A method and system for controlling automatic switching of a single-section busbar power failure with superconducting cable access

Abstract

This invention provides a method for automatic backup power transfer control of a single busbar section connected by a superconducting cable in a substation with a multi-segment power grid structure. The method includes: acquiring the de-energized busbar and its adjacent non-de-energized busbars; if the acquired non-de-energized busbar is only a single non-de-energized busbar adjacent to the de-energized busbar, and the incoming line of this single non-de-energized busbar is not the connected superconducting cable, calculating the load margin of the single non-de-energized busbar based on the pre-set incoming line capacity and load power of the corresponding single non-de-energized busbar; and after determining that the load margin of the single non-de-energized busbar is greater than or equal to the pre-set load power before the de-energized busbar lost power, directly selecting the single non-de-energized busbar for backup power transfer to restore power to the de-energized busbar. Implementing this invention allows for the rational selection of backup power sources and avoids overload load shedding, improving power supply reliability and continuity.

Description

Technical Field

[0001] The invention relates to the technical field of automatic switching of backup power supply of an electric power system, and in particular to a method and system for controlling automatic switching of backup power supply of a single-section busbar connected with a superconducting cable. Background Art

[0002] Different from the typical single busbar with two sections, after the superconducting cable access adopts a multi-segment structure, the busbar power failure fault situations are diverse, making the backup control more complicated.

[0003] In the case of a single-section busbar power failure, the backup power supply for multiple sections of the busbar does not involve the issue of backup power supply. Therefore, in addition to preventing the power failure busbar from simultaneously switching to the live buses on both sides to form an electromagnetic ring network, the backup power supply should be reasonably selected based on the load capacity of the power failure busbar section and the capacity margin of the backup power supply. At the same time, it is also necessary to avoid overload shedding to improve the power restoration rate.

[0004] However, the existing automatic backup control method is suitable for power grid scenarios with complex multi-segment busbar wiring, but lacks the power grid scenario with multi-segment ring wiring connected by superconducting cables. Therefore, there is an urgent need for a single-segment busbar power failure automatic backup control method with superconducting cables connected, which can reasonably select the backup power source, avoid overload and load shedding, and improve power supply reliability and continuity. Summary of the invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a single-section busbar power failure automatic switching control method and system connected to a superconducting cable, which can reasonably select the backup power supply, avoid the occurrence of overload and load shedding, and improve the power supply reliability and continuity.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a method for controlling a single-segment busbar power failure backup automatic switching connected to a superconducting cable, which is used in a power grid with a multi-segment structure where a substation busbar is connected to a superconducting cable. The method comprises the following steps:

[0007] Obtain the de-energized busbar and the non-de-energized busbars on its adjacent side;

[0008] If the acquired non-de-energized bus is only a single non-de-energized bus on one side adjacent to the de-energized bus, and the incoming line of the single non-de-energized bus is not a connected superconducting cable, the load margin of the single non-de-energized bus is calculated according to the incoming line capacity and load power pre-set for the single non-de-energized bus, and after it is determined that the load margin of the single non-de-energized bus is greater than or equal to the load power pre-set before the de-energized bus loses power, the single non-de-energized bus is selected for direct standby operation to restore power supply to the de-energized bus.

[0009] Wherein, the method further comprises:

[0010] If the acquired non-de-energized busbars are two non-de-energized busbars on both sides of the de-energized busbar, and the incoming line of one of the non-de-energized busbars is not a connected superconducting cable, and the incoming line of the other non-de-energized busbar is a connected superconducting cable, the load margin of the non-de-energized busbar not connected to the superconducting cable is calculated according to the pre-set incoming line capacity and load power of the corresponding non-de-energized busbar not connected to the superconducting cable, and after it is determined that the load margin of the non-de-energized busbar not connected to the superconducting cable is greater than or equal to the pre-set load power before the de-energized busbar loses power, the non-de-energized busbar not connected to the superconducting cable is selected for direct standby, so as to restore power supply to the de-energized busbar.

[0011] Wherein, the method further comprises:

[0012] If the acquired non-de-energized busbars are two non-de-energized busbars on both sides of the de-energized busbar, and the incoming lines of the two non-de-energized busbars are not connected superconducting cables, the load margins of the two non-de-energized busbars are calculated according to the pre-set incoming line capacities and load powers of the two corresponding non-de-energized busbars, and after it is determined that the load margin of at least one of the two non-de-energized busbars is greater than or equal to the pre-set load power of the de-energized busbar before power is lost, the direct standby with the largest load margin among the two non-de-energized busbars is selected to restore power supply to the de-energized busbar.

[0013] Wherein, the method further comprises:

[0014] If it is determined that the load margins of the two non-delivered buses are both less than the load power preset before the delivered bus loses power, and at least one of the two non-delivered buses shares the same incoming line with a corresponding non-delivered bus other than the two non-delivered buses, one of the shared incoming lines is selected, and the load of the non-delivered bus that is not adjacent to the delivered bus is transferred, so that the load margin of the non-delivered bus corresponding to the shared incoming line among the two non-delivered buses is greater than or equal to the load power preset before the delivered bus loses power, and the non-delivered bus corresponding to the shared incoming line among the two non-delivered buses is selected for standby, so as to restore power supply to the delivered bus; or

[0015] Take all the shared incoming lines and transfer the loads of the buses that are not adjacent to the de-energized busbar, so that the load margins of the two buses are greater than or equal to the load power pre-set before the de-energized busbar loses power. Then, any one of the two buses can be selected for standby to restore power to the de-energized busbar.

[0016] Wherein, the method further comprises:

[0017] If all the shared incoming lines are taken, and the loads of the buses that are not adjacent to the de-energized busbar in all the taken incoming lines are all transferred, and the load margins of the two buses that are not de-energized are still less than the load power preset before the de-energized busbar loses power, the overload rate is calculated according to the load power preset before the de-energized busbar loses power and the incoming line capacity and load power of the bus that is not de-energized with the largest load power among the two buses that are not de-energized, and the overload rate is compared with the preset overload rate, and further according to the comparison result, the corresponding load switching mode is selected to cut off the overload load when the two buses that are not de-energized are simultaneously put into standby power supply to the de-energized busbar; wherein, the load switching mode is a load shedding mode after standby power supply or a combination of pre-cut load and load shedding mode after standby power supply.

