Intelligent current protection method and device for active power distribution network

Abstract

The invention provides an intelligent current protection method and device for an active power distribution network. The method comprises the following steps: determining an output current phasor according to the rated power, rated line voltage and grid-connected point voltage phasor of distributed photovoltaic in the active power distribution network; setting the phase difference between the fault phase-to-phase voltage and the fault phase-to-phase current according to the fault occurrence position and the fault phase in the active power distribution network; determining a direction element action area according to the obtained traditional maximum sensitive angle and the phase difference between the fault interphase voltage and the fault interphase current; determining whether or not a phase difference measurement value acquired from the directional element belongs to a directional element operation region; and if yes, calculating each phase of current according to the fault occurrence position and the output current phasor, and calculating the ratio of the current corresponding to the phase with the minimum current value to the preset sensitivity to obtain a current quick-break protection setting value. According to the invention, fault characteristic analysis can be carried out on the power distribution network connected with the distributed photovoltaic system, the influence of the fault characteristic on the fault phase current is quantitatively analyzed, and intelligent current protection of the active power distribution network is realized.

Description

Technical Field

[0001] The present application relates to the field of power system maintenance, and specifically to an active distribution network intelligent current protection method and device. Background Art

[0002] At present, the access of inverter-type distributed power sources represented by photovoltaics to the distribution network, while improving power supply reliability, reducing network losses and reducing voltage drops, will also have an adverse impact on the original relay protection configuration scheme, setting of action settings, and coordination of protection actions of the power grid.

[0003] The access of distributed photovoltaics has changed the radial structure of the traditional distribution network, making the direction of the short-circuit current no longer unique after a fault occurs, resulting in the failure of the traditional distribution network protection strategy, and the protection may malfunction or refuse to operate. Adding directional elements to the original protection is an effective way to solve the above problems. Traditional power directional elements use 0° wiring or 90° wiring. When the protection is in the positive direction, the angle between the corresponding voltage and current taken at the protection installation is within the range of ±90° of the respective maximum sensitivity angles, thereby determining the fault direction. However, when distributed photovoltaics adopt different control strategies, the nature of their output current is also different, which will make the maximum sensitivity angle of the power directional element no longer equal to the line impedance angle, resulting in a decrease in the sensitivity of the directional element action; in addition, distributed photovoltaics only output three-phase symmetrical positive sequence current when symmetrical and asymmetrical faults occur in the line, which also affects the angular relationship between the voltage and current at the protection installation under asymmetrical faults. Traditional power directional elements are no longer suitable for distributed photovoltaic distribution networks with different control strategies. Their erroneous operation will affect the correctness of protection actions related to fault direction determination. Therefore, it is necessary to study new methods of directional elements suitable for active distribution networks.

[0004] In addition, most traditional medium and low voltage distribution networks are radial networks that supply power to loads in a single direction. Their protection does not take into account the situation of distributed photovoltaic access in the network, and is usually configured as a three-stage current protection. When distributed photovoltaics are connected to the distribution network, the distribution network becomes a network with two-terminal or multi-terminal power supplies. The access of distributed photovoltaics changes the fault current distribution of the distribution network and the basic conditions of the original protection configuration. The impact on the short-circuit current of the distribution network is manifested as auxiliary current, external current and reverse current. The original three-stage current protection of the distribution network may malfunction or refuse to operate. In addition, the output of distributed photovoltaics fluctuates greatly with changes in natural conditions, and the operation mode of the system is also more variable, which makes it difficult to set the set value of traditional current protection and the coordination between protections. Therefore, it is necessary to study new current protection methods suitable for active distribution networks.

[0005] When studying the applicability of power directional elements, most current studies only qualitatively analyze the impact of distributed photovoltaics on directional elements, and lack quantitative theoretical analysis that considers distributed photovoltaic control strategies. The traditional adaptive protection method is applicable to power supply areas where each line is equipped with a protection. By calculating the equivalent potential and equivalent impedance on the back side of the protection, the protection action setting is set according to the actual line impedance. The equipment installation cost is high, and the protection setting needs to be set in real time, which is prone to false operation when distributed photovoltaics are connected.

[0006] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that the description herein is prior art by inclusion in this section. Summary of the invention

[0007] In response to the problems in the prior art, the present application provides an active distribution network intelligent current protection method and device, which can analyze the fault characteristics of the distribution network connected to distributed photovoltaics, and quantitatively analyze the impact of the fault phase current on the distributed photovoltaic control strategy under the premise of considering the distributed photovoltaic control strategy, so as to realize the active distribution network intelligent current protection.

[0008] In order to solve the above technical problems, this application provides the following technical solutions:

[0009] In a first aspect, the present application provides an active distribution network intelligent current protection method, comprising:

[0010] Determine the output current phasor of distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor;

[0011] The phase difference between the fault phase voltage and the fault phase current is set according to the fault location and the fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, the phase difference between the fault phase voltage and the fault phase current is set according to the output current phasor;

[0012] Determine the directional element action area according to the acquired traditional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action area is the phase difference angle range;

[0013] When it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault occurrence location and the output current phasor;

[0014] The current phasor with the smallest modulus value among the current phasors of each phase is selected, the ratio of its modulus value to the preset sensitivity is calculated, and the current quick-break protection setting value is obtained to realize intelligent current protection for the active distribution network.

[0015] Furthermore, the output current phasor of the distributed photovoltaic system in the active power distribution network is determined according to the rated power, rated line voltage and grid connection point voltage phasor, including:

[0016] Calculating the ratio of the rated line voltage to the modulus value of the grid connection point voltage phasor;

[0017] Determining a phasor calculation model according to a threshold range to which the ratio of the modulus values ​​belongs;

[0018] The output current phasor is calculated using the phasor calculation model.

[0019] Furthermore, the output current phasor of the distributed photovoltaic system in the active power distribution network is determined according to the rated power, rated line voltage and grid connection point voltage phasor, including:

[0020] When the distributed photovoltaic system does not have a low voltage ride-through control function, the output current phasor is:

[0021]

[0022] When the distributed photovoltaic system has a low voltage ride-through control function, the output current phasor is:

[0023]

[0024] in, is the output current phasor, P N is the rated power, U N is the rated line voltage, is the grid connection point voltage phasor, and U is the modulus of the grid connection point voltage phasor.

[0025] Furthermore, the step of setting the phase difference between the fault phase voltage and the fault phase current according to the fault location and the fault phase in the active power distribution network includes:

[0026] When a three-phase short circuit fault occurs upstream of the distributed photovoltaic system, the line impedance angle is determined as the phase difference;

[0027] When a two-phase short circuit fault occurs in the upstream of the distributed photovoltaic system, the phase difference is determined according to the ratio of the fault phase voltage to the phase current;

[0028] When a three-phase short circuit fault or a two-phase short circuit fault occurs in the downstream of the distributed photovoltaic system, the phase difference is calculated according to the output current phasor.

[0029] Furthermore, the determining of the directional element action area according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current includes:

[0030] Calculating the maximum positive and negative offset phase angles according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point;

[0031] Determine the sum of half of the positive and negative maximum offset phase angles and the phase difference as the updated maximum sensitivity angle;

[0032] Determine the sum of the updated maximum sensitivity angle and 90° as the first limit angle of the directional element action area;

[0033] Determine the difference between the updated maximum sensitivity angle and 90° as the second limit angle of the directional element action area;

[0034] An angle range between the first limit angle and the second limit angle is determined as the directional element action area.

[0035] Furthermore, the positive and negative maximum offset phase angles include a positive maximum offset angle and a negative maximum offset angle; the positive and negative maximum offset phase angles are calculated according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point, including:

[0036] When the modulus of the grid-connected point voltage phasor is reduced to 0.9 times of itself, the distributed photovoltaic output has the maximum active current, so that the traditional maximum sensitivity angle increases, and a positive maximum offset angle is obtained;

[0037] When the modulus of the grid-connected point voltage phasor is reduced to 0.3 times of itself, the distributed photovoltaic output has the maximum reactive current, so that the traditional maximum sensitivity angle is reduced, and a negative maximum offset angle is obtained.

[0038] Further, when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault location and the output current phasor, including:

[0039] When it is determined that the phase difference measurement value belongs to the directional element action area, the sum of the system equivalent impedance and the fault line impedance is calculated according to the fault occurrence position to obtain the total impedance;

[0040] The current of each phase is calculated according to the ratio of the system equivalent potential to the total impedance and the output current phasor.

[0041] Further, when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault location and the output current phasor, including:

[0042] When a BC two-phase short circuit fault occurs in the distributed photovoltaic upstream line, the current of each phase is:

[0043]

[0044] When a BC two-phase short circuit fault occurs in the distributed photovoltaic downstream line, the current of each phase is:

[0045]

[0046] in, They are the A phase current phasor, the B phase current phasor, and the C phase current phasor, is the output current phasor, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z BC is the impedance of line BC, Z Bf is the line impedance from bus B to the fault, Z Cf is the line impedance from bus C to the fault.

