Current differential protection method, device and equipment for energy storage power station access line

Abstract

The present invention discloses a current differential protection method, device and equipment for access lines of energy storage power stations, which relates to the field of relay protection technology and can solve the technical problem that when the access line of the energy storage is in a state of charging before a fault, the existing ratio-braked current differential protection criterion has a risk of refusal to operate and cannot isolate the fault expansion caused by the fault in the line. It includes: obtaining the system side phase current and the energy storage side phase current; in the state of charging before the energy storage fault, correcting the energy storage side phase current according to a preset phase offset angle to obtain the corrected energy storage side phase current; obtaining the reliability coefficient, formulating the target current differential protection criterion for the access line of the energy storage power station according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, and when it is judged that the energy storage is in a charging state before the fault and the target differential protection criterion is put into use, the target current differential protection criterion is used to perform current differential protection.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection, and in particular to a current differential protection method, device and equipment for access lines of energy storage power stations. Background Art

[0002] Current differential protection is a relay protection technology based on the current balance principle, which is mainly used to detect and isolate faults in power equipment or transmission lines.

[0003] The most widely used current differential protection scheme is the ratio-braked current differential protection scheme. Since the phase current characteristics provided by energy storage are significantly different from those of traditional power sources, when the energy storage is in a charging state before a fault, the existing ratio-braked current differential protection criteria will be applied to the energy storage access line. There will be a risk of refusal to operate, and the fault in the line cannot be isolated. A current differential protection method for energy storage power station access lines is urgently needed. Summary of the invention

[0004] In view of this, the present invention provides a current differential protection method, device and equipment for the access line of an energy storage power station, which can solve the technical problem that when the access line fails while the energy storage is charging before the fault, the existing ratio-braked current differential protection criterion has the risk of refusal to operate and cannot isolate the fault in the line, causing the fault to expand.

[0005] According to a first aspect of the present invention, a current differential protection method for a line accessed to an energy storage power station is provided, the method comprising:

[0006] Obtaining the phase current on the system side and the phase current on the energy storage side;

[0007] In the state of charging before the energy storage fault, the energy storage side phase current is corrected according to a preset phase offset angle to obtain a corrected energy storage side phase current;

[0008] Obtain a reliability coefficient, formulate a target current differential protection criterion for the access line of the energy storage power station according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, and perform current differential protection using the target current differential protection criterion when it is determined that the energy storage is in a charging state before a fault occurs and the target differential protection criterion is put into operation.

[0009] Preferably, the correcting the energy storage side phase current according to the preset phase offset angle to obtain the corrected energy storage side phase current includes:

[0010] The product of the preset phase offset angle and the energy storage side phase current is calculated to obtain a corrected energy storage side phase current.

[0011] Preferably, the step of formulating a target current differential protection criterion for the energy storage power station access line according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient includes:

[0012] Calculating the sum of the system side phase current and the corrected energy storage side phase current to obtain a corrected differential current;

[0013] Calculating the difference between the system side phase current and the corrected energy storage side phase current to obtain a corrected braking current;

[0014] A target current differential protection criterion for the energy storage power station access line is formulated according to the corrected differential current, the corrected braking current and the reliability coefficient.

[0015] Preferably, formulating a target current differential protection criterion for the energy storage power station access line according to the corrected differential current, the corrected braking current and the reliability coefficient includes:

[0016] determining a first absolute value of the modified differential current, and determining a second absolute value of the modified braking current;

[0017] The first absolute value being greater than the product of the reliability coefficient and the second absolute value is used as a target current differential protection criterion for the energy storage power station access line.

[0018] Preferably, when the energy storage device is in a charging state before determining that the energy storage device has a fault and the target differential protection criterion is activated, before performing current differential protection using the target current differential protection criterion, the method further includes:

[0019] Set the target current differential protection criterion and put it into the pressure plate;

[0020] When the protected line is a grid-connected energy storage power station access line, the target current differential protection criterion input pressure plate is set to 1 to indicate that the target differential protection criterion is input;

[0021] When the protected line is not a grid-connected energy storage power station access line, the target current differential protection criterion input pressure plate is set to 0 to indicate that the target differential protection criterion is not input.

[0022] Preferably, when the energy storage device is in a charging state before determining that the energy storage device has a fault and the target differential protection criterion is activated, before performing current differential protection using the target current differential protection criterion, the method further includes:

[0023] Set up a monitoring element for the charge and discharge status of energy storage before failure;

[0024] Obtain the energy storage side current phase and the energy storage side voltage phase, calculate the third absolute value of the energy storage side current phase and the energy storage side voltage phase difference, and determine whether the third absolute value is greater than 90 degrees. If so, it is determined that the energy storage is in a charging state before the failure.

[0025] According to a second aspect of the present invention, there is provided a current differential protection device for an energy storage power station access line, the device comprising:

[0026] An acquisition module, used to acquire the phase current of the system side and the phase current of the energy storage side;

[0027] A correction module, used for correcting the energy storage side phase current according to a preset phase offset angle in a state of charging before the energy storage fault, to obtain a corrected energy storage side phase current;

[0028] A protection module is used to obtain a reliability coefficient, formulate a target current differential protection criterion for the access line of the energy storage power station according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, and perform current differential protection using the target current differential protection criterion when it is judged that the energy storage is in a charging state before a fault occurs and the target differential protection criterion is put into use.