[0018] Wherein, the method further comprises:

[0019] By formula Calculate the overload rate η; where L i is the load power pre-set before the de-energized bus loses power; ΔS is the load margin of the un-de-energized bus with the largest load power among the two un-de-energized buses, and ΔS = S N -L N ; S N L is the incoming line capacity of the busbar with the largest load power among the two buses that have not lost power; N The preset load power of the busbar with the largest load power among the two buses with power failure;

[0020] If the overload rate η(i) ≤ the preset overload rate η set , then select the load shedding mode after standby switching on to cut off the overload when the two buses that have not lost power are switched on to the power-lost bus at the same time;

[0021] If the overload rate η(i)> the preset overload rate η set , then the combined pre-cut load and standby load shedding method is selected to cut off the overload when the two buses that have not lost power are simultaneously backed up to the power-lost bus; where the pre-cut load is ΔL = (L i -ΔS)-η set S N .

[0022] The embodiment of the present invention further provides a single-section busbar power failure automatic switching control system connected to a superconducting cable, which is used in a power grid with a multi-segment structure where a substation busbar is connected to a superconducting cable, and includes:

[0023] A bus acquisition unit, used to acquire the de-energized bus and the non-de-energized bus on its adjacent side;

[0024] The first standby control unit is used for calculating the load margin of the single non-powered bus according to the pre-set incoming line capacity and load power corresponding to the single non-powered bus, if the acquired non-powered bus is only a single non-powered bus on one side adjacent to the power-lost bus, and the incoming line of the single non-powered bus is not a connected superconducting cable, and after determining that the load margin of the single non-powered bus is greater than or equal to the pre-set load power before the power-lost bus loses power, selecting the single non-powered bus for direct standby, so as to restore power supply to the power-lost bus.

[0025] Among them, it also includes:

[0026] The second standby control unit is used for, if the acquired non-power-off busbars are two non-power-off busbars on both sides of the power-off busbar, and the incoming line of one of the non-power-off busbars is not a connected superconducting cable, and the incoming line of the other non-power-off busbar is a connected superconducting cable, calculating the load margin of the non-power-off busbar not connected to the superconducting cable according to the pre-set incoming line capacity and load power of the corresponding non-power-off busbar not connected to the superconducting cable, and after determining that the load margin of the non-power-off busbar not connected to the superconducting cable is greater than or equal to the pre-set load power before the power-off busbar loses power, selecting the non-power-off busbar not connected to the superconducting cable for direct standby, so as to realize the restoration of power supply to the power-off busbar.

[0027] Among them, it also includes:

[0028] The third standby control unit is used for calculating the load margin of the two buses that have not lost power according to the pre-set incoming line capacity and load power of the two corresponding buses that have not lost power, if the acquired non-power-loss busbars are two non-power-loss busbars on both sides of the power-loss busbar, and the incoming lines of the two buses that have not lost power are not the connected superconducting cables, and after it is determined that the load margin of at least one of the two buses that have not lost power is greater than or equal to the load power pre-set before the power-loss busbar loses power, selecting the direct standby with the largest load margin among the two buses that have not lost power to realize the restoration of power supply to the power-loss busbar.

[0029] Among them, it also includes:

[0030] The fourth standby control unit is used for taking one of the shared incoming lines, and transferring the load of the non-powered bus that is not adjacent to the power-lost bus in the taken incoming line, if it is determined that the load margins of the two non-powered buses are both less than the load power preset before the power-lost bus loses power, and at least one of the two non-powered buses shares the same incoming line with a corresponding non-powered bus other than the two non-powered buses, so that the load margin of the non-powered bus that corresponds to the shared taken incoming line among the two non-powered buses is greater than or equal to the load power preset before the power-lost bus loses power, and then selecting the non-powered bus that corresponds to the shared taken incoming line among the two non-powered buses for standby, so as to restore power supply to the power-lost bus; or

[0031] Take all the shared incoming lines and transfer the loads of the buses that are not adjacent to the de-energized busbar, so that the load margins of the two buses are greater than or equal to the load power pre-set before the de-energized busbar loses power. Then, any one of the two buses can be selected for standby to restore power to the de-energized busbar.

[0032] Implementing the embodiments of the present invention has the following beneficial effects:

[0033] The present invention is applicable to a multi-segmented power grid in which a substation bus is connected to a superconducting cable. The present invention comprehensively utilizes whether the incoming line of the non-de-energized bus is connected to the superconducting cable and whether the load margin of the non-de-energized bus is greater than or equal to the load power of the de-energized bus before power failure, so as to reasonably select the backup power supply between the sections, avoid the occurrence of overload load shedding, and improve the reliability and continuity of power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0035] Figure 1 A flow chart of a method for controlling a single-section busbar power failure backup automatic switching connected to a superconducting cable provided by an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of a structure of a power grid with a multi-segment structure in which a substation bus is connected to a superconducting cable in a method for controlling a single-segment bus failure backup provided by an embodiment of the present invention;

[0037] Figure 3 for Figure 2 Application scenario diagram of the local structure;

[0038] Figure 4 for Figure 3 The control logic diagram of standby automatic switching when the single bus loses power;

[0039] Figure 5 A schematic diagram of a single-section busbar power failure automatic switching control structure with superconducting cable access is provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] like Figure 1 As shown in the figure, a method for controlling a single-segment busbar failure backup automatic switching connected to a superconducting cable is provided in an embodiment of the present invention, which is used in a power grid with a multi-segment structure where a substation busbar is connected to a superconducting cable (see Figure 2 The method comprises the following steps:

[0042] Step S1, obtaining a de-energized busbar and a non-de-energized busbar on its adjacent side;

[0043] The specific process is as follows: first, the voltage of each bus segment, the current of each incoming line and the load of each bus are calculated through real-time sampling of the bus voltage transformer and the bus incoming current transformer, and the calculated values ​​are stored; the on-off status of the switches QF01~QF0n and QF12~QFn(n+1) are collected; the on-off status of the incoming line switches set for each bus and the on-off status of the bus-coupler sectional switches connected to the adjacent bus are recorded. According to the instructions, the buses are numbered from left to right as 1M, 2M, ..., iM, (i+1)M, ..., nM, the iM incoming line switch is numbered as QF0i, and the bus-coupler sectional switch between iM and (i+1)M is numbered as QFi(i+1).

[0044] It should be noted that before step S1, the following steps are also included: when the incoming line switches provided for each bus are closed and the bus-connecting section switches connected to each bus are disconnected, the load of each bus is obtained as the preset load power of each bus and the preset incoming line capacity of the incoming line connected to each bus is obtained.

[0045] In one embodiment, the bus voltage U(i) of iM is recorded and stored in the array {U(k)}; the incoming line current I(i) of iM is recorded and stored in the array {I(k)}; the load power of iM is recorded Stored in array {L(k)}; record the incoming line capacity of each branch (ie, the preset power supply capacity of the substation) as a preset value and store it in array {S(i)}.

[0046] Detect the on / off status of all incoming line switches and record them in the array {QF0(k)}. If the iM incoming line switch QF0i is disconnected, QF0(i)=0; otherwise, QF0(i)=1; detect the on / off status of all busbar section switches and record them in the array {QF(k)}. If the busbar section switch QFi(i+1) between iM and (i+1)M is disconnected, QF(i)=0; otherwise, QF(i)=1.

[0047] At the same time, the following arrays are set to store the process signals of the standby automatic selection: bus power failure flag array {M(k)}, element M(k)=1 indicates that the iM bus is powered off; load margin array {ΔS(k)}, element ΔS(i) records the load margin of the iM bus.

[0048] Secondly, traverse the voltages of all busbars and their corresponding incoming line currents. Identify all busbars with voltages lower than a preset voltage threshold and incoming line currents lower than a preset current threshold as de-energized busbars, and identify all other remaining busbars except the de-energized busbars as non-de-energized busbars. Therefore, it is possible to traverse and obtain the single-segment de-energized busbar iM and a non-de-energized busbar (i - 1)M or (i + 1)M on its adjacent side; or obtain two non-de-energized busbars (i - 1)M and (i + 1)M.

[0049] For example, compare U(i) with the voltage threshold U set , I(i) with the current threshold I set . If U(i) < U set and I(i) < I set , then determine that the busbar iM is a de-energized busbar and set the busbar de-energization flag word M(i) = 1; otherwise, determine that the busbar iM is a non-de-energized busbar. If all M(i) = 0, there is no de-energized busbar, and the detection ends. Among them, U set and I set are pre-given setting values, and the typical values can be taken as 0.1U N and 0.04I N respectively.

[0050] Step S2: If the only non-de-energized busbar obtained is a single non-de-energized busbar on the adjacent side of the de-energized busbar, and the incoming line of this single non-de-energized busbar is not a connected superconducting cable, calculate the load margin of this single non-de-energized busbar according to the preset incoming line capacity and load power corresponding to this single non-de-energized busbar. After determining that the load margin of this single non-de-energized busbar is greater than or equal to the preset load power of the de-energized busbar before power loss, select this single non-de-energized busbar for direct standby switching to restore power supply to the de-energized busbar.

[0051] The specific process is as follows. When there is only one non-de-energized busbar (i + 1)M on the adjacent side of the single-segment de-energized busbar iM, and the incoming line of this single non-de-energized busbar (i + 1)M is not a connected superconducting cable, calculate the load margin of this single non-de-energized busbar (i + 1)M as ΔS(i + 1) = S(i + 1) - L(i + 1); where S(i + 1) is the preset incoming line capacity of this single non-de-energized busbar (i + 1)M, and L(i + 1) is the preset load power of this single non-de-energized busbar (i + 1)M.

[0052] When ΔS(i + 1) ≥ L(i), then this single non-de-energized busbar (i + 1)M is directly used for standby switching to restore power supply to the de-energized busbar iM; where L(i) is the preset load power of the de-energized busbar iM. It can be understood that if the incoming line of the non-de-energized busbar (i + 1)M is a superconducting cable or the load margin ΔS(i + 1) < L(i), standby switching cannot be performed, and power supply to the de-energized busbar iM cannot be restored.

[0053] In the embodiment of the present invention, if there are backup power supplies on both sides of the power-off bus iM, that is, there are two non-power-off buses (i-1)M and (i+1)M, it is necessary to determine whether the two non-power-off buses are connected to superconducting cables; if there is one, when the load margin of the non-power-off bus that is not connected to the superconducting cable is greater than or equal to the preset load power L(i) of the power-off bus iM, the non-power-off bus that is not connected to the superconducting cable is selected as the backup power supply for backup. It should be noted that if the two non-power-off buses (i-1)M and (i+1)M both have superconducting cables, they cannot be backed up, and the power supply of the power-off bus iM cannot be restored.

[0054] Therefore, if the acquired non-power-off busbars are two non-power-off busbars on both sides of the power-off busbar, and the incoming line of one of the non-power-off busbars is not a connected superconducting cable, and the incoming line of the other non-power-off busbar is a connected superconducting cable, the load margin of the non-power-off busbar that is not connected to the superconducting cable is calculated according to the pre-set incoming line capacity and load power of the corresponding non-power-off busbar that is not connected to the superconducting cable, and after it is determined that the load margin of the non-power-off busbar that is not connected to the superconducting cable is greater than or equal to the pre-set load power before the power-off busbar loses power, the non-power-off busbar that is not connected to the superconducting cable is selected for direct standby, so as to restore power supply to the power-off busbar.

[0055] The specific process is as follows: when there are two non-de-energized busbars (i-1)M and (i+1)M adjacent to the non-de-energized single-section busbar iM, and the incoming line of the non-de-energized busbar (i-1)M is not a connected superconducting cable, but the incoming line of the non-de-energized busbar (i+1)M is a connected superconducting cable, the non-de-energized busbar (i+1)M connected to the superconducting cable is discarded, and the load margin ΔS(i-1)=S(i-1)-L(i-1) of the non-de-energized busbar (i-1)M is calculated; wherein S(i-1) is the preset incoming line capacity of the non-de-energized busbar (i-1)M; and L(i-1) is the preset load power of the non-de-energized busbar (i-1)M.

[0056] When ΔS(i-1)≥L(i), the bus (i-1)M that has not lost power is directly put into standby mode to restore power supply to the lost bus iM.

[0057] In an embodiment of the present invention, if there are backup power supplies on both sides of the power-lost bus iM, that is, there are two non-power-lost buses (i-1)M and (i+1)M, it is necessary to determine whether the two non-power-lost buses are connected to superconducting cables; if neither is the case, when it is determined that the load margins of the two non-power-lost buses (i-1)M and (i+1)M are both greater than or equal to the preset load power L(i) of the power-lost bus iM, the non-power-lost bus with the largest load margin can be selected as the backup power supply for backup.

[0058] Therefore, if the acquired non-de-energized busbars are two non-de-energized busbars on both sides of the de-energized busbar, and the incoming lines of these two non-de-energized busbars are not connected superconducting cables, the load margins of these two non-de-energized busbars are calculated according to the pre-set incoming line capacities and load powers of the two corresponding non-de-energized busbars, and after it is determined that the load margin of at least one of the two non-de-energized busbars is greater than or equal to the pre-set load power of the de-energized busbar before power is lost, the direct standby with the largest load margin among the two non-de-energized busbars is selected to restore power supply to the de-energized busbar.

[0059] The specific process is that when there are two non-de-energized busbars (i-1)M and (i+1)M adjacent to the de-energized single-section busbar iM, and the incoming lines of these two non-de-energized busbars (i-1)M and (i+1)M are not connected superconducting cables, the load margins ΔS(i-1)=S(i-1)-L(i-1) and ΔS(i+1)=S(i+1)-L(i+1) of the non-de-energized busbars (i-1)M and (i+1)M are calculated respectively.

[0060] When ΔS(i-1)≥L(i), ΔS(i+1)≥L(i) and ΔS(i+1)>ΔS(i-1), the bus (i+1)M that has not lost power is directly put into standby mode to restore power supply to the lost bus iM; conversely, when ΔS(i-1)≥L(i), ΔS(i+1)≥L(i) and ΔS(i+1)<ΔS(i-1), the bus (i-1)M that has not lost power is directly put into standby mode to restore power supply to the lost bus iM.

[0061] In an embodiment of the present invention, if there are backup power supplies on both sides of the power-off bus iM, that is, there are two non-power-off buses (i-1)M and (i+1)M, and these two non-power-off buses (i-1)M and (i+1)M are not connected to superconducting cables, but the load margins of these two non-power-off buses do not meet the requirements, it is necessary to give priority to whether there is a load balancing function based on the connection structure of the two non-power-off buses (i-1)M and (i+1)M, increase the load margin of the backup power supply, and try to avoid the risk of load shedding.

[0062] Therefore, if it is determined that the load margins of the two non-power-lost buses are both less than the load power preset before the power-lost bus loses power, and at least one of the two non-power-lost buses shares the same incoming line with a corresponding non-power-lost bus other than the two non-power-lost buses, one of the shared incoming lines is taken, and the load of the non-power-lost bus that is not adjacent to the power-lost bus is transferred, so that the load margin of the non-power-lost bus corresponding to the shared incoming line among the two non-power-lost buses is greater than or equal to the load power preset before the power-lost bus loses power, and then the non-power-lost bus corresponding to the shared incoming line among the two non-power-lost buses is selected for standby, so as to restore power supply to the power-lost bus; or

[0063] Take all of the common incoming lines, and transfer the loads of the non-powered-off busbars among all the taken incoming lines that are not adjacent to the powered-off busbar. After the load margins of these two non-powered-off busbars are both greater than or equal to the pre-set load power before the powered-off busbar loses power, any one of these two non-powered-off busbars can be selected for backup power supply switching to restore power supply to the powered-off busbar.

[0064] The specific process is as follows. When the load margins of these two non-powered-off busbars (i - 1)M and (i + 1)M are both less than the pre-set load power L(i) before the powered-off busbar iM loses power, that is, ΔS(i - 1) < L(i) and ΔS(i + 1) < L(i), determine whether at least one of these two non-powered-off busbars (i - 1)M and (i + 1)M shares the same incoming line with a corresponding non-powered-off busbar other than these two non-powered-off busbars (i - 1)M and (i + 1)M. For example, for the busbar section connected to a low-voltage side branch-type transformer, the non-powered-off busbar (i + 1)M and another non-powered-off busbar (i + 2)M share the same incoming line. Another example, for the busbar section connected to a low-voltage side branch-type transformer, the non-powered-off busbar (i + 1)M and another non-powered-off busbar (i + 2)M share the same incoming line, and the non-powered-off busbar (i - 1)M and another non-powered-off busbar (i - 2)M share the same incoming line.

[0065] (1) In the case of only one common incoming line, transfer the loads of the non-powered-off busbars among the taken incoming lines that are not adjacent to the powered-off busbar (i.e., the non-powered-off busbars other than these two non-powered-off busbars (i - 1)M and (i + 1)M). After the load margin of the non-powered-off busbar corresponding to the taken incoming line among these two non-powered-off busbars is greater than or equal to the pre-set load power before the powered-off busbar loses power, select the non-powered-off busbar corresponding to the taken incoming line among these two non-powered-off busbars for backup power supply switching to restore power supply to the powered-off busbar. For example, the non-powered-off busbar (i + 1)M and another non-powered-off busbar (i + 2)M share the same incoming line. After the non-powered-off busbar (i + 2)M is transferred by the adjacent non-powered-off busbar (i + 3)M, the load margin of the non-powered-off busbar (i + 1)M is the sum of its load margin and that of the non-powered-off busbar (i + 2)M. After the obtained sum is greater than or equal to the pre-set load power L(i) before the powered-off busbar iM loses power, select the non-powered-off busbar (i + 1)M for backup power supply switching to restore power supply to the powered-off busbar iM.

