CN110707720B - Method for solving feeder line fault by using power electronic device SOP - Google Patents

Method for solving feeder line fault by using power electronic device SOP Download PDF

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CN110707720B
CN110707720B CN201910897484.7A CN201910897484A CN110707720B CN 110707720 B CN110707720 B CN 110707720B CN 201910897484 A CN201910897484 A CN 201910897484A CN 110707720 B CN110707720 B CN 110707720B
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sop
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distribution network
power distribution
reliability
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CN110707720A (en
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刘文霞
王晗钰
毛宇洋
王志强
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North China Electric Power University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • H02J3/1857—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters wherein such bridge converter is a multilevel converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Abstract

The invention discloses a method for solving a feeder fault by utilizing an SOP (service on demand) in the application field of power electronic equipment in a power distribution network, which aims at a power distribution network area containing important users, faces to the requirement of multi-terminal flexible interconnection, fully utilizes the uninterrupted power transfer capability of the SOP, reasonably plans the SOP by taking the improvement of the operation economy of the power distribution network and the power supply reliability of the important users as targets, and establishes an SOP double-layer planning model; and the SOP eight-state reliability model reasonably plans the SOP and achieves the purposes of improving the operation economy of the power distribution network and improving the power supply reliability of important users. The power supply reliability requirement of a user is improved, the SOP optimization trend function is played, the uninterrupted transfer capability, the fault recovery capability and the system self-healing capability are played, and the SOP is favorably popularized and applied.

Description

Method for solving feeder line fault by using power electronic device SOP
Technical Field
The invention belongs to the application field of power electronic equipment in a power distribution network, and particularly relates to a method for solving a feeder fault by using a power electronic device (SOP).
Background
The power distribution network is the last link from production to users of the power system, is closely connected with the users, and directly influences the power quality and the power supply reliability of the users. The international large power grid Conference (CIGRE) provides a concept of an active power distribution network in 2008, aims to improve the service quality and management performance index of a user, reduces the power supply interruption and power failure minute loss of the user by improving the reliability of a power distribution system, optimizes the operation mode of the power distribution network, and improves the operation economy of the power distribution network by enhancing the flexible control of the power distribution network. In recent years, the requirements of important users on the quality of electric energy and the reliability of power supply are continuously improved, in order to realize the upgrading and transformation of the existing power distribution network in China and meet the development requirements of new elements such as new energy, electric automobiles and diversified loads, the national energy agency issues 'action plan for power distribution network construction transformation' (2015-2020), and under the dual excitation of actual requirements and policy benefits, the architecture and mode of the power distribution network are greatly changed and gradually developed into a high-quality service platform for power supply. Active power distribution network technology and power electronic devices (SOPs) facing to the power distribution network are paid attention by various national scholars, and the key technology of the SOPs gradually becomes a new research hotspot in the field of the power distribution network. The SOP is a full-control power electronic device, compared with the traditional interconnection switch, the SOP has no mechanical operating mechanism, can respond to a control instruction in real time, is not limited by the action times, has longer service life, and has the advantages that because the SOP realizes decoupling at a direct current part, the fault current of a feeder line is easy to cut off, and the impact influence of the fault of the feeder line on a system is smaller. Therefore, compared with network reconstruction, the SOP uninterrupted conversion power is more suitable for the development requirement of a future power distribution network, and the flexibility and the rapidity of the operation control of the power distribution network are greatly improved. However, the investment and operation maintenance costs of the current SOP are high, and the SOP cannot be installed and used in a large range in a power distribution network, so that the reasonable application configuration of the SOP is an urgent problem to be solved.
SOP configuration and active power distribution system optimization based on tidal current betweenness published in southern Power grid technology 9, volume 11, the technology considers the fluctuation of distributed power sources and loads, proposes the concept of line tidal current betweenness suitable for a power distribution network, and applies the concept to SOP configuration analysis; an active power distribution network intelligent soft switch SOP planning method considering distributed power supply operation characteristics, published in the Chinese Motor engineering journal, volume 37, No. 7, is based on an optimal scene generation technology of Wassertein distance to construct a typical scene, and a scene analysis method is adopted to solve the problem of randomness of DG and load; the technique proposed a new stochastic programming model that considers demand side response, coordinated voltage control and SOP, and also considers the possibility of active Power generation curtailment of the DG plant, published IEEE Transactions on Power Systems, volume 32, 2. Factors such as fluctuation of the distributed power supply and diversity of loads are considered, but power supply reliability of users is not considered.
