CN112736962B - Control device and method of grid-connected photovoltaic power generation system and photovoltaic direct-driven equipment - Google Patents
Control device and method of grid-connected photovoltaic power generation system and photovoltaic direct-driven equipment Download PDFInfo
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- 238000010248 power generation Methods 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000001514 detection method Methods 0.000 claims abstract description 41
- 239000013589 supplement Substances 0.000 claims description 6
- 238000005057 refrigeration Methods 0.000 claims 2
- 238000004378 air conditioning Methods 0.000 description 40
- 238000010438 heat treatment Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 238000002955 isolation Methods 0.000 description 4
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Classifications
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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
- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention discloses a control device and method of a grid-connected photovoltaic power generation system and photovoltaic direct-drive equipment, wherein the device comprises the following components: the control unit is configured to control the switch unit to be switched on under the condition that the power grid is not powered down so as to control the photovoltaic direct-driven equipment to acquire electric energy from the power grid and the photovoltaic system; the detection unit is configured to detect bus voltage of the power grid under the condition that the power grid is powered down, and generate a power grid power-down signal under the condition that the bus voltage is lower than a set voltage; and the control unit is also configured to control the switch unit to be disconnected according to the power-down signal of the power grid so as to cut off the photovoltaic direct-drive equipment from the power grid and control the photovoltaic direct-drive equipment to acquire electric energy from the photovoltaic system. According to the scheme, the island phenomenon of the grid-connected photovoltaic power generation system is avoided when the power grid fails, and serious safety hazard caused by the island phenomenon is avoided.
Description
Technical Field
The invention belongs to the technical field of photovoltaic direct-drive equipment, and particularly relates to a control device and method of a grid-connected photovoltaic power generation system and photovoltaic direct-drive equipment (such as a photovoltaic direct-drive air conditioner), in particular to a control device of an anti-islanding photovoltaic direct-drive air conditioning system, an anti-islanding photovoltaic direct-drive air conditioning system and a control method of the anti-islanding photovoltaic direct-drive air conditioning system.
Background
Along with the rapid development of the distributed power generation technology, in order to solve the power consumption problem of the high-power electric equipment of the air conditioner, the photovoltaic direct-driven air conditioner combining the photovoltaic power generation technology with the air conditioning system provides a new thought for solving the power consumption problem of the air conditioner, and the photovoltaic direct-driven air conditioner changes the characteristics of the pure electric equipment of the original air conditioner, so that the photovoltaic direct-driven air conditioner becomes equipment integrating power generation and power consumption and has new requirements for protecting the photovoltaic direct-driven air conditioning system.
The grid-connected photovoltaic power generation system can convert direct current output by the solar cell array into alternating current with the same amplitude, same frequency and same phase as the voltage of the power grid, and realize connection with the power grid and power transmission to the power grid. When the grid is disconnected due to faults and the like, the grid-connected power generation system cannot timely detect power failure, so that a self-supplied island formed by the distributed grid-connected power generation system and surrounding local loads is formed. The occurrence of islanding is severely detrimental, such as: endangering the safety of maintenance personnel on the power transmission line of the power grid; the action program of a protection switch on the power distribution system is influenced, and a power grid protection device is impacted. Therefore, an effective anti-islanding detection device is needed in the grid-connected power generation system, and corresponding protection measures are adopted.
The foregoing is provided merely for the purpose of facilitating understanding of the technical solutions of the present invention and is not intended to represent an admission that the foregoing is prior art.
Disclosure of Invention
The invention aims to provide a control device and method of a grid-connected photovoltaic power generation system and photovoltaic direct-drive equipment, so as to solve the problem that the grid-connected photovoltaic power generation system has an island phenomenon when power failure occurs, and serious safety hazard exists, and achieve the effect of avoiding the island phenomenon when the grid-connected photovoltaic power generation system fails, and the serious safety hazard caused by the island phenomenon.
The invention provides a control device of a grid-connected photovoltaic power generation system, which comprises: the photovoltaic system and the power grid can supply power to the photovoltaic direct-drive equipment respectively; the control device of the grid-connected photovoltaic power generation system comprises: the device comprises a switch unit, a detection unit and a control unit; the switch unit is arranged between a bus of the power grid and the photovoltaic direct-drive equipment; the control unit is configured to control the switch unit to be turned on under the condition that the power grid is not powered down so as to control the photovoltaic direct-driven equipment to acquire electric energy from the power grid and the photovoltaic system; the detection unit is configured to detect bus voltage of the power grid under the condition that the power grid is powered down, and generate a power grid power-down signal under the condition that the bus voltage is lower than a set voltage; the control unit is further configured to control the switch unit to be disconnected according to the power-down signal of the power grid so as to cut off the photovoltaic direct-drive equipment from the power grid and control the photovoltaic direct-drive equipment to acquire electric energy from the photovoltaic system.
