CN109066659B - Microgrid island operation reliability assessment method and terminal equipment - Google Patents
Microgrid island operation reliability assessment method and terminal equipment Download PDFInfo
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Abstract
The invention relates to the technical field of computers, and provides a micro-grid island operation reliability assessment method and terminal equipment. The method comprises the following steps: acquiring the fault rate and the fault repair rate of each element in the microgrid, and calculating the fault-free working time and the fault repair time of each element according to the fault rate and the fault repair rate of each element to obtain a time sequence table; according to a preset fault isolation strategy and a preset micro-grid power interaction strategy, analyzing the operation condition of the micro-grid after each element in the time sequence list fails respectively, and determining the power failure time of each load node in the micro-grid after each failure occurs; calculating the reliability index of each load node; and calculating the reliability index of the micro-grid system according to the reliability index of each load node. The method and the device can improve the evaluation accuracy of the operation reliability of the isolated island of the micro-grid of the industrial park containing the EV charging station.
Description
Technical Field
The invention relates to the technical field of micro-grid operation reliability evaluation, in particular to a micro-grid island operation reliability evaluation method and terminal equipment.
Background
In recent years, clean energy technologies such as wind power and photovoltaic are rapidly developed, and the development of distributed power supplies represented by distributed photovoltaic presents an explosive growth trend. The access of a large number of micro-grids to a power distribution system will be a new form of future power distribution networks, which will be more common in some large industrial parks. The development of the micro-grid technology solves the problem of the influence of unstable power generation output of the clean energy on the power distribution network to a great extent, simultaneously improves the control capability of a power grid dispatching center on the distributed power supply, and powerfully promotes the high permeability access of the clean energy power generation.
The rapid development of Electric Vehicles (EVs) brings a large number of EV charging devices to be connected to a power distribution network, and the EV charging devices become new elements in the micro-grid. Considering the application of the technology of electric Vehicle-to-grid (V2G), the analysis of the operating condition of the micro grid becomes more complicated.
The micro-grid operation mode mainly comprises a grid connection mode and an island mode. When the micro-grid is connected to the power grid and operates, the load in the power grid is supplied with power jointly by the distributed power supply in the external power grid and the micro-grid. In this case, the load is not greatly affected by the fluctuation of the distributed power supply output. And the electric vehicles in the energy storage system and the EV charging station are in a charging state. When the micro-grid isolated island operates, the load in the grid is mainly supplied with power by the distributed power supply in the grid. Due to the fluctuation of the output of the distributed power supply and the randomness of the magnitude of the electric load, the power between the source charges is difficult to maintain balanced, and therefore an energy storage system is needed to maintain the stability of the operation of the microgrid system.
At present, certain research is carried out at home and abroad on the aspect of reliable operation evaluation under the isolated island state of the microgrid, the operation reliability of the microgrid under the isolated island state is mainly analyzed from different angles, but the existing evaluation methods do not take the access condition of an electric vehicle into account, and the operation reliability of the isolated island of the microgrid in an industrial park containing an EV charging station cannot be accurately evaluated.
Disclosure of Invention
In view of this, the embodiment of the invention provides a micro-grid island operation reliability assessment method and terminal equipment, so as to solve the problem that the existing assessment method cannot accurately assess the reliability of micro-grid island operation of an industrial park containing an EV charging station.
The first aspect of the embodiment of the invention provides a micro-grid island operation reliability assessment method, which comprises the following steps:
acquiring the fault rate and the fault repair rate of each element in the microgrid, and calculating the fault-free working time and the fault repair time of each element according to the fault rate and the fault repair rate of each element to obtain a time sequence table;
according to a preset fault isolation strategy and a preset micro-grid power interaction strategy, analyzing the operation condition of the micro-grid after each element in the time sequence list fails respectively, and determining the power failure time of each load node in the micro-grid after each failure occurs; the preset power interaction strategy of the micro point network is a power interaction strategy combining energy storage equipment, electric vehicle charging station equipment and a distributed power supply in the micro grid;
calculating a reliability index of each load node, wherein the reliability index comprises at least one of average failure rate, average failure time and average power failure time;
and calculating the reliability index of the micro-grid system according to the reliability index of each load node.
A second aspect of the embodiments of the present invention provides a device for evaluating operation reliability of a micro grid island, including:
the acquisition module is used for acquiring the fault rate and the fault repair rate of each element in the microgrid, and calculating the fault-free working time and the fault repair time of each element according to the fault rate and the fault repair rate of each element to obtain a time sequence table;
the processing module is used for analyzing the operation condition of the microgrid after the elements in the time sequence list have faults respectively according to a preset fault isolation strategy and a preset microgrid power interaction strategy, and determining the power failure time of each load node in the microgrid after each fault occurs; the preset power interaction strategy of the micro point network is a power interaction strategy combining energy storage equipment, electric vehicle charging station equipment and a distributed power supply in the micro grid;
the first calculation module is used for calculating the reliability index of each load node, and the reliability index comprises at least one of average failure rate, average failure time and average power failure time;
and the second calculation module is used for calculating the reliability index of the micro-grid system according to the reliability index of each load node.
A third aspect of the embodiments of the present invention provides a terminal device, which includes a memory, a processor, and a computer program stored in the memory and operable on the processor, and when the processor executes the computer program, the method for evaluating reliability of operation of a microgrid island in the first aspect is implemented.
