Method for automatically carrying out grid-connected and off-grid control switching between micro-grid and commercial power

Abstract

The invention provides a method for automatically carrying out grid-connected and off-grid control switching between a micro-grid and commercial power, and belongs to the technical field of electric power. The method comprises the following steps: when a control system monitors that the voltage on switching equipment accords with a set threshold value, controlling the switching equipment to be closed so as to enter a grid-connected working mode; the converter device converts alternating current generated by the wind driven generator into direct current, then converts the direct current into alternating current and accesses the mains supply; the control system adjusts the output power of the wind driven generator and the energy storage system according to the real-time condition information of the wind driven generator and the load demand and controls the energy storage equipment to be in a charging state; when the control system monitors that the voltage on the switching equipment does not conform to the set threshold value, the switching equipment is controlled to be disconnected to enter an off-grid working mode; the converter device converts alternating current generated by the wind driven generator into direct current and then converts the direct current into alternating current to be used by a load according to the current output voltage; the control device dynamically adjusts the working state of the energy storage system according to the generated power of the wind driven generator and the load demand.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electric power technology, and in particular to a method for automatically switching between a microgrid and a mains supply and performing on-grid and off-grid control. Background Art

[0002] As the global demand for renewable energy continues to grow, wind power generation, as an important form of clean energy, has received widespread attention. Traditional power systems usually rely on centralized power generation, which has problems such as high cost, low efficiency and great environmental impact in construction and operation. In order to optimize power supply, the concept of microgrids has gradually emerged, which improves energy efficiency and system flexibility by realizing distributed power generation, energy storage and load management in local areas.

[0003] In the operation of microgrids, wind turbines can effectively convert wind energy into electrical energy, but their output power is greatly affected by changes in wind speed. At the same time, in order to enhance the reliability of the system, microgrids also need to have the ability to connect to the main grid so that they can obtain supplementary power from the main grid when wind resources are insufficient.

[0004] Currently, many microgrid systems still face challenges in switching between grid-connected and off-grid operating modes. In grid-connected mode, the microgrid needs to keep pace with the mains to ensure voltage and frequency matching; in off-grid mode, it must operate independently to ensure the power demand of local loads.

[0005] Therefore, it is necessary to provide a grid-connected and off-grid control switching method that can improve the utilization rate of wind power generation and enhance the adaptability and stability of the microgrid. Summary of the invention

[0006] The embodiment of the present invention provides a method for automatically switching between a microgrid and a mains grid and between the microgrid and the mains, so as to enable a control unit to perform regular self-inspection and transmit status data to an alarm module. The alarm module analyzes the status data and water quality data to promptly detect whether there is an abnormality in the equipment status or water pollution, thereby avoiding the situation where accurate water quality data cannot be obtained due to equipment abnormality, greatly improving the accuracy of water quality data detection, and further improving the accuracy of water pollution analysis and the timeliness of sewage purification.

[0007] In a first aspect, an embodiment of the present invention provides a method for automatically switching between a microgrid and a mains grid for on-grid and off-grid control.

[0008] The microgrid comprises a wind turbine, a converter, an energy storage system, a DC bus, a load, a distribution network, a control system and a switching device; the wind turbine is provided with a wind tracking system for adjusting the angle of the blades or the position of the entire wind turbine according to the detected wind speed and wind direction; the electric energy generated by the wind turbine is connected to the DC bus after being stepped up or stepped down by the converter, and the energy storage system is connected to the DC bus; the converter converts the AC power generated by the wind turbine into DC power, and converts the DC power into AC power suitable for grid connection or use by the load, and the distribution network is connected to the converter; the control system is connected to the switching device, the control system is used to monitor the voltage on the switching device in real time, and the switching device is used to connect or disconnect the microgrid from the mains; the microgrid has a grid-connected working mode and an off-grid working mode; the method comprises:

[0009] When the control system detects that the voltage on the switching device meets the set threshold, the switching device is controlled to close to connect the microgrid with the mains, so that the microgrid is in the grid-connected working mode; the converter converts the AC power generated by the wind turbine into DC power, and then converts the DC power into AC power and connects it to the mains; the control system adjusts the output power of the wind turbine and the energy storage system according to the real-time status information of the wind turbine and the load demand; and controls the energy storage device to be in a charging state;

[0010] When the control system detects that the voltage on the switching device does not meet the set threshold, the switching device is controlled to disconnect to disconnect the microgrid from the mains, so that the microgrid is in the off-grid working mode; at this time, the converter converts the AC power generated by the wind turbine into DC power according to the current output voltage, and then converts the DC power into AC power suitable for the off-grid working mode for use by the load; the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the real-time demand of the load.

[0011] In a possible design of the first aspect, the wind tracking system includes an anemometer, a wind vane, a processor, and an actuator;

[0012] The anemometer is used to measure wind speed data, and the wind vane is used to measure wind direction data;

[0013] The processor is used to calculate the optimal angle of the blades of the wind turbine or the optimal adjustment value of the position of the entire wind turbine according to the wind speed data and the wind direction data;

[0014] The actuator is used to adjust the angle of the blade according to the optimal angle of the blade, or to adjust the direction of the turbine of the wind generator according to the optimal adjustment value, so as to control the output power of the wind generator.

