A power flow reversal control system and method for a photovoltaic power distribution ring network box

Abstract

The present application belongs to the field of switching control technology of distribution network ring main unit in distributed photovoltaic substation, and discloses a kind of photovoltaic substation ring main unit power flow reversal control system and method, the system includes state data acquisition module, switching object confirmation module, power supply path judging module, reverse support judging module, implicit anti-feeding identification module and switching control module;System according to switching request, switch position, to-be-switched side voltage, active direction and associated substation reverse support representation data, determine target interconnection interval, to-be-switched side and associated photovoltaic substation, judge whether to-be-switched side forms upper power supply path, and identify implicit anti-feeding state in combination with voltage maintaining state and reverse support state;When identifying implicit anti-feeding state, output switching lockout, delay or review instruction, output switching permission instruction when not identified and meet switching condition, improve switching safety under photovoltaic substation reverse support scenario.

Description

Technical Field

[0001] This invention relates to the field of power distribution network ring network box closing control technology, and particularly to a power flow reversal control system and method for a photovoltaic distribution network ring network box. Background Technology

[0002] As the proportion of distributed photovoltaic (PV) systems connected to low-voltage distribution areas increases, some areas, when PV output is high and local load is low, will switch from receiving power to feeding power back to the upstream distribution lines. For distribution areas using ring mains power supply, the actual energized state on both sides of the tie interval directly affects the safety of closing the circuit when the ring mains is closed, restored, or restored after maintenance.

[0003] Existing ring main unit automation control typically determines whether the tie-line can be closed based on switch position, bus voltage, current magnitude, or whether undervoltage / on-voltage conditions are met. This type of judgment method is mainly suitable for power distribution scenarios where the power supply direction is relatively clear and the load flow direction is relatively stable.

[0004] However, in a photovoltaic (PV) power flow reversal scenario, downstream PV units may provide reverse support to the medium-voltage side via a distribution transformer. In this case, the ring main unit's waiting-to-close side may not be powered by a conventional upstream power source, but it still exhibits a certain voltage maintenance state or a low-current state. This state differs from both a conventional stable energized state and a completely de-energized state. If the closing conditions are judged solely based on whether the voltage on the waiting-to-close side reaches the energizing threshold, or solely based on whether the current is low, the implicit reverse power supply state formed by the PV reverse support can easily be misjudged as a safe closing state.

[0005] Furthermore, photovoltaic reverse support typically exhibits characteristics such as low short-circuit capacity, power direction fluctuating with photovoltaic output, and inconsistent power supply status with the upstream power source. Existing conventional on / off detection methods struggle to distinguish this state from residual voltage, induced voltage, measurement errors, or normal energized states. This leads to risks such as inter-source closing, superimposed reverse power supply, re-energization of faulty sections, or abnormal protection coordination when the ring main unit is closed or restored.

[0006] Therefore, there is an urgent need for a power flow reversal control method suitable for photovoltaic grid ring boxes, which can identify the implicit reverse power supply state formed by the reverse support of the lower-level photovoltaic grid before the tie-bar is closed, and block, delay or permit control the closing action based on the identification result, thereby improving the safety of ring box closing control. Summary of the Invention

[0007] The first objective of this invention is to provide a power flow reversal control system for a photovoltaic distribution area ring network box, which has the advantage of identifying the implicit reverse power supply state formed by the reverse support of the photovoltaic distribution area before the connection bay is closed, and controlling the closing action accordingly, thereby reducing the risk of accidental closing.

[0008] The above-mentioned technical objectives of the present invention are achieved through the following technical solutions: A power flow reversal control system for a photovoltaic power distribution ring network box includes: The status data acquisition module is used to acquire the target ring network box's closing request information, switch position data, voltage data on the side to be closed, active power direction data of the associated outgoing line interval, and reverse support characterization data of the associated transformer area; The closing object confirmation module is used to determine the target connection interval, the side to be closed corresponding to the target connection interval, and the associated photovoltaic area that has a power supply association with the side to be closed, based on the switch position data and the preset ring network topology when the closing request information is received. The power supply path determination module is used to determine whether an upstream power supply path is formed on the side to be closed, based on the switch position data and the preset ring network topology. The reverse support judgment module is used to determine whether the associated photovoltaic area has the state of outputting reverse power to the side to be closed through the distribution transformer based on the active power direction data of the associated outgoing line interval and the reverse support characterization data of the associated transformer area, and to determine the state as the reverse support state. The implicit reverse power transmission identification module is used to determine whether the voltage holding state still exists on the side to be closed when the upstream power supply path has not been formed on the side to be closed; it is also used to determine that there is an implicit reverse power transmission state formed by the reverse support of the associated photovoltaic area on the side to be closed when the voltage holding state and the reverse support state are in the same closing verification time window. The closing control module is used to output a closing interlock command, a closing delay command, or a closing verification command to the target communication interval when the implicit reverse power transmission state is detected; it is also used to output a closing permission command when the implicit reverse power transmission state is not detected and the preset closing conditions are met.

[0009] Furthermore, the implicit reverse power transmission identification module includes a voltage holding judgment unit. The voltage holding judgment unit is used to acquire the voltage change status of the voltage data of the side to be closed within a preset holding judgment time period when the power supply path judgment module determines that the upper-level power supply path has not been formed on the side to be closed. When the voltage data of the side to be closed is within a preset voltage holding range within the preset holding judgment time period, the duration reaches the preset holding time, and there is no trend of continuous decay to a state of voltage loss, it is determined that the voltage holding state exists on the side to be closed.

[0010] Furthermore, the associated transformer area reverse support characterization data includes the transformer power direction data of the associated photovoltaic transformer area; The reverse support judgment module includes a transformer direction judgment unit, which is used to determine whether there is reverse power from the low-voltage side to the medium-voltage ring network box side in the associated photovoltaic area within the same direction confirmation time window based on the transformer power direction data. When the backfeeding power exists, the backfeeding power is determined as a candidate backfeeding power.

[0011] Furthermore, the associated photovoltaic distribution area reverse support characterization data includes the photovoltaic output data and load data of the associated photovoltaic distribution area within the same sampling time window; The reverse support judgment module includes a net reverse transmission judgment unit, which is used to determine the net reverse transmission power of the associated photovoltaic power distribution area based on the photovoltaic power output data and the load data of the distribution area. When the photovoltaic output data of the transformer area is greater than the load data of the transformer area, and the difference between the two reaches a preset back-feed margin, it is determined that there is a candidate net back-feed power in the associated photovoltaic transformer area, and the candidate net back-feed power is used as the candidate back-feed power.

[0012] Furthermore, the reverse support judgment module includes a direction consistency verification unit; The directional consistency verification unit is used to determine the reverse support path from the associated photovoltaic area through the corresponding associated outgoing line interval to the side to be closed, based on the preset ring network topology. It is also used to compare the active power flow direction represented by the active power direction data of the associated outgoing line interval with the direction of the reverse support path; When the active power flow direction is consistent with the direction of the reverse support path, the candidate reverse power is used to determine whether the associated photovoltaic area has the reverse support state.

[0013] Furthermore, the implicit reverse power transmission identification module includes a time correlation judgment unit; The time correlation judgment unit is used to determine the voltage holding interval corresponding to the voltage holding state and the reverse support interval corresponding to the reverse support state within the closing verification time window. When the voltage holding interval and the reverse support interval overlap within the closing verification time window, and the overlap duration reaches the preset correlation duration, it is determined that the voltage holding state and the reverse support state satisfy the time correlation condition.