A fourth aspect of the embodiments of the present invention provides a computer-readable storage medium, where a computer program is stored, and when the computer program is executed by a processor, the method for evaluating reliability of operation of a microgrid island in the first aspect is implemented.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: according to the embodiment of the invention, aiming at the isolated island operation mode of the industrial park microgrid with an EV charging station, a sequential Monte Carlo simulation method is adopted, and the operation reliability of the park microgrid in the isolated island mode is evaluated according to the energy storage equipment in combination with a power interaction strategy between the EV charging station and the microgrid and a fault isolation strategy after internal fault in the microgrid in the isolated island state, so that the evaluation accuracy of the isolated island operation reliability of the industrial park microgrid with the EV charging station can be improved, the operation stability of the microgrid and the new energy acceptance capability are improved, and meanwhile, the unified scheduling of the distributed power supply by the power grid is facilitated.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a flowchart of an implementation of a method for evaluating the operation reliability of a micro grid island according to an embodiment of the present invention;
fig. 2 is a flowchart illustrating an implementation of analyzing an operation condition of a microgrid after each element in a time sequence list fails in a microgrid island operation reliability assessment method according to an embodiment of the present invention;
fig. 3 is a diagram illustrating that the power failure time of each load node in the microgrid is determined in the microgrid island operation reliability assessment method provided by the embodiment of the present invention;
fig. 4 is a schematic diagram of a microgrid feeder partition according to an implementation example provided by the embodiment of the present invention;
fig. 5 is a schematic diagram of a microgrid island operation reliability evaluation device provided by an embodiment of the present invention;
fig. 6 is a schematic diagram of a terminal device according to an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
Fig. 1 is a flowchart of an implementation of a method for evaluating the operation reliability of a micro grid island according to an embodiment of the present invention, which is detailed as follows:
in S101, the fault rate and the fault repair rate of each element in the microgrid are obtained, and the non-fault working time and the fault repair time of each element are calculated according to the fault rate and the fault repair rate of each element to obtain a time sequence table.
In this embodiment, the Time To Failure (TTF) and the Time To Repair (TTR) of each element may be calculated according to the random number and the failure rate and the failure repair rate of each element, so as to obtain the time sequence table. For example, the time sequence table may be represented as Tf＝[TTF1,TTF2,····,TTFn]，Tr＝[TTR1,TTR2,····,TTRn]。
As an embodiment of the present invention, S101 may include:
calculating the fault-free working time and fault repair time of each element according to the first calculation formula, the fault rate and the fault repair rate of each element; the first calculation formula is:
wherein, TTFiFor the fault-free working time of the ith element, λiFailure rate of the ith element; TTRiTime to failure repair of ith element, muiThe failure repair rate of the ith element; u is a random number between (0,1) subject to uniform distribution.
In this embodiment, the non-failure operation time and the failure recovery time of each element in the network can be calculated according to formula (1).
In S102, according to a preset fault isolation strategy and a preset micro-grid power interaction strategy, respectively analyzing the operation condition of the micro-grid after each element in the time sequence list has a fault, and determining the power failure time of each load node in the micro-grid after each fault occurs; the preset power interaction strategy of the micro point network is a power interaction strategy combining energy storage equipment, electric vehicle charging station equipment and a distributed power supply in the micro grid.
In this embodiment, the preset fault isolation strategy and the preset microgrid power interaction strategy of the microgrid can be determined according to an isolated island operation mode of the microgrid in the industrial park with the EV charging station. And determining the power failure time of each load node in the microgrid after each fault occurs according to a preset fault isolation strategy and a preset microgrid power interaction strategy.
As an embodiment of the present invention, as shown in fig. 2, S102 may include:
in S201, the elements in the time sequence list are sorted according to the smaller to larger failure repair time of each element.
In S202, the sorted elements are sequentially selected as the elements having a failure.
In S203, the power outage time of each load node in the microgrid after each fault occurs is determined according to a preset fault isolation policy and a preset microgrid power interaction policy.
In this embodiment, faults may be enumerated. According to TfThe repair time of all faults in the process is enumerated from small to large in sequence. And determining the power failure time of each load node in the microgrid after each fault occurs according to a preset fault isolation strategy and a preset microgrid power interaction strategy.
As an embodiment of the present invention, as shown in fig. 3, S203 may include:
in S301, for any fault, a fault point position, a fault type, and a fault affected zone of the fault in the microgrid are determined.
In S302, fault isolation processing is performed on any fault according to a preset fault isolation policy, and a load node affected by any fault is determined.
In S303, analyzing the operation status of the microgrid after the fault isolation processing according to a preset microgrid power interaction strategy, and determining the power failure time of each load node in the microgrid under the influence of any fault.
In the present embodiment, an example of analyzing one failure will be described. And for one selected fault, judging the position and the type of the fault point, and analyzing the area affected by the fault. And carrying out fault isolation operation according to a preset fault isolation strategy, and determining the load nodes affected by the fault. And analyzing the operation condition of the feeder line area after the fault is isolated, judging the power balance condition of the normal working area, determining whether load reduction is needed or not according to a preset micro-grid power interaction strategy, and determining a reduced load node. And determining the power failure time of all load nodes under the influence of the fault.
