CN112994100B - Multi-mode control photovoltaic grid-connected inverter based on intelligent distribution transformer terminal - Google Patents

Multi-mode control photovoltaic grid-connected inverter based on intelligent distribution transformer terminal Download PDF

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Publication number
CN112994100B
CN112994100B CN202110253280.7A CN202110253280A CN112994100B CN 112994100 B CN112994100 B CN 112994100B CN 202110253280 A CN202110253280 A CN 202110253280A CN 112994100 B CN112994100 B CN 112994100B
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photovoltaic
capacitor
pin
inverter
resistor
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CN112994100A (en
Inventor
李练兵
刘艳杰
范辉
梁纪峰
李佳祺
李东颖
周文
李铁成
罗蓬
冯慧波
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Electric Power Research Institute of State Grid Hebei Electric Power Co Ltd
Hebei University of Technology
State Grid Hebei Electric Power Co Ltd
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Electric Power Research Institute of State Grid Hebei Electric Power Co Ltd
Hebei University of Technology
State Grid Hebei Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • 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
    • H02J13/00002—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 monitoring
    • 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
    • H02J13/00006—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 information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
    • H02J13/00016—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 information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using a wired telecommunication network or a data transmission bus
    • 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
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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
    • 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
    • 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
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/70—Smart grids as climate change mitigation technology in the energy generation sector
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • 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
    • Y02E70/00—Other energy conversion or management systems reducing GHG emissions
    • Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/12—Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation
    • Y04S10/123—Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation the energy generation units being or involving renewable energy sources
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/14—Energy storage units
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/22—Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
    • Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
    • Y04S40/124—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using wired telecommunication networks or data transmission busses

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Inverter Devices (AREA)

Abstract

The invention relates to a multi-mode control photovoltaic grid-connected inverter based on an intelligent distribution transformer terminal. The inverter comprises an intelligent distribution transformer terminal unit, an extended power signal detection module, a photovoltaic inverter, a photovoltaic cell and a capacitor cell; the connection relation is as follows: the intelligent distribution transformer terminal unit is connected with the extended power signal detection module, the extended power signal detection module is connected with the photovoltaic inverter, and the input side of the photovoltaic inverter is connected with the photovoltaic cell and the capacitor cell. The invention can solve the problem of insufficient energy efficiency ratio of the existing equipment or method, realize the multi-functional mode conversion of the photovoltaic inverter, effectively solve the problem of line loss, obviously increase the energy efficiency ratio of the power grid and improve the active support of the system.

Description

Multi-mode control photovoltaic grid-connected inverter based on intelligent distribution transformer terminal
Technical Field
The invention belongs to the technical field of electrical control, and particularly relates to a multi-mode control photovoltaic grid-connected inverter based on an intelligent distribution transformer terminal, belonging to the field of intelligent distribution transformer.
Background
In recent years, photovoltaic power generation technology is rapidly developed, photovoltaic power generation is accepted by more and more people, and the electric energy quality of a public connection point is deteriorated due to the characteristics of more and more power electronic equipment used by a user side, nonlinearity, unbalance, reactive power and the like of local loads. A large amount of harmonic waves are injected into the power grid, so that the interference of the power grid is increased, and the power factor is reduced.
The common photovoltaic grid-connected inverter has single function, and an additional filter device and a reactive compensation device are added on the power grid side, if a device with a specific function is installed for treatment, the stacking of a plurality of devices can be caused. In the prior art, the power quality of the power grid side is detected by a collecting circuit of the inverter, and is transmitted to the grid-connected inverter and then calculated and controlled by the grid-connected inverter. However, some configuration components are added to maintain the stability of the input side voltage of the grid-connected inverter.
Li Zhengming and the like (1000-100X (2016) 09-0030-05), and adopts a large power grid, a grid-connected inverter and various loads. The acquisition circuit of the grid-connected inverter is connected on a large power grid in a bridging way, the output side of the grid-connected inverter is connected on a load, and the load is connected on the power grid through a power line. The generalized instantaneous reactive power current detection method is comprehensively utilized, the forward and reverse synchronous rotation coordinate system transformation is utilized, the current negative sequence and fundamental wave reactive components are effectively detected, and meanwhile, harmonic suppression and reactive compensation are carried out. However, when the grid-connected inverter is connected with the external expansion assembly or a plurality of inverters are connected in parallel, the redundancy of connecting wires can increase the complexity of control when the grid-connected inverter collects grid-connected point information by utilizing the collecting circuit of the inverter. The simultaneous implementation of the filtering and reactive compensation functions with one control strategy may result in an incomplete functioning of a certain function.
In order to solve the situation, we propose a multi-mode control photovoltaic grid-connected inverter based on an intelligent distribution transformer terminal.
