CN116526543A - Island direct-current micro-grid control system and cooperative control method thereof - Google Patents
Island direct-current micro-grid control system and cooperative control method thereof Download PDFInfo
- Publication number
- CN116526543A CN116526543A CN202211259877.3A CN202211259877A CN116526543A CN 116526543 A CN116526543 A CN 116526543A CN 202211259877 A CN202211259877 A CN 202211259877A CN 116526543 A CN116526543 A CN 116526543A
- Authority
- CN
- China
- Prior art keywords
- micro
- grid
- load
- control
- energy storage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000004146 energy storage Methods 0.000 claims abstract description 88
- 230000007246 mechanism Effects 0.000 claims abstract description 7
- 238000007600 charging Methods 0.000 claims description 19
- 238000004891 communication Methods 0.000 claims description 17
- 238000011217 control strategy Methods 0.000 claims description 13
- 238000006243 chemical reaction Methods 0.000 claims description 11
- 230000001960 triggered effect Effects 0.000 claims description 9
- 238000004364 calculation method Methods 0.000 claims description 8
- 238000009826 distribution Methods 0.000 claims description 4
- 230000003993 interaction Effects 0.000 claims description 4
- 230000001502 supplementing effect Effects 0.000 claims description 4
- 230000000295 complement effect Effects 0.000 claims description 3
- 230000005540 biological transmission Effects 0.000 claims description 2
- 238000004422 calculation algorithm Methods 0.000 claims description 2
- 230000007613 environmental effect Effects 0.000 claims description 2
- 238000012545 processing Methods 0.000 claims description 2
- 238000010248 power generation Methods 0.000 abstract description 21
- 210000004027 cell Anatomy 0.000 description 96
- 238000010586 diagram Methods 0.000 description 16
- 210000000352 storage cell Anatomy 0.000 description 10
- 238000005286 illumination Methods 0.000 description 7
- 230000006870 function Effects 0.000 description 5
- 238000004088 simulation Methods 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 230000008520 organization Effects 0.000 description 4
- 230000002035 prolonged effect Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 3
- 238000012795 verification Methods 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000013486 operation strategy Methods 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005381 potential energy Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- 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
-
- 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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00001—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by the display of information or by user interaction, e.g. supervisory control and data acquisition systems [SCADA] or graphical user interfaces [GUI]
-
- 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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
-
- 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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
-
- 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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
- H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Human Computer Interaction (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention discloses an island direct current micro-grid control system and a cooperative control method thereof, wherein the island direct current micro-grid control system comprises a central unit and a subunit, wherein the central unit is used for centralized control of all mechanisms in the subunit; the subunit comprises two photovoltaic generator sets for supplying energy loads of the micro-grid, two energy storage batteries for storing first standby capacity of the direct-current micro-grid, a micro gas turbine for storing second standby capacity of the direct-current micro-grid, and comprehensive loads for detecting load voltage and adjusting load current, and the central unit and the subunits and each mechanism of the subunits can be communicated. And the common knowledge and coordination among all units are ensured, and the voltage stability of the island direct current micro-grid is effectively improved. Meanwhile, photovoltaic power generation is utilized to the maximum extent, the energy storage unit is called at any time, the gas turbine unit is used as the strongest backup, and the system can meet the requirement of supply and demand balance.
Description
Technical Field
The invention relates to the field of micro-grid control, in particular to an island direct-current micro-grid control system and a cooperative control method thereof.
Background
With the increasing global energy demand, efficient utilization of renewable energy is becoming more and more important, and the permeability of new energy is becoming higher and higher. Photovoltaic power generation is one of the most potential energy sources in new energy sources, and is also an important technology for 'energy conservation and emission reduction', but the photovoltaic power generation can have an uncoordinated integration mode, so that a plurality of technical strategies are challenged, and some outstanding problems include worsening photovoltaic fluctuation, unbalanced voltage, reduction of frequency reserves and the like.
The micro-grid is an interconnected low-voltage network formed by load, distributed power supply, energy storage, micro gas turbine and other units, and is an effective way for coordinated use of photovoltaic power generation. Among other things, the dc microgrid has the main advantages of: because the photovoltaic generator set, the energy storage system, the load and the like are connected into the direct-current micro-grid only once DC/DC or AC/DC conversion is needed, the converter has a simple control structure and is more efficient; the direct current micro-grid has no problems of synchronization, harmonic wave, frequency adjustment, reactive power and the like; the energy control in the direct current micro-grid depends on the direct current bus voltage, so that the coordination control of each unit in the system center is realized; the energy storage device in the direct current micro-grid can track the change of the load, so that the energy change in the system is balanced, and continuous power supply is provided for the load during island operation, and the load is not influenced by the faults of the large power grid. Therefore, the direct current micro grid is an effective method capable of absorbing new energy and improving the utilization rate thereof.