As an embodiment of the present invention, the preset fault isolation policy may include:
determining a corresponding fault isolation strategy according to the fault type;
if the fault type is a load region fault, disconnecting the circuit breaker or the intelligent switch in the upstream direction of the current flowing into the fault load region, disconnecting the isolating switch in the fault influence region, and overlapping the circuit breaker and the intelligent switch to enable the fault-free equipment of the microgrid to recover to normal operation;
if the fault type is a distributed power supply fault, an energy storage device fault or an electric vehicle charging station device fault, disconnecting an intelligent switch connected with a fault power supply;
and if the fault type is a line branch fault, disconnecting the circuit breaker or the intelligent switch in the upstream direction of the current flowing into the fault line branch region.
In this embodiment, when a fault occurs in the microgrid, in order to ensure continuous power utilization of other fault-free loads as much as possible, a switch in a network line is used for fault isolation. The operating conditions within the microgrid after a fault also are affected by the switching-off characteristics of the different types of switches and the position of the switching devices arranged in the network. As shown in fig. 4, the microgrid feed line area is classified by using switches as boundaries:
a primary area: the interior does not contain the smallest area of any type of switching device. The method comprises the following steps: the system comprises a load area with an isolating switch as a boundary, a distributed power system with an intelligent switch as a boundary, an energy storage device area and an EV charging station area with the intelligent switch as a boundary.
And (3) secondary area: the circuit breaker is used as a boundary, and other circuit breakers are not contained in the region. Generally, the same branch region is formed by combining a plurality of primary regions.
The distributed power supply is connected into the micro-grid system through the intelligent switch, and when the output of the distributed power supply is zero or fails, the intelligent switch acts to switch the power supply in order to prevent power backflow. The energy storage equipment and the EV charging station are connected into the microgrid through the intelligent switch, and when the equipment fails, the intelligent switch has the characteristic of a breaker to break the fault; when the energy storage device or the EV charging station discharges as the power supply characteristic, the downstream load or the line breaks down, the intelligent switch acts, and the discharging operation of the energy storage device or the EV charging station is blocked.
The types of faults that may occur within the campus microgrid contemplated by the present embodiments may include at least one of: distributed power failures, load failures, energy storage device failures, EV charging station failures, line device failures, and the like. As shown in fig. 4, the distributed power supply, the energy storage device, and the EV charging station are connected to each secondary area of the microgrid feeder in a distributed manner through the smart switch, so as to form a low-voltage power grid system with multiple power supplies and different access points. Therefore, after different types of faults occur in the microgrid, the switch action strategy and the influence of the faults on the operation of other loads or equipment of the microgrid can be analyzed as follows:
1) a fault occurs in the load zone bounded by the disconnector. Taking the load point LP2 as an example, the switching operation flow is as follows:
1 step: the upstream direction breaker or smart switch of the current flowing into the load region operates first, that is, the smart switch connected to the No. 2 and No. 4 breakers and DG1 in fig. 4 operates first. If the BAT1 is in a discharge state when a fault occurs, the connected intelligent switches are also simultaneously turned off.
2, step: after the current is blocked from flowing to the fault point, the isolating switch in the fault area is manually or automatically switched off to isolate the fault.
3 step: reclosing the breaker and the intelligent switch, and recovering normal operation of the fault-free equipment of the micro-grid.
The fault does not affect other secondary areas, and the power failure of other primary area loads and power equipment in the secondary area where the fault point is located is affected, and the power failure time is the on-off time of the isolating switch.
2) Distributed power supply faults, energy storage equipment faults and EV charging station faults with the intelligent switch as a boundary. Only the intelligent switch connected with the fault power supply is needed to be disconnected. For example, when BAT1 or DG1 in fig. 4 fails, the intelligent switch in the primary area where BAT1 or DG1 is located may be turned off.
After the fault occurs, the fault power supply is cut off, the total output of the system is reduced, and the operation of the micro-grid needs to be analyzed again according to a power interaction strategy in order to maintain the power balance of the system and the stability of the voltage and the frequency. If the energy storage device and the EV charging station are performing charging operation when a fault occurs, the connected intelligent switch is disconnected. Otherwise, the micro-grid power failure processing is carried out.
3) A line branch fault. The operation strategy is basically the same as that of the fault of the load point, and the operation of disconnecting the isolating switch is not needed after the current is blocked, and the breaker and the intelligent switch can not be switched on. If the line fault occurs in the line P in fig. 4, the circuit breakers 2 and 4 are opened, and the intelligent switch in the primary area where the DG1 is located is opened. If BAT1 is in discharge state when fault occurs, then the connected intelligent switch is disconnected. When the type of fault occurs, all loads of a secondary area where a fault point is located are powered off, all equipment stops running, and the power-off time is fault repairing time.
Based on the preset fault isolation strategy provided by the embodiment, the secondary region where the fault point is located can be isolated from other secondary regions after the fault occurs, the influence range of the fault is effectively limited, and the reliable operation of the micro-grid is improved. For the area with the fault isolated, the operating condition of the fault-free area of the microgrid needs to be analyzed by using the energy storage device provided by the embodiment in combination with the power interaction strategy of the EV charging station and the microgrid, and whether load reduction is needed in each area or not is judged, and relevant operations are performed.