In some embodiments, the control unit, when the power grid is not powered down, controls the photovoltaic direct-driving device to obtain electric energy from the power grid and the photovoltaic system, including: under the condition that the power grid and the photovoltaic system supply power simultaneously, the photovoltaic direct-drive equipment is controlled to obtain electric energy from the photovoltaic system preferentially; and controlling the power grid to supplement electric energy to the photovoltaic direct-drive equipment under the condition that the photovoltaic electric energy provided by the photovoltaic system is lower than the lower limit of the set electric energy range; and controlling the photovoltaic system to invert redundant photovoltaic power into the power grid under the condition that the photovoltaic power provided by the photovoltaic system is higher than the upper limit of the set power range.
In some embodiments, the switching unit includes: a circuit breaker, a contactor and a knife switch; the circuit breaker, the contactor and the knife-fuse switch are arranged between a bus of the power grid and an AC/DC module of the photovoltaic direct-drive equipment.
In some embodiments, in case the switching unit comprises a contactor, the detection unit comprises a coil of the contactor, and a normally closed contact of the contactor is provided in the switching unit.
In accordance with another aspect of the present invention, there is provided a photovoltaic direct-driven apparatus comprising: the control device of the grid-connected photovoltaic power generation system.
In accordance with another aspect of the present invention, in a control method of a grid-connected photovoltaic power generation system, the grid-connected photovoltaic power generation system includes: the photovoltaic system and the power grid can supply power to the photovoltaic direct-drive equipment respectively; the control method of the grid-connected photovoltaic power generation system comprises the following steps: the control unit is used for controlling the switch unit to be turned on under the condition that the power grid is not powered down so as to control the photovoltaic direct-driven equipment to acquire electric energy from the power grid and the photovoltaic system; detecting bus voltage of the power grid through a detection unit under the condition that the power grid is powered off, and generating a power grid power-off signal under the condition that the bus voltage is lower than a set voltage; and the control unit is used for controlling the switch unit to be disconnected according to the power-down signal of the power grid so as to cut off the photovoltaic direct-drive equipment from the power grid and controlling the photovoltaic direct-drive equipment to acquire electric energy from the photovoltaic system.
In some embodiments, the controlling, by the control unit, the photovoltaic direct-driving device to obtain electric energy from the power grid and the photovoltaic system without power failure of the power grid includes: under the condition that the power grid and the photovoltaic system supply power simultaneously, the photovoltaic direct-drive equipment is controlled to obtain electric energy from the photovoltaic system preferentially; and controlling the power grid to supplement electric energy to the photovoltaic direct-drive equipment under the condition that the photovoltaic electric energy provided by the photovoltaic system is lower than the lower limit of the set electric energy range; and controlling the photovoltaic system to invert redundant photovoltaic power into the power grid under the condition that the photovoltaic power provided by the photovoltaic system is higher than the upper limit of the set power range.
In some embodiments, the switching unit includes: a circuit breaker, a contactor and a knife switch; the circuit breaker, the contactor and the knife-fuse switch are arranged between a bus of the power grid and an AC/DC module of the photovoltaic direct-drive equipment.
In some embodiments, in case the switching unit comprises a contactor, the detection unit comprises a coil of the contactor, and a normally closed contact of the contactor is provided in the switching unit.
According to the scheme, the grid-connected cabinet is used for connecting the photovoltaic direct-drive equipment with the power grid and playing a role in protection, the intelligent detection module is used for realizing anti-islanding protection of the photovoltaic direct-drive equipment, off-grid operation can be realized, and serious safety hazard caused by islanding phenomenon is avoided by avoiding the grid-connected photovoltaic power generation system when the power grid fails.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a schematic diagram of a control device of a grid-connected photovoltaic power generation system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an embodiment of an anti-islanding photovoltaic direct-drive air conditioning system when not in off-grid operation;
FIG. 3 is a schematic diagram of an embodiment of an anti-islanding photovoltaic direct-drive air conditioning system in off-grid operation;
FIG. 4 is a flow chart of an embodiment of a control method of a grid-connected photovoltaic power generation system according to the present invention;
fig. 5 is a schematic flow chart of an embodiment of controlling the photovoltaic direct-driven apparatus to obtain electric energy from the power grid and the photovoltaic system in the method of the present invention.
In the embodiment of the present invention, reference numerals are as follows, in combination with the accompanying drawings:
1-a circuit breaker; a 2-contactor; 3-knife-fuse switch; 4-alternating-current low-voltage distribution busbar.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. 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.
According to an embodiment of the invention, a control device of a grid-connected photovoltaic power generation system is provided. Referring to fig. 1, a schematic diagram of an embodiment of the apparatus of the present invention is shown. The grid-connected photovoltaic power generation system comprises: the photovoltaic system and the power grid can supply power to the photovoltaic direct-drive equipment respectively. The control device of the grid-connected photovoltaic power generation system comprises: the system comprises a switch unit (such as a grid-connected cabinet), a detection unit and a control unit. The switch unit is arranged between a bus (such as an alternating-current low-voltage power distribution bus 4) of the power grid and photovoltaic direct-drive equipment (such as a photovoltaic direct-drive air conditioner), and the grid-connected cabinet is arranged between the alternating-current low-voltage power distribution bus 4 and a first AC/DC module of the photovoltaic direct-drive air conditioner. The photovoltaic system is connected to the photovoltaic direct-drive equipment, for example, the photovoltaic system is connected between a first AC/DC module and a second AC/DC module of the photovoltaic direct-drive air conditioner.