However, the new energy has the characteristics of non-schedulability, random volatility and anti-peak shaving; meanwhile, the comprehensive load also has random fluctuation and instability; the uncertainty of operation scheduling of the direct current micro-grid system is increased together, and the stable operation of various working conditions is difficult to ensure by the existing control method. In addition, most of new energy sources are put into a distributed mode, the information sharing span among components is large, the global property and accuracy of information acquisition cannot be guaranteed by the existing coordination control optimization method, and the convergence speed is relatively low. The problem of cooperative control at the demand side is that the existing optimization method cannot balance contradiction among control targets and cannot guarantee coordination among different components.
Disclosure of Invention
In view of the above, the present invention provides an island direct current micro-grid control system and a cooperative control method thereof, which aims to solve the technical problems of how to improve the voltage stability of the island direct current micro-grid and how to realize the supply and demand balance of the control system.
In order to solve the technical problems, the technical scheme of the invention is to provide an island direct current micro-grid control system and a cooperative control method thereof, comprising the following steps:
the central unit is used for centralized control of all mechanisms in the sub units; the subunit comprises two photovoltaic generator sets for supplying energy loads of the micro-grid, two energy storage batteries for storing first standby capacity of the direct-current micro-grid, a micro gas turbine for storing second standby capacity of the direct-current micro-grid, and comprehensive loads for detecting load voltage and adjusting load current, and the central unit and the subunits and each mechanism of the subunits can be communicated.
Optionally, the central unit comprises a communication module, a database module and an inference calculation module, wherein the communication module is used for collecting the output information of each subunit and issuing a control command to each subunit; the database module is used for storing real-time state data information uploaded by each subunit; the reasoning calculation module is used for giving a setting value adjustment quantity by adopting a control algorithm according to the current acquired information and the system state and reasoning out the output of each subunit which should be adjusted and executed.
Optionally, the subunit comprises a sensing module, a communication module, a database module and an execution module, wherein the sensing module is used for collecting environmental information; the communication module is used for information exchange among different components in the subunit and information transmission with the central unit; the database module is used for storing the state data of the corresponding components and the received information, processing the acquired information in a centralized way and sending a final control command to the execution module through logic reasoning; the execution module is used for converting the control command into actual output PWM.
Optionally, the photovoltaic generator set has two operation strategies of photovoltaic Maximum Power Point Tracking (MPPT) control and constant voltage control.
Optionally, the power of the micro gas turbine is adjustable.
Optionally, the first reserve capacity of the stored energy is preferentially used for the second reserve capacity of the micro gas turbine.
Optionally, the integrated load has only a power output and no power input.
Optionally, the present application further provides a control strategy based on an island direct current micro-grid control system, specifically,
first mode: when P PV ≥P load &SOC total ≥SOC max And when the micro gas turbine is dormant, the photovoltaic generator set operates under constant pressure control, and the energy storage system is dormant. The power flow of the system after steady state is: p (P) PV ＝P Load ；
Second mode: when P PV ≥P load &SOC total ＜SOC max And when the micro gas turbine is dormant, the photovoltaic generator set is controlled to operate by MPPT, and the energy storage system is in a charging state. The power flow of the system after steady state is: p (P) PV ＝P Load +P Battery ；
Third mode: when P PV ＜P load &SOC total ≥SOC min When the energy storage system is used for supplementing the power shortage firstly, then the micro gas turbine increases the output, the energy storage system continues to discharge, and the photovoltaic generator set is controlled to operate by MPPT. The power flow of the system after steady state is: p (P) PV +P MT +P Battery ＝P Load ；
Fourth mode: when P PV ＜P load &SOC total ＜SOC min When the micro gas turbine is in use, the micro gas turbine is required to complement the power shortage and also is required to charge the energy storage system; the photovoltaic generator set is controlled to operate by MPPT. The power flow of the system after steady state is: p (P) PV +P MT ＝P Load +P Battery 。
Optionally, a mode conversion strategy is also provided, specifically,
first mode conversion: when SOC is total ≥SOC max The energy of the photovoltaic generator set is sufficient, the energy storage system can be fully charged, and the second mode is converted into the first mode;
second mode conversion: when SOC is total ＜SOC min The system is too empty and the energy storage system has reached the lower SOC limit when temporarily replenishing power, and the third mode is switched to the fourth mode.
In addition, the application also provides an island direct current micro-grid cooperative control method which is applied to the island direct current micro-grid control system, and comprises the following steps:
(1) The central unit receives the real-time state information uploaded by each subunit, and the subunits interact with each other in real-time state information;
(2) The central unit calculates the power allocation amount according to the received real-time state information uploaded by each subunit, and determines a control mode;
(3) The central unit sends control instructions corresponding to the power distribution amounts of the subunits to the subunits so that the subunits can be controlled according to the control instructions;
(4) And (3) repeating the steps (1), (2) and (3) when the control instruction is ended and a new round of information interaction is triggered.