Disclosure of Invention
The invention aims to provide a method for solving a feeder fault by utilizing a power electronic device (SOP). The method is characterized in that aiming at a power distribution network area containing important users, the method faces to the requirement of multi-end flexible interconnection, fully utilizes the uninterrupted transfer capability of the SOP, reasonably plans the SOP by aiming at improving the operation economy of the power distribution network and the power supply reliability of the important users, and establishes an SOP double-layer planning model; and an SOP eight-state reliability model;
the SOP eight-state reliability model is changed based on the reliability model of the MMC commutation unit. The method comprises the steps of analyzing 4 operation modes based on an MMC (modular multilevel converter) converter unit and physical structures of submodules of the MMC converter unit, analyzing the relation between the fault rate of the submodules and a voltage load, establishing a dynamic reliability change model of a bridge arm valve group under the condition that the submodules have successive faults by adopting a mathematical induction method based on a bridge arm voltage-sharing strategy, correcting a single-ended MMC reliability model on the basis, and establishing an eight-state reliability model of a flexible multi-state switch based on a Markov method.
The quick reliability calculation method of the flexible multi-state switch eight-state reliability model is changed based on the traditional minimum path method; the maximum transfer capacity of an MMC port of the SOP is considered, the power failure loss index of a transfer path of an important user is given, a transfer load area of the SOP is obtained through breadth-first traversal search, and then a rapid reliability calculation method considering the transfer priority of the important user is provided on the basis of a traditional minimum path method by combining an SOP eight-state reliability model and the transfer load area.
The SOP double-layer planning model is established by taking important user power failure loss into power distribution network SOP planning to improve user power supply reliability, the operation model takes power distribution network operation loss and SOP operation loss minimum as targets, and constraint conditions comprise SOP operation constraint, power distribution network power balance constraint, node voltage constraint and branch capacity constraint.
The invention has the beneficial effects that: the SOP eight-state reliability model displays the occurrence probability and the average duration time of each state of the flexible multi-state switch, so that reliability parameters are provided for subsequently evaluating the reliability of the power distribution network containing the flexible multi-state switch by adopting a sequential Monte Carlo method, and the accuracy of reliability calculation of the power distribution network is improved; compared with the traditional minimum path method and the hybrid simulation method, the rapid reliability calculation method has high calculation efficiency and considers the priority transfer condition of important users; the SOP double-layer planning model meets the operating economy requirement of the power distribution network, improves the power supply reliability requirement of users, plays the role of SOP optimization trend, plays the uninterrupted power transfer capability, the fault recovery capability and the system self-healing capability of the SOP double-layer planning model, and is favorable for popularization and application of the SOP.
Drawings
FIG. 1 is a MMC and its sub-module physical structure;
FIG. 2 is a state space transition model of the flexible multi-state switch 16;
FIG. 3 is a schematic diagram of a flexible multi-state switch connected to a power distribution network;
FIG. 4 is a simple radial distribution network including SOPs;
fig. 5 is a diagram of a power distribution network.
Detailed Description
The invention provides a method for solving feeder line faults by utilizing a power electronic device (SOP). The method is directed at a power distribution network area containing important users, and is oriented to the requirement of multi-end flexible interconnection, the uninterrupted power transfer capability of the SOP is fully utilized, the SOP is reasonably planned with the aim of improving the operation economy of the power distribution network and the power supply reliability of the important users, and an SOP double-layer planning model is established; and an SOP eight-state reliability model; the invention is further described below with reference to the accompanying drawings.