The control unit is configured to control the switch unit to be connected under the condition that the power grid is not powered down so as to control the photovoltaic direct-driven equipment to acquire electric energy from the power grid and the photovoltaic system.
In some embodiments, the control unit, when the power grid is not powered down, controls the photovoltaic direct-driving device to obtain electric energy from the power grid and the photovoltaic system, including:
the control unit is specifically further configured to control the photovoltaic direct-drive device to obtain electric energy from the photovoltaic system preferentially under the condition that the power grid and the photovoltaic system supply power simultaneously. The method comprises the steps of,
the control unit is specifically further configured to control the power grid to supplement electric energy for the photovoltaic direct-drive device under the condition that the photovoltaic electric energy provided by the photovoltaic system is lower than the lower limit of the set electric energy range.
The control unit is specifically further configured to control the photovoltaic system to invert the surplus photovoltaic power into the power grid in case the photovoltaic power that the photovoltaic system can provide is higher than the upper limit of the set power range.
Specifically, when the utility grid (i.e. the power grid of the utility power) is powered on, the photovoltaic direct-driven air conditioner acquires electric energy from the utility grid and the photovoltaic system, the unit preferentially uses photovoltaic direct current, when the photovoltaic power is insufficient, the utility power is used for supplementing, and when the photovoltaic direct current is sufficient, the unit inverts surplus photovoltaic direct current to the utility grid.
The detection unit is configured to detect a bus voltage of the power grid under the condition that the power grid is powered down, and generate a power grid power-down signal under the condition that the bus voltage is lower than a set voltage.
The control unit is further configured to control the switch unit to be disconnected according to the power-down signal of the power grid so as to cut off the photovoltaic direct-drive equipment from the power grid and control the photovoltaic direct-drive equipment to acquire electric energy from the photovoltaic system.
For example: when the power grid is powered down, the intelligent detection module detects that the alternating-current low-voltage busbar 4 is powered down, so that signals are transmitted to the grid-connected cabinet and the photovoltaic direct-driven air conditioner, the contactor 2 in the grid-connected cabinet disconnects the photovoltaic direct-driven air conditioner from the mains supply after receiving the mains supply power down, and the photovoltaic direct-driven air conditioner is prevented from continuously supplying power to the mains supply after the mains supply power down; after receiving a mains supply power-off signal, the photovoltaic direct-driven air conditioner starts an off-grid operation mode, works according to the direct-current electric energy input condition of a photovoltaic system and the requirement condition of a user, and when the photovoltaic direct-current electric energy is excessive, the photovoltaic direct-driven air conditioner limits the direct-current electric energy input and outputs normal refrigerating (heating) quantity; when the photovoltaic direct current electric energy is insufficient, the photovoltaic direct-driven air conditioner operates with limited power, so that the refrigerating (heating) output is reduced, and the operation of the air conditioner is ensured.
Therefore, the island protection and off-grid operation of the photovoltaic direct-driven air conditioning system can be realized by utilizing the switch unit (such as a grid-connected cabinet) to connect the photovoltaic direct-driven equipment (such as a photovoltaic direct-driven air conditioner) with a power grid and play a role in protection, the urban network power failure can be accurately judged, the photovoltaic direct-driven air conditioning system is rapidly cut off from the power grid after the urban network power failure, and the photovoltaic direct-driven air conditioner is operated by utilizing the photovoltaic direct-current ionization network after the photovoltaic direct-driven air conditioning system is cut off from the power grid; the island protection problem of the photovoltaic direct-driven air conditioning system can be effectively solved, island operation of the photovoltaic direct-driven air conditioning system is prevented, and off-grid operation of the photovoltaic direct-driven air conditioning system after power failure of the commercial power is realized.
In some embodiments, the switching unit includes: a circuit breaker 1, a contactor 2 and a knife-fuse switch 3.
The circuit breaker 1, the contactor 2 and the knife-fuse switch 3 are arranged between a bus of the power grid and an AC/DC module of the photovoltaic direct-drive equipment.
The anti-islanding photovoltaic direct-drive air conditioning system comprises a photovoltaic system, a photovoltaic variable-frequency air conditioner (namely a photovoltaic direct-drive air conditioner) and a grid-connected cabinet. The photovoltaic system provides direct current for the photovoltaic direct-driven air conditioner, the electric wire netting provides alternating current for the photovoltaic direct-driven air conditioner, and when the photovoltaic system provides power for the photovoltaic direct-driven air conditioner and has surplus, the photovoltaic direct-driven air conditioner can invert unnecessary electric energy to the electric wire netting, and other loads of power supply network use, and the grid-connected cabinet is by circuit breaker 1, contactor 2 and sword fuse switch 3. The hardware is utilized to carry out effective physical isolation, so that the island effect is effectively prevented.
