CN109861389B - Photovoltaic microgrid energy management system based on LoRa technology - Google Patents
Photovoltaic microgrid energy management system based on LoRa technology Download PDFInfo
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Abstract
The invention relates to a photovoltaic microgrid energy management system based on an LoRa technology, and belongs to the technical field of industrial Internet of things. Contain a plurality of electric energy monitoring collection nodes, realize large capacity electric energy monitoring terminal data transmission through the loRa technique to with the data access photovoltaic microgrid energy management system of gathering, realize the function based on online monitoring, real-time analysis and processing and the decision-making optimization of the photovoltaic microgrid electric energy quality of loRa technique. The invention provides a photovoltaic microgrid energy management system based on an LoRa sensing technology, which combines the LoRa technology with a photovoltaic microgrid, carries out comprehensive monitoring analysis on a plurality of monitoring points of the photovoltaic microgrid of an intelligent factory, realizes the accurate grasping of comprehensive control and operation state, further improves the communication level of an electric power system, and controls and adjusts the operation state of microgrid electric equipment on a management platform.
Description
Technical Field
The invention belongs to the field of industrial Internet of things, and relates to a photovoltaic micro-grid energy management system based on an LoRa technology.
Background
Electricity is an indispensable energy source in our present society, and in the past, non-renewable energy sources such as coal, petroleum, natural gas and the like are main energy sources for various production activities of people. With the increasing severity of global energy and environmental issues, distributed power generation based on renewable energy has become an important component in implementing strategic plans for sustainable energy development. The development and utilization of distributed power sources is a major approach to solving the current energy problem. Currently, distributed power generation systems have been widely studied in countries around the world. Under the background, people begin to search for new energy, solar energy is one of the new energy in the 21 st century and is renewable green energy, the current situation of energy shortage is relieved to a certain extent by utilizing solar energy for power generation, the environment can be protected, and the application is very wide. Due to popularization of solar power generation and development of a micro-grid technology, more micro-grids are interconnected with a power distribution network to achieve the purposes of efficient utilization of distributed power supplies and complementation of electric energy quality, and an energy management system matched with the micro-grids gradually becomes a research hotspot.
In an automatic industrial production environment, a large number of intelligent technologies are applied, and various information data are converged in a network, so that the characteristics of the selected network directly concern the execution quality of a production plan, and the wireless transmission technology of the internet of things is a reasonable choice. The wireless transmission technology of the Internet of things comprises WiFi, bluetooth, zigBee and 2G/3G/4G, the defects of the WiFi, bluetooth, zigBee and 2G/3G/4G are obvious, the former three have short transmission distance although the power consumption is low, and the latter three have long transmission distance but high power consumption. Since LPWAN (low power wide area network) technology, both long distance and low power consumption can be realized to the greatest extent. The LoRa, which is a kind of LPWAN technology, is called 'Long Range' in its entirety, and is a novel ultra-Long-distance low-power consumption data transmission technology based on less than 1GHz, which is published by Semtech corporation in 2013, the frequency band is an unauthorized frequency band, so no extra charge is needed when in use, and LoRaWAN used by LoRa is an asynchronous communication protocol, the protocol mode not only has unique characteristics in the aspects of processing interference, network overlapping, scalability and the like, but also is very economical in power consumption, and the service life of equipment powered by batteries is greatly prolonged. However, the quality of service (QoS) is less desirable than the communication method using the cellular network. Therefore, cost-saving and large number of connections are needed, and LoRa is undoubtedly the best choice in case of low QoS requirement.
A Micro-Grid (Micro-Grid) system is also called a Micro-Grid, and refers to a small power generation and distribution system composed of a distributed power supply, an energy storage device, an energy conversion device, a load, a monitoring and protection device and the like.
The micro-grid aims to realize flexible and efficient application of distributed power supplies and solve the problem of grid connection of the distributed power supplies with large quantity and various forms. The development and extension of the micro-grid can fully promote the large-scale access of distributed power sources and renewable energy sources, realize the high-reliability supply of various energy source types of loads, and is an effective mode for realizing an active power distribution network, so that the traditional power grid is transited to a smart power grid.
Aiming at the intelligentized and informationalized requirements of the photovoltaic microgrid system, according to the future development directions of technologies such as a smart power grid and the Internet of things, the LoRa communication technology is applied to the photovoltaic microgrid system, the management of the photovoltaic microgrid system is further improved, the electric energy monitoring, analyzing and early warning capabilities of the photovoltaic microgrid system by the Internet of things technology are enhanced, the management efficiency of a manager on the photovoltaic microgrid system is improved, and the management efficiency is released to managers through an Internet platform.