FIG. 1 shows the MMC and its sub-modules physical structure;
the flexible multi-state Switch (SOP) is usually installed at a traditional interconnection switch, and is composed of a fully-controlled power electronic device, three mmcs (modular multilevel converters) are connected in parallel through direct current sides, alternating current sides of the mmcs are respectively connected to three different feeder lines, and active power flow between the three feeder lines can be controlled and reactive power can be provided during normal operation. The MMC commutation cell shown in fig. 1 includes 6 bridge arms, and each bridge arm is formed by connecting n identical Submodules (SM) and 1 reactor in series. Each SM sub-module includes 2 IGBT modules, 1 energy storage capacitor, a bypass thyristor, a bypass switch, and its auxiliary components, as well as a sub-module controller (SMC). According to the functional characteristics of the SOP, it can be divided into 4 subsystems: 3 MMC subsystems and 1 device-level control protection system. It has the following four modes of operation: (1) the device normally operates; (2) when the MMC is out of operation due to a fault at one end and the other two ends are in normal operation, power transmission can still be carried out; (3) the MMC at two ends stops running due to faults, works in a STATCOM mode, and only one working end performs reactive power control in a capacitance compensation mode; (4) when the MMCs at the three ends stop running or the device-level control protection system fails, the whole flexible multi-state switching device stops running.
Assuming that the above 4 subsystems have both working (1) and fault (0) states, combining the states of the 4 subsystems can obtain a 16-state space transition model of the entire flexible multi-state switch (as shown in fig. 2-5, the sequence of numbers in each rectangular box represents the state combination of MMC1, MMC2, MMC3 and device-level control protection). Therein will be
Figure BDA0002210757950000051
The 9 shutdown states are further merged to finally obtain an eight-state model, and the working states of the eight-state model are divided as shown in table 1:
TABLE 1 SOP eight State Table
Figure BDA0002210757950000052
In order to simplify the calculation, all the states are considered to be restored to the normal operation state once being overhauled, and the restoration rate is equal and is uniformly expressed by mu.
The method based on the Markov process calculates the multi-state reliability index as follows:
step 1: according to fig. 5 and table 1, the state transition matrix T of the flexible multi-state switch eight-state model is as follows:
Figure BDA0002210757950000061
step 2: applying markov process approximation principle:
PT＝P (2)
wherein P ═ PS1,PS2,…,PS8]Is the state probability of eight states, and the above formula can be rewritten as P (T-I) ═ P (3)
Wherein I is an identity matrix.
And 3, step 3: adding a total probability condition, wherein the sum of the probabilities of all system states is 1, as shown in formula (4):
Figure BDA0002210757950000062
finishing to obtain:
Figure BDA0002210757950000063
and 4, step 4: the Markov matrix equation obtained in the steps 2 and 3 is solved by applying a linear algebra algorithm, so that the state probability of 8 states can be calculated;
and 5, step 5: the frequency and duration are calculated using a frequency-duration method.
The frequency of each state Si can be calculated from equation (2-5):
Figure BDA0002210757950000064
in the formula: pSiProbability of being state i; pSlProbability of being a state directly connected to state i; lambda [ alpha ]kOr λlIs the rate of metastasis (failure or repair); mdIs the number of transitions leaving state i; meIs the number of transitions into state i.
The average duration of stay in state Si is:
Figure BDA0002210757950000071
according to the invention, based on the MMC reliability model and the Markov method for the dynamic reliability change of the bridge arm valve group, the flexible multi-state switch eight-state reliability model is established, and the calculation result is shown in Table 2.
