Distribution network distributed fault recovery method based on cooperation of flexible soft switch and interconnection switch

Abstract

The invention provides a power distribution network distributed fault recovery method based on cooperation of a flexible soft switch and an interconnection switch. The method comprises the following steps: firstly, establishing a power supply-switch-load topology search method considering SOP and TS; then realizing system power supply capacity estimation by using power supply-switch-load topology, and judging a load recovery level according to the estimated power supply capacity; performing first-stage system power adjustment based on the system power supply estimated capacity, and modifying an SOP port power instruction according to the load predicted power; and finally, judging whether the terminal feeder voltage of the low-voltage power distribution network is out of limit or not, and if so, performing two-stage system power adjustment considering the SOP. According to the method, distributed fault recovery can be realized through cooperation of the SOP and the TS after the low-voltage power distribution network has a fault, and the system recovery speed and the load recovery amount are taken into account on the premise of ensuring the safety and reliability of system fault recovery operation.

Description

Technical Field

[0001] The present invention relates to the technical field of coordinated fault recovery of flexible interconnected distribution networks, and in particular to a distributed fault recovery method for distribution networks based on the coordination of flexible soft switches and tie switches. Background Art

[0002] Renewable energy has become a future development trend, and the distribution network with a high proportion of new energy access has gradually become a key carrier of China's energy transformation today. When a large-scale renewable energy cluster is connected to the distribution network, due to the intermittent and volatile power output and the complexity of system voltage and frequency control, the requirements for fault recovery capabilities of the distribution network are significantly increased. The current distribution network fault recovery scheme mostly uses traditional contact switches (TS) to transfer loads. The system can only supply power through a single contact switch. This recovery method has limited load recovery and cannot flexibly assist power between regions. Therefore, how to effectively solve the power supply recovery of the end load of the low-voltage distribution network has become an urgent problem to be solved.

[0003] When a distribution network fails, the traditional centralized fault recovery method requires modeling of global information such as voltage and power of the low-voltage distribution network, which will lead to a long centralized calculation and decision-making process. The decision result is presented in the form of a steady-state recovery plan, which does not involve transient processes. In addition, if a centralized control center fails, it will cause a large-scale power outage in the area. Therefore, it is necessary to study the distributed fault recovery method. As a key device connecting various distribution networks, the soft open point (SOP) can achieve flexible mutual assistance of power in the power supply area during the fault period. Therefore, how to coordinate it with the tie switch has become an urgent problem to be solved. In addition, since the distributed fault recovery characteristics cannot obtain global information, there is a situation where the load recovery does not meet the system operation constraints after closing, which leads to the voltage limit problem during the fault recovery process. Therefore, how to achieve the maximum load recovery through distributed fault recovery under the premise of ensuring the safe operation of the system voltage has become a challenge. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies and gaps in the prior art, the present invention provides a distributed fault recovery method for a distribution network based on the collaboration of flexible soft switches and tie switches to solve the problems existing in the above-mentioned background technology.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] On the one hand, a distributed fault recovery method for a distribution network based on the coordination of a flexible soft switch and a tie switch is provided, comprising:

[0009] Step A: Establish power supply nodes, a set of SOP converter nodes connected to the power-off area, and a set of TS load nodes connected to the power-off area, apply Dijkstra algorithm to perform breadth-first search through the above node sets, calculate the shortest distance from each power supply to the SOP converter node connected to the power-off area and the shortest distance from each power supply to the TS load node connected to the power-off area, and determine the TS position according to the optimal TS determination logic to obtain the power supply-switch-load topology;

[0010] Step B: For the obtained power-switch-load topology, each lower-level proxy power point transmits its own remaining capacity information to the connected upper-level proxy, and the upper-level proxy performs the system capacity estimation decision process;

[0011] Step C: A one-stage system power adjustment is implemented to achieve capacity equalization according to the obtained system power capacity and load forecast power, and the SOP operation capacity is adjusted based on the load power factor angle;

[0012] Step D: Determine whether there is a voltage over-limit situation at the end feeder connection of the low-voltage distribution network during the distributed fault recovery process of the distribution network. If there is a voltage over-limit, perform a two-stage system power adjustment based on SOP. The power adjustment amount is obtained by subtracting the over-limit voltage value from the voltage limit value, and the voltage at the PCC is adjusted to within the normal operating limit.

