Emergency power supply over-current protection method, system and device and storage medium

Abstract

The invention discloses an emergency power supply over-current protection method, system and device and a storage medium. The method comprises three-section over-current protection and zero-sequence over-current protection. The three-section over-current protection comprises the step of embedding a three-section protection method into analysis and judgment of over-current protection, magnetizing inrush current locking, low-voltage locking and direction locking. The zero-sequence over-current protection also comprises a three-section protection scheme adopted in the zero-sequence over-current protection. According to the invention, the power output of the emergency power supply load by the emergency power supply is actively reduced, and an alarm is given to carry out manual emergency processing, so that the probability of wrong turn-off of the power supply system is reduced, and reasonable protection of the special application of the emergency power supply is realized instead of a simple and direct power-off mode for protection.

Description

Technical Field

[0001] The present invention relates to an overcurrent protection method, system, device and storage medium, and particularly to an overcurrent protection method, system, device and storage medium for an emergency power supply, belonging to the technical field of power control. Background Art

[0002] Overcurrent protection (referred to as overcurrent protection for short) is a common safety protection mechanism in electrical appliances and / or electrical equipment, used to monitor and prevent dangerous situations caused by abnormal increase in current in the circuit. When the current in the circuit exceeds the rated value or the designed range, the overcurrent protection will be activated and corresponding measures will be taken to protect the safety of the circuit, equipment and personnel.

[0003] As an emergency power supply with a wide range of uses, the energy storage power vehicle can facilitate and provide guarantee for the power supply of important loads, power-off maintenance operations, temporary capacity increase of distribution transformers, emergency temporary power supply and other needs. Such emergency power supplies are conventionally configured with various safety protection measures such as overcurrent protection and overvoltage protection.

[0004] The traditional overcurrent protection method generally uses a circuit breaker for protection, that is, when the current exceeds the threshold, the circuit automatically cuts off the power. Although the safety is relatively high, it ignores the basic requirement of emergency power supply is to ensure the load power supply as much as possible. When there are current overlimit phenomena caused by non-fault reasons, such as magnetizing inrush current and negative power overcurrent, the system is prone to misoperation of protection, resulting in unnecessary power-off protection, affecting the normal operation of the load, and the emergency power supply guarantee rate for abnormal phenomena is not high. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide an overcurrent protection method, system, device and storage medium for an emergency power supply that can improve the power supply guarantee performance and continuous power supply ability.

[0006] Technical Solution: An overcurrent protection method for an emergency power supply according to the present invention includes: three-stage overcurrent protection and zero-sequence overcurrent protection;

[0007] The three-stage overcurrent protection includes:

[0008] The action logic of the first-stage protection is: when the current exceeds the overcurrent setting value of the first-stage overcurrent, and the magnetizing inrush current blocking judgment is correct, and the direction blocking judgment is correct, and the voltage is normal, trigger the first-stage overcurrent protection action;

[0009] The action logic of the second-stage protection is: when the current exceeds the overcurrent setting value of the second-stage overcurrent, and the direction blocking judgment is correct, and the voltage is not lower than the preset rated value, the low-voltage blocking is opened, and the second-stage overcurrent protection action is triggered after a preset delay;

[0010] The action logic of the three-stage protection is as follows: when the current exceeds the over-current setting value of the third stage of over-current, the direction blocking judgment is correct, and the voltage is not lower than the preset rated value, the low-voltage blocking is opened, and the three-stage over-current protection action is triggered after a preset delay.

[0011] Further, for the three-stage over-current protection, the over-current setting value and time setting value of each stage are independently set. When any phase current is greater than the over-current setting value and reaches the time setting value of each stage of the three-stage protection, the protection circuit operates. The main criterion includes: I max >I nzd , where I max is the maximum phase current, and I nzd is the over-current setting value of each stage.

[0012] Further, the logic for correct judgment of inrush current blocking includes: when the second-harmonic braking element determines that the second-harmonic content is greater than the setting value, the inrush current blocking analysis and judgment are completed, and the over-current protection function is blocked; otherwise, the inrush current blocking judgment is correct, and the over-current protection function is opened. The action criterion of the second-harmonic braking element is I2 > K * I1, where I1 and I2 are the amplitudes of the fundamental wave component and the second-harmonic component in the phase current respectively, and K is the second-harmonic braking ratio, which is set according to the minimum second-harmonic content under various inrush currents.

[0013] Further, the three-stage over-current protection also includes a low-voltage blocking logic. When the low-voltage blocking logic judgment is correct, the low-voltage blocking is opened. The low-voltage blocking logic includes that when it is detected that all line voltages are greater than the low-voltage setting value U Lbs , the over-current protection function is blocked. The action criterion of the low-voltage blocking element is U min ≤U Lbs , where U min is the minimum line voltage. In the first-stage protection, when the line voltage is lower than 70% of the rated value, the over-current protection function is blocked. In the second-stage protection, when the line voltage is lower than 60% of the rated value, the over-current protection function is blocked, but the protection action delay is shortened to prevent misoperation. In the third-stage protection, when the line voltage is lower than 50% of the rated value, the over-current protection function is blocked, but the protection action delay is increased as a backup.

[0014] Further, the direction blocking judgment is made through the following logic. The direction blocking is embedded in the three-stage protection method. Only when a fault occurs in the positive direction, the direction blocking judgment is correct, and the first-stage protection is opened. When a fault occurs on the same line segment, the second-stage protection is opened. The direction blocking logic includes that when the power direction is positive, the first-stage overcurrent protection function is opened, and when the power direction is negative, the overcurrent protection function is blocked. When the corresponding bus PT is disconnected, the direction blocking will be withdrawn. The judgment basis for a positive-direction fault is as follows: when the direction setting is 0 and the power direction is from the bus to the line, when the absolute value of the power angle is less than 85°, it is a positive direction, and when the absolute value of the power angle is greater than 90°, it is a negative direction; when the direction setting is 1 and the power direction is from the line to the bus, when the absolute value of the power angle is greater than 95°, it is a positive direction, and when the absolute value of the power angle is less than 90°, it is a negative direction.

[0015] Further, the zero-sequence overcurrent protection adopts a three-stage protection scheme, including the first-stage instantaneous zero-sequence current cut-off protection, the second-stage time-limited zero-sequence current cut-off protection, and the third-stage zero-sequence overcurrent protection. The main criterion for the zero-sequence overcurrent protection is: 3I0 > I 0zd , where 3I0 is the zero-sequence current and I 0zd is the zero-sequence overcurrent setting value. When the zero-sequence current exceeds the zero-sequence overcurrent setting value, the first-stage protection is triggered. When the first-stage overcurrent protection is triggered and the zero-sequence current is detected to continue to exist, the second-stage protection is triggered. When the zero-sequence current still exists after the second-stage protection is triggered, the third-stage protection is triggered.

[0016] The action judgment logic of the zero-sequence overcurrent protection also includes the zero-sequence power direction blocking logic and the positive-direction fault judgment logic.

[0017] The zero-sequence power direction blocking logic is as follows: Only when the zero-sequence power direction is positive is the protection action allowed. When the zero-sequence power direction is negative, the zero-sequence overcurrent protection function is blocked. When the corresponding bus PT is disconnected and the zero-sequence voltage generation method is self-produced, the direction blocking will be withdrawn.

[0018] The positive-direction fault judgment logic is as follows: when the direction setting is 0 and the power direction is from the bus to the line, when the absolute value of the power angle is less than 85°, it is a positive direction, and when the absolute value of the power angle is greater than 90°, it is a negative direction; when the direction setting is 1 and the power direction is from the line to the bus, when the absolute value of the power angle is greater than 95°, it is a positive direction, and when the absolute value of the power angle is less than 90°, it is a negative direction.

[0019] Further, the various setting values used for the protection judgment of the zero-sequence overcurrent protection include the overcurrent setting value and the direction angle blocking setting value. The zero-sequence overcurrent setting value includes the zero-sequence overcurrent I-section current setting value, the zero-sequence overcurrent I-section direction angle blocking setting value, the zero-sequence overcurrent II-section current setting value, the zero-sequence overcurrent II-section direction angle blocking setting value, the zero-sequence overcurrent III-section current setting value, and the zero-sequence overcurrent III-section direction angle blocking setting value.

[0020] Further, it also includes setting overload current and overload time limit alarms, and / or setting overcurrent and overcurrent time limit alarms.

[0021] Further, it also includes active power reduction protection, and the active power reduction protection includes:

[0022] Setting a current limiting threshold I XL and a voltage reduction threshold U XL , where the current limiting threshold is less than the overcurrent section I current setting value I 1zd ;

[0023] Series-connected an adjustable load between the emergency power supply system open-circuit protection device and the user load;

[0024] When the measured emergency power supply current I SC is less than the current limiting threshold, control the load value of the adjustable load to be zero; when the measured emergency power supply current is greater than or equal to the current limiting threshold, control the load value of the adjustable load to increase with the increase of the current, and control the supply voltage of the user load to be not lower than the voltage reduction threshold.

[0025] Further, the voltage reduction threshold is greater than or equal to 50% of the rated voltage of the low-voltage distribution network. When it is detected that the measured supply current exceeds the current limiting threshold and the voltage reduction threshold is less than or equal to the low-voltage setting value U Lbs , close the judgment step of the low-voltage blocking logic and the undervoltage protection mechanism.

[0026] Further, the load value R of the adjustable load XL = K XL *(I SC - I XL ), where K XL is the current limiting load adjustment coefficient, and K XL ≤(U0 - U XL ) / (I 1zd *(I 1zd - I XL ))), where U0 is the rated voltage of the system power supply.

[0027] Further, the current limiting threshold is set not to exceed 4 / 5 of the overcurrent section I current setting value and is greater than the system normal power supply rated current value.

[0028] Further, the active power reduction protection method also includes setting a protection time limit, and the protection time limit does not exceed the shortest value among the longest continuous working time limits allowed under low voltage for all emergency power supply loads. The emergency power supply loads are the user loads powered by the emergency power supply after a fault.

[0029] Based on the same inventive concept, the present invention also provides an emergency power supply overcurrent protection system, including:

[0030] Three-stage overcurrent protection module, used to implement three-stage overcurrent protection, including:

[0031] The operation logic of the first-stage protection is: when the current exceeds the overcurrent setting value of the first-stage overcurrent, and the inrush current blocking judgment is correct, and the directional blocking judgment is correct, and the voltage is normal, trigger the first-stage overcurrent protection action;

[0032] The operation logic of the second-stage protection is: when the current exceeds the overcurrent setting value of the second-stage overcurrent, and the directional blocking judgment is correct, and the voltage is not lower than the preset rated value, the low-voltage blocking is opened, and the second-stage overcurrent protection action is triggered after a preset delay;

[0033] The operation logic of the third-stage protection is: when the current exceeds the overcurrent setting value of the third-stage overcurrent, and the directional blocking judgment is correct, and the voltage is not lower than the preset rated value, the low-voltage blocking is opened, and the third-stage overcurrent protection action is triggered after a preset delay;

[0034] Zero-sequence overcurrent protection module, used to implement zero-sequence overcurrent protection logic.

[0035] Further, for the three-stage overcurrent protection, the overcurrent setting value and time setting value of each stage are independently set. When any phase current is greater than the overcurrent setting value and reaches the time setting value of each stage of the three-stage protection, the protection circuit operates. The main criterion includes: I max >I nzd , where I max is the maximum phase current, and I nzd is the overcurrent setting value of each stage.

[0036] Further, the logic for correct inrush current blocking judgment includes: when the second-harmonic braking element determines that the second-harmonic content is greater than the setting value, the inrush current blocking analysis and judgment are completed, and the overcurrent protection function is blocked. Otherwise, the inrush current blocking judgment is correct, and the overcurrent protection function is open; the action criterion of the second-harmonic braking element is I2 > K * I1, where I1 and I2 are the amplitudes of the fundamental wave component and the second-harmonic component in the phase current respectively, and K is the second-harmonic braking ratio, which is set according to the minimum second-harmonic content under various inrush currents.

[0037] Further, the three-stage overcurrent protection also includes a low-voltage blocking logic. When the low-voltage blocking logic is judged correctly, the low-voltage blocking is opened; the low-voltage blocking logic includes that when it is detected that all line voltages are greater than the low-voltage setting value U Lbs , the overcurrent protection function is blocked; the action criterion of the low-voltage blocking element is U min ≤U Lbs , where U minis the minimum line voltage. When the line voltage in a section of protection is lower than 70% of the rated value, the overcurrent protection function is blocked; when the line voltage in the second section of protection is lower than 60% of the rated value, the overcurrent protection function is blocked, but the protection action delay is shortened to prevent misoperation; when the line voltage in the third section of protection is lower than 50% of the rated value, the overcurrent protection function is blocked, but the protection action delay is increased as a backup.

[0038] Further, the direction blocking judgment is carried out through the following logic. The direction blocking is embedded in the three-stage protection method. Only when the fault is in the positive direction, the direction blocking judgment is correct, and the first-stage protection is opened. When the fault occurs on the same section of the line, the second-stage protection is opened; among them, the direction blocking logic includes that when the power direction is positive, the first-stage overcurrent protection function is opened, and when the power direction is negative, the overcurrent protection function is blocked. When the corresponding bus PT is disconnected, the direction blocking will be withdrawn; the basis for judging the positive direction fault is: when the direction setting is 0 and the power direction is from the bus to the line, when the absolute value of the power angle is less than 85°, it is the positive direction, and when the absolute value of the power angle is greater than 90°, it is the negative direction; when the direction setting is 1 and the power direction is from the line to the bus, when the absolute value of the power angle is greater than 95°, it is the positive direction, and when the absolute value of the power angle is less than 90°, it is the negative direction.

[0039] Further, the zero-sequence overcurrent protection module also adopts a three-stage protection scheme in the zero-sequence overcurrent protection, including the first-stage instantaneous zero-sequence current quick-break protection, the second-stage time-limited zero-sequence current quick-break protection, and the third-stage zero-sequence overcurrent protection. The main criterion for the zero-sequence overcurrent protection is: 3I0 > I 0zd where 3I0 is the zero-sequence current and I 0zd is the zero-sequence overcurrent setting value; when the zero-sequence current exceeds the zero-sequence overcurrent setting value, the first-stage protection is triggered. When the first-stage overcurrent protection is triggered and the zero-sequence current is detected to continue to exist, the second-stage protection is triggered. When the second-stage protection is triggered and the zero-sequence current still exists, the third-stage protection is triggered;

[0040] The zero-sequence overcurrent protection action judgment logic also includes the zero-sequence power direction blocking logic and the positive direction fault judgment logic;

[0041] The zero-sequence power direction blocking logic is: only when the zero-sequence power direction is positive is the protection action allowed. When the zero-sequence power direction is negative, the zero-sequence overcurrent protection function is blocked. When the corresponding bus PT is disconnected and the zero-sequence voltage generation method is self-produced, the direction blocking will be withdrawn;

[0042] The positive direction fault judgment logic is: when the direction setting is 0 and the power direction is from the bus to the line, when the absolute value of the power angle is less than 85°, it is the positive direction, and when the absolute value of the power angle is greater than 90°, it is the negative direction; when the direction setting is 1 and the power direction is from the line to the bus, when the absolute value of the power angle is greater than 95°, it is the positive direction, and when the absolute value of the power angle is less than 90°, it is the negative direction.

[0043] Further, the various setting values used for the protection judgment of the zero-sequence over-current protection include the over-current setting value and the directional angle locking setting value. The zero-sequence over-current setting values include the zero-sequence over-current stage I current setting value, the zero-sequence over-current stage I directional angle locking setting value, the zero-sequence over-current stage II current setting value, the zero-sequence over-current stage II directional angle locking setting value, the zero-sequence over-current stage III current setting value, and the zero-sequence over-current stage III directional angle locking setting value.

[0044] Further, it also includes setting heavy-load current and heavy-load time-limit alarms, and / or setting overload current and overload time-limit alarms.

[0045] Further, it also includes active power reduction protection, and the active power reduction protection includes:

[0046] Setting a current-limiting threshold I XL and a voltage reduction threshold U XL , where the current-limiting threshold is less than the over-current stage I current setting value I 1zd ;

[0047] Series-connected an adjustable load between the emergency power supply system circuit breaker protection device and the user load;

[0048] When the measured emergency power supply current I SC is less than the current-limiting threshold, control the load value of the adjustable load to be zero; when the measured emergency power supply current is greater than or equal to the current-limiting threshold, control the load value of the adjustable load to increase with the increase of the current, and control the supply voltage of the user load to be not lower than the voltage reduction threshold.

[0049] Further, the voltage reduction threshold is greater than or equal to 50% of the rated voltage of the low-voltage distribution network. When it is detected that the measured supply current exceeds the current-limiting threshold and the voltage reduction threshold is less than or equal to the low-voltage setting value U Lbs , close the judgment step of the low-voltage locking logic and the under-voltage protection mechanism.

[0050] Further, the load value R XL of the adjustable load = K XL *(I SC -I XL ), where K XL is the current-limiting load adjustment coefficient, and K XL ≤(U0 - U XL ) / (I 1zd *(I 1zd -I XL ))), where U0 is the rated system supply voltage.

[0051] Further, the current-limiting threshold is set not to exceed 4 / 5 of the over-current stage I current setting value and is greater than the system normal supply rated current value.

[0052] Further, the active power reduction protection method further includes setting a protection time limit, which does not exceed the shortest value among the longest continuous working time limits allowed under low voltage for all emergency power supply loads, and the emergency power supply loads are user loads powered by the emergency power supply after a fault.

[0053] Based on the same inventive concept, the present invention further provides a computing device, including: one or more processors, one or more memories, and one or more programs, where the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the overcurrent protection method for the emergency power supply according to any one of the above are implemented.

[0054] Based on the same inventive concept, the present invention further provides a storage medium, which stores a computer program, and the computer program includes program instructions, and when the program instructions are executed by a processor, the processor is caused to execute the steps of the overcurrent protection method for the emergency power supply according to any one of the above.

[0055] Beneficial effects: Compared with the prior art, an overcurrent protection method for an emergency power supply designed by the present invention fully considers the special application requirements of the emergency power supply, and tries to ensure the power supply of the equipment as much as possible in possible situations. Specifically, by embedding a three-stage protection method into the analysis and judgment of overcurrent, inrush current locking, low voltage locking, directional locking, and zero-sequence overcurrent protection, and by connecting an adjustable load in series between the circuit breaker protection device and the user load, actively reducing the power output of the emergency power supply to the emergency power supply load, and alarming for manual emergency handling, in order to reduce the probability of mis-shutdown of the power supply system and achieve reasonable protection for this special application of the emergency power supply, rather than simply directly using the power-off method for protection; the power supply guarantee performance and continuous power supply ability of the emergency power supply system can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic diagram of the three-stage overcurrent protection logic according to an embodiment of the present invention;

[0057] Figure 2 It is a schematic diagram of the zero-sequence overcurrent protection logic according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0058] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0059] Embodiment 1, as shown in the attached Figure 1 figure, the overcurrent protection method for the emergency power supply in this embodiment includes: three-stage overcurrent protection and zero-sequence overcurrent protection;

[0060] The three-stage overcurrent protection includes:

[0061] The action logic of the first-stage protection is: when the current exceeds the overcurrent setting value of the first-stage overcurrent, the inrush current blocking judgment is correct, the directional blocking judgment is correct, and the voltage is normal, triggering the first-stage overcurrent protection action;

[0062] The action logic of the second-stage protection is: when the current exceeds the overcurrent setting value of the second-stage overcurrent, the directional blocking judgment is correct, and the voltage is not lower than 60% of the rated value, the low-voltage blocking is opened, and the second-stage overcurrent protection action is triggered after a preset delay;

[0063] The action logic of the third-stage protection is: when the current exceeds the overcurrent setting value of the third-stage overcurrent, the directional blocking judgment is correct, and the voltage is not lower than 50% of the rated value, the low-voltage blocking is opened, and the third-stage overcurrent protection action is triggered after a preset delay;

[0064] The zero-sequence overcurrent protection is used to implement the zero-sequence overcurrent protection logic.

[0065] Among them, the setting values used for the first-stage protection action logic judgment include the overcurrent setting value of the first-stage overcurrent, the inrush current blocking setting value of the first-stage overcurrent (used to determine the correct inrush current blocking judgment by judging the second-harmonic content. When the second-harmonic content is greater than the setting value, the overcurrent protection function is blocked), the directional angle blocking setting value of the first-stage overcurrent (that is, only when a positive-direction fault occurs, the directional blocking judgment is correct), and the low-voltage blocking setting value of the first-stage overcurrent (70% of the system voltage rated value. If the voltage is not lower than 70% of the rated value, it is judged that the voltage is normal and the low-voltage blocking is opened).

[0066] The setting values used for the second-stage protection action logic judgment include the current setting value of the second-stage overcurrent, the directional angle blocking setting value of the second-stage overcurrent (the low-voltage blocking setting value of the second-stage overcurrent (that is, when a fault occurs on the same line segment, the directional blocking judgment is correct), and the low-voltage blocking setting value of the second-stage overcurrent (60% of the system voltage rated value. If the voltage is not lower than 60% of the rated value, the low-voltage blocking is opened).

[0067] The overcurrent setting value of the third-stage overcurrent, the low-voltage blocking setting value of the third-stage overcurrent (50% of the system voltage rated value. If the voltage is not lower than 50% of the rated value, the low-voltage blocking is opened), and the directional angle blocking setting value of the third-stage overcurrent (that is, when a fault occurs on the same line segment, including adjacent line faults, the directional blocking judgment is correct, as a backup).

[0068] Specifically, in the three-stage overcurrent protection, the three-stage overcurrent protection includes a set of protection methods composed of the current quick-break protection (the first-stage overcurrent), the time-limited current quick-break protection (the second-stage overcurrent), and the definite-time overcurrent protection (the third-stage overcurrent) cooperating with each other.

[0069] In the three-stage overcurrent protection, the overcurrent setting value and time setting value of each stage are independently set. When the current of any phase is greater than the overcurrent setting value and reaches the time setting value of each stage (primary protection: 0 s, secondary protection: 0.2 s, tertiary protection: 2 s), the protection circuit operates;

[0070] The main criterion of the three-stage overcurrent protection includes: I max >I nzd , where I max is the maximum phase current, and I nzd is the overcurrent setting value of each stage; Figure 1 An "AND gate" judgment condition of I zd ≥0.05 is set, that is, the minimum current value of I nzd (i.e., I zd ) should meet the limit requirements during overcurrent judgment. If the current is too small, there is no meaning in judging protection;

[0071] The correct logic for locking out inrush current includes: when the second-harmonic braking element determines that the second-harmonic content is greater than the setting value, the inrush current locking analysis and judgment are completed, and the overcurrent protection function is locked out. Otherwise, the inrush current locking judgment is correct, and the overcurrent protection function is enabled; the action criterion of the second-harmonic braking element is I2>K*I1, where I1 and I2 are the amplitudes of the fundamental wave component and the second-harmonic component in the phase current respectively, and K is the second-harmonic braking ratio, which is set according to the minimum second-harmonic content under various inrush currents. When the second-harmonic braking element determines that the second-harmonic content is greater than the setting value, the inrush current locking analysis and judgment are completed, and the overcurrent protection function is locked out; this design is to prevent the misoperation of overcurrent protection caused by inrush current. According to the characteristic that inrush current contains a large amount of second-harmonic components, the second-harmonic braking logic is added. In the figure, "harmonic braking control word = 1" means that the "inrush current locking logic" is allowed, and the meaning of other "protection trip control word = 1" is similar; I A1 , I A2 , I B1 , I B2 , I C1 , I C2 are the amplitudes of the fundamental wave component and the second-harmonic component in the phase current of the three-phase electricity of A, B, and C respectively, and U AB , U BC , U CA are the voltage values between any two of the three-phase electricity respectively; Tzd is the logic delay time;

[0072] The three-stage overcurrent protection also includes a low-voltage locking logic. When the low-voltage locking logic is judged correctly, the low-voltage locking is enabled; the low-voltage locking logic: when it is detected that all line voltages are greater than the low-voltage setting value U Lbs , the overcurrent protection function is locked out; the action criterion of the low-voltage locking element is U min ≤ULbs , where U min is the minimum line voltage. When the line voltage in a section of protection is lower than 70% of the rated value, the overcurrent protection function is blocked; when the line voltage in the second section of protection is lower than 60% of the rated value, the overcurrent protection function is blocked, but the protection action delay is shortened to prevent misoperation; when the line voltage in the third section of protection is lower than 50% of the rated value, the overcurrent protection function is blocked, but the protection action delay is increased as a backup. This design is to prevent misoperation of the protection in non-fault situations where the current instantaneously increases but the voltage changes little. Therefore, a low-voltage blocking logic is added, that is, even if the current in the system is large, as long as the load does not lose voltage too low, it can still continue to work.

[0073] The direction blocking judgment is correct through the following logic. The direction blocking logic is that the direction blocking judgment is correct only for positive-direction faults, and the first-section protection is opened. For faults on the same section of the line, the second-section protection is opened: when the power direction is positive, the first-section overcurrent protection function is opened, and when the power direction is negative, the overcurrent protection function is blocked. When the corresponding bus PT (voltage transformer) is disconnected, the direction blocking will be withdrawn; the basis for positive-direction fault judgment is: when the direction indication is set to 0 (the direction of power is from the bus to the line), when the absolute value of the power angle is less than 85°, it is the positive direction, and when the absolute value of the power angle is greater than 90°, it is the negative direction; when the direction indication is set to 1 (the direction of power is from the line to the bus), when the absolute value of the power angle is greater than 95°, it is the positive direction, and when the absolute value of the power angle is less than 90°, it is the negative direction. This design is to achieve the directionality and selectivity of the protection action, so a direction blocking logic is added.

[0074] The zero-sequence overcurrent protection includes the traditional zero-sequence overcurrent protection logic.

[0075] Preferably, the overcurrent setting values include the overcurrent setting value of the first section of overcurrent (i.e., the overcurrent setting value of the first section, and the same for others), the inrush current blocking setting value of the first section of overcurrent, the low-voltage blocking setting value of the first section of overcurrent, the direction angle blocking setting value of the first section of overcurrent, the current setting value of the second section of overcurrent, the low-voltage blocking setting value of the second section of overcurrent, the direction angle blocking setting value of the second section of overcurrent, the current setting value of the third section of overcurrent, the low-voltage blocking setting value of the third section of overcurrent, the direction angle blocking setting value of the third section of overcurrent; the time setting values include the time limit of the first section of overcurrent, the time limit of the second section of overcurrent, and the time limit of the third section of overcurrent. The specific values of the above settings and time limits are generally set according to factors such as the capacity of the emergency power supply, the maximum load current that can be provided, and the actual load power. The implementation tools of the method, such as the corresponding application software or system, generally should provide an interface for parameter configuration.

[0076] This embodiment is for the NMC8631 type emergency power access device, configured with a 500 kWh lithium iron phosphate battery pack, applicable to application scenarios such as switching stations, distribution substations, ring main units, box-type substations, pole-mounted switches, and distribution transformers at 10 kV and below. It can be installed near the controlled primary equipment to achieve the uninterrupted connection and disconnection of energy storage vehicles / diesel generators on-site, realizing "zero" perception operation and maintenance for users. When the load power does not exceed 100 kW, the typical set values of the above fixed values and time limits are as follows: the overcurrent stage I current setting value is 5 kA, the overcurrent stage I inrush current blocking setting value is 7 kA, the overcurrent stage I low voltage blocking setting value is 280 V, the overcurrent stage I direction angle blocking setting value is 45°, the overcurrent stage II current setting value is 1 kA, the overcurrent stage II inrush current blocking setting value is 3 kA, the overcurrent stage II low voltage blocking setting value is 240 V, the overcurrent stage II direction angle blocking setting value is 45°, the overcurrent stage III current setting value is 400 A, the overcurrent stage III inrush current blocking setting value is 600 A, the overcurrent stage III low voltage blocking setting value is 200 V, the overcurrent stage III direction angle blocking setting value is 45°; the overcurrent stage I time limit is 0.1 s, the overcurrent stage II time limit is 0.5 s, and the overcurrent stage III time limit is 1 s.

[0077] In the grounding system, the system grounded through a small resistor, or in an ungrounded system with more cable outages, the grounding zero-sequence current is relatively large, and zero-sequence overcurrent protection can be used as the grounding protection. When the zero-sequence current is greater than the zero-sequence overcurrent setting value and reaches its time limit, it operates.

[0078] Embodiment 2 is different from Embodiment 1 in that, as Figure 2 shown, the zero-sequence overcurrent protection adopts a three-stage protection scheme, which is composed of a non-time-limited zero-sequence current quick-break protection (stage I), a time-limited zero-sequence current quick-break protection (stage II), and a zero-sequence overcurrent protection (stage III) cooperating with each other, including:

[0079] The main criterion of the zero-sequence overcurrent protection is: 3I0 > I0zd, where 3I0 is the zero-sequence current and I0zd is the zero-sequence overcurrent setting value. When the zero-sequence current exceeds the zero-sequence overcurrent setting value, the first-stage protection is triggered. When it is detected that the zero-sequence current persists, the second-stage protection is triggered. The third-stage protection is used to confirm the second-stage protection. When the zero-sequence current still exists after the second-stage protection is triggered, the third-stage protection is triggered.

[0080] The zero-sequence overcurrent protection action judgment logic also includes a zero-sequence power direction blocking logic and a positive-direction fault judgment logic.

[0081] Zero-sequence power direction blocking logic: To achieve the directionality and selectivity of protection actions, a direction blocking logic is added. The protection action is allowed only when the zero-sequence power direction is positive. When the zero-sequence power direction is negative, the zero-sequence overcurrent protection function is blocked. When the corresponding bus PT is disconnected and the zero-sequence voltage generation method is self-generated, the direction blocking will be withdrawn. The positive-direction fault judgment logic is as follows: When the direction setting is 0 (the power direction is from the bus to the line), when the absolute value of the power angle is less than 85°, it is the positive direction, and when the absolute value of the power angle is greater than 90°, it is the negative direction; when the direction setting is 1 (the power direction is from the line to the bus), when the absolute value of the power angle is greater than 95°, it is the positive direction, and when the absolute value of the power angle is less than 90°, it is the negative direction. Figure 2 In the zero-sequence voltage self-generation, it means that when a single-phase ground fault occurs in an ungrounded neutral system, the zero-sequence voltages U A0 , U B0 , U C0 are in the opposite direction to the potential direction of the fault phase, and are in the same direction and equal to the vector sum of other non-fault phases, that is, U A0 , U B0 , U C0 are in the same direction (the zero-sequence is always in the same direction), and the zero-sequence voltage measured by the open delta is the vector sum of the three.

[0082] Preferably, the overcurrent setting values include the zero-sequence overcurrent stage I current setting value, the zero-sequence overcurrent stage I direction angle blocking setting value, the zero-sequence overcurrent stage II current setting value, the zero-sequence overcurrent stage II direction angle blocking setting value, the zero-sequence overcurrent stage III current setting value, and the zero-sequence overcurrent stage III direction angle blocking setting value; the time setting values include the zero-sequence overcurrent stage I time limit, the zero-sequence overcurrent stage II time limit, and the zero-sequence overcurrent stage III time limit.

[0083] The zero-sequence overcurrent stage I direction angle blocking setting value (i.e., when only a positive-direction fault occurs, the direction blocking judgment is correct) is used to judge whether the zero-sequence overcurrent stage I protection operates. The zero-sequence overcurrent stage II direction angle blocking setting value (i.e., when a fault occurs on the same section of the line, the direction blocking judgment is correct) is used to judge whether the zero-sequence overcurrent stage II protection operates. The zero-sequence overcurrent stage III direction angle blocking setting value is used to judge whether the zero-sequence overcurrent stage III protection operates (i.e., when a fault occurs on the same section of the line, including adjacent line faults, the direction blocking judgment is correct, as a backup).

[0084] In this embodiment, the above typical values of the zero-sequence overcurrent setting values and time limits are set as follows: the zero-sequence overcurrent stage I current setting value is 4 kA, the zero-sequence overcurrent stage I direction angle blocking setting value is 120°, the zero-sequence overcurrent stage II current setting value is 1.5 kA, the zero-sequence overcurrent stage II direction angle blocking setting value is 120°, the zero-sequence overcurrent stage III current setting value is 200 A, and the zero-sequence overcurrent stage III direction angle blocking setting value is 120°; the zero-sequence overcurrent stage I time limit is 0.1 s, the zero-sequence overcurrent stage II time limit is 0.5 s, and the zero-sequence overcurrent stage III time limit is 1.5 s.

[0085] Embodiment 3, which is different from Embodiment 1 in that the method further includes setting overload current and overload time limit alarms, and / or setting overcurrent and overcurrent time limit alarms, that is, when the measured load current exceeds the set value of the overload current for a certain time limit, the system issues an alarm signal, and / or when the measured load current exceeds the set value of the overcurrent for a certain time limit, the system issues an alarm signal.

[0086] Embodiment 4, which is different from Embodiment 1 in that the method further includes an active power reduction protection method, which reduces the power output of the emergency power supply to the emergency power supply load actively and alarms for manual emergency handling, in order to reduce the probability of mis-shutdown of the emergency power supply system. The active power reduction protection method includes setting an active current limiting threshold I XL and an active voltage reduction threshold U XL , the current limiting threshold is less than the overcurrent section I current setting value I 1zd , an adjustable load is connected in series between the backend (the end connected to the load) of the circuit breaker protection device of the emergency power supply system and the user load; the circuit breaker protection device includes a circuit breaker, etc., and the adjustable load is generally connected between the circuit breaker directly connected to the load, rather than between the main circuit breaker and the branch circuit breaker.

[0087] When the measured emergency power supply current I SC (total power supply current) is less than the current limiting threshold, control the load value of the adjustable load to be zero; when the measured emergency power supply current is greater than or equal to the current limiting threshold, control the load value of the adjustable load to increase with the increase of the current, so as to achieve the purpose of dividing the voltage of the line to slow down the current increase speed and reduce the current value, thereby buying time for manual handling. At this time, the power supply voltage of the user load will drop, and the power supply voltage of the user load should be controlled not to be lower than the voltage reduction threshold; the manual handling includes disconnecting the faulty load or replacing the faulty equipment or replacing the faulty module, etc. This design, on the one hand, restricts the increase of the current, reduces the probability of the circuit breaker action or delays the circuit breaker action time, and buys time for manual fault handling; on the other hand, ensures the power supply of the equipment under possible conditions, reduces the losses or risks brought by abnormal power supply, and can also prevent abnormal damage of the equipment.

[0088] Preferably, the voltage reduction threshold is greater than or equal to 50% of the rated voltage of the low-voltage distribution network. When it is detected that the measured power supply current exceeds the current limiting threshold and the voltage reduction threshold is less than or equal to the low-voltage setting value U Lbs , turn off the judgment step of the low-voltage blocking logic and the under-voltage protection mechanism, that is, the system no longer executes the under-voltage protection function, nor does it execute the judgment of the "low-voltage blocking logic" anymore, because the system sets another lower under-voltage protection value that can still work normally, and the overcurrent is still within the effective control range; when the voltage reduction threshold is greater than the low-voltage setting value U Lbs , both the "low-voltage blocking logic" and the under-voltage protection function are executed normally.

[0089] Preferably, the load value R of the adjustable load XL = K XL *(I SC - I XL ), where K XL is the current-limiting load adjustment coefficient, and K XL ≤ (U0 - U XL ) / (I 1zd *(I 1zd - I XL ))), where U0 is the rated voltage of the system power supply. In this embodiment, K XL = 4*(U0 - U XL ) / (5*I 1zd *(I 1zd - I XL ))). In this embodiment, a load adjustment strategy is given taking a resistive load as an example. Similar adjustment strategies can be adopted for other capacitive or inductive loads.

[0090] Preferably, the current-limiting threshold is set not exceeding 4 / 5 of the overcurrent stage I current setting value and greater than the system normal power supply rated current value. A certain margin should be left between the current-limiting threshold and the overcurrent stage I current setting value for the system to adaptively adjust. In this embodiment, the system rated current is 10A, the overcurrent stage I current setting value is 30A, and the current-limiting threshold is set to 15A.

[0091] Preferably, the active power reduction protection method further includes setting a protection time limit, which does not exceed the shortest value among the longest continuous working time limits allowed under low voltage for all emergency power supply loads. The emergency power supply loads are the user loads powered by the emergency power supply after a fault. This is the general setting principle. In actual applications, it is better to be lower on the basis of taking into account the manual emergency handling time. That is, during the effective period of active power reduction, the equipment operates under low voltage, but the continuous working time cannot be too long. It is required that manual processing be carried out as soon as possible after the system alarms, such as directly cutting off the faulty load, etc. In this embodiment, the active power reduction protection time limit is set to 15 minutes.

[0092] Embodiment 5. Based on the same inventive concept, this embodiment also provides an emergency power supply overcurrent protection system, including:

[0093] A three-stage overcurrent protection module for implementing three-stage overcurrent protection, including:

[0094] The action logic of the first-stage protection is: when the current exceeds the overcurrent stage I overcurrent setting value, and the inrush current blocking judgment is correct, and the direction blocking judgment is correct, and the voltage is normal, trigger the first-stage overcurrent protection action;

[0095] The operation logic of the second-stage protection is as follows: when the current exceeds the overcurrent setting value of the second stage of overcurrent, the direction blocking judgment is correct, and the voltage is not lower than 60% of the rated value, the low-voltage blocking is opened, and the second-stage overcurrent protection action is triggered after a preset delay;

[0096] The operation logic of the third-stage protection is as follows: when the current exceeds the overcurrent setting value of the third stage of overcurrent, the direction blocking judgment is correct, and the voltage is not lower than 50% of the rated value, the low-voltage blocking is opened, and the third-stage overcurrent protection action is triggered after a preset delay;

[0097] The zero-sequence overcurrent protection module is used to implement the zero-sequence overcurrent protection logic.

[0098] Further, for the three-stage overcurrent protection, the overcurrent setting value and time setting value of each stage are independently set. When the current of any phase is greater than the overcurrent setting value and reaches the time setting value of each stage of the three-stage protection, the protection circuit operates. The main criterion includes: I max >I nzd , where I max is the maximum phase current, and I nzd is the overcurrent setting value of each stage.

[0099] Further, the logic for correct judgment of inrush current blocking includes: when the second-harmonic braking element determines that the second-harmonic content is greater than the setting value, the analysis and judgment of inrush current blocking are completed, and the overcurrent protection function is blocked; otherwise, the judgment of inrush current blocking is correct, and the overcurrent protection function is opened; the action criterion of the second-harmonic braking element is I2>K*I1, where I1 and I2 are the amplitudes of the fundamental wave component and the second-harmonic component in the phase current respectively, and K is the second-harmonic braking ratio, which is set according to the minimum second-harmonic content under various inrush currents.

[0100] Further, the three-stage overcurrent protection also includes a low-voltage blocking logic. When the low-voltage blocking logic is judged correctly, the low-voltage blocking is opened; the low-voltage blocking logic includes that when it is detected that all line voltages are greater than the low-voltage setting value U Lbs , the overcurrent protection function is blocked; the action criterion of the low-voltage blocking element is U min ≤U Lbs , where U min is the minimum line voltage. In the first-stage protection, the overcurrent protection function is blocked when the line voltage is lower than 70% of the rated value; in the second-stage protection, the overcurrent protection function is blocked when the line voltage is lower than 60% of the rated value, but the protection action delay is shortened to prevent misoperation; in the third-stage protection, the overcurrent protection function is blocked when the line voltage is lower than 50% of the rated value, but the protection action delay is increased as a backup.

[0101] Furthermore, the directional blocking judgment is made through the following logic. The directional blocking is embedded in the three-stage protection method. Only when a positive-direction fault occurs, the directional blocking judgment is correct, and the first-stage protection is opened. When a fault occurs on the same section of the line, the second-stage protection is opened. The directional blocking logic includes that when the power direction is positive, the first-stage overcurrent protection function is opened, and when the power direction is negative, the overcurrent protection function is blocked. When the corresponding bus PT is disconnected, the directional blocking is withdrawn. The basis for the positive-direction fault judgment is as follows: when the direction indication is set to 0 and the power direction is from the bus to the line, when the absolute value of the power angle is less than 85°, it is a positive direction, and when the absolute value of the power angle is greater than 90°, it is a negative direction; when the direction indication is set to 1 and the power direction is from the line to the bus, when the absolute value of the power angle is greater than 95°, it is a positive direction, and when the absolute value of the power angle is less than 90°, it is a negative direction.

[0102] Furthermore, the setting values used for the first-stage protection action logic judgment include the overcurrent I-section overcurrent setting value, the overcurrent I-section inrush current blocking setting value (used to determine the correct inrush current blocking judgment by judging the second-harmonic content. When the second-harmonic content is greater than the setting value, the overcurrent protection function is blocked), the overcurrent I-section direction angle blocking setting value (that is, only when a positive-direction fault occurs, the directional blocking judgment is correct), and the overcurrent I-section low-voltage blocking setting value (which is 70% of the rated system voltage. If the voltage is not lower than 70% of the rated value, it is judged that the voltage is normal and the low-voltage blocking is opened).

[0103] The setting values used for the second-stage protection action logic judgment include the overcurrent II-section current setting value, the overcurrent II-section direction angle blocking setting value (the overcurrent II-section low-voltage blocking setting value (that is, when a fault occurs on the same section of the line, the directional blocking judgment is correct), and the overcurrent II-section low-voltage blocking setting value (which is 60% of the rated system voltage. If the voltage is not lower than 60% of the rated value, the low-voltage blocking is opened).

[0104] The overcurrent III-section current setting value, the overcurrent III-section low-voltage blocking setting value (which is 50% of the rated system voltage. If the voltage is not lower than 50% of the rated value, the low-voltage blocking is opened), and the overcurrent III-section direction angle blocking setting value (that is, when a fault occurs on the same section of the line, including adjacent line faults, the directional blocking judgment is correct and it serves as a backup).

[0105] Furthermore, the zero-sequence overcurrent protection module also adopts a three-stage protection scheme in the zero-sequence overcurrent protection, including the first-stage instantaneous zero-sequence current quick-break protection, the second-stage time-limited zero-sequence current quick-break protection, and the third-stage zero-sequence overcurrent protection. The main criterion for the zero-sequence overcurrent protection is: 3I0 > I 0zd where 3I0 is the zero-sequence current and I 0zd is the zero-sequence overcurrent setting value; when the zero-sequence current exceeds the zero-sequence overcurrent setting value, the first-stage protection is triggered. When the first-stage overcurrent protection is triggered and the zero-sequence current is detected to continue to exist, the second-stage protection is triggered. When the second-stage protection is triggered and the zero-sequence current still exists, the third-stage protection is triggered;

[0106] The zero-sequence over-current protection action judgment logic further includes a zero-sequence power direction blocking logic and a positive-direction fault judgment logic;

[0107] The zero-sequence power direction blocking logic is as follows: The protection action is allowed only when the zero-sequence power direction is positive. When the zero-sequence power direction is negative, the zero-sequence over-current protection function is blocked. When the corresponding bus PT is disconnected and the zero-sequence voltage generation method is self-produced, the direction blocking is withdrawn;

[0108] The positive-direction fault judgment logic is as follows: When the direction setting is 0 and the power direction is from the bus to the line, when the absolute value of the power angle is less than 85°, it is the positive direction, and when the absolute value of the power angle is greater than 90°, it is the negative direction; When the direction setting is 1 and the power direction is from the line to the bus, when the absolute value of the power angle is greater than 95°, it is the positive direction, and when the absolute value of the power angle is less than 90°, it is the negative direction.

[0109] Further, the various setting values used for the protection judgment of the zero-sequence over-current protection include an over-current setting value and a direction angle blocking setting value. The zero-sequence over-current setting values include a zero-sequence over-current section I current setting value, a zero-sequence over-current section I direction angle blocking setting value, a zero-sequence over-current section II current setting value, a zero-sequence over-current section II direction angle blocking setting value, a zero-sequence over-current section III current setting value, and a zero-sequence over-current section III direction angle blocking setting value;

[0110] The zero-sequence over-current section I direction angle blocking setting value is used to judge whether the zero-sequence over-current section I protection acts (that is, when only a positive-direction fault occurs, the direction blocking judgment is correct). The zero-sequence over-current section II direction angle blocking setting value is used to judge whether the zero-sequence over-current section II protection acts (that is, when a fault occurs on the same section of the line, the direction blocking judgment is correct). The zero-sequence over-current section III direction angle blocking setting value is used to judge whether the zero-sequence over-current section III protection acts (that is, when a fault occurs on the same section of the line, including faults on adjacent lines at the same time, the direction blocking judgment is correct, as a backup).

[0111] Further, it also includes setting a heavy-load current and a heavy-load time limit alarm, and / or setting an over-load current and an over-load time limit alarm.

[0112] Further, it also includes an active power reduction protection, and the active power reduction protection includes:

[0113] Setting a current limiting threshold I XL and a voltage reduction threshold U XL where the current limiting threshold is less than the over-current section I current setting value I 1zd ;

[0114] Connecting an adjustable load in series between the emergency power supply system disconnection protection device and the user load;

[0115] When the measured emergency power supply current I SCWhen it is less than the current limiting threshold, control the load value of the adjustable load to be zero; when the measured emergency power supply current is greater than or equal to the current limiting threshold, control the load value of the adjustable load to increase with the increase of the current, and control the supply voltage of the user load to be not lower than the step-down threshold.

[0116] Further, the step-down threshold is greater than or equal to 50% of the rated voltage of the low-voltage distribution network. When it is detected that the measured supply current exceeds the current limiting threshold and the step-down threshold is less than or equal to the low-voltage setting value U Lbs at this time, close the judgment step of the low-voltage blocking logic and the under-voltage protection mechanism.

[0117] Further, the load value R of the adjustable load XL = K XL *(I SC - I XL ), where K XL is the current limiting load adjustment coefficient, K XL ≤ (U0 - U XL ) / (I 1zd *(I 1zd - I XL ))), where U0 is the rated voltage of the system power supply.

[0118] Further, the current limiting threshold is set not to exceed 4 / 5 of the overcurrent stage I current setting value and is greater than the normal system power supply rated current value.

[0119] Further, the active power reduction protection method further includes setting a protection time limit, and the protection time limit does not exceed the shortest value among the longest continuous working time limits allowed under low voltage for all emergency power supply loads. The emergency power supply loads are user loads that are powered by the emergency power supply after a fault. Example 6. Based on the same inventive concept, this embodiment also provides a computing device, including: one or more processors, one or more memories, and one or more programs. The programs are stored in the memory and are configured to be executed by the processor. When the programs are loaded into the processor, the steps of the emergency power supply overcurrent protection method according to any one of the above are implemented.

[0120] Example 7. Based on the same inventive concept, this embodiment also provides a storage medium. The storage medium stores a computer program. The computer program includes program instructions. When the program instructions are executed by the processor, the processor executes the steps of the emergency power supply overcurrent protection method according to any one of the above.

[0121] The above are only some relatively systematic and comprehensive embodiments of the overcurrent protection method for the emergency power supply of the present invention. In fact, the preferred solutions of each embodiment can be combined, different embodiments can be recombined, and the preferred solutions of different embodiments can be combined across embodiments. For example, Embodiment 4 can be combined with Embodiment 2 to form multiple preferred embodiments. These combinations or preferred solutions should also be regarded as the protection scope of the present invention and will not be listed one by one here.

Claims

1. An emergency power supply overcurrent protection method, characterized in that: include: Three-stage overcurrent protection and zero-sequence overcurrent protection; The three-stage overcurrent protection includes: The logic of the first stage protection action is: if the current exceeds the overcurrent setting value of the overcurrent stage I and the excitation inrush current blocking judgment is correct and the direction blocking judgment is correct and the voltage is normal, the first stage overcurrent protection action is triggered; The logic of the second-stage protection action is: when the current exceeds the overcurrent setting value of the overcurrent stage II and the direction lock judgment is correct and the voltage is not lower than the preset rated value, the low-voltage lock is opened and the second-stage overcurrent protection action is triggered within the preset delay; The three-stage protection action logic is: when the current exceeds the overcurrent setting value of stage III and the direction lock judgment is correct and the voltage is not lower than the preset rated value, the low-voltage lock is opened and the three-stage overcurrent protection action is triggered within the preset delay.

2. The emergency power supply overcurrent protection method according to claim 1, characterized in that: The three-stage overcurrent protection, in which the overcurrent setting value and time setting value of each stage are independently set, when any phase current is greater than the overcurrent setting value and reaches the time setting value of each stage of the three-stage protection, the protection circuit will be activated. The main judgment criteria include: I max >I nzd , where I max is the maximum phase current, I nzd It is the overcurrent setting value for each section.

3. The emergency power supply overcurrent protection method according to claim 1, characterized in that: The logic of correct judgment of excitation inrush current lockout includes: when the second harmonic braking element judges that the second harmonic content is greater than the set value, the excitation inrush current lockout analysis and judgment is completed, and the overcurrent protection function is locked; otherwise, the excitation inrush current lockout judgment is correct and the overcurrent protection function is opened; the action criterion of the second harmonic braking element is I2>K*I1, where I1 and I2 are the amplitudes of the fundamental component and the second harmonic component in the phase current respectively, and K is the second harmonic braking ratio, which is set according to the minimum second harmonic content under avoiding various excitation inrush currents.

4. The emergency power supply overcurrent protection method according to claim 1, characterized in that: The three-stage overcurrent protection also includes a low-voltage lockout logic. When the low-voltage lockout logic is judged to be correct, the low-voltage lockout is opened; the low-voltage lockout logic includes: when it is detected that all line voltages are greater than the low-voltage setting value U Lbs The overcurrent protection function is locked when the overcurrent protection function is locked; the action criterion of the low-voltage locking element is U min ≤U Lbs , where U min It is the minimum value of line voltage. When the neutral voltage of the first-stage protection is lower than 70% of the rated value, the overcurrent protection function is locked; when the neutral voltage of the second-stage protection is lower than 60% of the rated value, the overcurrent protection function is locked, but the protection action delay is shortened to prevent false operation; when the neutral voltage of the third-stage protection is lower than 50% of the rated value, the overcurrent protection function is locked, but the protection action delay is increased as a backup.

5. The emergency power supply overcurrent protection method according to claim 1, characterized in that: Whether the direction locking judgment is correct is judged by the following logic. The direction locking of the embedded three-stage protection method is correct only when the positive direction fault occurs, and the first stage protection is opened. When the same section of the line fails, the second stage protection is opened; the direction locking logic includes that when the power direction is positive, the first stage overcurrent protection function is opened, and when the power direction is negative, the overcurrent protection function is locked. When the corresponding bus PT is broken, the direction locking will be exited; the basis for judging the positive direction fault is: when the direction pointing is set to 0, the direction of power flows from the bus to the line, the absolute value of the power angle is less than 85° for the positive direction, and the absolute value of the power angle is greater than 90° for the negative direction; when the direction pointing is set to 1, the direction of power is from the line to the bus, the absolute value of the power angle is greater than 95° for the positive direction, and the absolute value of the power angle is less than 90° for the negative direction.

6. The emergency power supply overcurrent protection method according to claim 1, characterized in that: The zero-sequence overcurrent protection adopts a three-stage protection scheme, including one stage of zero-sequence current quick-break protection without time limit, two stages of zero-sequence current quick-break protection with time limit and three stages of zero-sequence overcurrent protection, wherein the main criterion of zero-sequence overcurrent protection is: 3I0>I 0zd , where 3I0 is the zero sequence current, I 0zd It is the zero-sequence overcurrent setting value; when the zero-sequence current exceeds the zero-sequence overcurrent setting value, the first-stage protection is triggered. When the zero-sequence current continues to exist after the first-stage overcurrent protection is triggered, the second-stage protection is triggered. When the zero-sequence current still exists after the second-stage protection is triggered, the third-stage protection is triggered. The zero-sequence overcurrent protection action judgment logic also includes zero-sequence power direction blocking logic and positive direction fault judgment logic; The zero-sequence power direction blocking logic is: protection action is allowed only when the zero-sequence power direction is positive, the zero-sequence overcurrent protection function is blocked when the zero-sequence power direction is negative, and the direction blocking will be exited when the corresponding bus PT is disconnected and the zero-sequence voltage generation mode is self-generation; The positive direction fault judgment logic is: when the direction is set to 0, the direction of power flows from the bus to the line, the absolute value of the power angle is less than 85° for the positive direction, and the absolute value of the power angle is greater than 90° for the negative direction; when the direction is set to 1, the direction of power flows from the line to the bus, the absolute value of the power angle is greater than 95° for the positive direction, and the absolute value of the power angle is less than 90° for the negative direction.

7. The emergency power supply overcurrent protection method according to claim 6, characterized in that: The various constants used in the protection judgment of the zero-sequence overcurrent protection include overcurrent constants and direction angle closing constants. The zero-sequence overcurrent constants include zero-sequence overcurrent segment I current constants, zero-sequence overcurrent segment I direction angle closing constants, zero-sequence overcurrent segment II current constants, zero-sequence overcurrent segment II direction angle closing constants, zero-sequence overcurrent segment III current constants and zero-sequence overcurrent segment III direction angle closing constants.

8. The emergency power supply overcurrent protection method according to claim 1, characterized in that: It also includes setting a heavy load current and a heavy load time limit alarm, and / or setting an overload current and an overload time limit alarm.

9. The emergency power supply overcurrent protection method according to claim 1, characterized in that: It also includes active power reduction protection, which includes: Set the current limit threshold I XL And the voltage drop threshold U XL , the current limiting threshold is less than the overcurrent I stage current setting value I 1zd ; An adjustable load is connected in series between the emergency power supply system circuit breaker protection device and the user load; When the measured emergency power supply current I SC When the current is less than the current limiting threshold, the load value of the adjustable load is controlled to be zero; when the measured emergency power supply current is greater than or equal to the current limiting threshold, the load value of the adjustable load is controlled to increase with the increase of the current, and the power supply voltage of the user load is controlled not to be lower than the voltage reduction threshold.

10. The emergency power supply overcurrent protection method according to claim 9, characterized in that: The voltage reduction threshold is greater than or equal to 50% of the rated voltage of the low-voltage distribution network. When it is detected that the measured power supply current exceeds the current limiting threshold and the voltage reduction threshold is less than or equal to the low-voltage setting value U Lbs When the voltage is low, the judgment step of the low voltage lockout logic and the undervoltage protection mechanism are turned off.

11. The emergency power supply overcurrent protection method according to claim 9, characterized in that: The load value R of the adjustable load XL =K XL *(I SC -I XL ), where K XL is the current limiting load regulation factor, K XL ≤(U0-U XL ) / (I 1zd *(I 1zd -I XL )), where U0 is the rated voltage of the system power supply.

12. The emergency power supply overcurrent protection method according to claim 9, characterized in that: The current limiting threshold is set not to exceed 4 / 5 of the current setting value of overcurrent stage I, and is greater than the rated current value of the normal power supply of the system.

13. The emergency power supply overcurrent protection method according to claim 9, characterized in that: The active power reduction protection method also includes setting a protection time limit, which does not exceed the shortest value of the longest continuous working time allowed under low voltage among all emergency power supply loads. The emergency power supply load is the user load taken up by the emergency power supply after a fault.

14. An emergency power supply overcurrent protection system, characterized in that: include: The three-stage overcurrent protection module is used to implement three-stage overcurrent protection, including: The logic of the first stage protection action is: if the current exceeds the overcurrent setting value of the overcurrent stage I and the excitation inrush current blocking judgment is correct and the direction blocking judgment is correct and the voltage is normal, the first stage overcurrent protection action is triggered; The logic of the second-stage protection action is: when the current exceeds the overcurrent setting value of the overcurrent stage II and the direction lock judgment is correct and the voltage is not lower than the preset rated value, the low-voltage lock is opened and the second-stage overcurrent protection action is triggered within the preset delay; The three-stage protection action logic is: when the current exceeds the overcurrent setting value of stage III and the direction lockout judgment is correct and the voltage is not lower than the preset rated value, the low-voltage lockout is opened and the three-stage overcurrent protection action is triggered within the preset delay; The zero-sequence overcurrent protection module is used to implement the zero-sequence overcurrent protection logic.

15. The emergency power supply overcurrent protection system according to claim 14, characterized in that: The three-stage overcurrent protection, in which the overcurrent setting value and time setting value of each stage are independently set, when any phase current is greater than the overcurrent setting value and reaches the time setting value of each stage of the three-stage protection, the protection circuit will be activated. The main judgment criteria include: I max >I nzd , where I max is the maximum phase current, I nzd It is the overcurrent setting value for each section.

16. The emergency power supply overcurrent protection system according to claim 14, characterized in that: The logic of correct judgment of excitation inrush current lockout includes: when the second harmonic braking element judges that the second harmonic content is greater than the set value, the excitation inrush current lockout analysis and judgment is completed, and the overcurrent protection function is locked; otherwise, the excitation inrush current lockout judgment is correct and the overcurrent protection function is opened; the action criterion of the second harmonic braking element is I2>K*I1, where I1 and I2 are the amplitudes of the fundamental component and the second harmonic component in the phase current respectively, and K is the second harmonic braking ratio, which is set according to the minimum second harmonic content under avoiding various excitation inrush currents.

17. The emergency power supply overcurrent protection system according to claim 14, characterized in that: The three-stage overcurrent protection also includes a low-voltage lockout logic. When the low-voltage lockout logic is judged to be correct, the low-voltage lockout is opened; the low-voltage lockout logic includes: when it is detected that all line voltages are greater than the low-voltage setting value U Lbs The overcurrent protection function is locked when the overcurrent protection function is locked; the action criterion of the low-voltage locking element is U min ≤U Lbs , where U min It is the minimum value of line voltage. When the neutral voltage of the first-stage protection is lower than 70% of the rated value, the overcurrent protection function is locked; when the neutral voltage of the second-stage protection is lower than 60% of the rated value, the overcurrent protection function is locked, but the protection action delay is shortened to prevent false operation; when the neutral voltage of the third-stage protection is lower than 50% of the rated value, the overcurrent protection function is locked, but the protection action delay is increased as a backup.

18. The emergency power supply overcurrent protection system according to claim 14, characterized in that: Whether the direction locking judgment is correct is judged by the following logic. The direction locking of the embedded three-stage protection method is correct only when the positive direction fault occurs, and the first stage protection is opened. When the same section of the line fails, the second stage protection is opened; the direction locking logic includes that when the power direction is positive, the first stage overcurrent protection function is opened, and when the power direction is negative, the overcurrent protection function is locked. When the corresponding bus PT is broken, the direction locking will be exited; the basis for judging the positive direction fault is: when the direction pointing is set to 0, the direction of power flows from the bus to the line, the absolute value of the power angle is less than 85° for the positive direction, and the absolute value of the power angle is greater than 90° for the negative direction; when the direction pointing is set to 1, the direction of power is from the line to the bus, the absolute value of the power angle is greater than 95° for the positive direction, and the absolute value of the power angle is less than 90° for the negative direction.

19. The emergency power supply overcurrent protection system according to claim 14, characterized in that: The zero-sequence overcurrent protection module also includes a three-stage protection scheme in the zero-sequence overcurrent protection, including a one-stage zero-sequence current quick-break protection without time limit, a two-stage zero-sequence current quick-break protection with time limit and a three-stage zero-sequence overcurrent protection, wherein the main criterion of the zero-sequence overcurrent protection is: 3I0>I 0zd , where 3I0 is the zero sequence current, I 0zd It is the zero-sequence overcurrent setting value; when the zero-sequence current exceeds the zero-sequence overcurrent setting value, the first-stage protection is triggered. When the zero-sequence current continues to exist after the first-stage overcurrent protection is triggered, the second-stage protection is triggered. When the zero-sequence current still exists after the second-stage protection is triggered, the third-stage protection is triggered. The zero-sequence overcurrent protection action judgment logic also includes zero-sequence power direction blocking logic and positive direction fault judgment logic; The zero-sequence power direction blocking logic is: protection action is allowed only when the zero-sequence power direction is positive, the zero-sequence overcurrent protection function is blocked when the zero-sequence power direction is negative, and the direction blocking will be exited when the corresponding bus PT is disconnected and the zero-sequence voltage generation mode is self-generation; The positive direction fault judgment logic is: when the direction is set to 0, the direction of power flows from the bus to the line, the absolute value of the power angle is less than 85° for the positive direction, and the absolute value of the power angle is greater than 90° for the negative direction; when the direction is set to 1, the direction of power flows from the line to the bus, the absolute value of the power angle is greater than 95° for the positive direction, and the absolute value of the power angle is less than 90° for the negative direction.

20. The emergency power supply overcurrent protection system according to claim 19, characterized in that: The various constants used in the protection judgment of the zero-sequence overcurrent protection include overcurrent constants and direction angle closing constants. The zero-sequence overcurrent constants include zero-sequence overcurrent segment I current constants, zero-sequence overcurrent segment I direction angle closing constants, zero-sequence overcurrent segment II current constants, zero-sequence overcurrent segment II direction angle closing constants, zero-sequence overcurrent segment III current constants and zero-sequence overcurrent segment III direction angle closing constants.

21. The emergency power supply overcurrent protection system according to claim 14, characterized in that: It also includes setting a heavy load current and a heavy load time limit alarm, and / or setting an overload current and an overload time limit alarm.

22. The emergency power supply overcurrent protection system according to claim 14, characterized in that: It also includes active power reduction protection, which includes: Set the current limit threshold I XL And the voltage drop threshold U XL , the current limiting threshold is less than the overcurrent I stage current setting value I 1zd ; An adjustable load is connected in series between the emergency power supply system circuit breaker protection device and the user load; When the measured emergency power supply current I SC When the current is less than the current limiting threshold, the load value of the adjustable load is controlled to be zero; when the measured emergency power supply current is greater than or equal to the current limiting threshold, the load value of the adjustable load is controlled to increase with the increase of the current, and the power supply voltage of the user load is controlled not to be lower than the voltage reduction threshold.

23. The emergency power supply overcurrent protection system according to claim 22, characterized in that: The voltage reduction threshold is greater than or equal to 50% of the rated voltage of the low-voltage distribution network. When it is detected that the measured power supply current exceeds the current limiting threshold and the voltage reduction threshold is less than or equal to the low-voltage setting value U Lbs When the voltage is low, the judgment step of the low voltage lockout logic and the undervoltage protection mechanism are turned off.

24. The emergency power supply overcurrent protection system according to claim 22, characterized in that: The load value R of the adjustable load XL =K XL *(I SC -I XL ), where K XL is the current limiting load regulation factor, K XL ≤(U0-U XL ) / (I 1zd *(I 1zd -I XL )), where U0 is the rated voltage of the system power supply.

25. The emergency power supply overcurrent protection system according to claim 22, characterized in that: The current limiting threshold is set not to exceed 4 / 5 of the current setting value of overcurrent stage I, and is greater than the rated current value of the normal power supply of the system.

26. The emergency power supply overcurrent protection system according to claim 22, characterized in that: The active power reduction protection method also includes setting a protection time limit, which does not exceed the shortest value of the longest continuous working time allowed under low voltage among all emergency power supply loads. The emergency power supply load is the user load taken up by the emergency power supply after a fault.

27. A computing device, characterized in that include: One or more processors, one or more memories, and one or more programs, wherein the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the emergency power supply overcurrent protection method according to any one of claims 1 to 13 are implemented.

28. A storage medium, characterized in that: The storage medium stores a computer program, which includes program instructions. When the program instructions are executed by a processor, the processor executes the steps of the emergency power supply overcurrent protection method according to any one of claims 1 to 13.

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