[0047] Furthermore, the current phasor with the smallest modulus value among the current phasors of each phase is selected, the ratio of its modulus value to a preset sensitivity is calculated, and a current quick-break protection setting value is obtained to realize intelligent current protection of the active distribution network, including:

[0048] Compare the modulus values ​​corresponding to the current phasors of each phase and determine the smallest one;

[0049] The ratio of the minimum value to the preset sensitivity is determined as the current quick-break protection setting value;

[0050] When it is detected that the short-circuit current reaches the current quick-break protection setting value, the circuit breaker is controlled to operate and isolate the fault circuit.

[0051] In a second aspect, the present application provides an active distribution network intelligent current protection device, comprising:

[0052] An output current determination unit, used to determine the output current phasor of the distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor;

[0053] A phase difference calculation unit, used for adjusting the phase difference between the fault phase voltage and the fault phase current according to the fault location and the fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, the phase difference between the fault phase voltage and the fault phase current is adjusted according to the output current phasor;

[0054] An action region determination unit, configured to determine a directional element action region according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action region is a phase difference angle range;

[0055] a current determination unit for each phase, configured to calculate the current phasor of each phase according to the fault occurrence location and the output current phasor when it is determined that the phase difference measurement value obtained from the directional element belongs to the action area of ​​the directional element;

[0056] The protection execution unit is used to select the current phasor with the smallest modulus value among the current phasors of each phase, calculate the ratio of its modulus value to a preset sensitivity, obtain a current quick-break protection setting value, and realize intelligent current protection for the active distribution network.

[0057] Furthermore, the output current determining unit includes:

[0058] A module value ratio calculation module, used to calculate the ratio of the module value of the rated line voltage to the grid connection point voltage phasor;

[0059] A calculation model selection module, used for determining a phasor calculation model according to a threshold range to which the ratio of the module values ​​belongs;

[0060] The output current calculation module is used to calculate the output current phasor using the phasor calculation model.

[0061] Furthermore, the output current determining unit includes:

[0062] The first output current calculation module is used for when the distributed photovoltaic does not have a low voltage ride-through control function, the output current phasor is:

[0063]

[0064] The second output current calculation module is used when the distributed photovoltaic has a low voltage ride-through control function, and the output current phasor is:

[0065]

[0066] in, is the output current phasor, P N is the rated power, U N is the rated line voltage, is the grid connection point voltage phasor, and U is the modulus of the grid connection point voltage phasor.

[0067] Furthermore, the phase difference calculation unit comprises:

[0068] A first phase difference calculation module is used to determine the line impedance angle as the phase difference when a three-phase short circuit fault occurs upstream of the distributed photovoltaic system;

[0069] A second phase difference calculation module is used to determine the phase difference according to the ratio of the fault phase voltage to the phase current when a two-phase short circuit fault occurs in the upstream of the distributed photovoltaic system;

[0070] The third phase difference calculation module is used to calculate the phase difference according to the output current phasor when a three-phase short circuit fault or a two-phase short circuit fault occurs in the downstream of the distributed photovoltaic.

[0071] Furthermore, the action area determination unit includes:

[0072] A maximum offset calculation module, used to calculate the positive and negative maximum offset phase angles according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point;

[0073] A maximum sensitivity update module, used to determine the sum of half of the positive and negative maximum offset phase angles and the phase difference as an updated maximum sensitivity angle;

[0074] A first margin determination module, used for determining the sum of the updated maximum sensitivity angle and 90° as the first margin angle of the directional element action area;

[0075] A second margin determination module, used for determining the difference between the updated maximum sensitivity angle and 90° as a second margin angle of the directional element action area;

[0076] The action area determination module is used to determine the angle range between the first limit angle and the second limit angle as the directional element action area.

[0077] Furthermore, the positive and negative maximum offset phase angles include a positive maximum offset angle and a negative maximum offset angle; and the maximum offset calculation module includes:

[0078] A positive offset calculation module is used for, when the modulus of the grid-connected point voltage phasor is reduced to 0.9 times of itself, the distributed photovoltaic output has the maximum active current, so that the traditional maximum sensitivity angle is increased, and the maximum offset angle of the positive value is obtained;

[0079] The negative offset calculation module is used to output the maximum reactive current of the distributed photovoltaic when the modulus of the grid-connected point voltage phasor is reduced to 0.3 times of itself, so that the traditional maximum sensitivity angle is reduced to obtain the maximum offset angle of negative value.

[0080] Furthermore, the phase current determination unit includes:

[0081] An impedance sum calculation module, used for calculating the sum of the system equivalent impedance and the fault line impedance according to the fault occurrence position to obtain the total impedance when it is determined that the phase difference measurement value belongs to the directional element action area;

[0082] The current calculation module for each phase is used to calculate the current for each phase according to the ratio of the system equivalent potential to the total impedance and the output current phasor.

[0083] Furthermore, the phase current determination unit includes:

[0084] The first phase current determination module is used for determining the current of each phase when a BC two-phase short circuit fault occurs in the distributed photovoltaic upstream line:

[0085]

[0086] The second phase current determination module is used for when a BC two-phase short circuit fault occurs in the distributed photovoltaic downstream line, and the current of each phase is:

[0087]

[0088] in, They are the A phase current phasor, the B phase current phasor, and the C phase current phasor, is the output current phasor, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z BC is the impedance of line BC, Z Bf is the line impedance from bus B to the fault, Z Cf is the line impedance from bus C to the fault.

[0089] Furthermore, the protection execution unit includes:

[0090] A minimum determination module is used to compare the module values ​​corresponding to the current phasors of each phase and determine the smallest one among them;

[0091] A ratio setting module, used for determining the ratio of the minimum value to a preset sensitivity as the current quick-break protection setting value;

[0092] The isolation action module is used to control the circuit breaker to operate and isolate the fault circuit when it is detected that the short-circuit current reaches the current quick-break protection setting value.

[0093] In a third aspect, the present application provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the active distribution network intelligent current protection method when executing the program.

[0094] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the active distribution network intelligent current protection method.

[0095] In a fifth aspect, the present application provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the active distribution network intelligent current protection method.

[0096] In view of the problems in the prior art, the active distribution network intelligent current protection method and device provided by the present application can analyze the fault characteristics of the distributed photovoltaic distribution network, and can protect the active distribution network by only using the relationship between the fault phase voltage and the fault phase current phase difference, without adding additional communication costs and equipment installation costs, and is easy to implement in engineering; it fully considers the influence of factors such as the control strategy, rated capacity, fault type, and fault location of distributed photovoltaic on the protection of the active distribution network, and has good applicability under various fault conditions; it also proposes a setting method for the maximum sensitivity angle, which can make the power direction element have high action sensitivity under all possible conditions; it considers the distributed photovoltaic control strategy, quantitatively analyzes its influence on the fault phase current, and can adapt to the access of distributed photovoltaics with different control strategies; the delayed current quick-break protection setting method based on the minimum fault phase current proposed by it takes into account the external draw effect of distributed photovoltaics, and the protection must meet the sensitivity requirements, and at the same time, by setting the time difference, the protection can also meet the selectivity requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0098] Figure 1 This is a topological diagram of a distributed photovoltaic distribution network in an embodiment of the present application;

[0099] Figure 2 This is a composite sequence network diagram when a BC two-phase interphase fault occurs at f1 in the embodiment of the present application;

[0100] Figure 3 This is an equivalent circuit diagram when a three-phase short circuit fault occurs at f2 in the embodiment of the present application;

[0101] Figure 4 This is a composite sequence network diagram when a BC two-phase interphase fault occurs at f2 in the embodiment of the present application;

[0102] Figure 5 A schematic diagram of a phase difference variation rule in an embodiment of the present application without low voltage ride-through control;

[0103] Figure 6A schematic diagram of a phase difference variation law with low voltage ride-through control in an embodiment of the present application;

[0104] Figure 7 This is a schematic diagram of the maximum sensitivity angle setting of the power direction element of the new wiring method in the embodiment of the present application;

[0105] Figure 8 This is a schematic diagram of a multi-segment line distribution network containing distributed photovoltaics in an embodiment of the present application;

[0106] Fig. 9A This is the variation law of the fault phase current when the IIDG is in the intermediate state in the embodiment of the present application, and the variation law of the fault occurring upstream of the IDG;

[0107] Fig. 9B This is the variation law of the fault phase current when the IIDG is in the intermediate state in the embodiment of the present application, and the variation law of the fault occurring downstream of the IDG;

[0108] Fig. 10A The variation law of the fault phase current when the IIDG is in a constant power state in the embodiment of the present application, and the variation law of the fault occurring upstream of the IDG;

[0109] Fig. 10B The variation law of the fault phase current when the IIDG is in a constant power state in the embodiment of the present application, and the variation law of the fault occurring downstream of the IDG;

[0110] Fig.11 This is a new intelligent current protection technology flow chart in the embodiment of this application;

[0111] Fig.12 This is a flow chart of an active power distribution network intelligent current protection method in an embodiment of the present application;

