CN110581553A - Off-grid autonomous operation method and device for micro-grid system and micro-grid system - Google Patents
Off-grid autonomous operation method and device for micro-grid system and micro-grid system Download PDFInfo
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- CN110581553A CN110581553A CN201910918504.4A CN201910918504A CN110581553A CN 110581553 A CN110581553 A CN 110581553A CN 201910918504 A CN201910918504 A CN 201910918504A CN 110581553 A CN110581553 A CN 110581553A
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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
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
Abstract
the embodiment of the invention discloses an off-grid autonomous operation method and device for a micro-grid system and the micro-grid system, wherein the method comprises the following steps: a safe operation strategy of the micro-grid system is established in advance according to each load branch, each distributed power supply and a main energy storage converter in the micro-grid system; if the micro-grid system is in an off-grid state, controlling the micro-grid system to execute a safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system; and if the micro-grid system is in a grid-connected state, constantly monitoring the state of the micro-grid system, and controlling the micro-grid system to execute a safe operation strategy to realize the off-grid autonomous operation of the micro-grid system when the micro-grid system is converted from the grid-connected state to the off-grid state. After the micro-grid system is put into operation, the load condition of the micro-grid system is monitored in real time through the pre-established safe operation strategy, and the load or the distributed power supply needing to be disconnected is adjusted, so that the micro-grid can normally work to realize the autonomous operation of the off-grid when the off-grid state or the grid connection is converted into the off-grid state.
Description
Technical Field
The invention relates to the technical field of power grids, in particular to an off-grid autonomous operation method and device for a micro-grid system and the micro-grid system.
background
With the rapid development of renewable energy power generation technologies such as photovoltaic power generation and wind power generation, the proportion of the distributed renewable energy power generation to the microgrid is higher and higher. Although the distributed renewable energy has the characteristics of cleanness, no pollution and the like, the defects of the distributed renewable energy are not ignored: the centralization is reflected in high access cost, difficult control, uncertain output and the like. In order to reduce the impact of the distributed power supply on a large power grid, most countries originally stipulate that the distributed power supply must be immediately shut down when a power system fails, which greatly limits the operating efficiency of the distributed power supply. In addition, based on the passive radial operation structure of the current microgrid, the distributed power supply must be incorporated and operated in the form of load, that is, the power generation amount must be smaller than the load of the installed users, which results in that the power generation capacity of the distributed power supply is greatly limited structurally.
at present, although the interconnection between energy devices in a microgrid has no problem, the integration mode still has a larger optimization space. Specifically, most energy devices still operate by themselves after being connected, for example, a random micro power supply works in a Maximum Power Point Tracking (MPPT) mode for a long time and is not linked with an energy storage device, so that the micro power grid as a whole cannot control power interaction with a large power grid; the energy storage equipment fixedly sets fixed charging and discharging power according to time periods, and the power price peak-valley registration force is insufficient; when the microgrid runs off the grid and meets the conditions of energy storage over-discharge or over-charge, the microgrid can only be shut down in the whole grid, and the microgrid cannot be automatically adjusted in advance to avoid the risk of shutdown; in the self-starting process after the micro-grid is stopped, the load branches can only be started according to a set sequence, and the risk of energy storage overload and stopping again during starting may exist. Therefore, how to solve the problems of safe, stable, economic and autonomous operation of the micro-grid is a main target of the current micro-grid centralized control.
Disclosure of Invention
In view of this, embodiments of the present invention provide an off-grid autonomous operation method and apparatus for a microgrid system, and the microgrid system, after the microgrid system is put into operation, load conditions of the microgrid system are monitored in real time and loads or distributed power supplies that need to be disconnected are adjusted through a pre-established safe operation policy, so that the microgrid in an off-grid state can normally work to implement the off-grid autonomous operation.
On one hand, the embodiment of the invention provides an off-grid autonomous operation method of a micro-grid system, which comprises the following steps:
Pre-establishing a safe operation strategy of the micro-grid system according to each load branch, each distributed power supply and a main energy storage converter in the micro-grid system;
judging the running state of the micro-grid system;
If the micro-grid system is in an off-grid state, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system;
If the micro-grid system is in a grid-connected state, judging whether the micro-grid system currently receives a passive off-grid signal or an active off-grid signal;
if the micro-grid system currently receives a passive off-grid signal, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system;
and if the micro-grid system currently receives the active off-grid signal, adjusting the power value of the grid-connected point to be zero, and then controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system.