[0013] Further, according to step A, a power supply-switch-load topology is established through the following steps A01 to A03:

[0014] Step A01: Establish a power supply node set, a SOP converter node set connected to the power-off area, and a TS node set connected to the power-off area respectively:

[0015] V sourse = {v s1 ,…,v si ,…,v sn}

[0016] V sop = {v d1 ,…,v dj ,…,v dm}

[0017] V TS = {v t1 ,…,v tk ,…,v tp}

[0018] Where V siis the node number of the i-th power supply, n is the number of power supplies; v dj is the node number of the jth SOP converter connected to the power-off area, m is the number of connected converters; v tk is the load node number of the kth TS connected to the power failure area, and p is the number of connected TSs.

[0019] Step A02: Take V sourse The point set is the starting point, V sop and V TS The point set is the end point, and one of the power points is taken as the starting point. The node with the shortest path from the starting point is continuously searched among the unmarked points, and marked until all nodes are marked, thereby obtaining V sourse and V sop 、V sourse and V TS The distance matrix is:

[0020]

[0021] In the formula, the matrix d(v s1 ,v d1 ) represents node v s1 and v d1 The distance between.

[0022] Step A03: After obtaining the upper matrix, according to the shortest path principle, the shortest distance of each row of the matrix is ​​the power-SOP topology and power-TS topology. Select the optimal TS closing point according to the power-TS topology. The optimal TS structure determination logic:

[0023] 1) It is preferred to select a TS whose power supply is only connected to the TS and not to any SOP;

[0024] 2) If the power supplies connected to the TS are all connected to the SOP, for multi-port SOPs, select the TS connected to the SOP with the most ports;

[0025] 3) When the number of SOP ports is consistent, the area with the highest power blocking degree is selected to supply power through TS.

[0026] Furthermore, in the step B, a source capacity estimation method considering the power supply-switch-load topology is designed.

[0027] Step B01: After obtaining the above topology, each lower-level proxy power point transmits its own remaining capacity information to the connected upper-level proxy, and the upper-level proxy performs the system capacity estimation decision process.

[0028] Step B02: Based on the power-SOP topology and power-TS topology obtained above, the power supplies connected to the same SOP / TS are classified into one category; the operating capacity constraints of the same category of power supplies are taken as the union, and then the operating capacity constraints of the SOP / TS connected to this category of power supplies are taken as the intersection:

[0029] {P SOPcap,m ,Q SOPcap,m}=({P DG,c ,Q DG,c}∪{P Fe,d ,Q Fe,d}∪{…})∩{P sop,m ,Q sop,m}

[0030] {P CAP,TS ,Q CAP,TS}=({P DG,e ,Q DG,e}∪{P Fe,f ,Q Fe,f}∪{…})∩{P TS,n ,Q TS,n}

[0031] Where P SOPcap,m , Q SOPcap,m and P CAP,TS , Q CAP,TS are the operating capacities of the mth SOP port and TS port respectively; P DG,c , P DG,e , Q DG,c , Q DG,e and P Fe,d , Q Fe,d , P Fe,f , Q Fe,f The remaining operating capacity of the distributed power source and upstream feeder connected to SOP / TS; P SOP,m , Q SOP,m and P TS,n , Q TS,n They are the operating capacities of the two respectively.

[0032] Step B03: Take the union of SOP, TS and the existing power supply points in the power failure area to obtain the total capacity of system failure recovery:

[0033] {P sys ,Q sys}={P CAP,TS ,Q CAP,TS}U{P SOPcap,1 ,Q SOPcap,1}

[0034] U{…}U{P SOPcap,n ,Q SOPcap,n}

[0035] Where P sys and Q sys Total capacity for system failure recovery in power outage areas.

[0036] Furthermore, in step C, the load predicted power value is evenly divided according to the estimated capacity of each switch, a system power adjustment is made in one stage, and the SOP capacity operation position is determined according to the load power factor angle, which specifically includes the following steps:

[0037] Step C01: The first stage system power adjustment should be based on the power output and load equation during the fault recovery process:

[0038]

[0039] Where P DG,i and Q DG,i is the power capacity of the distributed generation in the non-fault power failure area; ∑P loadi and ∑Q loadi The actual active / reactive power of the restored load node; P loadj and Q loadj Predict the load power of the next node j to be restored; is the load power factor angle.

[0040] Step C02: Evenly distribute the load prediction power according to the estimated capacity values ​​of each switch in step B02.