As an embodiment of the present invention, the preset microgrid power interaction strategy includes:
judging the time period of the micro-grid island operation;
calculating grid-connected point exchange power P during micro-grid isolated island operationph(t)；
If Pph(t)>0, when the time period of the operation of the micro-grid island is a first time period, the micro-grid charges the energy storage equipment; if Pph(t)>0 and microgrid isolated island operationWhen the time interval of the row is the second time interval, the micro-grid firstly charges the energy storage equipment, and when the charge quantity in the energy storage equipment reaches the first preset value SOCbat·sdOr Pph(t)-Pbat·ch·max>When 0, charging the electric automobile in the electric automobile charging station;
if Pph(t)<0, when the time period of the operation of the micro-grid island is a first time period, the energy storage equipment performs discharging operation; if Pph(t)<0 and the time interval of the isolated island operation of the micro-grid is a third time interval, the micro-grid firstly enables the electric vehicle charging station equipment to carry out discharging operation, and when P isph(t)+PEV·dis(t)<0 takes the energy storage device into discharge operation, when Pph(t)+PEV·dis(t)+Pbat·dis·max<When 0, load reduction is carried out on the micro-grid;
wherein, Pbat·ch·maxFor maximum charging power of the energy storage device, Pbat·dis·maxIs the maximum discharge power, P, of the energy storage deviceEV·dis(t) is the discharge power of the electric vehicle charging station equipment;
the first time period is a time period when the electric automobile does not participate in micro-grid power interaction; the second time period is a time period when the electric automobile participates in micro-grid power interaction in a charging mode; and the third time period is a time period when the electric automobile participates in the micro-grid power interaction in a discharging mode.
In this embodiment, in the case of microgrid island operation, the balance between the renewable energy generated output and the load demand power inside the microgrid determines the power flow direction between the EV charging station and the microgrid system. Therefore, the power balance condition between the source charges in the microgrid can be analyzed as follows:
Pph(t)＝PG(t)-PL(t) (2)
wherein, PG(t)＝PWT(v)+PPV(t)；Pph(t) is the microgrid grid-connected point exchange power, PG(t) real-time generated Power of distributed Power, PL(t) is the real-time load power within the microgrid; pWT(v) For generating power, P, of wind-power generator setsPV(t) is lightAnd generating power by the photovoltaic generator set.
After the electric automobile is connected into the microgrid system, the electric automobile and the energy storage equipment have the same characteristics, and when the microgrid is operated in an isolated island mode, a combined energy storage system consisting of the energy storage equipment and the electric automobile is arranged, so that smooth distributed energy is output, and the stable operation level of the microgrid is improved. When the output power of the distributed energy generation in the microgrid is greater than the load demand, the system charges the energy storage equipment and the EV; when the generated power cannot meet the demand of the load, the energy storage device and the EV will perform a discharging operation to supply power to the load together with the distributed power supply. When the energy storage and EV charging stations can not meet the load requirements together with the distributed power supply, the system can sequentially reduce the load according to the important level of the load until the system stably operates.
Through analysis of private EV and electric regular bus running time characteristics in the microgrid, the participation of the electric automobile in the microgrid V2G is mainly divided into a charging period Tch(i.e., the second period) and a discharge period Tdis(i.e. the third period of time) two modes, wherein the period of time when the electric automobile does not participate in V2G is T1(i.e., the first period).
At working day TchAnd TdisWhen the micro-grid isolated island operates in a time period, the energy storage equipment and the EV charging station jointly perform power interaction with the micro-grid. Analyzing the power interaction condition between the energy storage equipment combined EV charging station and the microgrid in different time periods:
the first step is as follows: judging whether the micro-grid island operation period is TchOr TdisA time period;
the second step is that: calculating the power of the grid-connected point exchange when the micro-grid islanding operates, namely calculating Pph(t) value;
the third step: if Pph(t)>0. At T1During the time period, the microgrid will only charge the energy storage device. At TchIn time period, the micro-grid firstly charges the energy storage equipment, and when the charge quantity in the energy storage equipment reaches a certain set value SOCbat·sd(the value is set according to the principle that the charging requirement of the electric automobile is considered under the premise of ensuring the subsequent work of the energy storage equipment as much as possible) or Pph(t)-Pbat·ch·max>And 0, if the maximum input power of the energy storage equipment is still rich, charging the electric vehicle in the EV charging station. Therein, SOCbat·sdThe energy storage device may be maintained at a state of charge for maintaining subsequent system stability when the EV charging station is without an electric vehicle.
The fourth step: if Pph(t)<0. At T1And in the time interval, the energy storage device performs discharging operation. At TdisIn the time period, the micro-grid firstly arranges the electric automobile to perform the discharging operation. When P is presentph(t)+PEV·dis(t)<And 0, when the load demand cannot be met by the EV charging station and the renewable energy source, the energy storage device participates in the discharging operation. If Pph(t)+PEV·dis(t)+Pbat·dis·max<And 0, when the energy storage equipment, the EV charging station and the renewable energy source combined output cannot meet the load requirement, load reduction is required.