Disclosure of Invention
The invention aims at solving the defects of the prior art and provides a multi-mode control photovoltaic grid-connected inverter system based on an intelligent distribution transformer terminal. As shown in fig. 1, an extended power signal detection module is added at the PCC point, where the extended power signal detection module is connected to the intelligent power distribution terminal unit, the photovoltaic inverter, and the PCC point respectively. The extended power signal detection module acquires voltage and current information of a grid-connected point and state information of an inverter, transmits the information to an intelligent distribution Transformer Terminal Unit (TTU) and sends a control instruction to adjust the working mode of the inverter through different control strategies. And a capacitor battery is added at the input side of the photovoltaic inverter to be connected with the photovoltaic inverter.
The invention solves the existing problems by adopting the following technical scheme:
the photovoltaic grid-connected inverter system based on the multi-mode control of the intelligent distribution transformer terminal comprises an intelligent distribution transformer terminal unit, an extended power signal detection module, a photovoltaic inverter, a photovoltaic cell and a capacitor cell; the connection relation is as follows: the intelligent distribution transformer terminal unit is connected with the extended power signal detection module, the extended power signal detection module is connected with the photovoltaic inverter, and the input side of the photovoltaic inverter is connected with the photovoltaic cell and the capacitor cell;
the extended power signal detection module comprises a microprocessor, a signal acquisition circuit, a carrier communication interface and an RS485 communication interface; the microprocessor is respectively connected with the signal acquisition circuit, the carrier communication and the RS485 communication; the signal acquisition circuit is connected with the power distribution network PCC, and RS485 communication is connected with the photovoltaic inverter;
the signal acquisition circuit includes: the input IN is connected with one end of a resistor R2, the other end of the resistor R2 is connected with a 3 pin of an operational amplifier U1A, a capacitor C is connected IN parallel with a resistor R7, one end of the capacitor C is also connected with the 3 pin of the operational amplifier U1A, and the other ends of the capacitor C and the resistor R7 are grounded; the 2 pin of the operational amplifier U1A is connected with the 1 pin of the chip U1A; the 8 pins of the operational amplifier U1A are respectively connected with a-5V power supply and a capacitor C1, and the other end of the capacitor C1 is grounded; the 4 pin of the operational amplifier U1A is respectively connected with a +5V power supply and a capacitor C5, and the other end of the capacitor C5 is grounded; the 1 pin of the operational amplifier U1A is connected with one end of a resistor R1; the other end of the resistor R1 is respectively connected with the 6 pin of the operational amplifier U1B, the capacitor C2 and the 3 pin of the linear optocoupler; the 5 pin of the operational amplifier U1B is grounded; the pin 7 of the operational amplifier U1B is respectively connected with the other end of the capacitor C2 and one end of the resistor R3; the 1 pin of the linear optocoupler is connected with the other end of the resistor R3, and the 2 pin of the linear optocoupler is connected with a +12V_SO power supply; the 4 pins of the linear optocoupler are grounded; the 6 pins of the linear optocoupler are respectively connected with the 6 pins of the operational amplifier U3B and the end of the resistor R4; the 5 pins of the linear optocoupler are respectively connected with the 5 pins of the operational amplifier U3B and the ground wire; the 4 pin of the operational amplifier U3B is respectively connected with a +5V power supply and one end of a capacitor C7, and the other end of the capacitor C7 is connected with a signal ground wire; the pin 7 of the operational amplifier U3B is respectively connected with one end of a resistor R9 and the other end of a resistor R4; the 8 pin of the operational amplifier U3B is respectively connected with a +4V power supply and a capacitor C3, and the other end of the capacitor C3 is connected with a signal ground wire; the 3 pin of the operational amplifier U3A is connected with the other end of the resistor R9; the pin 2 of the operational amplifier U3A is respectively connected with a resistor R5 and a resistor R6; the other end of the resistor R5 is connected with a signal ground wire; the 1 pin of the operational amplifier U3A is connected with the other end of the resistor R6; the 1 pin of the operational amplifier U3A is also connected with one end of a resistor R8, the other end of the resistor R8 is respectively connected with the output OUT and one end of a capacitor C6, and the other end of the capacitor C6 is connected with a signal ground wire. The input IN is a signal from the place to be collected, i.e. at the grid connection point. Pin OUT is connected to the ad sampling port of stm32F103.
In the photovoltaic inverter, an inversion unit is connected with a power grid through an LCL filter; the inversion unit is also connected with the control unit; the power grid voltage and current sampling circuit of the control unit is directly connected with the power grid, and the middle direct current voltage sampling circuit is connected with the power grid through a user;
the control unit of the photovoltaic inverter comprises an intermediate direct-current voltage sampling circuit, a power grid voltage sampling circuit, an inverter output voltage and current sampling circuit, a microprocessor, a communication module, a control signal and an IGBT main circuit; the middle direct-current voltage sampling circuit, the power grid voltage sampling circuit and the inverter output voltage and current sampling circuit are respectively connected with the microprocessor; the communication module and the control signal are respectively connected with the microprocessor to realize mutual control; the output of the microprocessor is connected with the IGBT main circuit.
