Cross-power-supply-area zero-power-failure load reverse supply method based on minimum change of regional power flow

Abstract

The invention discloses a cross-power-supply-area zero power failure load reverse supply method based on regional power flow minimum change, and the method comprises the following steps: S1, determining a cross-power-supply-area loop closing moment, and carrying out the power flow calculation through employing a double-end loop type network power flow calculation method; s2, analyzing load flow calculation so as to determine the position of a power division point; s3, performing protection check on each protection constant value in the ring network, and setting a temporary constant value as required; s4, judging whether cross-power-supply-area closed-loop load reverse supply can be carried out without power outage or not; and S5, loop closing and load reversing are carried out. The method has the advantages of being new in loop closing mode, accurate in simulation calculation, small in calculation error, complete in safeguard measure, wide in application range, rapid in quality effect improvement and the like.

Description

Technical Field

[0001] The invention relates to an operation and control method of a power distribution network of an electric power system, and in particular to a zero-blackout load reversal method across power supply areas based on minimum change of regional power flow. Background Art

[0002] The existing urban distribution network generally adopts the "closed-loop structure, open-loop operation" mode, that is, when the power grid is operating normally, the line is powered by a single power supply, that is, open-loop operation; when the line fails or needs maintenance, dual power supplies are used to ensure uninterrupted power supply, that is, closed-loop operation, at this time, the staff is required to close the loop of the distribution network. The so-called closed-loop operation refers to the operation of closing the network composed of lines, transformers or circuit breakers in the electrical operation of the power system. In the event of a failure or maintenance, the user load can be transferred by switching operation, thereby ensuring the reliability of power supply to the user.

[0003] Generally speaking, a 500kV substation and its 220kV, 110kV, and 35kV substations constitute a power supply area. When the feeders under the power supply of two different power supply areas are closed, due to the large differences in system impedance and bus voltage between different substations, under certain system operating conditions, power accidents such as equipment overload, relay protection malfunction, short-circuit current exceeding the standard, and electromagnetic ring network caused by excessive closing current may occur. The closing current and impact current generated by this have a great impact on the operation mode of the power grid, and also affect the safety of the power grid, and may even cause the collapse of the power grid. In order to improve the reliability of power supply and ensure the safety of the power grid, many power grids currently only take measures to close the loop under the feeders under the power supply of the same power supply area, and maintain continuous power supply to users during the operation. This improves the reliability of power supply of the power grid and achieves good social and economic benefits. However, with the accelerated development of the power grid, the 220-500kV power grid has been gradually improved, and there are more and more live closing operations involving different power supply areas. In the past, when conducting line maintenance, the "first disconnect and then connect" method was usually adopted, that is, the feeder switch was disconnected first, and then the contact switch was closed. The closing operation of the 110kV substation across the power supply area of ​​the electromagnetic ring network of different voltage levels is generally adjusted by shutting down the whole station, which causes short-term power outages for users and seriously restricts the improvement of the level of power access for users. With the improvement of living standards, users have higher and higher requirements for power supply reliability. Therefore, in order to ensure the safe operation of the power grid and meet the user's requirements for power supply reliability, it is necessary to study the live closing operation, obtain the closing flow, and formulate a feasible operation method for closing and power transfer operation.

[0004] Patent CN202311096996 provides a 10kV closed loop analysis method and system across 500kV power supply areas. By collecting data for preprocessing, a steady-state analysis of the closed loop of the 10kV distribution network line across the 500kV area is carried out; based on the results of the steady-state analysis, a transient analysis of the closed loop of the 10kV distribution network line across the 500kV area is carried out; based on the results of the transient analysis, the loop current after the two lines are closed when the connecting circuit breaker is in the closed position is calculated to determine whether the 10kV line has the conditions for closing the loop. The above method requires collecting data for preprocessing, and needs to perform transient analysis based on the steady-state analysis results to determine the closing current based on the transient analysis results and then determine whether the conditions for closing the loop are met.