Therefore, the contactor 2 and the breaker 1 of the grid-connected cabinet are directly controlled, and signals are not transmitted to the processing module, so that the grid-connected cabinet is more convenient and flexible, meanwhile, lower requirements are provided for the grid-connected cabinet and a photovoltaic air conditioner (namely, a photovoltaic direct-driven air conditioner), and the adaptation is stronger.
In some embodiments, in case the switching unit comprises a contactor 2, the detection unit comprises a coil of the contactor 2, and the normally closed contact of the contactor 2 is provided in the switching unit.
Specifically, the detection unit, such as an intelligent detection module, can be directly replaced by a coil control loop of the contactor 2, so that the photovoltaic air conditioner is required to have the function of detecting the power failure of the mains supply and automatically switching off-grid operation modes. When the main circuit is disconnected, the main coil of the contactor 2 is connected in series with the detection loop, and at the moment, the corresponding normally-closed contact is disconnected, and the photovoltaic power supply is cut off to ensure that the current is not conveyed to the city network.
Through a large number of experiments, the technical scheme of the invention is adopted, the grid-connected cabinet is utilized to connect the photovoltaic direct-drive equipment with the power grid and play a role in protection, the intelligent detection module is utilized to realize the anti-islanding protection of the photovoltaic direct-drive equipment, off-grid operation can be realized, and the occurrence of islanding phenomenon of the grid-connected photovoltaic power generation system during power grid faults is avoided, so that serious safety hazard caused by the islanding phenomenon is avoided.
According to an embodiment of the present invention, there is also provided a photovoltaic direct-driving apparatus corresponding to a control device of a grid-connected photovoltaic power generation system. The photovoltaic direct-drive apparatus may include: the control device of the grid-connected photovoltaic power generation system.
In the related scheme, a software program is used for judging whether island protection is needed, and a system with simple software protection and no physical isolation still has the risk of current series flow to a power grid system.
In some embodiments, the scheme of the invention provides an anti-islanding photovoltaic direct-driven air conditioning system and a control method thereof, which are characterized in that a grid-connected cabinet is utilized to connect a photovoltaic direct-driven air conditioner with a power grid and play a role in protection, and an intelligent detection module is utilized to realize islanding protection and off-grid operation of the photovoltaic direct-driven air conditioning system, so that the islanding protection problem of the photovoltaic direct-driven air conditioning system is solved, and the photovoltaic direct-driven air conditioning system can be disconnected from the mains supply and off-grid operation after the mains supply is powered off.
According to the scheme, the power failure of the commercial network can be accurately judged, the photovoltaic direct-driven air conditioner system is rapidly cut off from the power grid after the power failure of the commercial network, and the photovoltaic direct-driven air conditioner operates by using the photovoltaic direct-current ionization network after the power failure of the commercial network; the island protection problem of the photovoltaic direct-driven air conditioning system can be effectively solved, island operation of the photovoltaic direct-driven air conditioning system is prevented, and off-grid operation of the photovoltaic direct-driven air conditioning system after power failure of the commercial power is realized.
Fig. 2 is a schematic structural diagram of an embodiment of an anti-islanding photovoltaic direct-driven air conditioning system when not in off-grid operation. As shown in fig. 2, the anti-islanding photovoltaic direct-drive air conditioning system comprises: photovoltaic system, photovoltaic direct drive air conditioner, grid-connected cabinet and intelligent detection module. The photovoltaic system is connected to a photovoltaic direct-driven air conditioner, and the photovoltaic direct-driven air conditioner is connected to the alternating-current low-voltage power distribution busbar 4 after passing through the grid-connected cabinet.
Wherein, photovoltaic directly drives air conditioner includes: a first AC/DC module (i.e., alternating current and direct current conversion module), a second AC/DC module, and a motor M. The first AC/DC module, the second AC/DC module and the motor are sequentially connected. The photovoltaic system is connected between two adjacent AC/DC modules (namely a first AC/DC module and a second AC/DC module) in the photovoltaic direct-driven air conditioner. Grid-connected cabinet includes: the circuit breaker 1, the contactor 2 and the knife switch 3 are connected to the alternating-current low-voltage distribution busbar 4 in sequence. The intelligent detection module is respectively connected to the first AC/DC module, the contactor 2 and the alternating-current low-voltage distribution busbar 4.
Compared with the related scheme, the anti-islanding photovoltaic direct-driven air conditioning system shown in fig. 2 is more convenient and flexible, brings lower requirements on the grid-connected cabinet and the photovoltaic air conditioner (namely the photovoltaic direct-driven air conditioner) through directly controlling the contactor 2 and the breaker 1 of the grid-connected cabinet instead of transmitting signals to the processing module, and is stronger in adaptation.