The microprocessor in the control unit of the photovoltaic inverter is specifically ARM GD32F407.
The input side of the photovoltaic inverter is additionally provided with a capacitor battery which is connected with the photovoltaic inverter. The input side comprises a photovoltaic array, an MPPT module, a Boost module and a super-capacitor battery composite energy storage module, wherein the super-capacitor battery composite energy storage comprises a capacitor battery and a photovoltaic cell. The connection relation is as follows: the photovoltaic array is connected with the MPPT module, the MPPT module is connected with the Boost module to Boost voltage, then the MPPT module is connected with the super capacitor battery composite energy storage module, and finally the MPPT module is connected to the photovoltaic inverter.
The microprocessor in the extended power signal detection module is specifically ARM stm32F103.
The signal acquisition circuit uses a linear optocoupler HCNR200-000E.
The model numbers of the operational amplifiers U1A and 3A and the operational amplifiers U1B and 3B are LM2904.
The beneficial effects of the invention are as follows:
the invention adds the extended power signal detection module, which is respectively connected with the intelligent distribution transformer terminal unit and the photovoltaic inverter, and the convenience and the rapidity of detection can be increased by utilizing the power line carrier communication and the RS485 communication; the capacitor battery composite energy storage device is added on the input side of the inverter, and the photovoltaic inverter is respectively connected with the photovoltaic battery and the capacitor battery to provide stable voltage for the photovoltaic inverter, so that reactive power and impact load can be regulated, and active frequency support can be realized. Compared with simulation test, the harmonic content of the current at the side of the power grid after compensation is greatly reduced, the total harmonic distortion rate is obviously reduced, the current is smooth, and the total current distortion rate is about 1.6%. The voltage shows a stable state after reactive compensation, the voltage and the current are in the same phase, and the voltage distortion rate is greatly reduced from about 25% to about 1.5%. The method solves the problem of insufficient energy efficiency ratio of the existing equipment or method, realizes the multifunctional mode conversion of the photovoltaic inverter, effectively solves the problem of line loss, obviously increases the energy efficiency ratio of the power grid and improves the active supportability of the system. The electricity utilization quality of the user side is effectively guaranteed, the social benefit is remarkable, and the future development prospect is wide.
Drawings
FIG. 1 is a block diagram illustrating a system connection according to the present invention;
FIG. 2 is a block diagram illustrating the components of an extended power signal detection module according to the present invention;
FIG. 3 is a signal acquisition circuit in an extended power signal detection module;
FIG. 4 is a schematic diagram of a system according to the present invention;
FIG. 5 shows i according to the invention p -i q A structural block diagram of a reactive current detection method;
FIG. 6 is a block diagram of an FFT algorithm for harmonic compensation according to the invention;
fig. 7 is a block diagram showing the output side of the photovoltaic inverter according to the present invention;
fig. 8 is a block diagram showing the constitution of a photovoltaic inverter control unit according to the present invention;
fig. 9 shows a topology of the input side of a photovoltaic inverter according to the invention;
FIG. 10 is a grid side pre-harmonic compensation current waveform;
FIG. 11 is a waveform of the current after grid side harmonic compensation;
FIG. 12 is a current-voltage waveform before grid-side reactive compensation;
FIG. 13 is a current-voltage waveform after grid-side reactive compensation;
fig. 14 shows the voltage distortion after reactive compensation.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
A further description of embodiments of the present invention will now be provided with reference to the accompanying drawings, which show a general flow diagram of a system according to the present invention,
a multi-mode control photovoltaic grid-connected inverter based on an intelligent distribution transformer terminal comprises an intelligent distribution transformer terminal unit, an extended power signal detection module, a photovoltaic inverter, a photovoltaic cell and a capacitor cell; the connection relation is as follows: the intelligent distribution transformer terminal unit is connected with the extended power signal detection module, the extended power signal detection module is connected with the photovoltaic inverter, and the input side of the photovoltaic inverter is connected with the photovoltaic cell and the capacitor cell.
As shown in fig. 2, the extended power signal detection module comprises a microprocessor, a signal acquisition circuit, a carrier communication interface and an RS485 communication interface; the microprocessor is respectively connected with the signal acquisition circuit, the carrier communication and the RS485 communication; the signal acquisition circuit is connected with the power distribution network PCC, and RS485 communication is connected with the photovoltaic inverter.
The microprocessor is connected with the signal acquisition circuit to receive information and is respectively connected with the carrier communication interface and the RS485 communication interface to realize information transmission.
The microprocessor is specifically ARM stm32F103.
The signal acquisition circuit is shown in fig. 3. The signal acquisition circuit uses a linear optocoupler HCNR200-000E, a pin IN is connected to a grid-connected point to acquire signals, and then the signals pass through the front two operational amplifier circuits to form a voltage follower circuit with a filtering function, the rear two operational amplifier circuits perform filtering and follow, and then a pin OUT is connected to an ad sampling port of stm32F 103; the RS485 communication interface is connected to two ports of a user 1 and a user 2 of the microprocessor; the carrier communication interface is connected to the user 4 port of the microprocessor.