[0112] Fig.13 This is one of the flow charts for determining the output current phasor in the embodiment of the present application;

[0113] Fig.14 This is the second flow chart for determining the output current phasor in the embodiment of the present application;

[0114] Fig.15 This is a flow chart of setting the phase difference in an embodiment of the present application;

[0115] Fig.16 A flow chart for determining the action area of ​​a directional element in an embodiment of the present application;

[0116] Fig.17 This is a flow chart for calculating the maximum positive and negative offset phase angles in an embodiment of the present application;

[0117] Fig.18 This is one of the flow charts for calculating the current phasor of each phase in the embodiment of the present application;

[0118] Fig.19 This is the second flow chart of calculating the current phasor of each phase in the embodiment of the present application;

[0119] Fig. 20 A flow chart for obtaining the current quick-break protection setting value in an embodiment of the present application;

[0120] Fig.21 It is a structural diagram of an active power distribution network intelligent current protection device in an embodiment of the present application;

[0121] Fig. 22 This is a structural diagram of an output current determination unit in an embodiment of the present application;

[0122] Fig.23 This is a structural diagram of an output current determination unit in an embodiment of the present application;

[0123] Fig.24 This is a structural diagram of a phase difference calculation unit in an embodiment of the present application;

[0124] Fig.25 This is a structural diagram of an action area determination unit in an embodiment of the present application;

[0125] Fig.26 This is a structural diagram of a maximum offset calculation module in an embodiment of the present application;

[0126] Fig. 27 This is a structural diagram of each phase current determination unit in an embodiment of the present application;

[0127] Fig.28 This is a structural diagram of each phase current determination unit in an embodiment of the present application;

[0128] Fig.29 This is a structural diagram of the protection execution unit in the embodiment of the present application;

[0129] Fig.30 It is a schematic diagram of the structure of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0130] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0131] The information collected in the technical solution of this application is information and data authorized by the user or fully authorized by all parties, and the collection, storage, use, processing, transmission, provision, disclosure and application of relevant data comply with the relevant laws, regulations and standards of relevant countries and regions, take necessary confidentiality measures, do not violate public order and good morals, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0132] Provide users with corresponding operation entrances for them to choose to agree or reject the automated decision-making results; if the user chooses to reject, the expert decision-making process will be entered.

[0133] In one embodiment, in order to analyze the fault characteristics of the distribution network connected to the distributed photovoltaic, the influence of the fault phase current is quantitatively analyzed under the premise of considering the distributed photovoltaic control strategy, and the intelligent current protection of the active distribution network is realized. Fig.12 The present application provides an active distribution network intelligent current protection method, comprising:

[0134] S101: determining the output current phasor of the distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor;

[0135] S102: adjusting the phase difference between the fault phase voltage and the fault phase current according to the fault location and fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, adjusting the phase difference between the fault phase voltage and the fault phase current according to the output current phasor;

[0136] S103: determining a directional element action region according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action region is a phase difference angle range;

[0137] S104: when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, calculating the current phasor of each phase according to the fault occurrence location and the output current phasor;

[0138] S105: Select the current phasor with the smallest modulus value among the current phasors of each phase, calculate the ratio of its modulus value to a preset sensitivity, obtain a current quick-break protection setting value, and implement intelligent current protection for the active distribution network.

[0139] It can be understood that in order to improve the performance of active distribution network protection, the embodiment of the present application proposes a new method for active distribution network protection based on the analysis of the fault characteristics of the voltage and current at the protection installation when faults occur at different locations. First, in combination with the control strategy of distributed photovoltaics, a method for setting the maximum sensitivity angle using the fault phase-to-phase voltage and the fault phase-to-phase current is proposed; then, considering the characteristics of the distributed photovoltaic access to the fault phase current boost and external drain, a delayed current quick-break protection setting method based on the minimum fault phase current is proposed. This technology can make full use of the fault characteristics of the voltage and current at the protection installation under the current fault condition, reduce or eliminate the influence of factors such as distributed photovoltaic capacity (or output), fault location and fault type, and greatly improve the protection performance.

[0140] That is to say, the purpose of the present invention is to consider the influence of distributed photovoltaic control strategy, and propose a new technology of intelligent current protection for active distribution network by analyzing the voltage and current fault characteristics of the protection installation when faults occur at different positions of the active distribution network. Specifically, it includes: a wiring method based on the fault phase voltage and fault phase current, a maximum sensitivity angle setting method, and a delayed current quick-break protection setting method based on the minimum fault phase current. The above method can reduce or eliminate the influence of factors such as distributed photovoltaic capacity (or output), fault location and fault type on protection, and improve the performance of protection.

[0141] Specifically, an active distribution network intelligent current protection method comprises the following steps:

[0142] First, the maximum sensitivity angle of the power direction element under the new wiring method is adjusted as follows:

[0143] (a) Considering that there are multiple distributed photovoltaic grid-connected points on the feeder (different grid-connected points are at different distances from the feeder protection), the capacity of all distributed photovoltaics within the protection range is added up to obtain the aggregated distributed photovoltaic total capacity, and a distributed photovoltaic corresponding to the total capacity is connected to the grid-connected point closest to the protection. Next, under this working condition, the maximum impact range of distributed photovoltaic access on the traditional maximum sensitivity angle (i.e., line impedance angle) is calculated and adjusted.

[0144] (b) Considering the influence of distributed photovoltaic control strategy, the maximum impact range is calculated when the grid connection point voltage is reduced to 0.9 times the rated voltage under the rated power of distributed photovoltaic output (this corresponds to the maximum active current of distributed photovoltaic output, and the access of distributed photovoltaic makes the traditional maximum sensitivity angle larger), and the maximum impact range is calculated when the grid connection point is reduced to the maximum current of distributed photovoltaic output (usually 1.2 times the rated current limit value, and this corresponds to the maximum reactive current of distributed photovoltaic output, and the access of distributed photovoltaic makes the traditional maximum sensitivity angle smaller).

[0145] Then, according to the above principles, the two maximum offset angles (one is a positive value and the other is a negative value) that cause the traditional maximum sensitivity angle to change in opposite directions (increase or decrease) are added, and then half of the value is taken. Finally, the final value obtained by adding the traditional maximum sensitivity angle to this value is used as the new maximum sensitivity angle taking into account the impact of distributed photovoltaic access under the new wiring method, so as to take into account all possible working conditions, and expand 90° to both sides based on the new maximum sensitivity angle, thereby forming the phase difference change range corresponding to the positive direction of the fault under the new power direction element.

[0146] Afterwards, the fault type is determined, and the measured value of the aforementioned phase difference is calculated according to the fault type. If the three-phase currents are all greater than the overcurrent protection setting, it is determined to be a three-phase short circuit fault; if only two phase currents are greater than the overcurrent protection setting, it is determined to be a two-phase short circuit fault. For a three-phase short circuit fault, any two faulty phases are selected, and their phase-to-phase voltage and phase-to-phase current are calculated to obtain the phase difference between the phase-to-phase voltage and the phase-to-phase current; for a two-phase short circuit fault, only the electrical quantities of the two faulty phases can be selected to calculate the phase-to-phase voltage and phase-to-phase current, thereby obtaining the phase difference between the phase-to-phase voltage and the phase-to-phase current under this fault type.

[0147] Next, it is determined whether the phase difference measurement value is within the phase difference variation range corresponding to the positive direction of the fault. If so, the fault is determined to be a positive direction fault; otherwise, the fault is determined to be a reverse direction fault.

[0148] Finally, in order to protect the entire length of the line, the delayed current quick-break protection is set according to the sensitivity of the fault at the end of the line:

[0149]

[0150] In the formula, K is the minimum fault phase current when two phases are short-circuited at the end of the line. sen is the sensitivity, and the action time is set according to the coordination relationship. For three-phase short circuit, the three fault phases are still symmetrical; for two-phase short circuit, find the minimum fault phase current, and set the delayed current quick-break protection according to formula (1). If the directional element determines that it is a positive direction fault, the delayed current quick-break protection will be activated.

[0151] In summary, the flowchart of the new technology of intelligent current protection for active distribution network can be found in Fig.11 shown.

[0152] From the above description, it can be seen that the active distribution network intelligent current protection method provided by the present application can analyze the fault characteristics of the distributed photovoltaic distribution network, and can realize the protection of the active distribution network by only using the relationship between the fault phase voltage and the fault phase current phase difference, without adding additional communication costs and equipment installation costs, and is easy to implement in engineering; it fully considers the influence of factors such as the control strategy, rated capacity, fault type, and fault location of distributed photovoltaic on the protection of the active distribution network, and has good applicability under various fault conditions; it also proposes a setting method for the maximum sensitivity angle, which can make the power direction element have a higher action sensitivity under all possible conditions; it considers the distributed photovoltaic control strategy, quantitatively analyzes its influence on the fault phase current, and can adapt to the access of distributed photovoltaics with different control strategies; the delayed current quick-break protection setting method based on the minimum fault phase current proposed by it takes into account the external draw effect of distributed photovoltaics, and the protection must meet the sensitivity requirements. At the same time, by setting the time difference, the protection can also meet the selectivity requirements.