As shown in fig. 2, the anti-islanding photovoltaic direct-drive air conditioning system consists of a photovoltaic system, a photovoltaic variable-frequency air conditioner (namely a photovoltaic direct-drive air conditioner) and a grid-connected cabinet. The photovoltaic system provides direct current for the photovoltaic direct-driven air conditioner, the electric wire netting provides alternating current for the photovoltaic direct-driven air conditioner, and when the photovoltaic system provides power for the photovoltaic direct-driven air conditioner and has surplus, the photovoltaic direct-driven air conditioner can invert unnecessary electric energy to the electric wire netting, and other loads of power supply network use, and the grid-connected cabinet is by circuit breaker 1, contactor 2 and sword fuse switch 3. The hardware is utilized to carry out effective physical isolation, so that the island effect is effectively prevented.
When the commercial network (namely the power grid of the commercial power) is electrified, the photovoltaic direct-driven air conditioner acquires electric energy from the commercial network and the photovoltaic system, the unit preferentially uses photovoltaic direct current, when the photovoltaic power is insufficient, the commercial power is utilized for supplementing, and when the photovoltaic direct current is sufficient, the unit inverts the surplus photovoltaic direct current to the commercial network.
When the power grid is powered down, the intelligent detection module detects that the alternating-current low-voltage busbar 4 is powered down, so that signals are transmitted to the grid-connected cabinet and the photovoltaic direct-driven air conditioner, the contactor 2 in the grid-connected cabinet disconnects the photovoltaic direct-driven air conditioner from the mains supply after receiving the mains supply power down, and the photovoltaic direct-driven air conditioner is prevented from continuously supplying power to the mains supply after the mains supply power down; after receiving a mains supply power-off signal, the photovoltaic direct-driven air conditioner starts an off-grid operation mode, works according to the direct-current electric energy input condition of a photovoltaic system and the requirement condition of a user, and when the photovoltaic direct-current electric energy is excessive, the photovoltaic direct-driven air conditioner limits the direct-current electric energy input and outputs normal refrigerating (heating) quantity; when the photovoltaic direct-current electric energy is insufficient, the photovoltaic direct-driven air conditioner operates at a limited power, the refrigerating (heating) output is reduced, and the operation of the air conditioner is ensured, as shown in fig. 3.
In some embodiments, the intelligent detection module can be directly replaced by a coil control loop of the contactor 2, so that the photovoltaic air conditioner is required to have the function of detecting the power failure of the mains supply and automatically switching off-grid operation modes. When the main circuit is disconnected, the main coil of the contactor 2 is connected in series with the detection loop, and at the moment, the corresponding normally-closed contact is disconnected, and the photovoltaic power supply is cut off to ensure that the current is not conveyed to the city network.
In some embodiments, a grid-connected cabinet is configured for a large-scale photovoltaic direct-driven air conditioning device, and an island protection device is installed in the grid-connected cabinet; for the small photovoltaic direct-driven air conditioning equipment, the island protection device is directly designed into a product by taking the function into consideration when the product is designed, for example, the island protection function can be contained in the photovoltaic multi-split air conditioner, so that the redundant electric quantity is not directly transmitted to a power grid, and the photovoltaic multi-split air conditioner is completely used for the photovoltaic air conditioner.
The intelligent detection device is used for detecting the current state of the grid-connected cabinet, wherein the island protection device is installed in the grid-connected cabinet and is a controller and an actuator, and when the intelligent detection device feeds back the current state to the controller, the controller compares and analyzes the current state to obtain a conclusion and sends the conclusion to the actuator.
In some embodiments, the island protection scheme can be adopted by devices with electricity generation property, such as power plants, diesel generators and the like which are similar to devices with photovoltaic power generation function, which are not limited to photovoltaic direct-drive air conditioning devices.
Since the processing and the functions implemented by the photovoltaic direct-driven apparatus of this embodiment basically correspond to the embodiments, principles and examples of the apparatus shown in fig. 1, the description of this embodiment is not exhaustive, and reference may be made to the related descriptions in the foregoing embodiments, which are not repeated herein.
Through a large number of experiments, the technical scheme of the invention is adopted, the grid-connected cabinet is utilized to connect the photovoltaic direct-drive equipment with the power grid and play a role in protection, the intelligent detection module is utilized to realize the anti-islanding protection of the photovoltaic direct-drive equipment, off-grid operation can be realized, the problem of islanding protection of the photovoltaic direct-drive air conditioning system can be solved, and the photovoltaic direct-drive air conditioning system can be disconnected from the mains supply after the mains supply is powered off and operated off-grid.
According to an embodiment of the present invention, there is further provided a control method of a grid-connected photovoltaic power generation system corresponding to the photovoltaic direct-driven apparatus, as shown in fig. 4, which is a schematic flow chart of an embodiment of the method of the present invention. The grid-connected photovoltaic power generation system comprises: the photovoltaic system and the power grid can supply power to the photovoltaic direct-drive equipment respectively. The control method of the grid-connected photovoltaic power generation system comprises the following steps: step S110 to step S130.