The method comprises the following steps: the input IN is connected with one end of a resistor R2, the other end of the resistor R2 is connected with a 3 pin of an operational amplifier U1A, a capacitor C is connected IN parallel with a resistor R7, one end of the capacitor C is also connected with the 3 pin of the operational amplifier U1A, and the other ends of the capacitor C and the resistor R7 are grounded; the 2 pin of the operational amplifier U1A is connected with the 1 pin of the chip U1A; the 8 pins of the operational amplifier U1A are respectively connected with a-5V power supply and a capacitor C1, and the other end of the capacitor C1 is grounded; the 4 pin of the operational amplifier U1A is respectively connected with a +5V power supply and a capacitor C5, and the other end of the capacitor C5 is grounded; the 1 pin of the operational amplifier U1A is connected with one end of a resistor R1; the other end of the resistor R1 is respectively connected with the 6 pin of the operational amplifier U1B, the capacitor C2 and the 3 pin of the linear optocoupler; the 5 pin of the operational amplifier U1B is grounded; the pin 7 of the operational amplifier U1B is respectively connected with the other end of the capacitor C2 and one end of the resistor R3; the 1 pin of the linear optocoupler is connected with the other end of the resistor R3, and the 2 pin of the linear optocoupler is connected with a +12V_SO power supply; the 4 pins of the linear optocoupler are grounded; the 6 pins of the linear optocoupler are respectively connected with the 6 pins of the operational amplifier U3B and the end of the resistor R4; the 5 pins of the linear optocoupler are respectively connected with the 5 pins of the operational amplifier U3B and the ground wire; the 4 pin of the operational amplifier U3B is respectively connected with a +5V power supply and one end of a capacitor C7, and the other end of the capacitor C7 is connected with a signal ground wire; the pin 7 of the operational amplifier U3B is respectively connected with one end of a resistor R9 and the other end of a resistor R4; the 8 pin of the operational amplifier U3B is respectively connected with a +4V power supply and a capacitor C3, and the other end of the capacitor C3 is connected with a signal ground wire; the 3 pin of the operational amplifier U3A is connected with the other end of the resistor R9; the pin 2 of the operational amplifier U3A is respectively connected with a resistor R5 and a resistor R6; the other end of the resistor R5 is connected with a signal ground wire; the 1 pin of the operational amplifier U3A is connected with the other end of the resistor R6; the 1 pin of the operational amplifier U3A is also connected with one end of a resistor R8, the other end of the resistor R8 is respectively connected with the output OUT and one end of a capacitor C6, and the other end of the capacitor C6 is connected with a signal ground wire. The input IN is a signal from the place to be collected, i.e. at the grid connection point. Pin OUT is connected to the ad sampling port of stm32F103.
The model numbers of the operational amplifiers U1A and 3A and the operational amplifiers U1B and 3B are LM2904;
the intelligent distribution transformer terminal is a device based on the intelligent distribution transformer terminal and is used for calculating the voltage, the current distortion rate, the power factor and the residual capacity of the photovoltaic inverter of the grid-connected point according to the three-phase voltage and current information acquired by the extended power signal detection module, the intelligent distribution transformer terminal unit calculates reactive power and harmonic compensation control quantity, the working mode of the photovoltaic inverter is adjusted, and reactive compensation and harmonic suppression are carried out on the public connection point.
The current photovoltaic inverter is originally only connected with the photovoltaic cell, and the capacitor cell is additionally connected with the current photovoltaic inverter on the basis of the current photovoltaic inverter, and the photovoltaic cell is connected with the capacitor cell in a parallel connection mode.
Fig. 7 is a working schematic diagram of a photovoltaic inverter, namely a structure diagram of an output side of the photovoltaic inverter, and the inverter unit is connected with a power grid through an LCL filter; the inversion unit is also connected with the control unit; the power grid voltage and current sampling circuit of the control unit is directly connected with the power grid, and the middle direct current voltage sampling circuit is connected with the power grid through a user;
fig. 8 is a control unit of the photovoltaic inverter, which includes an intermediate dc voltage sampling circuit, a grid voltage sampling circuit, an inverter output voltage current sampling circuit, a microprocessor, a communication module, a control signal, and an IGBT main circuit. The microprocessor is specifically ARM GD32F407. The middle direct-current voltage sampling circuit, the power grid voltage sampling circuit and the inverter output voltage and current sampling circuit are respectively connected with the microprocessor. The communication module and the control signal are respectively connected with the microprocessor to realize mutual control. The output of the microprocessor is connected with the IGBT main circuit.
Further, the communication module is in communication connection with the RS485 of the extended power signal detection module, and the control signal is connected with the intelligent distribution transformer terminal unit. According to the control quantity fed back by the intelligent distribution transformer terminal unit, the microprocessor calculates the control quantity through a certain algorithm to control the output of the IGBT main circuit so as to realize the harmonic suppression and reactive compensation functions.