[0066] (2) In the case of two common incoming lines:

[0067] (21) A non-de-energized busbar connected to one of the incoming lines (a non-de-energized busbar other than the two non-de-energized buses (i-1)M and (i+1)M, such as the non-de-energized busbar (i+2)M) is selected for power transfer. If the above condition (1) is met, the non-de-energized busbar corresponding to the shared incoming line (e.g., the non-de-energized busbar (i+1)M) of the two non-de-energized buses can be placed in standby mode to restore power supply to the de-energized busbar iM.

[0068] If the above situation (1) is not satisfied, then continue to use another busbar connected to the incoming line (a busbar other than the two buses (i-1)M and (i+1)M, such as the busbar (i-2)M) to transfer power, so that the busbar corresponding to the shared incoming line (such as the busbar (i-1)M) can be put into standby mode to restore power to the lost busbar iM.

[0069] (22) All the buses connected to the common incoming lines that are not de-energized (except the two buses (i-1)M and (i+1)M, such as the buses (i-2)M and (i+2)M) are used for power transfer. If the above condition (1) is met, one of the two buses (e.g., the buses (i-1)M or (i+1)M) can be selected as a standby bus to restore power to the de-energized bus iM.

[0070] It should be noted that the condition for the load of the non-destroyed bus connected to the common incoming line to be transferred is that its load power should be less than or equal to the load margin of the non-destroyed bus that provides power transfer. For example, if the non-destroyed bus (i+2)M is transferred, the load power L(i+2) of the non-destroyed bus (i+2)M <= the load margin ΔS(i+3) of the non-destroyed bus (i+3)M, so that the load margin ΔS(i+1) of the non-destroyed bus (i+1)M + the load power L(i+2) of the non-destroyed bus (i+2)M>=the load power L(i) of the destroyed bus iM.

[0071] In the embodiment of the present invention, if there are backup power supplies on both sides of the power-off bus iM, that is, there are two non-power-off buses (i-1)M and (i+1)M, and these two non-power-off buses (i-1)M and (i+1)M are not connected to superconducting cables, but the load margins of these two non-power-off buses do not meet the requirements. At the same time, these two non-power-off buses (i-1)M and (i+1)M do not have or cannot realize the load balancing function, and it is necessary to use load shedding to ensure the safe operation of the backup power supply.

[0072] For multi-section backup of busbars, the information of electrical quantities of each incoming and outgoing line and the state information of switch quantities can be used to dynamically adjust the cut lines according to the importance of the load, give priority to cutting off the loads with low importance, and try to reduce the capacity of the cut loads. Dynamic overload joint cutting can be divided into two basic modes according to the timing of load cutting. One is to cut off part of the load before backup, that is, pre-cut load, and the other is to cut off the corresponding load according to the overload situation after backup, that is, joint cutting load after backup.

[0073] Among them, the main problem of pre-cutting load is that it may cause excessive load removal and reduce the power recovery rate. For example, some motors have an automatic exit mechanism after power failure, and pre-cutting load cannot obtain load exit information in advance, resulting in excessive load removal. Load shedding after standby is put into operation can effectively reduce the load shedding amount, but it may cause overload of the standby power supply equipment, affecting its safe operation.

[0074] In order to minimize the amount of load cut while ensuring the safe operation of the backup power supply, an improved solution for overload joint cutting is to adopt different joint cutting strategies according to the degree of overload.

[0075] Therefore, when the load margins of the two non-power-lost buses are both smaller than the load power pre-set before the power-lost bus loses power, and at least one of the two non-power-lost buses shares the same incoming line with a corresponding non-power-lost bus other than the two non-power-lost buses, if all the shared incoming lines are taken, and the loads of the non-power-lost buses that are not adjacent to the power-lost bus in all the taken incoming lines are transferred, the load margins of the two non-power-lost buses are still smaller than the load power pre-set before the power-lost bus loses power. Then, the overload rate is calculated based on the load power pre-set before the power-lost bus loses power and the incoming line capacity and load power of the non-power-lost bus with the largest load power among the two non-power-lost buses, and the overload rate is compared with the preset overload rate. Furthermore, based on the comparison result, the corresponding load switching mode is selected to cut off the overload load when the two non-power-lost buses are simultaneously put into standby power. Among them, the load switching mode is a load shedding mode after standby power is put into use, or a combination of pre-cut load and load shedding mode after standby power is put into use.

[0076] When the load margins of the two non-power-lost buses are both less than the load power preset before the power-lost bus loses power, and the two non-power-lost buses do not share the same incoming line with a corresponding non-power-lost bus other than the two non-power-lost buses, the overload rate is calculated based on the load power preset before the power-lost bus loses power and the incoming line capacity and load power of the non-power-lost bus with the largest load power among the two non-power-lost buses, and the overload rate is compared with the preset overload rate, and further based on the comparison result, the corresponding load switching mode is selected to cut off the overload load when the two non-power-lost buses are simultaneously used as backup for the power-lost bus.