on the other hand, the embodiment of the invention provides an off-grid autonomous operation device of a micro-grid system, which comprises the following components:
the strategy establishing unit is used for pre-establishing a safe operation strategy of the micro-grid system according to each load branch, each distributed power supply and the main energy storage converter in the micro-grid system;
the first judgment unit is used for judging the operation state of the microgrid system;
the first control unit is used for controlling the micro-grid system to execute the safe operation strategy to realize the off-grid autonomous operation of the micro-grid system if the micro-grid system is in an off-grid state;
The second judgment unit is used for judging whether the micro-grid system currently receives a passive off-grid signal or an active off-grid signal if the micro-grid system is in a grid-connected state;
the second control unit is used for controlling the micro-grid system to execute the safe operation strategy to realize the off-grid autonomous operation of the micro-grid system if the micro-grid system currently receives a passive off-grid signal;
and the third control unit is used for adjusting the power value of the grid-connected point to be zero if the micro-grid system currently receives the active off-grid signal, and then controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system.
In another aspect, an embodiment of the present invention further provides a microgrid system, which is mainly composed of a main current energy storage converter, a load branch and a distributed power supply, and is characterized in that the microgrid system operates in an off-grid autonomous operation method using the microgrid system as described above.
the embodiment of the invention provides an off-grid autonomous operation method and device for a micro-grid system and the micro-grid system, wherein the method comprises the following steps: the method comprises the steps that a safe operation strategy of the micro-grid system is established in advance according to each load branch, each distributed power supply and a main energy storage converter in the micro-grid system; if the micro-grid system is in an off-grid state, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system; and if the micro-grid system is in a grid-connected state, constantly monitoring the state of the micro-grid system, and controlling the micro-grid system to execute the safe operation strategy to realize the off-grid autonomous operation of the micro-grid system when the micro-grid system is converted from the grid-connected state to the off-grid state. After the micro-grid system is put into operation, the load condition of the micro-grid system is monitored in real time through the pre-established safe operation strategy, and the load or the distributed power supply needing to be disconnected is adjusted, so that the micro-grid can normally work to realize the autonomous operation of the off-grid under the off-grid state or when the grid is connected to the off-grid state.
drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are 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 creative efforts.
Fig. 1 is a schematic flow chart of an off-grid autonomous operation method of a microgrid system according to an embodiment of the present invention;
FIG. 2 is another schematic flow chart of an off-grid autonomous operation method for a microgrid system according to an embodiment of the present invention;
FIG. 3 is another schematic flow chart of a method for autonomous off-grid operation of a microgrid system according to an embodiment of the present invention;
FIG. 4 is another schematic flow chart of a method for autonomous off-grid operation of a microgrid system according to an embodiment of the present invention;
FIG. 5 is a schematic block diagram of an off-grid autonomous operation apparatus of a microgrid system according to an embodiment of the present invention;
FIG. 6 is another schematic block diagram of an off-grid autonomous operation apparatus for a microgrid system provided by an embodiment of the present invention;
FIG. 7 is another schematic block diagram of an off-grid autonomous operation apparatus for a microgrid system provided by an embodiment of the present invention;
fig. 8 is another schematic block diagram of an off-grid autonomous operation apparatus of a microgrid system according to an embodiment of the present invention.
Detailed Description
the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
it will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
Referring to fig. 1, fig. 1 is a schematic flow chart of an off-grid autonomous operation method of a microgrid system according to an embodiment of the present invention. As shown in fig. 1, the method includes the following steps S101 to S106.
S101, a safe operation strategy of the micro-grid system is established in advance according to each load branch, each distributed power supply and a main energy storage converter in the micro-grid system.
In the embodiment of the invention, when the micro-grid system is put into operation formally, a safe operation strategy of the micro-grid system is established in advance according to the working conditions of each load branch, each distributed power supply and the main energy storage converter in the micro-grid system, and the safe operation strategy is used for indicating how the micro-grid system realizes autonomous normal operation when the micro-grid system is in an off-grid state, so that the condition that the micro-grid system stops operation can not occur.
In an embodiment, as shown in fig. 2, in order to enable the microgrid system to operate autonomously and normally in an off-grid state, the specific step of establishing a safe operation strategy of the microgrid system in advance according to each load branch, each distributed power supply and a main energy storage converter in the microgrid system includes:
step one, acquiring the power value of each load branch in the micro-grid system and the power value of each distributed power supply.
Specifically, the power value of each load branch in the microgrid system is read, the power value of each load branch is recorded as Pload _ i, the power value of each distributed power supply in the microgrid system is read, and the power value of each distributed power supply is recorded as Pgen _ j.