As shown in fig. 9, the input side of the photovoltaic inverter of the present invention has a capacitive cell added to it. The input side comprises a photovoltaic array, an MPPT module, a Boost module and a super-capacitor battery composite energy storage module, wherein the super-capacitor battery composite energy storage comprises a capacitor battery and a photovoltaic cell. The connection relation is as follows: the photovoltaic array is connected with the MPPT module, the MPPT module is connected with the Boost module to Boost voltage, then the MPPT module is connected with the super capacitor battery composite energy storage module, and finally the MPPT module is connected to the photovoltaic inverter.
The carrier communication and the RS485 communication of the extended power signal detection module are respectively connected with the communication modules of the intelligent distribution transformer terminal unit and the photovoltaic inverter, and the signal acquisition circuit of the extended power signal detection module is respectively connected to the grid-connected point and the communication module of the photovoltaic inverter.
The extended power signal detection module collects information, the information is transmitted to the intelligent distribution Transformer Terminal Unit (TTU) by using a power line carrier communication mode, the TTU can also access a state-down instruction of the photovoltaic inverter through the power line carrier communication and an RS485 interface, and the photovoltaic inverter changes a working mode; and the input side of the photovoltaic inverter is additionally provided with a capacitor-battery composite energy storage device, so that the photovoltaic inverter has the functions of reactive power and impact load adjustment and active frequency support. And the self algorithm strategy is set, and the functions of harmonic suppression, reactive compensation and the like are realized through the set control strategy to adjust the power quality of the grid-connected point.
The functions of each part are as follows:
the intelligent distribution transformer terminal unit is connected with the photovoltaic grid-connected inverter controlled in a multi-mode manner, receives the collected voltage and current information of a grid-connected Point (PCC) and sends out information for controlling the photovoltaic inverter;
the photovoltaic grid-connected inverter is connected with the intelligent distribution transformer terminal unit to establish a connection, and comprises an extended power signal detection module and a photovoltaic inverter;
the extended power signal detection module is connected with the intelligent distribution transformer terminal unit through power line carrier communication to establish a connection, and is connected with the photovoltaic inverter through RS485 communication to establish a connection;
the photovoltaic inverter is respectively connected with the photovoltaic cell and the capacitor cell, receives the adjusting information and sends an adjusting instruction;
a photovoltaic cell that provides a photovoltaic inverter with a photovoltaic inverter input side voltage;
and the capacitor battery realizes the charge and discharge of the battery and stabilizes the voltage of the input side of the photovoltaic inverter.
Referring to fig. 4, there is shown a general schematic of a system according to the present invention comprising the steps of:
step one: the method comprises the steps that an extended power signal detection module acquires state information of a photovoltaic grid-connected inverter and voltage and current data information of a grid-connected point in a monitoring period of each intelligent distribution transformer terminal unit;
step two: the information acquired by the extended power signal detection module is transmitted to an intelligent distribution Transformer Terminal Unit (TTU) through RS485 communication and power line carrier communication (HPLC);
step three: the TTU calculates the voltage, the current harmonic distortion rate, the power factor and the residual capacity of the photovoltaic inverter of the grid-connected point; under the capacity limit of the photovoltaic grid-connected inverter, the intelligent distribution transformer terminal unit sends an inverter control instruction by taking the optimal electric energy quality of the public connection point as a target, and then the inverter control instruction is transmitted to the photovoltaic inverter;
step four: and controlling the output of the photovoltaic inverter according to the information fed back by the TTU unit, adjusting the working mode of the photovoltaic grid-connected inverter, and performing reactive compensation and harmonic suppression on the public connection point.
In the first step, as shown in fig. 4, an extended power signal detection module is connected near a common connection Point (PCC), and the extended power signal detection module collects information on the output side of the inverter through an RS485 interface. And the collected signals are modulated and demodulated into identifiable signals through a coupling device at the PCC end.
The extended power signal detection module reads the voltage and current information at the public connection point first, and if reactive power and harmonic current at the public connection point need to be adjusted, the extended power signal detection module reads the state of the inverter again, and the state is compensated after the residual capacity exists. The extended power signal detection module collects voltage and current to help control the photovoltaic inverter, the states of the photovoltaic inverter and the PCC point are transmitted to the TTU through the carrier, and the TTU controls the photovoltaic inverter through an intelligent power line carrier-to-RS 485 interface. The extended power signal detection module periodically inquires the state of the photovoltaic inverter, acquires the state of the PCC, and the TTU inquires the state of the PCC and the photovoltaic inverter by the extended power virtual signal detection module, and calculates related reference values.
And the power line carrier communication (HPLC) is adopted between the TTU and the extended power signal detection module, the intelligent power line carrier-to-RS 485 interface is adopted between the photovoltaic inverter and the TTU, and the photovoltaic inverter and the extended power signal detection module are in RS485 communication. And a coupling device is respectively arranged at the PCC side and the TTU side to realize the receiving and transmitting of carrier signals and the transmission of communication information. The power line carrier module is provided with a power line carrier interface, and the power line carrier module is used for establishing connection between a carrier circuit and external communication, and the communication interface uses RS485.