[0005] The existing technology has strong dependence on calculations: a large amount of data needs to be preprocessed, the analysis process is complicated, and the real-time performance is insufficient; the accuracy is insufficient: the power flow impact caused by voltage differences when closing the loop across power supply areas is difficult to accurately predict; there is a lack of protection measures: the extreme situation of superimposed faults during the closing process is not fully considered, and there are safety hazards and other problems. Summary of the invention

[0006] In order to solve the shortcomings of the above-mentioned technology, the present invention provides a zero-power-outage load reversal method across power supply areas based on minimum change of regional power flow.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a zero-power-outage load reversal method across power supply areas based on minimum change in regional power flow, the method comprising the following steps:

[0008] S1, determine the closing time of the cross-power supply area, and use the double-ended ring network power flow calculation method to perform power flow calculation;

[0009] S2, analyzing the power flow calculation results to determine the location of the power distribution point;

[0010] S3, check the protection settings of each protection setting in the ring network and set temporary settings as needed;

[0011] S4, judging whether it is possible to perform cross-power supply area loop load switching without power outage;

[0012] S5, close the loop and reverse the load.

[0013] Furthermore, the calculation time of the cross-power supply area closing simulation in step S1 is selected to be the time when the load volume is the same as or close to the expected closing time.

[0014] Furthermore, the steps of the double-ended ring network power flow calculation method in step S1 are:

[0015] Draw an equivalent circuit diagram of an equivalent two-terminal power supply network;

[0016] Calculate the power and current of the two-terminal power supply according to the power and impedance of each node at the time of closing the loop across the power supply area;

[0017] Determine the power and current flowing through each line segment of the ring network.

[0018] Furthermore, the double-ended ring network power flow calculation method adopts any one of manual calculation based on power system analysis principle, D5000 system PAS simulation, and new generation dispatching technology support system simulation.

[0019] Furthermore, the method of determining the position of the power distribution point in step S2 is to determine that the node where the power flow is jointly provided by the two-terminal power supply is the power distribution point.

[0020] Furthermore, step S3 performs protection verification on each protection setting in the ring network, that is, performs protection verification on the calculated closed-loop current and each protection setting in the ring network to ensure that the closed-loop current will not cause protection malfunction.

[0021] Furthermore, setting temporary set values ​​on demand means dynamically adjusting the current and time set values ​​of the protection based on the main transformer capacity, real-time load and potential fault scenarios before the cross-power supply area closing operation.

[0022] Furthermore, potential fault scenarios include upper line short circuit, ground fault or line abnormality within the station.

[0023] Furthermore, in step S4, the standard for judging whether the cross-power supply area loop closing can be performed without power outage is: the analysis results show that the cross-power supply area loop closing is a redistribution of the station's current, and the current of the relevant substations in the loop path will not be transferred when the loop is closed, so the method is used to perform the loop closing load reversal operation after protection verification.

[0024] Furthermore, the maximum cross-supply voltage level across the power supply area is 500 kV.

[0025] The present invention discloses a zero-power-off load reversal method across power supply areas based on minimum regional power flow change, which has the following advantages:

[0026] 1. New closing mode. The distribution network across the 500 kV power supply area cannot be closed directly and can only be reversed through short-term power outages. Relying on high-precision current calculation and safety verification, and synchronously equipped with fast ring release protection, the innovative "load reverse supply with zero power outage" of the distribution network across the 500 kV power supply area is realized at all voltage levels.

[0027] 2. Accurate simulation calculation. Relying on the new generation of analysis and decision-making center, the real-time cross-section of the power grid model provided by the integrated state estimation of the network, province and land is used to carry out accurate simulation calculation of the closed loop.

[0028] 3. Small calculation error. The simulation calculation results show that the closed-loop calculation error is less than 30A, which is 17% higher than the offline calculation accuracy.

[0029] 4. Comprehensive safeguards. In view of the extreme situation where there may be superimposed faults in the upper and lower lines during the ring closing process, a rapid ring opening protection is set up and short-circuit current is calculated item by item; emergency plans for various professions are compiled by classification and grading, and emergency drills are carried out to ensure rapid and safe handling in abnormal situations.