[0153] In one embodiment, see Fig.13 The output current phasor of the distributed photovoltaic system in the active distribution network is determined according to the rated power, rated line voltage and grid connection point voltage phasor, including:

[0154] S201: Calculate the ratio of the rated line voltage to the modulus value of the grid connection point voltage phasor;

[0155] S202: Determine a phasor calculation model according to a threshold range to which the ratio of the modulus values ​​belongs;

[0156] S203: Calculate the output current phasor using the phasor calculation model.

[0157] Specifically, see Fig.14 The output current phasor of the distributed photovoltaic system in the active distribution network is determined according to the rated power, rated line voltage and grid connection point voltage phasor, including:

[0158] S301: When the distributed photovoltaic system does not have a low voltage ride-through control function, the output current phasor is:

[0159]

[0160] S302: When the distributed photovoltaic system has a low voltage ride-through control function, the output current phasor is:

[0161]

[0162] in, is the output current phasor, P N is the rated power, U N is the rated line voltage, is the grid connection point voltage phasor, and U is the modulus of the grid connection point voltage phasor.

[0163] It is understandable that the following Figure 1 The example of a distributed photovoltaic distribution network shown in the figure provides a detailed explanation of the technical solution for connecting the faulty phases of the directional element.

[0164] First, the aggregation method is adopted to take the sum of the capacities of all distributed photovoltaics within the protection range as the total distributed photovoltaic capacity after aggregation, and the distributed photovoltaics after aggregation are connected to the grid connection point closest to the protection. Figure 1 , taking "protection 1" as the research object, the aggregated distributed photovoltaic is connected to bus B, which is closest to protection 1 within the protection range. Under this condition, the maximum sensitivity angle is adjusted.

[0165] When the IIDG (Inverter Interfaced Distributed Generator, IIDG; in the embodiment of the present application, it refers to distributed photovoltaic) does not have low voltage ride-through control, the output current is:

[0166]

[0167] When IIDG has low voltage ride-through control, the output current is:

[0168]

[0169] in, is the output current phasor, P N , U N They are IIDG rated power and rated line voltage respectively. is the voltage phasor of the IIDG grid connection point, and U is its modulus value.

[0170] From the above description, it can be seen that the active distribution network intelligent current protection method provided in the present application can determine the output current phasor of the distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor.

[0171] In one embodiment, see Fig.15 , the phase difference between the fault phase voltage and the fault phase current is set according to the fault location and fault phase in the active power distribution network, including:

[0172] S401: When a three-phase short circuit fault occurs at the upstream f1 of the distributed photovoltaic, the line impedance angle is determined as the phase difference;

[0173] S402: When a two-phase short circuit fault occurs at the upstream f1 of the distributed photovoltaic system, the phase difference is determined according to the ratio of the fault phase voltage to the phase current;

[0174] S403: When a three-phase short circuit fault or a two-phase short circuit fault occurs at the downstream f2 of the distributed photovoltaic system, the phase difference is calculated according to the output current phasor.

[0175] It can be understood that for the convenience of description, the three operating states shown in formula (3) are named constant power state, intermediate state and constant current state. When a three-phase short circuit occurs in the line, the voltage drop at the grid connection point is serious, and the IIDG is in a constant current state; when a two-phase short circuit occurs, the IIDG is in a constant power state or an intermediate state, and the output current of the IIDG in the constant power state is the same as the current without LVRT control, so only the latter is analyzed.

[0176] (1) When a three-phase short circuit fault occurs at f1 upstream of the IIDG, the three phases remain symmetrical and the IIDG has no effect on protection 1. Therefore, the phase difference measured by the power direction element at protection 1 is the line impedance angle

[0177] (2) When a BC phase-to-phase short circuit fault occurs at f1 upstream of the IIDG, the composite sequence network diagram is as follows: Figure 2 As shown, the phase difference between the fault phase voltage and phase current satisfies:

[0178]

[0179] In the formula, is the fault phase-to-phase voltage when a short circuit occurs between the two phases BC, is the fault phase-to-phase current, the same below; Z Af is the line impedance from bus A to the fault, is the line impedance angle.

[0180] (3) When a three-phase short circuit fault occurs at f2 downstream of the IIDG, the equivalent circuit diagram is as follows Figure 3 As shown, the phase difference between the fault phase voltage and phase current satisfies:

[0181]

[0182] In the formula, is the output current of distributed photovoltaic, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z Bf is the line impedance from bus B to the fault.

[0183] (4) When a BC phase-to-phase short circuit fault occurs at f2 downstream of the IIDG, the composite sequence network diagram is as follows: Figure 4 As shown, the phase difference between the fault phase voltage and phase current is still as shown in formula (5). Therefore, when the IIDG does not have low voltage ride-through control, the phase difference changes with the distributed photovoltaic capacity P N , the variation law of fault position α is as follows Figure 5 As shown in the figure; when IIDG has low voltage ride-through control, the phase difference increases with the distributed photovoltaic capacity P N , the variation law of fault position α is as follows Figure 6 shown.

[0184] In summary, when a fault occurs upstream of the IIDG, the phase difference between the fault phase voltage and the fault phase current is always the line impedance angle It has the highest action sensitivity. When a fault occurs downstream of the IIDG, whether it is a three-phase short circuit or a two-phase short circuit, the phase difference changes in the same way. If the IIDG outputs active power, the maximum sensitivity angle will increase with the increase of the IIDG capacity; if the IIDG outputs reactive power, the maximum sensitivity angle will decrease with the increase of the IIDG capacity, and the phase difference will remain when the IIDG is not connected. The directional element's action sensitivity is less affected.

[0185] From the above description, it can be seen that the active distribution network intelligent current protection method provided in the present application can adjust the phase difference between the fault phase voltage and the fault phase current according to the fault location and fault phase in the active distribution network.

[0186] In one embodiment, see Fig.16 The method of determining the directional element action area according to the obtained conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current includes:

[0187] S501: Calculating the maximum positive and negative offset phase angles according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point;

[0188] S502: Determine the sum of half of the maximum positive and negative offset phase angles and the phase difference as an updated maximum sensitivity angle;

[0189] S503: Determine the sum of the updated maximum sensitivity angle and 90° as the first limit angle of the directional element action area;

[0190] S504: Determine the difference between the updated maximum sensitivity angle and 90° as the second limit angle of the directional element action area;

[0191] S505: Determine an angle range between the first limit angle and the second limit angle as the directional element action area.

[0192] Specifically, see Fig.17 , the positive and negative maximum offset phase angles include a positive maximum offset angle and a negative maximum offset angle; the positive and negative maximum offset phase angles are calculated according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point, including:

[0193] S601: When the modulus of the grid-connected point voltage phasor is reduced to 0.9 times of itself, the distributed photovoltaic output has a maximum active current, so that the traditional maximum sensitivity angle increases, and a positive maximum offset angle is obtained;

[0194] S602: When the modulus of the grid-connected point voltage phasor is reduced to 0.3 times of itself, the distributed photovoltaic output has a maximum reactive current, so that the traditional maximum sensitivity angle is reduced, and a negative maximum offset angle is obtained.

[0195] It can be understood that based on the above phase difference variation law, considering different control strategies of IIDG, when the IIDG grid connection point voltage drops to 0.9U N When the IIDG outputs the maximum active current, the traditional maximum sensitivity angle becomes larger, a positive maximum deviation angle can be calculated; when the grid voltage drops to 0.3U N At this time, IIDG usually outputs 1.2I N The limiting value is the maximum reactive current, making As the value decreases, a negative maximum deviation angle can be calculated.

[0196] If a fault occurs upstream of the IIDG, according to the above analysis and formula (4), regardless of whether the IIDG has low voltage ride-through control, the phase difference between the fault phase voltage and the fault phase current is always the line impedance angle Therefore, the maximum deviation angle is 0.

[0197] If a fault occurs downstream of the IIDG, and the IIDG does not have low voltage ride-through control, Figure 5 As an example, substitute formula (2) into formula (5) and take the IIDG capacity P N The maximum capacity (20MW in the figure) and the fault location coefficient are 1, and the maximum positive deviation angle can be obtained; when the IIDG has low voltage ride-through control, Figure 6 As an example, substitute the constant flow expression of formula (3) into formula (5), and take the IIDG capacity P N The maximum capacity (20MW in the figure) and the fault location coefficient are 1, and the maximum offset angle with a negative value can be obtained.

[0198] Take the sum of the two maximum deviation angles half of Add them together as the new maximum sensitivity angle under the fault phase connection mode taking into account the impact of IIDG access As shown below:

[0199]

[0200] Towards The two sides are expanded by 90° to form a new positive direction action area. The improved directional element action diagram is as follows Figure 7 shown.

[0201] From the above description, it can be seen that the active distribution network intelligent current protection method provided by the present application can determine the directional element action area according to the obtained traditional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current.