[0077] The specific process is as follows: in the first step, when the load margins of the two buses that have not lost power are both less than the load power preset before the power-off bus loses power, it is determined whether the two buses that have not lost power have a common incoming line. If yes, the second step is executed; if not, the third step is jumped to;

[0078] Step 2: Continue to determine whether the load margins of the two buses that have not lost power after the power transfer are both less than the load power preset before the lost power bus loses power; if so, execute step 4; if not, end;

[0079] Step 3: Use the formula Calculate the overload rate η; where L i is the load power pre-set before the de-energized bus loses power; ΔS is the load margin of the un-de-energized bus with the largest load power among the two un-de-energized buses, and ΔS = S N -L N ; S N L is the incoming line capacity of the busbar with the largest load power among the two buses that have not lost power; N The preset load power of the busbar with the largest load power among the two buses with power failure;

[0080] Step 4: If the overload rate η(i) ≤ the preset overload rate η set , then select the load shedding mode after standby switching on to cut off the overload when the two buses that have not lost power are switched on to the power-lost bus at the same time;

[0081] Step 5: If the overload rate η(i)> the preset overload rate η set , then the combined pre-cut load and standby load shedding method is selected to cut off the overload when the two buses that have not lost power are simultaneously backed up to the power-lost bus; where the pre-cut load is ΔL = (L i -ΔS)-η set S N If the backup power supply is still overloaded, a secondary load shedding will be performed based on the actual overload amount.

[0082] like Figure 3 and Figure 4 As shown, the application scenario of a method for controlling a single-section busbar power failure backup automatic switching connected to a superconducting cable in an embodiment of the present invention is further described:

[0083] by Figure 3 The multi-section ring connection of a substation bus with superconducting cables is taken as an example. For the convenience of description, the busbars and switches are renumbered. Among the three main transformers, the No. 2 main transformer is a low-voltage side branch transformer. The 10kV busbar is divided into five sections. There is no section circuit breaker between the two sections of busbars QF02 and QF03 powered by the low-voltage side branch transformer, and the remaining busbars are connected by section circuit breakers. Figure 3For the specific control logic, please refer to Figure 4 shown.

[0084] Assuming that the de-energized bus is numbered iM, there are two adjacent buses on both sides that are not de-energized, numbered (i-1)M and (i+1)M. At this time, the load margin of the backup power supply is the backup power capacity minus the load already assumed. That is, the load margins of the non-de-energized buses (i-1)M and (i+1)M are ΔS(i-1)=S(i-1)-L(i-1) and ΔS(i+1)=S(i+1)-L(i+1), respectively. Among them, S(i+1) and S(i-1) can be set in advance, and L(i+1) and L(i-1) are calculated in real time by the incoming line current and the bus section voltage.

[0085] If there are backup power supplies on both sides of the de-energized bus iM, the calculated backup power capacity margins ΔS(i+1) and ΔS(i-1) can be compared with the load power L(i) of the de-energized bus iM before the de-energized bus iM loses power; if only one side of the non-de-energized bus has a capacity margin greater than or equal to L(i), then this section is the backup power section; if the capacity margins of the non-de-energized bus on both sides are greater than or equal to L(i), determine whether the incoming lines of the two non-de-energized bus sections are connected to superconducting cables; if so, select the non-de-energized bus without superconducting cables as the backup power supply; if not, the non-de-energized bus with a larger capacity margin can be selected as the backup power supply. For the bus section connected to the low-voltage side branch transformer, if Figure 3 Only one side of bus 2M and 3M has a backup power supply. When bus 2M or 3M loses power, if the capacity margin of bus 1M or 4M meets the demand, it can be directly put into backup.

[0086] If the above calculations show that the capacity of the backup power supply does not meet the requirements, for the bus section connected to the branch transformer on the low-voltage side, priority can be given to increasing the load margin of the backup power supply through load balancing to avoid load shedding as much as possible.

[0087] by Figure 3 Take the 1M busbar with power failure as an example. If the capacity margin of the backup power supplies 2M and 5M do not meet the requirements, the load sharing criterion can be activated:

[0088] A: ΔS(4)≥L(3), that is, the capacity margin of the 4M bus that has not lost power is greater than or equal to the load power carried by the 3M bus that has not lost power;

[0089] B: ΔS(2)+L(3)≥L(1), that is, after the load of the undelivered bus 3M is transferred by the undelivered bus 4M, the capacity margin of the undelivered bus 2M is the sum of its own capacity margin and the load power of the undelivered bus 3M, and the sum should be greater than or equal to the load power of the de-delivered bus 1M.

[0090] When the above criteria A and B are met at the same time, before the standby operation, firstly, load balancing is performed, and the load of the non-destroyed bus 3M is transferred to the non-destroyed bus 4M to increase the capacity margin of the non-destroyed bus 2M. Secondly, after the load is balanced, the non-destroyed bus 2M is put into standby operation to prevent the overload of the standby power supply No. 2 main transformer from causing continuous load shedding. Among them, the load balancing and standby operation process is as follows: trip QF03, confirm that QF03 is in the open position, close QF34 for transfer, confirm that QF34 is closed, and then close QF12 to put the non-destroyed bus 2M into standby operation, so as to realize the self-powered standby operation of the de-energized bus 1M to restore power supply.

[0091] If it is impossible to prevent the backup power supply from overloading by load balancing, or if the conditions for load balancing are not met and the backup power supply is overloaded, load shedding must be used to ensure the safe operation of the backup power supply.

[0092] In order to minimize the load being cut while ensuring the safe operation of the backup power supply, an improved solution for overload joint cutting is to adopt different joint cutting strategies according to the degree of overload. The specific methods are as follows:

[0093] If the overload rate η(i) ≤ the preset overload rate η set , then select the load shedding mode after standby switching on to cut off the overload when the two buses that have not lost power are switched on to the power-lost bus at the same time;

[0094] If the overload rate η(i)> the preset overload rate η set , then the combined pre-cut load and standby load shedding method is selected to cut off the overload when the two buses that have not lost power are simultaneously backed up to the power-lost bus; where the pre-cut load is ΔL = (L i -ΔS)-η set S N If the backup power supply is still overloaded, a secondary load shedding will be performed based on the actual overload amount.