Disclosure of Invention
In view of this, the invention aims to provide a photovoltaic microgrid energy management system based on an LoRa communication technology, aiming at the high-speed development of an internet of things wireless sensing technology in the current environment and the background that a photovoltaic microgrid system is widely applied to an industrial factory, so that a plurality of monitoring points in the photovoltaic microgrid system of an intelligent factory are comprehensively monitored and analyzed, the comprehensive control and the accurate grasping of the operation state are realized, the communication level of a power system is further improved, early fault information of the microgrid system and electric equipment is captured in time before the microgrid system and the electric equipment fail to operate, and a manager is informed on a management platform to adjust the operation state of the microgrid electric equipment and prevent and overhaul.
In order to achieve the purpose, the invention provides the following technical scheme:
a photovoltaic micro-grid energy management system based on an LoRa technology comprises a sensing device layer, a network communication layer and a management platform layer;
the sensing equipment layer comprises an LoRa terminal and a plurality of electric energy monitoring terminals, the LoRa terminal and the plurality of electric energy monitoring terminals are arranged in a photovoltaic array of the photovoltaic microgrid system, each electric energy monitoring terminal comprises a power supply, an electric energy monitoring module and an MCU (microprogrammed control unit) processor, and the power supplies are used for supplying power to the electric energy monitoring terminals; the electric energy monitoring module comprises a voltage sensor, a current sensor and a power sensor; the MCU processor is used for realizing control and preprocessing calculation functions;
the LoRa terminal comprises an MCU processor, a LoRa communication module, power management, an RF component and an SPI (serial peripheral interface), the LoRa terminal takes the MCU processor as a core, processes data acquired by the electric energy monitoring module to obtain indexes of electric energy quality, including voltage deviation, voltage fluctuation values and voltage flicker values, and harmonic components, total harmonic distortion rates and harmonic content rates of voltage and current, and sends the indexes to a LoRa communication base station through the RF component, and the LoRa communication module is connected with peripheral equipment through the SPI; the power supply management unit is used for supplying power to the battery;
the network communication layer comprises an LoRa communication base station, the LoRa communication base station adopts a star network architecture that an electric energy monitoring terminal jumps to a base station, the LoRa communication base station is responsible for realizing data forwarding between terminal equipment and a network server, the LoRa communication base station comprises collected data, response signals and network heartbeat information sent by a terminal in an uplink mode, the LoRa communication base station is a lossless and delay-free wireless transmission technology, and the LoRa communication base station has the function of receiving multiple channels simultaneously; a wireless communication mode is adopted between the terminal and the base station, a wireless or wired communication mode is adopted between the base station and the server, and a wired communication mode is adopted between the servers and between the server and the platform;
the management platform layer comprises a photovoltaic microgrid energy management system platform, the photovoltaic microgrid energy management system platform comprises an information acquisition module, a data monitoring module, a decision optimization module and a man-machine interaction module, and the information acquisition module is used for acquiring equipment information and working mode data in the photovoltaic microgrid system and electric energy monitoring terminal data sent by a LoRa base station; the data monitoring module is used for detecting the acquired data and storing the acquired data in a database; the decision optimization module is used for optimizing the operation condition of the distributed power supply of the photovoltaic micro-grid system according to the acquired data; the man-machine interaction module is used for displaying monitoring data and decision information in the photovoltaic micro-grid energy management system and inputting data into the system, so that the states of the switch and the disconnecting link are operated in real time, and the working mode of the micro-grid is controlled.
Further, the LoRa terminal uses an STM32 low-power consumption MCU; the RF part selects SX1278 as an RF device; the antenna adopts a folding rod antenna and is fixed at the upper right corner of the bottom plate by adopting a TNC interface; the device also comprises an indicator light which adopts a light-emitting diode and comprises a power supply indicator, a transceiving indicator and an error indicator.
Furthermore, the photovoltaic microgrid system adopts an alternating current-direct current hybrid microgrid structure, the photovoltaic array system is connected to a direct current bus through a bidirectional DC/DC converter, the energy storage unit realizes bidirectional circulation of active power through the bidirectional DC/DC converter, the direct current bus and an alternating current bus are further connected through the DC/AC converter, and the alternating current side is connected with a load and a mains supply through a switch.