[0014] Furthermore, the implicit reverse power transmission identification module includes a non-reverse voltage exclusion unit; The non-reverse voltage exclusion unit is used to acquire the voltage change status of the voltage data on the side to be closed within a preset exclusion judgment time period when the voltage holding state exists on the side to be closed. When the voltage data on the side to be closed continues to decrease and falls below the preset undervoltage threshold during the preset exclusion judgment time period, and there is no reverse support state within the same closing verification time window, the voltage holding state is determined to be a non-reverse voltage state. When determining the non-reverse voltage state, the voltage holding state is not used to determine the implicit reverse voltage state.

[0015] Furthermore, the closing control module includes a lockout verification unit; The interlocking verification unit is used to trigger the implicit reverse power transmission identification module to re-identify the implicit reverse power transmission status within the deconfirmation time window after outputting the closing interlocking command or the closing delay command. When the implicit reverse power supply state is not identified within the confirmation release time window, and the voltage holding state and the reverse support state no longer meet the time correlation condition, the interlocking verification unit outputs a closing verification command. When the verification result meets the preset closing conditions, the closing control module releases the closing lockout state or ends the closing delay state and outputs the closing permission command.

[0016] Furthermore, the closing control module includes a conservative control unit; The conservative control unit is used to mark the side to be closed as a state of pending confirmation of backfeeding when the implicit backfeeding identification module cannot determine whether the implicit backfeeding state exists. The inability to determine whether the implicit reverse power transmission state exists includes: the voltage data on the side to be closed and the data corresponding to the reverse support state do not meet the requirement of the same closing verification time window; the active power direction data of the associated outgoing line interval is inconsistent with the reverse support path direction; or valid reverse support characterization data of the associated transformer area has not been obtained. In the state of pending confirmation of reverse power supply, the conservative control unit prohibits the output of the closing permission command and outputs the closing delay command or the closing verification command.

[0017] Another object of the present invention is to provide a method for controlling the power flow reversal of a photovoltaic distribution area ring network box, comprising: Obtain the target ring network box's closing request information, switch position data, voltage data on the side to be closed, active power direction data of the associated outgoing line interval, and reverse support characterization data of the associated transformer area; Upon receiving the closing request information, the target connection interval, the side to be closed corresponding to the target connection interval, and the associated photovoltaic area that has a power supply relationship with the side to be closed are determined according to the switch position data and the preset ring network topology. Based on the switch position data and the preset ring network topology, determine whether an upstream power supply path has been formed on the side to be closed; Based on the active power direction data of the associated outgoing line interval and the reverse support characterization data of the associated photovoltaic area, it is determined whether the associated photovoltaic area has the state of outputting reverse power to the side to be closed via the distribution transformer, and this state is determined as the reverse support state. When the upstream power supply path is not formed on the side to be closed, it is determined whether the voltage holding state still exists on the side to be closed based on the voltage data of the side to be closed. When the voltage holding state and the reverse support state are within the same closing verification time window, it is determined that there is a hidden reverse power supply state formed by the reverse support of the associated photovoltaic area on the side to be closed; When the implicit reverse power transmission state is detected, a closing interlock command, a closing delay command, or a closing verification command is output to the target communication interval; when the implicit reverse power transmission state is not detected and the preset closing conditions are met, a closing permission command is output.

[0018] In summary, the present invention has the following beneficial effects: This invention, through the cooperation of a status data acquisition module, a closing object confirmation module, a power supply path judgment module, a reverse support judgment module, a hidden reverse power transmission identification module, and a closing control module, can determine the side to be closed and the associated photovoltaic area with which it has a power supply connection before closing the target interconnection interval, and determine whether the side to be closed forms an upper-level power supply path, thereby providing a clear object basis and topology judgment basis for the status verification before closing.

[0019] In the absence of an upstream power supply path on the side awaiting closure, this invention further combines the voltage holding status on the side awaiting closure, the active power direction data of the associated outgoing line interval, and the reverse support characterization data of the associated photovoltaic area to determine whether the associated photovoltaic area forms reverse support to the side awaiting closure via the distribution transformer. This is beneficial for identifying the implicit reverse power transmission state formed by the reverse support of the lower-level photovoltaic area.

[0020] This invention limits the voltage holding state and the reverse support state to the same closing verification time window for correlation judgment, which can reduce the risk of misjudgment caused by residual voltage, induced voltage, measurement error, short-term fluctuation of photovoltaic output or state misalignment, and improve the accuracy and reliability of implicit reverse power transmission state identification.

[0021] When a hidden reverse power feeding state is detected, this invention outputs a closing interlock command, a closing delay command, or a closing verification command to the target interconnection interval; when no hidden reverse power feeding state is detected and the preset closing conditions are met, it outputs a closing permission command. This enables hierarchical control of the interconnection interval closing action based on the pre-closing identification results, reducing the risks of cross-source closing, reverse power feeding superposition, fault section re-energization, or abnormal protection coordination in photovoltaic reverse support scenarios. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall architecture of the photovoltaic distribution area ring network box power flow reversal control system in this embodiment; Figure 2 This is a flowchart illustrating the power flow reversal control method for the photovoltaic distribution area ring network box in this embodiment. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings.

[0024] Example: This embodiment provides a power flow reversal control system for a photovoltaic distribution area ring network box, which is applied to a distribution area with distributed photovoltaic access. The distribution area is connected to a medium-voltage distribution line through a distribution transformer, and the incoming, outgoing and interconnection power supply control is realized through the target ring network box.

[0025] The target ring main unit includes at least one tie bay, at least one outgoing bay, and an incoming bay connected to the upstream power supply side. The tie bay is used to perform closing operations during power transfer, maintenance restoration, or power path adjustment; the outgoing bay is used to connect to the downstream distribution substation; and the incoming bay is used to connect to the upstream power supply line.

[0026] In this embodiment, the communication interval that receives the closing request is designated as the target communication interval. Before closing the target communication interval, its corresponding side to be closed needs to be determined. The side to be closed can be understood as the ring network busbar, outgoing branch, or line section that will be connected to or have its power restored after the target communication interval is closed.

[0027] An associated photovoltaic (PV) distribution area refers to a PV distribution area that has a power supply connection with the side awaiting closure. This associated PV distribution area can form an electrical connection with the side awaiting closure through corresponding outgoing line bays, distribution transformers, and distribution area power supply branches. When the PV output of the associated PV distribution area exceeds the local load, the power may be transmitted in reverse from the low-voltage distribution area side to the medium-voltage ring network box side via the distribution transformer, further affecting the voltage status of the side awaiting closure.

[0028] If no power supply path from the upstream power source is formed on the side to be closed before the target interconnection interval is closed, but a voltage holding phenomenon is still detected, then the voltage may not be formed by the conventional upstream power supply, but may be formed by the reverse support of the associated photovoltaic area.

[0029] This embodiment identifies whether there is a hidden reverse power transmission state on the side to be closed by collecting the switch position, voltage, active power direction and reverse support characterization data of the target ring network box and the associated photovoltaic area, and then controls the closing action of the target interconnection interval by blocking, delaying, verifying or permitting.

