CN112701731A - Energy storage microgrid grid-connection and off-grid seamless switching device, method and system - Google Patents
Energy storage microgrid grid-connection and off-grid seamless switching device, method and system Download PDFInfo
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- CN112701731A CN112701731A CN202110095727.2A CN202110095727A CN112701731A CN 112701731 A CN112701731 A CN 112701731A CN 202110095727 A CN202110095727 A CN 202110095727A CN 112701731 A CN112701731 A CN 112701731A
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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
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
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Abstract
The invention relates to a device, a method and a system for seamless switching of grid connection and disconnection of an energy storage microgrid. The invention adopts a seamless switching mode, namely, the seamless switching is realized by switching from off-grid to on-grid, planned off-grid and unplanned off-grid. The seamless switching means that in the process of grid-connected and off-grid switching, the voltage and the frequency of the microgrid are within the range specified by the microgrid operation standard, the voltage deviation of each bus in the microgrid is not greater than the rated voltage, the frequency deviation is not greater than the specified value, the microgrid can safely and stably operate, the uninterrupted power supply of important sensitive loads is ensured, and the reliability of power supply of users is improved.
Description
Technical Field
The invention relates to the field of grid-connected and off-grid seamless switching of a microgrid, in particular to a device, a method and a system for grid-connected and off-grid seamless switching of an energy storage microgrid.
Background
The micro-grid system is a set of system constructed on the basis of distributed photovoltaic, wind power generation systems, energy storage systems, various loads and other electrical units. The microgrid is switched from a grid-connected mode to an off-grid operation mode and from the off-grid operation mode to the grid-connected mode, and two schemes of seamless switching and short-time seamless switching can be adopted.
For a seam switching scheme allowing short-time power failure, when an external power grid fails, a distributed power supply in a microgrid is powered off firstly; then a grid-connected switch of the micro-grid and an external power grid is opened, and the load in the micro-grid is powered off in a short time; and after the micro-grid and an external grid-connected switch are confirmed to be turned on, the main power supply in the micro-grid switches over a control mode, the voltage and the frequency of the micro-grid are reestablished, and the micro-grid operates independently. The criterion for switching the independent operation of the microgrid to grid connection is that the external power grid is detected to be recovered to be normal, a main power supply in the microgrid is firstly quitted to operate, the microgrid is in voltage loss, the load is short-time power off, other distributed power supplies quit to operate after the grid connection point is detected to be in voltage loss, then a microgrid grid connection switch is closed, the load is recovered to supply power, and after a certain time interval, all distributed power supplies in the microgrid are connected to the grid again.
At present, with the development of technology, seamless switching between grid-off switching and grid-connection switching of a microgrid and planned grid-off switching can be realized through mutual matching of a main power supply and a grid-connection interface device, so that no special requirements can be imposed on the time for switching the main power supply from a PQ mode to a V/f mode and the on-off time of a grid-connection point switch of the microgrid. Seamless switching, the power supply reliability is high, and when external power grid faults occur, the load in the microgrid can still be maintained and is not powered off, but the requirement on the control of the microgrid is high. For a micro-grid adopting a master-slave control strategy, a main power supply is required to be capable of being quickly switched from a grid-connected control mode to an independent control mode, and simultaneously, grid-connected switches of the micro-grid and the main power grid need to be capable of being quickly disconnected.
However, when the grid is unplanned and off-grid, because deviation exists between the output voltage amplitude, the frequency and the rated value when the island operates, direct grid connection operation is not allowed, and quasi-synchronous control needs to be carried out by adopting a phase-locked loop technology. Because the phase-locked loop and the power system have nonlinearity, the satisfactory dynamic performance is difficult to achieve by adjusting the control parameters of the phase-locked loop, the control effect of the system is influenced by the slow dynamic response of the phase-locked loop, and the stability of the system is reduced; especially, under the condition of weak power grid, a large amount of higher harmonics exist in the power grid, the phase locking precision of the phase-locked loop is influenced, the quasi-synchronization control effect is influenced, and even the system is possibly unstable.