Further, in the alternating current-direct current hybrid photovoltaic microgrid structure, the energy storage unit adopts a storage battery and super capacitor hybrid energy storage mode, the photovoltaic array and the energy storage unit are regarded as a whole, and a Virtual Synchronous Generator (VSG) control technology is adopted for an inverter in the photovoltaic microgrid structure.
Further, the photovoltaic microgrid energy management system provides an energy management control strategy based on a Virtual Synchronous Generator (VSG), the photovoltaic array power generation amount and the energy storage unit charge State (SOC) are connected into the VSG control, and the photovoltaic array, the energy storage unit, the inverter and the commercial power are coordinately controlled by adjusting the droop characteristic of the VSG.
The basis of photovoltaic microgrid energy management is to keep energy supply and demand balance in the system and meet the requirements at any time in the system operation process:
P V +P S +P GRID ＝P L (1)
wherein, P V Is the power, P, generated by the photovoltaic array S Is the power absorbed or emitted by the energy storage unit, P GRID Is the power fed back to the mains supply by the mains supply load or the microgrid, P L Is the power required by the load.
The super capacitor in the energy storage unit is responsible for absorbing and releasing high-frequency power, and the storage battery is used as a long-time energy storage device for absorbing and releasing low-frequency power. SOC of the battery:
Q max ＝ess max n (3)
Q max and Q use Respectively representing the maximum electric quantity of the storage battery pack and the electric quantity consumed by the storage battery pack; i is the battery current; ess max Storing the maximum electric quantity for the single battery; n is the number of series-connected battery packs; ess SOC Setting the storage battery for the initial SOC value of the single batteryThe discharge was stopped when the SOC was less than 30%. The SOC calculation method of the battery is obtained by substituting expressions (2) and (3) for expression (4).
(1) If 30 percent<SOC<100%, the energy storage unit state of charge is normal, and the photovoltaic array runs at Maximum Power Point (MPP), and VSG control inverter makes the system output power according to the flagging characteristic. When P is present V >P L When the photovoltaic array is charged, the energy storage unit is charged, and the photovoltaic array bears load power supply; when P is present V <P L And when the energy storage unit is in use, the energy storage unit discharges to bear the load power supply.
(2) If SOC =100%, the energy storage unit electric quantity is saturated, and the photovoltaic array operates in MPP, adjusts VSG control, increases the inverter output, and the energy storage unit stops to charge and feedbacks surplus electric quantity to the commercial power. Up to P V ＝P L When the load is supplied, the load is only borne by the photovoltaic array.
(3) If the SOC is less than 30%, the residual capacity of the energy storage unit is insufficient, the discharging is stopped, and the recovery of the state of charge of the energy storage unit is taken as a primary control target. The photovoltaic array converter adopts Maximum Power Point Tracking (MPPT) control, adjusts VSG control, reduces inverter output power, opens a power grid switch, and the mains supply preferentially bears load power supply.
(4) Under the conditions of sudden load power change and sudden photovoltaic array output power change, the power required to be balanced by the energy storage system is divided into a low-frequency part and a high-frequency part, the super capacitor is responsible for absorbing and releasing high-frequency power, and the storage battery absorbs and releases low-frequency power. The invention has the beneficial effects that:
1) The LoRa communication technology is adopted, the terminal equipment uses the RF chip with low power consumption and low cost, the base station has the function of receiving multiple channels simultaneously and has ultrahigh sensitivity receiving capability, and theoretically, millions of equipment can be supported only by a small number of base stations. The whole system has the characteristics of low cost, large system capacity, wide coverage range, simplicity in layout and maintenance and the like.
2) Through an electric energy monitoring device deployed on the microgrid equipment, voltage deviation, voltage fluctuation values (including voltage deviation and statistical data thereof) and voltage flicker values, indexes of electric energy quality such as harmonic components, total harmonic distortion rate and harmonic content of voltage and current are obtained through real-time measurement and online processing, and the information is timely transmitted to an energy management platform through a low-power-consumption wide area sensing network LoRa to be processed, so that functions of online electric energy quality detection, optimization of electric power facility operation and the like are realized.