The invention provides an island direct current micro-grid control system and a cooperative method thereof, which consider the overcharge and overdischarge of an energy storage system, the balance of SOC and the maximum utilization rate of photovoltaic power generation and realize the balance between the two; meanwhile, the standby adjustable power of the micro gas turbine is introduced to maximally meet supply and demand balance and inhibit serious fluctuation of photovoltaic power generation under special conditions, the cooperative control method can sense global information, power distribution among photovoltaic power generation units, among photovoltaic power generation and micro gas turbine systems and among energy storage systems is realized, different control modes can be smoothly switched through a centralized cooperative control strategy, adjustment of public direct current bus voltage and reliable operation of a micro power grid under different operation conditions are effectively ensured, meanwhile, photovoltaic power generation is maximally utilized, an energy storage unit is called at any time, the gas turbine unit serves as the strongest backup, and the system can meet the requirement of supply and demand balance.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of 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 application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a typical DC micro-grid structure according to an embodiment of the present application;
fig. 2 is a schematic diagram of steps of an island dc micro-grid control method according to an embodiment of the present disclosure;
FIG. 3 is a schematic control diagram of a photovoltaic generator set according to an embodiment of the present disclosure;
FIG. 4 is a schematic diagram of a micro gas turbine control provided in an embodiment of the present application;
FIG. 5 is a schematic diagram of an energy storage system according to an embodiment of the present disclosure;
FIG. 6 is a schematic diagram of a cell flow diagram of a central control cell according to one embodiment of the present disclosure;
FIG. 7 is a schematic diagram of a cell flow of an energy storing cell according to an embodiment of the present disclosure;
FIG. 8 is a schematic cell flow diagram of a micro gas turbine cell according to one embodiment of the present disclosure;
FIG. 9 is a schematic diagram of a cell flow diagram of a photovoltaic cell according to an embodiment of the present disclosure;
FIG. 10 is a schematic diagram of a cell flow diagram of an integrated load cell according to one embodiment of the present application.
Detailed Description
In order that those skilled in the art will better understand the embodiments of the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The application adopts a typical direct current micro-grid structure, as shown in fig. 1, and is a schematic diagram of the typical direct current micro-grid structure provided by the embodiment, which comprises two photovoltaic generator sets, a micro gas turbine, two energy storage batteries and a comprehensive load.
Photovoltaic power generation energy is the main energy source for supplying loads in micro-grids, and there are two operation strategies: photovoltaic Maximum Power Point Tracking (MPPT) control, constant voltage control. When the photovoltaic power generation power is larger than the power required by the system (enough to supply load and store energy to be full), adopting a constant voltage control strategy; otherwise, the photovoltaic power generation systems all adopt MPPT control strategies. As shown in fig. 3, the photovoltaic unit may obtain a message: the power required by the system; after receiving the information, in the mode selection, firstly, selecting a local control strategy: when the MPPT control mode is selected, the photovoltaic unit performs tracking control of the maximum power point according to the photovoltaic irradiance at the moment; when the constant voltage control mode is selected, the photovoltaic unit performs double-closed-loop tracking control according to the direct current bus voltage signal at the moment. After the mode is selected, the command output is directly controlled to perform local control, and the two control modes are used for maximizing the utilization of light energy on the premise of ensuring the voltage stability of the direct current bus. When using the constant voltage control strategy, the maintenance power of the bus voltage is:
wherein V is dc For bus voltage, I dc_i To flow into the ith PV current, Z dc_i For the resistance on its line,k is the reference value of bus voltage i Is the sag factor.
The micro gas turbine will provide sufficient backup capacity for the entire dc micro grid and the power of the micro gas turbine is adjustable to adequately respond to load demands, improving the supply reliability of the system. As shown in fig. 4, a micro gas turbine unit (MTUnit) will obtain two pieces of information: power boost amount, sleep signal; after receiving the information, the control command converts the received information into an actual adjustment quantity, then the actual adjustment quantity is sent into a gas compressor combustion chamber, fuel supply, temperature control, speed control and acceleration control are carried out in the gas compressor combustion chamber according to the adjustment quantity, new power (torque quantity) is generated and sent into a prime mover, the prime mover outputs a control signal to carry out local control, meanwhile, the control signal of the prime mover also feeds back the control command, whether the control signal is matched with a system command or not is detected, and a strong backup is provided for a direct current micro-grid.
The energy storage system comprises two energy storage batteries, and the two energy storage batteries are used as spare capacity in the direct-current micro-grid, and when the photovoltaic system has sufficient power generation, the energy storage system is charged in order to fully utilize the photovoltaic power; when the photovoltaic system is insufficient in power generation, in order to be able to respond to load demands in time, enough response time is provided for the micro gas turbine unit to generate power, and the energy storage system is discharged. As shown in fig. 5, the energy storage Unit (BE Unit) receives two messages: issuing power information and adjacent energy storage information; the received two pieces of information are calculated in a calculation unit to obtain the current charge and discharge power, so that the SOC (state of charge) balance between the energy storage units of the system can be kept, and the overcharge and overdischarge of a single energy storage unit are avoided; then the control power reaches the local through an external power loop, the SOC is adjusted through droop control, and the adjusted information is stored in a database so as to be called at the next moment; the purpose of re-uploading the current SOC state information is to enable the system to update the state of stored energy so as to output accurate control instructions later.