[0030] 5. Wide application range. In combination with the needs of maintenance pre-test and infrastructure overhaul work, loop closing tests have been carried out in different regions for different grid structures, different operating modes and different voltage levels.

[0031] 6. Improve quality and efficiency quickly. The company achieved the first “load reverse supply with zero power outage” across the 500 kV power supply area of ​​Hebei Southern Power Grid for Baoding Company. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Flow chart of the method of the present invention.

[0033] Figure 2 It is the equivalent circuit diagram of a double-ended ring network.

[0034] Figure 3 This is a schematic diagram of the power supply method of a 110kV substation.

[0035] Figure 4 Recording of the closing process of the No. 1 main transformer 501 of a 110kV substation. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0037] The present invention aims at the problem that cross-500kV power supply area needs to be shut down for load reversal. This scheme proposes a method for load reversal with zero power outage across power supply areas based on the minimum change of regional current. The current in the network during cross-area loop closing is calculated, and then the power distribution point position is determined, and protection verification is performed to determine whether cross-area loop closing and reversal can be performed without power outage. This effectively solves the problem that substations operating across power supply areas need to shut down the entire station for mode adjustment and load reversal, and improves the power supply reliability and power supply service quality of regional power users. Specifically, the method for load reversal with zero power outage across power supply areas based on the minimum change of regional current includes the following;

[0038] Taking a simple double-ended ring network as an example, the closed-loop power and closed-loop current analysis is carried out. Figure 2 The equivalent circuit diagram of the double-ended ring network is shown in the figure. The theoretical basis of the double-ended ring network power flow calculation method is as follows: The steady-state analysis of the power system points out that a single ring network with a loop voltage of 0 is equivalent to a two-terminal power supply network with equal voltages and the same phase at both ends. A two-terminal power supply network with unequal voltages and different phases at both ends can be equivalent to a single ring network with a loop voltage that is not 0.

[0039] By the loop current method, we know that:

[0040]

[0041] Since the above formula can be rewritten as

[0042]

[0043] The power Sa flowing through the impedance Z12 is solved from the above formula:

[0044]

[0045] In the formula, is the voltage difference between the two ends of the two-terminal network, as shown in the figure above.

[0046] Z xy is the impedance between node x and node y, with * indicating the conjugate value;

[0047] The impedance Z 12 The current;

[0048] , is the injected current of nodes 2 and 3;

[0049] U N is the rated voltage;

[0050] The impedance Z 12 The power of , with * means taking the conjugate value;

[0051] , is the computational load of nodes 2 and 3. The * indicates the conjugate value.

[0052] It can be seen from the above formula that in a two-terminal power supply network with unequal voltages at both ends, the power flowing through each end can be regarded as the superposition of two power components. The first is the power when the voltages at both ends are equal, which depends on the power flow and impedance distribution of the two-terminal power supply network, that is, the first part of formula 3. This part of power eventually flows to the load side and does not circulate in the closed loop path. The change is the power transferred by the closed loop power flow. The second is the power transfer component that depends on the difference in voltages at both ends. The power of the total impedance of the ring network, which is the second part of Formula 3, will circulate in the closed-loop path.

[0053] Based on the above theory, when the cross-regional 110kV substation is closed in a loop, the double-end ring network flow calculation method can be used to calculate and then determine the power distribution point. When the power distribution point is a closed-loop 110kV substation, only the bus load in the station is redistributed, and the flow of other substations in the loop does not change. In extreme cases, although the load in the station may be completely transferred to one main transformer for operation, it is consistent with the expected maintenance method. Therefore, if it is determined that the power distribution point is in the closed-loop station and is verified by protection and a temporary set value is set as needed, cross-regional zero power outage load reversal can be carried out. Figure 1 As shown, the specific steps are:

[0054] S1, determine the moment of closing the loop across power supply areas (determine the closing time), determine the flow calculation method, in this embodiment, the double-ended ring network flow calculation method is used for flow calculation; the moment of closing the loop across power supply areas in step S1 is to select a moment that is not much different from the load volume at the expected closing moment for simulation calculation. Among them, the steps of the double-ended ring network flow calculation method are: draw an equivalent circuit diagram of an equivalent double-ended power supply network; calculate the power and current supplied by the double-ended power supply according to the power and impedance of each node at the moment of closing the loop across power supply areas; obtain the power and current flowing in each line segment of the ring network. Among them, the double-ended ring network flow calculation method adopts any one of manual calculation based on power system analysis principles, D5000 system PAS simulation, and new generation dispatching technology support system simulation. It should be noted that in this method, there are many methods for power flow calculation. In the case, the new generation system simulation is used for calculation. It can also be simulated and calculated by applying the power system analysis principle, manual calculation, D5000 system PAS simulation and other methods. The calculation results can give the power distribution point position in the ring network, and the closed-loop current value can also be calculated. However, after actual verification and comparison, it is found that there are certain errors in the above three calculation results. The correctness of the three methods can be verified by collecting data from the recording device in the station, and finally the method with higher accuracy is determined to guide the feasibility of subsequent work. The manual calculation method has many disadvantages, such as the complex calculation process involving multi-level complex number calculations, the complex network topology of 220kV and above voltage levels cannot be truly restored by manual calculation, and the calculation cannot be performed according to the real-time section. At the same time, because the topology and load cannot be truly restored, the calculation results are quite different from the real data. The D5000 system PAS simulation method lacks a 220kV or above power grid model in the prefecture-level D5000 system. Although this method is better than manual calculation, it still has a certain deviation from the real data. The new generation of dispatching technology support system simulation is based on the support platform, and builds business applications such as real-time monitoring, automatic control, analysis and verification, and training simulation. It has the inherent advantages of power grid models and quasi-real-time sections provided by network, provincial, and local integrated state estimation. Through actual combat verification, the new generation of closed-loop simulation results are highly consistent with the operating data of the actual closed-loop power grid, and the simulation results are good.

[0055] S2, analyze the simulation results obtained from the power flow calculation and determine the location of the power distribution point; the way to determine the location of the power distribution point is to determine that the node where the power flow is jointly provided by the two-terminal power supply is the power distribution point (the definition of the power distribution point in the steady-state analysis of the power system: after obtaining the power, it is found that the power of some nodes in the network flows to them from both sides, and this node is called a power distribution point).

[0056] S3, perform protection verification on each protection setting in the ring network and set temporary settings as needed; perform protection verification on the calculated closing current and each protection setting in the ring network to ensure that the closing current will not cause protection malfunction; setting temporary settings as needed means dynamically adjusting the current and time settings of the busbar protection based on the main transformer capacity, real-time load and potential fault scenarios before the closing operation across the power supply area. Specifically, during the closing process, various situations may occur, such as upper 110kV, 220kV line faults and 10kV line faults. This method comprehensively considers and carries out relevant accident predictions. Potential fault scenarios include upper line short circuit, ground fault or abnormal line in the station.

[0057] a) The 110kV and 220kV switches on the upper side of the substation trip without fault. When the 110kV and 220kV switches on the upper side of the closed-loop substation trip without fault, a large amount of current may be transferred through the closed-loop substation. In order to quickly resolve such a situation, the 10kV busbar protection is set to a temporary setting before closing the loop. Considering the extreme situation when the loop is closed, the maximum current that may flow through the busbar in the station may be the current under full load of the main transformer, which can be set according to the capacity of a single transformer in the station. At present, the maximum capacity of the main transformer in the 110kV substation is 50MW, which is equivalent to about 2750A for 10kV and about 260A for 110kV. Generally, the current carrying capacity of the 110kV line is above 400A, and the capacity of the 220kV main transformer is much larger than that of the 110kV main transformer. Therefore, under this temporary setting protection, when load transfer occurs in extreme situations, the equipment in the loop will not exceed the limit for a long time.