Optionally, the preset microgrid power interaction policy may further include:
establishing a charge and discharge power calculation model of the energy storage equipment; the charging and discharging power calculation model of the energy storage equipment comprises a charging power calculation model of the energy storage equipment in a second time period, a discharging power calculation model of the energy storage equipment in the second time period, a charging power calculation model of the energy storage equipment in a third time period and a discharging power calculation model of the energy storage equipment in the third time period;
the charging power calculation model of the energy storage device in the second period is as follows:
the discharge power calculation model of the energy storage device in the second period is as follows:
the charging power calculation model of the energy storage device in the third period is as follows:
the discharge power calculation model of the energy storage device in the third period is as follows:
wherein, Pbat·dis(t) discharge power of the energy storage device, Pbat·ch(t) charging Power, SOC, for energy storage devicesbatAnd (t) is the state of charge of the energy storage device.
In this embodiment, equations (3) to (6) represent charge and discharge power calculation models of the energy storage device in the microgrid in different periods and under different operating conditions of the microgrid in the park microgrid.
In S103, a reliability index including at least one of an average failure rate, an average failure time, and an average power outage time is calculated for each load node.
In this embodiment, the average failure rate λ of each load node may be calculated based on the power failure time of each load node in the microgrid after each failure occursiMean time to failure riAnnual average power failure time UiAnd waiting for reliability indexes.
In S104, a reliability index of the microgrid system is calculated from the reliability indexes of the load nodes.
According to the embodiment of the invention, aiming at the isolated island operation mode of the industrial park microgrid with an EV charging station, a sequential Monte Carlo simulation method is adopted, and the operation reliability of the park microgrid in the isolated island mode is evaluated according to the energy storage equipment in combination with a power interaction strategy between the EV charging station and the microgrid and a fault isolation strategy after internal fault in the microgrid in the isolated island state, so that the evaluation accuracy of the isolated island operation reliability of the industrial park microgrid with the EV charging station can be improved, the operation stability of the microgrid and the new energy acceptance capability are improved, and meanwhile, the unified scheduling of the distributed power supply by the power grid is facilitated.
As an implementation example of the present invention, the energy storage device provided in the embodiment of the present invention is used in combination with a power interaction policy between the EV charging station and the microgrid and a fault isolation policy after an internal fault occurs in the microgrid in an island state, so as to evaluate the operation reliability of the microgrid in the island. The specific evaluation process may be:
1) and (4) inputting parameters, setting an initial value T of the analog clock to be 0, and assuming that all elements are in a normal working state.
2) And respectively calculating the fault-free working time and the fault repairing time of each element in the network according to a formula (1) to obtain a time sequence table.
3) The faults are enumerated. According to TfThe repair time of all faults in the process is enumerated from small to large in sequence.
4) And analyzing the fault, judging the position and the type of the fault point, and analyzing the area affected by the fault.
5) And performing fault isolation operation according to the post-fault microgrid operation analysis method and the fault isolation strategy, and determining the load affected by the fault.
6) And analyzing the operation condition of the feeder line area after the fault is isolated, judging the power balance condition of the normal working area, determining whether load reduction needs to be carried out or not according to the energy storage equipment combined EV charging station and microgrid power interaction strategy, and determining the reduced load nodes.
7) The outage time for all loads under the influence of the fault is determined.
8) Judging whether the fault is the last fault in the given total time, if not, returning to the step 3); if yes, the next step is continued.
9) Calculating the mean failure rate lambda of each load pointiMean time to failure riAnnual average power failure time UiAnd waiting for reliability indexes.
10) And calculating each reliability index of the system according to the reliability index of each load point.
The embodiment innovatively provides a method for evaluating the operation reliability of a microgrid island containing an EV charging station by adopting a sequential Monte Carlo algorithm, innovatively provides a partition method for dividing a microgrid feeder line area into two stages by taking a switch as a boundary when the park microgrid island containing the EV charging station operates, and provides a charging and discharging power calculation model of energy storage equipment in the park microgrid.
According to the embodiment of the invention, aiming at the isolated island operation mode of the industrial park microgrid with an EV charging station, a sequential Monte Carlo simulation method is adopted, and the operation reliability of the park microgrid in the isolated island mode is evaluated according to the energy storage equipment in combination with a power interaction strategy between the EV charging station and the microgrid and a fault isolation strategy after internal fault in the microgrid in the isolated island state, so that the evaluation accuracy of the isolated island operation reliability of the industrial park microgrid with the EV charging station can be improved, the operation stability of the microgrid and the new energy acceptance capability are improved, and meanwhile, the unified scheduling of the distributed power supply by the power grid is facilitated.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
Corresponding to the method for evaluating the operation reliability of the microgrid island, fig. 5 is a schematic diagram of a device for evaluating the operation reliability of the microgrid island, provided by the embodiment of the present invention. For convenience of explanation, only the portions related to the present embodiment are shown.
Referring to fig. 5, the apparatus includes an acquisition module 51, a processing module 52, a first calculation module 53, and a second calculation module 54.
The obtaining module 51 is configured to obtain a fault rate and a fault repair rate of each element in the microgrid, and calculate a fault-free working time and a fault repair time of each element according to the fault rate and the fault repair rate of each element to obtain a time sequence table.