The load refers to an electronic element which is connected to two ends of a circuit and has a certain potential difference in physics and is used for converting electric energy into energy in other forms, in the embodiment, the comprehensive load is equipment for receiving electric energy in the circuit, self information of the comprehensive load comprises impedance matching and affordable power information, whether overload conditions occur in a control system is judged according to the comprehensive load information, safety accidents are avoided, meanwhile, the condition that power overload or surplus conditions occur in a micro-grid system is avoided based on information transmitted by the comprehensive load, the photovoltaic power generation is guaranteed to be maximally utilized, and the system can maintain supply and demand balance.
Further, the conventional method for controlling the micro-grid includes centralized control and autonomous control, wherein the autonomous control is more suitable for the flexible characteristic of plug-and-play of a distributed power generation device in the micro-grid, but the high load/power generation change rate caused by the increase of the new energy permeability and the increase of the scale of the distributed micro-grid make the autonomous control unable to ensure the voltage quality in the micro-grid and the stable operation of the micro-grid.
Mode one: when P PV ≥P load &SOC total ≥SOC max And when the micro gas turbine unit is dormant, the photovoltaic generator unit operates under constant pressure control, and the energy storage system is dormant. The power flow of the system after steady state is: p (P) PV ＝P Load . In the mode, only the photovoltaic generator set supplies a load, the direct-current bus voltage is maintained by the photovoltaic generator set, the two groups of PVs are operated by adopting constant-voltage control, and the distributed power is the load power P Load 。
Mode two: when P PV ≥P load &SOC total ＜SOC max And when the micro gas turbine unit is dormant, the photovoltaic generator unit is controlled to operate by MPPT, and the energy storage system is in a charging state. The power flow of the system after steady state is: p (P) PV ＝P Load +P Battery . In this mode, the photovoltaic generator sets need not only supply load, but also supply the remaining power to the energy storage system for charging to increase emergency standby, and the distributed power of each photovoltaic generator set is respectivelyAnd P PV_2 ＝1-P PV_1 . It should be noted that, the power transmitted at this time is only the power meeting the load requirement, and is not the power generated by the photovoltaic generator set, and the remaining power is sent to the energy storage system.
Mode three: when P PV ＜P load &SOC total ≥SOC min When the energy storage system is used for supplementing the power shortage firstly, then the micro gas turbine increases the output, the energy storage system continues to discharge, and the photovoltaic generator set is controlled to operate by MPPT. The power flow of the system after steady state is: p (P) PV +P MT +P Battery ＝P Load . The power of the micro gas turbine is:
P MT ＝P Load -P PV1 -P PV2 -P Battery 。
mode four: when P PV ＜P load &SOC total ＜SOC min When the micro gas turbine is in use, the micro gas turbine is required to complement the power shortage and also is required to charge the energy storage system; the photovoltaic generator set is controlled to operate by MPPT. The power flow of the system after steady state is: p (P) PV +P MT ＝P Load +P Battery . In this mode, the power of the photovoltaic generator set is supplied to the load entirely, then the remaining power is complemented by the micro gas turbine, then the remaining power of the micro gas turbine charges the energy storage system, and the distributed power of each distributed power supply is as follows:
micro gas turbine unit: p (P) MT ＝P Load_MT +P Battery ；
A first photovoltaic generator: p (P) PV_1 ＝P Load_1 ；
And a second photovoltaic generator: p (P) PV_2 ＝P Load_2 ；
Comprehensive load: p (P) Load ＝P Load_MT +P Load_1 +P Load_2 。
In the secondary cooperative control, because the corresponding speed of the micro gas turbine is lower than that of the energy storage system, if the system is in shortage, no energy storage system is supplemented in time, and the time for recovering the voltage is prolonged only by the force of one turbine, so that the condition of the mode four should be avoided as much as possible in actual operation. In addition, in addition to the four natural modes described above, there are two cases of mode conversion:
conversion one: when SOC is total ≥SOC max The photovoltaic generator set has sufficient energy, and the energy storage system can reach full charge, and the mode is converted into the mode I.
Conversion II: when SOC is total ＜SOC min The system is too large in shortage, and the energy storage system reaches the lower limit of the SOC when temporarily supplementing power, so that the mode is converted into the three-way mode four.
It should be noted that, due to the difference of assembly capacity, production process and the like, there may be a difference of SOC, in order to prolong the service life of the energy storage system and maintain the balance of SOC, in this embodiment, a balanced charging manner is adopted, and when a unit with a large capacity discharges, the SOC drops more and discharges faster; and vice versa.
The average value of SOC is:
in discharge mode:
in the charging mode:
wherein, p is the convergence rate of adjusting the SOC balance, and the higher the p value, the faster the convergence.
Further, in order to implement the above-mentioned two-level cooperative control strategy, the present embodiment introduces a novel organization P system as an infrastructure for communication and information sharing, where the organization P system is in a network structure, and is composed of a plurality of cells, and each cell includes a plurality of data (or variables) and a plurality of rules, and is a distributed parallel computing model or system. Based on the direct-current micro-grid structure provided by the application, a cell structure diagram of the direct-current micro-grid control system shown in fig. 6 is obtained.