3) Aiming at the characteristics of energy management of a photovoltaic micro-grid power generation system, an energy management control strategy based on a Virtual Synchronous Generator (VSG) is provided, the generated energy of a photovoltaic array and the state of charge (SOC) of an energy storage unit are accessed into the VSG control, the coordination control of the photovoltaic array, the energy storage unit, an inverter and a mains supply is realized by adjusting the droop characteristic of the VSG, and the grid-connected stability of the photovoltaic micro-grid is well maintained.
4) The application scene of the photovoltaic microgrid is expanded, the solar power generation technology is applied to the field of intelligent factories, and the practical problems that the power supply of most factories is inflexible, the power supply is interrupted, the production management is disordered and the like are hopefully solved.
Drawings
In order to make the purpose, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:
FIG. 1 is a system architecture framework diagram of the present invention;
FIG. 2 is a frame diagram of the overall functional structure of the power monitoring terminal of the present invention;
FIG. 3 is a frame diagram of the LoRa terminal hardware layout structure of the present invention;
fig. 4 is a frame diagram of a photovoltaic microgrid energy management system platform of the present invention;
fig. 5 is a structural framework diagram of the photovoltaic microgrid system of the present invention.
Detailed Description
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in figure 1, the photovoltaic micro-grid energy management system based on LoRa communication is characterized in that electric energy monitoring terminals are installed on each photovoltaic array in an intelligent factory photovoltaic micro-grid system, the photovoltaic arrays are more and widely distributed, and the physical positions of the electric energy monitoring terminals are far away from each other.
Fig. 2 is a frame diagram of the overall functional structure of the power monitoring terminal, and the power monitoring terminal mainly includes: the power supply is used for the power supply requirement of the electric energy monitoring terminal system and is designed into a battery power supply mode; the electric energy monitoring terminal comprises a voltage sensor, a current sensor and a power sensor; the MCU processor is used for realizing various control and preprocessing calculation functions, aiming at the applied sensor, and interfaces and power supply management units among the parts; and the LoRa wireless transmission module realizes wireless data receiving and transmitting. The photovoltaic microgrid equipment comprises a voltage change sensor, a current change sensor and a power sensor device which are deployed on the photovoltaic microgrid equipment, the voltage deviation, the voltage fluctuation value (including voltage deviation and statistical data) and the voltage flicker value, the indexes of the power quality such as harmonic components, total harmonic distortion rate and harmonic content rate of voltage and current are obtained through real-time measurement and online processing, and the information is timely transmitted to an energy management system platform through a LoRa low-power-consumption wide area sensing network, so that the functions of online power quality detection, energy optimization decision making and the like are realized.
Fig. 3 is a frame diagram of a layout structure of the LoRa terminal hardware, and the LoRa terminal hardware structure includes a LoRa communication module, a power management interface, an SPI interface, and other components; the LoRa terminal takes an MCU processor as a core, processes data acquired by the electric energy detection module to obtain indexes of electric energy quality, including voltage deviation, voltage fluctuation values, voltage flicker values, harmonic components, total harmonic distortion rates and harmonic content rates of voltage and current, and sends the data to the LoRa base station through the LoRa RF part, and the system uses an STM32 low-power-consumption MCU; the RF part of the LoRa terminal selects SX1278 as an RF device according to the requirement of the China wireless frequency band; the sensor unit part selects a voltage sensor, a current sensor and a power sensor as a module data acquisition terminal; the antenna type adopts a folding rod antenna, and the antenna adopts a TNC interface and is fixed at the upper right corner of the bottom plate; the communication module is connected with peripheral equipment through an SPI interface, and a liquid crystal display interface is selectable; the indicator light adopts emitting diode, is respectively: power indication, transmit and receive indication and error indication; the power management unit is designed to be in a battery powered mode.