TABLE 2 SOP eight State reliability index
Figure BDA0002210757950000072
Parameter K for the inventionsop qRecording the working states of three MMC commutation units under different states by using the parameter Psop SkRepresenting the state probability of the state Sk. When the q-th MMC is in failure shutdown, K sop q0 and 1 in normal operation. In the STATCOM mode, two MMC ports are in failure shutdown, the rest MMC ports can normally work but only can perform reactive power control and cannot transfer load, and therefore, the same as the shutdown of the whole equipment, the K issop qAre all recorded as 0, and the results are shown in Table 3
TABLE 3. SOP's MMC port State Table
Figure BDA0002210757950000073
Figure BDA0002210757950000081
For a multi-terminal interconnection power distribution system containing an SOP, the SOP port fault and the system equipment fault can be divided according to the type of a fault element. When the SOP port fails, the SOP can change the operation mode of the SOP, the protection system locks and isolates the failed port, and the rest ports work normally; when system equipment fails, the differential protection device in the power distribution network acts to quickly isolate a fault section. The invention considers the important user transfer priority, gives the important user transfer priority index and gives the corresponding fault recovery strategy, and lays a foundation for the quick load loss risk calculation considering the important user priority. When a fault occurs on a feeder lineIn time of birth, the SOP transfers the load on the feeder line to other feeder lines, and at this time, the MMC port capacity of the SOP directly determines the maximum transfer capability (TSC) of the SOP as the basis for dividing the load transfer region without interruption. The distribution network wiring mode containing SOP is shown in figure 3, and S is setsop qFor the SOP qth MMC port capacity, the maximum switching capacity of this port is affected by the port capacity of the other ports.
The sum of the maximum access power of the remaining ports is:
Figure BDA0002210757950000082
the maximum switching power of the MMC port satisfies the following equation:
Figure BDA0002210757950000083
important users are the core of the SOP service object, and in order to fully play the role of SOP in customizing power, important users of non-fault sections on the feeder line should be preferentially transferred. The power failure tolerance of the important users is evaluated, the power failure loss can be reduced to the greatest extent, the important users are guaranteed to supply power preferentially, the power supply reliability of the important users is improved, and the key point for dividing the SOP to supply load area is located.
The user power failure loss index is generally established according to the user category, the power failure frequency, the power failure time and the power failure duration. The transfer load area of the invention is changed along with the fault position, and the power failure time in the area is the same, therefore, the transfer priority of the important users is only related to the user scale, the user type and the power failure loss of the users. It should be noted that the handover path of the present invention generally refers to a handover path from an important user to an SOP access point, and if the path includes other important users, the handover path of other important users should be removed to avoid an exaggerated loss of power failure of the important user at the end of the feeder line, as shown in fig. 4. Power failure loss index f of important user transfer pathQComprises the following steps:
Figure BDA0002210757950000091
in the formula, the transfer path of the important user Q is omegaQThe load on the transfer path is PLThe power failure loss of unit power shortage of important user is CICQThe power failure loss of the unit power shortage of the ordinary user is the comprehensive user power failure loss CCDF (composite Customer Damage function) in the area.
If a certain device on the feeder line is in fault, if the fault occurs from the SOP access point to the power supply point, users which are not directly connected with the power supply need to be transferred out through the SOP, breadth-first traversal search is carried out from the SOP access point, in the searching process, the transfer priority of important users is ranked according to the power failure loss index of the transfer path of the important users, the transfer priority of the important users is compared layer by layer until traversal is finished or the maximum transfer power of the SOP port is reached, and finally a transfer load area is obtained. The area range is mainly related to the distribution of users on the feeder line and the maximum switching power of the SOP port.