The cell structure of the direct current micro-grid control system comprises a central control cell, two energy storage cells, photovoltaic cells, micro gas turbine cells and comprehensive load cells, wherein the two energy storage cells respectively correspond to the two energy storage cells; the number of the photovoltaic cells is two, and the photovoltaic cells correspond to two photovoltaic generator sets respectively. The central control cell is used as a central cell, the rest 6 cells respectively correspond to 6 constituent units of the micro-grid, the communication between every two cells is completed by a communication rule, the function of the communication rule is that the information exchange and sharing between the central cell and the unit cells or between the two unit cells are realized by a physical network. Each directional arc in the illustration reflects the communication relationship between two cells, and the direction of the arrow is the direction of communication. Each cell typically contains a set of evolution rules. The evolution rules are used to evolve the state (or variable) of the cell. In handling the actual application, the evolution rules are often implemented as a program (program) that performs the given function.
The central control cell is responsible for collecting information of all other control units, a control instruction is obtained through the calculation module and the logic judgment module, and then the control instruction is fed back to each control unit through the communication module, so that overall information is mastered;
the energy storage cells need to transmit self SOC information to the central control cells and adjacent energy storage cells, and simultaneously receive control commands issued by the central control cells and the SOC information of the adjacent energy storage cells, so that SOC balance among the energy storage units is realized, and DC bus voltage fluctuation caused by photovoltaic power generation fluctuation and load fluctuation is reduced;
the photovoltaic cells receive the central control cell command and the information of the comprehensive load cells, and then determine the control mode of the photovoltaic module through the logic judgment module to maintain coordination among the photovoltaic units;
the micro gas turbine cell determines a self-sleep state or provides power according to a command of receiving the central control cell, and can keep coordination between the micro gas turbine and photovoltaic power generation when an emergency occurs;
the load cells are synthesized, the power information of the load cells is uploaded to the central control cells and the photovoltaic cells, the central control cells can conveniently acquire global information, and accurate control instructions are implemented; while facilitating the selection of the proper control mode by the photovoltaic cells.
Further, as shown in fig. 2, the schematic step diagram of the control method of the island direct current micro-grid provided in an embodiment of the present application, in the coordinated voltage control based on the organization P system, the corresponding steps of implementing information sharing in the two-level coordination control by combining with the control method include:
(1) At t=0, i.e. parameter initialization, each elementary cell transmits its own initial status information to the central control cell, specifically: the central control cell receives initial parameters of each unit cell; the two energy storage unit cells exchange the energy storage state SOC and respectively upload the energy storage state SOC of each energy storage unit cell to the central control cell; initial power P of MT uploaded by micro gas turbine unit cell to central control cell MT The integrated load unit cell will initially load power information P Load The initial load power information is respectively output to the central control cell and the two photovoltaic unit cells, and the two photovoltaic unit cells respectively upload the initial powers to the central control cell while receiving the initial load power information of the comprehensive load unit cells.
(2) At the time t, the central control cell calculates the power allocation amount according to the information input at the time t-1, and after the calculation is finished, a rule is triggered; the gas turbine cell, the photovoltaic cell and the energy storage cell firstly carry out local control according to the information received at the time t-1, when the local control finishes outputting signals to the environment, new sampling is triggered, and the rule in the input value is triggered by the sampled input value; the load cell has no input and only output, so that in this period, after outputting the signal, a new sampling is performed, triggering the rule. The triggering of this moment of time comprises two rules, one consisting in the communication rules of the information interaction between the cells and the other consisting in the evolution rules of the cells themselves, often implemented as a program to accomplish a given task or function.
(3) At time t+1, each cell receives new information interaction, and performs new calculation, distribution and control, that is, the step (2) is repeated to maintain the stability of the bus voltage.
The above steps are described in more detail below in conjunction with the flow chart of each cell
Referring to fig. 6, a flow chart of a central control cell is shown, wherein the central control cell transmits all collected information to other cells through a communication network after the central control cell infers the collected information through a computing unit and corresponding logic and triggers a rule.
As shown in fig. 7, a flow chart of the energy storage cell is shown, wherein the energy storage cell is to receive two information at time t, one information is from the central control cell, and the other information is from each other, wherein the information sent by the central control cell is divided into two types, and when the signal information is SOC, the energy storage cell is in a charging or discharging state, and the system is in a second mode, a third mode or a fourth mode; when the received signal is x (x represents a sleep signal), it represents that the energy storage is in a sleep state, and it represents that the system is now in mode one. After the received information is determined, a rule is triggered, and a punishment rule is used for giving a reference value to the local control, so that the adjustment of a local control mechanism is triggered. And then at the time t+1, information is sent to the central control cell and the adjacent unit cells, and the cells circulate in turn.