[0058] b) Phase-to-phase short-circuit fault of the upper 110kV line. Accident anticipation is carried out for the phase-to-phase short-circuit fault of the upper 110kV line. Considering the extreme case, a phase-to-phase short-circuit fault occurs at the 110kV bus outlet of the 220kV substation. After the 110kV line protection is reliably actuated, it is verified that the sensitivity of the 10kV busbar temporary protection to the fault meets the requirements and can be effectively removed. Therefore, the phase-to-phase short-circuit and three-phase short-circuit faults can be removed through the 10kV busbar temporary protection, which will not affect the 110kV line protection reclosing.

[0059] c) Grounding fault of the upper 110kV line. Accident anticipation is carried out for the grounding fault of the upper 110kV line. Considering the extreme case, a single-phase grounding fault occurs at the 110kV bus outlet of the 220kV substation. After the 110kV line protection is reliably actuated, since the high-voltage system on the non-fault side is a large-current grounding system, the high-voltage side of the 110kV main transformer on the fault side is converted into a small-current grounding system. The zero-sequence voltage on the high-voltage side of the 110kV main transformer on this side increases, but it will not provide fault current to the fault point, and finally the relevant main transformer will be tripped through the zero-voltage protection of the main transformer protection gap.

[0060] d) 10kV line fault in the station. For the grounding fault of the 10kV line in the station, the accident anticipation is carried out. When the 10kV line fault occurs during the closing process, in order to prevent the mismatch between the bus protection and the line protection setting value in the station, the 10kV bus protection setting value time limit is set to 0.9s. In summary, during the closing process, by setting the 10kV bus protection to the current setting value under the main transformer capacity in the station and the time setting to 0.9s, most superimposed faults can be avoided.

[0061] S4, determine whether this method can be applied to carry out cross-power supply area loop closing load reversal without power outage; the analysis results show that the cross-power supply area loop closing is the redistribution of the station flow, and the flow of the relevant substations in the loop path will not be transferred when the loop is closed, so after protection verification, use this method to carry out the loop closing load reversal operation.

[0062] S5, finally, actual closing of the loop and reverse supply of load are performed.

[0063] The method of the present invention is described in detail below in conjunction with an application example (a 10 kV busbar loop-closing reverse load supply in a 110 kV substation). Two main transformers in a 110 kV substation are powered by 500 kV station A and 500 kV station B, respectively. Figure 3 As shown. Under normal conditions, the power supply path of the No. 1 main transformer is 500kV A station-220kV C station-110kV D station-110kV station, and the power supply path of the No. 2 main transformer is 500kV B station-220kV E station-110kV F station-110kV station. Before closing the loop, the two incoming line switches of the station are closed, the 501 and 502 switches on the low-voltage side of the main transformer are closed, and the 145 and 545 switches are open. This method is now used to reverse the load of the No. 1 main transformer to the No. 2 main transformer.

[0064] According to the method disclosed in the present invention, first determine whether this method can be applied to close the loop. Determine the closing time, and select a time that is not much different from the expected closing time load volume for flow calculation. This case uses a new generation of scheduling technology support system for simulation (because the two main transformers are parallel after closing 545, so before simulating closing 545, the two main transformers need to be adjusted to the same gear in advance), and the simulation data is recorded in Table 1:

[0065]

[0066] Table 1

[0067] Secondly, the calculation results are analyzed. The flow into the 10kV bus is negative. In this example, the above data shows that before closing the loop, the No. 1 main transformer carries a load of 15.5MW, the 501 switch current is 861A, the No. 2 main transformer carries a load of 16.8MW, and the 502 switch current is 937A. The simulation obtains the data when the loop is closed. After the 545 switch changes from the open position to the closed position, the load carried by the No. 1 main transformer decreases from 15.5MW to 9.1MW, and the load carried by the No. 2 main transformer increases from 16.8MW to 23.2MW, that is, load transfer occurs, and part of the load of the No. 1 main transformer is transferred to the No. 2 main transformer. When closing the loop, the power values ​​of the 501 and 502 switches are both negative, that is, they both flow into the bus, and the power distribution point is still within the 110kV station.