[0029] Preferably, the protection module is specifically used for:

[0030] The sum of the system side phase current and the corrected energy storage side phase current is calculated to obtain a corrected differential current; the difference between the system side phase current and the corrected energy storage side phase current is calculated to obtain a corrected braking current; and a target current differential protection criterion for the energy storage power station access line is formulated according to the corrected differential current, the corrected braking current and the reliability coefficient.

[0031] According to a third aspect of the present application, a storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the current differential protection method for the access line of the energy storage power station is implemented.

[0032] According to the fourth aspect of the present application, a computer device is provided, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, wherein when the processor executes the program, the current differential protection method for the access line of the energy storage power station is implemented.

[0033] Through the above technical scheme, the present invention provides a current differential protection method, device and equipment for energy storage power station access lines, firstly obtaining the system side phase current and the energy storage side phase current; then, in the state of charging before the energy storage fault, the energy storage side phase current is corrected according to the preset phase offset angle to obtain the corrected energy storage side phase current; finally, the reliability coefficient is obtained, and the target current differential protection criterion for the energy storage power station access line is formulated according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient. When it is judged that the energy storage is in a charging state before the fault and the target differential protection criterion is put into use, the target current differential protection criterion is used to perform current differential protection. Through the technical scheme of the present invention, for the energy storage power station access line, due to the charging before the energy storage fault, the target current differential protection criterion is used to perform current differential protection. In this state, the angle between the system side phase current and the energy storage side phase current may be an obtuse angle, which falls in the non-action zone. Therefore, the energy storage side phase current is twisted by a preset phase offset angle to obtain the energy storage side phase current after the twisted angle (the energy storage side phase current after this twisted angle is the corrected energy storage side phase current), so that the angle between the energy storage side phase current after the twisted angle and the system side phase current is an acute angle, that is, the energy storage side phase current after the twisted angle falls in the action zone. The target current differential protection criterion formulated by the corrected energy storage side phase current can stably act when a fault occurs, which solves the technical problem that when the energy storage is in the state of charging before the fault and the access line fails, the existing ratio-braked current differential protection criterion has the risk of refusal to act and cannot isolate the fault expansion caused by the fault in the line.

[0034] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the local application. In the drawings:

[0036] Figure 1 A schematic flow chart of a current differential protection method for access lines of an energy storage power station provided by an embodiment of the present invention is shown;

[0037] Figure 2 A schematic flow chart of another current differential protection method for access lines of an energy storage power station provided by an embodiment of the present invention is shown;

[0038] Figure 3 A schematic structural diagram of a current differential protection device for access lines of an energy storage power station provided by an embodiment of the present invention is shown;

[0039] Figure 4 A schematic structural diagram of another current differential protection device for access lines of an energy storage power station provided by an embodiment of the present invention is shown;

[0040] Figure 5 A schematic diagram showing an existing ratio-braked current differential protection action range provided by an embodiment of the present invention;

[0041] Figure 6 A schematic diagram showing short-circuit current characteristics provided by an energy storage provided by an embodiment of the present invention;

[0042] Figure 7 A simulation model topology structure provided by an embodiment of the present invention is shown;

[0043] Figure 8 The waveform diagram of the current amplitude and phase on the P side under a two-phase interphase short circuit fault type provided by an embodiment of the present invention is shown;

[0044] Fig. 9 The figure shows the current amplitude and phase waveform of the Q side under a two-phase interphase short circuit fault type provided by an embodiment of the present invention;

[0045] Fig.10 The differential current and braking current waveforms of the existing ratio-braking current differential protection criterion under a two-phase interphase short-circuit fault type provided by an embodiment of the present invention are shown;

[0046] Fig.11 The modified differential current and modified braking current waveform diagram of the target current differential protection criterion for the access line of the energy storage power station under a two-phase interphase short circuit fault type provided by an embodiment of the present invention are shown;

[0047] Fig.12 The waveform diagram of the current amplitude and phase on the P side under a two-phase inter-phase short circuit fault type provided by an embodiment of the present invention is shown;

[0048] Fig.13 The figure shows the current amplitude and phase waveform of the Q side under a two-phase inter-phase short circuit fault type provided by an embodiment of the present invention;

[0049] Fig.14 The differential current and braking current waveforms of the existing ratio-braking current differential protection criterion under a two-phase inter-phase to ground short circuit fault type provided by an embodiment of the present invention are shown;

[0050] Fig.15The modified differential current and modified braking current waveform diagram of the target current differential protection criterion for the access line of the energy storage power station under a two-phase inter-phase short circuit fault type provided by an embodiment of the present invention are shown;

[0051] Fig.16 The differential current and braking current waveform diagram of the existing ratio-braking current differential protection criterion under a single-phase grounding fault type provided by an embodiment of the present invention and a 10Ω transition resistance are shown;

[0052] Fig.17 The modified differential current and modified braking current waveform diagram of the target current differential protection criterion for the energy storage power station access line under a single-phase grounding fault type provided by an embodiment of the present invention with a transition resistance of 10Ω are shown;

[0053] Fig.18 The differential current and braking current waveforms of the existing ratio-braking current differential protection criterion under a single-phase grounding fault type provided by an embodiment of the present invention and a 100Ω transition resistance are shown;

[0054] Fig.19 The modified differential current and modified braking current waveforms of the target current differential protection criterion for the energy storage power station access line under a single-phase grounding fault type provided by an embodiment of the present invention and a 100Ω transition resistance are shown. DETAILED DESCRIPTION

[0055] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0056] Here is a detailed description of the technical background:

[0057] Relay protection is a safety protection measure used for power systems and equipment. It detects abnormal conditions in the power system and automatically triggers circuit breakers to isolate the faulty part to prevent the fault from expanding and protect the system from running safely and stably.