[0030] like Figure 1 As shown, the photovoltaic distribution area ring network box power flow reversal control system of this embodiment includes a status data acquisition module, a closing object confirmation module, a power supply path judgment module, a reverse support judgment module, a hidden reverse power transmission identification module, and a closing control module. The status data acquisition module is used to acquire the target ring network box's closing request information, switch position data, voltage data on the side to be closed, active power direction data of the associated outgoing line bay, and reverse support characterization data of the associated transformer area. This data is used to support topology confirmation, voltage status judgment, and reverse support status judgment before the target interconnection bay is closed.

[0031] The closing object confirmation module is connected to the status data acquisition module. When a closing request information is received, it is used to determine the target connection interval corresponding to this closing operation, the side to be closed corresponding to the target connection interval, and the associated photovoltaic area that has a power supply relationship with the side to be closed, based on the switch position data and the preset ring network topology.

[0032] The power supply path determination module is connected to the closing object confirmation module. It is used to determine whether an upstream power supply path from the upstream power source has been formed on the side to be closed, based on the switch position data and the preset ring network topology. This determination result is used to distinguish whether the voltage on the side to be closed can be formed by a conventional upstream power supply.

[0033] The reverse support judgment module is connected to the status data acquisition module. It is used to determine whether the associated photovoltaic area has the state of outputting reverse power to the side to be closed through the distribution transformer based on the active power direction data of the associated outgoing line interval and the reverse support characterization data of the associated transformer area, and to determine the state as the reverse support state.

[0034] The implicit reverse power transmission identification module is connected to the power supply path judgment module and the reverse support judgment module respectively. It is used to determine whether there is still a voltage holding state on the side to be closed when no upper-level power supply path is formed on the side to be closed, based on the voltage data of the side to be closed; and when the voltage holding state and the reverse support state are within the same closing verification time window, it is determined that there is an implicit reverse power transmission state formed by the reverse support of the associated photovoltaic area on the side to be closed.

[0035] The closing control module is connected to the implicit reverse power transmission identification module and is used to control the closing of the target communication interval based on the identification result of the implicit reverse power transmission status. When the implicit reverse power transmission status is identified, the closing control module outputs a closing interlock command, a closing delay command, or a closing verification command; when the implicit reverse power transmission status is not identified and the preset closing conditions are met, the closing control module outputs a closing permission command.

[0036] Through the above architecture, this embodiment can jointly judge the voltage holding phenomenon on the side to be closed, the reverse support status of the associated photovoltaic area, and the ring network topology before closing the target interconnection interval, avoiding making the closing judgment solely based on whether the side to be closed is energized, thereby reducing the risk of accidental closing under the condition of implicit back-feeding.

[0037] In this embodiment, the status data acquisition module is used to acquire status data related to the confirmation of the closing object, the judgment of the power supply path, the judgment of the reverse support, and the identification of the implicit reverse power transmission before the closing judgment is performed in the target communication interval.

[0038] The data acquired by the status data acquisition module includes the target ring network box's closing request information, switch position data, voltage data on the side to be closed, active power direction data of the associated outgoing line interval, and reverse support characterization data of the associated transformer area.

[0039] The closing request information is used to characterize the closing operation of the interconnection bay to be performed in the target ring network box. This closing request information can be generated by the distribution automation master station, the local control unit of the ring network box, the operation and maintenance control terminal, or a preset power restoration control process, and is used to trigger the closing object confirmation process.

[0040] Switch position data is used to characterize the open / closed status of incoming, outgoing, and tie-line sections in the target ring network box, as well as related sectionalizing switches. The closing target confirmation module and power supply path judgment module, based on the switch position data and in conjunction with the preset ring network topology, determine whether the target tie-line, the side to be closed, and whether the side to be closed forms an upstream power supply path.

[0041] Voltage data on the side awaiting closure is used to characterize the voltage status of the target interconnection bay corresponding to the side awaiting closure. The voltage data on the side awaiting closure may include at least one of the bus voltage, line-side voltage, or outgoing-side voltage on the side awaiting closure, and is used to determine whether there is a voltage holding state on the side awaiting closure when no upstream power supply path has been formed.

[0042] The active power direction data of the associated outgoing line bay is used to characterize the active power flow direction in the outgoing line bay corresponding to the associated photovoltaic area. The reverse support judgment module determines whether the candidate reverse power is directed to the side to be closed along the preset ring network topology based on this active power flow direction.

[0043] The associated photovoltaic (PV) distribution area reverse support characterization data is used to characterize whether the associated PV distribution area has the condition to output reverse power to the medium-voltage ring network box side. This data may include transformer power direction data, or it may include PV output data and load data of the associated PV distribution area within the same sampling time window.

[0044] In one implementation, the power direction data of the distribution transformer is used to determine whether power is directed from the low-voltage side to the medium-voltage ring network box side via the distribution transformer. In another implementation, the photovoltaic output data and load data of the transformer substation are used to determine whether there is net reverse power transmission from the associated photovoltaic substation.

[0045] The status data acquisition module can also acquire the sampling time information corresponding to each status data. The sampling time information is used to determine whether the voltage data on the side to be closed, the active power direction data of the associated outgoing line interval, and the reverse support characterization data of the associated transformer area are within the same closing verification time window.

[0046] Through the above-described state data acquisition process, this embodiment can provide a data foundation for identifying the voltage holding state on the side to be closed, the reverse support state of the associated photovoltaic area, and the implicit reverse power transmission state.

[0047] In this embodiment, the closing object confirmation module is used to determine the target communication interval, the side to be closed, and the associated photovoltaic area corresponding to this closing operation after receiving the closing request information.

[0048] The closing object confirmation module first parses the closing request information, determines the communication interval to be closed, and uses this communication interval as the target communication interval. The closing request information may include at least one of the following: communication interval number, closing operation source, request time, and operation object identifier.

[0049] After determining the target tie interval, the closing object confirmation module determines the electrical connection status on both sides of the target tie interval based on the switch position data of the target ring main unit and the preset ring network topology. The preset ring network topology is used to characterize the connection relationships between incoming line intervals, outgoing line intervals, tie intervals, busbar sections, and downstream distribution areas in the target ring main unit.

[0050] The closing target confirmation module further determines the side to be closed corresponding to the target interconnection bay based on the electrical connection status on both sides of the target interconnection bay. The side to be closed can be the bus section, line section, or outgoing branch that will be connected, restored to power, or integrated into operation after the target interconnection bay is closed.

[0051] After determining the side to be closed, the closing object confirmation module searches for lower-level transformer substations that have a power supply connection with the side to be closed along the preset ring network topology. If a lower-level transformer substation is connected to distributed photovoltaic power and can affect the voltage state of the side to be closed through the corresponding outgoing line bay, distribution transformer, or power supply branch, then the lower-level transformer substation is identified as the associated photovoltaic transformer substation.

[0052] Through the above-mentioned process of confirming the closing object, the control object, the side to be verified, and the range of photovoltaic areas that may form reverse support can be clearly identified in the subsequent judgment, thereby providing an object basis for power supply path judgment and hidden reverse power transmission identification.

[0053] In this embodiment, the power supply path determination module is used to determine whether a power supply path from the upstream power source has been formed on the side to be closed. This determination is based on switch position data and a preset ring network topology.