[0041] Furthermore, in the step D, it is determined whether the voltage at the end feeder of the low-voltage distribution network exceeds the limit, and the second-stage system power adjustment is performed according to the voltage exceeding the limit, which specifically includes the following steps:

[0042] Step D01: Calculate the voltage expression of the feeder at the end of the low-voltage distribution network:

[0043]

[0044] In the formula, is the voltage at the head end of ∑ feeder n, For busbar PCC i The voltage at the position, its phase is 0 by default; R i +jX i Line impedance, P sop and Q sop is the sum of active / reactive power transmitted by the SOP connected to the non-fault power-off area, R li and Q li is the actual power value of the load.

[0045] Step D02: Calculate the SOP active / reactive power two-stage adjustment amount according to the voltage over-limit amount:

[0046]

[0047] Where ΔP sop , ΔQ sop is the sum of all SOP power adjustments in the region; V Pol is the over-limit voltage value, V Pimax and V Pimin The upper and lower limits of voltage.

[0048] Step D03: The two-stage SOP power adjustment can achieve the target by combining different active and reactive power adjustment amounts. This patent provides an adjustment scheme with the goal of minimizing the apparent power of the two-stage SOP adjustment:

[0049]

[0050] Where T is the constant on the right side of the equation in step D02, and its value is in PCC i When the voltage exceeds the upper / lower limit, it is given respectively.

[0051] Step D04: Divide the second-stage power adjustment of each SOP equally according to the apparent power capacity of each SOP port:

[0052]

[0053] In the formula, S sop1 :S sop2 :…:S sopn =S1:S2:…:S n Apparent power capacity of each SOP port.

[0054] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the distributed fault recovery method for a distribution network based on the coordination of flexible soft switches and tie switches is implemented.

[0055] A computer-readable storage medium stores computer instructions, which, when executed by a processor, implement the distribution network distributed fault recovery method based on the coordination of flexible soft switches and tie switches.

[0056] Beneficial Effects

[0057] The present invention designs a distributed fault recovery method for distribution networks based on the collaboration of flexible soft switches and interconnecting switches. First, the power supply points in the system are set as lower-level agents, and SOP and TS are used as upper-level agents to implement the power-switch-load topology search process. This method effectively solves the problems of long calculation time and high communication requirements for centralized fault recovery. Then, the above-mentioned power-switch-load topology is considered to realize the estimation of system power capacity, and the load recovery level is judged according to the estimated capacity, taking into account both the system recovery speed and the load recovery amount. In addition, in order to solve the problem that the voltage at the end of the low-voltage distribution network is easy to exceed the limit, a two-stage system power adjustment process is performed according to the load predicted power and the voltage level at the end of the low-voltage distribution network, thereby completing distributed fault recovery and ensuring the safety of the system recovery process. The present invention provides a new idea for distributed fault recovery of distribution networks based on flexible interconnection devices. It takes into account both the calculation speed of the recovery plan and the load recovery amount while ensuring the safe and reliable recovery of the system, and has superiority. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 is a flow chart of the distributed fault recovery method of the present invention;

[0059] Figure 2 It is a flexible interconnected distribution network simulation system used in an embodiment of the present invention;

[0060] Figure 3 is a power supply-switch-load topology structure obtained in an embodiment of the present invention;

[0061] Figure 4 is the estimated power supply capacity and load recovery amount obtained in the embodiment of the present invention;

[0062] Figure 5 is the PCC steady-state voltage per unit value of the recovery process in the embodiment of the present invention;

[0063] Figure 6 is the transient voltage waveform of the feeder 104 when the loads 31 and 43 are restored in the embodiment of the present invention;

[0064] Figure 7 is the transient voltage waveform of the DC side of SOP2 when the loads 31 and 43 are restored in the embodiment of the present invention;

[0065] Figure 8 It is the transient frequency waveform of the power failure area when the loads 31 and 43 are restored in the embodiment of the present invention.