And step two, sequencing the load branches and the distributed power supplies respectively according to the sequence of the power values from large to small.
specifically, in this step, the load branches and the distributed power supplies need to be sequenced, after the power value Pload _ i of each load branch and the power value Pgen _ j of each distributed power supply are read in the first step, the power value Pload _ i of each load branch and the power value Pgen _ j of each distributed power supply are sequenced according to the sequence of the power values from large to small, and in this step, after the sequencing is completed, the load branches and the distributed power supplies can be numbered according to the sequence of the power values from large to small.
And step three, adding the power values of the load branches to obtain a total power value of the load, and adding the power values of the distributed power supplies to obtain a total power value of the distributed power supplies.
specifically, after the sorting is completed, the sum of the power values of all the load branches and the power value of each distributed power source are calculated, where the total power value of the load may be Pload, which is Σ Pload _ i, and the total power value of the distributed power source may be Pgen, which is Σ Pgen _ j.
And fourthly, subtracting the total power value of the distributed power supply from the total power value of the load, respectively comparing a first difference value of the algebraic difference obtained by subtracting with the maximum charging power of the main energy storage converter of the micro-grid system and the maximum discharging power of the main energy storage converter of the micro-grid system, if the first difference value of the algebraic difference is larger than the maximum charging power of the main energy storage converter or smaller than the maximum discharging power of the main energy storage converter, selecting the load branch or the distributed power supply with the minimum power value from each load branch or each distributed power supply in sequence, and controlling the selected load branch or the distributed power supply with the minimum power value to be disconnected from the micro-grid system.
Specifically, the main energy storage converter of the microgrid system comprises two numbers, namely maximum charging power (namely Pcharge _ max) and maximum discharging power (namely Pdischarge _ max), wherein the maximum charging power refers to a maximum power value when the main energy storage converter allows charging, the maximum discharging power refers to a maximum power value when the main energy storage converter allows discharging, the total power value of the distributed power supply is subtracted from the total power value of the load to obtain a first difference value of an algebraic difference, namely Pgen-Pload, the first difference value of the algebraic difference is compared with the maximum charging power of the main energy storage converter of the microgrid system and the maximum discharging power of the main energy storage converter of the microgrid system, and if the obtained first difference value of the algebraic difference is greater than the maximum charging power of the main energy storage converter or less than the maximum discharging power of the main energy storage converter, namely Pgen-Pload > Pcharge _ max or Pgen-Pload < Pdischarge _ max, it indicates that the maximum charging/discharging power value of the main energy storage converter in the microgrid system under the condition of allowing charging/discharging cannot meet the normal working power of each load branch and each distributed power supply in the microgrid system, and the microgrid system cannot normally operate as a result. Therefore, in order to enable the maximum charging/discharging power value of the main energy storage converter under the condition of allowing charging/discharging to be enough to support the normal working power of each load branch and each distributed power supply in the microgrid system, and the microgrid system can normally operate, the load branches or the distributed power supplies in the microgrid system need to be cut down, in this case, the specific method of the embodiment is to sequentially select the load branch or the distributed power supply with the minimum power value from the load branches or the distributed power supplies, and control the selected load branch or the distributed power supply with the minimum power value to be cut off from the microgrid system so as to complete the cutting down of the load branch or the distributed power supply in the microgrid system, and after the selected load branch or the distributed power supply with the minimum power value is cut off from the microgrid system each time, the first difference of the algebraic difference between the total power value of the distributed power sources in the current microgrid system and the total power of the loads is calculated again, and if the first difference of the algebraic difference obtained by recalculation is larger than or equal to the maximum discharge power of the main energy storage converter and smaller than or equal to the maximum charge power of the main energy storage converter, namely Pdcharge _ max (Pgen-Pload) < (Pcharge _ max), it is indicated that the maximum charge/discharge power value of the main energy storage converter under the condition of allowing charge/discharge is enough to support the normal working power of each load branch and each distributed power source in the microgrid system, and the microgrid system can normally run, so that each load branch and each distributed power source do not need to be reduced again.
And step five, judging whether the first difference value of the algebraic difference is larger than the maximum charging power of the main energy storage converter or smaller than the maximum discharging power of the main energy storage converter, if so, continuing to execute the step four, and if not, executing the step six.
And step six, recording all load branches and all distributed power supplies disconnected from the micro-grid system as a safety operation strategy of the micro-grid system.