[0095] like Figure 5 As shown in the figure, a single-segment busbar power failure automatic switching control system connected to a superconducting cable is proposed in an embodiment of the present invention, which is used in a power grid with a multi-segment structure where a substation busbar is connected to a superconducting cable, and includes:

[0096] The bus acquisition unit 110 is used to acquire the de-energized bus and the non-de-energized buses on its adjacent sides;

[0097] The first standby control unit 120 is used to calculate the load margin of the single non-powered bus according to the pre-set incoming line capacity and load power corresponding to the single non-powered bus, if the acquired non-powered bus is only a single non-powered bus on one side adjacent to the power-lost bus, and the incoming line of the single non-powered bus is not a connected superconducting cable, and after determining that the load margin of the single non-powered bus is greater than or equal to the pre-set load power before the power-lost bus loses power, select the single non-powered bus for direct standby, so as to restore power supply to the power-lost bus.

[0098] Among them, it also includes:

[0099] The second standby control unit is used for, if the acquired non-power-off busbars are two non-power-off busbars on both sides of the power-off busbar, and the incoming line of one of the non-power-off busbars is not a connected superconducting cable, and the incoming line of the other non-power-off busbar is a connected superconducting cable, calculating the load margin of the non-power-off busbar not connected to the superconducting cable according to the pre-set incoming line capacity and load power of the corresponding non-power-off busbar not connected to the superconducting cable, and after determining that the load margin of the non-power-off busbar not connected to the superconducting cable is greater than or equal to the pre-set load power before the power-off busbar loses power, selecting the non-power-off busbar not connected to the superconducting cable for direct standby, so as to realize the restoration of power supply to the power-off busbar.

[0100] Among them, it also includes:

[0101] The third standby control unit is used for calculating the load margin of the two buses that have not lost power according to the pre-set incoming line capacity and load power of the two corresponding buses that have not lost power, if the acquired non-power-loss busbars are two non-power-loss busbars on both sides of the power-loss busbar, and the incoming lines of the two buses that have not lost power are not the connected superconducting cables, and after it is determined that the load margin of at least one of the two buses that have not lost power is greater than or equal to the load power pre-set before the power-loss busbar loses power, selecting the direct standby with the largest load margin among the two buses that have not lost power to realize the restoration of power supply to the power-loss busbar.

[0102] Among them, it also includes:

[0103] The fourth standby control unit is used for taking one of the shared incoming lines, and transferring the load of the non-powered bus that is not adjacent to the power-lost bus in the taken incoming line, if it is determined that the load margins of the two non-powered buses are both less than the load power preset before the power-lost bus loses power, and at least one of the two non-powered buses shares the same incoming line with a corresponding non-powered bus other than the two non-powered buses, so that the load margin of the non-powered bus that corresponds to the shared taken incoming line among the two non-powered buses is greater than or equal to the load power preset before the power-lost bus loses power, and then selecting the non-powered bus that corresponds to the shared taken incoming line among the two non-powered buses for standby, so as to restore power supply to the power-lost bus; or

[0104] Take all the shared incoming lines and transfer the loads of the buses that are not adjacent to the de-energized busbar, so that the load margins of the two buses are greater than or equal to the load power pre-set before the de-energized busbar loses power. Then, any one of the two buses can be selected for standby to restore power to the de-energized busbar.

[0105] Implementing the embodiments of the present invention has the following beneficial effects:

[0106] The present invention is applicable to a multi-segmented power grid in which a substation bus is connected to a superconducting cable. The present invention comprehensively utilizes whether the incoming line of the non-de-energized bus is connected to the superconducting cable and whether the load margin of the non-de-energized bus is greater than or equal to the load power of the de-energized bus before power failure, so as to reasonably select the backup power supply between the sections, avoid the occurrence of overload load shedding, and improve the reliability and continuity of power supply.

[0107] It is worth noting that in the above system embodiment, the various units included are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of the functional units are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention.

[0108] A person skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, such as ROM / RAM, disk, CD-ROM, etc.

[0109] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for controlling the power failure of a single-section busbar connected to a superconducting cable, characterized in that: The method is used for connecting the substation busbar to a power grid with a multi-segment structure of a superconducting cable, and comprises the following steps: Obtain the de-energized busbar and the non-de-energized busbars on its adjacent side; If the acquired non-de-energized bus is only a single non-de-energized bus on one side adjacent to the de-energized bus, and the incoming line of the single non-de-energized bus is not a connected superconducting cable, the load margin of the single non-de-energized bus is calculated according to the pre-set incoming line capacity and load power corresponding to the single non-de-energized bus, and after it is determined that the load margin of the single non-de-energized bus is greater than or equal to the pre-set load power before the de-energized bus loses power, the single non-de-energized bus is selected for direct standby, so as to restore power supply to the de-energized bus; Wherein, the method further comprises: If the acquired non-de-energized busbars are two non-de-energized busbars on both sides of the de-energized busbar, and the incoming line of one of the non-de-energized busbars is not a connected superconducting cable, and the incoming line of the other non-de-energized busbar is a connected superconducting cable, the load margin of the non-de-energized busbar not connected to the superconducting cable is calculated according to the pre-set incoming line capacity and load power of the corresponding non-de-energized busbar not connected to the superconducting cable, and after it is determined that the load margin of the non-de-energized busbar not connected to the superconducting cable is greater than or equal to the pre-set load power before the de-energized busbar loses power, the non-de-energized busbar not connected to the superconducting cable is selected for direct standby, so as to restore power supply to the de-energized busbar.

2. The method for controlling the power failure of a single-section busbar connected to a superconducting cable according to claim 1, characterized in that: The method further comprises: If the acquired non-de-energized busbars are two non-de-energized busbars on both sides of the de-energized busbar, and the incoming lines of the two non-de-energized busbars are not connected superconducting cables, the load margins of the two non-de-energized busbars are calculated according to the pre-set incoming line capacities and load powers of the two corresponding non-de-energized busbars, and after it is determined that the load margin of at least one of the two non-de-energized busbars is greater than or equal to the pre-set load power of the de-energized busbar before power is lost, the direct standby with the largest load margin among the two non-de-energized busbars is selected to restore power supply to the de-energized busbar.

