step 2, δ is

[0020] In the method, the transfer branch includes a current transfer and damping module.

[0021] In the method described above, the correction coefficient α is 0.9.

[0022] In the method described above, the time T at which the transfer current is input 4 After the short-circuit current drops from the peak value, the short-circuit current value is equal to the transfer current value I zy The moment you are in.

[0023] In the method described, in step 5, the time when the transfer current is input through the transfer branch is determined according to the time when the control device collects the transfer current value.

[0024] Beneficial Effects

[0025] The present invention provides a method for calculating the time difference between the transfer current value moment and the current peak moment during the short-circuit current rising process. When the current rises to the maximum value, the circuit breaker opening waiting time is calculated by a formula. The calculation amount is small, and the short-circuit fault can be interrupted within one cycle. The problem of the traditional control method being complex in principle and the long algorithm calculation time can be effectively solved. The existing control method is too dependent on the mathematical expression of the short-circuit current and cannot adapt to the complex situation of the short-circuit current on the generator outlet side. The control method based on the symmetry of the short-circuit current of the present invention predicts the circuit breaker opening moment by the time difference between the transfer current moment and the current peak moment in the short-circuit current rising stage, and corrects it by a correction coefficient. The prediction deviation is small and can adapt to various short-circuit situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0027] In the attached picture:

[0028] Figure 1 A schematic diagram of the principle of a current transfer type generator circuit breaker according to an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of a short-circuit waveform time node according to an embodiment of the present invention;

[0030] Figure 3 A control flow chart of an embodiment of the present invention.

[0031] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0032] The following will refer to the attached Figures 1 to 3 Specific embodiments of the present invention are described in more detail. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0033] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0034] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0035] like Figure 1 As shown, the present invention is applied to a current transfer type generator circuit breaker. When the generator is in normal operation, the current flows through the main branch circuit breaker. The main branch circuit breaker and the circuit breaker S on the transfer branch are both fast circuit breakers driven by a fast repulsive mechanism, which can achieve fast opening after being triggered. Figure 2 As shown, at T 0 At this moment, a short circuit fault occurs in the generator system, and a rapidly increasing short-circuit current flows through the main branch circuit breaker. When the short-circuit current drops to the transfer current value I zy When the current transfer module inputs a transfer current i in the opposite direction of the main branch current zy , forcing the current on the main branch to quickly cross zero, thereby disconnecting the main branch. Due to the limitation of the circuit breaker's breaking capacity, the main branch circuit breaker needs to be opened in advance for a time ε, that is, at T 3 The main branch circuit breaker is successfully opened after the transfer current is input and the main branch circuit breaker contacts reach a certain opening distance. After that, the system current will flow through the damping module and further be greatly reduced by the current limiting effect of the damping module. After the current limiting, the circuit breaker S is opened quickly, and after waiting for a fixed time β, at T 5 At this moment, the circuit breaker S completely disconnects the short-circuit fault circuit.

[0036] In the current transfer type generator circuit breaker system, the current transfer value I zy , the advance tripping time ε and the waiting time β for the circuit breaker S to open are known fixed values ​​determined according to the short-circuit current characteristics of the system. Based on the above-mentioned breaking principle and characteristics, the present invention proposes a generator fast circuit breaker control method based on the symmetry of short-circuit current, which can accurately predict the time T when the main branch circuit breaker starts to open. 3 , and the short-circuit current drops to I zy After waiting for a fixed time β, at T 5 The circuit breaker S is disconnected at all times, and the purpose of completely disconnecting the fault circuit is finally achieved.

[0037] In one embodiment, the generator circuit breaker control method based on short-circuit current symmetry of the present invention comprises the following steps:

[0038] Step 1: Combine the short-circuit fault simulation and measured short-circuit current data at the generator outlet to reasonably set the correction coefficient α. Set the early trip time threshold ε according to the generator outlet circuit breaker requirements, and the transfer current value I zy And wait for the circuit breaker S to open for time β.

[0039] Step 2: Real-time acquisition of the generator outlet current. When the detection system determines a short circuit fault (T 0 After the moment, the control algorithm is started. N-1 <I zy <I N , when the capture current is rising, the current value is equal to the transfer current value I zy The time is recorded as T 1 . When I N’-2 <I N，-1 >I N’ When the short-circuit current rises to its peak value, the moment is captured and recorded as T 2 .