[0202] In one embodiment, see Fig.18 , when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault location and the output current phasor, including:

[0203] S701: When it is determined that the phase difference measurement value belongs to the directional element action area, the sum of the system equivalent impedance and the fault line impedance is calculated according to the fault occurrence position to obtain the total impedance;

[0204] S702: Calculate each phase current according to the ratio of the system equivalent potential to the total impedance and the output current phasor.

[0205] It can be understood that the measured value of the phase difference is determined according to the fault type (which can be obtained from the directional element). If the three-phase currents are all greater than the overcurrent protection setting, it is a three-phase short circuit fault. Two of the fault phases are randomly selected to calculate the phase difference between the phase voltage and the phase current; if only two phase currents are greater than the overcurrent protection setting, it is judged as a two-phase short circuit fault. Two fault phases are selected to calculate the phase difference between the phase voltage and the phase current. If the phase difference measurement value is within the phase difference variation range corresponding to the positive direction of the fault, it is judged as a positive direction fault; otherwise, it is judged as a reverse direction fault.

[0206] Specifically, see Fig.19 , when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault location and the output current phasor, including:

[0207] S801: When a BC phase short circuit fault occurs in the upstream distributed photovoltaic line, the current of each phase is:

[0208]

[0209] S802: When a BC phase short circuit fault occurs in the distributed photovoltaic downstream line, the current of each phase is:

[0210]

[0211] in, They are the A phase current phasor, the B phase current phasor, and the C phase current phasor, is the output current phasor, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z BC is the impedance of line BC, Z Bf is the line impedance from bus B to the fault, Z Cf is the line impedance from bus C to the fault, j is an imaginary unit, and j acts on the phasor. Among them, j means that the phase of the phasor rotates 90° counterclockwise, and -j means that the phase of the phasor rotates 90° clockwise.

[0212] It can be understood that, based on the correct judgment of the fault direction, the minimum fault phase current is found and the setting value of the delayed current quick-break protection is calculated. Figure 8 The multi-section line distribution network with distributed photovoltaics shown in the figure provides a detailed description of the delayed current quick-break protection setting method based on the minimum fault phase current.

[0213] (1) When a short circuit fault occurs between the two phases BC on the upstream BC line of the IIDG, the current of each phase measured by protection 1 is:

[0214]

[0215] In the formula, They are the A-phase, B-phase, and C-phase currents measured at protection point 1. is the output current of distributed photovoltaic, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, the same below; Z Bf is the line impedance from bus B to the fault, j is an imaginary unit, and j acts on the phasor. Among them, j means that the phase of the phasor rotates 90° counterclockwise, and -j means that the phase of the phasor rotates 90° clockwise.

[0216] (2) When a short circuit fault occurs between the two phases BC on the CD line downstream of the IIDG, the currents of each phase measured by protection 1 are:

[0217]

[0218] In the formula, They are the A-phase, B-phase, and C-phase currents measured at protection point 1. is the output current of distributed photovoltaic, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z BC is the impedance of line BC, Z Cf is the line impedance from bus C to the fault, Z Bf is the line impedance from bus B to the fault, j is an imaginary unit, and j acts on the phasor. Among them, j means that the phase of the phasor rotates 90° counterclockwise, and -j means that the phase of the phasor rotates 90° clockwise.

[0219] In one embodiment, see Fig. 20 The current phasor with the smallest modulus value among the current phasors of each phase is selected, the ratio of its modulus value to the preset sensitivity is calculated, and the current quick-break protection setting value is obtained to realize the intelligent current protection of the active distribution network, including:

[0220] S901: Compare the module values ​​corresponding to the current phasors of each phase, and determine the smallest one;

[0221] S902: Determine the ratio of the minimum value to the preset sensitivity as the current quick-break protection setting value;

[0222] S903: When it is detected that the short-circuit current reaches the current quick-break protection setting value, the circuit breaker is controlled to operate and isolate the fault circuit.

[0223] It can be understood that when the IIDG is in the intermediate state, the influence of the protection 1 fault phase current is as follows: Fig. 9A , Fig. 9B As shown, the B-phase current measured by protection 1 increases compared to when IIDG is not connected, and the C-phase current decreases compared to when IIDG is not connected, and the increase and decrease increase with the increase of IIDG capacity; when IIDG is in constant power state, the influence law of protection 1 fault phase current is as follows Fig. 10A , Fig. 10B As shown, the B-phase current measured by protection 1 is reduced compared to when IIDG is not connected, and the C-phase current is increased compared to when IIDG is not connected, and the increase and decrease increase with the increase of IIDG capacity. Therefore, in order to enable the delayed current quick-break protection to protect the entire length of the line, the minimum fault phase current when the two phases at the end of the line are short-circuited should be used to set the protection setting.

[0224] In summary, a new technology for intelligent current protection of active distribution network includes the following aspects:

[0225] (1) The maximum sensitivity angle of the power direction element under the new wiring method is adjusted as follows:

[0226] (a) Considering that there are multiple distributed photovoltaic grid-connected points on the feeder (different grid-connected points are at different distances from the feeder protection), the capacity of all distributed photovoltaics within the protection range is added up to obtain the aggregated distributed photovoltaic total capacity, and a distributed photovoltaic corresponding to the total capacity is connected to the grid-connected point closest to the protection. Next, under this working condition, the maximum impact range of distributed photovoltaic access on the traditional maximum sensitivity angle (i.e., line impedance angle) is calculated and adjusted.

[0227] (b) Considering the impact of the distributed photovoltaic low-breakthrough control strategy, the maximum impact range is calculated when the grid-connected point voltage is reduced to 0.9 times the rated voltage under the rated power of distributed photovoltaic output (this corresponds to the maximum active current output of distributed photovoltaic, and the access of distributed photovoltaic makes the traditional maximum sensitivity angle larger), and the maximum impact range is calculated when the grid-connected point is reduced to the maximum current output of distributed photovoltaic (usually a limit value of 1.2 times the rated current, and this corresponds to the maximum reactive current output of distributed photovoltaic, and the access of distributed photovoltaic makes the traditional maximum sensitivity angle smaller).

[0228] (2) According to the above principles, the two maximum offset angles (one positive and one negative) that cause the traditional maximum sensitivity angle to change in opposite directions (increase or decrease) are added together, and then half of the value is taken. Finally, the final value obtained by adding the traditional maximum sensitivity angle to the value is used as the new maximum sensitivity angle under the new wiring method taking into account the impact of distributed photovoltaic access, so as to take into account all possible working conditions, and the new maximum sensitivity angle is used as the reference to expand 90° to both sides, thereby forming the phase difference change range corresponding to the positive direction of the fault under the new power direction element.

[0229] (3) Determine the fault type and calculate the measured value of the aforementioned phase difference according to the fault type. If the three-phase currents are all greater than the overcurrent protection setting, it is determined to be a three-phase short circuit fault; if only two phase currents are greater than the overcurrent protection setting, it is determined to be a two-phase short circuit fault. For a three-phase short circuit fault, arbitrarily select two faulty phases and calculate their phase-to-phase voltage and phase-to-phase current to obtain the phase difference between the phase-to-phase voltage and phase-to-phase current; for a two-phase short circuit fault, only the electrical quantities of the two faulty phases can be selected to calculate the phase-to-phase voltage and phase-to-phase current to obtain the phase difference between the phase-to-phase voltage and phase-to-phase current under this fault type.

[0230] (4) Compare and determine whether the phase difference measurement value is within the phase difference variation range corresponding to the positive direction of the fault. If so, the fault is determined to be a positive direction fault; otherwise, the fault is determined to be a reverse direction fault.

[0231] (5) To protect the entire length of the line, the delayed current quick-break protection is set according to the sensitivity of the fault at the end of the line:

[0232]

[0233] In the formula, K is the minimum fault phase current when two phases are short-circuited at the end of the line. sen is the sensitivity, and the action time is set according to the coordination relationship. For three-phase short circuit, the three fault phases are still symmetrical; for two-phase short circuit, find the minimum fault phase current, and set the delayed current quick-break protection according to formula (9). If the directional element judges that it is a positive direction fault, the delayed current quick-break protection will be activated.

[0234] From the above description, it can be seen that the active distribution network intelligent current protection method provided by the present application can calculate the current phasor of each phase according to the fault location and the output current phasor when it is determined that the phase difference measurement value obtained from the directional element belongs to the action area of ​​the directional element.