The processing module 52 is configured to analyze the operation conditions of the microgrid after the elements in the time sequence table have a fault according to a preset fault isolation policy and a preset microgrid power interaction policy, and determine power failure time of each load node in the microgrid after each fault occurs; the preset power interaction strategy of the micro point network is a power interaction strategy combining energy storage equipment, electric vehicle charging station equipment and a distributed power supply in the micro grid.
The first calculating module 53 is configured to calculate a reliability indicator of each load node, where the reliability indicator includes at least one of an average failure rate, an average failure time, and an average power failure time.
And the second calculating module 54 is configured to calculate a reliability index of the microgrid system according to the reliability index of each load node.
Optionally, the obtaining module 51 is configured to
Calculating the fault-free working time and fault repair time of each element according to the first calculation formula, the fault rate and the fault repair rate of each element; the first calculation formula is:
TTFi＝-(1/λi)·lnu
TTRi＝-(1/μi)·lnu
wherein, TTFiFor the fault-free working time of the ith element, λiFailure rate of the ith element; TTRiTime to failure repair of ith element, muiThe failure repair rate of the ith element; u is a random number between (0,1) subject to uniform distribution.
Optionally, the processing module 52 is configured to:
sorting the elements in the time sequence list according to the fault repair time of each element from small to large;
sequentially selecting the sequenced elements as elements with faults;
and determining the power failure time of each load node in the microgrid after each fault occurs according to a preset fault isolation strategy and a preset microgrid power interaction strategy.
Optionally, the processing module 52 is configured to:
for any fault, judging the position, type and area of fault influence of the fault in the microgrid;
carrying out fault isolation processing on any fault according to a preset fault isolation strategy, and determining a load node influenced by any fault;
analyzing the operation condition of the micro-grid after the fault isolation processing according to a preset micro-grid power interaction strategy, and determining the power failure time of each load node in the micro-grid under the influence of any fault.
Optionally, the preset fault isolation policy includes:
determining a corresponding fault isolation strategy according to the fault type;
if the fault type is a load region fault, disconnecting the circuit breaker or the intelligent switch in the upstream direction of the current flowing into the fault load region, disconnecting the isolating switch in the fault influence region, and overlapping the circuit breaker and the intelligent switch to enable the fault-free equipment of the microgrid to recover to normal operation;
if the fault type is a distributed power supply fault, an energy storage device fault or an electric vehicle charging station device fault, disconnecting an intelligent switch connected with a fault power supply;
and if the fault type is a line branch fault, disconnecting the circuit breaker or the intelligent switch in the upstream direction of the current flowing into the fault line branch region.
Optionally, the preset microgrid power interaction strategy includes:
judging the time period of the micro-grid island operation;
calculating grid-connected point exchange power P during micro-grid isolated island operationph(t)；
If Pph(t)>0, when the time period of the operation of the micro-grid island is a first time period, the micro-grid charges the energy storage equipment; if Pph(t)>0, when the time period of the isolated island operation of the micro-grid is a second time period, the micro-grid firstly charges the energy storage equipment, and when the electric charge quantity in the energy storage equipment reaches a first preset value SOCbat·sdOr Pph(t)-Pbat·ch·max>When 0, charging the electric automobile in the electric automobile charging station;
if Pph(t)<0, when the time period of the operation of the micro-grid island is a first time period, the energy storage equipment performs discharging operation; if Pph(t)<0, if the time interval of the isolated island operation of the micro-grid is the third time interval, the micro-grid firstly charges the electric automobileThe power station performs discharge operation when Pph(t)+PEV·dis(t)<0 takes the energy storage device into discharge operation, when Pph(t)+PEV·dis(t)+Pbat·dis·max<When 0, load reduction is carried out on the micro-grid;
wherein, Pbat·ch·maxFor maximum charging power of the energy storage device, Pbat·dis·maxIs the maximum discharge power, P, of the energy storage deviceEV·dis(t) is the discharge power of the electric vehicle charging station equipment;
the first time period is a time period when the electric automobile does not participate in micro-grid power interaction; the second time period is a time period when the electric automobile participates in micro-grid power interaction in a charging mode; and the third time period is a time period when the electric automobile participates in the micro-grid power interaction in a discharging mode.
Optionally, the preset microgrid power interaction strategy includes:
establishing a charge and discharge power calculation model of the energy storage equipment; the charging and discharging power calculation model of the energy storage equipment comprises a charging power calculation model of the energy storage equipment in a second time period, a discharging power calculation model of the energy storage equipment in the second time period, a charging power calculation model of the energy storage equipment in a third time period and a discharging power calculation model of the energy storage equipment in the third time period;
the charging power calculation model of the energy storage device in the second period is as follows:
the discharge power calculation model of the energy storage device in the second period is as follows:
the charging power calculation model of the energy storage device in the third period is as follows:
the discharge power calculation model of the energy storage device in the third period is as follows:
wherein, Pbat·dis(t) discharge power of the energy storage device, Pbat·ch(t) charging Power, SOC, for energy storage devicesbatAnd (t) is the state of charge of the energy storage device.
According to the embodiment of the invention, aiming at the isolated island operation mode of the industrial park microgrid with an EV charging station, a sequential Monte Carlo simulation method is adopted, and the operation reliability of the park microgrid in the isolated island mode is evaluated according to the energy storage equipment in combination with a power interaction strategy between the EV charging station and the microgrid and a fault isolation strategy after internal fault in the microgrid in the isolated island state, so that the evaluation accuracy of the isolated island operation reliability of the industrial park microgrid with the EV charging station can be improved, the operation stability of the microgrid and the new energy acceptance capability are improved, and meanwhile, the unified scheduling of the distributed power supply by the power grid is facilitated.