As shown in FIG. 8, the micro gas turbine cell flow chart is that the micro gas turbine cell receives a single message, which is only the message P sent from the central control cell MT The local control is triggered after the receiving, and when the local control is operated to the reference value, the information P is sent to the central control cell at the time t+1 MT 。
The photovoltaic cell flow chart is shown in fig. 9, the two pieces of received information are two, one is from the central control cell and the other is from the comprehensive load cell, the central control cell information is compared with the comprehensive load cell information after the two pieces of information are received to determine the control mode of the photovoltaic cell, the rule is triggered after the determination to perform local control, and when the local control is performed to the reference value, the local control is sent to the central control cell again at the time t+1Sending information P PV_i 。
As shown in FIG. 10, a cell flow chart of the integrated load cell is shown, the integrated load cell will not receive information, and only send information P to the central control cell and the two photovoltaic cells at time t+1 Load 。
Further, in combination with the specific description of the above embodiments, the present invention further performs corresponding simulation verification, and the results of the simulation verification further determine the functions and functions actually implemented by each embodiment of the present invention, specifically:
aiming at different modes, the invention builds a typical direct current micro-grid by utilizing MATLAB/SIMULINK software. The total capacity of the photovoltaic power generation is 25kW, and the total capacity comprises 10kW of PV1 and 15kW of PV2; the capacity of the micro gas turbine is 60kW; the total capacity of the energy storage device was 35kW, including 20kW of Battery1 and 15kW of Battery2.
(1) Scenario one: sufficient photovoltaic and energy storage full charge
In scenario one, the initial load is set to 7.2kW, and the energy storage unit is set to reach the SOC set upper charging limit due to charging. The central control cell judges by the calculating unit: the energy storage is in a dormant state; the photovoltaic unit can meet the load requirement due to sufficient illumination and is in a constant-voltage control mode; the micro gas turbine unit is in a dormant state. In this case, the initial load was increased by 25% at 0.5s, and 25% of the initial load was removed at 1 s. After load fluctuation, the voltage of the direct current bus can be stably maintained at 380V; when t=0.5 s, the direct current micro grid reaches a minimum voltage of 372V; when t=1s, the dc microgrid reaches a maximum voltage of 395V, still within the standard microgrid voltage range, and even in the event of load fluctuations, the power required by the load can be balanced with the power flow of the system.
(2) Scenario two: sufficient illumination, energy storage and charging
In scenario two, the initial load is still set to 7.2kW, and the energy storage unit is set to not reach the SOC set upper charging limit at this time. The central control cell judges by the calculating unit: the energy storage is in a charging state, and the voltage of the bus is maintained to be stable; the photovoltaic unit can meet the load demand due to sufficient illumination, and is in an MPPT control mode due to the fact that energy storage needs to be charged; the micro gas turbine unit is in a dormant state. In this case, the initial load is increased by 25% at 1.5s, the initial load is removed by 25% at 2s, and the initial load is restored at 2.5 s. According to the instruction of the central controller, the two photovoltaic units work in MPPT modes, the output power is 10kW and 15kW respectively, the gas turbine unit is in the sleep mode, and the output power is 0kW. The total power generated by the photovoltaic is larger than the power required by the load, the system has a large amount of surplus power, and the surplus power charges the fully charged energy storage battery according to the instruction of the central controller. We set the initial states of the two energy storage units to be 32% and 28%, respectively. In order to clearly see the charging effect of the stored energy, the capacity of the storage battery is properly processed, the simulation time is prolonged under the same system configuration, and the energy storage unit can be charged at different charging speeds and finally reach the SOC balance.
(3) Scenario three: insufficient illumination, energy storage and discharge
In a third scenario, the initial load is set to be 14.5kW, the energy storage unit is set to not reach the SOC set discharge lower limit at the moment, and the photovoltaic irradiance is set to be 1000W/m from the original 2 Down to 500W/m 2 (indicating that there is insufficient light at this time). The central control cell judges by the calculating unit: the energy storage is in a discharge state, and meanwhile, the voltage stability of the direct current bus is maintained; the photovoltaic unit can not meet the load requirement due to insufficient illumination and is in an MPPT control mode (at 500W/m 2 PV1 is 5kW and pv2 is 7.7kW; the micro gas turbine unit randomly increases the output. In this case, the initial load was increased by 50% at 3 s. For clarity of explanation of the effectiveness of the proposed method, we will compare the system dc bus voltage output and each unit output power under the conventional control strategy.
Under the traditional control strategy, when t=3s, the voltage drops to 358V due to the impact of the load, which is lower than the standard voltage range; under the proposed control strategy, the lowest voltage is 373V only, which is within the standard range. Under the traditional control strategy, when t=3s, the gas turbine properly increases the power of 1.2kW due to the impact of the load, but the energy storage does not reach the lower discharge limit, and the energy storage firstly fills the power gap, so that the difference 694W between the output force of the unit and the output force of the load is caused, and the depth of discharge of the energy storage is increased; under the control strategy, the gas turbine is increased to 8.9kW of power due to the coordination of the central controller, the output of the unit and the output of the load are only different by 20W, meanwhile, the stored energy is continuously discharged according to the original discharging speed, namely the service time of the reserved power of the system is prolonged, the overdischarge problem caused by the accelerated discharging speed is avoided, and the service life of the stored energy is prolonged.