In the second step, as the distance between the photovoltaic inverter and the PCC point is close, the photovoltaic inverter and the extended power signal detection module are connected through a wire, and the state of the photovoltaic inverter and the state of the PCC point are sent to the TTU through a carrier circuit. The power line carrier module is characterized in that a coupling device is arranged on the grid-connected point side and the TTU side respectively and used for transmitting and receiving signals acquired by the extended power signal detection module, the coupling device isolates strong current from weak current by using a capacitive coupling mode, a high-frequency signal path is provided for preventing power frequency current from entering a weak current system, a frequency spectrum is moved in the power line carrier path, a conversion mode is modulation, and an encoder and a modulator are integrated in transmitting equipment.
And thirdly, calculating the voltage and current harmonic distortion rate, the power factor and the residual capacity of the photovoltaic inverter of the grid-connected point according to the voltage and current information acquired in the first step, and calculating by the intelligent distribution transformer terminal unit.
The specific method of the third step is to calculate the voltage and current distortion rate of the grid-connected point. The grid-connected point extended power signal detection module detects voltage and current information in real time, calculates voltage harmonic distortion rate and harmonic current according to an instantaneous reactive power method, calculates a power factor and the residual capacity of the photovoltaic inverter, and TTU forms control information and sends a control instruction. And the TTU analyzes the state of the grid-connected point according to the received information and gives a certain control instruction to control the working mode of the inverter and make an adjusting action.
The calculation formula of the voltage-current distortion rate in the third step is as follows:
u in the formula n -effective value of nth harmonic voltage, u 1 THD is the effective value of fundamental voltage u Is the voltage distortion rate.
In which I n -effective value of nth harmonic current, I 1 THD is the fundamental current effective value i Is the current distortion rate.
Calculating the residual capacity of the inverter:
P r ＝(P-Pe)×95％
p in the above r The residual capacity of the photovoltaic inverter is P, the rated power of the inverter is P e Is the grid-connected power of the inverter. And compensating the system according to the residual capacity of the inverter.
Calculating the power factor of the point of connection:active power of P-grid-connected point, reactive power of Q-grid-connected point, P b Is the power factor of the point of connection. P and Q are determined by the instantaneous reactive power method.
When the harmonic distortion rate of the voltage and the current of the grid-connected point exceeds the limit value required by the system and the power factor does not meet the system requirement, the TTU enables the photovoltaic inverter to adjust through power line carrier communication. The photovoltaic inverter suppresses harmonics and compensates reactive power according to its own remaining capacity. And actively performing functional conversion according to the voltage amplitude of the photovoltaic grid-connected point and the capacity limit of the photovoltaic inverter and the energy storage.
In the fourth step, as shown in fig. 5 and 6, the photovoltaic inverter receives feedback information from the TTU through power line carrier communication, and the photovoltaic inverter sends out corresponding output values to control output current of the photovoltaic inverter to realize harmonic suppression and reactive compensation, so that time-sharing multiplexing of the photovoltaic inverter is realized, and functions of regulating voltage to prevent voltage from exceeding limit and regulating active and reactive are realized.
The intelligent power line carrier-wave 485 interface and the photovoltaic inverter are communicated through RS485, a ModBus communication protocol is used, and the TTU can generate a control instruction to control the photovoltaic inverter according to grid-connected point detection information so as to improve the power quality of a power grid.
Referring to FIG. 5, there is shown an ip-i according to the present invention q A structural block diagram of a reactive current detection method;
the invention adopts a reactive current detection method based on instantaneous reactive power, directly takes reactive current required by a grid-connected point as a part of command current, and realizes dynamic real-time compensation of the reactive power by controlling the magnitude and phase of fundamental voltage or current. Using i p -i q The method only needs to carry out coordinate transformation processing on the current signal, and directly obtains the corresponding reactive current signal. As required to i p And i q The corresponding reactive current and harmonic current signals can be obtained by performing inverse transformation. Reactive component i generated by grid connection point Lq After reversed polarity, the current is used as command current for outputting reactive current of photovoltaic inverterAnd is in actual output with current i of the photovoltaic inverter q And comparing, then sending the signals into a PI controller, tracking the instruction current, and driving a pulse generator by the control quantity to control the on-off of a switch of the photovoltaic inverter.
FIG. 6 is a block diagram of an FFT algorithm for harmonic compensation according to the present invention, further using an FFT method to implement calculation of the filtered current:
and carrying out FFT decomposition according to the acquired current value of one period to obtain the amplitude and phase coefficient of each subharmonic, and carrying out FFT inverse transformation to synthesize the total harmonic. The inverter outputs a corresponding current suppressing harmonic.