[0066] Fig. 9 This is a comparison chart of various fault solutions in the embodiment of the present invention. DETAILED DESCRIPTION

[0067] The following will be combined with the accompanying drawings of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] like Figure 1 As shown, the present invention provides a distributed fault recovery method for a distribution network based on the coordination of a flexible soft switch and a tie switch. In practical applications, the method specifically includes the following steps:

[0069] Step A: Establish power supply nodes, a set of SOP converter nodes connected to the power-off area, and a set of TS load nodes connected to the power-off area, apply Dijkstra algorithm to perform breadth-first search through the above node sets, calculate the shortest distance from each power supply to the SOP converter node connected to the power-off area and the shortest distance from each power supply to the TS load node connected to the power-off area, and determine the TS position according to the optimal TS determination logic to obtain the power supply-switch-load topology;

[0070] Step B: For the obtained power-switch-load topology, each lower-level proxy power point transmits its own remaining capacity information to the connected upper-level proxy, and the upper-level proxy performs the system capacity estimation decision process;

[0071] Step C: A one-stage system power adjustment is implemented to achieve capacity equalization according to the obtained system power capacity and load forecast power, and the SOP operation capacity is adjusted based on the load power factor angle;

[0072] Step D: Determine whether there is a voltage over-limit situation at the end feeder connection of the low-voltage distribution network during the distributed fault recovery process of the distribution network. If there is a voltage over-limit, perform a two-stage system power adjustment based on SOP. The power adjustment amount is obtained by subtracting the over-limit voltage value from the voltage limit value, and the voltage at the PCC is adjusted to within the normal operating limit.

[0073] Further, according to step A, a power supply-switch-load topology is established through the following steps A01 to A03:

[0074] Step A01: Establish a power supply node set, a SOP converter node set connected to the power failure area, and a TS node set connected to the power failure area respectively:

[0075] V sourse = {v s1 ,…,v si ,…,v sn}

[0076] V sop = {vd1 ,…,v dj ,…,v dm}

[0077] V TS = {v t1 ,…,v tk ,…,v tp}

[0078] Where V si is the node number of the i-th power supply, n is the number of power supplies; v dj is the node number of the jth SOP converter connected to the power-off area, m is the number of connected converters; v tk is the load node number of the kth TS connected to the power failure area, and p is the number of connected TSs.

[0079] Step A02: Take V sourse The point set is the starting point, V sop and V TS The point set is the end point, and one of the power points is taken as the starting point. The node with the shortest path from the starting point is continuously searched among the unmarked points, and marked until all nodes are marked, thereby obtaining V sourse and V sop 、V sourse and V TS The distance matrix is:

[0080]

[0081] In the formula, the matrix d(v s1 ,v d1 ) represents node v s1 and v d1 The distance between.

[0082] Step A03: After obtaining the upper matrix, according to the shortest path principle, the shortest distance of each row of the matrix is ​​the power-SOP topology and power-TS topology. Select the optimal TS closing point according to the power-TS topology. The optimal TS structure determination logic:

[0083] 1) It is preferred to select a TS whose power supply is only connected to the TS and not to any SOP;

[0084] 2) If the power supplies connected to the TS are all connected to the SOP, for multi-port SOPs, select the TS connected to the SOP with the most ports;

[0085] 3) When the number of SOP ports is consistent, the area with the highest power blocking degree is selected to supply power through TS.

[0086] Furthermore, in the step B, a source capacity estimation method considering the power supply-switch-load topology is designed.

[0087] Step B01: After obtaining the above topology, each lower-level proxy power point transmits its own remaining capacity information to the connected upper-level proxy, and the upper-level proxy performs the system capacity estimation decision process.

[0088] Step B02: Based on the power-SOP topology and power-TS topology obtained above, the power supplies connected to the same SOP / TS are classified into one category; the operating capacity constraints of the same category of power supplies are taken as the union, and then the operating capacity constraints of the SOP / TS connected to this category of power supplies are taken as the intersection:

[0089] {P SOPcap,m ,Q SOPcap,m}=({P DG,c ,Q DG,c}∪{P Fe,d ,Q Fe,d}∪{…})∩{P sop,m ,Q sop,m}

[0090] {P CAP,TS ,Q CAP,TS}=({P DG,e ,Q DG,e}∪{P Fe,f ,Q Fe,f}∪{…})∩{P TS,n ,Q TS,n}

[0091] Where P SOPcap,m , Q SOPcap,m and P CAP,TS , Q CAP,TS are the operating capacities of the mth SOP port and TS port respectively; P DG,c , P DG,e , Q DG,c , Q DG,e and P Fe,d , Q Fe,d , P Fe,f , Q Fe,f The remaining operating capacity of the distributed power source and upstream feeder connected to SOP / TS; P SOP,m , Q SOP,m and P TS,n , Q TS,n They are the operating capacities of the two respectively.