(4) Scenario four: sufficient illumination, energy storage and charging
In a fourth scenario, the initial load is set to be 14.5kW, the energy storage unit is set to reach the SOC set discharge lower limit at the moment, and the photovoltaic irradiance is from 500W/m 2 And starts to move down gradually over time (indicating that there is insufficient light). The central control cell judges by the calculating unit: the energy storage is in a charging state, and meanwhile, the voltage stability of the direct current bus is maintained; the photovoltaic unit can not meet the load demand due to insufficient illumination, and is in an MPPT control mode, and the micro gas turbine unit randomly increases the output. It should be noted that since the gas turbine has some delay, the stored energy still needs to continue discharging a small portion of the electricity before the gas turbine increases the output. The system maintains the bus voltage within the standard range, with a maximum impact of 399V, despite the constantly changing photovoltaic irradiance. The maximum output power of the corresponding photovoltaic unit is also changed due to the change of irradiance, and the output power of the gas turbine unit is also changed under the instruction of the central controller, so that the corresponding unit maintains the power balance of the system. The stored energy is in a discharge state when t=0 to 2s corresponding to the power flow of the system, and charging is started from t=2 s.
(5) Scenario five: mode two-to-mode one conversion
The reason for this switching is that the charging of the energy store has reached the set upper limit and the operation of the energy store will be stopped. Meanwhile, the control mode of the photovoltaic is switched from the MPPT mode to the constant voltage mode. In this case, the initial load was still set to 7.2kW, and the irradiance was still set to 1000/m 2 . It should be noted that at the instant of conversion, the method comprisesIn the case of large current surge and power variation, the present embodiment employs a power limiting measure to suppress.
(6) Scenario six: mode three-way mode four transition
The reason for this switching is that the discharge of the stored energy has reached the set lower limit, the stored energy needs to be charged, and the control mode of the photovoltaic is still the MPPT mode. In this case, the initial load was still set to 14.5kW, and the irradiance was still set to 500/m 2 . At t=2.08, the energy storage unit SOC has reached the set lower limit 20.296 (this value is set so that simulation results can be seen in a short time), but it has not immediately transitioned to the charging mode, but has been retarded by about 0.19s. This is because there is a certain delay in the output of the gas turbine unit. Therefore, when the practical lower limit of the SOC of the energy storage unit is set, the embodiment can properly improve a margin and give out more power to the gas turbine unit for a bit more time, so that the influence of overdischarge on the energy storage life can be avoided.
In the embodiment, after simulation verification is performed by the collaborative control method based on the organization type P system, the proposed strategy ensures the consensus and coordination among all units, and effectively improves the voltage stability of the island direct current micro-grid. Meanwhile, photovoltaic power generation is utilized to the maximum extent, the energy storage unit is called at any time, the gas turbine unit is used as the strongest backup, and the system can meet the requirement of supply and demand balance.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-mentioned preferred embodiment should not be construed as limiting the invention, and the scope of the invention should be defined by the appended claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (10)
1. The island direct current micro-grid control system is characterized by comprising a central unit and a subunit, wherein the central unit is used for centralized control of all mechanisms in the subunit; the subunit comprises two photovoltaic generator sets for supplying energy loads of the micro-grid, two energy storage batteries for storing first standby capacity of the direct-current micro-grid, a micro gas turbine for storing second standby capacity of the direct-current micro-grid, and comprehensive loads for detecting load voltage and adjusting load current, and the central unit and the subunits and each mechanism of the subunits can be communicated.
2. The island direct current micro-grid control system according to claim 1, wherein the central unit comprises a communication module, a database module and an inference calculation module, wherein the communication module is used for collecting output information of each subunit and issuing control commands to each subunit; the database module is used for storing real-time state data information uploaded by each subunit; the reasoning calculation module is used for giving a setting value adjustment quantity by adopting a control algorithm according to the current acquired information and the system state and reasoning out the output of each subunit which should be adjusted and executed.
3. The island direct current micro-grid control system according to claim 1, wherein the subunit comprises a sensing module, a communication module, a database module and an execution module, wherein the sensing module is used for collecting environmental information; the communication module is used for information exchange among different components in the subunit and information transmission with the central unit; the database module is used for storing the state data of the corresponding components and the received information, processing the acquired information in a centralized way and sending a final control command to the execution module through logic reasoning; the execution module is used for converting the control command into actual output PWM.
4. The island direct current micro-grid control system of claim 1, wherein the photovoltaic generator set has two operating strategies, photovoltaic Maximum Power Point Tracking (MPPT) control and constant voltage control.
5. The island direct current micro-grid control system of claim 1 wherein the power of the micro gas turbine is adjustable.
6. The island direct current micro-grid control system of claim 1 wherein the first backup capacity of stored energy is preferentially utilized for the second backup capacity of the micro gas turbine.
7. An islanding direct current micro grid control system according to claim 1, wherein said integrated load has only a power output and no power input.