[0235] Based on the same inventive concept, the embodiments of the present application also provide an active distribution network intelligent current protection device, which can be used to implement the method described in the above embodiments, as described in the following embodiments. Since the principle of solving the problem by the active distribution network intelligent current protection device is similar to that of the active distribution network intelligent current protection method, the implementation of the active distribution network intelligent current protection device can refer to the implementation of the method based on software performance benchmark determination, and the repeated parts will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the system described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0236] In one embodiment, see Fig.21 In order to analyze the fault characteristics of the distribution network connected to the distributed photovoltaic power generation, quantitatively analyze the influence of the fault phase current on the fault phase current under the premise of considering the distributed photovoltaic control strategy, and realize the intelligent current protection of the active distribution network, the present application provides an active distribution network intelligent current protection device, including:

[0237] The output current determination unit 2101 is used to determine the output current phasor of the distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor;

[0238] The phase difference calculation unit 2102 is used to set the phase difference between the fault phase voltage and the fault phase current according to the fault location and the fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, the phase difference between the fault phase voltage and the fault phase current is set according to the output current phasor;

[0239] An action region determining unit 2103 is used to determine a directional element action region according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action region is a phase difference angle range;

[0240] The phase current determination unit 2104 is used to calculate the phase current phasor of each phase according to the fault location and the output current phasor when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area;

[0241] The protection execution unit 2105 is used to select the current phasor with the smallest modulus value among the current phasors of each phase, calculate the ratio of its modulus value to the preset sensitivity, obtain the current quick-break protection setting value, and realize the intelligent current protection of the active distribution network.

[0242] In one embodiment, see Fig. 22 , the output current determining unit 2101 comprises:

[0243] A module value ratio calculation module 2201 is used to calculate the ratio of the module value of the rated line voltage to the grid connection point voltage phasor;

[0244] A calculation model selection module 2202 is used to determine a phasor calculation model according to a threshold range to which the ratio of the module values ​​belongs;

[0245] The output current calculation module 2203 is used to calculate the output current phasor using the phasor calculation model.

[0246] In one embodiment, see Fig.23 , the output current determining unit 2101 comprises:

[0247] The first output current calculation module 2301 is used for when the distributed photovoltaic does not have a low voltage ride-through control function, the output current phasor is:

[0248]

[0249] The second output current calculation module 2302 is used for when the distributed photovoltaic has a low voltage ride-through control function, the output current phasor is:

[0250]

[0251] in, is the output current phasor, P N is the rated power, U N is the rated line voltage, is the grid connection point voltage phasor, and U is the modulus of the grid connection point voltage phasor.

[0252] In one embodiment, see Fig.24 , the phase difference calculation unit 2102 comprises:

[0253] The first phase difference calculation module 2401 is used to determine the line impedance angle as the phase difference when a three-phase short circuit fault occurs at the upstream f1 of the distributed photovoltaic;

[0254] The second phase difference calculation module 2402 is used to determine the phase difference according to the ratio of the fault phase voltage to the phase current when a two-phase short circuit fault occurs at the upstream f1 of the distributed photovoltaic system;

[0255] The third phase difference calculation module 2403 is used to calculate the phase difference according to the output current phasor when a three-phase short circuit fault or a two-phase short circuit fault occurs at the downstream f2 of the distributed photovoltaic.

[0256] In one embodiment, see Fig.25 , the action area determination unit 2103 includes:

[0257] The maximum offset calculation module 2501 is used to calculate the positive and negative maximum offset phase angles according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point;

[0258] A maximum sensitivity updating module 2502, configured to determine the sum of half of the positive and negative maximum offset phase angles and the phase difference as an updated maximum sensitivity angle;

[0259] A first margin determination module 2503, configured to determine the sum of the updated maximum sensitivity angle and 90° as the first margin angle of the directional element action area;

[0260] A second margin determination module 2504, configured to determine the difference between the updated maximum sensitivity angle and 90° as a second margin angle of the directional element action area;

[0261] The action area determination module 2505 is used to determine the angle range between the first limit angle and the second limit angle as the directional element action area.

[0262] In one embodiment, see Fig.26 The positive and negative maximum offset phase angles include a positive maximum offset angle and a negative maximum offset angle; the maximum offset calculation module 2501 includes:

[0263] A positive offset calculation module 2601 is used for, when the modulus of the grid-connected point voltage phasor is reduced to 0.9 times of itself, the distributed photovoltaic output has the maximum active current, so that the traditional maximum sensitivity angle increases, and the maximum offset angle of the positive value is obtained;

[0264] The negative offset calculation module 2602 is used to, when the modulus of the grid-connected point voltage phasor is reduced to 0.3 times of itself, output the maximum reactive current of the distributed photovoltaic system, so that the traditional maximum sensitivity angle is reduced to obtain a negative maximum offset angle.

[0265] In one embodiment, see Fig. 27 , the phase current determination unit 2104 comprises:

[0266] The impedance sum calculation module 2701 is used to calculate the sum of the system equivalent impedance and the fault line impedance according to the fault location to obtain the total impedance when it is determined that the phase difference measurement value belongs to the directional element action area;

[0267] The current calculation module 2702 for each phase is used to calculate the current for each phase according to the ratio of the system equivalent potential to the total impedance and the output current phasor.

[0268] In one embodiment, see Fig.28 , the phase current determination unit 2104 comprises:

[0269] The first phase current determination module 2801 is used for determining the current of each phase when a BC two-phase short circuit fault occurs in the distributed photovoltaic upstream line:

[0270]

[0271] The second phase current determination module 2802 is used for determining the current of each phase when a BC phase short circuit fault occurs in the distributed photovoltaic downstream line:

[0272]

[0273] in, They are the A phase current phasor, the B phase current phasor, and the C phase current phasor, is the output current phasor, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z BC is the impedance of line BC, Z Bf is the line impedance from bus B to the fault, Z Cf is the line impedance from bus C to the fault.

[0274] In one embodiment, see Fig.29 , the protection execution unit 2105 includes:

[0275] A minimum determination module 2901 is used to compare the module values ​​corresponding to the current phasors of each phase and determine the smallest one among them;

[0276] A ratio setting module 2902, used to determine the ratio of the minimum value to a preset sensitivity as the current quick-break protection setting value;

[0277] The isolation action module 2903 is used to control the circuit breaker to operate and isolate the fault circuit when it is detected that the short-circuit current reaches the current quick-break protection setting value.

[0278] From the hardware level, in order to be able to analyze the fault characteristics of the distribution network connected to the distributed photovoltaic, under the premise of considering the distributed photovoltaic control strategy, quantitatively analyze its impact on the fault phase current, and realize the intelligent current protection of the active distribution network, the application provides an embodiment of an electronic device for realizing all or part of the contents of the active distribution network intelligent current protection method, and the electronic device specifically includes the following contents:

[0279] Processor, memory, communication interface and bus; wherein the processor, memory and communication interface communicate with each other through the bus; the communication interface is used to realize information transmission between the active distribution network intelligent current protection device and related devices such as core business systems, user terminals and related databases; the logic controller can be a desktop computer, a tablet computer and a mobile terminal, etc., and the present embodiment is not limited thereto. In the present embodiment, the logic controller can be implemented with reference to the embodiment of the active distribution network intelligent current protection method and the embodiment of the active distribution network intelligent current protection device in the embodiment, and the contents thereof are incorporated herein, and the repeated parts are not repeated.

[0280] It is understandable that the user terminal may include a smart phone, a tablet electronic device, a network set-top box, a portable computer, a desktop computer, a personal digital assistant (PDA), a vehicle-mounted device, a smart wearable device, etc. Among them, the smart wearable device may include smart glasses, a smart watch, a smart bracelet, etc.

[0281] In practical applications, part of the active distribution network intelligent current protection method can be executed on the electronic device side as described above, or all operations can be completed in the client device. The specific selection can be based on the processing capability of the client device and the limitations of the user's usage scenario. This application does not limit this. If all operations are completed in the client device, the client device may also include a processor.

[0282] The client device may have a communication module (i.e., a communication unit) that can communicate with a remote server to achieve data transmission with the server. The server may include a server on the task scheduling center side, and other implementation scenarios may also include a server on an intermediate platform, such as a server on a third-party server platform that has a communication link with the task scheduling center server. The server may include a single computer device, or a server cluster consisting of multiple servers, or a server structure of a distributed device.

[0283] Fig.30 FIG. 9 is a schematic block diagram of the system structure of the electronic device 9600 according to an embodiment of the present application. Fig.30 As shown, the electronic device 9600 may include a central processor 9100 and a memory 9140; the memory 9140 is coupled to the central processor 9100. It is worth noting that Fig.30 is exemplary; other types of structures may also be used to supplement or replace this structure to implement telecommunication functions or other functions.

[0284] In one embodiment, the function of the active power distribution network intelligent current protection method can be integrated into the central processor 9100. The central processor 9100 can be configured to perform the following control:

[0285] S101: determining the output current phasor of the distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor;

[0286] S102: adjusting the phase difference between the fault phase voltage and the fault phase current according to the fault location and fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, adjusting the phase difference between the fault phase voltage and the fault phase current according to the output current phasor;

[0287] S103: determining a directional element action region according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action region is a phase difference angle range;

[0288] S104: when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, calculating the current phasor of each phase according to the fault occurrence location and the output current phasor;

[0289] S105: Select the current phasor with the smallest modulus value among the current phasors of each phase, calculate the ratio of its modulus value to a preset sensitivity, obtain a current quick-break protection setting value, and implement intelligent current protection for the active distribution network.