Taking a simple radial distribution network containing SOP as an example, as shown in FIG. 4, Lp1 Lp5 Lp7For important users, assume Lp1When the line is in fault, the circuit breaker and the sectionalizing switch are operated to isolate Lp1Then, other users can be forwarded out through SOP, and through breadth-first traversal search, when important users, fault sections or feeder line ends are searched, the deeper search is stopped, and the hierarchy only has Lp5Marking the users on the important user transfer path as transferable and then from Lp5To search deeper, the important user L is foundp7But just exceeds the maximum transfer energy of the SOP port, and the searched ordinary users are added into the transfer load area until just the maximum transfer energy of the SOP port is not reached. Finally, the transshipment load region includes Lp2～Lp7。
If the device j on the feeder line has a fault, X is setijFor the transition of the load point iA state, which is a variable from 0 to 1, with 1 indicating a possibility of transfer, and 0 indicating an inability to transfer or no need for transfer. Assuming that an access point of an MMC port of the SOP on the feeder line is m, and the maximum transfer capacity of the MMC port is TSCSsop, for different devices j, determining a transfer load area by adopting the following steps:
firstly, initializing XijWhen the position of the failed device j is judged to be 0, i is 1,2, …, m and …, if the failed device j is not located from the SOP access point to the power point, the process is terminated, the next device is replaced, and the process I is repeated; if the fault equipment j is from the SOP access point to the power supply point, entering a flow II;
performing breadth-first traversal search from the SOP access point m, marking the searched users as visited, avoiding repeated search, stopping further search when important users, fault sections or feeder line tail ends are searched, recording the transfer path of the important users, and entering a process step three;
thirdly, calculating the power failure loss index of the important user transfer path, sorting the searched important users by transfer priority, sequentially judging whether the important users can be transferred out through SOP (sequence of order of priority), if so, indicating that the important users can be transferred out, then Xij＝1，i∈ΩQThen searching from the important user to a deeper layer, recording the transfer path of a new important user, repeating the process step (c), entering the process step (c) until the traversal is finished, and entering the process step (c) if the important users do not satisfy the following formula;
Figure BDA0002210757950000101
Figure BDA0002210757950000102
fourthly, after the traversal is finished, the rest important users are sequentially transferred and supplied out according to the transfer priority, if the above formula is met, the situation that the important users can be transferred and supplied out through the SOP is shown, and then X is carried outij＝1，i∈ΩQUntil all important users are forwarded out, entering the process (5);
fifthly, the rest ordinary users are transferred according to the sequence of breadth-first traversal search, and the user X is transferredijUntil the SOP maximum rotational power is reached, the process ends.
The invention takes all SOP states into consideration, and calculates the reliability index of the user in different SOP states by adopting a probability accumulation mode. The minimum path of the load point i is omegaiThe non-minimum path of the load point i is omegaOiThe state probability when the SOP state is Sk is Psop SkAt this time, the state of the MMC port connected with the q-th feeder line is Ksop qFailure rate of the device is λjThe power failure time of the fault is rjThe switching operation time of the circuit breaker and the section switch is rtts. The fast reliability calculation principle is as follows.
(1) Impact of equipment failure on the minimum path on the load point
Assuming that the load i on the q-th feeder line is in a failure state XijWhen the number is 1, the load i can be transferred, and the average failure power failure time mu of the load iijI.e. the switching operation time rttsThe circuit breaker with the head end of the feeder line nearest to the fault point is required to complete switching operation, and the load is converted into a supply state XijWhen the power failure time is 0, the load i cannot be transferred out, the power supply can be recovered after the fault is repaired, and the average fault power failure time mu of the load iijNamely the power failure time r of the faultjConsidering that the transfer conditions of all ports are different under different states of the SOP, the reliability index is calculated by adopting a probability accumulation mode, and the average fault power failure time mu of the load i caused by the fault of the equipment jijComprises the following steps:
Figure BDA0002210757950000111
(2) impact of non-minimum on-road equipment failure on load point
When the equipment with the load i not the minimum path fails, the load still keeps contact with the power supply, only the circuit breaker with the head end of the feeder line closest to the fault point is needed to complete switching operation, and the load i is not connected with the minimum path equipment, so that the switching operation is completedi mean time to failure μijI.e. the switching operation time rttsNamely:
μij＝λjrtts (14)
in conclusion, the average fault power failure time mu of the load i is obtained by comprehensively considering the reliability parameters of each device of the power distribution network, the transfer load area and the working state of the SOPiComprises the following steps:
Figure BDA0002210757950000121
in the SOP double-layer planning model, the upper-layer planning model calculates the annual comprehensive cost, including the investment cost, the annual operation maintenance cost, the annual operation loss cost and the annual user power failure loss of the SOP. The investment cost takes the time value of capital into consideration and is converted into annual investment cost; in summary, the objective function can be calculated by:
Figure BDA0002210757950000122
Figure BDA0002210757950000123
Figure BDA0002210757950000124
Figure BDA0002210757950000125
Figure BDA0002210757950000126
Figure BDA0002210757950000127
in the formula, d is the discount rate; m is the life cycle of the SOP; c. CsopAnd clossThe unit capacity cost and the unit active loss coefficient of the SOP are respectively, and omega is an annual operation and maintenance cost coefficient; omegasopAn alternate point set for installation of the SOP; ssop qIs the SOP capacity, k, at the qth candidate pointqIs a non-negative integer, Ssop perIs the SOP unit installation capacity; x is the number ofqFor the variable 0-1, taking 0 and 1 indicates the position q without and with equipment, Pnet loss(t) and Psop lossAnd (t) the active losses of the distribution network and the SOP at the tth hour are respectively solved through a power flow equation. M is the number of users of the power distribution network, N is the number of devices considering the fault probability in the power distribution network, EifFor the amount of user i lost load due to equipment failure after configuration of SOP, sijFailure rate, λ, for device j causing failure of user ijAnd the CIC is the power failure loss of the user with unit power failure amount, the resident user calculates according to the average power price, and the important user calculates according to the calculation result of the power failure loss evaluation model of the important user.