[0054] After determining the side to be closed, the power supply path determination module traces the path from the side to be closed to the upstream power supply along a preset ring network topology to identify whether there is a continuous conductive path between the side to be closed and the upstream power supply. The continuous conductive path refers to the path in which the incoming line bay, outgoing line bay, tie bay, or sectionalizing switch is in a closed state that can transmit electrical energy, and there are no disconnection points in the path caused by the position of the sectionalizing switch or the switch to be confirmed.

[0055] When a continuous conductive path exists between the side to be closed and the upstream power supply, the power supply path determination module determines that the side to be closed has formed an upstream power supply path. When there is no continuous conductive path between the side to be closed and the upstream power supply, or when there is a disconnection point in the path where the switch position needs to be confirmed, the power supply path determination module determines that the side to be closed has not formed an upstream power supply path.

[0056] If no upstream power supply path is formed on the side to be closed, and the voltage data on the side to be closed still indicates that there is a voltage holding phenomenon on that side, the power supply path judgment module sends the judgment result to the implicit reverse power transmission identification module to trigger subsequent voltage holding status judgment and implicit reverse power transmission identification.

[0057] In this embodiment, the implicit reverse power transmission identification module includes a voltage holding judgment unit. The voltage holding judgment unit is used to determine whether there is a voltage holding state on the side to be closed after the power supply path judgment module determines that no upper-level power supply path has been formed on the side to be closed.

[0058] The voltage holding judgment unit acquires the voltage data of the side to be closed and reads the voltage change status of the voltage data of the side to be closed within a preset holding judgment time period. The preset holding judgment time period can be preset according to the closing verification cycle, sampling cycle and on-site operation requirements of the target ring network box.

[0059] When the voltage data on the side to be closed is within the preset voltage holding range within the preset holding judgment time period, and the duration reaches the preset holding time, the voltage holding judgment unit further judges whether the voltage data on the side to be closed shows a trend of continuous decay to a state of loss of voltage.

[0060] If the voltage data on the side to be closed remains within the preset voltage holding range during the preset holding judgment time period, and the duration reaches the preset holding time, and does not show a trend of continuous decay to a state of voltage loss, then the voltage holding judgment unit determines that there is a voltage holding state on the side to be closed.

[0061] If the voltage data on the side to be closed is not within the preset voltage holding range, the duration does not reach the preset holding time, or shows a trend of continuous decay to a state of voltage loss, the voltage holding judgment unit will not determine the voltage state corresponding to the voltage data on the side to be closed as a voltage holding state.

[0062] Through the above judgment process, it is possible to identify the state in which the side to be closed still maintains voltage when no upstream power supply path has been formed, providing a basis for subsequent identification of implicit reverse power feeding status in conjunction with the reverse support status of the associated photovoltaic area. By combining the voltage holding range, holding duration, and whether it continues to decay to a state of loss of voltage for judgment, the stability of voltage holding status identification can be improved, and the interference of short-term residual voltage or decaying voltage on subsequent implicit reverse power feeding identification can be reduced.

[0063] In this embodiment, the reverse support determination module may include a transformer direction determination unit. The transformer direction determination unit is used to determine whether there is candidate reverse power in the associated photovoltaic power distribution area based on the transformer power direction data of the associated photovoltaic power distribution area.

[0064] The power direction data of the photovoltaic distribution area is used to characterize the active power flow direction on both sides of the distribution transformer. This data can be obtained from the distribution area's smart terminal, distribution transformer monitoring device, low-voltage side metering device, or distribution automation system.

[0065] The transformer direction determination unit reads the transformer power direction data within the same direction confirmation time window and determines whether the power flows from the low-voltage side of the associated photovoltaic area to the medium-voltage ring network box side via the distribution transformer. The direction confirmation time window can be preset according to the sampling period of the transformer power direction data, communication delay, and closing verification period.

[0066] When the power direction data of the distribution transformer indicates that the active power is directed from the low-voltage side to the medium-voltage ring network box side through the distribution transformer, the distribution transformer direction judgment unit determines that there is reverse power in the associated photovoltaic area and identifies the reverse power as a candidate reverse power.

[0067] The candidate reverse power is used to indicate the possibility that the associated photovoltaic area has the potential to output power to the medium-voltage ring network box. This candidate reverse power also needs to be checked for directional consistency by combining the active power direction data of the associated outgoing line bay and the preset ring network topology to determine whether it can affect the side to be closed along the reverse support path.

[0068] In this embodiment, the reverse support judgment module may include a net reverse transmission judgment unit. The net reverse transmission judgment unit is used to determine whether there is candidate net reverse transmission power in the associated photovoltaic power distribution area based on the photovoltaic output data and load data of the associated photovoltaic power distribution area within the same sampling time window.

[0069] The photovoltaic output data of the associated photovoltaic distribution area is used to characterize the active power output of distributed photovoltaic systems within that area at the current sampling time or within the sampling time window. The load data of the distribution area is used to characterize the active power of the electrical load within the corresponding sampling time or within the sampling time window. The above data can be obtained from the distribution area's intelligent terminal, photovoltaic grid-connected monitoring equipment, low-voltage side metering devices, or distribution automation systems.

[0070] In one implementation, the net backfeed determination unit determines the net backfeed power of the associated photovoltaic distribution area based on the difference between the photovoltaic output data and the load data of the distribution area.

[0071] in, This indicates the net reverse power of the associated photovoltaic power station area; This indicates the photovoltaic output of the associated photovoltaic distribution area; This indicates the load of the associated photovoltaic power station area.

[0072] When the net backfeed power is greater than zero, it indicates that the photovoltaic output of the associated photovoltaic area exceeds the local load, and it has the capacity to output surplus active power to external lines. To avoid misjudgment due to sampling errors, short-term fluctuations, or metering deviations, the net backfeed judgment unit can further introduce a preset backfeed margin to confirm the net backfeed power.

[0073] in, This indicates the preset backfeed margin, used to limit the net backfeed power to the minimum power amplitude that can be used as a candidate backfeed power.

[0074] When the photovoltaic output data of a distribution area is greater than the load data of the distribution area, and the difference between the two reaches the preset back-feed margin, the net back-feed judgment unit determines that there is a candidate net back-feed power in the associated photovoltaic distribution area, and uses the candidate net back-feed power as the candidate back-feed power.

[0075] In the specific judgment process, the net backfeed judgment unit can continuously acquire photovoltaic power output data and load data of the distribution area within the same sampling time window. When multiple sampling points meet the condition that the net backfeed power reaches the preset backfeed margin, or when the duration of meeting the condition reaches the preset confirmation time, the net backfeed judgment unit confirms that the candidate backfeed power is valid. This candidate backfeed power is used for subsequent directional consistency verification to determine whether it can affect the side to be closed corresponding to the target interconnection interval along the reverse support path.

[0076] In this embodiment, the reverse support judgment module includes a directional consistency verification unit, which is used to verify the power flow direction of the candidate reverse power to determine whether the candidate reverse power can affect the side to be closed along the preset ring network topology.

[0077] The directional consistency verification unit first determines the reverse support path from the associated photovoltaic area through the corresponding associated outgoing line bay to the side to be closed, based on the preset ring network topology. The reverse support path may include the electrical connection path between the associated photovoltaic area, the distribution transformer, the corresponding associated outgoing line bay, the bus section within the target ring network box, and the side to be closed.

[0078] After determining the reverse support path, the directional consistency verification unit acquires the active power direction data of the associated outgoing interval. This associated outgoing interval active power direction data characterizes the flow direction of active power at the corresponding outgoing interval. This flow direction can be determined based on the positive or negative direction of the active power in the outgoing interval, the power flow direction indicator, or the direction status output by the metering device.