[0092] Step B03: Take the union of SOP, TS and the existing power supply points in the power failure area to obtain the total capacity of system failure recovery:

[0093] {P sys ,Q sys}={P CAP,TS ,Q CAP,TS}U{PSOPcap,1 ,Q SOPcap,1}U{…}U{P SOPcap,n ,Q SOPcap,n}

[0094] Where P sys and Q sys Total capacity for system failure recovery in power outage areas.

[0095] Furthermore, in step C, the load predicted power value is evenly divided according to the estimated capacity of each switch, a system power adjustment is made in one stage, and the SOP capacity operation position is determined according to the load power factor angle, which specifically includes the following steps:

[0096] Step C01: The first stage system power adjustment should be based on the power output and load equation during the fault recovery process:

[0097]

[0098] Where P DG,i and Q DG,i is the power capacity of the distributed generation in the non-fault power failure area; ∑P loadi and ∑Q loadi The actual active / reactive power of the restored load node; P loadj and Q loadj Predict the load power of the next node j to be restored; is the load power factor angle.

[0099] Step C02: Evenly distribute the load prediction power according to the estimated capacity values ​​of each switch in step B02.

[0100] Furthermore, in the step D, it is determined whether the voltage at the end feeder of the low-voltage distribution network exceeds the limit, and the second-stage system power adjustment is performed according to the voltage exceeding the limit, which specifically includes the following steps:

[0101] Step D01: Calculate the voltage expression of the feeder at the end of the low-voltage distribution network:

[0102]

[0103] In the formula, is the voltage at the beginning of feeder n, For busbar PCC i The voltage at the position, its phase is 0 by default; R i +jX i Line impedance, P sop and Q sop is the sum of active / reactive power transmitted by the SOP connected to the non-fault power-off area, R li and Q li is the actual power value of the load.

[0104] Step D02: Calculate the SOP active / reactive power two-stage adjustment amount according to the voltage over-limit amount:

[0105]

[0106] Where ΔP sop , ΔQ sop is the sum of all SOP power adjustments in the region; V Pol is the over-limit voltage value, V Pimax and V Pimin The upper and lower limits of voltage.

[0107] Step D03: The two-stage SOP power adjustment can achieve the target by combining different active and reactive power adjustment amounts. This patent provides an adjustment scheme with the goal of minimizing the apparent power of the two-stage SOP adjustment:

[0108]

[0109] Where T is the constant on the right side of the equation in step D02, and its value is in PCC i When the voltage exceeds the upper / lower limit, it is given respectively.

[0110] Step D04: Divide the second-stage power adjustment of each SOP equally according to the apparent power capacity of each SOP port:

[0111]

[0112] In the formula, S sop1 :S sop2 :…:S sopn =S1:S2:…:S n Apparent power capacity of each SOP port.

[0113] The above-mentioned distributed fault recovery scheme is applied to practice. The 69-node flexible interconnected low-voltage distribution network power supply recovery simulation system is as follows: Figure 2 As shown, the flexible interconnection simulation system consists of four parts, wherein power supply area 1 is interconnected with power supply area 2 and power supply area 3 by tie switches TS1 and TS2 respectively, and power supply area 3 is interconnected with power supply area 4 by tie switch TS3; power supply area 1 is interconnected with power supply area 3 by a two-port flexible interconnection device SOP1 (nodes 63 and 64), and power supply areas 2, 3 and 4 are connected by a three-port flexible interconnection device SOP2 (nodes 65, 66 and 67). Wherein the white square is a distributed power supply node, and the load is equivalent to a black circular node. According to a distributed fault recovery method for a distribution network based on the coordination of flexible soft switches and tie switches mentioned in the present invention, the effectiveness and superiority of the proposed method are verified.