The lower-layer operation model aims at minimizing the operation network loss and the SOP operation loss of the power distribution network, and the objective function can be calculated by the following formula:
Figure BDA0002210757950000131
Figure BDA0002210757950000132
the constraint conditions comprise SOP operation constraint and power distribution network flow constraint:
1) three-terminal SOP capacity constraints
Figure BDA0002210757950000133
Figure BDA0002210757950000134
Figure BDA0002210757950000135
In the formula, PSOP 1(t)，PSOP 2(t)，PSOP 3(t)，QSOP 1(t)，QSOP 2(t)，QSOP 3(t) respectively the active power and the reactive power output by each port of the SOP in the t period; psop i(t) is the active power loss at port i; m isiIs the active power loss coefficient of port i; ssop 1、Ssop 2And Ssop 3The connecting capacity of the converter at each port of the SOP is respectively.
2) Power balance constraints for a system
Figure BDA0002210757950000141
Figure BDA0002210757950000142
In the formula (I), the compound is shown in the specification,
Figure BDA0002210757950000143
respectively representing the active load and the reactive load of the node i; u shapeiAnd UjRespectively representing the voltage amplitudes of the node i and the node j; gij、BijRespectively representing the conductance and susceptance of branch ij; deltaijRepresenting the difference between the voltage phase angles at node i and node j.
3) Node voltage constraint
Figure BDA0002210757950000144
4) Branch capacity constraint
Figure BDA0002210757950000145
Figure BDA0002210757950000146
In the formula IijIs the current flowing through branch ij.
The concrete calculation example is as follows:
the calculation structure of the invention refers to the main feeder 4 of IEEE RBTS BUS 6, the system wiring diagram is shown in figure 5, the reliability parameters such as element failure rate, repair time and the like in the system are shown in table 4, and the impedance value of the line unit length is 0.45+ j0.368 omega. The feeder line comprises 23 load points, system load data is shown in a table 5, total 1183 users are 33.63MW, 8 important users are included, a power failure loss information questionnaire of the important users is shown in a table 7, and due to the existence of a fault self-healing process, the operation time of the section switch is 1 min; the switching time of the isolating switch is 2 min.
The example analyzes and verifies an SOP double-layer planning model considering the power failure loss of important users, the reliability index and the port state table of the SOP refer to tables 1 and 2, the related parameters of the SOP are shown in table 6, the discount rate is 0.08, the average electricity price of residential users is 0.67 yuan/kWh, and the average electricity price of industrial users is 0.85 yuan/kWh. In consideration of the geographical position limitation, the selected position of the SOP is determined at the connection position of the traditional interconnection switch, including the node 2/12/16/21/26, and the installation position and the capacity of the SOP are optimally selected.
TABLE 4 element reliability parameters
Figure BDA0002210757950000151
TABLE 5 load data
Figure BDA0002210757950000152
TABLE 6 SOP-related parameters
Figure BDA0002210757950000161
TABLE 7 Power outage loss information questionnaire for important users
Figure BDA0002210757950000162
And then, the parameter result is recorded into an SOP double-layer planning model, and a hybrid optimization algorithm combining the proposed multi-objective evolutionary algorithm and cone planning is adopted for solving. Here, 2 planning schemes are set: 1) collectively planning a group of SOP ports; 2) and planning a plurality of groups of SOP ports in a distributed mode. The resulting planning scheme is shown in table 8, and the planning results are shown in table 9.