[0079] The directional consistency verification unit compares the active power flow direction, represented by the active power flow direction data of the associated outgoing line bay, with the direction of the reverse support path. When the active power flow direction is consistent with the reverse support path direction, it indicates that the candidate reverse power can be transmitted from the associated photovoltaic area side along the corresponding outgoing line bay to the side to be closed. At this time, the directional consistency verification unit uses the candidate reverse power to determine that the associated photovoltaic area has a reverse support state.

[0080] When the active power flow direction is inconsistent with the reverse support path direction, or when the active power flow direction is in an unconfirmable state, the direction consistency verification unit will not use the candidate reverse power to determine the reverse support state. In cases where the direction cannot be confirmed, the closing control module can, in conjunction with subsequent conservative control processes, mark the side to be closed as being in a reverse power flow pending confirmation state and output a closing delay command or a closing verification command.

[0081] Through the above-mentioned directional consistency verification process, the candidate reverse power of the associated photovoltaic power distribution area can be matched with the actual topological direction of the side to be closed, providing a reverse support basis for subsequent identification of hidden reverse power transmission status.

[0082] In this embodiment, the implicit reverse power transmission identification module includes a time correlation judgment unit. The time correlation judgment unit is used to determine whether the voltage holding state of the side to be closed and the reverse support state of the associated photovoltaic area form a time correlation within the closing verification time window.

[0083] The time correlation judgment unit first determines the closing verification time window. The closing verification time window can be preset according to the closing verification cycle, data sampling cycle and communication delay of the target communication interval, and is used to limit the effective range of data used in this closing judgment.

[0084] Within the closing verification time window, the time correlation judgment unit determines the voltage holding interval corresponding to the voltage holding state, and the reverse support interval corresponding to the reverse support state. The voltage holding interval is used to characterize the start and end time when the voltage data on the side to be closed meets the voltage holding state; the reverse support interval is used to characterize the start and end time when the associated photovoltaic area meets the reverse support state.

[0085] In one implementation, the voltage holding interval is represented as:

[0086] in, Indicates the voltage holding range; Indicates the start time of the voltage holding state; Indicates the end time of the voltage holding state.

[0087] The reverse support range is represented as follows:

[0088] in, Indicates the reverse support range; Indicates the start time of the reverse support state; Indicates the end time of the reverse support state.

[0089] The time correlation judgment unit determines whether the voltage holding interval and the reverse support interval overlap. If the two intervals overlap, the overlap duration is further determined. The overlap duration can be determined according to the following relationship:

[0090] in, This indicates the overlap duration between the voltage holding interval and the reverse support interval; This indicates the earlier of the voltage holding state end time and the reverse support state end time. This indicates the later of the voltage holding state start time and the reverse support state start time.

[0091] When the overlap duration is greater than zero and the preset correlation duration is reached, the time correlation judgment unit determines that the voltage holding state and the reverse support state satisfy the time correlation condition:

[0092] in, This indicates the preset association duration. The preset association duration can be pre-set based on the field data sampling period, the closing judgment period, and the allowable state synchronization error.

[0093] When the voltage holding state and the reverse support state meet the time correlation condition, and the power supply path judgment module has determined that no upper-level power supply path has been formed on the side to be closed, the implicit reverse power transmission identification module determines that there is an implicit reverse power transmission state formed by the reverse support of the associated photovoltaic area on the side to be closed.

[0094] When the voltage holding interval and the reverse support interval do not overlap, or the overlap duration does not reach the preset association duration, the implicit reverse power transmission identification module does not determine the implicit reverse power transmission state based on the voltage holding state and the reverse support state.

[0095] Through the above time correlation judgment process, the voltage holding phenomenon on the side to be closed can be correlated with the reverse support state of the associated photovoltaic area in the time dimension, reducing misjudgments caused by state misalignment, sampling delay or short-term fluctuation.

[0096] In this embodiment, the implicit reverse power transmission identification module includes a non-reverse power transmission voltage exclusion unit. The non-reverse power transmission voltage exclusion unit is used to further determine whether the voltage holding state can be used as the identification basis for the implicit reverse power transmission state when there is a voltage holding state on the side to be closed.

[0097] The non-reverse voltage rejection unit acquires the voltage change status of the voltage data on the side to be closed within a preset rejection judgment time period. The preset rejection judgment time period can be pre-set according to the sampling period of the target ring network box, the closing verification period, and the residual voltage attenuation characteristics on site.

[0098] When the voltage data on the side awaiting closure continues to decrease within a preset exclusion judgment time period and falls below a preset undervoltage threshold, it indicates that the voltage on the side awaiting closure does not have a continuous support characteristic. If there is no reverse support state within the same closing verification time window, the non-reverse voltage exclusion unit determines the voltage holding state as a non-reverse voltage state.

[0099] When determining a non-reverse voltage state, the implicit reverse power transmission identification module does not use the voltage holding state to determine the implicit reverse power transmission state. In other words, this voltage change state is not involved in the time correlation judgment between the voltage holding state and the reverse support state.

[0100] If the voltage data on the side to be closed does not continuously drop below the preset undervoltage threshold, or if a reverse support state exists within the same closing verification time window, the non-reverse voltage exclusion unit will not exclude the voltage holding state, and the implicit reverse power transmission identification module will continue to determine whether an implicit reverse power transmission state exists based on the voltage holding state, the reverse support state, and the time correlation conditions.

[0101] By eliminating the non-reverse voltage state described above, the impact of residual voltage, induced voltage, or short-term voltage fluctuations on the identification of implicit reverse voltage states can be reduced, thereby improving the reliability of the state judgment before closing the circuit.

[0102] In this embodiment, the closing control module is used to control the closing action of the target communication bay based on the identification result of the implicit reverse power transmission identification module. When the implicit reverse power transmission identification module determines that there is an implicit reverse power transmission state on the side to be closed, the closing control module outputs a closing interlock command, a closing delay command, or a closing verification command to the target communication bay; Among them, the closing interlock command is used to prohibit the target interconnection interval from performing the closing operation; the closing delay command is used to suspend the closing operation of the target interconnection interval and wait for subsequent re-verification; the closing verification command is used to trigger the reconfirmation of the voltage status of the side to be closed, the reverse support status of the associated photovoltaic area, the active power direction of the associated outgoing interval, and the switch position status.

[0103] When the implicit reverse power transmission identification module fails to detect an implicit reverse power transmission state, the closing control module further determines whether the target communication interval meets the preset closing conditions. The preset closing conditions may include at least one of the following: the target communication interval is in an operable state, the relevant switch position is valid, there is no reverse power transmission pending confirmation state on the side to be closed, and the protection interlocking signal has not been activated.

[0104] When no hidden reverse power transmission is detected and the target interconnection interval meets the preset closing conditions, the closing control module outputs a closing permission command. The closing permission command is used to allow the target interconnection interval to perform a closing operation, or to send the closing permission result to the ring network box local control unit, distribution automation terminal, or distribution automation master station.

[0105] When no hidden reverse power supply is detected, but the preset closing conditions are not met, the closing control module does not output a closing permission command, and can output a closing verification command or a closing delay command according to the unmet conditions.