[0114] Corresponds to Figure 2, This paper assumes that feeder 103 fails, power supply area 3 loses contact with the upper transformer, and the load in area 3 loses power and needs to be restored. At the time of the fault, the distributed power supply 44 is out of operation due to low voltage. At this time, the available power supply and capacity after the fault are shown in Appendix C Table C1. The capacity of the flexible interconnection devices SOP1 and SOP2 connected to the fault area is 300kVA, and the active power capacity and reactive power capacity of the interconnection switches TS1, TS2 and TS3 in the area are 350kW and 120kVar respectively. Figure 3 The power-switch-load topology under the distributed fault recovery method mentioned in this patent is composed of Figure 3 As shown, in the power-switch-load topology structure obtained by the method mentioned in this paper, on the basis of including all power points in the system, TS3 is used as the single traditional interconnection switch transfer point of the power-off area according to the TS selection logic, and the three power supply areas are respectively transferred from SOP1, SOP2 and TS3 to the non-fault power-off area. Figure 4 The estimated power capacity and load recovery amount under this patent method, the horizontal axis represents active power, unit: Kw, the vertical axis represents reactive power, unit: Kvar. Figure 4 It can be seen that the power supply-switch-load topology structure obtained by the method mentioned in this patent can support the restoration of power supply to load nodes 28-35, 38-41 and 43, and the load recovery amount is about 83.06%. Figure 5 is the PCC steady-state voltage per unit value at feeder 104 during the fault recovery process under the patent method, the horizontal axis represents the sequential recovery load node number, and the vertical axis represents the voltage per unit value. Figure 5 It can be seen that due to the distributed fault recovery characteristics, the voltages of loads 43 and 31 were 1.071pu and 0.918pu respectively after the first power adjustment during the recovery process, exceeding the upper / lower limits of the system voltage; after the second power adjustment process based on SOP, the voltage was adjusted to 1.050pu and 0.952pu, and the system successfully operated within the safety limit, ensuring the safe operation of the power-off area during fault recovery. Figure 6 : is the transient voltage waveform of feeder 104 during the recovery process of loads 31 and 43, the horizontal axis represents the recovery period, and the vertical axis represents the voltage per unit value. Figure 6 It can be seen that during the recovery process, the voltage of feeder 104 of load 43 smoothly increased from 1.033 to 1.071 after the first adjustment of SOP power, and smoothly decreased from 1.071 to 1.049 after the second adjustment of SOP power. During the recovery process, the voltage of feeder 104 of load 31 smoothly decreased from 0.957 to 0.918 after the first adjustment of SOP power, and smoothly increased from 0.918 to 0.952 after the second adjustment of SOP power. The voltage transient process of power adjustment in the two recovery processes was good, and basically no fluctuation occurred. Figure 7The transient voltage waveform of the SOP2 DC side during the recovery process of loads 31 and 43. The horizontal axis represents the recovery period, and the vertical axis represents the voltage, in V. Figure 7 It can be seen that during the recovery process of loads 43 and 31, the maximum points of transient voltage fluctuations of SOP primary power adjustment are 753V and 782V respectively, and the maximum points of transient voltage fluctuations of SOP secondary power adjustment are 846V and 760V respectively. The transient fluctuations on the DC side are all in the range of 0.9pu~1.1pu. Figure 8 The transient frequency waveform of the power-off area during the restoration process of loads 31 and 43. The horizontal axis represents the restoration period, and the vertical axis represents the frequency, in Hz. Figure 8 It can be seen that during the recovery process of loads 43 and 31, the maximum points of transient frequency fluctuation in the power-off area of ​​SOP power primary adjustment are 50.06Hz and 49.94Hz, and the maximum points of transient frequency fluctuation in the power-off area of ​​SOP power secondary adjustment are 49.97Hz and 50.05Hz. The transient frequency fluctuations are all in the range of 49.9Hz to 50.1Hz. Fig. 9 Compare 5 fault recovery solutions. Fig. 9 It can be seen that the distributed fault recovery method mentioned in method 3 of this patent that considers SOP and TS is slightly slower than the method that only considers TS (method 1) or SOP (method 2) in calculating the recovery plan, but it has a significant improvement in load recovery; method 4 does not estimate the capacity of the power point. Although it has advantages in recovery amount and recovery speed, it has the problem of voltage exceeding the limit caused by power overload; method 5 is a centralized fault recovery plan. While the load recovery amount is not significantly improved, it slows down the calculation speed of the recovery plan. The number of participating calculation nodes far exceeds the distributed fault recovery, and the simple second-order cone optimization model requires more than 5s to solve. In summary, method 3 proposed in this article takes into account the load recovery amount, system security and recovery plan calculation speed, and has advantages.