[0068] Then, protection checks are performed for various situations and temporary settings are set as needed;

[0069] Then, determine whether this method can be used for loop closing. This loop closing is the redistribution of the power flow of this station. When the loop is closed, the power flow of the relevant substations in the loop path is not transferred, and it is determined by protection verification that this method can be used for loop closing operation;

[0070] Finally, according to the pre-set plan, the loop load is reversed, the 545 switch is closed, and the 501 switch is pulled.

[0071] In order to verify the effectiveness of this method, the real closed-loop data records and simulation records are compared and verified as shown in Table 2 (Comparison of the new generation simulation and the actual situation of D5000 before the closing of a 110kV substation) and Table 3 (Comparison of the new generation simulation and the actual situation of D5000 during the closing of a 110kV substation):

[0072]

[0073] Table 2

[0074]

[0075] Table 3

[0076] Through the above data, such as Figure 4 The figure shows the waveform recording of the closing process of the No. 1 main transformer 501 of a 110kV substation, which can verify that the simulation results of the new generation system during closing are basically consistent with the actual operation of D5000.

[0077] Data comparison 501 current before closing the loop 501 current when closing the loop Next-generation state estimation 861 531 D5000 in action 859 539 Waveform verification 855 537

[0078] Table 4

[0079] Table 4 shows that by comparing the new generation of 501 intervals, D5000 and actual operation recordings, it can also be verified that the closing loop simulation results of the new generation system are consistent with the actual closing loop process, that is, the successful application of this method to achieve cross-regional load reversal with zero power outage.

[0080] In summary, in order to solve the problem that the distribution network across 500 kV power supply areas cannot be directly closed and can only reverse loads through short-term power outages, this solution proposes a method for zero power outage load reversal across power supply areas based on the minimum change in regional power flow. Through a variety of methods, the location of power distribution points in the network during cross-area closing is obtained and protection verification is performed to determine whether cross-area closing and reversal can be performed without power outages. This effectively solves the problem that substations operating across power supply areas require full station power outages for mode adjustment and load reversal, thereby improving the power supply reliability and power supply service quality for regional power users. The key protection points proposed in this patent and the effects they bring are:

[0081] 1. New closing mode. The distribution network across the 500 kV power supply area cannot be closed directly and can only be reversed through short-term power outages. Relying on high-precision current calculation and safety verification, and synchronously equipped with fast ring release protection, the innovative "load reverse supply with zero power outage" of the distribution network across the 500 kV power supply area is realized at all voltage levels.

[0082] 2. Accurate simulation calculation. Relying on the new generation of analysis and decision-making center, the real-time cross-section of the power grid model provided by the integrated state estimation of the network, province and land is used to carry out accurate simulation calculation of the closed loop.

[0083] 3. Small calculation error. The simulation calculation results show that the closed-loop calculation error is less than 30A, which is 17% higher than the offline calculation accuracy.

[0084] 4. Comprehensive safeguards. In view of the extreme situation where there may be superimposed faults in the upper and lower lines during the ring closing process, a rapid ring opening protection is set up and short-circuit current is calculated item by item; emergency plans for various professions are compiled by classification and grading, and emergency drills are carried out to ensure rapid and safe handling in abnormal situations.

[0085] 5. Wide range of applications. In combination with the needs of maintenance pre-test and infrastructure overhaul work, loop closing tests have been carried out in different regions for different grid structures, different operating modes, and different voltage levels. The experience was included in the National Typical Experience Bulletin on November 23, 2023 and received instructions from the leaders of the provincial company: in-depth analysis should be conducted, various operating scenarios should be comprehensively considered, good practices should be solidified, and experience that can be promoted should be formed and promoted and applied within the system at the right time. At present, this model has been fully implemented in various municipal companies of Hebei Southern Power Grid.