The grid existing in the grid connection point contains higher harmonics, fourier decomposition is carried out on the higher harmonics, fundamental wave components of the voltage of the grid are obtained, and meanwhile amplitude and phase conditions of the lower harmonics can be obtained. The expression is as follows:
wherein (n=1, 2, 3)
Wherein: u (u) (t) A is the fundamental component of voltage 0 For each subharmonic amplitude, nω 0 Frequency of each subharmonic, A n Is the amplitude of the n-order harmonic, phi 0 For the ratio of phase, harmonic frequency and fundamental frequencyKnown as harmonic orders.
Fig. 9 shows the input side of a photovoltaic inverter according to the invention. The photovoltaic system comprises an MPPT module, a Boost module and a super-capacitor battery composite energy storage module, has the function of adjusting reactive power and impact load, and improves the energy efficiency ratio of the photovoltaic system and the stability of a power grid.
In the case of example 1,
the following describes a photovoltaic grid-connected inverter based on multi-mode control of an intelligent distribution transformer terminal in a specific embodiment. In order to verify the effectiveness of the device, a simulation experiment platform of a photovoltaic grid-connected inverter controlled in a multi-mode manner is built in Matlab/Simulink, three-phase 380V, 0-phase and 50Hz are used as power grid side states in the simulation model, and the switching frequency is 10KHz and the DC bus voltage U is set dc =800V, dc bus side capacitor C dc 2500 μf, inverter side capacitance C f ＝600μF、L 1 =500 μh. To testThe harmonic suppression and reactive compensation capabilities of the invention are demonstrated, and specific load harmonic and reactive power sources are simulated on the load side. The embodiment is a 10KW photovoltaic inverter, higher harmonic and reactive power are added in simulation, and the whole system device obtains good expected effect by switching operation modes of different functions.
In fig. 10, to verify the capability of harmonic suppression, a load is added to the grid output side to create a source of interference. The current waveform before power grid side harmonic compensation is intercepted, a large number of harmonics are contained, the amplitude of the visible current waveform is unstable, the higher harmonics contained in the visible power grid current are very much, and the damage is easy to generate due to the fact that the waveform does not form a sine characteristic.
Fig. 11 shows a current waveform after grid-side harmonic compensation using an FFT harmonic detection algorithm, the current harmonic content on the grid-side after compensation is greatly reduced, the current is smooth, and the total harmonic distortion is significantly reduced.
Comparing fig. 10 and fig. 11, when higher harmonics are injected into the grid-connected inverter control system, the grid-connected current waveform after the device filters is smooth, and the sine characteristic is obviously better than the grid-connected current waveform before compensation.
In fig. 12, the upper column is the current-voltage waveform before reactive power compensation on the grid side, the middle column is the compensation current waveform, and the lower column is the disturbance current waveform. The current amplitude before compensation is unstable and does not show a sine characteristic, the voltage amplitude is weak, the voltage and the current have phase difference and obviously show an advanced state, and the damage to a power grid and a user is easy to cause.
The upper column of FIG. 13 uses i p -i q And measuring current and voltage waveforms of the power grid after the reactive current detection method. The voltage after reactive compensation presents a stable state, and the phase difference is completely compensated and presents a sine waveform.
In fig. 14, the uppermost curve after 0.06s is the voltage distortion rate before compensation, and the lower curve is the voltage distortion rate after compensation, and it can be seen from the graph that the voltage distortion rate is reduced from about 0.25 to about 0.015, and the photovoltaic inverter completely improves the power quality.
It should be emphasized that the embodiments described herein are illustrative rather than limiting, and that this invention encompasses other embodiments which may be made by those skilled in the art based on the teachings herein and which fall within the scope of this invention.
The invention is not a matter of the known technology.