[0290] From the above description, it can be seen that the active distribution network intelligent current protection method provided by the present application can analyze the fault characteristics of the distributed photovoltaic distribution network, and can realize the protection of the active distribution network by only using the relationship between the fault phase voltage and the fault phase current phase difference, without adding additional communication costs and equipment installation costs, and is easy to implement in engineering; it fully considers the influence of factors such as the control strategy, rated capacity, fault type, and fault location of distributed photovoltaic on the protection of the active distribution network, and has good applicability under various fault conditions; it also proposes a setting method for the maximum sensitivity angle, which can make the power direction element have a higher action sensitivity under all possible conditions; it considers the distributed photovoltaic control strategy, quantitatively analyzes its influence on the fault phase current, and can adapt to the access of distributed photovoltaics with different control strategies; the delayed current quick-break protection setting method based on the minimum fault phase current proposed by it takes into account the external draw effect of distributed photovoltaics, and the protection must meet the sensitivity requirements. At the same time, by setting the time difference, the protection can also meet the selectivity requirements.

[0291] In another embodiment, the active distribution network intelligent current protection device can be configured separately from the central processor 9100. For example, the data composite transmission device active distribution network intelligent current protection device can be configured as a chip connected to the central processor 9100, and the function of the active distribution network intelligent current protection method is realized through the control of the central processor.

[0292] like Fig.30 As shown, the electronic device 9600 may also include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It is worth noting that the electronic device 9600 does not necessarily have to include Fig.30 In addition, the electronic device 9600 may also include Fig.30 For components not shown, reference may be made to the prior art.

[0293] like Fig.30 As shown, the central processing unit 9100 is sometimes also referred to as a controller or an operation control, and may include a microprocessor or other processor device and / or logic device. The central processing unit 9100 receives input and controls the operation of various components of the electronic device 9600.

[0294] The memory 9140 may be, for example, one or more of a cache, a flash memory, a hard drive, a removable medium, a volatile memory, a non-volatile memory or other suitable devices. The above-mentioned information related to the failure may be stored, and a program for executing the relevant information may also be stored. The CPU 9100 may execute the program stored in the memory 9140 to implement information storage or processing, etc.

[0295] The input unit 9120 provides input to the central processing unit 9100. The input unit 9120 is, for example, a key or a touch input device. The power supply 9170 is used to provide power to the electronic device 9600. The display 9160 is used to display display objects such as images and texts. The display may be, for example, an LCD display, but is not limited thereto.

[0296] The memory 9140 may be a solid-state memory, such as a read-only memory (ROM), a random access memory (RAM), a SIM card, etc. It may also be a memory that saves information even when the power is off, can be selectively erased, and is provided with more data, examples of which are sometimes referred to as EPROMs, etc. The memory 9140 may also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 may include an application / function storage unit 9142, which is used to store application programs and function programs or processes for executing the operation of the electronic device 9600 through the central processor 9100.

[0297] The memory 9140 may also include a data storage unit 9143 for storing data, such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 may include various drivers for communication functions of the electronic device and / or for executing other functions of the electronic device (such as messaging applications, address book applications, etc.).

[0298] The communication module 9110 is a transmitter / receiver that sends and receives signals via the antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processor 9100 to provide input signals and receive output signals, which may be the same as the case of a conventional mobile communication terminal.

[0299] Based on different communication technologies, multiple communication modules 9110 may be provided in the same electronic device, such as a cellular network module, a Bluetooth module and / or a wireless LAN module. The communication module (transmitter / receiver) 9110 is also coupled to a speaker 9131 and a microphone 9132 via an audio processor 9130 to provide an audio output via the speaker 9131 and receive an audio input from the microphone 9132, thereby realizing a common telecommunication function. The audio processor 9130 may include any suitable buffer, decoder, amplifier, etc. In addition, the audio processor 9130 is also coupled to the central processor 9100, so that recording can be performed on the local machine through the microphone 9132, and the sound stored on the local machine can be played through the speaker 9131.

[0300] The embodiments of the present application also provide a computer-readable storage medium capable of implementing all the steps of the active distribution network intelligent current protection method in the above embodiments, where the execution subject is a server or a client. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, all the steps of the active distribution network intelligent current protection method in the above embodiments are implemented, where the execution subject is a server or a client. For example, when the processor executes the computer program, the following steps are implemented:

[0301] S101: determining the output current phasor of the distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor;

[0302] S102: adjusting the phase difference between the fault phase voltage and the fault phase current according to the fault location and fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, adjusting the phase difference between the fault phase voltage and the fault phase current according to the output current phasor;

[0303] S103: determining a directional element action region according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action region is a phase difference angle range;

[0304] S104: when it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, calculating the current phasor of each phase according to the fault occurrence location and the output current phasor;

[0305] S105: Select the current phasor with the smallest modulus value among the current phasors of each phase, calculate the ratio of its modulus value to a preset sensitivity, obtain a current quick-break protection setting value, and implement intelligent current protection for the active distribution network.

[0306] From the above description, it can be seen that the active distribution network intelligent current protection method provided by the present application can analyze the fault characteristics of the distributed photovoltaic distribution network, and can realize the protection of the active distribution network by only using the relationship between the fault phase voltage and the fault phase current phase difference, without adding additional communication costs and equipment installation costs, and is easy to implement in engineering; it fully considers the influence of factors such as the control strategy, rated capacity, fault type, and fault location of distributed photovoltaic on the protection of the active distribution network, and has good applicability under various fault conditions; it also proposes a setting method for the maximum sensitivity angle, which can make the power direction element have a higher action sensitivity under all possible conditions; it considers the distributed photovoltaic control strategy, quantitatively analyzes its influence on the fault phase current, and can adapt to the access of distributed photovoltaics with different control strategies; the delayed current quick-break protection setting method based on the minimum fault phase current proposed by it takes into account the external draw effect of distributed photovoltaics, and the protection must meet the sensitivity requirements. At the same time, by setting the time difference, the protection can also meet the selectivity requirements.

[0307] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0308] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (apparatus), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0309] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0310] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0311] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An active distribution network intelligent current protection method, characterized in that: include: Determine the output current phasor of distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor; The phase difference between the fault phase voltage and the fault phase current is set according to the fault location and the fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, the phase difference between the fault phase voltage and the fault phase current is set according to the output current phasor; Determine the directional element action area according to the acquired traditional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action area is the phase difference angle range; When it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault occurrence location and the output current phasor; The current phasor with the smallest modulus value among the current phasors of each phase is selected, the ratio of its modulus value to the preset sensitivity is calculated, and the current quick-break protection setting value is obtained to realize intelligent current protection for the active distribution network.

2. The active power distribution network intelligent current protection method according to claim 1, characterized in that: The method of determining the output current phasor of the distributed photovoltaic system in the active power distribution network according to the rated power, rated line voltage and grid connection point voltage phasor includes: Calculating the ratio of the rated line voltage to the modulus value of the grid connection point voltage phasor; Determining a phasor calculation model according to a threshold range to which the ratio of the modulus values ​​belongs; The output current phasor is calculated using the phasor calculation model.

3. The active power distribution network intelligent current protection method according to claim 1, characterized in that: The method of determining the output current phasor of the distributed photovoltaic system in the active power distribution network according to the rated power, rated line voltage and grid connection point voltage phasor includes: When the distributed photovoltaic system does not have a low voltage ride-through control function, the output current phasor is: When the distributed photovoltaic system has a low voltage ride-through control function, the output current phasor is: in, is the output current phasor, P N is the rated power, U N is the rated line voltage, is the grid connection point voltage phasor, and U is the modulus of the grid connection point voltage phasor.

4. The active power distribution network intelligent current protection method according to claim 1, characterized in that: The step of setting the phase difference between the fault phase voltage and the fault phase current according to the fault location and the fault phase in the active power distribution network comprises: When a three-phase short circuit fault occurs upstream of the distributed photovoltaic system, the line impedance angle is determined as the phase difference; When a two-phase short circuit fault occurs in the upstream of the distributed photovoltaic system, the phase difference is determined according to the ratio of the fault phase voltage to the phase current; wherein, In the formula, is the fault phase-to-phase voltage when a short circuit occurs between the two phases BC, is the fault phase current, Z Af is the line impedance from bus A to the fault, is the line impedance angle; When a three-phase short circuit fault or a two-phase short circuit fault occurs in the downstream of the distributed photovoltaic system, the phase difference is calculated according to the output current phasor; wherein, In the formula, is the fault phase-to-phase voltage when a short circuit occurs between the two phases BC, is the fault phase current, is the output current of distributed photovoltaic, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z Bf is the line impedance from bus B to the fault.

5. The active power distribution network intelligent current protection method according to claim 1, characterized in that: The step of determining the directional element action area according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current comprises: Calculating the maximum positive and negative offset phase angles according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point; Determine the sum of half of the positive and negative maximum offset phase angles and the phase difference as the updated maximum sensitivity angle; Determine the sum of the updated maximum sensitivity angle and 90° as the first limit angle of the directional element action area; Determine the difference between the updated maximum sensitivity angle and 90° as the second limit angle of the directional element action area; An angle range between the first limit angle and the second limit angle is determined as the directional element action area.