Fig. 4 is a frame diagram of a platform of the photovoltaic microgrid energy management system, and the photovoltaic microgrid energy management system has functions of data monitoring and decision optimization. Some external information such as equipment information and working modes are transmitted to the microgrid energy management system through the data interface, and meanwhile, the microgrid energy management system exchanges information with the distributed power supplies through the interface. The man-machine communication is mainly responsible for the communication between people and the energy management system, adopts a visual man-machine interface and provides a uniform graphic platform. The topological structure of the microgrid and the access conditions of all electrical elements can be checked through a human-computer interface, the states of the switch and the disconnecting link can be operated in real time, and the working mode of the microgrid is controlled. The voltage, current and power real-time data collected by the monitoring system are displayed in the graphic system. By monitoring the human-computer interface, the working personnel can know the operation conditions of the micro-grid system, the background system and the communication system in real time. The running information of the system can be displayed in a human-computer interface in various modes such as characters, graphs, sound and light, colors and the like. The data monitoring module stores real-time data and historical data acquired by the system into a database of the system, flexibly organizes the data into a form to form a real-time historical statistical report form of day, month, year and the like, and has the functions of printing and form editing. Decision optimization is a core module of the photovoltaic microgrid energy management system. The optimization system decides the power generation scheduling of the distributed power supply, a power purchase plan from a power grid, output distribution of stored energy, load arrangement according to information such as the power generation amount of load and renewable energy, the power demand of a user, a scheduling rule, market price and the like, wherein the decision needs to meet a series of constraint conditions and control targets, the energy consumption and the system loss are minimized as far as possible, and the operation efficiency of the distributed power supply is maximized.
Fig. 5 is a photovoltaic microgrid system structure, the photovoltaic microgrid system adopts an alternating current-direct current hybrid microgrid structure, a photovoltaic array system is used as a distributed power generation unit and is connected to a direct current bus through a bidirectional DC/DC converter, an energy storage unit adopts a storage battery and a super capacitor, bidirectional circulation of active power is realized through the bidirectional DC/DC converter, then the direct current bus and an alternating current bus are connected through the DC/AC converter, and an alternating current side is connected with a load and commercial power through a switch. The photovoltaic array and the energy storage unit are considered as a whole, and a Virtual Synchronous Generator (VSG) control technology is adopted for an inverter in the photovoltaic array and the energy storage unit.
The microgrid mainly comprises 3 typical structures of an alternating current microgrid, a direct current microgrid and an alternating current-direct current hybrid microgrid. Compare in single photovoltaic microgrid structure, the mixed microgrid of alternating current-direct current has combined the advantage of direct current microgrid on the basis of exchanging the microgrid, has following advantage: the existence of the direct current bus and the alternating current bus meets the requirements of alternating current or direct current distributed power generation and load, reduces AC/DC or DC/AC conversion links, and reduces the use of power electronic devices, thereby inhibiting harmonic waves; the alternating-current and direct-current hybrid micro-grid can be independently controlled and can be used for standby at the same time, so that the reliability of the system is improved; the alternating current-direct current hybrid microgrid has better ductility and wider application. In the alternating current and direct current hybrid microgrid, an alternating current (DG) or a load is directly connected into an alternating current bus, a direct current (DG) or the load is directly connected into a direct current bus, and the balance of power flow is realized between the alternating current bus and the direct current bus through a bidirectional converter. The AC/DC hybrid micro-grid has better economical efficiency, safety and reliability, and is widely concerned at home and abroad.
The photovoltaic microgrid energy management system provides an energy management control strategy based on a Virtual Synchronous Generator (VSG), the photovoltaic array generating capacity and the energy storage unit charge State (SOC) are connected into the VSG control, and the photovoltaic array, the energy storage unit, the inverter and the commercial power are coordinately controlled by adjusting the droop characteristic of the VSG.
The basis of photovoltaic microgrid energy management is to keep energy supply and demand balance in the system and meet the following requirements at any time in the system operation process:
P V +P S +P GRID ＝P L (1)
wherein, P V Is the power generated by the photovoltaic array, P S Is the power absorbed or emitted by the energy storage unit, P GRID Is the power fed back to the mains supply by the mains supply load or the microgrid, P L Is the power required by the load.
The super capacitor in the energy storage unit is responsible for absorbing and releasing high-frequency power, and the storage battery is used as a long-time energy storage device for absorbing and releasing low-frequency power. SOC of the battery:
Q max ＝ess max n (3)
Q max and Q use Respectively representing the maximum electric quantity of the storage battery pack and the electric quantity consumed by the storage battery pack; i is the battery current; ess max Storing the maximum electric quantity for the single battery; n is the number of series-connected battery packs; ess SOC And setting the SOC of the storage battery to be lower than 30% for the initial SOC value of the single battery, and stopping discharging. The SOC calculation method of the battery is obtained by substituting expressions (2) and (3) for expression (4).
(1) If 30 percent<SOC<And when the charge state of the energy storage unit is normal by 100%, the photovoltaic array operates at the Maximum Power Point (MPP), and the VSG controls the inverter to enable the system to output power according to the droop characteristic. When P is V >P L When the photovoltaic array is charged, the energy storage unit is charged, and the photovoltaic array bears load power supply; when P is V <P L And when the energy storage unit discharges, the energy storage unit bears the load power supply.