[0040] The actual control system collects the current at the generator outlet in a discrete manner, causing a short circuit fault T at the generator outlet. 0 time, recorded as the 0th sampling point. Then I N-1 Indicates the current value of the N-1th sampling point, I N Indicates the current value of the Nth sampling point. N，-2 Indicates the current value of the N′-2th sampling point, I N’-1 Indicates the current value of the N′-1th sampling point, which is the peak value of the sampling current. N， Represents the current value of the N′th sampling point. By converting the discrete time coordinate to the continuous time coordinate, we can get T 1 ≈(N-1)·Δt+δ, T 2 ≈(N′-1)·Δt+δ, where Δt is the sampling interval and δ is generally defaulted to

[0041] Step 3: When the control device collects the current peak value, it starts to predict the time T when the transfer current is put into use. 4 And the main branch advance opening time T 3 Taking into account the attenuation effect of the DC component in the short-circuit current at the generator outlet, the correction coefficient α set in advance is used to adjust T 4 Correction is made and T is calculated 4 =α(T 2 -T 1 )+T 2 And by advancing the opening time ε value, the time T of the circuit breaker opening action is predicted 3 =T 4 -ε. The generator fast circuit breaker opening waiting time T is calculated by the following formula wait .

[0042] T wait =T 3 -T 2 =α(T 2 -T 1)-ε;

[0043] In the formula, α is the correction coefficient;

[0044] ε is the advance opening time;

[0045] T 1 It is the moment when the short-circuit current rises to the transfer current value;

[0046] T 2 is the peak moment of short-circuit current;

[0047] Step 4: Wait T after the short-circuit current peak moment wait Execute the circuit breaker opening command.

[0048] Step 5, when the current drops to the transfer current I zy When the transfer current is input through the transfer branch, the short-circuit current on the main branch is rapidly reduced to 0, so that the main branch is quickly disconnected.

[0049] Step 6: Wait for a fixed time β after the transfer current is turned on. 5 At this moment, the circuit breaker S finally achieves the purpose of successfully breaking the fault circuit.

[0050] Example

[0051] The generator circuit breaker control method based on short-circuit current symmetry of this embodiment is applied within one cycle after a short-circuit fault occurs at the generator outlet side, and includes the following steps:

[0052] Step 1: Combine the short-circuit fault simulation and measured short-circuit current data at the generator outlet to reasonably set the correction coefficient α. Set the early trip time threshold ε according to the generator outlet circuit breaker requirements, and the transfer current value I zy And wait for the circuit breaker S to open for time β.

[0053] Step 2: Real-time acquisition of the generator outlet current. When the detection system determines a short circuit fault (T 0 After the moment, the control algorithm is started. N-1 <I zy <I N , when the capture current is rising, the current value is equal to the transfer current value I zy The time is recorded as T 1 . When I N’-2 <I N，-1 >I N’ When the short-circuit current rises to its peak value, the moment is captured and recorded as T 2 .

[0054] The actual control system collects the current at the generator outlet in a discrete manner, causing a short circuit fault T at the generator outlet. 0time, recorded as the 0th sampling point. Then I N-1 Indicates the current value of the N-1th sampling point, I N Indicates the current value of the Nth sampling point. N，-2 Indicates the current value of the N′-2th sampling point, I N，-1 Indicates the current value of the N′-1th sampling point, which is the peak value of the sampling current. N， Represents the current value of the N′th sampling point. By converting the discrete time coordinate to the continuous time coordinate, we can get T 1 ≈(N-1)·Δt+δ, T 2 ≈(N′-1)·Δt+δ, where Δt is the sampling interval and δ is generally defaulted to

[0055] Step 3: When the control device collects the current peak value, it starts to predict the time T when the transfer current is put into use. 4 And the main branch advance opening time T 3 Taking into account the attenuation effect of the DC component in the short-circuit current at the generator outlet, the correction coefficient α set in advance is used to adjust T 4 Correction is made and T is calculated 4 =α(T 2 -T 1 )+T 2 And by advancing the opening time ε value, the time T of the circuit breaker opening action is predicted 3 =T 4 -ε. The generator fast circuit breaker opening waiting time T is calculated by the following formula wait .

[0056] T wait =T 3 -T 2 =α(T 2 -T 1 )-ε;

[0057] In the formula, α is the correction coefficient;

[0058] ε is the advance opening time;

[0059] T 1 It is the moment when the short-circuit current rises to the transfer current value;

[0060] T 2 is the peak moment of short-circuit current;

[0061] Step 4: Wait T after the short-circuit current peak moment wait Execute the circuit breaker opening command.

[0062] Step 5, when the current drops to the transfer current I zyWhen the transfer current is input through the transfer branch, the short-circuit current on the main branch is rapidly reduced to 0, so that the main branch is quickly disconnected.

[0063] Step 6: Wait for a fixed time β after the transfer current is turned on. 5 At this moment, the circuit breaker S finally achieves the purpose of successfully breaking the fault circuit.

[0064] Figure 1 This is a schematic diagram of the principle of an injection current generator circuit breaker of an embodiment of the present invention, in which the arrows indicate the direction of current flow. When a short circuit occurs, the current on the main branch will increase rapidly. At the right time, the transfer branch current in the opposite direction to the main branch current can quickly reduce the current on the main branch to zero, which is beneficial to the disconnection of the main branch contacts. After the main branch is disconnected, the remaining current flows through the damping module and is subject to the current limiting effect, and finally the circuit is completely disconnected through the circuit breaker S.