3. The method for controlling the power failure of a single-section busbar connected to a superconducting cable according to claim 2, characterized in that: The method further comprises: If it is determined that the load margins of the two non-delivered buses are both less than the load power preset before the delivered bus loses power, and at least one of the two non-delivered buses shares the same incoming line with a corresponding non-delivered bus other than the two non-delivered buses, one of the shared incoming lines is selected, and the load of the non-delivered bus that is not adjacent to the delivered bus is transferred, so that the load margin of the non-delivered bus corresponding to the shared incoming line among the two non-delivered buses is greater than or equal to the load power preset before the delivered bus loses power, and the non-delivered bus corresponding to the shared incoming line among the two non-delivered buses is selected for standby, so as to restore power supply to the delivered bus; or Take all the shared incoming lines and transfer the loads of the buses that are not adjacent to the de-energized busbar, so that the load margins of the two buses are greater than or equal to the load power pre-set before the de-energized busbar loses power. Then, any one of the two buses can be selected for standby to restore power to the de-energized busbar.

4. The method for controlling the power failure of a single-section busbar connected to a superconducting cable according to claim 3, characterized in that: The method further comprises: If all the shared incoming lines are taken, and the loads of the buses that are not adjacent to the de-energized busbar in all the taken incoming lines are all transferred, and the load margins of the two buses that are not de-energized are still less than the load power preset before the de-energized busbar loses power, the overload rate is calculated according to the load power preset before the de-energized busbar loses power and the incoming line capacity and load power of the bus that is not de-energized with the largest load power among the two buses that are not de-energized, and the overload rate is compared with the preset overload rate, and further according to the comparison result, the corresponding load switching mode is selected to cut off the overload load when the two buses that are not de-energized are simultaneously put into standby power supply to the de-energized busbar; wherein, the load switching mode is a load shedding mode after standby power supply or a combination of pre-cut load and load shedding mode after standby power supply.

5. The method for controlling the power failure of a single-section busbar connected to a superconducting cable according to claim 4, characterized in that: The method further comprises: By formula Calculate the overload rate η; where L i is the load power pre-set before the de-energized bus loses power; ΔS is the load margin of the un-de-energized bus with the largest load power among the two un-de-energized buses, and ΔS = S N -L N ; S N L is the incoming line capacity of the busbar with the largest load power among the two buses that have not lost power; N The preset load power of the busbar with the largest load power among the two buses with power failure; If the overload rate η(i) ≤ the preset overload rate η set , then select the load shedding mode after standby switching on to cut off the overload when the two buses that have not lost power are switched on to the power-lost bus at the same time; If the overload rate η(i)> the preset overload rate η set , then the combined pre-cut load and standby load shedding method is selected to cut off the overload when the two buses that have not lost power are simultaneously backed up to the power-lost bus; where the pre-cut load is ΔL = (L i -ΔS)-η set S N .

6. A single-section busbar power failure automatic switching control system connected to a superconducting cable, used in a power grid with a multi-segment structure where the substation busbar is connected to a superconducting cable, characterized in that: include: A bus acquisition unit, used to acquire the de-energized bus and the non-de-energized bus on its adjacent side; The first standby control unit is used to calculate the load margin of the single non-delivery bus according to the pre-set incoming line capacity and load power corresponding to the single non-delivery bus if the acquired non-delivery bus is only a single non-delivery bus on one side adjacent to the delivery bus, and the incoming line of the single non-delivery bus is not a connected superconducting cable, and after determining that the load margin of the single non-delivery bus is greater than or equal to the pre-set load power before the delivery bus loses power, select the single non-delivery bus to directly standby, so as to restore power supply to the delivered bus; Among them, it also includes: The second standby control unit is used for, if the acquired non-power-off busbars are two non-power-off busbars on both sides of the power-off busbar, and the incoming line of one of the non-power-off busbars is not a connected superconducting cable, and the incoming line of the other non-power-off busbar is a connected superconducting cable, calculating the load margin of the non-power-off busbar not connected to the superconducting cable according to the pre-set incoming line capacity and load power of the corresponding non-power-off busbar not connected to the superconducting cable, and after determining that the load margin of the non-power-off busbar not connected to the superconducting cable is greater than or equal to the pre-set load power before the power-off busbar loses power, selecting the non-power-off busbar not connected to the superconducting cable for direct standby, so as to realize the restoration of power supply to the power-off busbar.

7. The method for controlling the power failure of a single-section busbar connected to a superconducting cable according to claim 6, characterized in that: Also includes: The third standby control unit is used for calculating the load margin of the two buses that have not lost power according to the pre-set incoming line capacity and load power of the two corresponding buses that have not lost power, if the acquired non-power-loss busbars are two non-power-loss busbars on both sides of the power-loss busbar, and the incoming lines of the two buses that have not lost power are not the connected superconducting cables, and after it is determined that the load margin of at least one of the two buses that have not lost power is greater than or equal to the load power pre-set before the power-loss busbar loses power, selecting the direct standby with the largest load margin among the two buses that have not lost power to realize the restoration of power supply to the power-loss busbar.

8. The method for controlling the power failure of a single-section busbar connected to a superconducting cable according to claim 7, characterized in that: Also includes: The fourth standby control unit is used for, if it is determined that the load margins of the two non-power-lost buses are both less than the load power preset before the power-lost bus loses power, and at least one of the two non-power-lost buses shares the same incoming line with a corresponding non-power-lost bus other than the two non-power-lost buses, taking one of the shared incoming lines, and transferring the load of the non-power-lost bus that is not adjacent to the power-lost bus in the taken incoming line, so that the load margin of the non-power-lost bus corresponding to the shared taken incoming line among the two non-power-lost buses is greater than or equal to the load power preset before the power-lost bus loses power, and then selecting the non-power-lost bus corresponding to the shared taken incoming line among the two non-power-lost buses for standby, so as to restore power supply to the power-lost bus; or Take all the shared incoming lines and transfer the loads of the buses that are not adjacent to the de-energized busbar, so that the load margins of the two buses are greater than or equal to the load power pre-set before the de-energized busbar loses power. Then, any one of the two buses can be selected for standby to restore power to the de-energized busbar.

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