[0115] The present invention proposes a distributed fault recovery method for a distribution network based on the coordination of a flexible soft switch and a tie switch. First, a power-switch-load topology search method considering SOP and TS is established, and a Dijkstra algorithm is applied to perform a breadth-first search to obtain the shortest distance from each power point to the switch, and the TS position is determined according to the optimal TS selection logic, and the load is connected to the recovery topology to form a power-switch-load topology; then, the power-switch-load topology is used to realize the estimation of the system power capacity, and the load recovery level is determined according to the estimated power capacity; then, a first-stage system power adjustment is performed based on the system power estimated capacity, the SOP port power instruction is modified according to the load predicted power, and the SOP operating capacity is adjusted according to the load power factor angle; finally, it is determined whether the feeder voltage at the end of the low-voltage distribution network exceeds the limit, and if it exceeds the limit, a second-stage system power adjustment considering the SOP is performed to adjust the voltage at the PCC to within the safe operation limit of the system. This method effectively solves the problems of long centralized fault recovery calculation time and weak communication capability; it alleviates the problems of insufficient power capacity and voltage over-limit during load recovery, and ensures that the system can safely and reliably achieve the recovery process while meeting the maximum load recovery amount. This method takes into account both the system recovery speed and the load recovery amount while ensuring the safety and reliability of the system recovery process, and is economical and superior.

[0116] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0117] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A distributed fault recovery method for a distribution network based on the coordination of flexible soft switches and tie switches, characterized in that: include: Step A: Establish power supply nodes, a set of SOP converter nodes connected to the power-off area, and a set of TS load nodes connected to the power-off area, apply Dijkstra algorithm to perform breadth-first search through the above node sets, calculate the shortest distance from each power supply to the SOP converter node connected to the power-off area and the shortest distance from each power supply to the TS load node connected to the power-off area, and determine the TS position according to the optimal TS determination logic to obtain the power supply-switch-load topology; Step B: For the obtained power-switch-load topology, each lower-level proxy power point transmits its own remaining capacity information to the connected upper-level proxy, and the upper-level proxy performs the system capacity estimation decision process; Step C: A one-stage system power adjustment is implemented to achieve capacity equalization according to the obtained system power capacity and load forecast power, and the SOP operation capacity is adjusted based on the load power factor angle; Step D: Determine whether there is a voltage over-limit situation at the end feeder connection of the low-voltage distribution network during the distributed fault recovery process of the distribution network. If there is a voltage over-limit, perform a two-stage system power adjustment based on SOP. The power adjustment amount is obtained by subtracting the over-limit voltage value from the voltage limit value, and the voltage at the PCC is adjusted to within the normal operating limit.

2. A method for distributed fault recovery of distribution network based on coordination of flexible soft switches and tie switches according to claim 1, characterized in that: In step A, a power supply-switch-load topology is established through the following steps A01 to A03: Step A01: Establish a power supply node set, a SOP converter node set connected to the power-off area, and a TS node set connected to the power-off area respectively: V sourse ={v s1 ,…,v si ,…,v sn } V sop ={v d1 ,…,v dj ,…,v dm } V TS ={v t1 ,…,v tk ,…,v tp } Where V si is the node number of the i-th power supply, n is the number of power supplies; v dj is the node number of the jth SOP converter connected to the power-off area, m is the number of connected converters; v tk is the load node number of the kth TS connected to the power failure area, p is the number of connected TS, Step A02: Take V sourse The point set is the starting point, V sop and V TS The point set is the end point, and one of the power points is taken as the starting point. The node with the shortest path from the starting point is continuously searched among the unmarked points, and marked until all nodes are marked, thereby obtaining V sourse and V sop 、V sourse and V TS The distance matrix is: In the formula, the matrix d(v s1 ,v d1 ) represents node v s1 and v d1 The distance between Step A03: After obtaining the upper matrix, according to the shortest path principle, the shortest distance of each row of the matrix is ​​taken as the power-SOP topology and the power-TS topology. The optimal TS closing point is selected according to the power-TS topology. The optimal TS structure determines the logic: 1) It is preferred to select a TS whose power supply is only connected to the TS and not to any SOP; 2) If the power supplies connected to the TS are all connected to the SOP, for multi-port SOPs, select the TS connected to the SOP with the most ports; 3) When the number of SOP ports is consistent, the area with the highest power blocking degree is selected to supply power through TS.

