CN112910002A - Smooth switching method and device for self-adaptive main power supply operation mode of microgrid - Google Patents
Smooth switching method and device for self-adaptive main power supply operation mode of microgrid Download PDFInfo
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- CN112910002A CN112910002A CN202110217309.6A CN202110217309A CN112910002A CN 112910002 A CN112910002 A CN 112910002A CN 202110217309 A CN202110217309 A CN 202110217309A CN 112910002 A CN112910002 A CN 112910002A
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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
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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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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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
- H02J3/40—Synchronising a generator for connection to a network or to another generator
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Abstract
The invention discloses a micro-grid self-adaptive main power supply operation mode smooth switching method and device, wherein a micro-grid coordination controller judges whether a main power supply is an energy storage or a diesel generator according to the current load requirement when switching from a grid connection to an island, if the diesel generator is the main power supply, the diesel generator is automatically started, new energy output limitation, load shedding and tie line power control are carried out according to the system operation state, the tie line power switches the main power supply operation mode within a set value range and a tie-point switch is disconnected, and the smooth switching from the grid connection to the island is completed; when the island is switched to the grid-connected mode, the microgrid coordinated controller adopts a control strategy of combining automatic synchronization and multiple synchronization, controls the current main power supply to adjust the voltages of the microgrid side and the system side to be consistent, increases and decreases the frequency of the microgrid side according to the frequency of the system side and the phase angle difference between the microgrid side and the system side, and then the grid-connected point switch is switched on synchronously after the synchronous switching-on condition is met, so that the island is switched to the grid-connected mode for smooth switching.
Description
Technical Field
The invention relates to the field of microgrid control, in particular to a microgrid self-adaptive main power supply operation mode smooth switching method and device.
Background
The micro-grid is a small-sized power generation and distribution system organically integrating a distributed power supply, a load, an energy storage device and a control protection device together, can effectively solve the stability problem of a large-scale distributed power supply after being connected into a power grid, and can be connected with a large power grid in a networking mode and separated from the large power grid in an isolated island mode.
The power transmission distance is long in remote areas far away from a load center, on one hand, line loss is increased due to overlarge line impedance, voltage drop is large, the remote areas are in a weak power grid state, a diesel generator needs to be started to supply power to a system in some areas at a load peak, on the other hand, the line passes through a geographic environment to be complex, when the line breaks down, the fault point position is difficult to find in a short time, the system maintenance time is long, and the power supply recovery difficulty is large in time. The renewable resources around the areas are often rich, and the substation level micro-grid with large scale is formed by combining the distributed power supply, load and energy storage on the accessed substation and the outgoing line thereof for effective management, so that the economy, reliability and electric energy quality of local power supply can be greatly improved. With the continuous development of the micro-grid, the structure of the micro-grid is more and more complex, the control difficulty is continuously increased, the voltage frequency fluctuation in the operation mode switching process can seriously affect the load power supply, and the realization of the smooth switching between grid-connected operation and island operation is the key and difficult point of the micro-grid control.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a microgrid self-adaptive main power supply operation mode smooth switching method and device, which can self-adaptively store energy or use a diesel generator as an island main power supply and ensure the voltage frequency stability of a microgrid in the mode switching process.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
in a first aspect, the invention provides a microgrid self-adaptive main power supply operation mode smooth switching method, which comprises a grid-connected to island method;
the grid-connected to island method comprises the following steps:
receiving a switching instruction from grid connection to island;
selecting an off-grid main power supply according to the current load requirement;
carrying out new energy output limitation, load shedding and tie line power control according to the system running state;
and when the power of the tie line is within the range of the set value, switching the main power supply operation mode and disconnecting the grid-connected point switch, thereby finishing the smooth switching from grid connection to island.
Further, the off-grid main power supply comprises an energy storage and a diesel generator;
the selecting of the off-grid main power supply according to the current load demand comprises:
if the current load demand PloadLess than the maximum discharge capacity P of stored energydischrgAnd using the stored energy as an island main power supply, or using the diesel generator set as the island main power supply.
Further, the performing new energy output limitation, load shedding and tie-line power control according to the system operation state comprises:
when the stored energy is taken as the main power supply of the island, if the new energy is taken out, the new energy is taken outdgWith the current load demand PloadThe difference is larger than the maximum charging power PchrgThe output of new energy is limited;
when the diesel generator is used as an island main power supply, if the current load demand PloadGreater than the maximum discharge capacity P of stored energydischrgAnd total capacity P of diesel generatordieselWhen the sum is obtained, load shedding is carried out;
and executing tie line power control after the new energy output limit or the load shedding is finished.
Further, when the tie-line power is within the range of the set value, switching the main power supply operation mode and turning off the point-to-grid switch includes:
when the absolute value | P | of the active power of the tie line is less than the active set value PsetAnd the absolute value of reactive power | Q | of the tie line is less than the set value Q of the reactive powersetSwitching a preset main power control mode;
if the stored energy is used as an island main power supply, switching the stored energy to a virtual synchronous machine mode, otherwise, controlling the diesel generator to operate in the island mode;
and when the main power control mode is switched, the grid-connected point switch is switched off, so that smooth switching from grid connection to island is completed.
Furthermore, the microgrid self-adaptive main power supply operation mode smooth switching method and device also comprise an island-to-grid method;
the island-to-grid method comprises the following steps:
receiving an island-to-grid switching instruction or detecting system voltage recovery;
identifying a current main power supply mode, and adjusting the voltages of the microgrid side and the system side to be consistent according to the current main power supply mode;
increasing or decreasing the frequency of the micro-grid side according to the frequency of the system side and the phase angle difference between the micro-grid side and the system side, simultaneously starting a corresponding synchronous switch-on detection function of a grid-connected point switch by a micro-grid coordination controller when the main power supply performs synchronous adjustment, and if the synchronous switch-on detection function is performed at a set time TmaxAnd the synchronous closing condition is met, and the grid-connected point switch is synchronously closed to complete the smooth switching from the island to the grid.
Further, the method for adjusting the voltages of the microgrid side and the system side to be consistent according to the current main power supply mode comprises the following steps:
if the main power supply is energy storage, sending a frequency deviation delta f and voltage deviation delta U instruction to an energy storage converter according to the frequency difference, the angle difference and the voltage difference measurement of the system side and the micro-grid side;
if the main power supply is a diesel generator, the system side voltage is controlled to be connected into a diesel generator master coordination controller, meanwhile, a starting synchronization grid connection command is sent to the diesel generator master coordination controller, the diesel generator master coordination controller automatically generates a rotating speed and an excitation reference value through system voltage input measurement and sends the rotating speed and the excitation reference value to each diesel generator controller, and each diesel generator is controlled to adjust the micro-grid side frequency f and the micro-grid side voltage U.
Further, the island-to-grid method further comprises the following steps:
at a set time TmaxIf the internal system fails to complete synchronous closing, the micro-grid coordination controller automatically resets the regulating instruction of the energy storage converter or the diesel generator master coordination controller, and simultaneously stops the synchronous closing detection function of the corresponding grid-connected point switch;
if the number of times of synchronization is smaller than N, the delay delta T automatically executes synchronization adjustment and synchronization switch-on detection logic again, and if the number of times of synchronization reaches N times and synchronization is not successfully connected, the island-to-grid switching logic is finished, and the micro-grid continues island operation.
In a second aspect, the invention provides a microgrid self-adaptive main power supply operation mode smooth switching device, which comprises a grid-connected to island device;
the grid-connected island-to-island device comprises the following modules:
an instruction receiving module: the device is used for receiving a switching instruction from grid connection to island;
the main power supply selection module: the off-grid main power supply is selected according to the current load requirement;
a power control module: the system is used for carrying out new energy output limitation, load shedding and tie line power control according to the system running state;
a mode switching module: and when the power of the tie line is within the range of the set value, the main power supply operation mode is switched and the grid-connected point switch is disconnected, so that the smooth switching from grid connection to island is completed.
Further, the device also comprises an island-to-grid device;
the island-to-grid device comprises the following modules:
the instruction detection module: the system is used for receiving an island-to-grid switching instruction or detecting system voltage recovery;
the main power source identification module: the system is used for identifying the current main power supply mode and adjusting the voltages of the microgrid side and the system side to be consistent according to the current main power supply mode;
a closing module: the microgrid coordinated controller is used for increasing and decreasing the frequency of the microgrid side according to the frequency of the system side and the phase angle difference between the microgrid side and the system side, and simultaneously starting the corresponding switch-on and switch-off point switch synchronous switch-on functions of the microgrid coordinated controller when the main power supply performs synchronous adjustment, and if the synchronous switch-on and switch-off functions are detected at the set time TmaxAnd the synchronous closing condition is met, and the grid-connected point switch is synchronously closed to complete the smooth switching from the island to the grid.
In a third aspect, the present invention further provides a smooth switching apparatus for a self-adaptive main power supply operation mode of a microgrid, comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate according to the instructions to perform the steps of the above-described method.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a microgrid self-adaptive main power supply operation mode smooth switching method and device, because an energy storage system is higher in price at present and overlarge in large-capacity investment cost, the maximum configuration capacity often cannot meet the power supply requirements of all loads in a microgrid, a certain diesel generator needs to be configured, grid-connected to island switching adopts the energy storage or the diesel generator as an island main power supply through automatic identification, the economy of the microgrid is improved, the island to grid-connected switching is realized through a mode of combining automatic synchronization and multiple synchronization control in a grid-connected process, the frequency and voltage of the main power supply are adjusted to meet the synchronization switching-on condition, grid-connected impact is reduced, and grid-connected efficiency and success rate can be effectively improved.
Drawings
FIG. 1 is a system architecture diagram of a method and apparatus for smooth switching of adaptive main power modes of a microgrid;
FIG. 2 is a grid-connected to island switching flow chart;
FIG. 3 is a waveform diagram of active and reactive power at a grid-connected point for switching from grid-connected mode to island mode;
FIG. 4 is a waveform diagram of voltage frequency variation at the moment of switching from grid-connected mode to island mode;
FIG. 5 is a flow chart of an island to grid switching;
FIG. 6 is a waveform diagram of voltage and frequency regulation for switching between an island grid mode and a grid mode;
FIG. 7 is a waveform diagram of voltage frequency variation at the switching time of an island-to-grid mode;
fig. 8 is a flow chart of adaptive main power mode switching.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The first embodiment is as follows:
the embodiment provides a microgrid self-adaptive main power supply operation mode smooth switching method, which is suitable for a microgrid control system containing energy storage and a diesel generator, can self-adaptively store energy or use the diesel generator as an island main power supply, and ensures stable voltage frequency of a microgrid in a mode switching process.
In order to achieve the above purpose, the solution of the invention is: a microgrid self-adaptive main power supply operation mode smooth switching method comprises the following steps:
when the grid-connected to island switching is performed, the micro-grid coordination controller judges whether a main power supply is an energy storage or diesel generator according to the current load requirement, if the diesel generator is the main power supply, the diesel generator is automatically started, new energy output limitation, load shedding and tie line power control are performed according to the system operation state, and after the tie line power meets a set value, the main power supply operation mode is switched and a grid-connected point switch is disconnected, so that grid-connected to island smooth switching is completed; when the island is switched to the grid-connected mode, the microgrid coordinated controller adopts a control strategy of combining automatic synchronization and multiple synchronization, controls the current main power supply to adjust the voltages of the microgrid side and the system side to be consistent, increases and decreases the frequency of the microgrid side according to the frequency of the system side and the phase angle difference between the microgrid side and the system side, and then the grid-connected point switch is switched on synchronously after the synchronous switching-on condition is met, so that the island is switched to the grid-connected mode for smooth switching.
The micro-grid coordination controller receives a grid-connected to island switching instruction, and if the current load demand P isloadLess than stored energyMaximum discharge capacity PdischrgWhen the stored energy is used as the main power supply of the island, if the stored energy is used as the main power supply of the island, the new energy output P is generateddgWith the current load demand PloadThe difference is larger than the maximum charging power PchrgWhen the diesel generator is used as an island main power supply, if the current load demand P is requiredloadGreater than the maximum discharge capacity P of stored energydischrgAnd total capacity P of diesel generatordieselAnd when the sum is obtained, load shedding is required, and the power control of the tie line is executed after the output limit of the new energy or the load shedding is finished.
When the absolute value | P | of the active power of the tie line is less than the active set value PsetAnd the absolute value of reactive power | Q | of the tie line is less than the set value Q of the reactive powersetAnd switching a preset main power supply control mode later, if the stored energy is used as an island main power supply, switching the stored energy to a virtual synchronous machine mode, otherwise, controlling the diesel generator to operate in the island mode, and disconnecting the grid-connected point switch after the main power supply control mode is switched, so as to complete the smooth switching from grid connection to island.
The microgrid coordinated controller receives an island-to-grid switching instruction or detects that system voltage recovers, and then automatically identifies whether a current main power supply is an energy storage or a diesel generator, if the main power supply is the energy storage, frequency deviation delta f and voltage deviation delta U instructions are sent to an energy storage converter according to frequency difference, angle difference and pressure difference measurement between a system side and a microgrid side, if the main power supply is the diesel generator, the system side voltage is controlled to be connected to a diesel generator master coordinated controller, meanwhile, a starting synchronous grid connection instruction is sent to the diesel generator master coordinated controller, the diesel generator master coordinated controller automatically generates rotating speed and excitation reference values through system voltage input measurement and sends the rotating speed and excitation reference values to each diesel generator controller, and each diesel generator is controlled to adjust the microgrid side frequency f and the voltage U.
When the main power supply performs synchronous regulation, the microgrid coordinated controller simultaneously starts the corresponding synchronous closing detection function of the grid-connected point switch, and if the synchronous closing detection function is performed within the set time TmaxAnd the synchronous closing condition is met, and the grid-connected point switch is synchronously closed to complete the smooth switching from the island to the grid.
At a set time TmaxIf the internal system fails to complete synchronous switching, the micro-grid coordination controller automatically resets the regulating instruction of the energy storage converter or the diesel generator main coordination controller, and simultaneously stops the synchronous switching detection function of the corresponding grid-connected point switch, if the synchronous times are smaller than N, the delay delta T automatically executes synchronous regulation and synchronous switching detection logic again, and if the synchronous times reach N times and are not successfully connected to the grid, the island-to-grid switching logic is ended, and grid connection fails.
The application scenario of the invention is a micro-grid control system, the system structure diagram is shown in fig. 1, a micro-grid bus is of a single bus-section structure and comprises a photovoltaic system, a hydroelectric system, a diesel generator set and an energy storage system, a micro-grid incoming line 1 and a micro-grid incoming line 2 come from a remote power grid, PCC1 and PCC2 are grid-connected points, and the diesel generator set and the energy storage system can be used as a main power supply to maintain the system voltage frequency during isolated island operation. The microgrid coordinated controller collects the voltage and current of the whole system and the running state of each device, carries out real-time coordinated control on the load and the power supply device, and realizes the stable running of the whole microgrid system.
In the embodiment shown in fig. 2, the microgrid coordinated controller receives a grid-connected to island switching instruction, and if the current load demand P isloadLess than the maximum discharge capacity P of stored energydischrgWhen the stored energy is used as the main power supply of the island, if the stored energy is used as the main power supply of the island, the new energy output P is generateddgWith the current load demand PloadThe difference is larger than the maximum charging power PchrgWhen the diesel generator is used as an island main power supply, if the current load demand P is requiredloadGreater than the maximum discharge capacity P of stored energydischrgAnd total capacity P of diesel generatordieselAnd when the sum is obtained, load shedding is required, and the power control of the tie line is executed after the output limit of the new energy or the load shedding is finished. When the absolute value | P | of the active power of the tie line is less than the active set value PsetAnd the absolute value of reactive power | Q | of the tie line is less than the set value Q of the reactive powersetSwitching a preset main power supply control mode later, and switching the stored energy to the virtual synchronous machine if the stored energy is used as an island main power supplyAnd otherwise, controlling the diesel generator to operate in an island mode, and disconnecting the grid-connected point switch after the main power control mode is switched to complete smooth switching from grid connection to island.
In order to verify the effectiveness of the method, a grid-connected to island switching test is carried out on a micro-grid project site, fig. 3 is a grid-connected to island mode switching grid-connected point active and reactive power waveform diagram, the active power is 0.097MW after being controlled by the power of a tie line before a 0.0725s grid-connected point switch is tripped, the reactive power is-0.028 MVar, the setting range of the active power of the tie line is +/-0.1 MW, the setting range of the reactive power is +/-0.05 MVar, and the power of the tie line is adjusted to be within the range of a set value. Fig. 4 is a voltage frequency change waveform diagram at the switching time of the grid-connected to island mode, the fluctuation range of the bus frequency of the micro-grid is 49.92 Hz-50.13 Hz after the grid-connected point switch is tripped, the voltage basically has no phase and amplitude abrupt change, and the whole system realizes the smooth switching from grid-connected to island.
In the embodiment shown in fig. 5, after receiving an island-to-grid switching instruction or detecting that the system voltage is recovered, the microgrid coordinated controller automatically identifies whether the current main power source is an energy storage or a diesel generator, if the main power source is the energy storage, a frequency deviation delta f and a voltage deviation delta U instruction are sent to an energy storage converter according to the frequency difference, the angle difference and the voltage difference between the system side and the microgrid side, and if the main power source is the diesel generator, the system side voltage is controlled to be connected to a diesel generator master coordinated controller, and a start-up synchronization instruction is sent to the diesel generator master coordinated controller. When the main power supply performs synchronous regulation, the microgrid coordinated controller simultaneously starts the corresponding synchronous closing detection function of the grid-connected point switch, and if the synchronous closing detection function is performed within the set time TmaxAnd the synchronous closing condition is met, and the grid-connected point switch is synchronously closed to complete the smooth switching from the island to the grid. At a set time TmaxIf the internal system fails to complete synchronous closing, the micro-grid coordination controller automatically resets the regulating instruction of the energy storage converter or the diesel generator master coordination controller, and simultaneously stops the corresponding grid-connected point from being openedAnd closing and detecting the synchronous closing function, if the synchronous times are less than N, automatically executing synchronous regulation and detecting synchronous closing logic again by delaying delta T, and if the synchronous times reach N times and the grid connection is not successfully completed, ending the island-to-grid switching logic and failing to connect the grid.
In order to verify the effectiveness of the method, an island-to-grid switching test is performed on a microgrid project site, fig. 6 is a voltage and frequency regulation oscillogram for switching from an island-to-grid mode, the frequency of a main power supply regulation microgrid side is slightly higher than the frequency of a system side, and the voltage of the regulated microgrid side is close to the voltage of the system side. Fig. 7 is a voltage frequency change waveform diagram at the switching time of the island-to-grid mode, the grid-connected point switch recovers to be normal after the frequency oscillates for about 500ms after being switched on for 0.23s, the oscillation amplitude of the bus frequency is within the bearable range of the system, the voltage basically has no phase and amplitude mutation, and the whole system realizes the smooth switching from the island to the grid.
Fig. 8 is a flow chart of adaptive main power supply operation mode switching, in which a grid-connected to island instruction is received during grid-connected operation of the micro grid, and the micro grid is automatically switched to island operation, and in which grid voltage is recovered during island operation of the micro grid or the micro grid is switched to grid-connected operation after receiving the island to grid instruction.
In the embodiment of the application, microgrid coordinated controller gathers microgrid state information, and with energy storage and diesel generator communication in the microgrid, whether the grid-connected switches to the island adopts the energy storage or the diesel generator as the main power source of the island through automatic identification, the economy of the microgrid is improved, the island-connected switches to the grid-connected switches to the mode of combining with automatic synchronization and multiple synchronization control in the grid-connected process, the frequency and voltage of the main power source are adjusted to meet the synchronization switching-on condition, so that grid-connected impact is reduced, grid-connected efficiency and success rate can be effectively improved, grid-connected/island smooth switching improves the economy and stability of microgrid operation, and the method has great significance.
Example two:
the embodiment provides a microgrid self-adaptive main power supply operation mode smooth switching device, which comprises a grid-connected to island device and an island to grid-connected device;
the grid-connected island-to-island device comprises the following modules:
an instruction receiving module: the device is used for receiving a switching instruction from grid connection to island;
the main power supply selection module: the off-grid main power supply is selected according to the current load requirement;
a power control module: the system is used for carrying out new energy output limitation, load shedding and tie line power control according to the system running state;
a mode switching module: and when the power of the tie line is within the range of the set value, the main power supply operation mode is switched and the grid-connected point switch is disconnected, so that the smooth switching from grid connection to island is completed.
The island-to-grid device comprises the following modules:
the instruction detection module: the system is used for receiving an island-to-grid switching instruction or detecting system voltage recovery;
the main power source identification module: the system is used for identifying the current main power supply mode and adjusting the voltages of the microgrid side and the system side to be consistent according to the current main power supply mode;
a closing module: the microgrid coordinated controller is used for increasing and decreasing the frequency of the microgrid side according to the frequency of the system side and the phase angle difference between the microgrid side and the system side, and simultaneously starting the corresponding switch-on and switch-off point switch synchronous switch-on functions of the microgrid coordinated controller when the main power supply performs synchronous adjustment, and if the synchronous switch-on and switch-off functions are detected at the set time TmaxAnd the synchronous closing condition is met, and the grid-connected point switch is synchronously closed to complete the smooth switching from the island to the grid.
The apparatus is operable to perform the steps of the method of embodiment one, operating according to the instructions.
Example three:
the embodiment of the invention also provides a smooth switching device of the self-adaptive main power supply operation mode of the microgrid, which comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method of:
when the grid-connected to island switching is performed, the micro-grid coordination controller judges whether a main power supply is an energy storage or diesel generator according to the current load requirement, if the diesel generator is the main power supply, the diesel generator is automatically started, new energy output limitation, load shedding and tie line power control are performed according to the system operation state, and after the tie line power meets a set value, the main power supply operation mode is switched and a grid-connected point switch is disconnected, so that grid-connected to island smooth switching is completed; when the island is switched to the grid-connected mode, the microgrid coordinated controller adopts a control strategy of combining automatic synchronization and multiple synchronization, controls the current main power supply to adjust the voltages of the microgrid side and the system side to be consistent, increases and decreases the frequency of the microgrid side according to the frequency of the system side and the phase angle difference between the microgrid side and the system side, and then the grid-connected point switch is switched on synchronously after the synchronous switching-on condition is met, so that the island is switched to the grid-connected mode for smooth switching.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A smooth switching method of a self-adaptive main power supply operation mode of a micro-grid is characterized by comprising a grid-connected to island-isolated switching method;
the grid-connected to island method comprises the following steps:
receiving a switching instruction from grid connection to island;
selecting an off-grid main power supply according to the current load requirement;
carrying out new energy output limitation, load shedding and tie line power control according to the system running state;
and when the power of the tie line is within the range of the set value, switching the main power supply operation mode and disconnecting the grid-connected point switch, thereby finishing the smooth switching from grid connection to island.
2. The microgrid adaptive main power supply operation mode smooth switching method of claim 1, wherein the off-grid main power supply comprises an energy storage and a diesel generator;
the selecting of the off-grid main power supply according to the current load demand comprises:
if the current load is requiredCalculating PloadLess than the maximum discharge capacity P of stored energydischrgAnd using the stored energy as an island main power supply, or using the diesel generator set as the island main power supply.
3. The microgrid adaptive main power supply operation mode smooth switching method according to claim 2, wherein the performing new energy output limitation, load shedding and tie-line power control according to the system operation state comprises:
when the stored energy is taken as the main power supply of the island, if the new energy is taken out, the new energy is taken outdgWith the current load demand PloadThe difference is larger than the maximum charging power PchrgThe output of new energy is limited;
when the diesel generator is used as an island main power supply, if the current load demand PloadGreater than the maximum discharge capacity P of stored energydischrgAnd total capacity P of diesel generatordieselWhen the sum is obtained, load shedding is carried out;
and executing tie line power control after the new energy output limit or the load shedding is finished.
4. The microgrid adaptive main power supply operation mode smooth switching method according to claim 2, wherein switching the main power supply operation mode and turning off a grid-connected point switch when the tie line power is within a set value range comprises:
when the absolute value | P | of the active power of the tie line is less than the active set value PsetAnd the absolute value of reactive power | Q | of the tie line is less than the set value Q of the reactive powersetSwitching a preset main power control mode;
if the stored energy is used as an island main power supply, switching the stored energy to a virtual synchronous machine mode, otherwise, controlling the diesel generator to operate in the island mode;
and when the main power control mode is switched, the grid-connected point switch is switched off, so that smooth switching from grid connection to island is completed.
5. The microgrid adaptive main power supply operation mode smooth switching method and device according to claim 2, characterized in that the microgrid adaptive main power supply operation mode smooth switching method and device further comprises an island-to-grid method;
the island-to-grid method comprises the following steps:
receiving an island-to-grid switching instruction or detecting system voltage recovery;
identifying a current main power supply mode, and adjusting the voltages of the microgrid side and the system side to be consistent according to the current main power supply mode;
increasing or decreasing the frequency of the micro-grid side according to the frequency of the system side and the phase angle difference between the micro-grid side and the system side, simultaneously starting a corresponding synchronous switch-on detection function of a grid-connected point switch by a micro-grid coordination controller when the main power supply performs synchronous adjustment, and if the synchronous switch-on detection function is performed at a set time TmaxAnd the synchronous closing condition is met, and the grid-connected point switch is synchronously closed to complete the smooth switching from the island to the grid.
6. The microgrid adaptive main power supply operation mode smooth switching method according to claim 5, wherein the method for adjusting the microgrid-side and system-side voltages to be consistent according to the current main power supply mode comprises:
if the main power supply is energy storage, sending a frequency deviation delta f and voltage deviation delta U instruction to an energy storage converter according to the frequency difference, the angle difference and the voltage difference measurement of the system side and the micro-grid side;
if the main power supply is a diesel generator, the system side voltage is controlled to be connected into a diesel generator master coordination controller, meanwhile, a starting synchronization grid connection command is sent to the diesel generator master coordination controller, the diesel generator master coordination controller automatically generates a rotating speed and an excitation reference value through system voltage input measurement and sends the rotating speed and the excitation reference value to each diesel generator controller, and each diesel generator is controlled to adjust the micro-grid side frequency f and the micro-grid side voltage U.
7. The microgrid adaptive main power supply operation mode smooth switching method according to claim 6, characterized in that the island-to-grid method further comprises the following steps:
at a set time TmaxIf the internal system fails to complete synchronous closing, the micro-grid coordination controller automatically resets the energy storage converter orThe general coordination controller of the diesel generator regulates the instruction, and simultaneously stops the synchronous switching-on function of the corresponding grid-connected point switch detection;
if the number of times of synchronization is smaller than N, the delay delta T automatically executes synchronization adjustment and synchronization switch-on detection logic again, and if the number of times of synchronization reaches N times and synchronization is not successfully connected, the island-to-grid switching logic is finished, and the micro-grid continues island operation.
8. A micro-grid self-adaptive main power supply operation mode smooth switching device is characterized by comprising a grid-connected to island device;
the grid-connected island-to-island device comprises the following modules:
an instruction receiving module: the device is used for receiving a switching instruction from grid connection to island;
the main power supply selection module: the off-grid main power supply is selected according to the current load requirement;
a power control module: the system is used for carrying out new energy output limitation, load shedding and tie line power control according to the system running state;
a mode switching module: and when the power of the tie line is within the range of the set value, the main power supply operation mode is switched and the grid-connected point switch is disconnected, so that the smooth switching from grid connection to island is completed.
9. The microgrid adaptive main power supply operation mode smooth switching device according to claim 8, characterized in that the device further comprises an island-to-grid device;
the island-to-grid device comprises the following modules:
the instruction detection module: the system is used for receiving an island-to-grid switching instruction or detecting system voltage recovery;
the main power source identification module: the system is used for identifying the current main power supply mode and adjusting the voltages of the microgrid side and the system side to be consistent according to the current main power supply mode;
a closing module: the microgrid coordinated controller is used for increasing and decreasing the frequency of the microgrid side according to the frequency of the system side and the phase angle difference between the microgrid side and the system side, and the microgrid coordinated controller is started correspondingly when the main power supply is synchronously adjustedThe switch of the grid-connected point detects the synchronous switch-on function if the set time T is upmaxAnd the synchronous closing condition is met, and the grid-connected point switch is synchronously closed to complete the smooth switching from the island to the grid.
10. A smooth switching device of a micro-grid self-adaptive main power supply operation mode is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 7.
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