At step S110, the control unit controls the switch unit to be turned on to control the photovoltaic direct-driving device to obtain electric energy from the power grid and the photovoltaic system when the power grid is not powered down.
In some embodiments, in step S110, the control unit controls the photovoltaic direct-driving device to obtain electric energy from the power grid and the photovoltaic system in a case that the power grid is not powered down, which is described in the following exemplary description.
An embodiment of the method of the present invention for controlling the photovoltaic direct-driving device to obtain electric energy from the power grid and the photovoltaic system according to fig. 5 is a schematic flow chart, which further describes a specific process for controlling the photovoltaic direct-driving device to obtain electric energy from the power grid and the photovoltaic system in step S110, including: step S210 to step S230.
Step S210, controlling the photovoltaic direct-driving device to obtain electric energy from the photovoltaic system preferentially under the condition that the power grid and the photovoltaic system supply power simultaneously. The method comprises the steps of,
and step S220, controlling the power grid to supplement electric energy for the photovoltaic direct-drive equipment under the condition that the photovoltaic electric energy provided by the photovoltaic system is lower than the lower limit of the set electric energy range.
And step S230, controlling the photovoltaic system to invert redundant photovoltaic power into the power grid under the condition that the photovoltaic power provided by the photovoltaic system is higher than the upper limit of the set power range.
Specifically, when the utility grid (i.e. the power grid of the utility power) is powered on, the photovoltaic direct-driven air conditioner acquires electric energy from the utility grid and the photovoltaic system, the unit preferentially uses photovoltaic direct current, when the photovoltaic power is insufficient, the utility power is used for supplementing, and when the photovoltaic direct current is sufficient, the unit inverts surplus photovoltaic direct current to the utility grid.
At step S120, a detection unit detects a bus voltage of the power grid in case of power failure of the power grid, and generates a power-down signal of the power grid in case that the bus voltage is lower than a set voltage.
At step S130, the control unit controls the switch unit to be turned off according to the power-down signal of the power grid, so as to cut off the photovoltaic direct-drive device from the power grid, and controls the photovoltaic direct-drive device to obtain electric energy from the photovoltaic system.
The switch unit (such as a grid-connected cabinet) is arranged between a bus (such as an alternating-current low-voltage power distribution bus 4) of the power grid and photovoltaic direct-drive equipment (such as a photovoltaic direct-drive air conditioner), and the grid-connected cabinet is arranged between the alternating-current low-voltage power distribution bus 4 and a first AC/DC module of the photovoltaic direct-drive air conditioner; the photovoltaic system is connected to the photovoltaic direct-drive equipment, for example, the photovoltaic system is connected between a first AC/DC module and a second AC/DC module of the photovoltaic direct-drive air conditioner.
For example: when the power grid is powered down, the intelligent detection module detects that the alternating-current low-voltage busbar 4 is powered down, so that signals are transmitted to the grid-connected cabinet and the photovoltaic direct-driven air conditioner, the contactor 2 in the grid-connected cabinet disconnects the photovoltaic direct-driven air conditioner from the mains supply after receiving the mains supply power down, and the photovoltaic direct-driven air conditioner is prevented from continuously supplying power to the mains supply after the mains supply power down; after receiving a mains supply power-off signal, the photovoltaic direct-driven air conditioner starts an off-grid operation mode, works according to the direct-current electric energy input condition of a photovoltaic system and the requirement condition of a user, and when the photovoltaic direct-current electric energy is excessive, the photovoltaic direct-driven air conditioner limits the direct-current electric energy input and outputs normal refrigerating (heating) quantity; when the photovoltaic direct current electric energy is insufficient, the photovoltaic direct-driven air conditioner operates with limited power, so that the refrigerating (heating) output is reduced, and the operation of the air conditioner is ensured.
Therefore, the island protection and off-grid operation of the photovoltaic direct-driven air conditioning system can be realized by utilizing the switch unit (such as a grid-connected cabinet) to connect the photovoltaic direct-driven equipment (such as a photovoltaic direct-driven air conditioner) with a power grid and play a role in protection, the urban network power failure can be accurately judged, the photovoltaic direct-driven air conditioning system is rapidly cut off from the power grid after the urban network power failure, and the photovoltaic direct-driven air conditioner is operated by utilizing the photovoltaic direct-current ionization network after the photovoltaic direct-driven air conditioning system is cut off from the power grid; the island protection problem of the photovoltaic direct-driven air conditioning system can be effectively solved, island operation of the photovoltaic direct-driven air conditioning system is prevented, and off-grid operation of the photovoltaic direct-driven air conditioning system after power failure of the commercial power is realized.
In some embodiments, the switching unit includes: a circuit breaker 1, a contactor 2 and a knife-fuse switch 3.