[0015] In a possible design of the first aspect, the actuator includes a blade pitch system and a yaw system;

[0016] The blade pitch system is used to adjust the angle of the blades through an electric or hydraulic drive device; the yaw system is used to drive the base of the turbine to rotate through a motor so that the entire turbine faces the optimal wind direction.

[0017] In a possible design of the first aspect, the specific working process of the wind tracking system is as follows:

[0018] Collecting the wind speed data by the anemometer, and collecting the wind direction data by the wind vane;

[0019] sending the wind speed data and the wind direction data to the processor;

[0020] The processor calculates the wind speed data and the wind direction data by using a fuzzy control algorithm to obtain an optimal adjustment value of the blade angle or the position of the wind turbine generator;

[0021] The processor sends a blade angle adjustment signal to the blade pitch system, or sends a position adjustment signal to the yaw system;

[0022] The blade pitch control system adjusts the angle of the blade through an electric or hydraulic drive device according to the blade angle adjustment signal; or,

[0023] The yaw system drives the base of the turbine to rotate through a motor according to the position adjustment signal to adjust the direction of the turbine so that the turbine always faces the direction of the wind.

[0024] In a possible design of the first aspect, in the grid-connected working mode, the energy storage system is adjusted to a charging state, and the city power and the wind turbine generator supply power to the load and charge the energy storage system.

[0025] In a possible design of the first aspect, in the off-grid working mode, the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the real-time demand of the load, including:

[0026] If the power generated by the wind turbine is greater than the real-time demand of the load, adjusting the energy storage system to a charging state;

[0027] If the power generation of the wind turbine is less than the real-time demand of the load, the energy storage system is adjusted to a discharging state.

[0028] In a possible design of the first aspect, when the microgrid is in the grid-connected working mode, the converter converts the AC power generated by the wind turbine into DC power, and then converts the DC power into AC power and connects it to the mains power, including:

[0029] The alternating current generated by the wind turbine generator is converted into direct current through the rectifier module in the converter;

[0030] Converting direct current into alternating current matching the voltage of the mains electricity through an inverter in the converter;

[0031] According to the monitored current output voltage and frequency on the switching device, the output voltage of the inverter is calculated by a feedback control algorithm, so as to dynamically adjust the output voltage of the inverter according to the calculated output voltage.

[0032] In a possible design of the first aspect, when the microgrid is in the off-grid working mode, the converter converts the AC power generated by the wind turbine generator into DC power according to the current output voltage and then converts the DC power into AC power suitable for the off-grid working mode for use by the load, including:

[0033] The alternating current generated by the wind turbine generator is converted into direct current through the rectifier module in the converter;

[0034] According to the real-time demand of the load, the DC power is converted into AC power suitable for the off-grid working mode by the inverter in the converter;

[0035] The output voltage and frequency of the inverter are dynamically adjusted according to the real-time demand of the load.

[0036] In the above scheme, by setting a wind tracking system for the wind turbine, the wind turbine can always face the direction of the wind, thereby improving the power generation efficiency of the wind turbine and being able to adapt to different wind conditions. At the same time, when the control system monitors that the voltage on the switching device meets the set threshold, the switching device is controlled to close to enter the grid-connected working mode; the converter converts the AC power generated by the wind turbine into DC power and then into AC power and connects to the mains; the control system adjusts the output power of the wind turbine and the energy storage system according to the real-time status information of the wind turbine and the load demand and controls the energy storage device to be in the charging state; when the control system monitors that the voltage on the switching device does not meet the set threshold, the switching device is controlled to disconnect to enter the off-grid working mode; the converter converts the AC power generated by the wind turbine into DC power and then into AC power for load use according to the current output voltage; the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the load demand, further improving the adaptability and stability of the microgrid. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the embodiments of the present invention.

[0038] Figure 1 is a structural schematic diagram of a microgrid provided by an embodiment of the present invention;

[0039] Figure 2 is a schematic structural diagram of a wind tracking system 200 provided in an embodiment of the present invention;

[0040] Figure 3 is a flowchart of a working process of a wind tracking system in a microgrid provided by an embodiment of the present invention;

[0041] Figure 4 A flow chart of a method for automatically switching between a microgrid and a mains grid for on-grid and off-grid control is provided in an embodiment of the present invention.

[0042] The above drawings have shown specific embodiments of the present invention, which will be described in more detail below. These drawings and text descriptions are not intended to limit the scope of the embodiments of the present invention in any way, but to illustrate the concepts of the embodiments of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of the present invention are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data need to comply with the relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0045] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the case where there is no conflict between the embodiments, the following embodiments and the features in the embodiments can be combined with each other. In addition, the step sequence in the following method embodiments is only an example and not a strict limitation.

[0046] First, some terms involved in the embodiments of the present invention are explained.

[0047] Microgrid: A microgrid is a small, localized power system that can operate independently in both grid-connected and off-grid modes. A microgrid is usually composed of multiple distributed energy resources, loads, energy storage systems, and control systems, and has the ability to autonomously control and manage.

[0048] Mains electricity: also known as the public power grid or alternating current, refers to the standardized electricity supply provided by power companies, usually used for various electricity needs such as residential, commercial and industrial.

[0049] Grid-connected working mode: refers to the working mode in which the microgrid is connected to the mains and can realize two-way power exchange.

[0050] Off-grid working mode: refers to the mode in which the microgrid is disconnected from the mains and operates independently. In the off-grid mode, the microgrid needs to independently meet its load requirements.

[0051] Wind turbine: A device that converts wind energy into electrical energy.

[0052] Load: refers to the equipment or devices that consume electricity.

[0053] As the global demand for renewable energy continues to increase, wind power generation, as an important form of clean energy, has received widespread attention. Traditional power systems usually rely on centralized power generation, which has problems such as high cost, low efficiency and great environmental impact during construction and operation. In order to optimize power supply and solve these problems, the concept of microgrids has gradually emerged. Microgrids improve energy efficiency and system flexibility by realizing distributed power generation, energy storage and load management in local areas.

[0054] In the operation of microgrids, wind turbines can effectively convert wind energy into electrical energy. However, their output power is greatly affected by changes in wind speed, showing intermittency and uncertainty. In addition, in order to enhance the reliability of the system, microgrids need to be able to connect to the main grid so that they can obtain supplementary power from the main grid when wind resources are insufficient and sell excess power to the main grid when there is excess power.

[0055] Currently, many microgrid systems still face many challenges in switching between grid-connected and off-grid working modes. In grid-connected mode, microgrids need to keep pace with the mains to ensure the consistency of voltage and frequency to achieve seamless power transmission. In off-grid mode, microgrids must operate independently to ensure that the power demand of local loads is met while ensuring the stability and reliability of the system.

[0056] Therefore, it is particularly important to develop a grid-connected and off-grid control switching method that can improve the utilization rate of wind power generation and enhance the adaptability and stability of microgrids. This method not only needs to be able to intelligently manage the output of wind turbines, but also needs to be able to dynamically adjust the system's operating mode according to real-time wind speed changes and load demand. Through advanced control strategies and technical means, smooth switching between microgrids and city power can be achieved, ensuring that microgrids can operate efficiently and reliably whether they are connected to the grid or off-grid, thereby promoting the effective utilization and development of renewable energy.

[0057] Based on this, the embodiment of the present invention proposes a method for automatically switching between a microgrid and a mains supply and controlling the connection and disconnection of the microgrid. By setting a wind tracking system for the wind turbine, the wind turbine can always face the direction of the wind, thereby improving the power generation efficiency of the wind turbine and being able to adapt to different wind conditions. At the same time, when the control system monitors that the voltage on the switching device meets the set threshold, the switching device is controlled to close to enter the grid-connected working mode; the converter converts the AC power generated by the wind turbine into DC power and then into AC power and connects to the mains; the control system adjusts the output power of the wind turbine and the energy storage system according to the real-time status information of the wind turbine and the load demand and controls the energy storage device to be in a charging state; when the control system monitors that the voltage on the switching device does not meet the set threshold, the switching device is controlled to disconnect to enter the off-grid working mode; the converter converts the AC power generated by the wind turbine into DC power and then into AC power for use by the load according to the current output voltage; the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the load demand, further improving the adaptability and stability of the microgrid.

[0058] It should be understood herein that any number of elements in the drawings is for illustration rather than limitation, and any naming is only for distinction rather than having any limiting meaning.

[0059] The following is an introduction to the microgrid in the method for automatically switching between a microgrid and a mains grid through on-grid and off-grid control provided by an embodiment of the present invention.

[0060] Figure 1 Schematic diagram of a microgrid structure provided by an embodiment of the present invention. Figure 1 As shown, the system includes: the microgrid 100 includes a wind turbine 110, a converter 120, an energy storage system 130, a DC bus 140, a load 150, a distribution network 160, a control system 170 and a switching device 180.

[0061] Among them, the wind turbine 110 is provided with a wind tracking system 200, which is used to adjust the angle of the blades or the position of the entire wind turbine 110 according to the detected wind speed and wind direction. The electric energy generated by the wind turbine 110 is connected to the DC bus 140 after being stepped up or down by the converter 120, and the energy storage system 130 is also connected to the DC bus 140.

[0062] The converter 120 converts the AC power generated by the wind turbine 110 into DC power, and converts the DC power into AC power suitable for grid connection or for use by the load 150. The distribution network 160 is connected to the converter 120. The control system 170 is connected to the switching device 180. The control system 170 is used to monitor the voltage on the switching device 180 in real time. The switching device 180 is used to connect or disconnect the microgrid from the mains. The microgrid has a grid-connected working mode and an off-grid working mode.

[0063] Specifically, the electric energy generated by the wind turbine 110 is converted into direct current through the rectifier module in the converter 120, and then connected to the DC bus 140 after adjusting the voltage through the DC / DC converter. The energy storage system 130 is connected to the DC bus 140 through a bidirectional DC / DC converter, and is charged or discharged according to actual needs. The DC power on the DC bus 140 is converted into AC power through the inverter in the converter 120, and is provided to the load 150 for use or connected to the distribution network 160 for power distribution or energy exchange with the mains.

[0064] In the grid-connected working mode of the microgrid, the distribution network 160 is connected to the mains through an inverter to exchange energy, that is, the electric energy in the microgrid flows to the mains, or the electric energy of the mains flows to the microgrid. In the off-grid working mode of the microgrid, the distribution network 160 operates independently and only serves the load 150 inside the microgrid.

[0065] In actual use, in order to ensure the stability and reliability of the microgrid, when the mains fails, such as when the voltage on the switching device 180 is detected to be out of the normal range, the frequency fluctuates too much, there is a power outage, or the protection mechanism is activated, the microgrid will be triggered to switch from the grid-connected working mode to the off-grid working mode to ensure that the equipment in the microgrid is not damaged. Among them, the protection mechanism can be, for example, overcurrent protection, short circuit protection, etc.

[0066] When the mains power returns to normal, that is, when the voltage and frequency on the switching device 180 are monitored to be within the normal range, the microgrid can be reconnected to the mains power and switched to the grid-connected working mode. In some cases, the microgrid can also trigger the switch to the grid-connected working mode to obtain additional electricity from the mains power when the internal load increases and the electricity generated by the energy storage system 130 and the wind turbine 110 is insufficient to meet the demand. In other cases, when too much energy is generated inside the microgrid and the excess electricity needs to be transmitted to the mains power, the working mode switch can also be triggered, switching from the off-grid working mode to the grid-connected working mode.

[0067] For example, assuming that the normal voltage range is 180V~242V, if the voltage of the AC power on the switching device 180 is monitored to be lower than 180V or higher than 242V, the microgrid switches to the off-grid working mode. If the voltage of the AC power on the switching device 180 is monitored to be between 180V and 242V, the microgrid can switch to the grid-connected working mode.

[0068] In this way, by monitoring the voltage and / or frequency on the switching device 180, the electric energy of the energy storage system 130 and the wind turbine 110 and the demand of the load 150 are used as trigger conditions for switching the working mode, so that the microgrid can smoothly switch between different working modes, ensuring that the system maintains efficient operation while meeting the power demand of the load 150.

[0069] In order to make the wind turbine 110 always face the direction of the wind to adapt to different wind conditions and improve the power generation efficiency of the wind turbine 110, in an embodiment of the present invention, a wind tracking system 200 is designed for the wind turbine 110. The wind tracking system 200 provided in an embodiment of the present invention is described below with reference to the accompanying drawings.

[0070] Figure 2 2 is a schematic diagram of the structure of a wind tracking system 200 provided in an embodiment of the present invention. Figure 2 As shown, the wind tracking system 200 may include: an anemometer 210, a wind vane 220, a processor 230 and an actuator 240. The anemometer 210 is used to measure wind speed data, and the wind vane 220 is used to measure wind direction data; the processor 230 is used to calculate the optimal angle of the blades of the wind turbine 110 or the optimal adjustment value of the position of the entire wind turbine 110 according to the wind speed data and the wind direction data; the actuator 240 is used to adjust the angle of the blades according to the optimal angle of the blades, or adjust the direction of the turbine of the wind turbine 110 according to the optimal adjustment value, so as to control the output power of the wind turbine 110.

[0071] The blades of the wind turbine 110 are devices for capturing wind energy. Therefore, by adjusting the blades to an optimal angle, it can be ensured that the wind turbine 110 can efficiently convert wind energy into mechanical energy, and the generator can convert mechanical energy into electrical energy.

[0072] Specifically, the actuator 240 may include a blade pitch system 241 and a yaw system 242. The blade pitch system 241 is used to adjust the angle of the blades through an electric or hydraulic drive device; the yaw system 242 is used to drive the base of the turbine to rotate through a motor so that the entire turbine faces the best wind direction.

[0073] The microgrid provided by the embodiment of the present invention is introduced above. The following describes the working process of the wind tracking system 200 in the microgrid.

[0074] Figure 3 1 is a flowchart of the working process of a wind tracking system in a microgrid provided by an embodiment of the present invention. Figure 3 As shown, the workflow may include the following steps:

[0075] Step 300, collecting wind speed data through an anemometer, and collecting wind direction data through a wind vane.

[0076] Step 310, sending wind speed data and wind direction data to a processor.

[0077] Step 320: The processor calculates the wind speed data and wind direction data through a fuzzy control algorithm to obtain an optimal adjustment value of the blade angle or the position of the wind turbine.

[0078] In step 330, the processor sends a blade angle adjustment signal to the blade pitch system, or sends a position adjustment signal to the yaw system. When sending a blade angle adjustment signal, the process goes to step 340, and when sending a position adjustment signal, the process goes to step 350.

[0079] Step 340: The blade pitch control system adjusts the angle of the blade through an electric or hydraulic drive device according to the blade angle adjustment signal.

[0080] Step 350 , the yaw system drives the base of the turbine to rotate through a motor according to the position adjustment signal to adjust the direction of the turbine so that the turbine always faces the direction of the wind.

[0081] The anemometer may be a cup anemometer or an ultrasonic anemometer, etc., installed on the top of the wind turbine to obtain accurate wind speed data. The wind vane may be a pointer-type wind vane or a magnetic compass-type wind vane, also installed on the top of the wind turbine to obtain accurate wind direction data. The types of anemometers and wind vanes listed above are only examples. In actual use, the specific types of anemometers and wind vanes can be determined according to needs, and the most suitable installation location can be determined according to the determined types.

[0082] After the anemometer collects wind speed data and the wind vane collects wind direction data, they are sent to the processor, which calculates the optimal angle of the wind turbine blades or the optimal adjustment value of the wind turbine position based on the wind speed data and wind direction data.

[0083] In the embodiment of the present invention, the processor may be an embedded controller, such as a programmable logic controller (PLC) or an ARM microcontroller. The embodiment of the present invention does not specifically limit the type of processor.

[0084] The processor can use a fuzzy control algorithm to calculate the wind speed data and wind direction data to obtain the optimal angle or optimal adjustment value of the blade. The fuzzy control algorithm mainly converts real-time data into fuzzy values, and then calculates the relevant actual adjustment value, that is, the optimal angle or optimal adjustment value of the blade described in this article.

[0085] The implementation process is:

[0086] 1) Fuzzification: used to convert wind speed data and wind direction data into fuzzy values. For example, wind speed is divided into "low, medium, and high", and wind direction is divided into "tailwind, headwind, and crosswind".

[0087] 2) Establish a fuzzy logic rule base: associate fuzzy values ​​with adjustment values.

[0088] 3) Reasoning of fuzzy calculation: According to the fuzzy value of the input variable and the fuzzy logic rules of the fuzzy logic rule base, calculation reasoning is performed to obtain the fuzzy value of the output variable.

[0089] 4) Solve the fuzzy value and convert it into the corresponding actual value, that is, the optimal angle or optimal adjustment value of the blade.

[0090] Specifically, assume that the wind speed data is V and the wind direction data is D. Perform fuzzy processing on the wind speed data and wind direction data respectively. The wind speed data is fuzzified into: VL-very low; L-low; M-medium; H-high; VH-very high. The wind direction data is fuzzified into: NW-northwest; NE-northeast; E-east; SE-southeast; S-south; SW-southwest; W-west; NW-northwest.

[0091] The fuzzy logic rules are defined as follows: if the wind speed is very high (VH) and the wind direction is westerly (W), the blade angle should decrease (Δθ<0) and the turbine should turn westward (ΔD>0); if the wind speed is moderate (M) and the wind direction is eastward (E), the blade angle should increase (Δθ>0) and the turbine should turn eastward (ΔD<0); if the wind speed is very low (L) and the wind direction is northward (N), the blade angle should remain unchanged (Δθ=0) and the turbine should not turn (ΔD=0).

[0092] Afterwards, according to the actual values ​​of the wind speed data and the wind direction data and the defined rules, the inference calculation is performed. For example, assuming that the wind speed data is 10m / s, which is medium (M), and the wind direction data is due east, which is east wind (E), then according to the defined rules, it is inferred that the wind speed is medium and the wind direction is east wind, the blade angle should be increased, and the turbine should rotate eastward. After obtaining the fuzzy output, the fuzzy output is defuzzified, that is, the fuzzy output is converted into an actual value to obtain the optimal adjustment value of the specific blade optimal angle and position. Among them, the defuzzification method includes the center of gravity method, the maximum membership method, etc. After obtaining the optimal adjustment value of the blade optimal angle and / or position, the processor can send a blade angle adjustment signal to the blade pitch system so that the blade pitch system adjusts the angle of the blade according to the blade angle adjustment signal through an electric or hydraulic drive device. Alternatively, the processor sends a position adjustment signal to the yaw system so that the yaw system drives the base of the turbine to rotate through a motor according to the position adjustment signal to adjust the direction of the turbine so that the turbine always faces the direction of the wind.

[0093] In actual applications, after the actuator adjustment is completed, the wind tracking system can also measure the wind speed data and wind direction data again based on the feedback mechanism to check whether the expected effect has been achieved. If there is a deviation, the optimal adjustment value of the blade's optimal angle or position is recalculated based on the re-measured wind speed data and wind direction data.

[0094] Specifically, it is possible to establish monitoring of key indicators, such as output power, efficiency wind speed, wind direction, and other data, as well as blade angle and real-time status of the generator. Then, a monitoring loop is established to compare the actual output of the wind turbine with the expected output to obtain an error signal. The error signal is then input into the above-mentioned processor, and the error signal is used to adjust the parameters of the processor, such as the membership function, rule weight, or the fuzzy logic rule base itself.

[0095] Based on the solution provided by the above embodiment of the present invention, a wind tracking system is set for the wind turbine, the anemometer collects wind speed data and the wind vane collects wind direction data, and the processor can determine the optimal blade angle or the optimal adjustment value of the turbine position based on the wind speed data and wind direction data collected in real time. Thereafter, the blade angle or the direction of the turbine is adjusted according to the optimal blade angle or the optimal adjustment value of the turbine position by controlling the actuator, so that the wind turbine can always face the direction of the wind, thereby improving the power generation efficiency of the wind turbine and being able to adapt to different wind conditions.

[0096] The above describes the microgrid provided by the embodiment of the present invention. The following describes the method for automatically switching the microgrid and the mains power for on-grid and off-grid control provided by the embodiment of the present invention.

[0097] Figure 4A flow chart of a method for automatically switching between a microgrid and a mains grid for on-grid and off-grid control provided by an embodiment of the present invention. Figure 4 As shown, the method comprises the following steps:

[0098] Step 400, when the control system detects that the voltage on the switching device meets the set threshold, the switching device is controlled to close to connect the microgrid with the mains, so that the microgrid is in a grid-connected working mode; the converter converts the AC power generated by the wind turbine into DC power, and then converts the DC power into AC power and connects it to the mains; the control system adjusts the output power of the wind turbine and the energy storage system according to the real-time status information of the wind turbine and the load demand; and controls the energy storage device to be in a charging state.

[0099] Step 420, when the control system detects that the voltage on the switching device does not meet the set threshold, the switching device is controlled to disconnect to disconnect the microgrid from the mains, so that the microgrid is in an off-grid working mode; at this time, the converter converts the AC power generated by the wind turbine into DC power according to the current output voltage and then converts the DC power into AC power suitable for the off-grid working mode for use by the load; the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the real-time demand of the load.

[0100] The voltage threshold may be, for example, 180 V to 242 V, that is, it should not be lower than 180 V or higher than 242 V. When the control system detects that the voltage on the switching device is between 180 V and 242 V, it is determined that the mains power is normal, and the switching device of the microgrid may be controlled to close to access the mains power, so that the microgrid is in a grid-connected working mode.

[0101] In the grid-connected working mode, the electric energy required by the load can be provided by the mains. At this time, the energy storage system can be adjusted to the charging state, and the mains and wind turbines can power the load and charge the energy storage system.

[0102] Specifically, the wind tracking system adjusts the direction of the wind turbine facing the wind according to the measured wind speed data and wind direction data, so that the wind turbine generates AC power with the best output power. Considering that changes in wind speed may cause unstable output power, in practical applications, it is also necessary to increase power regulation to ensure stable power output. For example, the maximum power point tracking algorithm is used to monitor the output of the wind turbine in real time, and the operating parameters are adjusted to capture the maximum available power. The AC power generated by the wind turbine is input to the converter, which then converts the AC power generated by the wind turbine into DC power, and then inverts it back into AC power suitable for the mains, thereby achieving a smooth switch from off-grid working mode to grid-connected working mode.

[0103] Among them, in the grid-connected working mode, the process in which the converter converts the AC power generated by the wind turbine into DC power, and then converts the DC power into AC power and connects it to the mains power may include: converting the AC power generated by the wind turbine into DC power through the rectifier module in the converter; converting the DC power into AC power matching the voltage of the mains power through the inverter in the converter; calculating the output voltage of the inverter through a feedback control algorithm based on the current output voltage and frequency on the monitored switching device, so as to dynamically adjust the output voltage of the inverter based on the calculated output voltage.

[0104] In one example, the switching device may be a grid-connected or off-grid switch. The control device may monitor the current output voltage and frequency of the grid-connected or off-grid switch in real time through a voltage sensor and a frequency sensor, and perform low-pass filtering on the collected output voltage and frequency to eliminate noise interference.

[0105] In the embodiment of the present invention, a proportional-integral-derivative (PID) controller is used to calculate the target output voltage U of the inverter. output Specifically, assuming the target output voltage is U target , the current voltage is U current .

[0106] Among them, K P is the proportional gain, the voltage error e V =U target -U current , K i is the integral gain, K d is the differential gain, ∫e V dt is the integral term of the error, is the rate of change of error.

[0107] After the target output voltage of the inverter is calculated according to the above formula, the calculated target output voltage is transmitted to the control module of the inverter so that the control module of the inverter adjusts the output voltage of the inverter through a pulse width modulation (PWM) signal. At the same time, the control device will continue to monitor the output voltage of the on-grid and off-grid switch, and adjust the output voltage of the inverter in real time according to the feedback.

[0108] Through the above scheme, the output voltage of the inverter can be dynamically adjusted through the feedback control algorithm according to the current output voltage and frequency on the switching device. This method can ensure that the voltage and frequency output by the inverter always remain within the predetermined range, thereby improving the stability and reliability of the microgrid system.

[0109] In the off-grid working mode, the control device can also dynamically adjust the working state of the energy storage system. Specifically, the control device dynamically adjusts the working state of the energy storage system according to the power generation of the wind turbine and the real-time demand of the load. If the power generation of the wind turbine is greater than the real-time demand of the load, it means that there is excess electric energy. At this time, the energy storage system is adjusted to the charging state, and the excess electric energy is used to charge the energy storage system. If the power generation of the wind turbine is less than the real-time demand of the load, it means that the current wind turbine cannot meet the load's demand for electric energy, and the energy storage system needs to be adjusted to the discharging state, and the energy storage system will perform supplementary power generation.

[0110] Among them, when the microgrid is in the off-grid working mode, the converter device converts the AC power generated by the wind turbine into DC power according to the current output voltage, and then converts the DC power into AC power suitable for the off-grid working mode for use by the load. The process includes: converting the AC power generated by the wind turbine into DC power through the rectifier module in the converter device; converting the DC point into AC power suitable for the off-grid working mode through the inverter in the converter device according to the real-time demand of the load; and dynamically adjusting the output voltage and frequency of the inverter according to the real-time demand of the load.

[0111] Specifically, after the inverter converts DC power into AC power according to the real-time demand of the load, the PID controller is used to dynamically adjust the output voltage and frequency of the inverter. Similarly, the formula To calculate the target output voltage; where K P is the proportional gain, the voltage error e V =U target -U current , K i is the integral gain, K d is the differential gain, ∫e V dt is the integral term of the voltage error, is the rate of change of voltage error.

[0112] In addition, through the formula Calculate the target output frequency; where K′ P is the proportional gain, the frequency error e F =f target -f current , K′ i is the integral gain, K′ d is the differential gain, ∫e F dt is the integral term of the frequency error, is the rate of change of frequency error.

[0113] Through the above method, the microgrid can realize the process of converting the AC power generated by the wind turbine into AC power suitable for the off-grid working mode through the converter device in the off-grid working mode. This method can ensure that the voltage and frequency output by the inverter are always kept within the predetermined range, thereby improving the stability and reliability of the microgrid system.

[0114] In one possible implementation, the microgrid of the present application may also have a pre-off-grid working mode, which is mainly used to respond to mains failures, power outage instructions issued by grid operators, economic considerations (mains electricity prices are higher than microgrid power generation costs), system protection and other user needs.

[0115] When the above trigger conditions are met, the pre-off-grid working mode can control the wind turbine to reduce power generation; reduce the load; control the energy storage system to discharge or charge to maintain the internal ionization balance of the microgrid; adjust the bidirectional inverter to reduce energy exchange with the mains; and send notifications of the pre-off-grid working mode to operators and internal systems.

[0116] Furthermore, when the pre-off-grid working mode is converted to the off-grid working mode, it may include the following actions: 1) synchronization: confirm that the inverter output is close to zero and the voltage and frequency inside the microgrid are stable; 2) disconnection: operate the smart switch to physically disconnect from the mains; 3) complete the off-grid working mode switching.

[0117] On the contrary, when the pre-off-grid working mode is converted to the grid-connected working mode, it can include the following actions: 1) Monitoring: monitor the status of the mains power, adjust the output of the wind turbine generator, and achieve synchronization with the mains power through the inverter; 2) Synchronization check: confirm that the voltage, frequency, and phase deviation between the microgrid and the mains power are within the allowable range; 3) Grid-connected operation: issue a grid-connected command, close the smart switch, and reconnect the microgrid to the mains power; 4) Complete the switching of the grid-connected working mode.

[0118] Through these steps, the microgrid can smoothly transition from the pre-off-grid working mode to the off-grid working mode or the grid-connected working mode to ensure the continuity of power supply and system stability. The key to the pre-off-grid working mode is to gradually reduce the energy exchange with the mains to avoid damage to the grid or microgrid equipment caused by sudden power outages.

[0119] Based on the solution provided by the above embodiments of the present invention, when the control system monitors that the voltage on the switching device meets the set threshold, the switching device is controlled to close to enter the grid-connected working mode; the converter converts the AC power generated by the wind turbine into DC power and then into AC power and connects it to the mains; the control system adjusts the output power of the wind turbine and the energy storage system according to the real-time status information of the wind turbine and the load demand and controls the energy storage device to be in a charging state; when the control system monitors that the voltage on the switching device does not meet the set threshold, the switching device is controlled to disconnect to enter the off-grid working mode; the converter converts the AC power generated by the wind turbine into DC power and then into AC power for use by the load according to the current output voltage; the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the load demand, thereby further improving the adaptability and stability of the microgrid.

[0120] Those skilled in the art will readily appreciate other implementations of the embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The embodiments of the present invention are intended to cover any variations, uses, or adaptations of the embodiments of the present invention that follow the general principles of the embodiments of the present invention and include common knowledge or customary technical means in the art that are not disclosed in the embodiments of the present invention. The specification and embodiments are to be regarded as exemplary only, and the true scope and spirit of the embodiments of the present invention are indicated by the claims.

[0121] It should be understood that the embodiments of the present invention are not limited to the precise structures described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the embodiments of the present invention is limited only by the appended claims.

Claims

1. A method for automatically switching between a microgrid and a mains grid, characterized in that: The microgrid includes a wind turbine, a converter, an energy storage system, a DC bus, a load, a distribution network, a control system and a switching device; the wind turbine is provided with a wind tracking system for adjusting the angle of the blades or the position of the entire wind turbine according to the detected wind speed and wind direction; the electric energy generated by the wind turbine is connected to the DC bus after being stepped up or down by the converter, and the energy storage system is connected to the DC bus; the converter converts the AC power generated by the wind turbine into DC power, and converts the DC power into AC power suitable for grid connection or use by the load, and the distribution network is connected to the converter; the control system is connected to the switching device, and the control system is used to monitor the voltage on the switching device in real time, and the switching device is used to connect or disconnect the microgrid from the city power; The microgrid has a grid-connected working mode and an off-grid working mode; the method comprises: When the control system detects that the voltage on the switching device meets the set threshold, the switching device is controlled to close to connect the microgrid with the mains, so that the microgrid is in the grid-connected working mode; the converter converts the AC power generated by the wind turbine into DC power, and then converts the DC power into AC power suitable for grid connection and connects it to the mains; the control system adjusts the output power of the wind turbine and the energy storage system according to the real-time status information of the wind turbine and the load demand; and controls the energy storage device to be in a charging state; When the control system detects that the voltage on the switching device does not meet the set threshold, the switching device is controlled to disconnect to disconnect the microgrid from the mains, so that the microgrid is in the off-grid working mode; at this time, the converter converts the AC power generated by the wind turbine into DC power according to the current output voltage, and then converts the DC power into AC power suitable for the off-grid working mode for use by the load; the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the real-time demand of the load.

2. The method according to claim 1, characterized in that The wind tracking system includes an anemometer, a wind vane, a processor and an actuator; The anemometer is used to measure wind speed data, and the wind vane is used to measure wind direction data; The processor is used to calculate the optimal angle of the blades of the wind turbine or the optimal adjustment value of the position of the entire wind turbine according to the wind speed data and the wind direction data; The actuator is used to adjust the angle of the blade according to the optimal angle of the blade, or to adjust the direction of the turbine of the wind generator according to the optimal adjustment value, so as to control the output power of the wind generator.

3. The method according to claim 2, characterized in that The actuator includes a blade pitch system and a yaw system; The blade pitch system is used to adjust the angle of the blades through an electric or hydraulic drive device; the yaw system is used to drive the base of the turbine to rotate through a motor so that the entire turbine faces the optimal wind direction.

4. The method according to claim 3, characterized in that The specific working process of the wind tracking system is as follows: Collecting the wind speed data by the anemometer, and collecting the wind direction data by the wind vane; sending the wind speed data and the wind direction data to the processor; The processor calculates the wind speed data and the wind direction data by using a fuzzy control algorithm to obtain an optimal adjustment value of the blade angle or the position of the wind turbine generator; The processor sends a blade angle adjustment signal to the blade pitch system, or sends a position adjustment signal to the yaw system; The blade pitch control system adjusts the angle of the blade through an electric or hydraulic drive device according to the blade angle adjustment signal; or, The yaw system drives the base of the turbine to rotate through a motor according to the position adjustment signal to adjust the direction of the turbine so that the turbine always faces the direction of the wind.

5. The method according to claim 1, characterized in that In the grid-connected working mode, the energy storage system is adjusted to a charging state, and the mains power and the wind turbine generator supply power to the load and charge the energy storage system.

6. The method according to claim 1, characterized in that In the off-grid working mode, the control device dynamically adjusts the working state of the energy storage system according to the power generation power of the wind turbine and the real-time demand of the load, including: If the power generated by the wind turbine is greater than the real-time demand of the load, adjusting the energy storage system to a charging state; If the power generation of the wind turbine is less than the real-time demand of the load, the energy storage system is adjusted to a discharging state.

7. The method according to claim 1, characterized in that When the microgrid is in the grid-connected working mode, the converter converts the AC power generated by the wind turbine into DC power, and then converts the DC power into AC power and connects it to the mains power, including: The alternating current generated by the wind turbine generator is converted into direct current through the rectifier module in the converter; Converting direct current into alternating current matching the voltage of the mains electricity through an inverter in the converter; According to the monitored current output voltage and frequency on the switching device, the output voltage of the inverter is calculated by a feedback control algorithm, so as to dynamically adjust the output voltage of the inverter according to the calculated output voltage.

8. The method according to claim 1, characterized in that When the microgrid is in the off-grid working mode, the converter device converts the AC power generated by the wind turbine into DC power according to the current output voltage and then converts the DC power into AC power suitable for the off-grid working mode for use by the load, including: The alternating current generated by the wind turbine generator is converted into direct current through the rectifier module in the converter; According to the real-time demand of the load, the DC power is converted into AC power suitable for the off-grid working mode by the inverter in the converter; The output voltage and frequency of the inverter are dynamically adjusted according to the real-time demand of the load.

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