Micro-grid and frequency modulation method and device thereof

Abstract

The application discloses a micro-grid and a frequency modulation method and device thereof. The micro-grid comprises multi-stage hydroelectric generating units, and in each stage of the hydroelectric generating units, the installed capacity of a preceding stage of hydroelectric generating unit is greater than that of a following stage of hydroelectric generating unit. The frequency modulation method of the micro-grid comprises: when the micro-grid is in a non-steady state working condition, adjusting the output power of each stage of hydroelectric generating unit in sequence, and acquiring the frequency of an alternating current signal output by the micro-grid in real time; when the frequency of the alternating current signal is within a preset frequency range, controlling the micro-grid to enter a steady state working condition. By using the above technical scheme, when the micro-grid is in the non-steady state working condition, the risk of damage of the hydroelectric device caused by frequent tripping is reduced, and the safety of frequency regulation of the micro-grid is improved; the frequency of the alternating current signal can be accurately regulated, so that the frequency of the alternating current signal can reach the preset frequency range, and the reliability of frequency regulation of the micro-grid is improved.

Description

Technical Field

[0001] This invention relates to the field of microgrid frequency regulation technology, and in particular to a microgrid and its frequency regulation method and device. Background Technology

[0002] Hydropower generation has advantages such as being green, pollution-free, and renewable. As a result, there are more and more small hydropower plants that generate electricity using hydropower, and they are widely distributed. Most of these small hydropower plants do not operate alone; they are connected to nearby power grids or form a microgrid.

[0003] Currently, when a microgrid composed of multiple small hydropower units is in operation, each small hydropower unit operates at its maximum power, meaning all operating units run at maximum output. When frequency regulation is required, if the frequency is too high, one of the small hydropower units is disconnected from the microgrid, thus reducing the microgrid's output power and lowering the frequency. If the frequency is too low, more small hydropower units are put into operation to increase the microgrid's output power, thereby raising the frequency.

[0004] As a result, each small hydropower unit operates at its maximum output power. Frequency regulation only considers two methods: switching off and starting up. Sometimes, it is difficult to adjust the frequency to around 50Hz. Furthermore, there is no good way to deal with frequency fluctuations during periods or in areas with frequent load fluctuations. Each unit operates at maximum power with very little adjustment margin. Failures may occur due to frequent switching on or off of small hydropower units, making it difficult to guarantee the stability and safety of the microgrid operation. Summary of the Invention

[0005] This invention provides a microgrid and its frequency regulation method and device to improve the stability and security of microgrid operation.

[0006] According to one aspect of the present invention, a frequency regulation method for a microgrid is provided, the microgrid comprising multiple stages of hydropower units, wherein the installed capacity of the preceding stage of hydropower units is greater than the installed capacity of the following stage of hydropower units, the frequency regulation method for the microgrid comprising:

[0007] When the microgrid is in an unsteady operating state, the output power of each level of the hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time.

[0008] When the frequency of the AC signal is within a preset frequency range, the microgrid is controlled to enter a steady-state operating state.

[0009] Optionally, the output power of each stage of the hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time, including:

[0010] The output power of the current hydropower unit is continuously increased by a preset power increment, and the frequency of the AC signal output by the microgrid is acquired in real time.

[0011] When the output power of the current stage hydropower unit is equal to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, then the next stage hydropower unit is the current stage hydropower unit, and the process returns to the step of continuously increasing the output power of the current stage hydropower unit by a preset power increment.

[0012] Optionally, the output power of each stage of the hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time, further comprising:

[0013] Before continuously increasing the output power of the current stage hydropower unit to the first power threshold by the preset power increment, if the frequency of the AC signal is within the preset frequency range, then the increase in the output power of the current stage hydropower unit shall be stopped.

[0014] Optional, also includes:

[0015] When the output power of each level of the hydropower unit increases to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, the first power threshold is adjusted by a preset threshold increment, and the process returns to the step of continuously increasing the output power of the current level hydropower unit by a preset power increment and acquiring the frequency of the AC signal output by the microgrid in real time.

[0016] Optional, also includes:

[0017] When the microgrid is in a steady-state operating state, the frequency of the AC signal output by the microgrid is acquired in real time;

[0018] If the frequency of the AC signal is not within the preset frequency range, the output power of each stage of the hydropower unit is adjusted sequentially according to the adjustment cycle.

[0019] Optionally, the output power of each stage of the hydropower unit is adjusted sequentially according to the adjustment cycle, including:

[0020] The output power of each stage of the hydropower units is adjusted sequentially, starting from the first hydropower unit in the current adjustment cycle. When the current adjustment cycle is the Nth adjustment cycle, the first hydropower unit in the current adjustment cycle is the next-stage hydropower unit after the last hydropower unit adjusted in the previous adjustment cycle. When the current adjustment cycle is the first adjustment cycle, the first hydropower unit in the current adjustment cycle is the next-stage hydropower unit after the first-stage hydropower unit or the last hydropower unit adjusted when the microgrid is in a non-steady-state operating state. Wherein, N is an integer greater than or equal to 2.

[0021] Optionally, starting with the first hydropower unit in the current regulation cycle, the output power of each stage of the hydropower units is adjusted sequentially, including:

[0022] The first hydropower unit in the current adjustment cycle is continuously adjusted with a preset power adjustment amount, and the frequency of the AC signal is continuously determined to be within the preset range.

[0023] When the frequency of the AC signal is not within the preset range and the output power of the first hydropower unit reaches the second power threshold, the next-level hydropower unit of the first hydropower unit is taken as the hydropower unit to be adjusted.

[0024] The output power of the hydropower unit to be adjusted is continuously adjusted by the preset power adjustment amount, and the frequency of the AC signal is continuously determined to be within the preset range.

[0025] When the frequency of the AC signal is not within the preset range and the output power of the hydropower unit to be adjusted reaches the second power threshold, the next-level hydropower unit to be adjusted is taken as the next hydropower unit to be adjusted, and the process returns to the step of continuously adjusting the output power of the hydropower unit to be adjusted with the preset power adjustment amount until the frequency of the AC signal is within the preset range.

[0026] Optional, also includes:

[0027] When the output power of each level of the hydropower unit reaches the second power threshold, if the frequency of the AC signal is not within the preset range, the second power threshold is adjusted by the preset threshold adjustment amount.

[0028] The hydropower unit to be adjusted is the next level hydropower unit after the first-stage hydropower unit or the last hydropower unit in the current adjustment cycle. The process is then repeated to continuously adjust the output power of the hydropower unit to be adjusted by the preset power adjustment amount until the frequency of the AC signal is within the preset range.

[0029] According to another aspect of the present invention, a frequency regulation device for a microgrid is provided, the microgrid comprising multiple stages of hydropower units, wherein the installed capacity of the preceding stage of the hydropower units is greater than the installed capacity of the following stage of the hydropower units, and the frequency regulation device for the microgrid comprises:

[0030] The power regulation module is used to sequentially adjust the output power of each stage of the hydropower unit when the microgrid is in an unsteady operating state, and to acquire the frequency of the AC signal output by the microgrid in real time.

[0031] The steady-state control module is used to control the microgrid to enter a steady-state operating state when the frequency of the AC signal is within a preset frequency range.

[0032] According to another aspect of the present invention, a microgrid is provided, comprising: a multi-stage hydropower unit, wherein the installed capacity of the preceding stage hydropower unit is greater than the installed capacity of the subsequent stage hydropower unit; wherein the first stage hydropower unit has the largest installed capacity among the stages of the hydropower unit.

[0033] The first-stage hydropower unit is communicatively connected to the other stages of the hydropower unit; the first-stage hydropower unit includes the frequency regulation device of the microgrid described above, and the frequency regulation device of the microgrid is capable of executing the frequency regulation method of the microgrid described in any embodiment of the present invention.

[0034] The technical solution of this invention, when the microgrid is in a non-steady-state operating state, sequentially adjusts the output power of each level of hydropower unit, starting with the hydropower unit with the largest installed capacity, and adjusts the output power of each level of hydropower unit until the frequency of the AC signal output by the microgrid is within a preset range. This avoids directly performing simple generator switching when the frequency of the AC signal output by the microgrid fluctuates significantly, thus preventing damage to the small hydropower devices in the microgrid. It reduces the risk of damage to hydropower devices caused by frequent generator switching and improves the safety of frequency regulation in the microgrid. While sequentially adjusting the output power of each level of hydropower unit, the frequency of the AC signal output by the microgrid is also acquired in real time, allowing for precise control of the AC signal frequency to reach the preset frequency range, thereby improving the reliability of frequency regulation in the microgrid.

[0035] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A flowchart illustrating a frequency regulation method for a microgrid provided in Embodiment 1 of the present invention;

[0038] Figure 2 This is a flowchart of a frequency regulation method for a microgrid provided in Embodiment 2 of the present invention;

[0039] Figure 3 This is a flowchart of a frequency regulation method for a microgrid provided in Embodiment 3 of the present invention;

[0040] Figure 4 This is a flowchart of a frequency regulation method for a microgrid provided in Embodiment 4 of the present invention;

[0041] Figure 5 A flowchart of a frequency regulation method for a microgrid provided in Embodiment 5 of the present invention;

[0042] Figure 6 This is a flowchart of a frequency regulation method for a microgrid provided in Embodiment Six of the present invention;

[0043] Figure 7 A flowchart illustrating a frequency regulation method for a microgrid provided in Embodiment 7 of the present invention;

[0044] Figure 8 This is a schematic diagram of the structure of a frequency modulation device for a microgrid provided in Embodiment 8 of the present invention;

[0045] Figure 9 This is a schematic diagram of the structure of a frequency modulation device for a microgrid provided in Embodiment 9 of the present invention. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] Example 1

[0049] Figure 1 This is a flowchart of a frequency regulation method for a microgrid provided in Embodiment 1 of the present invention. This embodiment can regulate the output frequency of a microgrid composed of multiple small hydropower devices. These small hydropower devices can be combined to form multiple hydropower units, and these multiple hydropower units can be arranged in sequence to form a multi-stage hydropower unit. The microgrid includes multiple stages of hydropower units, and in each stage of the hydropower unit, the installed capacity of the preceding stage is greater than the installed capacity of the following stage. This frequency regulation method can be executed by a frequency regulation device of the microgrid, which can be implemented in hardware and / or software, and can be configured in a certain stage of the hydropower unit of the microgrid. Figure 1 As shown, the frequency modulation method includes:

[0050] S1001. When the microgrid is in an unsteady operating state, the output power of each level of hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time.

[0051] A microgrid refers to a small substation composed of multiple hydropower units. Each hydropower unit includes at least one hydroelectric device, and its installed capacity refers to the sum of the installed capacities of all its smaller hydroelectric devices. The hydropower units are ordered by their installed capacity, with the largest being the first-stage unit, followed by the second-stage, third-stage, and so on. The output power of a hydropower unit is the sum of the active power output by all its smaller hydroelectric devices. The output power of a microgrid is the sum of the output power of all its hydropower units within the microgrid. When the output power of a microgrid meets the power demand of the local electrical load, the microgrid and the local electrical load reach a state of equilibrium, and the frequency of the AC signal output by the microgrid will remain within a certain range, such as [49.8Hz, 50.2Hz]. When the power demand of the local electrical load becomes too large or too small in a short period of time, the output power of the microgrid differs greatly from the power demand of the local electrical load. The output power of the microgrid cannot meet or exceeds the power demand of the local electrical load, and the microgrid and the local electrical load cannot maintain an equilibrium. At this time, the frequency of the AC signal output by the microgrid will change significantly, and the microgrid is in a non-steady-state operating state.

[0052] Specifically, when a microgrid is operating in a non-steady-state state, the frequency of its output AC signal will fluctuate significantly. By adjusting the water flow rate of each stage of the hydropower unit sequentially, starting from the first-stage unit, the output power of the hydropower unit can be adjusted, thereby regulating the output power of the microgrid. Simultaneously, the frequency information of the microgrid's output AC signal is received in real time to detect whether the frequency has returned to normal, i.e., whether it has returned to the frequency range required for the microgrid to maintain a balance with the local electrical load.

[0053] S1002. When the frequency of the AC signal is within the preset frequency range, control the microgrid to enter a steady-state working state.

[0054] The preset frequency range refers to the frequency range when the microgrid and local power load are in a balanced state, for example, [49.8Hz, 50.2Hz]. When the power demand of the local power load is basically stable or changes slowly, the output power of the microgrid can basically maintain a balance with the power demand of the local power load, that is, the output power of the microgrid basically meets the power demand of the local power load. At this time, the frequency of the AC signal output by the microgrid will generally be within the preset frequency range, and there may be small fluctuations, slightly larger or smaller. The microgrid is in a steady-state operating state. The frequency regulation method when the microgrid is in a steady-state operating state is different from the frequency regulation method when the microgrid is in a non-steady-state operating state.

[0055] Specifically, when the frequency of the AC signal output by the microgrid is within the preset frequency range, it means that the frequency of the AC signal has recovered to the frequency range where the output power of the microgrid and the demand power of the local power load are in balance. The microgrid can basically maintain a balance with the local power load, that is, the output power of the microgrid basically meets the demand power of the local power load. At this time, the frequency of the AC signal output by the microgrid will not change significantly, and the microgrid is controlled to enter a steady-state operating state. That is, the frequency regulation method of the microgrid can be changed from a non-steady-state operating state to a steady-state operating state.

[0056] For example, at 8:00 AM, there is a sudden surge in residential or industrial electricity consumption, resulting in a significant increase in local power demand within a short period. The microgrid's output power cannot meet this demand, leading to a substantial decrease in the frequency of the microgrid's output AC signal, placing the microgrid in a non-steady-state operating condition. By sequentially adjusting the water flow of each stage of the hydropower unit, starting from the first stage, the output power of each unit is adjusted, thereby regulating the microgrid's output power. This reduces the gap between the microgrid's output power and the local power demand, gradually increasing the frequency of the microgrid's output AC signal. While increasing the microgrid's output power, the frequency of the output AC signal is monitored in real-time until it reaches a frequency range where the microgrid's output power and the local power demand are balanced, falling within a preset frequency range. Once the AC signal frequency is within the preset range, the microgrid has transitioned from a non-steady-state to a steady-state operating condition. In other words, the microgrid's frequency regulation method can transition from a non-steady-state to a steady-state operating condition, and the frequency regulation work during the non-steady-state operation is complete.

[0057] This invention, when the microgrid is in a non-steady-state operating state, sequentially adjusts the output power of each level of hydropower unit, starting with the hydropower unit with the largest installed capacity, and adjusts the output power of each level of hydropower unit until the frequency of the AC signal output by the microgrid is within a preset range. This avoids simply switching off the hydropower units when the frequency of the AC signal output by the microgrid fluctuates significantly, thus preventing damage to the hydropower equipment in the microgrid. It reduces the risk of damage to hydropower equipment caused by frequent switching off and improves the safety of frequency regulation in the microgrid. While sequentially adjusting the output power of each level of hydropower unit, the frequency of the AC signal output by the microgrid is also acquired in real time, allowing for precise control of the AC signal frequency to reach the preset frequency range, thereby improving the reliability of frequency regulation in the microgrid.

[0058] Example 2

[0059] Figure 2This is a flowchart of a microgrid frequency regulation method provided in Embodiment 2 of the present invention. Compared with the above embodiments, this embodiment provides a specific method for sequentially adjusting the output power of each stage of the hydropower unit. Figure 2 As shown, the method includes:

[0060] S2001. When the microgrid is in an unsteady state, the output power of the current hydropower unit is continuously increased by a preset power increment, and the frequency of the AC signal output by the microgrid is obtained in real time.

[0061] S2002. Before continuously increasing the output power of the current stage hydropower unit to the first power threshold by a preset power increment, if the frequency of the AC signal is within the preset frequency range, then stop increasing the output power of the current stage hydropower unit.

[0062] S2003. When the output power of the current stage hydropower unit is equal to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, then the next stage hydropower unit is the current stage hydropower unit. Return to execute S2001.

[0063] S2004. When the frequency of the AC signal is within the preset frequency range, control the microgrid to enter a steady-state operating state.

[0064] In this context, "current-level hydropower unit" refers to a hydropower unit in a state of adjusting its output power, and is not limited to a single level of hydropower unit. Adjusting the current-level hydropower unit can improve the frequency of the AC signal output by the microgrid, and may even directly restore the AC signal frequency to a preset frequency range. The preset power increment can be an increase in the output power of the hydropower unit, such as an increase in the valve flow rate. The preset power increments for each level of hydropower unit can be the same or different; this embodiment of the invention does not specifically limit this. The first power threshold refers to a certain threshold percentage of the maximum output power of the hydropower unit. For example, the first power threshold can be 70%, 80%, 85%, or 90% of the maximum output power of the hydropower unit.

[0065] To facilitate control of the operating status of each small hydropower unit within a hydropower generator set, while continuously increasing the output power of the current-stage hydropower generator set by a preset power increment, the valve flow rate of each small hydropower unit within the current-stage hydropower generator set can be continuously increased by an increment corresponding to the installed capacity of each small hydropower unit. This ensures that the output power of each small hydropower unit within the current-stage hydropower generator set increases synchronously. The sum of the valve flow rate increments corresponding to the installed capacity of each small hydropower unit is the valve flow rate increment of the current-stage hydropower generator set. The valve flow rate increments of each stage of the hydropower generator set can be the same or different. For example, by continuously increasing the valve flow rate of each small hydropower unit within the current-stage hydropower generator set by an increment corresponding to the installed capacity of each small hydropower unit, the output power of each small hydropower unit within the current-stage hydropower generator set can be continuously increased in units of 5% of its maximum output power, ensuring that the operating status of each small hydropower unit within the current-stage hydropower generator set is identical.

[0066] For example, when the demand for local electricity load increases significantly in a short period of time, and the microgrid is in a non-steady-state operating state, starting from the first-stage hydropower unit, the output power of the hydropower unit is adjusted. At this time, the first-stage hydropower unit is the current stage hydropower unit. By adjusting the valve flow rate of the first-stage hydropower unit by increasing the valve flow rate of the first-stage hydropower unit, the output power of the first-stage hydropower unit can be continuously increased in units of 5% of its maximum output power, thereby adjusting the output power of the microgrid. This reduces the gap between the output power of the microgrid and the demand for local electricity load, and gradually increases the frequency of the AC signal output by the microgrid.

[0067] While increasing the output power of the microgrid, the frequency of the AC signal output by the microgrid is monitored in real time. If the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz] before the output power of the first-stage hydropower unit increases to 80% of its maximum output power, it indicates that adjusting the output power of the first-stage hydropower unit alone can meet the incremental demand of the local power load, and the adjustment of the output power of the first-stage hydropower unit is stopped. The frequency regulation work of the microgrid in the non-steady-state operation state has been completed. If the frequency of the AC signal is still not within the range of [49.8Hz, 50.2Hz] when the output power of the first-stage hydropower unit increases to 80% of its maximum output power, it indicates that adjusting the output power of the first-stage hydropower unit alone is insufficient to meet the incremental demand of the local power load. Therefore, the output power of the second-stage hydropower unit can be adjusted.

[0068] When adjusting the output power of the second-stage hydropower unit, which is the current-stage hydropower unit, the valve flow rate of the second-stage hydropower unit is adjusted by increasing the valve flow rate of the second-stage hydropower unit to increase the output power of the second-stage hydropower unit and further increase the output power of the microgrid. Simultaneously, the frequency of the AC signal output by the microgrid is detected. If the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz] before the output power of the second-stage hydropower unit increases to 80% of its maximum output power, it indicates that adjusting the output power of the first-stage and second-stage hydropower units alone can meet the incremental demand of the local power load. Adjusting the output power of the second-stage hydropower unit is then stopped, and the frequency regulation work in the microgrid's unsteady-state operation is complete. If the frequency of the AC signal is still not within the range of [49.8Hz, 50.2Hz] when the output power of the second-stage hydropower unit increases to 80% of its maximum output power, it indicates that adjusting the output power of the first-stage and second-stage hydropower units alone is insufficient to meet the incremental demand of the local power load. Therefore, the output power of the third-stage hydropower unit can be adjusted; the third-stage hydropower unit is the current-stage hydropower unit. If the valve flow rate of the third-stage hydropower unit is adjusted by increasing the valve flow rate of the third-stage hydropower unit, and the AC signal frequency is still not within the range of [49.8Hz, 50.2Hz] when the output power of the third-stage hydropower unit increases to 80% of its maximum output power, the output power of the fourth-stage hydropower unit can be adjusted, and so on, until the AC signal frequency is within the range of [49.8Hz, 50.2Hz]. At this point, the increase in the output power of the current-stage hydropower unit is stopped, and the frequency regulation work when the microgrid is in a non-steady-state operating state is completed.

[0069] This invention, through sequential adjustment of the output power of each stage of the hydropower unit, when the output power of the current stage hydropower unit reaches a first power threshold, uses the next stage hydropower unit as the current hydropower unit and adjusts the output power of the next stage hydropower unit. This ensures that each stage of the hydropower unit does not operate at its maximum output power, and each hydropower unit still has a certain adjustment margin to cope with minor fluctuations in local power load. Moreover, it prevents each stage of the hydropower unit from always operating at its maximum output power, thus improving the heating phenomenon of small hydropower devices and protecting the small hydropower devices in each hydropower unit.

[0070] Example 3

[0071] Figure 3 This is a flowchart of a microgrid frequency regulation method provided in Embodiment 3 of the present invention. Compared with the above embodiments, this embodiment adds a specific step regarding the situation where the frequency of the AC signal is still not within the preset frequency range when the output power of each level of hydropower unit increases to a first power threshold. Figure 3 As shown, the method includes:

[0072] S3001. When the microgrid is in an unsteady state, the output power of the current hydropower unit is continuously increased by a preset power increment, and the frequency of the AC signal output by the microgrid is obtained in real time.

[0073] S3002. Before continuously increasing the output power of the current stage hydropower unit to the first power threshold by a preset power increment, if the frequency of the AC signal is within the preset frequency range, then stop increasing the output power of the current stage hydropower unit.

[0074] S3003. When the output power of the current stage hydropower unit is equal to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, then the next stage hydropower unit is the current stage hydropower unit. Return to execute S3001.

[0075] S3004. When the output power of each level of hydropower unit increases to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, the first power threshold is adjusted by the preset threshold increment. Return to execute S3001.

[0076] S3005. When the frequency of the AC signal is within the preset frequency range, control the microgrid to enter a steady-state operating state.

[0077] The preset threshold increment is the increment of the first power threshold. For example, the first power threshold can be increased from 70% to 80% of the maximum output power of the current stage hydropower unit, or from 80% to 85% of the maximum output power of the current stage hydropower unit, etc.

[0078] For example, when the microgrid is in a non-steady-state operating state, starting from the first-stage hydropower unit, the output power of the hydropower unit is continuously increased to 80% of its maximum output power. At the same time, the frequency of the AC signal output by the microgrid is acquired in real time. If the frequency of the AC signal is not within the range of [49.8Hz, 50.2Hz], the output power of the next-stage hydropower unit is adjusted until the output power of the last-stage hydropower unit is adjusted to 80% of its maximum output power, or the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz]. If, after adjusting the output power of all hydropower units to 80% of their maximum output power, the frequency of the AC signal is still not within the range of [49.8Hz, 50.2Hz], then the first power threshold is increased from 80% to 85% of the maximum output power of the current stage hydropower unit. Then, starting from the first stage hydropower unit, the output power of the hydropower units is continuously increased to 85% of their maximum output power. At the same time, the frequency of the AC signal output by the microgrid is acquired in real time. If the frequency of the AC signal is not within the range of [49.8Hz, 50.2Hz], the output power of the next stage hydropower unit is adjusted until the output power of the last stage hydropower unit is adjusted to 85% of its maximum output power, or the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz]. If the frequency of the AC signal is still not within the range of [49.8Hz, 50.2Hz] after adjusting the output power of all hydropower units to 85% of their maximum output power, the first power threshold will be increased from 85% to 90% of the maximum output power of the current hydropower unit. Then the output power of each level of hydropower unit will be adjusted in turn, and the frequency of the AC signal output by the microgrid will be obtained in real time.

[0079] The embodiments of the present invention improve the output power of the microgrid in non-steady-state conditions by increasing the first power threshold when the output power of each level of hydropower unit is increased to the first power threshold and the frequency of the AC signal is not within the preset frequency range. This makes the invention highly practical.

[0080] Example 4

[0081] Figure 4 This is a flowchart of a frequency regulation method for a microgrid provided in Embodiment 4 of the present invention. Compared with the above embodiments, this embodiment adds a frequency regulation method when the microgrid is in a steady state. Figure 4 As shown, the method includes:

[0082] S4001. When the microgrid is in an unsteady state, adjust the output power of each level of hydropower unit in sequence and obtain the frequency of the AC signal output by the microgrid in real time.

[0083] S4002. When the frequency of the AC signal is within the preset frequency range, control the microgrid to enter a steady-state operating state.

[0084] S4003. When the microgrid is in steady-state operation, the frequency of the AC signal output by the microgrid is acquired in real time.

[0085] S4004. If the frequency of the AC signal is not within the preset frequency range, adjust the output power of each level of hydropower unit in sequence according to the adjustment cycle.

[0086] The regulation period refers to the frequency regulation time of each level of hydropower unit when the microgrid is in steady-state operation. This embodiment of the invention does not specifically limit the length of the frequency regulation time.

[0087] For example, even after the microgrid enters a steady-state operating state, the local electricity load remains fluctuating, and the power demand of the local electricity load will continuously change slightly. The frequency of the AC signal output by the microgrid can be acquired in real time, and then adjusted according to the frequency regulation time of each stage of the hydropower unit when the frequency exceeds the preset frequency range. For instance, the first hour after the microgrid enters a steady-state operating state is the frequency regulation time of the first-stage hydropower unit. By adjusting the output power of the first hydropower unit, the frequency of the AC signal is kept within the preset frequency range. When the frequency of the AC signal output by the microgrid is higher than 50.2Hz, it indicates that the output power of the microgrid is greater than the power demand of the local electrical load. Therefore, the water flow of the valves of the small hydroelectric devices in the first-stage hydroelectric unit can be reduced, i.e., the output power of the first-stage hydroelectric unit can be reduced, so that the output power of the microgrid and the power demand of the local electrical load can be rebalanced, and the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz]. When the frequency of the AC signal output by the microgrid is lower than 49.8Hz, it indicates that the output power of the microgrid is less than the power demand of the local electrical load. Therefore, the water flow of the valves of the small hydroelectric devices in the first-stage hydroelectric unit can be increased, i.e., the output power of the first-stage hydroelectric unit can be increased, so that the output power of the microgrid and the power demand of the local electrical load can be rebalanced, and the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz]. It should be noted that, within the first hour after the microgrid enters steady-state operation, when the frequency of the AC signal fluctuates, only the output power of the first-stage hydropower unit is adjusted, while the output power of the other stages remains unchanged; within the second hour after the microgrid enters steady-state operation, when the frequency of the AC signal fluctuates, only the output power of the second-stage hydropower unit is adjusted, while the output power of the other stages remains unchanged; within the third hour after the microgrid enters steady-state operation, when the frequency of the AC signal fluctuates, only the output power of the third-stage hydropower unit is adjusted, while the output power of the other stages remains unchanged, and so on.

[0088] In this embodiment of the invention, when the microgrid is in steady-state operation and the frequency of the AC signal is not within the preset frequency range, the output power of each level of hydropower unit is adjusted sequentially according to the adjustment cycle. This allows each level of hydropower unit to only be responsible for frequency improvement during its own adjustment period. That is, the water flow rate of the valves of the small hydropower devices of each level of hydropower unit is adjusted only during the adjustment period of that level of hydropower unit. The water flow rate of the valves of the small hydropower devices of hydropower units outside their adjustment period does not need to be changed. This allows each level of hydropower unit to take turns undertaking the frequency improvement task, which can effectively avoid the problem of frequent adjustment of the output power of the same hydropower unit causing easy damage to the small hydropower devices. It can extend the service life of the small hydropower devices. Furthermore, by adjusting the water flow rate of the valves of the small hydropower devices to improve the frequency, the adjustment is more flexible and the frequency control is more accurate.

[0089] Example 5

[0090] Figure 5 This is a flowchart of a frequency regulation method for a microgrid provided in Embodiment 5 of the present invention. Compared with the above embodiments, this embodiment adds a frequency regulation method when the microgrid is in a steady state. Figure 5 As shown, the method includes:

[0091] S5001. When the microgrid is in an unsteady operating state, the output power of each level of hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time.

[0092] S5002. When the frequency of the AC signal is within the preset frequency range, control the microgrid to enter a steady-state working state.

[0093] S5003. When the microgrid is in steady-state operation, the frequency of the AC signal output by the microgrid is acquired in real time.

[0094] S5004. If the frequency of the AC signal is not within the preset frequency range, adjust the output power of each level of hydropower unit sequentially, starting from the first hydropower unit in the current adjustment cycle.

[0095] The current regulation cycle refers to the regulation cycle in which the power grid is in a steady-state operating state and the corresponding hydropower unit is being regulated. When the current regulation cycle is the Nth regulation cycle, the first hydropower unit in the current regulation cycle is the next-level hydropower unit of the last hydropower unit regulated in the previous regulation cycle; when the current regulation cycle is the first regulation cycle, the first hydropower unit in the current regulation cycle is the next-level hydropower unit of the first-level hydropower unit or the last hydropower unit regulated when the microgrid is in a non-steady-state operating state; where N is an integer greater than or equal to 2.

[0096] For example, each regulation cycle can adjust the output power of one or more hydropower units to avoid failing to rebalance the microgrid's output power with the local load demand by adjusting only one hydropower unit. The first frequency regulation cycle after the microgrid enters steady-state operation does not necessarily start with the first-stage hydropower unit. It can also be the next stage hydropower unit after the last hydropower unit regulated when the microgrid was in a non-steady-state operation. For example, if the last hydropower unit regulated when the microgrid was in a non-steady-state operation was the 14th stage hydropower unit, then the first frequency regulation cycle after the microgrid enters steady-state operation can start with either the first-stage or the 15th stage hydropower unit. The valve flow rate of each stage hydropower unit is adjusted sequentially to regulate its output power, so that the microgrid's output power is rebalanced with the local load demand, keeping the AC signal frequency within the range of [49.8Hz, 50.2Hz]. If N is 5, in the 5th frequency regulation cycle after the microgrid enters steady-state operation, the first hydropower unit in the current regulation cycle is the next level hydropower unit after the last hydropower unit regulated in the 4th regulation cycle. In this way, the same level hydropower unit can be regulated in different regulation cycles, the regulation frequency of the hydropower unit can be reduced, and the life of the hydropower unit can be extended.

[0097] When the microgrid is in a steady-state operation, the frequency of the AC signal is not within the preset frequency range. By adjusting the output power of each level of hydropower unit sequentially starting from the first hydropower unit in the current adjustment cycle, this invention takes into account the special situation where the local power load fluctuates greatly during the current adjustment cycle, which may result in the hydropower unit performing the frequency improvement task being unable to continue adjustment. This increases the application scope of actual operation and is also conducive to improving the stability and coping ability of the microgrid.

[0098] Example 6

[0099] Figure 6 This is a flowchart of a microgrid frequency regulation method provided in Embodiment Six of the present invention. Compared with the above embodiments, this embodiment provides a specific method for sequentially adjusting the output power of each level of hydropower unit starting from the first hydropower unit in the current regulation cycle. Figure 6 As shown, the method includes:

[0100] S6001. When the microgrid is in an unsteady operating state, the output power of each level of hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time.

[0101] S6002. When the frequency of the AC signal is within the preset frequency range, control the microgrid to enter a steady-state operating state.

[0102] S6003. When the microgrid is in steady-state operation, the frequency of the AC signal output by the microgrid is acquired in real time.

[0103] S6004. If the frequency of the AC signal is not within the preset frequency range, the first hydropower unit of the current adjustment cycle shall be continuously adjusted with the preset power adjustment amount, and the frequency of the AC signal shall be continuously judged to be within the preset range.

[0104] S6005. When the frequency of the AC signal is not within the preset range and the output power of the first hydropower unit reaches the second power threshold, the next-level hydropower unit of the first hydropower unit shall be used as the hydropower unit to be regulated.

[0105] S6006. Continuously adjust the output power of the hydropower unit to be adjusted with a preset power adjustment amount, and continuously determine whether the frequency of the AC signal is within the preset range.

[0106] S6007. When the frequency of the AC signal is not within the preset range and the output power of the hydropower unit to be adjusted reaches the second power threshold, the next-level hydropower unit to be adjusted is selected as the next hydropower unit to be adjusted. Return to execute S6006.

[0107] S6008. When the frequency of the AC signal is within the preset range, stop adjusting the output power of the hydropower unit to be adjusted.

[0108] The preset power adjustment amount can be a change in valve flow rate or other parameters that can alter the output power of the hydropower unit. The preset power adjustment amounts for each level of the hydropower unit can be the same or different; this embodiment of the invention does not impose specific limitations on this. The second power threshold refers to the upper / lower limit of the output power adjustment of the hydropower unit when the microgrid is in a steady-state operating state. For example, the second power threshold includes the upper limit of the output power adjustment of the hydropower unit when the microgrid is in a steady-state operating state and the lower limit of the output power adjustment of the hydropower unit when the microgrid is in a steady-state operating state, which are respectively the maximum output power of the hydropower unit and 20% of the maximum output power.

[0109] For example, if the output power of the first hydropower unit in the current regulation cycle has increased to its maximum output power but still fails to rebalance the microgrid's output power with the local power load demand (i.e., the AC signal frequency is still less than 49.8Hz), then the output power of more hydropower units needs to be increased to bring the AC signal frequency into the range of [49.8Hz, 50.2Hz]. Assuming the first hydropower unit in the current regulation cycle is the 6th stage, the output power of the 7th stage hydropower unit is continuously increased by a preset power regulation amount until the AC signal frequency reaches the range of [49.8Hz, 50.2Hz]. If the output power of the 7th stage hydropower unit has increased to its maximum output power but still fails to bring the AC signal frequency to 49.8Hz, the output power of the 8th stage hydropower unit is continuously increased by a preset power regulation amount, and so on, until the AC signal frequency reaches the range of [49.8Hz, 50.2Hz].

[0110] For example, if the output power of the first hydropower unit in the current regulation cycle has been reduced to 20% of its maximum output power but still fails to rebalance the microgrid's output power with the local power load demand (i.e., the AC signal frequency is still greater than 50.2Hz), then the output power of more hydropower units needs to be reduced to bring the AC signal frequency into the range of [49.8Hz, 50.2Hz]. Assuming the first hydropower unit in the current regulation cycle is the 6th stage, the output power of the 7th stage hydropower unit is continuously reduced by a preset power regulation amount until the AC signal frequency reaches the range of [49.8Hz, 50.2Hz]. If the output power of the 7th stage hydropower unit has been reduced to 20% of its maximum output power but still fails to bring the AC signal frequency to 50.2Hz, then the output power of the 8th stage hydropower unit is continuously reduced by a preset power regulation amount, and so on, until the AC signal frequency reaches the range of [49.8Hz, 50.2Hz].

[0111] In this embodiment of the invention, when the frequency of the AC signal is not within a preset range and the output power of the first hydropower unit or the hydropower unit to be adjusted in the current adjustment cycle reaches a second power threshold, the output power of the next-level hydropower unit is continuously adjusted by a preset power adjustment amount. This allows for continued adjustment of the output power of the next-level hydropower unit even when adjusting the output power of the first hydropower unit or the hydropower unit to be adjusted fails to bring the frequency of the AC signal within the preset frequency range. This expands the practical application scope and also helps improve the stability and coping capabilities of the microgrid. Furthermore, by setting a second power threshold, the output power of the hydropower unit is prevented from exceeding the maximum output power or dropping to zero, avoiding damage caused by overload and preventing the hydropower unit from operating in a shutdown state. This improves the operating efficiency of the unit and reduces adjustment time.

[0112] Example 7

[0113] Figure 7 This is a flowchart of a microgrid frequency regulation method provided in Embodiment 7 of the present invention. Compared with the above embodiments, this embodiment adds a specific step regarding the situation where the frequency of the AC signal is still not within the preset frequency range when the output power of each level of hydropower unit reaches the second power threshold. Figure 7 As shown, the method includes:

[0114] S7001. When the microgrid is in an unsteady state, the output power of each level of hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time.

[0115] S7002. When the frequency of the AC signal is within the preset frequency range, control the microgrid to enter a steady-state working state.

[0116] S7003. When the microgrid is in steady-state operation, the frequency of the AC signal output by the microgrid is acquired in real time.

[0117] S7004. If the frequency of the AC signal is not within the preset frequency range, the first hydropower unit of the current adjustment cycle shall be continuously adjusted with the preset power adjustment amount, and the frequency of the AC signal shall be continuously judged to be within the preset range.

[0118] S7005. When the frequency of the AC signal is not within the preset range and the output power of the first hydropower unit reaches the second power threshold, the next-level hydropower unit of the first hydropower unit shall be used as the hydropower unit to be regulated.

[0119] S7006: Continuously adjust the output power of the hydropower unit to be adjusted with a preset power adjustment amount, and continuously determine whether the frequency of the AC signal is within the preset range.

[0120] S7007. When the frequency of the AC signal is not within the preset range and the output power of the hydropower unit to be adjusted reaches the second power threshold, the next-level hydropower unit to be adjusted is selected as the next hydropower unit to be adjusted. Return to execute S7006.

[0121] S7008. When the output power of each level of hydropower unit reaches the second power threshold, if the frequency of the AC signal is not within the preset range, the second power threshold shall be adjusted by the preset threshold adjustment amount.

[0122] S7009. Select the first-stage hydropower unit or the next-stage hydropower unit after the last hydropower unit in the current regulation cycle as the hydropower unit to be regulated. Return to execute S7006.

[0123] S7010. When the frequency of the AC signal is within the preset range, stop adjusting the output power of the hydropower unit to be adjusted.

[0124] Among them, the preset threshold adjustment amount adjustment is to change the amount of change of the second power threshold. For example, the lower limit of the output power adjustment of the hydropower unit when the microgrid is in steady state can be changed from 20% of the original maximum output power to 15% of the maximum output power.

[0125] For example, when the microgrid is in a non-steady-state operating state, starting from the first hydropower unit in the current regulation cycle (e.g., the 6th hydropower unit), the output power of the hydropower unit is continuously reduced to 20% of its maximum output power by a preset power regulation amount, while continuously judging whether the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz]. If the frequency of the AC signal is still greater than 50.2Hz, the output power of the next stage hydropower unit is adjusted until the output power of all hydropower units (i.e., from the 6th stage hydropower unit to the last stage hydropower unit, and then from the last stage hydropower unit to the 1st stage hydropower unit to the 5th stage hydropower unit) is reduced to 20% of its maximum output power by a preset power regulation amount, or the frequency of the AC signal is within the range of [49.8Hz, 50.2Hz]. If the AC signal frequency is still greater than 50.2Hz after reducing the output power of all hydropower units to 20% of their maximum output power, then the lower limit of the output power adjustment for hydropower units in the microgrid's steady-state operation is changed from 20% to 15% of the maximum output power. Then, starting with the first-stage hydropower unit, or the next-stage hydropower unit after the last hydropower unit in the current adjustment cycle (e.g., the 5th stage hydropower unit) (e.g., the 6th stage hydropower unit), the output power of the hydropower units is continuously reduced to 15% of their maximum output power, while continuously checking whether the AC signal frequency is within the range of [49.8Hz, 50.2Hz]. If the AC signal frequency is not within the range of [49.8Hz, 50.2Hz], the output power of the next-stage hydropower unit is reduced until the output power of all hydropower units is reduced to 15% of their maximum output power, or the AC signal frequency is within the range of [49.8Hz, 50.2Hz]. If, after reducing the output power of all hydropower units to 85% of their maximum output power, the frequency of the AC signal still falls outside the range of [49.8Hz, 50.2Hz], the second power threshold will be further adjusted. The lower limit for adjusting the output power of the hydropower units when the microgrid is in steady-state operation will be changed from 15% of the maximum output power to 10% of the maximum output power. Then, the output power of each level of hydropower unit will be reduced sequentially, and the frequency of the AC signal output by the microgrid will be acquired in real time.

[0126] In this embodiment of the invention, when the output power of each level of hydropower unit reaches the second power threshold, the frequency of the AC signal is not within the preset frequency range. By adjusting the second power threshold with the preset threshold adjustment amount, the application space in actual operation is improved, and it is also beneficial to improve the stability and coping ability of the microgrid.

[0127] Example 8

[0128] Figure 8This is a schematic diagram of a frequency regulation device for a microgrid provided in Embodiment 8 of the present invention. This embodiment can be implemented in hardware and / or software, and can be configured in a certain stage of a microgrid hydropower unit. It can execute the frequency regulation method for microgrids described in any embodiment of the present invention, and can adjust the output frequency of a microgrid composed of multiple small hydropower devices. These small hydropower devices can be combined to form multiple hydropower units, and multiple hydropower units can be arranged to form multi-stage hydropower units. The microgrid includes multi-stage hydropower units, and in each stage of hydropower units, the installed capacity of the previous stage hydropower unit is greater than the installed capacity of the next stage hydropower unit. Figure 8 As shown, the frequency modulation device 800 includes:

[0129] The power regulation module 810 is used to sequentially adjust the output power of each level of hydropower unit when the microgrid is in an unsteady operating state, and to acquire the frequency of the AC signal output by the microgrid in real time.

[0130] The steady-state control module 820 is used to control the microgrid to enter a steady-state operating state when the frequency of the AC signal is within a preset frequency range.

[0131] This invention, through a power regulation module and a steady-state control module, sequentially adjusts the output power of each hydropower unit when the microgrid is in a non-steady-state operating state. Regulation begins with the hydropower unit with the largest installed capacity, adjusting the output power of each subsequent unit. This avoids simple unit switching, reducing the risk of damage to hydropower equipment caused by frequent unit switching and improving the safety of microgrid frequency regulation. Simultaneously, while sequentially adjusting the output power of each hydropower unit, the frequency of the AC signal output by the microgrid is also acquired in real time. This allows for precise control of the AC signal frequency, ensuring it reaches a preset frequency range and improving the reliability of microgrid frequency regulation.

[0132] The frequency regulation device for microgrids provided in the embodiments of the present invention can execute the frequency regulation method for microgrids provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the method.

[0133] Example 9

[0134] Figure 9 This is a schematic diagram of the structure of a frequency regulation device for a microgrid provided in Embodiment 9 of the present invention. Figure 9 As shown, the microgrid 900 includes multiple hydropower units (920, 930, ...), and in each level of hydropower unit (910, 920, 930, ...), the installed capacity of the previous level hydropower unit is greater than the installed capacity of the next level hydropower unit; among them, the first level hydropower unit 910 has the largest installed capacity.

[0135] The first-stage hydropower unit 910 is communicatively connected to other stages of hydropower units (920, 930, ...); the first-stage hydropower unit includes a microgrid frequency regulation device 800 as described in the embodiments of the present invention, and the microgrid frequency regulation device 800 is capable of executing the microgrid frequency regulation method described in any embodiment of the present invention.

[0136] This invention fully utilizes the effective communication of micro power plants to exchange frequency regulation information, adjusts the frequency regulation information in real time according to the current operating status, and adopts a master-slave frequency regulation method, in which the first-stage hydropower unit sends and exchanges information, and coordinates the work of each level of hydropower unit to achieve the purpose of frequency regulation.

[0137] The microgrid provided in this embodiment of the invention includes a frequency regulation device for the microgrid. The frequency regulation device of the microgrid can execute the frequency regulation method of the microgrid provided in any embodiment of the invention. The microgrid has the corresponding functional modules and beneficial effects of executing the method.