8. An island direct current micro-grid control system according to claim 4, further providing a control strategy, in particular,
first mode: when P PV ≥P load &SOC total ≥SOC max And when the micro gas turbine is dormant, the photovoltaic generator set operates under constant pressure control, and the energy storage system is dormant. The power flow of the system after steady state is: p (P) PV ＝P Load ；
Second mode: when P PV ≥P load &SOC total <SOC max And when the micro gas turbine is dormant, the photovoltaic generator set is controlled to operate by MPPT, and the energy storage system is in a charging state. The power flow of the system after steady state is: p (P) PV ＝P Load +P Battery ；
Third mode: when P PV <P load &SOC total ≥SOC min When the energy storage system is used for supplementing the power shortage firstly, then the micro gas turbine increases the output, the energy storage system continues to discharge, and the photovoltaic generator set is controlled to operate by MPPT. The power flow of the system after steady state is: p (P) PV +P MT +P Battery ＝P Load ；
Fourth mode: when P PV <P load &SOC total <SOC min When the micro gas turbine is in use, the micro gas turbine is required to complement the power shortage and also is required to charge the energy storage system; the photovoltaic generator set is controlled to operate by MPPT. The power flow of the system after steady state is: p (P) PV +P MT ＝P Load +P Battery 。
9. An islanding direct current micro grid control system according to claim 8, further providing a mode switching strategy, in particular,
first mode conversion: when SOC is total ≥SOC max The energy of the photovoltaic generator set is sufficient, the energy storage system can be fully charged, and the second mode is converted into the first mode;
second mode conversion: when SOC is total <SOC min The system is too empty and the energy storage system has reached the lower SOC limit when temporarily replenishing power, and the third mode is switched to the fourth mode.
10. An island direct current micro-grid cooperative control method, which is characterized by being applied to the island direct current micro-grid control system as claimed in any one of claims 1 to 9, and comprising the following steps:
(1) The central unit receives the real-time state information uploaded by each subunit, and the subunits interact with each other in real-time state information;
(2) The central unit calculates the power allocation amount according to the received real-time state information uploaded by each subunit, and determines a control mode;
(3) The central unit sends control instructions corresponding to the power distribution amounts of the subunits to the subunits so that the subunits can be controlled according to the control instructions;
(4) And (3) repeating the steps (1), (2) and (3) when the control instruction is ended and a new round of information interaction is triggered.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211259877.3A CN116526543A (en) | 2022-10-14 | 2022-10-14 | Island direct-current micro-grid control system and cooperative control method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211259877.3A CN116526543A (en) | 2022-10-14 | 2022-10-14 | Island direct-current micro-grid control system and cooperative control method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116526543A true CN116526543A (en) | 2023-08-01 |
Family
ID=87389154
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211259877.3A Pending CN116526543A (en) | 2022-10-14 | 2022-10-14 | Island direct-current micro-grid control system and cooperative control method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116526543A (en) |
-
2022
- 2022-10-14 CN CN202211259877.3A patent/CN116526543A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Wang et al. | Energy management system for stand-alone diesel-wind-biomass microgrid with energy storage system | |
| Pu et al. | Hierarchical energy management control for islanding DC microgrid with electric-hydrogen hybrid storage system | |
| CN104242337B (en) | The real time coordination control method of photovoltaic microgrid system | |
| CN111900721B (en) | Smart power grid frequency control method based on wind-water cooperative power generation mode | |
| CN104734195A (en) | Monitoring method of wind, photovoltaic and storage-integrated micro-grid capable of being operated in a grid-connected manner | |
| CN107370171B (en) | Large-scale energy storage optimal configuration and coordination control method in independent microgrid | |
| Lu et al. | Strategic framework of an energy management of a microgrid with a photovoltaic-based active generator | |
| CN107681700B (en) | Method for converting operation modes of alternating current-direct current hybrid micro-grid | |
| CN104734194A (en) | Wind, photovoltaic and storage-integrated micro-grid capable of being operated in a grid-connected manner | |
| Xiao et al. | Flat tie-line power scheduling control of grid-connected hybrid microgrids | |
| CN112510756A (en) | Micro-grid optical storage and charging coordinated operation method and system based on power level | |
| Patel et al. | Adaptive power management in PV/Battery integrated hybrid microgrid system | |
| Sun et al. | A Hybrid renewable DC microgrid voltage control | |
| Behera et al. | Coordinated power management of a laboratory scale wind energy assisted lvdc microgrid with hybrid energy storage system | |
| Pozo et al. | Battery energy storage system for a hybrid generation system grid connected using fuzzy controllers | |
| Luo et al. | Hierarchical cooperative control for islanded DC microgrid cluster | |
| CN112583020B (en) | Two-stage voltage control method for low-voltage distribution network | |
| Chai et al. | Coordinated power control for islanded DC microgrids based on bus-signaling and fuzzy logic control | |
| CN116526543A (en) | Island direct-current micro-grid control system and cooperative control method thereof | |
| CN113937751A (en) | Direct-current micro-grid group power coordination control method and system | |
| Chuan et al. | Decentralized Power Management of an Islanded Microgrid with AWS-based Wave Energy Converter | |
| Jha et al. | Literature review on various control strategies for hybrid photovoltaic and fuel cell power generating systems | |
| Mahrouch et al. | Primary Frequency Control for Wind/Battery Stand-Alone Microgrid | |
| Nandakumar et al. | Virtual Synchronous Generator-Based Frequency Control Strategy for Grid-Connected PV Systems | |
| CN110994655A (en) | Centralized coordination control method for distributed power supply |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |