AU2018102188A4 - Method for controlling stability when microgrid grid connection switches to island operation mode - Google Patents
Method for controlling stability when microgrid grid connection switches to island operation mode Download PDFInfo
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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
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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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
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Abstract
The invention discloses a method for controlling stability of a transition from grid-connected
operation to island mode operation of a microgrid, wherein a microgrid central controller and a rapid
measurement and control unit are employed to acquire electrical quantities of the microgrid and
liaison line and to receive an instruction from a superior system, thereby obtaining real-time
operation state of the microgrid; in the case of planned island, the real-time load and power output
of the microgrid system are calculated to determine whether source-load are balanced; otherwise, if
the system satisfies the island criterion, the main power supply is switched to a V/f operation mode
from a PQ operation mode, and the PCC switch is disconnected to determine whether the system
operates normally, if the system is abnormal, a fault circuit is immediately tripped once detected,
and the determination restarted; if the system is normal, whether source-load are balanced in the
microgrid is determined, if source-load are unbalanced, calculating a power unbalance value, the
storage battery output is adjusted, whether source-load are balanced is determined again, if source
load unbalanced, low-voltage/low-frequency load shedding is carried out, and the balance is
determined again. The invention can realize the effect of simple detection and renders good stability.
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Description
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Description
Method for Controlling Stability of Transition from Grid-connected Operation to Island Mode Operation of Microgrid
Technical Field The invention relates to the technical field of microgrid, in particular to a method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid.
Background Art Traditional primary energy, such as coal, oil and so on, is not renewable, and it's an inevitable choice to solve increasingly prominent conflicts between energy demand growth and energy shortage, and between energy utilization and environmental protection in the process of rapid economic and social development by improving energy utilization efficiency, developing new energy, promoting the utilization of renewable energy. Currently, through the long-term development of distributed power generators such as photovoltaic power generation, wind power generation, fuel cells, micro-gas turbines, internal combustion engines, and the like, great progress has been made in technology. In China, it's planned that by 2020, the total installed capacity of the generator will reach nearly 100 billion kilowatts, and the proportion of distributed energy including small hydropower stations will exceed 20%. It is the most effective way of making the best of a distributed power generation and energy supply system to realize distributed power generation by connecting a microgrid to a large power grid, the so-called microgrid is a small-sized power generation and distribution system composed of a distributed generator, a storage battery device, an energy conversion device, related loads, a monitoring and protection device, and an autonomous system capable of realizing self-control, protection and management. A microgrid can operate in a grid-connected mode by connecting to a large power grid (a connecting switch of the microgrid with the large power grid is closed) or in an island mode (a connecting switch of the microgrid with the large power grid is disconnected). The capability of dual-mode operation in the grid-connected and the island modes is the key to realizing the technical and economic advantages of a microgrid. When the microgrid needs to operate independently according to the circumstances or the main power grid fails, the microgrid should be disconnected immediately from the main power grid and switched into the island mode; and when the power supply of the main power grid returns to normal or the microgrid has to operate in the grid-connected mode according to circumstances, the microgrid in the island mode is reconnected to the public power grid. Smooth and stable switching is the key technology to ensure the stable transition of microgrid between the two operation modes. In the mode switching process, corresponding operation control strategies are to be employed to ensure the stability of the switching process. The control strategy of micro-power supply not only determines the operation of a microgrid in two modes, but also directly affects the switching process between the operation modes. In Document
[1] (Wang Zan, Xiao Lan,Yao Zhilei. Design and Implementation of Grid-connected and Island Dual-mode Control High Performance Inverter [J]. Chinese Journal of ElectricalEngineering, 2007, 27 (1): 54-59, Yang Zilong, Wu Chunsheng. Design of Three-phase Grid-connected/Island Dual-mode Inverter System [J]. Power Electronics, 2010, 44 (1): 14-16), a dual-mode inverter is set forth, PQ current control is employed for the grid-connected operation, V/f control is employed for island operation, satisfying the requirement of the operation of a microgrid, however, having risks of failures in switching due to high difficulties in switching between voltage control and current control. In Document [2] (Wang Chengshan, Xiao Zhaoxia, Wang Shouxiang, Microgrid Integrated Control and Analysis [J]. Power System Automation, 2008, 32 (7): 98-103), droop control is employed, and the micro power supply control strategy is kept unchanged in the island mode and the grid-connected mode, satisfying the plug-and-play features, however, without considering the adaptability of droop control to the grid-connected operation and the impact current suppression in the process switching to the grid-connected mode. The Chinese patent application No. 2015104442425.2, published on November 4, 2015, discloses a signal control system and method for a microgrid in grid-connected and island operation modes, wherein the signal control method for the microgrid in the grid-connected and island operation modes determines whether a substation sends a state signal to the microgrid by detecting a voltage or current signal between a microgrid side common coupling point and a grid-connected circuit breaker; the microgrid control system sends an instruction to the grid-connected circuit breaker to disconnect or connect at a proper time according to the type of the signal, assisting the transition of the microgrid between the grid-connected state and the island state; the system includes a control system, a pulse signal system, and a voltage detection system. The invention has stable and reliable performance; the main power grid has a reliable means to actively inform the microgrid of the operation state to switch to, so that the cost is greatly reduced; the microgrid is facilitated to quickly and smoothly transit between the island operation state and the grid-connected operation state, so that the microgrid can operate safely and stably; the requirements of a power grid operator for effectively controlling the microgrid are satisfied. However, the invention detects by a transducer, featuring low efficiency and inadequate accuracy. The Chinese patent application No. 201310509652.3, published on February 19, 2014, discloses a stability control method when a microgrid is switched from a grid-connected state to an island state, wherein before the microgrid is disconnected from a power grid in the case of planned switching, a microgrid stability control system collects a power at the grid-connected point, configures a power supply and a load to enable source-load to be basically balanced, and simultaneously sends the transmission power at the grid-connected point to an inverter before the disconnection; a grid connected point breaker is stably disconnected, so that output power of the inverter is kept to be equal to the transmission power at the grid-connected point before the disconnection, and the power of the microgrid immediately reaches a balance after the microgrid is disconnected from the power grid. In the case of unplanned switching, the microgrid is suddenly disconnected from the power grid and forms an island, and the load is intertripped or a partial power branch circuit is disconnected within 10 ms according to a difference between a power flow at the grid-connected point before the disconnection and an output maximum power of a storage battery inverter, so that the stability at the moment of switching of the system is ensured; the storage battery inverter with the maximum capacity immediately switches to V/f control, and other power supplies are set to be under P/Q control. This method can realize smooth switching of the microgrid from the grid-connected state to the island state. However, the control only targets switching and stable control of the power supply branch circuit, featuring defects in integral stable control, because specific disconnection is not realized to ensure the stability, and thus the stability is insufficient. The Chinese patent application No. 201410458561.6, published on February 19, 2014, discloses a stability control method for unplanned switching of a microgrid from a grid-connected mode to an island mode, the method combines adjustments of a power supply and a load capacity in the microgrid and adjustments of output power of a storage battery unit to detect operating frequencies and voltage levels of the microgrid in real time, thereby realizing feedback control, and at last, the stable operation for unplanned switching of the microgrid from the grid-connected mode to the island mode. The safety of various electrical appliances is guaranteed, and the uninterrupted power supply for important users is secured, featuring a promising prospect. However, the detection method is complex, high in costs, and insufficient in the stability control efficiency. any references to prior art should not be taken as admissions of common general knowledge in the field
Summary of the Invention It's an object of the invention to solve the problems in the prior art by providing a method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid, having the advantages of simple detection, good stability, and high stability control efficiency. The object of the invention is realized by the following technical solution.
In a first embodiment, a method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid, comprising the following steps : 1) acquiring electrical quantities of a microgrid and liaison line through a microgrid central controller and a rapid measurement and control unit and receiving an instruction from a superior system to obtain a real-time operating state of the microgrid, and then implementing step 2); 2) determining whether the transition to the island mode is planned, if the transition to the island mode is planned, implementing step 3); if not, implementing step 4); 3) calculating a real-time load and a power supply output of the microgrid system, and determining whether source-load are balanced; if source-load are unbalanced, adjusting a storage battery output or tripping a controllable load, and implementing step 3) again; if source-load are balanced, disconnectinga PCC (Point of Common Coupling) switch upon arrival at a planned switching time point, and returning to implement step 1) when each distributed generator operates normally and source-load are balanced in the microgrid; 4) determining by the microgrid central controller whether the system satisfies an island criterion, if the island criterion is satisfied, switching a main power supply to a V/f operation mode from a PQ operation mode, implementing step 5) after the PCC switch is disconnected, and otherwise, returning to step 1); and ) determining whether the system operates normally: if the system is abnormal, immediately tripping a fault circuit once detected, and restarting step 5); if the system is normal, determining whether source-load are balanced in the microgrid, and if source-load are balanced, returning to step 1); if source-load are unbalanced, calculating a power unbalance value, adjusting the storage battery output, determining whether source-load are balanced again, if source-load are balanced, returning to step 1), otherwise, carrying out low-voltage/low-frequency load shedding, and determining whether source-load are balanced again. In a second embodiment, the microgrid central controller is used for acquiring electrical quantities of the microgrid and the liaison line, wherein the electrical quantities of the microgrid and the liaison line comprise a current and switch positions on the liaison line, a bus voltage and a frequency of the microgrid, a current and switch positions of each micro power supply circuit, and a current and switch positions of each load circuit. In a third embodimen, the rapid measurement and control unit is installed on an incoming line of each load circuit, the rapid measurement and control unit is used for acquiring electrical information of each load circuit and providing overcurrent protection for the load circuit, and the rapid measurement and control unit is communicated with the microgrid central controller, uploads the electrical information of the load circuit to the microgrid central controller and receives remote control from the microgrid central controller.
In a fourth embodiment, GOOSE communication is employed among the microgrid central controller, the rapid measurement and control unit and the superior system. Further, the microgrid comprises a wind turbine generator, a photovoltaic cell panel and a storage battery. In a fifth embodiment, the microgrid is connected with an external power grid through a PCC point, an inverter is used as an interface between a distributed generator and a storage battery system, and the PCC point and the inverter are controlled to be disconnected and connected through a microgrid control system. In a sixth embodiment, the PCC point, a power supply branch circuit and a load branch circuit are disconnected and connected through a remote control module. In a seventh embodiment, the main power supply in step 4) is provided by a storage battery system, and the microgrid can operate in a PQ mode during the grid-connected operation to provide stable power for the microgrid; and the microgrid can operate in a V/f mode during the island mode operation to provide stable voltage and frequency support for the microgrid. In a eighth embodiment, the criterion for determining the balance of source-load of the microgrid in step 3) and step 5) lies in that all the power of the power supply in the system are equal to the
power of the load, i.e., PDG -LOAD, the power value is obtained by the microgrid central controller and the rapid measurement and control unit through high-speed sampling and data capture after calculation, i.e., 64 points are sampled in each cycle, and measured values are averaged after three cycles, whereby on the basis of rapid response, the determination of the balance is ensured to be accurate. In a nineth embodiment, the balance adjustment in step 3) and step 5) comprises the steps of: calculating an unbalanced value of power of the microgrid system, adjusting the storage battery output according to a result of the calculation, and carrying out low-voltage/low-frequency load shedding when source-load are unbalanced: classifying the load as an important load and a controllable load according to a priority of the load, preferentially tripping the controllable load, ensuring that the important load is not interrupted and the controllable load encounters fewer interruptions, until source-load are balanced. Compared with the prior art, the invention has the following advantages: (1) according to the control method, a microgrid central controller is used as a main control unit, a rapid measurement and control unit is used as a local control unit to acquire electrical quantities of each circuit of the microgrid and receives an instruction issued by an energy management system. The load is switched and the storage battery system is adjusted according to the identified power grid state, so that the microgrid can stably operate in the transition between the operation modes, and the power supply reliability of the microgrid is further improved;
(2) according to the invention, the acquired microgrid data are taken as a criterion to determine the state of the microgrid, and by controlling the output of the storage battery device and the switching of the load, the stability of the microgrid in the transition between the operation modes is effectively improved, the power supply reliability of the microgrid is improved, and the power failure range of the microgrid is reduced; (3) according to the technical solution, the data of the microgrid are monitored on line in real time, featuring high sensitivity, quick switching response, high efficiency, and good stability control; (4) according to the technical solution, a remote control module is employed, the PCC point and each circuit of the microgrid are disconnected and connected through remote control to conduct internal switching of the microgrid, the remote control reduces the cost and renders high efficiency.
Brief Description of the Drawings Fig. 1 is a schematic view showing an overall structure of a microgrid; Fig. 2 is a flow chart of the present invention.
Detailed Description of the Invention The feature of preferred embodiment relates to operation and stability control of a microgrid, in particular to a method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid. According to the control method, a microgrid central controller is used as a main control unit to acquire electrical quantities of each circuit of the microgrid and receives an instruction issued by an energy management system. The load is switched and the storage battery system is adjusted according to the identified power grid state, so that the microgrid can stably operate in the transition between the operation modes, and the power supply reliability of the microgrid is further improved. It's an object of the feature of preferred embodiment to solve the problems in the prior art concerning the transition from the grid-connected operation to the island mode operation of a microgrid by providing a method for controlling stability of the transition from the grid-connected operation to the island mode operation of the microgrid, to improve the operation reliability and reduce the power failure range of the microgrid. The feature of preferred embodiment will now be described in detail with reference to the accompanying drawings and embodiments. As shown in Fig. 1, the microgrid includes two photovoltaic power generation systems, two wind power generation systems, two storage battery systems and two loads. One of the storage battery systems is taken as the main power supply, the other distributed generators run in a PQ mode. AC load I is a primary load, and AC load 11 is the other adjustable load.
As shown in Fig. 2, the method for controlling stability of the transition from the grid-connected operation to the island mode operation of the microgrid includes the steps of: 1) acquiring electrical quantities of a microgrid and liaison line through a microgrid central controller and a rapid measurement and control unit and receiving an instruction from a superior system to obtain a real-time operating state of the microgrid, and then implementing step 2); 2) determining whether the transition to the island mode is planned, if the transition to the island mode is planned, implementing step 3); if not, implementing step 4); 3) calculating a real-time load and a power supply output of the microgrid system, and determining whether source-load are balanced; if source-load are unbalanced, adjusting a storage battery output or tripping a controllable load, and implementing step 3) again; if source-load are balanced, disconnecting a PCC switch upon arrival at a planned switching time point, and returning to implement step 1) when each distributed generator operates normally and source-load are balanced in the microgrid; 4) determining by the microgrid central controller whether the system satisfies an island criterion, if the island criterion is satisfied, switching a main power supply to a V/f operation mode from a PQ operation mode, implementing step 5) after the PCC switch is disconnected, and otherwise, returning to step 1); and ) determining whether the system operates normally: if the system is abnormal, immediately tripping a fault circuit once detected, and restarting step 5); if the system is normal, determining whether source-load are balanced in the microgrid, and if source-load are balanced, returning to step 1); if source-load are unbalanced, calculating a power unbalance value, adjusting the storage battery output, determining whether source-load are balanced again, if source-load are balanced, returning to step 1), otherwise, carrying out low-voltage/low-frequency load shedding, and determining whether source-load are balanced again. The microgrid central controller is used for acquiring electrical quantities of the microgrid and the liaison line, wherein the electrical quantities of the microgrid and the liaison line include a current and switch positions on the liaison line, a bus voltage and a frequency of the microgrid, a current and switch positions of each micro power supply circuit, and a current and switch positions of each load circuit. The micro-grid central controller (MGCC) in step 1) can acquire analog quantities and switching quantities of multiple circuits, communicates with an energy management system (EMS) and a battery management system (BMS), and can control the switch remotely; an expert system program module is built in to receive, process and forward data in real time. The rapid measurement and control unit is installed on an incoming line of each load circuit, the rapid measurement and control unit is used for acquiring electrical information of each load circuit and providing overcurrent protection for the load circuit, and the rapid measurement and control unit is communicated with the microgrid central controller, uploads the electrical information of the load circuit to the microgrid central controller and receives remote control from the microgrid central controller. GOOSE communication is employed among the microgrid central controller, the rapid measurement and control unit and the superior system. The microgrid in step 1) includes solar photovoltaic (PV), wind turbine generation (WG) and storage battery (SB) devices; as shown in Figure 1, wind-solar hybridization can be realized to improve the economy, environmental protection and reliability of power supply. Moreover, the use of an inverter as the interface between distributed generators and storage battery systems effectively improves the flexibility and dynamic performance of the microgrid; and multiple operation modes, including the grid-connected operation mode, the island mode, a transition from the grid-connected mode to the island mode, and a transition from the island mode to the grid-connected mode, are involved. The microgrid is connected with an external power grid through a PCC point, an inverter is used as an interface between a distributed generator and a storage battery system, and the PCC point and the inverter are controlled to be disconnected and connected through a microgrid control system. the PCC point, a power supply branch circuit and a load branch circuit are disconnected and connected through a remote control module. The main power supply in step 4) is provided by a storage battery system, and the microgrid can operate in a PQ mode during the grid-connected operation to provide stable power for the microgrid; and the microgrid can operate in a V/f mode during the island mode operation to provide stable voltage and frequency support for the microgrid. The criterion for determining the balance of source-load of the microgrid in step 3) and step 5) lies in that all the power of the power supply in the system are equal to the power of the load, i.e.,
PDG -LOAD, the power value is obtained by the microgrid central controller and the rapid measurement and control unit through high-speed sampling and data capture after calculation, i.e., 64 points are sampled in each cycle, and measured values are averaged after three cycles, whereby on the basis of rapid response, the determination of the balance is ensured to be accurate. The balance adjustment in step 3) and step 5) includes the steps of: calculating an unbalanced value of power of the microgrid system, adjusting the storage battery output according to a result of the calculation, and carrying out low-voltage/low-frequency load shedding when source-load are unbalanced: classifying the load as an important load and a controllable load according to a priority of the load, preferentially tripping the controllable load, ensuring that the important load is not interrupted and the controllable load encounters fewer interruptions, until source-load are balanced. An island criterion includes three conditions, i.e., whether the main power grid is under voltage, whether the PCC switch is in a tripped position, and whether the microgrid is abnormal. The state of the microgrid can be quickly determined through the island criterion: if the main power grid is under voltage, the PPC switch is closed, and the microgrid is not abnormal, the state is determined to be normal grid-connected operation; if the main power grid is under voltage, the PCC switch is closed, and the microgrid is abnormal, fault detection should be carried out immediately and a fault circuit should be tripped once detected; if the main power grid is under voltage, the PCC switch is disconnected, and the microgrid is not abnormal, the operation to connect the microgrid to the main power grid, namely, the transition from the island mode to the grid-connected mode, is implemented; if the main power grid is under voltage, the PCC switch is disconnected, and the microgrid is abnormal, fault detection should be carried out immediately and the fault circuit should be tripped once detected, and then the operation to connect the microgrid to the main power grid, namely, the transition from the island mode to the grid-connected mode, is implemented; if the main power grid is not under voltage, the PCC switch is closed, and the microgrid is not abnormal, the island criterion is satisfied, and the PCC switch should be immediately disconnected to enter the island mode operation; if the main power grid is not under voltage, the PCC switch is closed, and the microgrid is abnormal, the island criterion is satisfied, the PCC switch should be disconnectedimmediately, fault detection should be carried out and the fault circuit should be tripped once detected; if the main power grid is not under voltage, the PCC switch is disconnected, and the microgrid is not abnormal, the state of the microgrid is ddetermined to be normal island mode operation; if the main power grid is not under voltage, the PCC switch is disconnected, and the microgrid is abnormal, fault detection should be carried out immediately and the fault circuit should be tripped once detected. In Document [3] (Guo Xian, Guo He, Cheng Haozhong, Masaud Bazargan, Liang Wuxing. MicrogridFrameworkPlanningConsidering Costs of Users Due to Power Failure[J]. Journalof Electrical Technology, 2014, 29 (8): 301-308.), typical values of costs of an entity due to power failure are provided: if the power failure duration is 20min, the costs of small industrial users due to power failure are about 140 yuan/(kW h); if the power failure duration is 60 min, the costs of small industrial users due to power failure are about 250 yuan/(kW h). If the microgrid cannot be smoothly and seamlessly switched between the operation modes, the microgrid will experience a process of stopping, starting, and gradual accessing of loads. This process lasts for about 30 min. Taking a microgrid with a capacity of 500 kW as an example, the costs after experiencing this process due to the power failure are calculated as follows: C=30+60 X 500 X 140=35000 yuan.
Claims (10)
1. A method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid,wherein including the following steps : 1) acquiring electrical quantities of a microgrid and liaison line through a microgrid central controller and a rapid measurement and control unit and receiving an instruction from a superior system to obtain a real-time operating state of the microgrid, and then implementing step 2); 2) determining whether the transition to the island mode is planned, if the transition to the island mode is planned, implementing step 3); if not, implementing step 4); 3) calculating a real-time load and a power supply output of the microgrid system, and determining whether source-load are balanced; if source-load are unbalanced, adjusting a storage battery output or tripping a controllable load, and implementing step 3) again; if source-load are balanced, disconnecting a PCC (Point of Common Coupling) switch upon arrival at a planned switching time point, and returning to implement step 1) when each distributed generator operates normally and source-load are balanced in the microgrid; 4) determining by the microgrid central controller whether the system satisfies an island criterion, if the island criterion is satisfied, switching a main power supply to a V/f operation mode from a PQ operation mode, implementing step 5) after the PCC switch is disconnected, and otherwise, returning to step 1); and ) determining whether the system operates normally: if the system is abnormal, immediately tripping a fault circuit once detected, and restarting step 5); if the system is normal, determining whether source-load are balanced in the microgrid, and if source-load are balanced, returning to step 1); if source-load are unbalanced, calculating a power unbalance value, adjusting the storage battery output, determining whether source-load are balanced again, if source-load are balanced, returning to step 1), otherwise, carrying out low-voltage/low-frequency load shedding, and determining whether source-load are balanced again.
2. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1, whereinthe microgrid central controller is used for acquiring electrical quantities of the microgrid and the liaison line, wherein the electrical quantities of the microgrid and the liaison line include a current and switch positions on the liaison line, a bus voltage and a frequency of the microgrid, a current and switch positions of each micro power supply circuit, and a current and switch positions of each load circuit.
3. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1, whereinthe rapid measurement and control unit is installed on an incoming line of each load circuit, the rapid measurement and control unit is used for acquiring electrical information of each load circuit and providing overcurrent protection for the load circuit, and the rapid measurement and control unit is communicated with the microgrid central controller, uploads the electrical information of the load circuit to the microgrid central controller and receives remote control from the microgrid central controller.
4. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1, wherein GOOSE communication is employed among the microgrid central controller, the rapid measurement and control unit and the superior system.
5. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1 or 2 or 3 or 4, whereinthe microgrid comprises a wind turbine generator, a photovoltaic cell panel and a storage battery.
6. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1, whereinthe microgrid is connected with an external power grid through a PCC point, an inverter is used as an interface between a distributed generator and a storage battery system, and the PCC point and the inverter are controlled to be disconnected and connected through a microgrid control system.
7. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 6, wherein the PCC point, a power supply branch circuit and a load branch circuit are disconnected and connected through a remote control module.
8. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1, whereinthe main power supply in step 4) is provided by a storage battery system, and the microgrid can operate in a PQ mode during the grid-connected operation to provide stable power for the microgrid; and the microgrid can operate in a V/f mode during the island mode operation to provide stable voltage and frequency support for the microgrid.
9. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1, whereinthe criterion for determining the balance of source-load of the microgrid in step 3) and step 5) lies in that all the power of the power supply in the system are equal to the power of the load, i.e., PDG =LOAD, the power value is obtained by the microgrid central controller and the rapid measurement and control unit through high-speed sampling and data capture after calculation, i.e., 64 points are sampled in each cycle, and measured values are averaged after three cycles, whereby on the basis of rapid response, the determination of the balance is ensured to be accurate.
10. The method for controlling stability of a transition from grid-connected operation to island mode operation of a microgrid as recited in claim 1, characterized in that the balance adjustment in step 3) and step 5) include the following steps: calculating an unbalanced value of power of the microgrid system, adjusting the storage battery output according to a result of the calculation, and carrying out low-voltage/low-frequency load shedding when source-load are unbalanced: classifying the load as an important load and a controllable load according to a priority of the load, the important load includinga first-level load and a second-level load, the controllable load including a third-level load, preferentially tripping the controllable load, ensuring that the important load is not interrupted and the controllable load encounters fewer interruptions, until source-load are balanced.
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| CN201810105873.7 | 2018-02-01 | ||
| CN201810105873.7A CN109842148A (en) | 2018-02-01 | 2018-02-01 | A kind of micro-grid connection turns the stable control method of isolated operation mode |
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| AU2018406527A Pending AU2018406527A1 (en) | 2018-02-01 | 2018-05-10 | Method for controlling stability when microgrid grid connection switches to island operation mode |
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| CN (1) | CN109842148A (en) |
| AU (2) | AU2018102188A4 (en) |
| WO (1) | WO2019148688A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110212583A (en) * | 2019-06-25 | 2019-09-06 | 国网山东省电力公司临沂供电公司 | The control method of Distribution Network Failure distributed generation resource off-the-line linkage |
| CN111525524B (en) * | 2020-05-13 | 2022-05-24 | 国网山西省电力公司电力科学研究院 | Relay protection method for distributed photovoltaic access power distribution network |
| CN111697619B (en) * | 2020-06-09 | 2023-07-21 | 上海交通大学 | Method and system for switching off-grid control of micro-grid inverter in unplanned manner |
| CN112186796B (en) * | 2020-09-04 | 2022-02-01 | 三峡大学 | Multi-microgrid non-planned island control method based on artificial emotion reinforcement learning |
| CN112202208B (en) * | 2020-09-24 | 2023-05-05 | 广东电网有限责任公司韶关供电局 | Ad hoc network control method and system for small hydropower micro-grid cutting machine |
| CN112350367A (en) * | 2020-10-13 | 2021-02-09 | 芜湖泰伦特能源科技有限公司 | Control method for local power grid combined power supply constructed through micro-grid |
| CN113255485B (en) * | 2021-05-13 | 2022-05-17 | 云南电网有限责任公司 | Identification method and device for grid-connected mode of hydroelectric generating set |
| CN113629654B (en) * | 2021-08-04 | 2023-09-15 | 深圳市英锐恩科技有限公司 | Power supply control method, circuit, device and readable storage medium |
| CN114063698B (en) * | 2021-10-20 | 2024-01-23 | 中航宝胜海洋工程电缆有限公司 | Main line adjusting and protecting circuit and method for constant-voltage submarine observation network |
| CN113890098A (en) * | 2021-10-22 | 2022-01-04 | 三峡大学 | Micro-grid unplanned island switching method based on artificial emotion SARSA learning |
| CN116826795B (en) * | 2023-06-01 | 2024-03-15 | 中能建储能科技(武汉)有限公司 | Energy storage power station non-planned island operation load distribution control equipment and method |
| CN116780629B (en) * | 2023-06-27 | 2024-02-20 | 武汉大学 | Smooth switching method and device for independent operation of power distribution system containing energy storage |
| CN117277403A (en) * | 2023-08-16 | 2023-12-22 | 湖北能源集团鄂州发电有限公司 | Micro-grid island control method |
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| CN102324741B (en) * | 2011-08-17 | 2013-10-16 | 国家电网公司 | Micro-power grid off-grid energy balance and control device and method |
| CN102856924B (en) * | 2012-08-29 | 2015-01-21 | 中国能源建设集团广东省电力设计研究院 | Microgrid smooth switch control method based on composite energy storage |
| CN103296699B (en) * | 2013-03-19 | 2017-11-10 | 昆明理工大学 | A kind of fast control method of the plan island with power conversion power-balance based on Wide-area Measurement Information |
| CN103595052B (en) * | 2013-10-25 | 2015-07-01 | 国家电网公司 | Method for stably controlling switchover from micro-grid connection into island state |
| CN103607045B (en) * | 2013-11-06 | 2015-05-20 | 国电南瑞科技股份有限公司 | Micro grid grid-connection to grid-off smooth switching intelligent control method based on GOOSE |
| CN103795084B (en) * | 2014-02-24 | 2015-11-18 | 国电南瑞科技股份有限公司 | The one-touch grid-connected net that leaves of micro-capacitance sensor takes over seamlessly control method |
| US10903654B2 (en) * | 2015-12-03 | 2021-01-26 | Enphase Energy, Inc. | Method and apparatus for minimizing circulating currents in microgrids |
| CN106374501B (en) * | 2016-11-17 | 2019-05-24 | 新智能源***控制有限责任公司 | A kind of micro-grid system for realizing micro battery power supply and load coulomb balance |
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2018
- 2018-02-01 CN CN201810105873.7A patent/CN109842148A/en active Pending
- 2018-05-10 AU AU2018102188A patent/AU2018102188A4/en not_active Ceased
- 2018-05-10 AU AU2018406527A patent/AU2018406527A1/en active Pending
- 2018-05-10 WO PCT/CN2018/086239 patent/WO2019148688A1/en active Application Filing
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| WO2019148688A1 (en) | 2019-08-08 |
| CN109842148A (en) | 2019-06-04 |
| AU2018406527A1 (en) | 2020-09-24 |
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