[0138] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0139] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A frequency regulation method for a microgrid, characterized in that, The microgrid includes multiple levels of hydropower units, and in each level of hydropower unit, the installed capacity of the preceding level is greater than the installed capacity of the following level. The frequency regulation method of the microgrid includes: When the microgrid is in an unsteady operating state, the output power of each level of the hydropower unit is adjusted sequentially, and the frequency of the AC signal output by the microgrid is acquired in real time. When the frequency of the AC signal is within a preset frequency range, the microgrid is controlled to enter a steady-state operating state. The process includes sequentially adjusting the output power of each stage of the hydropower unit and acquiring the frequency of the AC signal output by the microgrid in real time, including: The output power of the current hydropower unit is continuously increased by a preset power increment, and the frequency of the AC signal output by the microgrid is acquired in real time. When the output power of the current stage hydropower unit is equal to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, then the next stage hydropower unit is the current stage hydropower unit, and the process returns to the step of continuously increasing the output power of the current stage hydropower unit by a preset power increment. The frequency regulation method of the microgrid further includes: when the output power of each level of the hydropower unit increases to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, the first power threshold is adjusted by a preset threshold increment, and the process returns to the step of continuously increasing the output power of the current level hydropower unit by a preset power increment, and obtaining the frequency of the AC signal output by the microgrid in real time.

2. The frequency regulation method for a microgrid according to claim 1, characterized in that, The method further includes sequentially adjusting the output power of each stage of the hydropower unit and acquiring the frequency of the AC signal output by the microgrid in real time. Before continuously increasing the output power of the current stage hydropower unit to the first power threshold by the preset power increment, if the frequency of the AC signal is within the preset frequency range, then the increase in the output power of the current stage hydropower unit shall be stopped.

3. The frequency regulation method for a microgrid according to claim 1, characterized in that, Also includes: When the microgrid is in a steady-state operating state, the frequency of the AC signal output by the microgrid is acquired in real time; If the frequency of the AC signal is not within the preset frequency range, the output power of each stage of the hydropower unit is adjusted sequentially according to the adjustment cycle.

4. The frequency regulation method for a microgrid according to claim 3, characterized in that, The output power of each stage of the hydropower unit is adjusted sequentially according to the regulation cycle, including: The output power of each stage of the hydropower units is adjusted sequentially, starting from the first hydropower unit in the current adjustment cycle. When the current adjustment cycle is the Nth adjustment cycle, the first hydropower unit in the current adjustment cycle is the next-stage hydropower unit after the last hydropower unit adjusted in the previous adjustment cycle. When the current adjustment cycle is the first adjustment cycle, the first hydropower unit in the current adjustment cycle is the next-stage hydropower unit after the first-stage hydropower unit or the last hydropower unit adjusted when the microgrid is in a non-steady-state operating state. Wherein, N is an integer greater than or equal to 2.

5. The frequency regulation method for a microgrid according to claim 4, characterized in that, Starting with the first hydropower unit in the current regulation cycle, the output power of each stage of the hydropower units is adjusted sequentially, including: The first hydropower unit in the current adjustment cycle is continuously adjusted with a preset power adjustment amount, and the frequency of the AC signal is continuously determined to be within the preset frequency range. When the frequency of the AC signal is not within the preset frequency range and the output power of the first hydropower unit reaches the second power threshold, the next-level hydropower unit of the first hydropower unit is taken as the hydropower unit to be adjusted. The output power of the hydropower unit to be adjusted is continuously adjusted by the preset power adjustment amount, and the frequency of the AC signal is continuously determined to be within the preset frequency range. When the frequency of the AC signal is not within the preset frequency range and the output power of the hydropower unit to be adjusted reaches the second power threshold, the next-level hydropower unit to be adjusted is taken as the next hydropower unit to be adjusted, and the process returns to the step of continuously adjusting the output power of the hydropower unit to be adjusted with the preset power adjustment amount until the frequency of the AC signal is within the preset frequency range.

6. The frequency regulation method for a microgrid according to claim 5, characterized in that, Also includes: When the output power of each level of the hydropower unit reaches the second power threshold, if the frequency of the AC signal is not within the preset frequency range, the second power threshold is adjusted by the preset threshold increment. The first-stage hydropower unit or the next-stage hydropower unit after the last hydropower unit in the current adjustment cycle is taken as the hydropower unit to be adjusted, and the process returns to the step of continuously adjusting the output power of the hydropower unit to be adjusted with the preset power adjustment amount until the frequency of the AC signal is within the preset frequency range.

7. A frequency regulation device for a microgrid, characterized in that, The microgrid includes multiple levels of hydropower units, and in each level of hydropower unit, the installed capacity of the preceding level is greater than the installed capacity of the following level. The frequency regulation device of the microgrid includes: The power regulation module is used to sequentially adjust the output power of each stage of the hydropower unit when the microgrid is in an unsteady operating state, and to acquire the frequency of the AC signal output by the microgrid in real time. The steady-state control module is used to control the microgrid to enter a steady-state operating state when the frequency of the AC signal is within a preset frequency range. The power threshold adjustment module is used to adjust the first power threshold by a preset threshold increment when the output power of each level of the hydropower unit increases to the first power threshold, and if the frequency of the AC signal is not within the preset frequency range, and return to the step of continuously increasing the output power of the current level hydropower unit by the preset power increment and obtaining the frequency of the AC signal output by the microgrid in real time. The power regulation module is also used to continuously increase the output power of the current stage hydropower unit by a preset power increment, and to acquire the frequency of the AC signal output by the microgrid in real time. The power regulation module is also used to, when the output power of the current stage hydropower unit is equal to the first power threshold, if the frequency of the AC signal is not within the preset frequency range, then the next stage hydropower unit is the current stage hydropower unit, and the process returns to the step of continuously increasing the output power of the current stage hydropower unit by a preset power increment.

8. A microgrid, characterized in that, include: The system comprises multi-stage hydropower units, wherein the installed capacity of the preceding stage hydropower unit is greater than that of the following stage hydropower unit; and the first stage hydropower unit has the largest installed capacity among all stages. The first-stage hydropower unit is communicatively connected to the other stages of the hydropower unit; the first-stage hydropower unit includes the frequency regulation device of the microgrid as described in claim 7, and the frequency regulation device of the microgrid is capable of executing the frequency regulation method of the microgrid as described in any one of claims 1-6.

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