[0106] Through the above-described closing control logic, this embodiment can convert the implicit reverse power transmission status identification result into a clear closing control result before closing the target interconnection interval, thereby reducing the risk of direct closing when there is photovoltaic reverse support on the side to be closed.

[0107] In this embodiment, the closing control module includes a lockout verification unit. The lockout verification unit is used to verify the implicit reverse power supply status of the side to be closed after the closing control module outputs a closing lockout command or a closing delay command, and to determine whether to release the lockout or end the delay based on the verification result.

[0108] After outputting the closing interlock command or closing delay command, the interlock verification unit triggers the implicit backfeeding identification module to re-identify the implicit backfeeding status within the release confirmation time window. The release confirmation time window can be preset according to the closing verification cycle of the target ring network box, the photovoltaic power output fluctuation characteristics, the data sampling cycle, and the communication delay.

[0109] Within the confirmation period, the implicit reverse power transmission identification module reacquires or retrieves the voltage data of the side to be closed, the active power direction data of the associated outgoing line interval, and the reverse support characterization data of the associated transformer area, and re-determines whether there is a voltage holding state on the side to be closed, whether there is a reverse support state in the associated photovoltaic transformer area, and whether the two meet the time correlation conditions.

[0110] When no hidden reverse power supply status is detected within the confirmation period, and the voltage holding status and reverse support status no longer meet the time correlation conditions, the interlocking verification unit outputs a closing verification command. The closing verification command is used to trigger a reconfirmation of the switch position status of the target interconnection bay, the voltage status of the side to be closed, the status of the upstream power supply path, and the protection interlocking status.

[0111] When the verification result meets the preset closing conditions, the closing control module releases the closing lockout state or ends the closing delay state and outputs a closing permission command. If the verification result still does not meet the preset closing conditions, the closing control module continues to maintain the closing lockout state, or outputs a closing delay command and a closing verification command again.

[0112] Through the above-mentioned verification and release process after blocking, a subsequent recovery control process can be formed after the hidden reverse power transmission state is identified, so that the target communication bay can enter the closing state after the reverse power transmission risk is eliminated and the closing verification is passed.

[0113] In this embodiment, the closing control module includes a conservative control unit, which is used to perform conservative control on the closing operation of the target communication interval when the implicit backfeeding identification module cannot determine whether the implicit backfeeding state exists.

[0114] When the voltage data on the side awaiting closing does not meet the same closing verification time window requirement as the data corresponding to the reverse support state, the conservative control unit marks the side awaiting closing as a state of reverse power supply pending confirmation. This situation indicates that there is no effective time correspondence between the voltage holding state and the reverse support state, and the current data is insufficient to support the closing permission judgment.

[0115] When the active power direction data of the associated outgoing line bay is inconsistent with the reverse support path direction, or when the active power flow direction is in an unconfirmed state, the conservative control unit marks the side to be closed as having a reverse power transmission pending confirmation. This situation indicates that it has not yet been confirmed whether the candidate reverse power transmission can affect the side to be closed along the reverse support path.

[0116] When no valid reverse support characterization data for the associated transformer substation is obtained, the conservative control unit marks the side to be closed as pending confirmation of reverse power supply. Invalid reverse support characterization data for the associated transformer substation may include at least one of the following: missing data, sampling time exceeding the valid range, abnormal data quality identifier, or abnormal communication status.

[0117] In the state of pending confirmation of reverse power transmission, the conservative control unit is prohibited from outputting the closing permission command, and instead outputs the closing delay command or the closing verification command. The closing delay command is used to postpone the closing operation of the target interconnection bay, and the closing verification command is used to trigger the re-acquisition of voltage data on the side to be closed, active power direction data of the associated outgoing bay, and reverse support characterization data of the associated transformer area.

[0118] Through the above conservative control process, when the implicit reverse power transmission status cannot be confirmed or eliminated, the target communication interval can be prevented from directly entering the closing permission process, thereby improving the security of closing control.

[0119] This embodiment also provides a method for controlling the power flow reversal of a photovoltaic power distribution ring network box, which can be executed by the aforementioned photovoltaic power distribution ring network box power flow reversal control system.

[0120] like Figure 2 As shown, the method includes the following steps: S1. Obtain the target ring main unit's closing request information, switch position data, voltage data on the side to be closed, active power direction data of the associated outgoing line bay, and reverse support characterization data of the associated transformer area. The above data is used to support object confirmation, power supply path judgment, reverse support judgment, and implicit reverse power transmission identification before the target interconnection bay is closed.

[0121] S2. Upon receiving the closing request information, determine the target connection interval corresponding to this closing operation based on the switch position data and the preset ring network topology, and determine the side to be closed corresponding to the target connection interval; further, along the preset ring network topology, determine the associated photovoltaic area that has a power supply connection with the side to be closed.

[0122] S3. Based on the switch position data and the preset ring network topology, determine whether there is a continuous conductive path between the side to be closed and the upstream power supply. If there is no continuous conductive path between the side to be closed and the upstream power supply, or if there is a disconnection point in the path where the switch position needs to be confirmed, it is determined that the side to be closed has not formed an upstream power supply path.

[0123] S4. Based on the active power direction data of the associated outgoing line interval and the reverse support characterization data of the associated photovoltaic area, determine whether the associated photovoltaic area has the state of outputting reverse power to the side to be closed via the distribution transformer. If the associated photovoltaic area has candidate reverse power, and the active power flow direction corresponding to the candidate reverse power is consistent with the reverse support path direction, then it is determined that the associated photovoltaic area has a reverse support state.

[0124] S5. When no upstream power supply path is formed on the side to be closed, determine whether the side to be closed still has a voltage holding state based on the voltage data of the side to be closed. If the voltage data of the side to be closed is within the preset voltage holding range within the preset holding judgment time period, the duration reaches the preset holding time, and there is no trend of continuous decay to the state of loss of voltage, then it is determined that the side to be closed has a voltage holding state.

[0125] S6. Within the closing verification time window, determine the voltage holding interval corresponding to the voltage holding state and the reverse support interval corresponding to the reverse support state. When the voltage holding interval and the reverse support interval overlap, and the overlap duration reaches the preset correlation duration, it is determined that the voltage holding state and the reverse support state meet the time correlation condition. When no upstream power supply path is formed on the side to be closed, and the voltage holding state and the reverse support state meet the time correlation condition, it is determined that there is an implicit reverse power supply state formed by the reverse support of the associated photovoltaic area on the side to be closed.

[0126] S7. When a hidden reverse power transmission state is detected, a closing interlock command, a closing delay command, or a closing verification command is output to the target interconnection bay. If no hidden reverse power transmission state is detected and the preset closing conditions are met, a closing permission command is output. If the hidden reverse power transmission state cannot be confirmed, the side to be closed is marked as a reverse power transmission pending confirmation state, and a closing delay command or a closing verification command is output.

[0127] Taking a high-penetration photovoltaic (PV) distribution area in a 10kV distribution network as an example, the target ring main unit includes a first incoming line bay, a second incoming line bay, a first outgoing line bay, a second outgoing line bay, and a tie bay. The target ring main unit is connected to distribution area A through the first outgoing line bay and to distribution area B through the second outgoing line bay. Distribution area A has distributed PV power generation with an installed capacity of 800kW, a distribution transformer capacity of 1000kVA, a low-voltage side rated voltage of 0.4kV, and a medium-voltage side rated voltage of 10kV. Distribution area A is electrically connected to the target ring main unit's closing side through the distribution transformer and the first outgoing line bay.