Claims (8)

1. The multi-mode control photovoltaic grid-connected inverter system based on the intelligent distribution transformer terminal is characterized by comprising an intelligent distribution transformer terminal unit, an extended power signal detection module, a photovoltaic inverter, a photovoltaic cell and a capacitor cell; the connection relation is as follows: the intelligent distribution transformer terminal unit is connected with the extended power signal detection module, the extended power signal detection module is connected with the photovoltaic inverter, and the input side of the photovoltaic inverter is connected with the photovoltaic cell and the capacitor cell;
the extended power signal detection module comprises a microprocessor, a signal acquisition circuit, a carrier communication interface and an RS485 communication interface; the microprocessor is respectively connected with the signal acquisition circuit, the carrier communication and the RS485 communication;
the signal acquisition circuit includes: the input IN is connected with one end of a resistor R2, the other end of the resistor R2 is connected with a 3 pin of an operational amplifier U1A, a capacitor C is connected IN parallel with a resistor R7, one end of the capacitor C is also connected with the 3 pin of the operational amplifier U1A, and the other ends of the capacitor C and the resistor R7 are grounded; the 2 pin of the operational amplifier U1A is connected with the 1 pin of the chip U1A; the 8 pins of the operational amplifier U1A are respectively connected with a-5V power supply and a capacitor C1, and the other end of the capacitor C1 is grounded; the 4 pin of the operational amplifier U1A is respectively connected with a +5V power supply and a capacitor C5, and the other end of the capacitor C5 is grounded; the 1 pin of the operational amplifier U1A is connected with one end of a resistor R1; the other end of the resistor R1 is respectively connected with the 6 pin of the operational amplifier U1B, the capacitor C2 and the 3 pin of the linear optocoupler; the 5 pin of the operational amplifier U1B is grounded; the pin 7 of the operational amplifier U1B is respectively connected with the other end of the capacitor C2 and one end of the resistor R3; the 1 pin of the linear optocoupler is connected with the other end of the resistor R3, and the 2 pin of the linear optocoupler is connected with a +12V_SO power supply; the 4 pins of the linear optocoupler are grounded; the 6 pins of the linear optocoupler are respectively connected with the 6 pins of the operational amplifier U3B and the end of the resistor R4; the 5 pins of the linear optocoupler are respectively connected with the 5 pins of the operational amplifier U3B and the ground wire; the 4 pin of the operational amplifier U3B is respectively connected with a +5V power supply and one end of a capacitor C7, and the other end of the capacitor C7 is connected with a signal ground wire; the pin 7 of the operational amplifier U3B is respectively connected with one end of a resistor R9 and the other end of a resistor R4; the 8 pin of the operational amplifier U3B is respectively connected with a +4V power supply and a capacitor C3, and the other end of the capacitor C3 is connected with a signal ground wire; the 3 pin of the operational amplifier U3A is connected with the other end of the resistor R9; the pin 2 of the operational amplifier U3A is respectively connected with a resistor R5 and a resistor R6; the other end of the resistor R5 is connected with a signal ground wire; the 1 pin of the operational amplifier U3A is connected with the other end of the resistor R6; the 1 pin of the operational amplifier U3A is also connected with one end of a resistor R8, the other end of the resistor R8 is respectively connected with an output OUT and one end of a capacitor C6, the other end of the capacitor C6 is connected with a signal ground wire, the input IN is from a signal of a place to be collected, namely a grid connection point, and the pin OUT is connected to an ad sampling port of the stm32F103.
2. The photovoltaic grid-connected inverter system based on the multi-mode control of the intelligent distribution transformer terminal as claimed in claim 1, wherein in the photovoltaic inverter, an inversion unit is connected with a power grid through an LCL filter; the inversion unit is also connected with the control unit; the power grid voltage and current sampling circuit of the control unit is directly connected with the power grid, and the middle direct current voltage sampling circuit is connected with the power grid through a user.
3. The multi-mode control photovoltaic grid-connected inverter system based on the intelligent distribution transformer terminal as claimed in claim 2, wherein the control unit of the photovoltaic inverter comprises an intermediate direct-current voltage sampling circuit, a grid voltage sampling circuit, an inverter output voltage and current sampling circuit, a microprocessor, a communication module, a control signal and an IGBT main circuit; the middle direct-current voltage sampling circuit, the power grid voltage sampling circuit and the inverter output voltage and current sampling circuit are respectively connected with the microprocessor; the communication module and the control signal are respectively connected with the microprocessor to realize mutual control; the output of the microprocessor is connected with the IGBT main circuit.
4. The intelligent distribution terminal-based multi-mode control photovoltaic grid-connected inverter system as claimed in claim 3, wherein the microprocessor in the control unit of the photovoltaic inverter is ARM GD32F407.
5. The multi-mode control photovoltaic grid-connected inverter system based on the intelligent distribution transformer terminal as claimed in claim 1, wherein the input side of the photovoltaic inverter is provided with a capacitor battery connected with the photovoltaic inverter, the input side is composed of a photovoltaic array, an MPPT module, a Boost module and a super capacitor battery composite energy storage module, the super capacitor battery composite energy storage comprises a capacitor battery and a photovoltaic battery, and the connection relation is that: the photovoltaic array is connected with the MPPT module, the MPPT module is connected with the Boost module to Boost voltage, then the MPPT module is connected with the super capacitor battery composite energy storage module, and finally the MPPT module is connected to the photovoltaic inverter.
6. The multi-mode controlled photovoltaic grid-connected inverter system based on the intelligent distribution transformer terminal as claimed in claim 1, wherein the microprocessor in the extended power signal detection module is ARM stm32F103.
7. The intelligent distribution terminal-based multi-mode control photovoltaic grid-connected inverter system according to claim 1, wherein the signal acquisition circuit uses a linear optocoupler HCNR200-000E.
8. The intelligent distribution transformer terminal-based multi-mode control photovoltaic grid-connected inverter system as claimed in claim 1, wherein the operational amplifiers U1A, 3A and the operational amplifiers U1B, 3B are LM2904.
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基于STM32F103的光伏电站智能直流汇流箱监测单元的研究;韩媛媛;周皓;陈金辉;张国瑞;;陕西电力(第06期);全文 *

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