[0065] It is particularly noted that the generator circuit breaker control method based on short-circuit current symmetry of the present invention is only applicable to Figure 1 The method of the present invention is not applicable to generator circuit breakers of the current injection type and generator circuit breakers of other principles.

[0066] Figure 2 The current waveform of this embodiment is shown in the figure, in which the current waveform at the generator outlet changes from a steady state to a transient current. Figure 2 The important time nodes captured in the control method are marked in T 0 The moment when the short circuit fault occurs, the control device receives the signal and starts the subsequent control method. As the short circuit current continues to increase, the control device successively captures the transfer current value at the moment T 1 And the short-circuit current peak time T 2 , and at T 2 Start predicting the main branch circuit breaker opening time T 3 And the time when the transfer current is put into operation T 4 , and finally realized in T 5 Completely disconnect the fault circuit at all times.

[0067] Figure 3 The present invention is a complete control flow chart of the present embodiment, including a generator circuit breaker control method based on short-circuit current symmetry, wherein the method for determining short-circuit fault is selected by the control device. The control method of the present invention is used after a short-circuit fault.

[0068] Combination Figure 2 and Figure 3As shown, the transfer current value should be set to a reasonable value. In principle, the control method of the present invention must start capturing the transfer current value after receiving a short-circuit fault. An unreasonable setting will cause the control method to fail, resulting in serious consequences. The correction coefficient α is set to 0.9 by default, and generally does not need to be modified to meet the situation of a short-circuit fault on the generator outlet side.

[0069] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A generator circuit breaker control method based on short-circuit fault current symmetry, It is characterized in that The method comprises the following steps: Step 1: The generator circuit breaker is provided with a main branch and a transfer branch, and the correction coefficient is set based on the short-circuit fault simulation at the generator outlet and the measured short-circuit current data. , set the early trip time threshold according to the generator output circuit breaker requirements , transfer current value And waiting time for circuit breaker to open ; Step 2: Real-time acquisition of the generator outlet current. A short circuit fault occurs at the generator outlet. Moment, when , the current value of the capture current rising stage is equal to the transfer current value The time is recorded as Moment, when When the short-circuit current rises to its peak value, the moment is captured and recorded as At this moment, the current at the generator outlet is collected in a discrete manner, causing a short circuit fault at the generator outlet. Time, recorded as the 0th sampling point, then Indicates The current value of the sampling point, Indicates The current value of the sampling point, Indicates The current value of the sampling point, Indicates The current value of the sampling point, Indicates The current value of the sampling point is converted from discrete time coordinates to continuous time coordinates to obtain , ,in is the sampling interval; Step 3: When the current peak is collected, the time to start the prediction of the transfer current is And the main branch advance opening time , through the correction factor The moment of inputting transfer current Make corrections, , and through the advance opening time threshold The value predicts the main branch circuit breaker opening time in advance , calculate the generator circuit breaker opening waiting time , ,in, is the correction factor; is the early trip time threshold; It is the moment when the short-circuit current rises to the transfer current value; is the peak moment of short-circuit current; Step 4: Waiting time for the generator circuit breaker to open after the short-circuit current peak moment Execute the circuit breaker opening command; Step 5, when the current drops to the transfer current When the transfer current is input through the transfer branch, the short-circuit current on the main branch is quickly reduced to 0, so that the main branch is quickly disconnected; Step 6: Wait for a fixed time after inputting transfer current , at the time The circuit breaker disconnects the fault circuit.

2. The method according to claim 1, It is characterized in that In step 1, the correction factor It is 0.85-1.

3. The method according to claim 1, It is characterized in that In step 1, when the generator short-circuit fault current is an axisymmetric waveform, the correction coefficient is 1.

4. The method according to claim 1, It is characterized in that In step 1, the early trip time threshold The shortest time threshold for successful opening of the generator circuit breaker contacts and the early opening time threshold is a constant value.

5. The method according to claim 1, It is characterized in that In step 2, the current peak value is the current peak value in the first half-wave.

6. The method according to claim 1, It is characterized in that In step 2, for .

7. The method according to claim 1, It is characterized in that The transfer branch includes a current transfer and damping module.

8. The method according to claim 1, It is characterized in that Correction factor is 0.

9.

9. The method according to claim 1, It is characterized in that The moment of inputting transfer current After the short-circuit current drops from the peak value, the short-circuit current value is equal to the transfer current value The moment you are in.

10. The method according to claim 1, It is characterized in that In step 5, the time when the transfer current is input through the transfer branch is determined according to the time when the control device collects the transfer current value.

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