[0086] 6. Improve quality and efficiency quickly. On June 15, 2023, Baoding Company achieved the first "load reversal with zero power outage" across the 500 kV power supply area of ​​the Southern Power Grid in Hebei Province. On this basis, this technology was actively promoted. Against the background of large-scale relocation and construction of the Xiong'an power grid and increasingly frequent demand for load reversal, it broke through the rigid demand for closing devices in advanced areas of Jiangsu and Zhejiang, and achieved non-stop closing and load reversal at all voltage levels of the distribution network with zero investment, saving a total of 39.6 million yuan in hardware capital investment in 132 closing points of 25 cross-power supply area substations in the Baoxiong area, reducing power outages of 1,500 lines per year, reducing power outages for 1.35 million households, and increasing power supply by 2.25 million kWh, improving the power supply reliability of 13 first-level important users and 17 second-level important users, improving service levels, optimizing the business environment, and effectively improving the power supply reliability and power supply service quality of regional power users, providing Baoding experience for exploring the management of frequent power outages in distribution networks and ensuring power supply reliability.

[0087] The above implementation modes are not limitations of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also belong to the protection scope of the present invention.

Claims

1. A method for zero-blackout load reversal across power supply areas based on minimum change in regional power flow, characterized in that: The method comprises the following steps: S1, determine the closing time of the cross-power supply area, and use the double-ended ring network power flow calculation method to perform power flow calculation; S2, analyzing the power flow calculation results to determine the location of the power distribution point; S3, check the protection settings of each protection setting in the ring network and set temporary settings as needed; S4, judging whether it is possible to perform cross-power supply area loop load switching without power outage; S5, close the loop and reverse the load.

2. The method for load reversal with zero blackout across power supply areas based on minimum change in regional power flow according to claim 1 is characterized in that: The time for calculating the cross-power supply area closing simulation in step S1 is a time when the load volume is the same as or close to the expected closing time.

3. The method for load reversal with zero power outage across power supply areas based on minimum change in regional power flow according to claim 2 is characterized in that: The steps of the double-ended ring network power flow calculation method in step S1 are: Draw an equivalent circuit diagram of an equivalent two-terminal power supply network; Calculate the power and current of the two-terminal power supply according to the power and impedance of each node at the time of closing the loop across the power supply area; Determine the power and current flowing through each line segment of the ring network.

4. The method for load reversal with zero power outage across power supply areas based on minimum change in regional power flow according to claim 3 is characterized in that: The double-ended ring network power flow calculation method adopts any one of manual calculation based on power system analysis principle, D5000 system PAS simulation, and new generation dispatching technology support system simulation.

5. The method for load reversal with zero blackout across power supply areas based on minimum change in regional power flow according to claim 1 is characterized in that: The method of determining the position of the power distribution point in step S2 is to determine that the node where the power flow is jointly provided by the two-terminal power supply is the power distribution point.

6. The method for load reversal with zero blackout across power supply areas based on minimum change in regional power flow according to claim 1 is characterized in that: The step S3 performs protection verification on each protection setting in the ring network, which is to perform protection verification on the calculated closed-loop current and each protection setting in the ring network to ensure that the closed-loop current will not cause protection malfunction.

7. The method for load reversal with zero blackout across power supply areas based on minimum change in regional power flow according to claim 6 is characterized in that: The on-demand setting of temporary constants refers to dynamically adjusting the current and time constants of the protection based on the main transformer capacity, real-time load and potential fault scenarios before the cross-power supply area loop closing operation.

8. The method for load reversal with zero blackout across power supply areas based on minimum change in regional power flow according to claim 7 is characterized in that: The potential fault scenarios include upper line short circuit, ground fault or station line abnormality.

9. The method for load reversal with zero power outage across power supply areas based on minimum change in regional power flow according to claim 1 is characterized in that: In step S4, the standard for judging whether the cross-power supply area loop closing load switching can be performed without power outage is: the analysis result shows that the cross-power supply area loop closing is a redistribution of the station flow, and the flow of the relevant substations in the loop path will not be transferred when the loop is closed, so the loop closing load switching operation is performed after protection verification.

10. The method for load reversal with zero blackout across power supply areas based on minimum change in regional power flow according to any one of claims 1 to 9, characterized in that: The maximum cross-supply voltage level across the power supply area is 500kV.

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