(2) If the SOC =100%, the electric quantity of the energy storage unit is saturated, the photovoltaic array operates at the MPP, the VSG control is adjusted, the output of the inverter is increased, the energy storage unit stops charging, and the surplus electric quantity is fed back to the commercial power. Up to P V ＝P L When the load is supplied, the load is only borne by the photovoltaic array.
(3) If the SOC is less than 30%, the residual capacity of the energy storage unit is insufficient, the discharging is stopped, and the recovery of the state of charge of the energy storage unit is taken as a primary control target. The photovoltaic array converter adopts Maximum Power Point Tracking (MPPT) control, adjusts VSG control, reduces inverter output power, opens a power grid switch, and the mains supply preferentially bears load power supply.
(4) Under the conditions of sudden load power change and sudden photovoltaic array output power change, the power required to be balanced by the energy storage system is divided into a low-frequency part and a high-frequency part, the super capacitor is responsible for absorbing and releasing high-frequency power, and the storage battery absorbs and releases low-frequency power.
Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (4)
1. The utility model provides a photovoltaic microgrid energy management system based on loRa technique which characterized in that: the system comprises a perception device layer, a network communication layer and a management platform layer;
the sensing equipment layer comprises LoRa terminals and a plurality of electric energy monitoring terminals, the LoRa terminals and the electric energy monitoring terminals are arranged in a photovoltaic array of the photovoltaic microgrid system, each electric energy monitoring terminal comprises a power supply, an electric energy monitoring module and an MCU processor, and the power supplies are used for supplying power to the electric energy monitoring terminals; the electric energy monitoring module comprises a voltage sensor, a current sensor and a power sensor; the MCU processor is used for realizing control and preprocessing calculation functions;
the LoRa terminal comprises an MCU processor, a LoRa communication module, power management, an RF component and an SPI (serial peripheral interface), the LoRa terminal takes the MCU processor as a core, processes data acquired by the electric energy monitoring module to obtain indexes of electric energy quality, including voltage deviation, voltage fluctuation values and voltage flicker values, and harmonic components, total harmonic distortion rates and harmonic content rates of voltage and current, and sends the indexes to a LoRa communication base station through the RF component, and the LoRa communication module is connected with peripheral equipment through the SPI; the power management unit is used for supplying power to the battery;
the network communication layer comprises an LoRa communication base station, the LoRa communication base station adopts a star network architecture that an electric energy monitoring terminal jumps to a base station, the LoRa communication base station is responsible for realizing data forwarding between terminal equipment and a network server, the LoRa communication base station comprises collected data, response signals and network heartbeat information sent by a terminal in an uplink mode, the LoRa communication base station is a lossless and delay-free wireless transmission technology, and the LoRa communication base station has the function of receiving multiple channels simultaneously; a wireless communication mode is adopted between the terminal and the base station, a wireless or wired communication mode is adopted between the base station and the server, and a wired communication mode is adopted between the servers and between the server and the platform;
the management platform layer comprises a photovoltaic micro-grid energy management system platform, the photovoltaic micro-grid energy management system platform comprises an information acquisition module, a data monitoring module, a decision optimization module and a man-machine interaction module, and the information acquisition module is used for acquiring equipment information and working mode data in the photovoltaic micro-grid system and electric energy monitoring terminal data sent by an LoRa base station; the data monitoring module is used for detecting the acquired data and storing the acquired data in a database; the decision optimization module is used for optimizing the operation condition of the distributed power supply of the photovoltaic micro-grid system according to the acquired data; the man-machine interaction module is used for displaying monitoring data and decision information in the photovoltaic microgrid energy management system and inputting data into the system, so that the states of the switch and the disconnecting link are operated in real time, and the working mode of the microgrid is controlled;
the photovoltaic microgrid energy management system provides an energy management control strategy based on VSG, the generated energy of a photovoltaic array and the state of charge (SOC) of an energy storage unit are accessed into VSG control, the coordination control of the photovoltaic array, the energy storage unit, an inverter and mains supply is realized by adjusting the droop characteristic of the VSG, and the stable operation of the photovoltaic microgrid system is maintained;
the basis of photovoltaic microgrid energy management is to keep energy supply and demand balance in the system and meet the following requirements at any time in the system operation process:
P V +P S +P GRID ＝P L (1)
wherein, P V Is the power, P, generated by the photovoltaic array S Is the power absorbed or emitted by the energy storage unit, P GRID Is the power fed back to the mains supply by the mains supply load or the microgrid, P L Is the power required by the load;
the super capacitor in the energy storage unit is responsible for absorbing and releasing high frequency power, and the battery absorbs and releases low frequency power, the SOC of battery as long-time energy memory:
Q max ＝ess max n (3)
Q max and Q use Respectively representing the maximum electric quantity of the storage battery pack and the electric quantity consumed by the storage battery pack; i is the battery current; ess max Storing the maximum electric quantity for the single battery; n is the number of series-connected battery packs; ess SOC Setting the SOC of the storage battery to be lower than 30% for stopping discharging for the initial SOC value of the single battery; substituting the expressions (2) and (3) into the expression (4) to obtain an SOC calculation mode of the storage battery;
(1) If 30 percent<SOC<The charging state of the energy storage unit is normal 100%, the photovoltaic array operates at the maximum power point MPP, and the VSG controls the inverter to enable the system to output power according to the droop characteristic; when P is present V >P L When the photovoltaic array is charged, the energy storage unit is charged, and the photovoltaic array bears load power supply; when P is present V <P L When the energy storage unit discharges, the energy storage unit bears the load power supply;
(2) If SOC =100%, the electric quantity of the energy storage unit is saturated, the photovoltaic array operates at MPP, VSG control is adjusted, the output of the inverter is increased, the energy storage unit stops charging, and surplus electric quantity is fed back to the commercial power; up to P V ＝P L At the time of, only byThe photovoltaic array bears load power supply;
(3) If the SOC is less than 30%, the residual electric quantity of the energy storage unit is insufficient, the discharging is stopped, and the recovery of the charge state of the energy storage unit is taken as a primary control target; the photovoltaic array converter adopts Maximum Power Point Tracking (MPPT) control, adjusts VSG control, reduces the output power of the inverter, opens a power grid switch, and the mains supply preferentially bears load power supply;
(4) Under the conditions of sudden load power change and sudden photovoltaic array output power change, the power required to be balanced by the energy storage system is divided into a low-frequency part and a high-frequency part, the super capacitor is responsible for absorbing and releasing high-frequency power, and the storage battery absorbs and releases low-frequency power.
2. The photovoltaic microgrid energy management system based on the LoRa technology of claim 1, wherein: the LoRa terminal uses an STM32 low-power consumption MCU; the RF part selects SX1278 as an RF device; the antenna adopts a folding rod-shaped antenna and is fixed on the bottom plate by adopting a TNC interface; the device also comprises an indicator light which adopts a light-emitting diode and comprises a power supply indicator, a transceiving indicator and an error indicator.
3. The photovoltaic microgrid energy management system based on the LoRa technology of claim 1, wherein: the photovoltaic microgrid system adopts an alternating current-direct current hybrid microgrid structure, the photovoltaic array system is connected to a direct current bus through a bidirectional DC/DC converter, the energy storage unit realizes bidirectional circulation of active power through the bidirectional DC/DC converter, the direct current bus and an alternating current bus are further connected through the DC/AC converter, and the alternating current side is connected with a load and a commercial power through a switch.
4. The photovoltaic microgrid energy management system based on an LoRa technology of claim 3, characterized in that: the energy storage unit adopts a storage battery and super capacitor hybrid energy storage mode, the photovoltaic array and the energy storage unit are regarded as a whole, and a virtual synchronous generator VSG control technology is adopted for an inverter in the energy storage unit.
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| CN111427930A (en) * | 2020-03-30 | 2020-07-17 | 广东电科院能源技术有限责任公司 | Low-voltage photovoltaic energy storage microgrid device monitoring management system, method and device |
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| CN112396907A (en) * | 2020-11-26 | 2021-02-23 | 国网浙江省电力有限公司培训中心 | Electric power thing networking integration simulation is real to be instructed device |
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| CN113794749A (en) * | 2021-08-09 | 2021-12-14 | 北京国电通网络技术有限公司 | Communication equipment and system for monitoring state of power distribution network |
| CN114488988B (en) | 2022-04-14 | 2022-07-08 | 成都秦川物联网科技股份有限公司 | Industrial Internet of things for production line balance rate regulation and control method |
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