The circuit breaker 1, the contactor 2 and the knife-fuse switch 3 are arranged between a bus of the power grid and an AC/DC module of the photovoltaic direct-drive equipment.
The anti-islanding photovoltaic direct-drive air conditioning system comprises a photovoltaic system, a photovoltaic variable-frequency air conditioner (namely a photovoltaic direct-drive air conditioner) and a grid-connected cabinet. The photovoltaic system provides direct current for the photovoltaic direct-driven air conditioner, the electric wire netting provides alternating current for the photovoltaic direct-driven air conditioner, and when the photovoltaic system provides power for the photovoltaic direct-driven air conditioner and has surplus, the photovoltaic direct-driven air conditioner can invert unnecessary electric energy to the electric wire netting, and other loads of power supply network use, and the grid-connected cabinet is by circuit breaker 1, contactor 2 and sword fuse switch 3. The hardware is utilized to carry out effective physical isolation, so that the island effect is effectively prevented.
Therefore, the contactor 2 and the breaker 1 of the grid-connected cabinet are directly controlled, and signals are not transmitted to the processing module, so that the grid-connected cabinet is more convenient and flexible, meanwhile, lower requirements are provided for the grid-connected cabinet and a photovoltaic air conditioner (namely, a photovoltaic direct-driven air conditioner), and the adaptation is stronger.
In some embodiments, in case the switching unit comprises a contactor 2, the detection unit comprises a coil of the contactor 2, and the normally closed contact of the contactor 2 is provided in the switching unit.
Specifically, the detection unit, such as an intelligent detection module, can be directly replaced by a coil control loop of the contactor 2, so that the photovoltaic air conditioner is required to have the function of detecting the power failure of the mains supply and automatically switching off-grid operation modes. When the main circuit is disconnected, the main coil of the contactor 2 is connected in series with the detection loop, and at the moment, the corresponding normally-closed contact is disconnected, and the photovoltaic power supply is cut off to ensure that the current is not conveyed to the city network.
Since the processing and the functions implemented by the method of the present embodiment basically correspond to the embodiments, principles and examples of the foregoing photovoltaic direct-driven apparatus, the descriptions of the present embodiment are not exhaustive, and reference may be made to the related descriptions of the foregoing embodiments, which are not repeated herein.
Through a large number of experimental verification, adopt the technical scheme of this embodiment, through utilizing the grid-connected cabinet to connect photovoltaic direct-drive equipment and electric wire netting and play the guard action, utilize intelligent detection module to realize the anti-islanding protection of photovoltaic direct-drive equipment to can realize off-grid operation, can effectively solve photovoltaic direct-drive air conditioning system islanding protection problem, prevent photovoltaic direct-drive air conditioning system islanding operation, realize that photovoltaic direct-drive air conditioning system breaks off with the commercial power after the commercial power falls, off-grid operation.
In summary, it is readily understood by those skilled in the art that the above-described advantageous ways can be freely combined and superimposed without conflict.
The above description is only an example of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (7)
1. A control device for a grid-connected photovoltaic power generation system, the control device comprising: the photovoltaic system and the power grid can supply power to the photovoltaic direct-drive equipment respectively; the control device of the grid-connected photovoltaic power generation system comprises: the device comprises a switch unit, a detection unit and a control unit; the switch unit is arranged between a bus of the power grid and the photovoltaic direct-drive equipment; wherein,
the control unit is configured to control the switch unit to be turned on under the condition that the power grid is not powered down so as to control the photovoltaic direct-drive equipment to acquire electric energy from the power grid and the photovoltaic system;
the detection unit is configured to detect bus voltage of the power grid under the condition that the power grid is powered down, and generate a power grid power-down signal under the condition that the bus voltage is lower than a set voltage;
the control unit is further configured to control the switch unit to be disconnected according to the power-down signal of the power grid so as to cut off the photovoltaic direct-drive equipment from the power grid and control the photovoltaic direct-drive equipment to acquire electric energy from the photovoltaic system;
the control unit is used for controlling the photovoltaic direct-driven equipment to acquire electric energy from the power grid and the photovoltaic system under the condition that the power grid is not powered down, and comprises the following steps: under the condition that the power grid and the photovoltaic system supply power simultaneously, the photovoltaic direct-drive equipment is controlled to obtain electric energy from the photovoltaic system preferentially; and controlling the power grid to supplement electric energy for the photovoltaic direct-drive equipment under the condition that the photovoltaic electric energy provided by the photovoltaic system is lower than the lower limit of the set electric energy range; under the condition that the photovoltaic power provided by the photovoltaic system is higher than the upper limit of the set power range, controlling the photovoltaic system to invert redundant photovoltaic power into the power grid;
when the power grid is powered down, the intelligent detection module detects that the alternating-current low-voltage busbar is powered down, so that signals are transmitted to the grid-connected cabinet and the photovoltaic direct-driven air conditioner, and a contactor in the grid-connected cabinet disconnects the photovoltaic direct-driven air conditioner from the mains supply after receiving the mains supply power down, so that the photovoltaic direct-driven air conditioner is prevented from continuously supplying power to the mains supply after the mains supply power down; after receiving a mains supply power-off signal, the photovoltaic direct-driven air conditioner starts an off-grid operation mode, works according to the direct-current electric energy input condition of a photovoltaic system and the requirement condition of a user, and when the photovoltaic direct-current electric energy is excessive, the photovoltaic direct-driven air conditioner limits the direct-current electric energy input and outputs normal refrigeration or heat; when the photovoltaic direct-current electric energy is insufficient, the photovoltaic direct-driven air conditioner operates at a limited power, so that the refrigerating or heat output is reduced, and the operation of the air conditioner is ensured; the intelligent detection module is used for realizing island protection of the photovoltaic direct-drive equipment and off-grid operation.