Disclosure of Invention
The invention aims to provide a device, a method and a system for seamless switching of grid connection and disconnection of an energy storage microgrid, and the device, the method and the system can solve the problem that seamless switching cannot be realized simultaneously when the microgrid is switched from a grid connection mode to a grid connection mode, and when the microgrid is switched from a planned grid connection mode and is not in a planned grid connection mode.
In order to achieve the purpose, the invention provides the following scheme:
an energy storage microgrid grid-connected and off-grid seamless switching device comprises an operation controller, a grid-connected point switch, a grid-connected interface device, a stability control device and an energy storage PCS which are electrically connected with a main power supply and a microgrid,
the operation controller is used for receiving, translating and executing the control command to complete the operation control of the main and micro-grid;
the grid-connected point switch is positioned between the main power grid and the micro power grid;
the grid-connected interface device is used for controlling the on/off of a grid-connected point switch;
the stability control device is used for isolating the micro-grid from the main grid;
the energy storage PCS is used for switching the operation modes, detecting voltages on two sides of a grid-connected point and carrying out synchronization.
The energy storage microgrid grid-connected and off-grid seamless switching method comprises the following steps:
planned off-grid mode:
step 11: the operation controller receives a planned off-network instruction;
step 12: detecting the states of the grid-connected point switch, the main network and the microgrid;
step 13: the operation controller respectively issues planned off-grid instructions to the grid-connected interface device and mode switching instructions to the energy storage PCS;
step 14: the grid-connected interface device controls the grid-connected point switch to be switched off, and the energy storage PCS is switched from a PQ operation mode to a V/f operation mode;
grid connection mode:
step 21: the operation controller receives a synchronous grid-connected instruction;
step 22: detecting the states of the grid-connected point switch, the main network and the microgrid;
step 23: the operation controller respectively gives synchronous closing instructions to the grid-connected interface device and gives synchronous adjusting instructions to the energy storage PCS;
step 24: the energy storage PCS detects voltages on two sides of a grid-connected point to carry out synchronization;
step 25: the grid-connected interface device controls a grid-connected point switch to be switched on, and the energy storage PCS is switched from a V/f operation mode to a PQ operation mode;
unplanned off-grid mode:
step 31: detecting that a main network fails to cause unplanned off-network;
step 32: the grid-connected interface device controls the opening and closing of the grid-connected point switch;
step 33: and the stability control device is used for rapidly adjusting the exchange power, and simultaneously, the energy storage PCS is switched from the PQ operation mode to the V/f operation mode.
Optionally, the step 12 specifically includes:
judging whether the planned off-grid can be realized, wherein the judging process comprises the following steps: whether the grid-connected point switch is electrified or not, whether the main grid of the grid-connected point switch is electrified or not and whether the microgrid is electrified or not are judged;
if not, not executing planned off-grid;
if yes, judging whether the exchange power needs to be adjusted;
if yes, the microgrid operation controller adjusts the switching power and executes the step 13;
if not, directly executing step 13.
Optionally, the step 22 specifically includes:
judging whether synchronization grid connection can be achieved or not, wherein the judging process comprises the following steps: whether a grid-connected point switch sub-grid is electrified or not, whether a grid-connected point switch main grid is electrified or not and whether a micro-grid is electrified or not;
if not, synchronous grid connection is not executed;
if yes, go to step 23.
Optionally, after the step 24 and before the step 25, further comprising:
judging whether a synchronous closing condition is met;
if yes, go to step 25;
if not, the procedure returns to step 24.
An energy storage microgrid grid-on and off-grid seamless switching system comprises:
planned off-grid module:
the off-grid instruction receiving submodule is used for receiving a planned off-grid instruction through the operation controller;
the off-grid state detection submodule is used for detecting the states of the grid-connected point switch, the main grid and the microgrid;
the first instruction issuing sub-module is used for respectively issuing planned off-grid instructions to the grid-connected interface device through the operation controller and issuing mode switching instructions to the energy storage PCS;
the first operation mode switching submodule is used for controlling the grid-connected point switch to be switched off through the grid-connected interface device, and the energy storage PCS is switched to a V/f operation mode from a PQ operation mode;
a grid connection module:
the grid-connected instruction receiving submodule is used for receiving a synchronous grid-connected instruction through the operation controller;
the grid-connected detection submodule is used for detecting the states of the grid-connected point switch, the main grid and the microgrid;
the second instruction issuing submodule is used for operating the controller to respectively issue synchronous closing instructions to the grid-connected interface device and issue synchronous adjusting instructions to the energy storage PCS;
the synchronization sub-module is used for detecting voltages on two sides of the grid-connected point through the energy storage PCS to perform synchronization;
the second operation mode switching module is used for controlling the switching-on of the grid-connected point switch through the grid-connected interface device, and the energy storage PCS is switched from the V/f operation mode to the PQ operation mode;
unscheduled off-grid module:
the unplanned off-grid generation sub-module is used for detecting that the main network fails to cause unplanned off-grid;
the grid-connected point switch opening control submodule is used for controlling the grid-connected point switch opening through the grid-connected interface device;
and the third operation mode switching submodule is used for stabilizing the control device, quickly adjusting the switching power, and simultaneously switching the energy storage PCS from the PQ operation mode to the V/f operation mode.
Optionally, the off-network state detection sub-module specifically includes:
the first judgment unit is used for judging whether planned off-grid can be realized, and the judgment process comprises the following steps: whether the grid-connected point switch is electrified or not, whether the main grid of the grid-connected point switch is electrified or not and whether the microgrid is electrified or not are judged;
the first judgment result output unit is used for not executing planned off-grid when the battery is not charged;
the second judgment unit is used for judging whether the exchange power needs to be adjusted or not during electrification;
the second judgment result output unit is used for adjusting the switching power by the micro-grid operation controller when the switching power needs to be adjusted, and entering the first instruction issuing submodule;
if not, directly entering a first instruction issuing submodule.
Optionally, the grid-connected detection submodule specifically includes:
the third judgment unit is used for judging whether synchronization grid connection can be achieved or not, and the judgment process comprises the following steps: whether a grid-connected point switch sub-grid is electrified or not, whether a grid-connected point switch main grid is electrified or not and whether a micro-grid is electrified or not;
the third judgment result output unit is used for not executing synchronous grid connection when synchronous grid connection cannot be carried out;
and when the synchronization can be realized, entering a second instruction issuing submodule.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention adopts a seamless switching mode, namely, the seamless switching is realized by switching from off-grid to on-grid, planned off-grid and unplanned off-grid. The seamless switching means that in the process of grid-connected and off-grid switching, the voltage and the frequency of the microgrid are within the range specified by the microgrid operation standard, the voltage deviation of each bus in the microgrid is not greater than the rated voltage, the frequency deviation is not greater than the specified value, the microgrid can safely and stably operate, the uninterrupted power supply of important sensitive loads is ensured, and the reliability of power supply of users is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic configuration diagram of an energy storage microgrid grid-on and off-grid seamless switching system according to the invention;
fig. 2 is a flow chart of planned off-grid handover in embodiment 1 of the present invention;
FIG. 3 is a flow chart of synchronous grid-connection switching in embodiment 2 of the present invention;
fig. 4 is a flow chart of an unscheduled off-grid handover according to embodiment 3 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 only a part of the embodiments of the present invention, and not all of the embodiments. 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.
The invention aims to provide a device, a method and a system for seamless switching of grid connection and disconnection of an energy storage microgrid, and the device, the method and the system can solve the problem that seamless switching cannot be realized simultaneously when the microgrid is switched from a grid connection mode to a grid connection mode, and when the microgrid is switched from a planned grid connection mode and is not in a planned grid connection mode.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 1, an energy storage microgrid grid-on and off-grid seamless switching device comprises an operation controller, a grid-connected point switch, a grid-connected interface device, a stability control device and an energy storage PCS, wherein the operation controller is electrically connected with a main power supply and a microgrid,
the operation controller is used for receiving, translating and executing the control command to complete the operation control of the main and micro-grid;
the grid-connected point switch is positioned between the main power grid and the micro power grid;
the grid-connected interface device is used for controlling the on/off of a grid-connected point switch;
the stability control device is used for isolating the micro-grid from the main grid;
the energy storage PCS is used for switching the operation modes, detecting voltages on two sides of a grid-connected point and carrying out synchronization.
10kV/380V in FIG. 1 is a transformer, AC380V is a low-voltage AC bus, L1-L5 represents a branch line on the side of a micro-grid power supply, L1-1, L1-2 and L1-3 represent commercial power supply lines, L2-1, L2-2 and L2-3 represent micro-grid power supply lines, S1-S3 represent double-power-supply circuit breakers, and K1-K5 represent intelligent control switches.
Workflow of lines 1, 2: lines 1 and 2 are mains power supplies and are spare to each other. Under the condition that the microgrid is not used, S1-S3 are respectively connected with a mains supply line L1-1, L1-2 and L1-3, and mains supply supplies power to an electric load; under the condition that the microgrid is put into use, the S1-S3 is automatically switched to be connected with the L2-1, the L2-2 and the L2-3, the microgrid supplies power to the load, and the normal and stable operation of the microgrid system is maintained according to a grid-connected and off-grid operation strategy of the microgrid.
The invention adopts a seamless switching mode, namely, the seamless switching is realized by switching from off-grid to on-grid, planned off-grid and unplanned off-grid. The invention provides an energy storage microgrid grid-connected and off-grid seamless switching method which comprises the following steps:
when the microgrid runs off the grid, the stored energy is used as a main power supply to provide reference frequency for the microgrid. In order to ensure the off-grid stable operation of the micro-grid, the off-grid stable operation of the micro-grid is realized by coordinating the distribution among the distributed power supply, the load and the energy storage, and the reliable operation of important loads is supported for a certain time.
Planned off-grid mode:
step 11: the operation controller receives a planned off-grid instruction, specifically, when the planned off-grid instruction is issued by the microgrid energy management system, and the microgrid operation controller receives the planned off-grid instruction.
Step 12: the detection of the states of the grid-connected point switch, the main grid and the microgrid specifically comprises the following steps:
judging whether the planned off-grid can be realized, wherein the judging process comprises the following steps: whether the grid-connected point switch is electrified or not, whether the main grid of the grid-connected point switch is electrified or not and whether the microgrid is electrified or not are judged;
if not, not executing planned off-grid;
if so, judging whether the exchange power needs to be adjusted or not, namely controlling the tie line power and ensuring that the tie line power is in a power fluctuation range of a PCS (energy storage PCS) serving as a main power supply;
if yes, the microgrid operation controller adjusts the switching power and executes the step 13;
if not, directly executing step 13.
Step 13: the operation controller respectively issues planned off-grid instructions to the grid-connected interface device and mode switching instructions to the energy storage PCS;
step 14: and the grid-connected interface device controls the grid-connected point switch to be switched off, and the energy storage PCS is switched from the PQ operation mode to the V/f operation mode.
If the requirement of plan off-grid can be met through adjustment, the micro-grid connection interface device and the main PCS are matched to complete plan off-grid: the microgrid operation controller sends a planned off-grid instruction to the microgrid grid-connected interface device, and the microgrid grid-connected interface device controls the grid-connected point switch to be switched off; if the exchange power does not need to be adjusted, the microgrid operation controller sends a mode switching instruction to the energy storage PCS, and the energy storage PCS is switched to a V/f operation mode from a PQ operation mode.
And if the requirement of planned off-grid cannot be met through adjustment, the micro-grid operation controller returns a corresponding prompt. And finally finishing planned off-grid.
And when synchronization is carried out, a microgrid energy management system issues synchronization instructions. And the microgrid grid-connected interface device is matched with the main PCS to complete synchronous grid connection. When the synchronous grid-connected condition is met, the rapid switch is switched on, the micro-grid is connected to the grid, and meanwhile, the energy storage mode is switched from the V/f operation mode to the P/Q mode.
When the grid is connected, the internal power supply of the microgrid automatically uses itself, when the generated power is greater than the load power consumption, the redundant part preferentially charges the stored energy, and the rest of the electricity is connected to the Internet; when the power generation power is smaller than the power consumption power of the load, the stored energy is discharged to supplement the power shortage, and if the stored energy is not enough to supplement the power shortage, the power is taken from the power grid for supplement.
And when a grid-connected point fixed power control scheduling instruction is received, controlling the exchange power of the micro-grid and a distribution network connecting line to be a specified fixed value. When the exchange power is larger than a fixed value, the stored energy is charged to absorb the redundant power; when the exchange power is smaller than a fixed value, the stored energy discharge supplements the insufficient power.
And when a power limit control scheduling instruction is received, controlling the exchange power of the micro-grid and the power distribution network connecting line to be lower than a specified fixed value. When the exchange power is larger than the limit value, the energy storage charging absorbs the redundant power.
When the micro-grid is connected, a synchronous grid connection instruction is sent by the micro-grid energy management system, and synchronous grid connection is completed by matching the micro-grid connection interface device and the main PCS. When the synchronous grid-connected condition is met, the rapid switch is switched on, the micro-grid is connected to the grid, and meanwhile, the energy storage mode is switched from the V/f operation mode to the P/Q mode.
Grid connection mode:
step 21: the operation controller receives a synchronous grid-connected instruction;
step 22: detect the state of grid-connected point switch, major network and microgrid, specifically include:
judging whether synchronization grid connection can be achieved or not, wherein the judging process comprises the following steps: whether a grid-connected point switch sub-grid is electrified or not, whether a grid-connected point switch main grid is electrified or not and whether a micro-grid is electrified or not;
if not, synchronous grid connection is not executed;
if yes, go to step 23.
Step 23: the operation controller respectively gives synchronous closing instructions to the grid-connected interface device and gives synchronous adjusting instructions to the energy storage PCS;
step 24: the energy storage PCS detects voltages on two sides of a grid-connected point to carry out synchronization;
step 25: and the grid-connected interface device controls the switch-on of the grid-connected point switch, and the energy storage PCS is switched from the V/f operation mode to the PQ operation mode.
When the main network fails to cause unplanned off-grid, the microgrid grid-connected interface device firstly judges the failure and trips a grid-connected point switch through a protection action, the microgrid stability control device quickly adjusts the exchange power and quickly processes microgrid power fluctuation, meanwhile, the energy storage PCS is switched from a PQ operation mode to a V/f operation mode, and the unplanned off-grid is finished.
After the step 24 and before the step 25, further comprising:
judging whether a synchronous closing condition is met;
if yes, go to step 25;
if not, the procedure returns to step 24.
When the main network fails to cause unplanned off-network, entering an unplanned off-network mode:
step 31: detecting that a main network fails to cause unplanned off-network;
step 32: the grid-connected interface device controls the grid-connected point switch to be switched off, and specifically, the microgrid grid-connected interface device firstly judges a fault and trips the grid-connected point switch through a protection action.
Step 33: and the stability control device is used for quickly adjusting the exchange power (quickly processing the power fluctuation of the microgrid), and simultaneously, the energy storage PCS is switched from a PQ operation mode to a V/f operation mode.
Corresponding to the energy storage microgrid grid-connected and off-grid seamless switching method, the invention also provides an energy storage microgrid grid-connected and off-grid seamless switching system, which comprises the following steps:
planned off-grid module:
the off-grid instruction receiving submodule is used for receiving a planned off-grid instruction through the operation controller;
the off-grid state detection submodule is used for detecting the states of the grid-connected point switch, the main grid and the microgrid;
the first instruction issuing sub-module is used for respectively issuing planned off-grid instructions to the grid-connected interface device through the operation controller and issuing mode switching instructions to the energy storage PCS;
the first operation mode switching submodule is used for controlling the grid-connected point switch to be switched off through the grid-connected interface device, and the energy storage PCS is switched to a V/f operation mode from a PQ operation mode;
a grid connection module:
the grid-connected instruction receiving submodule is used for receiving a synchronous grid-connected instruction through the operation controller;
the grid-connected detection submodule is used for detecting the states of the grid-connected point switch, the main grid and the microgrid;
the second instruction issuing submodule is used for operating the controller to respectively issue synchronous closing instructions to the grid-connected interface device and issue synchronous adjusting instructions to the energy storage PCS;
the synchronization sub-module is used for detecting voltages on two sides of the grid-connected point through the energy storage PCS to perform synchronization;
the second operation mode switching module is used for controlling the switching-on of the grid-connected point switch through the grid-connected interface device, and the energy storage PCS is switched from the V/f operation mode to the PQ operation mode;
unscheduled off-grid module:
the unplanned off-grid generation sub-module is used for detecting that the main network fails to cause unplanned off-grid;
the grid-connected point switch opening control submodule is used for controlling the grid-connected point switch opening through the grid-connected interface device;
and the third operation mode switching submodule is used for stabilizing the control device, quickly adjusting the switching power, and simultaneously switching the energy storage PCS from the PQ operation mode to the V/f operation mode.
The off-network state detection submodule specifically comprises:
the first judgment unit is used for judging whether planned off-grid can be realized, and the judgment process comprises the following steps: whether the grid-connected point switch is electrified or not, whether the main grid of the grid-connected point switch is electrified or not and whether the microgrid is electrified or not are judged;
the first judgment result output unit is used for not executing planned off-grid when the battery is not charged;
the second judgment unit is used for judging whether the exchange power needs to be adjusted or not during electrification;
the second judgment result output unit is used for adjusting the switching power by the micro-grid operation controller when the switching power needs to be adjusted, and entering the first instruction issuing submodule;
if not, directly entering a first instruction issuing submodule.
The grid connection detection submodule specifically comprises:
the third judgment unit is used for judging whether synchronization grid connection can be achieved or not, and the judgment process comprises the following steps: whether a grid-connected point switch sub-grid is electrified or not, whether a grid-connected point switch main grid is electrified or not and whether a micro-grid is electrified or not;
the third judgment result output unit is used for not executing synchronous grid connection when synchronous grid connection cannot be carried out;
and when the synchronization can be realized, entering a second instruction issuing submodule.
The invention has the advantages that:
(1) the voltage deviation of the common connection point does not exceed +/-7% of the nominal voltage, and the frequency deviation is +/-0.2 Hz. The power factor of the microgrid bus is controlled to be 0.98 (leading) to 0.98 (lagging).
(2) The deviation of the three-phase power supply voltage is +/-7% of the nominal voltage. When the power grid normally operates, the negative sequence voltage unbalance degree does not exceed 2%, and the short-time negative sequence voltage unbalance degree does not exceed 4%. When the power system normally operates, the frequency deviation cannot exceed +/-0.2 Hz. When the power system normally operates, the total harmonic distortion rate of the voltage does not exceed 5 percent.
(3) And 4, the micro-grid is switched in parallel and off-grid seamless mode, and the whole switching process is completed within 10 ms.
Example 1:
as shown in fig. 2, the embodiment provides a specific planned off-grid method, which specifically includes:
the NMC1000 microgrid energy management system issues a planned off-grid instruction, and the NMC8100 microgrid operation controller receives the planned off-grid instruction;
judging whether the off-grid can be planned or not, namely judging whether a grid-connected point switch is closed or not, whether a main grid is electrified or not and whether a microgrid is electrified or not;
if not, not executing planned off-grid;
if yes, judging whether the exchange power needs to be adjusted;
if so, the NMC8100 micro-grid operation controller adjusts the exchange power;
if not, the NMC8100 microgrid operation controller respectively gives a planned off-grid instruction to the NMC8601 microgrid grid-connected interface device and a mode switching instruction to the energy storage PCS;
and the NMC8601 microgrid grid-connected interface device controls the grid-connected point switch to open, the energy storage PCS is switched to a V/f operation mode from a PQ operation mode, and the planned off-grid operation is finished.
Example 2:
as shown in fig. 3, the embodiment provides a specific grid connection method, which specifically includes:
the NMC1000 micro-grid energy management system sends a synchronous grid connection instruction, and the NMC8100 operation controller receives the synchronous grid connection instruction;
judging whether the synchronous grid-connected condition is met, namely judging whether a grid-connected point switch is a branch, whether a main grid is electrified or not and whether a microgrid is electrified or not;
if not, synchronous grid connection is not executed;
if yes, the NMC8100 micro-grid operation controller respectively gives synchronous closing instructions to the NMC8601 micro-grid-connected interface device, and the NMC8100 micro-grid operation controller gives synchronous adjusting instructions to the energy storage PCS;
the energy storage PCS detects voltages on two sides of a grid-connected point and carries out synchronization;
whether the synchronous closing condition is met or not;
if yes, the NMC8601 micro-grid-connected interface device controls a grid-connected point switch to be switched on, the energy storage PCS is switched from a V/f operation mode to a PQ operation mode, and grid connection is finished at the same time;
if not, returning to the energy storage PCS to detect the voltages at the two sides of the grid-connected point, and carrying out synchronization.
Example 3:
as shown in fig. 4, the embodiment provides a specific unscheduled off-grid method, which specifically includes:
when the main network fails to cause unplanned grid disconnection, the NMC8601 microgrid grid-connected interface device judges the failure firstly and trips a grid-connected point switch through a protection action, the NMC8603 microgrid stability control device quickly adjusts exchange power and quickly processes microgrid power fluctuation, meanwhile, the energy storage PCS is switched from a PQ operation mode to a V/f operation mode, and unplanned grid disconnection is finished.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (8)
1. An energy storage microgrid grid-on and off-grid seamless switching device is characterized by comprising an operation controller, a grid-connected point switch, a grid-connected interface device, a stability control device and an energy storage PCS which are electrically connected with a main power supply and a microgrid,
the operation controller is used for receiving, translating and executing the control command to complete the operation control of the main and micro-grid;
the grid-connected point switch is positioned between the main power grid and the micro power grid;
the grid-connected interface device is used for controlling the on/off of a grid-connected point switch;
the stability control device is used for isolating the micro-grid from the main grid;
the energy storage PCS is used for switching the operation modes, detecting voltages on two sides of a grid-connected point and carrying out synchronization.
2. An energy storage microgrid grid-on and grid-off seamless switching method is based on the energy storage microgrid grid-on and grid-off seamless switching device of claim 1, and the method comprises the following steps:
planned off-grid mode:
step 11: the operation controller receives a planned off-network instruction;
step 12: detecting the states of the grid-connected point switch, the main network and the microgrid;
step 13: the operation controller respectively issues planned off-grid instructions to the grid-connected interface device and mode switching instructions to the energy storage PCS;
step 14: the grid-connected interface device controls the grid-connected point switch to be switched off, and the energy storage PCS is switched from a PQ operation mode to a V/f operation mode;
grid connection mode:
step 21: the operation controller receives a synchronous grid-connected instruction;
step 22: detecting the states of the grid-connected point switch, the main network and the microgrid;
step 23: the operation controller respectively gives synchronous closing instructions to the grid-connected interface device and gives synchronous adjusting instructions to the energy storage PCS;
step 24: the energy storage PCS detects voltages on two sides of a grid-connected point to carry out synchronization;
step 25: the grid-connected interface device controls a grid-connected point switch to be switched on, and the energy storage PCS is switched from a V/f operation mode to a PQ operation mode;
unplanned off-grid mode:
step 31: detecting that a main network fails to cause unplanned off-network;
step 32: the grid-connected interface device controls the opening and closing of the grid-connected point switch;
step 33: and the stability control device is used for rapidly adjusting the exchange power, and simultaneously, the energy storage PCS is switched from the PQ operation mode to the V/f operation mode.
3. The energy storage microgrid grid-on and grid-off seamless switching method according to claim 2, wherein the step 12 specifically comprises:
judging whether the planned off-grid can be realized, wherein the judging process comprises the following steps: whether the grid-connected point switch is electrified or not, whether the main grid of the grid-connected point switch is electrified or not and whether the microgrid is electrified or not are judged;
if not, not executing planned off-grid;
if yes, judging whether the exchange power needs to be adjusted;
if yes, the microgrid operation controller adjusts the switching power and executes the step 13;
if not, directly executing step 13.
4. The energy storage microgrid grid-on and grid-off seamless switching method according to claim 2, wherein the step 22 specifically comprises:
judging whether synchronization grid connection can be achieved or not, wherein the judging process comprises the following steps: whether a grid-connected point switch sub-grid is electrified or not, whether a grid-connected point switch main grid is electrified or not and whether a micro-grid is electrified or not;
if not, synchronous grid connection is not executed;
if yes, go to step 23.
5. The energy storage microgrid grid-on and grid-off seamless switching method according to claim 2, characterized in that after the step 24 and before the step 25, the method further comprises:
judging whether a synchronous closing condition is met;
if yes, go to step 25;
if not, the procedure returns to step 24.
6. An energy storage microgrid grid-on and off-grid seamless switching system is characterized by comprising:
planned off-grid module:
the off-grid instruction receiving submodule is used for receiving a planned off-grid instruction through the operation controller;
the off-grid state detection submodule is used for detecting the states of the grid-connected point switch, the main grid and the microgrid;
the first instruction issuing sub-module is used for respectively issuing planned off-grid instructions to the grid-connected interface device through the operation controller and issuing mode switching instructions to the energy storage PCS;
the first operation mode switching submodule is used for controlling the grid-connected point switch to be switched off through the grid-connected interface device, and the energy storage PCS is switched to a V/f operation mode from a PQ operation mode;
a grid connection module:
the grid-connected instruction receiving submodule is used for receiving a synchronous grid-connected instruction through the operation controller;
the grid-connected detection submodule is used for detecting the states of the grid-connected point switch, the main grid and the microgrid;
the second instruction issuing submodule is used for operating the controller to respectively issue synchronous closing instructions to the grid-connected interface device and issue synchronous adjusting instructions to the energy storage PCS;
the synchronization sub-module is used for detecting voltages on two sides of the grid-connected point through the energy storage PCS to perform synchronization;
the second operation mode switching module is used for controlling the switching-on of the grid-connected point switch through the grid-connected interface device, and the energy storage PCS is switched from the V/f operation mode to the PQ operation mode;
unscheduled off-grid module:
the unplanned off-grid generation sub-module is used for detecting that the main network fails to cause unplanned off-grid;
the grid-connected point switch opening control submodule is used for controlling the grid-connected point switch opening through the grid-connected interface device;
and the third operation mode switching submodule is used for stabilizing the control device, quickly adjusting the switching power, and simultaneously switching the energy storage PCS from the PQ operation mode to the V/f operation mode.
7. The energy storage microgrid grid-connected and off-grid seamless switching system of claim 6, wherein the off-grid state detection submodule specifically comprises:
the first judgment unit is used for judging whether planned off-grid can be realized, and the judgment process comprises the following steps: whether the grid-connected point switch is electrified or not, whether the main grid of the grid-connected point switch is electrified or not and whether the microgrid is electrified or not are judged;
the first judgment result output unit is used for not executing planned off-grid when the battery is not charged;
the second judgment unit is used for judging whether the exchange power needs to be adjusted or not during electrification;
the second judgment result output unit is used for adjusting the switching power by the micro-grid operation controller when the switching power needs to be adjusted, and entering the first instruction issuing submodule;
if not, directly entering a first instruction issuing submodule.
8. The energy storage microgrid grid-on and grid-off seamless switching system of claim 6, wherein the grid-connected detection submodule specifically comprises:
the third judgment unit is used for judging whether synchronization grid connection can be achieved or not, and the judgment process comprises the following steps: whether a grid-connected point switch sub-grid is electrified or not, whether a grid-connected point switch main grid is electrified or not and whether a micro-grid is electrified or not;
the third judgment result output unit is used for not executing synchronous grid connection when synchronous grid connection cannot be carried out;
and when the synchronization can be realized, entering a second instruction issuing submodule.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113346550A (en) * | 2021-07-16 | 2021-09-03 | 阳光电源股份有限公司 | Optical storage networking system control method and application device thereof |
| CN114123181A (en) * | 2021-11-24 | 2022-03-01 | 许继集团有限公司 | Mode switching control method and device for power distribution network flexible loop closing device |
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2021
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113346550A (en) * | 2021-07-16 | 2021-09-03 | 阳光电源股份有限公司 | Optical storage networking system control method and application device thereof |
| CN113346550B (en) * | 2021-07-16 | 2024-04-12 | 阳光电源股份有限公司 | Optical storage networking system control method and application device thereof |
| CN114123181A (en) * | 2021-11-24 | 2022-03-01 | 许继集团有限公司 | Mode switching control method and device for power distribution network flexible loop closing device |
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