Specifically, if the first difference of the algebraic differences obtained by calculation is greater than or equal to the maximum discharge power of the main energy storage converter and less than or equal to the maximum charge power of the main energy storage converter, that is, Pdischarge _ max ═ Pgen-Pload ═ Pcharge _ max, it is indicated that the maximum charge/discharge power value of the main energy storage converter under the charging/discharging permission condition is sufficient to support the normal working power of each load branch and each distributed power supply in the microgrid system, and the microgrid system can normally operate, so that all load branches and all distributed power supplies disconnected from the microgrid system are recorded, that is, all load branches or distributed power supplies cut down from the microgrid system are recorded. And finally, taking the recorded content as a safe operation strategy of the micro-grid system, and when the micro-grid system is in an off-grid state, executing the established safe operation strategy to cut load branches or distributed power supplies from the micro-grid system, so that the micro-grid system can normally operate in the off-grid state.
And S102, judging the running state of the micro-grid system.
In the embodiment of the invention, the operation states of the microgrid system comprise an off-grid state and a grid-connected state, wherein the off-grid state can be roughly divided into the following cases: the method comprises the following steps that an artificial active off-grid operation causes an off-grid state of the micro-grid system, a large grid does not supply power, the micro-grid system is caused to be off-grid, and a grid-connected off-grid switch indicates the off-grid state, so that the micro-grid system is caused to be off-grid, wherein the grid-connected state is specifically the following conditions: and when the off-grid switch indicates grid connection and the large power grid normally supplies power, the micro-grid system is in a grid connection state.
S103, if the micro-grid system is in an off-grid state, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system.
In the embodiment of the invention, if the microgrid system is in an off-grid state, the microgrid system is controlled to execute the safe operation strategy, namely the recorded load branches or distributed power supplies are cut off from the microgrid system according to the pre-established safe operation strategy, so that the maximum power value of the main energy storage converter under the condition of allowing charging/discharging is enough to support the normal working power of each load branch and each distributed power supply in the microgrid system, and the microgrid system can normally operate.
and S104, if the micro-grid system is in a grid-connected state, judging whether the micro-grid system currently receives a passive off-grid signal or an active off-grid signal.
In the embodiment of the invention, when the microgrid system is converted from the grid-connected state to the off-grid state, the following two conditions are generally included: active off-grid or passive off-grid; for the active off-grid condition, the micro-grid system needs to receive an active off-grid signal, the active off-grid signal is generally generated by artificial active off-grid operation, and the active off-grid signal comprises an artificial active off-grid instruction; for the passive off-grid condition, the large power grid does not supply power to the micro-grid system, when the large power grid does not supply power, a main energy storage converter in the micro-grid system receives a passive off-grid signal, the passive off-grid signal is generally generated by the large power grid without supplying power, and the passive off-grid signal comprises an off-grid instruction when the micro-grid fails to supply power.
And S105, if the micro-grid system currently receives the passive off-grid signal, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system.
in the embodiment of the invention, if the microgrid system receives a passive off-grid signal currently, it is indicated that the large power grid supplying power to the microgrid system does not supply power, the current microgrid system is converted from a grid-connected state to an off-grid state, and in the off-grid state, the microgrid system is controlled to execute the safe operation strategy, that is, the recorded load branches or distributed power supplies are cut off from the microgrid system according to the pre-established safe operation strategy, so that the maximum charging/discharging power value of the main energy storage converter under the condition of allowing discharging/charging is enough to support the normal working power of each load branch and each distributed power supply in the microgrid system, and the microgrid system can normally operate.
S106, if the micro-grid system receives the active off-grid signal currently, adjusting the power value of the grid-connected point to be zero, and then controlling the micro-grid system to execute the safe operation strategy to realize the off-grid autonomous operation of the micro-grid system.
In the embodiment of the invention, if the micro-grid system receives an active off-grid signal currently, it is indicated that the artificial active off-grid operation causes the micro-grid system to be in an off-grid state, but due to the particularity of the active off-grid operation, the power supply of the large power grid is normally performed at the moment, in order to ensure that the micro-grid system is converted from a grid-connected state to an off-grid state under the active off-grid operation and to eliminate the influence of the power supply of the large power grid, the interior of the micro-grid system needs to be adjusted so that the power value of a grid-connected point between the micro-grid system and the large power grid is equal to zero, so that the interior of the micro-grid system can reach power supply balance and get rid of the power supply influence of the large power grid, the micro-grid system is converted from the grid-connected state to the off-grid state under the active, and the recorded load branches or distributed power supplies are cut off from the micro-grid system, so that the maximum charging/discharging power value of the main energy storage converter under the condition of allowing discharging/charging is enough to support the normal working power of each load branch and each distributed power supply in the micro-grid system, and the micro-grid system can normally run.
In one embodiment, as shown in fig. 3, the specific operation of adjusting the grid-connected point power value to be equal to zero includes the following steps S202 to S204:
S202, subtracting the total power value of the distributed power supply in the micro-grid system from the total power value of the load, and acquiring a second difference value of the algebraic difference obtained by subtracting.
specifically, the calculated total power value Pgen of the distributed power source in the microgrid system is subtracted from the total power value Pload of the load, and a second difference value of the algebraic difference obtained by the subtraction, namely Pgen-Pload, is obtained.
and S204, controlling the power value of the main energy storage converter of the micro-grid system to be equal to a second difference value of an algebraic difference obtained by subtracting the total power value of the distributed power supply and the total power value of the load branch.
Specifically, under the normal working condition of the main energy storage converter of the micro-grid system, the power value P _ pcs _ set of the main energy storage converter of the micro-grid system is adjusted to be equal to a second difference value of an algebraic difference obtained by subtracting a total power value of a distributed power supply and a total power value of a load branch, namely P _ pcs _ set is Pgen-Pload, so that power supply balance inside the micro-grid system is achieved, the influence of power supply of the large grid is eliminated, and the micro-grid system is enabled to be converted into an off-grid state from a grid-connected state under the active off-grid operation.
More specifically, if the power value P _ pcs _ set of the main energy storage converter of the microgrid system is adjusted under the condition that the main energy storage converter of the microgrid system normally works, the power value of the main energy storage converter of the microgrid system cannot be made to be equal to a second difference value of an algebraic difference obtained by subtracting a total power value of a distributed power supply and a total power value of a load branch, the current grid-connected state of the microgrid system is converted into a passive off-grid state, and power supply of the microgrid system by the large power grid can be manually stopped, so that the current microgrid system is in the passive off-grid state.
In an embodiment, in order to achieve the maximum program load in the microgrid system and guarantee the maximum power supply to the user, as shown in fig. 4, after the microgrid system executes the security policy, the method further includes the following steps S302-S310:
And S302, selecting the load branch/distributed power supply with the minimum power value from the load branch/distributed power supplies disconnected from the microgrid system according to the sequence of the power values from small to large.
In this step, if the disconnected load branch/distributed power supply needs to be reconnected, the load branch/distributed power supply with the minimum power value needs to be selected from the disconnected load branch/distributed power supply according to the sequence of the power values from small to large. Because the normal operation state in the off-grid state in the microgrid system needs to be ensured, the load branch circuit/distributed power supply with the minimum power value needs to be selected from the disconnected load branch circuits/distributed power supplies for the re-switching verification according to the sequence of the power values from small to large, and if the re-switching of the selected load branch circuit/distributed power supply does not influence the normal operation state in the off-grid state in the microgrid system, the corresponding load branch circuit/distributed power supply is allowed to be re-switched.
and S304, multiplying the power value of the selected load branch/distributed power supply by a preset threshold value to generate a first result value.
in the embodiment of the present invention, the preset threshold may be 1.5, or may be a number greater than 1.5, and during each re-commissioning verification, a product obtained by multiplying the power value of the selected load branch/distributed power supply by the preset threshold needs to be calculated first, and a first result value is generated, so as to ensure that, in the re-commissioning verification process, the normal operation state in the off-grid state in the microgrid system is not affected by the power value of the selected load branch/distributed power supply when the power value is a multiple value or greater than the multiple value.
and S306, adding the first result value into the current micro-grid system, and calculating the total power value of the current micro-grid system.
S308, judging whether the total power value of the current micro-grid system is larger than or equal to the maximum discharging power of the main energy storage converter in the micro-grid system and smaller than or equal to the maximum charging power of the main energy storage converter.
And S310, if the total power value of the current micro-grid system is greater than or equal to the maximum discharge power of the main energy storage converter in the micro-grid system and less than or equal to the maximum charging power of the main energy storage converter, controlling the load branch/distributed power supply with the selected minimum power value to be switched again.
In the embodiment of the invention, if the total power value of the current micro-grid system is greater than or equal to the maximum discharge power of the main energy storage converter in the micro-grid system and less than or equal to the maximum charge power of the main energy storage converter, it is indicated that the newly switched load branch/distributed power supply does not cause the overcharge/discharge power of the main energy storage converter, and the newly switched load branch/distributed power supply is allowed and controlled.
As can be seen from the above, in the embodiment of the invention, the safe operation strategy of the microgrid system is pre-established according to each load branch, each distributed power supply and the main energy storage converter in the microgrid system; if the micro-grid system is in an off-grid state, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system; and if the micro-grid system is in a grid-connected state, constantly monitoring the state of the micro-grid system, and controlling the micro-grid system to execute the safe operation strategy to realize the off-grid autonomous operation of the micro-grid system when the micro-grid system is converted from the grid-connected state to the off-grid state. After the micro-grid system is put into operation, the load condition of the micro-grid system is monitored in real time through the pre-established safe operation strategy, and the load or the distributed power supply needing to be disconnected is adjusted, so that the micro-grid can normally work to realize the autonomous operation of the off-grid under the off-grid state or when the grid is connected to the off-grid state.
referring to fig. 5, in response to the above-mentioned off-grid autonomous operation method for the microgrid system, an embodiment of the present invention further provides an off-grid autonomous operation apparatus for the microgrid system, where the apparatus 100 includes: policy establishing means 101, first judging means 102, first controlling means 103, second judging means 104, second controlling means 105, and third controlling means 106.
The strategy establishing unit 101 is used for establishing a safe operation strategy of the microgrid system in advance according to each load branch, each distributed power supply and the main energy storage converter in the microgrid system.
the first judging unit 102 is configured to judge an operation state of the microgrid system.
The first control unit 103 is configured to control the microgrid system to execute the safe operation policy to implement off-grid autonomous operation of the microgrid system if the microgrid system is in an off-grid state.
A second determining unit 104, configured to determine, if the microgrid system is in a grid-connected state, whether the microgrid system currently receives a passive off-grid signal or an active off-grid signal.
And the second control unit 105 is configured to control the microgrid system to execute the safe operation strategy to implement off-grid autonomous operation of the microgrid system if the microgrid system currently receives a passive off-grid signal.
A third control unit 106, configured to adjust a power value of a grid-connected point to be equal to zero if the microgrid system currently receives an active off-grid signal, and then control the microgrid system to execute the safe operation policy to implement off-grid autonomous operation of the microgrid system.
referring to fig. 6, the policy establishing unit 101 includes:
The obtaining unit 101a is configured to obtain a power value of each load branch in the microgrid system and a power value of each distributed power source.
And the sorting unit 101b is configured to sort the load branches and the distributed power supplies respectively according to the sequence of the power values from large to small.
the first calculating unit 101c is configured to add the power values of the load branches to obtain a total power value of the load and add the power values of the distributed power supplies to obtain a total power value of the distributed power supplies.
The execution unit 101d is configured to subtract the total power value of the distributed power source from the total power value of the load, compare a first difference of an algebraic difference obtained by the subtraction with a maximum charging power of a main energy storage converter of the microgrid system and a maximum discharging power of the main energy storage converter of the microgrid system, select a load branch or a distributed power source with a smallest power value from the load branches or the distributed power sources in sequence if the first difference of the algebraic difference is greater than the maximum charging power of the main energy storage converter or less than the maximum discharging power of the main energy storage converter, and control the selected load branch or the distributed power source with the smallest power value to be disconnected from the microgrid system.
And the strategy establishing subunit 101e is configured to determine whether the first difference of the algebraic differences is greater than the maximum charging power of the main energy storage converter or less than the maximum discharging power of the main energy storage converter, if so, continue to execute the execution unit 101d, and if not, record all load branches and all distributed power supplies disconnected from the microgrid system as a safe operation strategy of the microgrid system.
Referring to fig. 7, the third control unit 106 includes:
The calculation obtaining unit 106a is configured to subtract the total power value of the distributed power source in the microgrid system from the total power value of the load branch, and obtain a second difference value of the algebraic difference obtained by the subtraction.
and the third control subunit 106b is configured to control a power value of the main energy storage converter of the microgrid system to be equal to a second difference value of an algebraic difference obtained by subtracting the total power value of the distributed power supply from the total power value of the load branch.
Referring to fig. 8, the apparatus 100 further includes:
and the selecting unit 107 is configured to select the load branch/distributed power supply with the minimum power value from the load branches/distributed power supplies disconnected from the microgrid system in the order from small power value to large power value.
A generating unit 108, configured to multiply the power value of the selected load branch/distributed power source by a preset threshold to generate a first result value.
And the second calculating unit 109 is configured to add the first result value to the current microgrid system, and calculate a total power value of the current microgrid system.
A third determining unit 110, configured to determine whether a total power value of the current microgrid system is greater than or equal to a maximum discharging power of a main energy storage converter in the microgrid system and is less than or equal to a maximum charging power of the main energy storage converter.
and the control reclosing unit 111 is used for controlling the reclosing of the load branch/distributed power supply with the selected minimum power value if the total power value of the current micro-grid system is greater than or equal to the maximum discharging power of the main energy storage converter in the micro-grid system and less than or equal to the maximum charging power of the main energy storage converter.
as can be seen from the above, in the embodiment of the invention, the safe operation strategy of the microgrid system is pre-established according to each load branch, each distributed power supply and the main energy storage converter in the microgrid system; if the micro-grid system is in an off-grid state, controlling the micro-grid system to execute a safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system; and if the micro-grid system is in a grid-connected state, constantly monitoring the state of the micro-grid system, and controlling the micro-grid system to execute a safe operation strategy to realize the off-grid autonomous operation of the micro-grid system when the micro-grid system is converted from the grid-connected state to the off-grid state. After the micro-grid system is put into operation, the load condition of the micro-grid system is monitored in real time through the pre-established safe operation strategy, and the load or the distributed power supply needing to be disconnected is adjusted, so that the micro-grid can normally work to realize the autonomous operation of the off-grid when the off-grid state or the grid connection is converted into the off-grid state.
the off-grid autonomous operation device of the micro-grid system corresponds to the off-grid autonomous operation method of the micro-grid system one by one, and the specific principle and process are the same as those of the method in the embodiment and are not described again.
the embodiment of the invention also provides a micro-grid system, which mainly comprises the main current energy storage converter, the load branch circuit and the distributed power supply, wherein the off-grid autonomous operation method of the micro-grid system is adopted when the micro-grid system operates.
The steps in the off-grid autonomous operation method of the microgrid system can be sequentially adjusted, combined and deleted according to actual needs.
the units in the off-grid autonomous operation device of the microgrid system can be merged, divided and deleted according to actual needs.
While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. An off-grid autonomous operation method for a microgrid system, the method comprising:
Pre-establishing a safe operation strategy of the micro-grid system according to each load branch, each distributed power supply and a main energy storage converter in the micro-grid system;
Judging the running state of the micro-grid system;
If the micro-grid system is in an off-grid state, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system;
If the micro-grid system is in a grid-connected state, judging whether the micro-grid system currently receives a passive off-grid signal or an active off-grid signal;
if the micro-grid system currently receives a passive off-grid signal, controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system;
and if the micro-grid system currently receives the active off-grid signal, adjusting the power value of the grid-connected point to be zero, and then controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system.
2. the method as claimed in claim 1, wherein the pre-establishing a safe operation strategy of the microgrid system according to each load branch, each distributed power source and a main energy storage converter in the microgrid system specifically comprises:
Step one, acquiring power values of all load branches and distributed power sources in the micro-grid system;
step two, sorting each load branch and each distributed power supply respectively according to the sequence of the power values from large to small;
step three, adding the power values of all the load branches to obtain a total power value of the load and adding the power values of all the distributed power supplies to obtain a total power value of the distributed power supplies;
step four, subtracting the total power value of the distributed power supply from the total power value of the load, respectively comparing a first difference value of an algebraic difference obtained by subtracting with the maximum charging power of a main energy storage converter of the microgrid system and the maximum discharging power of the main energy storage converter of the microgrid system, if the first difference value of the algebraic difference is larger than the maximum charging power of the main energy storage converter or smaller than the maximum discharging power of the main energy storage converter, selecting a load branch or a distributed power supply with the smallest power value from each load branch or each distributed power supply in sequence, and controlling the selected load branch or the distributed power supply with the smallest power value to be disconnected from the microgrid system;
And step five, judging whether the first difference value of the algebraic difference is larger than the maximum charging power of the main energy storage converter or smaller than the maximum discharging power of the main energy storage converter, if so, continuing to execute the step four, and if not, recording all load branches and all distributed power supplies disconnected from the microgrid system as a safe operation strategy of the microgrid system.
3. The method of claim 1, wherein adjusting the grid-connected point power value to be equal to zero comprises:
Subtracting the total power value of the distributed power supply in the micro-grid system from the total power value of the load, and acquiring a second difference value of the algebraic difference obtained by subtracting;
And controlling the power value of a main energy storage converter of the micro-grid system to be equal to a second difference value of an algebraic difference obtained by subtracting the total power value of the distributed power supply and the total power value of the load branch.
4. The method of claim 1, wherein after the microgrid system executes the security policy, the method further comprises:
Selecting the load branch circuit/distributed power supply with the minimum power value from the load branch circuits/distributed power supplies disconnected from the micro-grid system according to the sequence of the power values from small to large;
Multiplying the power value of the selected load branch/distributed power supply by a preset threshold value to generate a first result value;
Adding the first result value into the current micro-grid system, and calculating the total power value of the current micro-grid system;
Judging whether the total power value of the current micro-grid system is greater than or equal to the maximum discharge power of a main energy storage converter in the micro-grid system and less than or equal to the maximum charging power of the main energy storage converter;
and if the total power value of the current micro-grid system is greater than or equal to the maximum discharge power of a main energy storage converter in the micro-grid system and less than or equal to the maximum charge power of the main energy storage converter, controlling the load branch/distributed power supply with the selected minimum power value to be switched again.
5. the method of claim 1, wherein the active off-grid signal comprises an artificial active off-grid command, and the passive off-grid signal comprises an off-grid command in case of a microgrid power supply failure.
6. An off-grid autonomous operation apparatus for a microgrid system, the apparatus comprising:
The strategy establishing unit is used for pre-establishing a safe operation strategy of the micro-grid system according to each load branch, each distributed power supply and the main energy storage converter in the micro-grid system;
The first judgment unit is used for judging the operation state of the microgrid system;
the first control unit is used for controlling the micro-grid system to execute the safe operation strategy to realize the off-grid autonomous operation of the micro-grid system if the micro-grid system is in an off-grid state;
The second judgment unit is used for judging whether the micro-grid system currently receives a passive off-grid signal or an active off-grid signal if the micro-grid system is in a grid-connected state;
the second control unit is used for controlling the micro-grid system to execute the safe operation strategy to realize the off-grid autonomous operation of the micro-grid system if the micro-grid system currently receives a passive off-grid signal;
And the third control unit is used for adjusting the power value of the grid-connected point to be zero if the micro-grid system currently receives the active off-grid signal, and then controlling the micro-grid system to execute the safe operation strategy so as to realize the off-grid autonomous operation of the micro-grid system.
7. The apparatus of claim 6, wherein the policy establishing unit comprises:
The acquiring unit is used for acquiring the power value of each load branch and the power value of each distributed power supply in the micro-grid system;
The sequencing unit is used for sequencing each load branch and each distributed power supply respectively according to the sequence of the power values from large to small;
The first calculation unit is used for adding the power values of the load branches to obtain a total power value of the load and adding the power values of the distributed power supplies to obtain a total power value of the distributed power supplies;
the execution unit is used for subtracting the total power value of the distributed power supply from the total power value of the load, respectively comparing a first difference value of an algebraic difference obtained by subtracting with the maximum charging power of a main energy storage converter of the microgrid system and the maximum discharging power of the main energy storage converter of the microgrid system, and if the first difference value of the algebraic difference is larger than the maximum charging power of the main energy storage converter or smaller than the maximum discharging power of the main energy storage converter, selecting a load branch or a distributed power supply with the smallest power value from each load branch or each distributed power supply in sequence, and controlling the selected load branch or the distributed power supply with the smallest power value to be disconnected from the microgrid system;
And the strategy establishing subunit is used for judging whether the first difference value of the algebraic difference is greater than the maximum charging power of the main energy storage converter or less than the maximum discharging power of the main energy storage converter, if so, continuing to execute the step four, and if not, recording all load branches and all distributed power supplies disconnected from the microgrid system as a safe operation strategy of the microgrid system.
8. The apparatus of claim 6, wherein the third control unit comprises:
The calculation obtaining unit is used for subtracting the total power value of the distributed power supply in the micro-grid system from the total power value of the load branch and obtaining a second difference value of the algebraic difference obtained by subtracting;
And the third control subunit is used for controlling the power value of the main energy storage converter of the microgrid system to be equal to a second difference value of the algebraic difference obtained by subtracting the total power value of the distributed power supply from the total power value of the load branch.
9. the apparatus of claim 6, wherein the apparatus further comprises:
the selecting unit is used for selecting the load branch/distributed power supply with the minimum power value from the load branch/distributed power supplies disconnected from the micro-grid system according to the sequence of the power values from small to large;
The generating unit is used for multiplying the power value of the selected load branch/distributed power supply by a preset threshold value to generate a first result value;
the second calculation unit is used for adding the first result value into the current micro-grid system and calculating the total power value of the current micro-grid system;
the third judging unit is used for judging whether the total power value of the current micro-grid system is greater than or equal to the maximum discharging power of a main energy storage converter in the micro-grid system and less than or equal to the maximum charging power of the main energy storage converter;
and the control re-switching unit is used for controlling the re-switching of the load branch/the distributed power supply with the selected minimum power value if the total power value of the current micro-grid system is greater than or equal to the maximum discharging power of the main energy storage converter in the micro-grid system and less than or equal to the maximum charging power of the main energy storage converter.
10. a microgrid system, which mainly comprises a main current energy storage converter, a load branch circuit and a distributed power supply, and is characterized in that the microgrid system adopts an off-grid autonomous operation method of the microgrid system as claimed in any one of claims 1-5 during operation.
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