TABLE 8 SOP locating and sizing scheme
Figure BDA0002210757950000163
TABLE 9 planning results
Figure BDA0002210757950000164
The result shows that by adopting the scheme 1, the SOP port of 5.1MVA is accessed at the node 21, compared with the original system, the annual comprehensive cost of the SOP planning is reduced by 5.89 ten thousand yuan, 4.6 percent and 8.24 ten thousand yuan, the loss rate is reduced by 22.69 percent, and the operation economy of the power distribution network is obviously improved; by adopting the scheme 2, the node 21 and the node 26 are respectively connected with the SOP ports of 2.7MVA and 5.7MVA, compared with the original system, the annual comprehensive cost of the SOP planning is reduced by 2.65 ten thousand yuan, 2.07 percent and 11.76 ten thousand yuan, the loss reduction rate is 32.38 percent, compared with the scheme 1, the network loss and the power failure loss of important users are further reduced, but the annual comprehensive cost is slightly higher. The installation position and the capacity of the SOP determine the adjusting capacity of the system, the SOP is configured in the system to bring obvious benefits to the power distribution network, the economical operation requirement of the power distribution network is met, the power supply reliability requirement of users is improved, and the SOP planning scheme considering the power failure loss of important users is economical and feasible.

Claims (2)

1. A method for solving feeder line fault by using power electronic device SOP; the method is characterized in that aiming at a power distribution network area containing important users, the method faces to the requirement of multi-end flexible interconnection, fully utilizes the uninterrupted transfer capability of the SOP, reasonably plans the SOP by aiming at improving the operation economy of the power distribution network and the power supply reliability of the important users, and establishes an SOP double-layer planning model; and an SOP eight-state reliability model;
the SOP eight-state reliability model is changed based on the reliability model of the MMC commutation unit; analyzing 4 operation modes based on an MMC (modular multilevel converter) converter unit and the physical structures of submodules thereof, analyzing the relation between the failure rate of the submodules and the voltage load, establishing a reliability dynamic change model of a bridge arm valve group under the condition that the submodules have successive failures by adopting a mathematical induction method based on a bridge arm voltage-sharing strategy, correcting a single-ended MMC reliability model on the basis, and establishing a flexible multi-state switch eight-state reliability model based on a Markov method;
the quick reliability calculation method of the flexible multi-state switch eight-state reliability model is changed based on the traditional minimum path method; the maximum transfer capacity of an MMC port of the SOP is considered, the power failure loss index of a transfer path of an important user is given, a transfer load area of the SOP is obtained through breadth-first traversal search, and then a rapid reliability calculation method considering the transfer priority of the important user is provided on the basis of a traditional minimum path method by combining an SOP eight-state reliability model and the transfer load area;
the SOP double-layer planning model is established by taking important user power failure loss into power distribution network SOP planning to improve user power supply reliability, the operation model takes power distribution network operation loss and SOP operation loss minimum as targets, and constraint conditions comprise SOP operation constraint, power distribution network power balance constraint, node voltage constraint and branch capacity constraint.
2. A method of resolving feeder faults with a power electronics SOP according to claim 1; the method is characterized in that for a multi-terminal interconnection power distribution system containing the SOP, the SOP port fault and the system equipment fault can be divided according to the type of a fault element; when the SOP port fails, the SOP can change the operation mode of the SOP, the protection system locks and isolates the failed port, and the rest ports work normally; when system equipment fails, a differential protection device in the power distribution network acts to quickly isolate a fault section;
giving out an important user transfer priority index and a corresponding fault recovery strategy in consideration of the important user transfer priority, and laying a foundation for quick load loss risk calculation in consideration of the important user priority; when a fault occurs on a feeder line, the SOP transfers the load on the feeder line to other feeder lines.
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