3. A method for distributed fault recovery of distribution network based on coordination of flexible soft switches and tie switches according to claim 1, characterized in that: In step B, a source capacity estimation method considering the power supply-switch-load topology is designed. Step B01: After obtaining the above topology, each lower-level proxy power point transmits its own remaining capacity information to the connected upper-level proxy, and the upper-level proxy performs the system capacity estimation decision process. Step B02: Based on the power-SOP topology and power-TS topology obtained above, the power supplies connected to the same SOP / TS are classified into one category; the operating capacity constraints of the same category of power supplies are taken as the union, and then the operating capacity constraints of the SOP / TS connected to this category of power supplies are taken as the intersection: {P SOPcap,m ,Q SOPcap,m }=({P DG,c ,Q DG,c }∪{P Fe,d ,Q Fe,d } ∪{…})∩{P sop,m ,Q sop,m } {P CAP,TS ,Q CAP,TS }=({P DG,e ,Q DG,e }∪{P Fe,f ,Q Fe,f } ∪{…})∩{P TS,n ,Q TS,n } Where P SOPcap,m , Q SOPcap,m and P CAP,TS , Q CAP,TS are the operating capacities of the mth SOP port and TS port respectively; P DG,c , P DG,e , Q DG,c , Q DG,e and P Fe,d , Q Fe,d , P Fe,f , Q Fe,f The remaining operating capacity of the distributed power source and upstream feeder connected to SOP / TS; P SOP,m , Q SOP,m and P TS,n , Q TS,n are their own operating capacities, Step B03: Take the union of SOP, TS and the existing power supply points in the power failure area to obtain the total capacity of system failure recovery: {P sys ,Q sys }={P CAP,TS ,Q CAP,TS }U{P SOPcap,1 ,Q SOPcap,1 } U{…}U{P SOPcap,n ,Q SOPcap,n } Where P sys and Q sys Total capacity for system failure recovery in power outage areas.

4. A method for distributed fault recovery of distribution network based on coordination of flexible soft switches and tie switches according to claim 1, characterized in that: According to the estimated capacity of each switch, the load predicted power value is evenly divided to make a first-stage system power adjustment, and the SOP capacity operation position is determined according to the load power factor angle. The specific steps include the following: Step C01: The first stage system power adjustment should be based on the power output and load equation during the fault recovery process: Where P DG,i and Q DG,i is the power capacity of the distributed generation in the non-fault power failure area; ∑P loadi and ∑Q loadi The actual active / reactive power of the restored load node; P loadj and Q loadj Predict the load power of the next node j to be restored; is the load power factor angle, Step C02: Evenly distribute the load prediction power according to the estimated capacity values ​​of each switch in step B02.

5. The method for distributed fault recovery of distribution network based on coordination of flexible soft switches and tie switches according to claim 1, characterized in that: Determine whether the voltage at the end feeder of the low-voltage distribution network exceeds the limit, and perform a second-stage system power adjustment based on the voltage exceeding the limit, which specifically includes the following steps: Step D01: Calculate the voltage expression of the feeder at the end of the low-voltage distribution network: In the formula is the voltage at the beginning of feeder n, For busbar PCC i The voltage at the position, its phase is 0 by default; R i +jX i Line impedance, P sop and Q sop is the sum of active / reactive power transmitted by the SOP connected to the non-fault power-off area, R li and Q li is the actual power value of the load, Step D02: Calculate the SOP active / reactive power two-stage adjustment amount according to the voltage over-limit amount: Where ΔP sop , ΔQ sop is the sum of all SOP power adjustments in the region; V Pol is the over-limit voltage value, V Pimax and V Pimin are the upper and lower limits of voltage, Step D03: The two-stage SOP power adjustment can achieve the target by combining different active and reactive power adjustment amounts. This patent provides an adjustment scheme with the goal of minimizing the apparent power of the two-stage SOP adjustment: Where T is the constant on the right side of the equation in step D02, and its value is in PCC i When the voltage exceeds the upper / lower limit, Step D04: Divide the second-stage power adjustment of each SOP equally according to the apparent power capacity of each SOP port: In the formula, S sop1 :S sop2 :…:S sopn =S1:S2:…:S n , is the apparent power capacity of each SOP port.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the distributed fault recovery method for distribution network based on the coordination of flexible soft switches and tie switches as described in any one of claims 1 to 5 above is implemented.

7. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the computer instruction is executed by the processor, a distributed fault recovery method for a distribution network based on the coordination of a flexible soft switch and a tie switch as described in any one of claims 1 to 5 is implemented.

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