Fig. 6 is a schematic diagram of a terminal device according to an embodiment of the present invention. As shown in fig. 6, the terminal device 6 of this embodiment includes: a processor 60, a memory 61 and a computer program 62, e.g. a program, stored in said memory 61 and executable on said processor 60. The processor 60, when executing the computer program 62, implements the steps in the various method embodiments described above, such as the steps 101 to 104 shown in fig. 1. Alternatively, the processor 60, when executing the computer program 62, implements the functions of the modules/units in the above-mentioned device embodiments, such as the functions of the modules 51 to 54 shown in fig. 5.
Illustratively, the computer program 62 may be partitioned into one or more modules/units that are stored in the memory 61 and executed by the processor 60 to implement the present invention. The one or more modules/units may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution of the computer program 62 in the terminal device 6.
The terminal device 6 may be a desktop computer, a notebook, a palm computer, a cloud server, or other computing devices. The terminal device may include, but is not limited to, a processor 60, a memory 61. Those skilled in the art will appreciate that fig. 6 is merely an example of a terminal device 6, and does not constitute a limitation of the terminal device 6, and may include more or less components than those shown, or some components in combination, or different components, for example, the terminal device may also include an input-output device, a network access device, a bus, a display, etc.
The Processor 60 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory 61 may be an internal storage unit of the terminal device 6, such as a hard disk or a memory of the terminal device 6. The memory 61 may also be an external storage device of the terminal device 6, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), and the like, which are provided on the terminal device 6. Further, the memory 61 may also include both an internal storage unit and an external storage device of the terminal device 6. The memory 61 is used for storing the computer program and other programs and data required by the terminal device. The memory 61 may also be used to temporarily store data that has been output or is to be output.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of the functional units and modules is illustrated, and in practical applications, the above-mentioned function distribution may be performed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-mentioned functions. Each functional unit and module in the embodiments may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit, and the integrated unit may be implemented in a form of hardware, or in a form of software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working processes of the units and modules in the system may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to the related descriptions of other embodiments for parts that are not described or illustrated in a certain embodiment.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus/terminal device and method may be implemented in other ways. For example, the above-described embodiments of the apparatus/terminal device are merely illustrative, and for example, the division of the modules or units is only one logical division, and there may be other divisions when actually implemented, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated modules/units, if implemented in the form of software functional units and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like. It should be noted that the computer readable medium may contain other components which may be suitably increased or decreased as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, computer readable media which may not include electrical carrier signals and telecommunications signals in accordance with legislation and patent practice.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.
Claims (8)
1. A micro-grid island operation reliability assessment method is characterized by comprising the following steps:
acquiring the fault rate and the fault repair rate of each element in the microgrid, and calculating the fault-free working time and the fault repair time of each element according to the fault rate and the fault repair rate of each element to obtain a time sequence table;
sorting the elements in the time sequence list according to the fault repair time of each element from small to large; sequentially selecting the sequenced elements as elements with faults; for any fault, judging the position, type and area of fault influence of the fault in the microgrid; carrying out fault isolation processing on any fault according to a preset fault isolation strategy, and determining a load node influenced by any fault; analyzing the operation condition of the micro-grid after the fault isolation processing according to a preset micro-grid power interaction strategy, and determining the power failure time of each load node in the micro-grid under the influence of any fault;
the preset micro-grid power interaction strategy is a power interaction strategy combining energy storage equipment, electric vehicle charging station equipment and a distributed power supply in a micro-grid; the micro-grid feeder line area is divided into a primary area and a secondary area in a grading way by taking the switch as a boundary; the primary area is the minimum area without any type of switching device inside; the secondary area is an area which takes the breaker as a boundary and does not contain other breakers; the preset fault isolation strategy is a strategy for isolating a secondary area where a fault point is located from other secondary areas after a fault occurs;
calculating the reliability index of each load node; the reliability index comprises at least one of average fault rate, average fault time and average power failure time;
and calculating the reliability index of the micro-grid system according to the reliability index of each load node.
2. The microgrid island operation reliability evaluation method of claim 1, wherein the calculating of the fault-free operating time and the fault repair time of each element according to the fault rate and the fault repair rate of each element comprises:
calculating the fault-free working time and fault repair time of each element according to the first calculation formula, the fault rate and the fault repair rate of each element; the first calculation formula is:
TTFi＝-(1/λi)·lnu
TTRi＝-(1/μi)·lnu
wherein, TTFiFor the fault-free working time of the ith element, λiFailure rate of the ith element; TTRiTime to failure repair of ith element, muiThe failure repair rate of the ith element; u is a random number between (0,1) subject to uniform distribution.