[0128] Between 12:30 and 12:40 on a certain day, the sunlight conditions in transformer substation A were good, with the photovoltaic output remaining between 650kW and 720kW, and the local load between 280kW and 350kW. At this time, transformer substation A had the potential to output surplus active power to the medium-voltage side. The distribution transformer monitoring device detected that the direction of active power from the distribution transformer was from the low-voltage side to the medium-voltage side, and the active power direction data of the first outgoing line bay indicated that the active power flow was from the transformer substation side to the target ring network box side.

[0129] At 12:35:10, the distribution automation master station sends a request to the target ring network box to close the tie-line, requesting the restoration of power supply to the tie-line. The status data acquisition module acquires the closing request information, the switch position data of the target ring network box, the voltage data of the side to be closed, the active power direction data of the first outgoing line interval, and the reverse support characterization data of the A transformer area.

[0130] The closing target confirmation module determines the target interconnection interval corresponding to this closing operation based on the closing request information, and determines the side to be closed corresponding to the target interconnection interval based on the switch position data and the preset ring network topology. According to the preset ring network topology, the voltage state of the side to be closed can be affected by the distribution transformer, the first outgoing line interval, and the target ring network box bus section of area A. Therefore, the closing target confirmation module determines area A as the associated photovoltaic area.

[0131] The power supply path determination module traces the path based on switch position data and the preset ring network topology. At this point, one sectionalizing switch between the side to be closed and the upstream power supply is in the open position, and the tie switch in the other backup power supply path is not yet closed. Therefore, there is no continuous conductive path between the side to be closed and the upstream power supply. The power supply path determination module determines that no upstream power supply path has been formed on the side to be closed.

[0132] The implicit reverse power transmission identification module then reads the voltage data on the side to be closed. During the preset holding period from 12:35:10 to 12:35:20, the voltage on the side to be closed remained between 0.72 and 0.78 times the rated voltage, lasting for the preset holding time, and did not show a trend of continuous decay to a state of voltage loss. Based on this, the voltage holding judgment unit determines that a voltage holding state exists on the side to be closed.

[0133] The reverse support judgment module simultaneously judges the candidate reverse power for transformer substation A. In one judgment path, the transformer direction judgment unit reads the transformer power direction data, confirms that there is reverse power in transformer substation A flowing from the low-voltage side through the distribution transformer to the 10kV ring network box side, and identifies this reverse power as a candidate reverse power. In another judgment path, the net reverse power judgment unit reads the photovoltaic output data and substation load data of transformer substation A. For example, at 12:35:12, the photovoltaic output of transformer substation A is 690kW, and the substation load is 310kW, with a difference of 380kW, reaching the preset reverse power margin of 80kW. Therefore, the net reverse power judgment unit determines that there is candidate net reverse power in transformer substation A and identifies this candidate net reverse power as the candidate reverse power.

[0134] The directional consistency verification unit determines the reverse support path from transformer A, through the distribution transformer, the first outgoing line bay, and the target ring network bus section to the side to be closed, based on the preset ring network topology. Subsequently, the directional consistency verification unit compares the active power flow direction represented by the active power direction data of the first outgoing line bay with the direction of the reverse support path. Since the active power flow direction data of the first outgoing line bay represents an active power flow from transformer A to the side to be closed, the directional consistency verification unit determines that the active power flow direction is consistent with the reverse support path direction and uses the candidate reverse power to determine that transformer A has a reverse support state.

[0135] The time correlation judgment unit determines the voltage holding interval corresponding to the voltage holding state and the reverse support interval corresponding to the reverse support state within the closing verification time window. For example, the voltage holding interval is from 12:35:10 to 12:35:20, and the reverse support interval is from 12:35:08 to 12:35:22. The two intervals overlap, and the overlap duration reaches the preset correlation duration of 5 seconds. The time correlation judgment unit determines that the voltage holding state and the reverse support state meet the time correlation condition.

[0136] If no upstream power supply path is formed on the side to be closed, and the voltage holding state and reverse support state meet the time correlation condition, the implicit reverse power transmission identification module determines that there is an implicit reverse power transmission state formed by the reverse support of area A on the side to be closed. Based on this, the closing control module outputs a closing interlock command to the target interconnection interval and records the reasons for the interlock, including: no upstream power supply path is formed on the side to be closed, the voltage holding state exists on the side to be closed, the reverse support state exists in area A, and the two meet the time correlation condition.

[0137] In another operational phase, if cloud cover causes the photovoltaic output of transformer area A to drop to 260kW and the load to rise to 420kW after 12:42, and the power direction of the transformer changes from the medium-voltage side to the low-voltage side, and the active power flow direction of the first outgoing line bay no longer points to the side awaiting closing, then the interlocking verification unit will trigger re-identification within the release confirmation time window. If no hidden reverse power supply state is identified within the release confirmation time window, and the voltage holding state and reverse support state no longer meet the time correlation conditions, the interlocking verification unit will output a closing verification command.

[0138] During the closing verification process, the closing control module reconfirms that the target communication bay is in an operable state, the relevant switch position data is valid, there is no back-feeding pending confirmation state on the side to be closed, and the protection interlocking signal has not been activated. When the verification result meets the preset closing conditions, the closing control module releases the closing interlocking state and outputs a closing permission command.

[0139] If, during the verification process, the sampling time difference between the voltage data on the side to be closed and the reverse support characterization data of area A exceeds the allowable range of the closing verification time window, or if the active power direction data of the first outgoing line bay is in an unconfirmable state, the closing control module will mark the side to be closed as being in a state of reverse power transmission pending confirmation. In this state, the closing control module will prohibit the output of closing permission commands and will output closing delay commands or closing verification commands until data that meets the time and direction consistency requirements is reacquired.

[0140] In summary, this embodiment triggers the pre-closing verification of the target interconnection interval through the closing request, and determines the side to be closed and the associated photovoltaic area based on the switch position data and the preset ring network topology. In the case that no upstream power supply path is formed on the side to be closed, this embodiment further combines the voltage holding state of the side to be closed, the candidate reverse power of the associated photovoltaic area, the reverse support path direction, and the time correlation conditions to identify whether there is a hidden reverse power supply state formed by the reverse support of the associated photovoltaic area on the side to be closed.

[0141] Upon detecting a hidden backfeeding state, the closing control module outputs a closing interlock command, a closing delay command, or a closing verification command. When the hidden backfeeding state is resolved and preset closing conditions are met, a closing permission command is output. If the data timing, direction, or reverse support characterization status cannot be effectively confirmed, the side to be closed is marked as a backfeeding pending confirmation state, and conservative control is executed. This embodiment can perform state identification, risk interlocking, verification release, and conservative control on the closing operation of the target interconnection bay in scenarios where reverse support is possible in the photovoltaic area, reducing the risk of erroneous closing under the hidden backfeeding state on the side to be closed.

[0142] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A power flow reversal control system for a photovoltaic distribution ring network box, characterized in that, include: The status data acquisition module is used to acquire the target ring network box's closing request information, switch position data, voltage data on the side to be closed, active power direction data of the associated outgoing line interval, and reverse support characterization data of the associated transformer area; The closing object confirmation module is used to determine the target connection interval, the side to be closed corresponding to the target connection interval, and the associated photovoltaic area that has a power supply association with the side to be closed, based on the switch position data and the preset ring network topology when the closing request information is received. The power supply path determination module is used to determine whether an upstream power supply path is formed on the side to be closed, based on the switch position data and the preset ring network topology. The reverse support judgment module is used to determine whether the associated photovoltaic area has the state of outputting reverse power to the side to be closed through the distribution transformer based on the active power direction data of the associated outgoing line interval and the reverse support characterization data of the associated transformer area, and to determine the state as the reverse support state. The implicit reverse power transmission identification module is used to determine whether the voltage holding state still exists on the side to be closed when the upstream power supply path has not been formed on the side to be closed; it is also used to determine that there is an implicit reverse power transmission state formed by the reverse support of the associated photovoltaic area on the side to be closed when the voltage holding state and the reverse support state are in the same closing verification time window. The closing control module is used to output a closing interlock command, a closing delay command, or a closing verification command to the target communication interval when the implicit reverse power transmission state is detected; it is also used to output a closing permission command when the implicit reverse power transmission state is not detected and the preset closing conditions are met.

2. The photovoltaic distribution ring network box power flow reversal control system according to claim 1, characterized in that, The implicit reverse power transmission identification module includes a voltage holding judgment unit. The voltage holding judgment unit is used to obtain the voltage change status of the voltage data of the side to be closed within a preset holding judgment time period when the power supply path judgment module determines that the upper-level power supply path has not been formed on the side to be closed. When the voltage data of the side to be closed is within a preset voltage holding range within the preset holding judgment time period, the duration reaches the preset holding time, and there is no trend of continuous decay to the state of voltage loss, it is determined that the voltage holding state exists on the side to be closed.

3. The photovoltaic distribution ring network box power flow reversal control system according to claim 1, characterized in that, The associated photovoltaic distribution area reverse support characterization data includes the distribution transformer power direction data of the associated photovoltaic distribution area; The reverse support judgment module includes a transformer direction judgment unit, which is used to determine whether there is reverse power from the low-voltage side to the medium-voltage ring network box side in the associated photovoltaic area within the same direction confirmation time window based on the transformer power direction data. When the backfeeding power exists, the backfeeding power is determined as a candidate backfeeding power.

4. The photovoltaic distribution area ring network box power flow reversal control system according to claim 1, characterized in that, The associated photovoltaic distribution area reverse support characterization data includes the photovoltaic output data and load data of the associated photovoltaic distribution area within the same sampling time window; The reverse support judgment module includes a net reverse transmission judgment unit, which is used to determine the net reverse transmission power of the associated photovoltaic power distribution area based on the photovoltaic power output data and the load data of the power distribution area. When the photovoltaic output data of the transformer area is greater than the load data of the transformer area, and the difference between the two reaches a preset back-feed margin, it is determined that there is a candidate net back-feed power in the associated photovoltaic transformer area, and the candidate net back-feed power is used as the candidate back-feed power.

5. The photovoltaic distribution area ring network box power flow reversal control system according to claim 3 or 4, characterized in that, The reverse support judgment module includes a direction consistency verification unit; The directional consistency verification unit is used to determine the reverse support path from the associated photovoltaic area through the corresponding associated outgoing line interval to the side to be closed, based on the preset ring network topology. It is also used to compare the active power flow direction represented by the active power direction data of the associated outgoing line interval with the direction of the reverse support path; When the active power flow direction is consistent with the direction of the reverse support path, the candidate reverse power is used to determine whether the associated photovoltaic area has the reverse support state.

6. The photovoltaic distribution ring network box power flow reversal control system according to claim 1, characterized in that, The implicit reverse power transmission identification module includes a time correlation judgment unit; The time correlation judgment unit is used to determine the voltage holding interval corresponding to the voltage holding state and the reverse support interval corresponding to the reverse support state within the closing verification time window. When the voltage holding interval and the reverse support interval overlap within the closing verification time window, and the overlap duration reaches the preset association duration, it is determined that the voltage holding state and the reverse support state satisfy the time association condition.

7. The photovoltaic distribution ring network box power flow reversal control system according to claim 1, characterized in that, The implicit reverse power transmission identification module includes a non-reverse voltage exclusion unit; The non-reverse voltage exclusion unit is used to acquire the voltage change status of the voltage data on the side to be closed within a preset exclusion judgment time period when the voltage holding state exists on the side to be closed. When the voltage data on the side to be closed continues to decrease and falls below the preset undervoltage threshold during the preset exclusion judgment time period, and there is no reverse support state within the same closing verification time window, the voltage holding state is determined to be a non-reverse voltage state. When determining the non-reverse voltage state, the voltage holding state is not used to determine the implicit reverse voltage state.

8. The photovoltaic distribution ring network box power flow reversal control system according to claim 6, characterized in that, The closing control module includes a lockout verification unit; The interlocking verification unit is used to trigger the implicit reverse power transmission identification module to re-identify the implicit reverse power transmission status within the deconfirmation time window after outputting the closing interlocking command or the closing delay command. When the implicit reverse power supply state is not identified within the confirmation release time window, and the voltage holding state and the reverse support state no longer meet the time correlation condition, the interlocking verification unit outputs a closing verification command. When the verification result meets the preset closing conditions, the closing control module releases the closing lockout state or ends the closing delay state and outputs the closing permission command.

9. The photovoltaic distribution ring network box power flow reversal control system according to claim 5, characterized in that, The closing control module includes a conservative control unit; The conservative control unit is used to mark the side to be closed as a state of pending confirmation of backfeeding when the implicit backfeeding identification module cannot determine whether the implicit backfeeding state exists. The inability to determine whether the implicit reverse power transmission state exists includes: the voltage data on the side to be closed and the data corresponding to the reverse support state do not meet the requirement of the same closing verification time window; the active power direction data of the associated outgoing line interval is inconsistent with the reverse support path direction; or valid reverse support characterization data of the associated transformer area has not been obtained. In the state of pending confirmation of reverse power supply, the conservative control unit prohibits the output of the closing permission command and outputs the closing delay command or the closing verification command.

10. A method for controlling power flow reversal in a photovoltaic distribution area ring network box, characterized in that, include: Obtain the target ring network box's closing request information, switch position data, voltage data on the side to be closed, active power direction data of the associated outgoing line interval, and reverse support characterization data of the associated transformer area; Upon receiving the closing request information, the target connection interval, the side to be closed corresponding to the target connection interval, and the associated photovoltaic area that has a power supply relationship with the side to be closed are determined according to the switch position data and the preset ring network topology. Based on the switch position data and the preset ring network topology, determine whether an upstream power supply path has been formed on the side to be closed; Based on the active power direction data of the associated outgoing line interval and the reverse support characterization data of the associated photovoltaic area, it is determined whether the associated photovoltaic area has the state of outputting reverse power to the side to be closed via the distribution transformer, and this state is determined as the reverse support state. When the upstream power supply path is not formed on the side to be closed, it is determined whether the voltage holding state still exists on the side to be closed based on the voltage data of the side to be closed. When the voltage holding state and the reverse support state are within the same closing verification time window, it is determined that there is a hidden reverse power supply state formed by the reverse support of the associated photovoltaic area on the side to be closed; When the implicit reverse power transmission state is detected, a closing interlock command, a closing delay command, or a closing verification command is output to the target communication interval; when the implicit reverse power transmission state is not detected and the preset closing conditions are met, a closing permission command is output.

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