2. The control device of a grid-connected photovoltaic power generation system according to claim 1, wherein the switching unit includes: a circuit breaker (1), a contactor (2) and a fuse switch (3); wherein,
the circuit breaker (1), the contactor (2) and the knife-fuse switch (3) are arranged between a bus of the power grid and an AC/DC module of the photovoltaic direct-drive equipment.
3. The control device of a grid-connected photovoltaic power generation system according to claim 2, characterized in that, in the case where the switching unit includes a contactor (2), the detection unit includes a coil of the contactor (2), and a normally closed contact of the contactor (2) is provided in the switching unit.
4. A photovoltaic direct drive apparatus, comprising: the control device for a grid-connected photovoltaic power generation system according to any one of claims 1 to 3.
5. The control method of the grid-connected photovoltaic power generation system is characterized by comprising the following steps of: the photovoltaic system and the power grid can supply power to the photovoltaic direct-drive equipment respectively; the control method of the grid-connected photovoltaic power generation system comprises the following steps:
the control unit is used for controlling the switch unit to be switched on under the condition that the power grid is not powered down so as to control the photovoltaic direct-driven equipment to acquire electric energy from the power grid and the photovoltaic system;
detecting bus voltage of the power grid through a detection unit under the condition that the power grid is powered off, and generating a power grid power-off signal under the condition that the bus voltage is lower than a set voltage;
the control unit is used for controlling the switch unit to be disconnected according to the power-down signal of the power grid so as to cut off the photovoltaic direct-drive equipment from the power grid and controlling the photovoltaic direct-drive equipment to acquire electric energy from the photovoltaic system;
through the control unit, under the condition that the power grid is not powered down, the photovoltaic direct-drive equipment is controlled to acquire electric energy from the power grid and the photovoltaic system, and the method comprises the following steps: under the condition that the power grid and the photovoltaic system supply power simultaneously, the photovoltaic direct-drive equipment is controlled to obtain electric energy from the photovoltaic system preferentially; and controlling the power grid to supplement electric energy for the photovoltaic direct-drive equipment under the condition that the photovoltaic electric energy provided by the photovoltaic system is lower than the lower limit of the set electric energy range; under the condition that the photovoltaic power provided by the photovoltaic system is higher than the upper limit of the set power range, controlling the photovoltaic system to invert redundant photovoltaic power into the power grid;
when the power grid is powered down, the intelligent detection module detects that the alternating-current low-voltage busbar is powered down, so that signals are transmitted to the grid-connected cabinet and the photovoltaic direct-driven air conditioner, and a contactor in the grid-connected cabinet disconnects the photovoltaic direct-driven air conditioner from the mains supply after receiving the mains supply power down, so that the photovoltaic direct-driven air conditioner is prevented from continuously supplying power to the mains supply after the mains supply power down; after receiving a mains supply power-off signal, the photovoltaic direct-driven air conditioner starts an off-grid operation mode, works according to the direct-current electric energy input condition of a photovoltaic system and the requirement condition of a user, and when the photovoltaic direct-current electric energy is excessive, the photovoltaic direct-driven air conditioner limits the direct-current electric energy input and outputs normal refrigeration or heat; when the photovoltaic direct-current electric energy is insufficient, the photovoltaic direct-driven air conditioner operates at a limited power, so that the refrigerating or heat output is reduced, and the operation of the air conditioner is ensured; the intelligent detection module is used for realizing island protection of the photovoltaic direct-drive equipment and off-grid operation.
6. The control method of a grid-connected photovoltaic power generation system according to claim 5, wherein the switching unit includes: a circuit breaker (1), a contactor (2) and a fuse switch (3); wherein,
the circuit breaker (1), the contactor (2) and the knife-fuse switch (3) are arranged between a bus of the power grid and an AC/DC module of the photovoltaic direct-drive equipment.
7. The control method of a grid-connected photovoltaic power generation system according to claim 6, wherein in the case where the switching unit includes a contactor (2), the detection unit includes a coil of the contactor (2), and a normally closed contact of the contactor (2) is provided in the switching unit.
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