[0058] Current differential protection is a relay protection technology based on the current balance principle, which is mainly used to detect and isolate faults in power equipment or transmission lines.

[0059] The current balance principle means that under normal operating conditions, the current in the power system is symmetrical, that is, at both ends of the power line, the current flowing in and out is equal in magnitude and opposite in direction. However, when a power line or equipment fails, such as a short circuit or ground fault, additional current will be generated at the fault point, causing the current at both ends of the line to no longer be balanced.

[0060] The current differential protection device is installed at both ends of the power line to measure the current at both ends. It can collect and calculate the unbalanced current on both sides of the line. If the unbalanced current exceeds the preset action value, the protection device will consider that a fault has occurred and send an action signal.

[0061] This embodiment provides a current differential protection method for energy storage power station access lines, such as Figure 1 As shown, the method includes:

[0062] 101. Obtain the phase current on the system side and the phase current on the energy storage side.

[0063] 102. In a state of charging before an energy storage fault occurs, the energy storage side phase current is corrected according to a preset phase offset angle to obtain a corrected energy storage side phase current.

[0064] 103. Obtain a reliability coefficient, formulate a target current differential protection criterion for the access line of the energy storage power station according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, and perform current differential protection using the target current differential protection criterion when the energy storage is in a charging state before the energy storage fault is determined and the target differential protection criterion is put into operation.

[0065] 1. Next, the existing ratio-restrained current differential protection scheme is introduced:

[0066] The protection principle of the existing ratio-restrained current differential protection scheme is based on the existing ratio-restrained current differential protection criterion. The existing ratio-restrained current differential protection criterion formula is:

[0067]

[0068] In the formula, and are the phase currents on both sides (Q side and P side) of line PQ, k set is the reliability coefficient.

[0069] like Figure 5 As shown, the principle of the existing ratio-restrained current differential protection criterion is explained. Figure 5 The phase current on the Q side is Direction is used as the reference, and the differential current is represented in the phasor diagram and braking current The range of the non-operating zone can be derived from the existing ratio-restrained current differential protection judgment formula as follows: As the center of the circle, The intersection of a circle with a radius of 0 and a unit circle. The gray part in the figure is the action area. When a fault occurs in the line PQ area (i.e., the gray part in the figure), and The directions of the currents are basically the same, so the differential current at this time Very large, braking current The protection can be operated stably; the white part is the non-operating area, that is, when there is no fault or an out-of-area fault occurs, and The direction is opposite to that of the braking current. Very large, differential current Very small. Protection does not work.

[0070] 2. For steps 101-103 of the embodiment, since the existing ratio-braked current differential protection criterion has the risk of refusal to operate only when the line connected to the energy storage power station fails when the energy storage is charged before the fault, the goal of steps 101-103 of the embodiment is to improve the existing ratio-braked current differential protection criterion when the energy storage is charged before the fault.

[0071] Next, we first explain (1) that the phase current characteristics provided by the energy storage are different from those of the traditional power supply, and then explain (2) that such differences will lead to the risk of rejection of the existing ratio-restrained current differential protection criterion when the energy storage is charged before the fault. Finally, we explain (3) that in order to solve this rejection risk, when the energy storage is charged before the fault, the energy storage side phase current is corrected according to the preset phase offset angle to obtain the corrected energy storage side phase current:

[0072] (1) The phase current characteristics provided by energy storage are different from those of traditional power sources:

[0073] The phase current characteristics provided by energy storage are analyzed as follows:

[0074] 1) When energy storage is used as a power source, the phase current characteristics are similar to those of other inverter-type power sources, showing the characteristics of limited amplitude and controlled phase. The phase current characteristics provided by energy storage are mainly determined by the converter control strategy. In order to protect power electronic devices such as inverters, the control strategy usually limits the output phase current amplitude after a fault. Therefore, the phase current provided by energy storage has the characteristic of limited amplitude. In addition, the control of the inverter usually takes the positive sequence voltage as the reference, decomposing the current into active and reactive components and controlling them separately, which makes the phase current provided by the energy storage have the characteristic of phase control.

[0075] 2) Compared with other inverter-type power sources, the existing national standards only set requirements for the lower limit of the reactive current support capability of energy storage, which makes the selection of reactive current control targets of energy storage converters during fault ride-through have a large variation space, which is significantly different from photovoltaic power sources. The existing standard stipulates as shown in the following formula:

[0076] I T =0(U T >0.85)

[0077] I T ≥1.6×(0.85-U T )I N (0.2≤U T ≤0.85)

[0078] I T ≥1.04×I N (U T <0.2)

[0079] In the formula, I T is the reactive current injected by the energy storage to the grid connection point, U T is the per unit value of the grid connection point voltage.

[0080] 3) In current engineering practice, the phase current provided by the energy storage is affected by the charge and discharge state before the fault, and its active component remains consistent with the state before the fault. Therefore, when the energy storage encounters a line fault in the charging state, in order to maintain the original charge and discharge state unchanged, the energy storage converter is still controlled according to the absorption of active current.

[0081] (2) Such differences may lead to the risk of refusal to operate in the existing ratio-restrained current differential protection criteria when the energy storage is being charged before a fault occurs:

[0082] like Figure 6 As shown, Figure 6 (a) and (b) are the short-circuit currents provided by the energy storage in the discharge and charging states before the energy storage fault. According to feature 2), the phase current i q (Here I q Represents the phase current on the energy storage side. When discussing the target differential protection criterion below, Indicates that the phase current on the energy storage side has a large variation space (represented by i in the figure) q1 and i q2 ), so the synthetic phase current i a The changes in a1 and i a2 ). In addition, compared Figure 6 (a) and (b) show that feature 3) leads to active current components i in different charge and discharge states before the fault. d The direction is opposite, so its phase current i a The phase difference is obvious. Figure 6 (b) It can be seen that when the existing ratio-restrained current differential protection is applied to the energy storage access line, if the energy storage is in a charging state before the fault, the energy storage side phase current i q1 The positive sequence voltage angle with the grid connection point is Or the energy storage side phase current i provided after a fault q2The positive sequence voltage angle with the grid connection point is Whether it is i q1 with i q2 For any of them, the angle between it and the positive sequence voltage at the grid connection point is obtuse.

[0083] The system side phase current and Figure 6 (a) is the same, and its angle with the positive sequence voltage is usually an acute angle. Since the angle between the phase current on the energy storage side and the positive sequence voltage at its grid connection point is an obtuse angle, and the angle between the phase current on the system side and the positive sequence voltage at the same grid connection point is an acute angle, there is a possibility that the angle between the phase current on the system side and the phase current on the energy storage side is an obtuse angle. If the angle between the phase current on the system side and the phase current on the energy storage side is an obtuse angle, it will be reflected in Figure 5 In the example, the phase current on the energy storage side stays in the white non-operating area. Therefore, if the energy storage is in a charging state before the fault, when a fault occurs in the connected line, the existing ratio-braked current differential protection criterion has the risk of refusal to operate.

[0084] (3) In order to solve the risk of refusal to operate, in the charging state before the energy storage failure, the energy storage side phase current is corrected according to the preset phase offset angle to obtain the corrected energy storage side phase current:

[0085] It should be noted that the idea of ​​correcting the phase current on the energy storage side according to the preset phase offset angle is that the phase current on the energy storage side needs to be corrected because it falls in the non-action zone, and the angle between it and the phase current on the system side is an obtuse angle. Therefore, by twisting the phase current on the energy storage side by an angle, the phase current on the energy storage side after the twisting angle is obtained (the phase current on the energy storage side after the twisting angle is the corrected phase current on the energy storage side), so that the angle between the phase current on the energy storage side after the twisting angle and the phase current on the system side is an acute angle, that is, the phase current on the energy storage side after the twisting angle falls in the action zone, so that it can operate stably when a fault occurs.

[0086] Among them, the phase current of the energy storage side is The preset phase offset angle is represented by 1∠θ (1 and ∠θ are in a multiplication relationship, and 1 is the coefficient of ∠θ). The preset phase offset angle is obtained by analyzing the amplitude and phase of the phase currents on both sides of the line (i.e., the phase current on the energy storage side and the phase current on the system side) under various fault conditions, and the optimal value that can cover various fault types can be obtained. The selection of the preset phase offset angle can keep the phase difference of the phase currents on both sides of the line (i.e., the phase current on the energy storage side and the phase current on the system side) within the acute angle range. is the corrected phase current on the energy storage side.

[0087]

[0088] In summary, the target current differential protection criteria for the energy storage power station access line are formulated as follows:

[0089]

[0090] Among them, the system side phase current is It means that k set is the reliability coefficient, set by the user, and should satisfy k set ∈[0.5,1].

[0091] The present invention provides a current differential protection method, device and equipment for energy storage power station access lines. First, the system side phase current and the energy storage side phase current are obtained; then, in the state of charging before the energy storage fault, the energy storage side phase current is corrected according to a preset phase offset angle to obtain the corrected energy storage side phase current; finally, the reliability coefficient is obtained, and a target current differential protection criterion for the energy storage power station access line is formulated according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient. When it is judged that the energy storage is in a charging state before the fault and the target differential protection criterion is put into use, the target current differential protection criterion is used to perform current differential protection. Through the technical solution of the present invention, for the energy storage power station access line, since the system is in a charging state before the energy storage fault, The angle between the system-side phase current and the energy storage-side phase current may be an obtuse angle, which falls in the non-action zone. Therefore, the energy storage-side phase current is twisted by a preset phase offset angle to obtain the energy storage-side phase current after the twisted angle (the energy storage-side phase current after the twisted angle is the corrected energy storage-side phase current), so that the angle between the energy storage-side phase current after the twisted angle and the system-side phase current is an acute angle, that is, the energy storage-side phase current after the twisted angle falls in the action zone. The target current differential protection criterion formulated by the corrected energy storage-side phase current can stably act when a fault occurs, which solves the technical problem that when the energy storage is in a charging state before the fault and the connected line fails, the existing ratio-braked current differential protection criterion has the risk of refusal to act and cannot isolate the fault expansion caused by the fault in the line.

[0092] Further, as a refinement and expansion of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, another current differential protection method for the access line of the energy storage power station is provided, such as Figure 2 As shown, the method includes:

[0093] 201. Obtain the phase current on the system side and the phase current on the energy storage side.

[0094] 202. In a state of charging before an energy storage fault occurs, calculate the product of the preset phase offset angle and the energy storage side phase current to obtain a corrected energy storage side phase current.

[0095] 203. Obtain a reliability coefficient, calculate the sum of the system side phase current and the corrected energy storage side phase current to obtain a corrected differential current, calculate the difference between the system side phase current and the corrected energy storage side phase current to obtain a corrected braking current.

[0096] 204. Formulate a target current differential protection criterion for the energy storage power station access line according to the corrected differential current, the corrected braking current and the reliability coefficient.

[0097] For this embodiment, the target current differential protection criterion for the energy storage power station access line is formulated according to the corrected differential current, the corrected braking current and the reliability coefficient, including: determining the first absolute value of the corrected differential current, determining the second absolute value of the corrected braking current; and taking the first absolute value greater than the product of the reliability coefficient and the second absolute value as the target current differential protection criterion for the energy storage power station access line.

[0098] For the steps 201-204 of the embodiment, the specific implementation is the same as the steps 101-103 of the embodiment, and will not be repeated here. Among them, the corrected differential current is The corrected braking current is The first absolute value of the corrected differential current is The second absolute value of the corrected braking current is

[0099] 205. Set a target current differential protection criterion input pressure plate. When the protected line is a grid-connected energy storage power station access line, the target current differential protection criterion input pressure plate is set to 1 to indicate that the target differential protection criterion is put into operation. When the protected line is not a grid-connected energy storage power station access line, the target current differential protection criterion input pressure plate is set to 0 to indicate that the target differential protection criterion is not put into operation.

[0100] 206. Set a charging and discharging state monitoring element before energy storage failure, obtain the current phase and the voltage phase of the energy storage side, calculate the third absolute value of the difference between the current phase and the voltage phase of the energy storage side, and determine whether the third absolute value is greater than 90 degrees. If so, it is determined that the energy storage is in a charging state before the failure.

[0101] For steps 205 and 206 of the embodiment, the target current differential protection criterion for the energy storage power station access line is applied in the protection device. Specifically, the target current differential protection criterion for the energy storage power station access line is applied with a target ratio braking phase current differential element (this element is based on the target current differential protection criterion), a target current differential protection criterion input pressure plate, an energy storage before fault charge and discharge state monitoring element and other phase current differential elements (other phase current differential elements are the same as those in the existing protection device and are not repeated here). In the protection device, the target ratio braking phase current differential element, the target current differential protection criterion input pressure plate and the energy storage before fault charge and discharge state monitoring element are connected to the same AND gate, and the target ratio braking phase current differential element, the target current differential protection criterion input pressure plate, the energy storage before fault charge and discharge state monitoring element and the above-mentioned AND gate and other phase current differential elements are connected in parallel and then connected to the same OR gate.

[0102] For step 205 of the embodiment, the target current differential protection criterion input pressure plate is used to control whether the target differential protection criterion is effective. The user can choose whether to input the target differential protection criterion according to the protection object of the protection device.

[0103] For step 206 of the embodiment, the energy storage device charge-discharge state monitoring element before the failure is used to determine and record whether the energy storage device is in a charging state before the failure. When it is determined that the energy storage device is in a charging state before the failure, the energy storage device charge-discharge state monitoring element before the failure is set to 1. When the energy storage device is not in a charging state before the failure, the energy storage device charge-discharge state monitoring element before the failure is set to 0.

[0104]

[0105] in, is the current phase of the energy storage side, It is the voltage phase on the energy storage side. When any action element in the protection device (any action element includes the target ratio braking type phase current differential element, the target current differential protection criterion input pressure plate, the energy storage pre-fault charging and discharging status monitoring element and any other phase current differential element) is actuated, it is considered that a fault has occurred at this time, and this element stops updating its own value and keeps the status value at the previous moment unchanged.

[0106] 207. When it is determined that the energy storage is in a charging state before a fault occurs and the target differential protection criterion is activated, current differential protection is performed using the target current differential protection criterion.

[0107] In summary, the effect of the target ratio braking split-phase current differential element is verified by the following simulation example. The topology of the simulation model is as follows: Figure 7 As shown, the impedance parameters of line PQ are shown in the following table:

[0108] Line positive sequence impedance (Ω / km) 0.13+j0.84 Line zero-sequence impedance (Ω / km) 0.36+j2.5

[0109] The limit value of the energy storage converter is set to 1.5 times the rated current, and the control target of the reactive support current is set according to the following formula:

[0110] I q_ref ≥1.1×I N (U T ≤0.85)

[0111] I q_ref =0(U T >0.85)

[0112] In the simulation, the energy storage is set to charge at rated power before the fault. A fault occurs near P at 1.5s. The analysis of different fault types is as follows:

[0113] 1) Two-phase short circuit

[0114] In the simulation, the fault type is set to phase-to-phase short circuit between phases AB, and the transition resistance is 10 ohms. The current amplitude and phase on the P side are as follows: Figure 8 As shown in (where the unmarked waveform is Ipa_mag), the current amplitude and phase on the Q side are as follows Fig. 9 shown.

[0115] The differential current and braking current of the existing ratio-restrained current differential protection criteria are as follows: Fig.10 As shown in FIG. 1 , the corrected differential current and the corrected braking current of the target current differential protection criterion of the energy storage power station access line are as follows: Fig.11 shown.

[0116] from Fig.10 It can be seen that when the existing ratio-restrained current differential protection criterion is used, the differential current of the fault phase A is less than the braking current, and there is a risk of refusal to operate. Fig.11 It can be seen that the corrected differential current of the fault phase A using the target current differential protection criterion exceeds twice the corrected braking current, and the current differential protection can operate reliably. In addition, the corrected braking current of the non-fault phase is always much larger than the corrected differential current, and the use of the target current differential protection criterion will not cause false operation of the non-fault phase.

[0117] 2) Two phases are short-circuited to ground

[0118] In the simulation, the fault type is set to phase-to-phase short circuit between phases AB, the phase-to-phase transition resistance is 0Ω, and the ground transition resistance is 100Ω. The current amplitude and phase on the P side are as follows: Fig.12 As shown, the current amplitude and phase on the Q side are as follows Fig.13 The differential current and braking current of the existing ratio-restrained current differential protection criterion are as follows: Fig.14As shown in FIG. 1 , the corrected differential current and the corrected braking current of the target current differential protection criterion of the energy storage power station access line are as follows: Fig.15 shown.

[0119] contrast Fig.14 and 15 It can be seen that when the existing ratio-restrained current differential protection criterion is used, the differential current of the fault phases A and B is much smaller than the braking current. When the target current differential protection criterion is used, the corrected differential current of the fault phase A exceeds the corrected braking current. The use of the target current differential protection criterion effectively reduces the risk of current differential protection refusal.

[0120] 3) Single-phase ground fault

[0121] In the simulation, the fault type is set to A-phase ground fault, and the transition resistance is set to 10Ω and 100Ω respectively. The differential current and the braking current of the existing ratio-restrained current differential protection criterion under the condition of 10Ω transition resistance are as follows: Fig.16 As shown in FIG. 1 , the corrected differential current and the corrected braking current of the target current differential protection criterion for the energy storage power station access line under the condition of 10Ω transition resistance are as follows: Fig.17 As shown in the figure, the differential current and the braking current of the existing ratio-restrained current differential protection criterion under the condition of 100Ω transition resistance are as follows Fig.18 As shown in FIG. 1 , the corrected differential current and the corrected braking current of the target current differential protection criterion for the energy storage power station access line under the condition of 100Ω transition resistance are as follows: Fig.19 shown.

[0122] First, by comparing Fig.16 and Fig.18 It can be found that as the transition resistance increases, the differential current decreases and the braking current increases. This significantly increases the risk of rejection of the current differential protection. Fig.17 and Fig.19 It can be found that by using the target current differential protection criterion, it is still possible to ensure that the corrected differential current of the fault phase is greater than the corrected braking current, thus avoiding protection failure.

[0123] In addition, Fig.16 In the example, although the differential current of phase A is greater than the braking current, the magnitudes of the two are very close, which may lead to insufficient sensitivity. Fig.17 The corrected differential current shown is significantly larger than the corrected braking current, and the sensitivity of the protection is improved.

[0124] The present invention provides a current differential protection method, device and equipment for energy storage power station access lines. First, the system side phase current and the energy storage side phase current are obtained; then, in the state of charging before the energy storage fault, the energy storage side phase current is corrected according to a preset phase offset angle to obtain the corrected energy storage side phase current; finally, the reliability coefficient is obtained, and a target current differential protection criterion for the energy storage power station access line is formulated according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient. When it is judged that the energy storage is in a charging state before the fault and the target differential protection criterion is put into use, the target current differential protection criterion is used to perform current differential protection. Through the technical solution of the present invention, for the energy storage power station access line, since the system is in a charging state before the energy storage fault, The angle between the system-side phase current and the energy storage-side phase current may be an obtuse angle, which falls in the non-action zone. Therefore, the energy storage-side phase current is twisted by a preset phase offset angle to obtain the energy storage-side phase current after the twisted angle (the energy storage-side phase current after the twisted angle is the corrected energy storage-side phase current), so that the angle between the energy storage-side phase current after the twisted angle and the system-side phase current is an acute angle, that is, the energy storage-side phase current after the twisted angle falls in the action zone. The target current differential protection criterion formulated by the corrected energy storage-side phase current can stably act when a fault occurs, which solves the technical problem that when the energy storage is in a charging state before the fault and the connected line fails, the existing ratio-braked current differential protection criterion has the risk of refusal to act and cannot isolate the fault expansion caused by the fault in the line.

[0125] Further, as Figure 1 and Figure 2 The specific implementation of the method shown in the figure, the embodiment of the present invention provides a current differential protection device for the access line of the energy storage power station, such as Figure 3 As shown, the device includes: an acquisition module 31, a correction module 32, and a protection module 33;

[0126] An acquisition module 31 is used to acquire the phase current of the system side and the phase current of the energy storage side;

[0127] A correction module 32, used for correcting the energy storage side phase current according to a preset phase offset angle in a state of charging before the energy storage fault, to obtain a corrected energy storage side phase current;

[0128] The protection module 33 is used to obtain the reliability coefficient, formulate a target current differential protection criterion for the access line of the energy storage power station according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, and perform current differential protection using the target current differential protection criterion when it is judged that the energy storage is in a charging state before a fault occurs and the target differential protection criterion is put into use.

[0129] Correspondingly, in order to correct the energy storage side phase current according to the preset phase offset angle to obtain the corrected energy storage side phase current, the correction module 32 can be specifically used to calculate the product of the preset phase offset angle and the energy storage side phase current to obtain the corrected energy storage side phase current.

[0130] Correspondingly, in order to formulate a target current differential protection criterion for the energy storage power station access line according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, the protection module 33 can be specifically used to calculate the sum of the system side phase current and the corrected energy storage side phase current to obtain a corrected differential current; calculate the difference between the system side phase current and the corrected energy storage side phase current to obtain a corrected braking current; formulate a target current differential protection criterion for the energy storage power station access line according to the corrected differential current, the corrected braking current and the reliability coefficient.

[0131] Correspondingly, in order to formulate a target current differential protection criterion for the energy storage power station access line based on the corrected differential current, the corrected braking current and the reliability coefficient, the protection module 33 can also be used to determine the first absolute value of the corrected differential current and the second absolute value of the corrected braking current; the first absolute value is greater than the product of the reliability coefficient and the second absolute value, which is used as the target current differential protection criterion for the energy storage power station access line.

[0132] In a specific application state, such as Figure 4 As shown, a current differential protection device for a power storage station access line, the device also includes: a first setting module 34, which can be specifically used to set a target current differential protection criterion input pressure plate; when the protected line is a grid-connected energy storage station access line, the target current differential protection criterion input pressure plate is set to 1 to indicate that the target differential protection criterion is put into use; when the protected line is not a grid-connected energy storage station access line, the target current differential protection criterion input pressure plate is set to 0 to indicate that the target differential protection criterion is not put into use.

[0133] In a specific application state, such as Figure 4 As shown, a current differential protection device for a line accessed to an energy storage power station, the device also includes: a second setting module 35, which can be specifically used to set a charging and discharging state monitoring element before an energy storage fault; obtaining a current phase and a voltage phase on the energy storage side, calculating a third absolute value of a phase difference between the current phase on the energy storage side and the voltage phase on the energy storage side, and judging whether the third absolute value is greater than 90 degrees. If so, it is determined that the energy storage is in a charging state before the fault.

[0134] It should be noted that for other corresponding descriptions of the functional units involved in the current differential protection device for the access line of the energy storage power station provided in this embodiment, reference can be made to Figure 1 to Figure 2 The corresponding description will not be repeated here.

[0135] Based on the above Figure 1 to Figure 2 The method shown in the embodiment, accordingly, also provides a storage medium, which can be volatile or non-volatile, and stores a computer program, which is executed by a processor to implement the above-mentioned Figure 1 to Figure 2 The current differential protection method for the access line of the energy storage power station is shown.

[0136] Based on this understanding, the technical solution of the present invention can be embodied in the form of a software product, which can be stored in a storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods of various implementation states of the present invention.

[0137] Based on the above Figure 1 to Figure 2 The method shown and Figure 3 , Figure 4 In order to achieve the above-mentioned purpose, the present embodiment further provides a computer device, which includes a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to achieve the above-mentioned Figure 1 to Figure 2 The current differential protection method for the access line of the energy storage power station is shown.

[0138] Optionally, the computer device may further include a user interface, a network interface, a camera, a radio frequency (RF) circuit, a sensor, an audio circuit, a WI-FI module, etc. The user interface may include a display, an input unit such as a keyboard, etc., and the optional user interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a WI-FI interface), etc.

[0139] Those skilled in the art will appreciate that the computer device structure provided in this embodiment does not constitute a limitation on the physical device, and may include more or fewer components, or a combination of certain components, or different component arrangements.

[0140] The storage medium may also include an operating network communication module. The operating is a program that manages the hardware and software resources of the above-mentioned computer device, supporting the operation of the information processing program and other software and / or programs. The network communication module is used to communicate between the components inside the storage medium, and to communicate with other hardware and software in the information processing entity device.

[0141] Through the description of the above implementation modes, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform, or by hardware.

[0142] The present invention provides a current differential protection method, device and equipment for energy storage power station access lines. First, the system side phase current and the energy storage side phase current are obtained; then, in the state of charging before the energy storage fault, the energy storage side phase current is corrected according to a preset phase offset angle to obtain the corrected energy storage side phase current; finally, the reliability coefficient is obtained, and a target current differential protection criterion for the energy storage power station access line is formulated according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient. When it is judged that the energy storage is in a charging state before the fault and the target differential protection criterion is put into use, the target current differential protection criterion is used to perform current differential protection. Through the technical solution of the present invention, for the energy storage power station access line, since the system is in a charging state before the energy storage fault, The angle between the system-side phase current and the energy storage-side phase current may be an obtuse angle, which falls in the non-action zone. Therefore, the energy storage-side phase current is twisted by a preset phase offset angle to obtain the energy storage-side phase current after the twisted angle (the energy storage-side phase current after the twisted angle is the corrected energy storage-side phase current), so that the angle between the energy storage-side phase current after the twisted angle and the system-side phase current is an acute angle, that is, the energy storage-side phase current after the twisted angle falls in the action zone. The target current differential protection criterion formulated by the corrected energy storage-side phase current can stably act when a fault occurs, which solves the technical problem that when the energy storage is in a charging state before the fault and the connected line fails, the existing ratio-braked current differential protection criterion has the risk of refusal to act and cannot isolate the fault expansion caused by the fault in the line.

[0143] Those skilled in the art will appreciate that the accompanying drawings are only schematic diagrams of a preferred implementation state, and the modules or processes in the accompanying drawings are not necessarily necessary for implementing the present invention. Those skilled in the art will appreciate that the modules in the devices in the implementation state can be distributed in the devices in the implementation state according to the description of the implementation state, or can be changed accordingly and located in one or more devices different from the present implementation state. The modules in the above-mentioned implementation state can be combined into one module, or can be further split into multiple submodules.

[0144] The serial numbers of the present invention are only for description and do not represent the advantages and disadvantages of the implementation status. The above disclosure is only a few specific implementation statuses of the present invention, but the present invention is not limited thereto, and any changes that can be thought of by a person skilled in the art should fall within the protection scope of the present invention.

Claims

1. A current differential protection method for access lines of energy storage power stations, characterized in that: The method comprises: Obtaining the phase current on the system side and the phase current on the energy storage side; In the state of charging before the energy storage fault, the energy storage side phase current is corrected according to a preset phase offset angle to obtain a corrected energy storage side phase current; Obtain a reliability coefficient, formulate a target current differential protection criterion for the access line of the energy storage power station according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, and perform current differential protection using the target current differential protection criterion when it is determined that the energy storage is in a charging state before a fault occurs and the target current differential protection criterion is activated.

2. The method according to claim 1, characterized in that The step of correcting the energy storage side phase current according to the preset phase offset angle to obtain the corrected energy storage side phase current includes: The product of the preset phase offset angle and the energy storage side phase current is calculated to obtain a corrected energy storage side phase current.

3. The method according to claim 1 or 2, characterized in that: The step of formulating a target current differential protection criterion for the energy storage power station access line according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient includes: Calculating the sum of the system side phase current and the corrected energy storage side phase current to obtain a corrected differential current; Calculating the difference between the system side phase current and the corrected energy storage side phase current to obtain a corrected braking current; A target current differential protection criterion for the energy storage power station access line is formulated according to the corrected differential current, the corrected braking current and the reliability coefficient.

4. The method according to claim 3, characterized in that The step of formulating a target current differential protection criterion for the energy storage power station access line according to the corrected differential current, the corrected braking current and the reliability coefficient includes: determining a first absolute value of the modified differential current, and determining a second absolute value of the modified braking current; The first absolute value being greater than the product of the reliability coefficient and the second absolute value is used as a target current differential protection criterion for the energy storage power station access line.

5. The method according to claim 1, characterized in that When the energy storage device is in a charging state before determining that the energy storage device has a fault and the target current differential protection criterion is activated, before performing current differential protection using the target current differential protection criterion, the method further includes: Set the target current differential protection criterion and put it into the pressure plate; When the protected line is a grid-connected energy storage power station access line, the target current differential protection criterion input pressure plate is set to 1 to indicate that the target current differential protection criterion is input; When the protected line is not a grid-connected energy storage power station access line, the target current differential protection criterion input pressure plate is set to 0 to indicate that the target current differential protection criterion is not input.

6. The method according to claim 1, characterized in that When the energy storage device is in a charging state before determining that the energy storage device has a fault and the target current differential protection criterion is activated, before performing current differential protection using the target current differential protection criterion, the method further includes: Set up a monitoring element for the charge and discharge status of energy storage before failure; Obtain the energy storage side current phase and the energy storage side voltage phase, calculate the third absolute value of the energy storage side current phase and the energy storage side voltage phase difference, and determine whether the third absolute value is greater than 90 degrees. If so, it is determined that the energy storage is in a charging state before the failure.

7. A current differential protection device for access lines of energy storage power stations, characterized in that: The device comprises: An acquisition module, used to acquire the phase current of the system side and the phase current of the energy storage side; A correction module, used for correcting the energy storage side phase current according to a preset phase offset angle in a state of charging before the energy storage fault, to obtain a corrected energy storage side phase current; A protection module is used to obtain a reliability coefficient, formulate a target current differential protection criterion for the access line of the energy storage power station according to the system side phase current, the corrected energy storage side phase current and the reliability coefficient, and perform current differential protection using the target current differential protection criterion when it is judged that the energy storage is in a charging state before a fault occurs and the target current differential protection criterion is put into use.

8. The device according to claim 7, characterized in that The protection module is specifically used for: The sum of the system side phase current and the corrected energy storage side phase current is calculated to obtain a corrected differential current; the difference between the system side phase current and the corrected energy storage side phase current is calculated to obtain a corrected braking current; and a target current differential protection criterion for the energy storage power station access line is formulated according to the corrected differential current, the corrected braking current and the reliability coefficient.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the current differential protection method for the access line of the energy storage power station as described in any one of claims 1 to 6 is implemented.

10. A computer device comprising a storage medium, a processor, and a computer program stored in the storage medium and executable on the processor, characterized in that: When the processor executes the computer program, the current differential protection method for the access line of the energy storage power station as described in any one of claims 1 to 6 is implemented.

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