6. The active power distribution network intelligent current protection method according to claim 5, characterized in that: The positive and negative maximum offset phase angles include a positive maximum offset angle and a negative maximum offset angle; The calculating of the positive and negative maximum offset phase angles according to the voltage phasor, the maximum active current and the maximum reactive current of the grid-connected point of the distributed photovoltaic system includes: When the modulus of the grid-connected point voltage phasor is reduced to 0.9 times of itself, the distributed photovoltaic output has the maximum active current, so that the traditional maximum sensitivity angle increases, and a positive maximum offset angle is obtained; When the modulus of the grid-connected point voltage phasor is reduced to 0.3 times of itself, the distributed photovoltaic output has the maximum reactive current, so that the traditional maximum sensitivity angle is reduced, and a negative maximum offset angle is obtained.

7. The active power distribution network intelligent current protection method according to claim 1, characterized in that: When it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault location and the output current phasor, including: When it is determined that the phase difference measurement value belongs to the directional element action area, the sum of the system equivalent impedance and the fault line impedance is calculated according to the fault occurrence position to obtain the total impedance; The current of each phase is calculated according to the ratio of the system equivalent potential to the total impedance and the output current phasor.

8. The active power distribution network intelligent current protection method according to claim 1, characterized in that: When it is determined that the phase difference measurement value obtained from the directional element belongs to the directional element action area, the current phasor of each phase is calculated according to the fault location and the output current phasor, including: When a BC two-phase short circuit fault occurs in the distributed photovoltaic upstream line, the current of each phase is: When a BC phase short circuit fault occurs in the distributed photovoltaic downstream line, the current of each phase is: in, They are the A phase current phasor, the B phase current phasor, and the C phase current phasor, respectively. is the output current phasor, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z BC is the impedance of line BC, Z Bf is the line impedance from bus B to the fault, Z Cf is the line impedance from bus C to the fault.

9. The active power distribution network intelligent current protection method according to claim 1, characterized in that: The current phasor with the smallest modulus value among the current phasors of each phase is selected, the ratio of its modulus value to the preset sensitivity is calculated, and the current quick-break protection setting value is obtained to realize the intelligent current protection of the active distribution network, including: Compare the modulus values ​​corresponding to the current phasors of each phase and determine the smallest one; The ratio of the minimum value to the preset sensitivity is determined as the current quick-break protection setting value; When it is detected that the short-circuit current reaches the current quick-break protection setting value, the circuit breaker is controlled to operate and isolate the fault circuit.

10. An active power distribution network intelligent current protection device, characterized in that: include: An output current determination unit, used to determine the output current phasor of the distributed photovoltaic in the active distribution network according to the rated power, rated line voltage and grid connection point voltage phasor; A phase difference calculation unit, used for adjusting the phase difference between the fault phase voltage and the fault phase current according to the fault location and the fault phase in the active distribution network; wherein, when the fault location is located downstream of the distributed photovoltaic, the phase difference between the fault phase voltage and the fault phase current is adjusted according to the output current phasor; An action region determination unit, configured to determine a directional element action region according to the acquired conventional maximum sensitivity angle and the phase difference between the fault phase voltage and the fault phase current; wherein the directional element action region is a phase difference angle range; a current determination unit for each phase, configured to calculate the current phasor of each phase according to the fault occurrence location and the output current phasor when it is determined that the phase difference measurement value obtained from the directional element belongs to the action area of ​​the directional element; The protection execution unit is used to select the current phasor with the smallest modulus value among the current phasors of each phase, calculate the ratio of its modulus value to a preset sensitivity, obtain a current quick-break protection setting value, and realize intelligent current protection for the active distribution network.

11. The active power distribution network intelligent current protection device according to claim 10, characterized in that: The output current determining unit comprises: A module value ratio calculation module, used to calculate the ratio of the module value of the rated line voltage to the grid connection point voltage phasor; A calculation model selection module, used for determining a phasor calculation model according to a threshold range to which the ratio of the module values ​​belongs; The output current calculation module is used to calculate the output current phasor using the phasor calculation model.

12. The active power distribution network intelligent current protection device according to claim 10, characterized in that: The output current determining unit comprises: The first output current calculation module is used for when the distributed photovoltaic does not have a low voltage ride-through control function, the output current phasor is: The second output current calculation module is used when the distributed photovoltaic has a low voltage ride-through control function, and the output current phasor is: in, is the output current phasor, P N is the rated power, U N is the rated line voltage, is the grid connection point voltage phasor, and U is the modulus of the grid connection point voltage phasor.

13. The active power distribution network intelligent current protection device according to claim 10, characterized in that: The phase difference calculation unit comprises: A first phase difference calculation module is used to determine the line impedance angle as the phase difference when a three-phase short circuit fault occurs upstream of the distributed photovoltaic system; The second phase difference calculation module is used to determine the phase difference according to the ratio of the fault phase voltage to the phase current when a two-phase short circuit fault occurs in the upstream of the distributed photovoltaic system; wherein, In the formula, is the fault phase-to-phase voltage when a short circuit occurs between the two phases BC, is the fault phase current, Z Af is the line impedance from bus A to the fault, is the line impedance angle; The third phase difference calculation module is used to calculate the phase difference according to the output current phasor when a three-phase short circuit fault or a two-phase short circuit fault occurs in the downstream of the distributed photovoltaic system; wherein, In the formula, is the fault phase-to-phase voltage when a short circuit occurs between the two phases BC, is the fault phase current, is the output current of distributed photovoltaic, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z Bf is the line impedance from bus B to the fault.

14. The active power distribution network intelligent current protection device according to claim 10, characterized in that: The action area determination unit includes: A maximum offset calculation module, used to calculate the positive and negative maximum offset phase angles according to the voltage phasor, maximum active current and maximum reactive current of the distributed photovoltaic grid connection point; A maximum sensitivity update module, used to determine the sum of half of the positive and negative maximum offset phase angles and the phase difference as an updated maximum sensitivity angle; A first margin determination module, used for determining the sum of the updated maximum sensitivity angle and 90° as the first margin angle of the directional element action area; A second margin determination module, used for determining the difference between the updated maximum sensitivity angle and 90° as a second margin angle of the directional element action area; The action area determination module is used to determine the angle range between the first limit angle and the second limit angle as the directional element action area.

15. The active power distribution network intelligent current protection device according to claim 14, characterized in that: The positive and negative maximum offset phase angles include a positive maximum offset angle and a negative maximum offset angle; The maximum offset calculation module comprises: A positive offset calculation module is used for, when the modulus of the grid-connected point voltage phasor is reduced to 0.9 times of itself, the distributed photovoltaic output has the maximum active current, so that the traditional maximum sensitivity angle is increased, and the maximum offset angle of the positive value is obtained; The negative offset calculation module is used to output the maximum reactive current of the distributed photovoltaic when the modulus of the grid-connected point voltage phasor is reduced to 0.3 times of itself, so that the traditional maximum sensitivity angle is reduced to obtain the maximum offset angle of negative value.

16. The active power distribution network intelligent current protection device according to claim 10, characterized in that: The phase current determination unit comprises: An impedance sum calculation module, used for calculating the sum of the system equivalent impedance and the fault line impedance according to the fault occurrence position to obtain the total impedance when it is determined that the phase difference measurement value belongs to the directional element action area; The current calculation module for each phase is used to calculate the current for each phase according to the ratio of the system equivalent potential to the total impedance and the output current phasor.

17. The active power distribution network intelligent current protection device according to claim 10, characterized in that: The phase current determination unit comprises: The first phase current determination module is used for determining the current of each phase when a BC two-phase short circuit fault occurs in the distributed photovoltaic upstream line: The second phase current determination module is used for when a BC two-phase short circuit fault occurs in the distributed photovoltaic downstream line, and the current of each phase is: in, They are the A phase current phasor, the B phase current phasor, and the C phase current phasor, respectively. is the output current phasor, is the equivalent potential of the system, Z s is the internal impedance of the system, Z AB is the impedance of line AB, Z BC is the impedance of line BC, Z Bf is the line impedance from bus B to the fault, Z Cf is the line impedance from bus C to the fault.

18. The active power distribution network intelligent current protection device according to claim 10, characterized in that: The protection execution unit comprises: A minimum determination module is used to compare the module values ​​corresponding to the current phasors of each phase and determine the smallest one among them; A ratio setting module, used for determining the ratio of the minimum value to a preset sensitivity as the current quick-break protection setting value; The isolation action module is used to control the circuit breaker to operate and isolate the fault circuit when it is detected that the short-circuit current reaches the current quick-break protection setting value.

19. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the active distribution network intelligent current protection method according to any one of claims 1 to 9 are implemented.

20. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the active distribution network intelligent current protection method according to any one of claims 1 to 9 are implemented.

21. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the steps of the active distribution network intelligent current protection method according to any one of claims 1 to 9 are implemented.

Images