3. The microgrid island operation reliability assessment method according to claim 1, wherein the preset fault isolation strategy comprises:
determining a corresponding fault isolation strategy according to the fault type;
if the fault type is a load region fault, disconnecting the circuit breaker or the intelligent switch in the upstream direction of the current flowing into the fault load region, disconnecting the isolating switch in the fault influence region, and overlapping the circuit breaker and the intelligent switch to enable the fault-free equipment of the microgrid to recover to normal operation;
if the fault type is a distributed power supply fault, an energy storage device fault or an electric vehicle charging station device fault, disconnecting an intelligent switch connected with a fault power supply;
and if the fault type is a line branch fault, disconnecting the circuit breaker or the intelligent switch in the upstream direction of the current flowing into the fault line branch region.
4. The microgrid island operation reliability assessment method according to any one of claims 1 to 3, wherein the preset microgrid power interaction strategy comprises:
judging the time period of the micro-grid island operation;
calculating grid-connected point exchange power P during micro-grid isolated island operationph(t)；
If Pph(t)>0, when the time period of the operation of the micro-grid island is a first time period, the micro-grid charges the energy storage equipment; if Pph(t)>0, when the time period of the isolated island operation of the micro-grid is a second time period, the micro-grid firstly charges the energy storage equipment, and when the electric charge quantity in the energy storage equipment reaches a first preset value SOCbat·sdOr Pph(t)-Pbat·ch·max>When 0, charging the electric automobile in the electric automobile charging station;
if Pph(t)<0, when the time period of the operation of the micro-grid island is a first time period, the energy storage equipment performs discharging operation; if Pph(t)<0 and the time interval of the isolated island operation of the micro-grid is a third time interval, the micro-grid firstly enables the electric vehicle charging station equipment to carry out discharging operation, and when P isph(t)+PEV·dis(t)<0 takes the energy storage device into discharge operation, when Pph(t)+PEV·dis(t)+Pbat·dis·max<When 0, load reduction is carried out on the micro-grid;
wherein, Pbat·ch·maxFor maximum charging power of the energy storage device, Pbat·dis·maxIs the maximum discharge power, P, of the energy storage deviceEV·dis(t) is the discharge power of the electric vehicle charging station equipment;
the first time period is a time period when the electric automobile does not participate in micro-grid power interaction; the second time period is a time period when the electric automobile participates in micro-grid power interaction in a charging mode; and the third time period is a time period when the electric automobile participates in the micro-grid power interaction in a discharging mode.
5. The microgrid island operation reliability assessment method of claim 4, wherein the preset microgrid power interaction strategy comprises:
establishing a charge and discharge power calculation model of the energy storage equipment; the charging and discharging power calculation model of the energy storage equipment comprises a charging power calculation model of the energy storage equipment in a second time period, a discharging power calculation model of the energy storage equipment in the second time period, a charging power calculation model of the energy storage equipment in a third time period and a discharging power calculation model of the energy storage equipment in the third time period;
the charging power calculation model of the energy storage device in the second period is as follows:
the discharge power calculation model of the energy storage device in the second period is as follows:
the charging power calculation model of the energy storage device in the third period is as follows:
the discharge power calculation model of the energy storage device in the third period is as follows:
wherein, Pbat·dis(t) discharge power of the energy storage device, Pbat·ch(t) charging Power, SOC, for energy storage devicesbatAnd (t) is the state of charge of the energy storage device.
6. A microgrid island operation reliability assessment device is characterized by comprising:
the acquisition module is used for acquiring the fault rate and the fault repair rate of each element in the microgrid, and calculating the fault-free working time and the fault repair time of each element according to the fault rate and the fault repair rate of each element to obtain a time sequence table;
the processing module is used for sequencing the elements in the time sequence list from small to large according to the fault repair time of the elements; sequentially selecting the sequenced elements as elements with faults; for any fault, judging the position, type and area of fault influence of the fault in the microgrid; carrying out fault isolation processing on any fault according to a preset fault isolation strategy, and determining a load node influenced by any fault; analyzing the operation condition of the micro-grid after the fault isolation processing according to a preset micro-grid power interaction strategy, and determining the power failure time of each load node in the micro-grid under the influence of any fault; the preset micro-grid power interaction strategy is a power interaction strategy combining energy storage equipment, electric vehicle charging station equipment and a distributed power supply in a micro-grid; the micro-grid feeder line area is divided into a primary area and a secondary area in a grading way by taking the switch as a boundary; the primary area is the minimum area without any type of switching device inside; the secondary area is an area which takes the breaker as a boundary and does not contain other breakers; the preset fault isolation strategy is a strategy for isolating a secondary area where a fault point is located from other secondary areas after a fault occurs;
the first calculation module is used for calculating the reliability index of each load node, and the reliability index comprises at least one of average failure rate, average failure time and average power failure time;
and the second calculation module is used for calculating the reliability index of the micro-grid system according to the reliability index of each load node.
7. A terminal device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the steps of the method according to any of claims 1 to 5 when executing the computer program.
8. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 5.
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| CN111682550B (en) * | 2020-06-18 | 2022-04-01 | 国网山东省电力公司德州供电公司 | Reliability evaluation method for power distribution network connected with high-permeability power supply and electric automobile |
| CN112053032A (en) * | 2020-08-05 | 2020-12-08 | 上海工程技术大学 | Micro-grid reliability evaluation method based on load change |
| CN113141025B (en) * | 2021-04-26 | 2022-11-25 | 河北工业大学 | Reliability evaluation method for island type alternating current-direct current hybrid micro-grid system containing EHS |
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