A control method for water-solar-storage microgrid under weak communication conditions

Abstract

The present invention discloses a method for controlling a hydropower-photovoltaic-storage microgrid under weak communication conditions, comprising the following steps: a hydropower unit controller receives historical local load power data sent from a substation; predicts the load value for the day; installs a photovoltaic auxiliary test unit around the hydropower station, obtains the maximum power of the auxiliary test unit under the current working condition, establishes communication between the auxiliary test unit and the small hydropower station, and transmits its maximum power to the hydropower unit controller; the hydropower unit controller estimates the power generation of the photovoltaic power station in the substation based on the power generation data of the auxiliary test unit; the small hydropower station calculates and updates the current power generation reference value of the small hydropower station based on the current estimated power generation of the photovoltaic power station and the predicted local load data; the microgrid controller in the substation collects voltage, current, power and system frequency data of the microgrid system, adjusts the power balance of the microgrid system through the centralized energy storage power station and the photovoltaic power station, records the local load power data within a day, and transmits it to the hydropower unit controller.

Description

Technical Field

[0001] The present invention belongs to the field of water-photovoltaic-storage microgrid control, and in particular relates to a water-photovoltaic-storage microgrid control method under weak communication conditions. Background Art

[0002] my country's southeastern and southwestern mountainous areas are rich in hydropower resources, offering promising prospects for the development of small hydropower. Driven by the dual carbon goals, distributed photovoltaics are rapidly developing, with an increasing number of distributed power sources, such as photovoltaics and hydropower, being connected to the grid via long-distance transmission lines. However, due to their remote locations and complex terrain, power grids in mountainous areas often suffer from relatively poor power supply reliability due to long power lines and large power supply radiuses. In the event of a power outage in the upper grid, microgrid systems, relying on abundant local photovoltaic and hydropower resources, effectively guarantee power supply reliability for mountain residents.

[0003] However, small hydropower stations are often located in remote mountainous areas far from load centers, resulting in poor communication with substation equipment. To address this communication issue, researchers are currently researching microgrid control strategies, focusing on improving communication conditions and addressing weak communication scenarios. For mountainous power grids containing small hydropower stations, technologies exist to establish communication between hydropower controllers, grid-connected switches, and dispatching EMS master stations. This allows for the collection of data such as hydropower unit power. Hydropower units can also receive commands from the dispatching EMS system to regulate the start and stop of hydropower and adjust hydropower output. However, this technology relies heavily on strong communication conditions and requires pre-established communication lines, resulting in high costs.

[0004] There are also technologies for controlling small hydropower stations under weak communication conditions, proposing an emergency control strategy of centralized decision-making + on-site control to achieve the transition from grid connection to isolated grid at the moment of failure. However, it does not consider the stable operation of the microgrid system for a period of time after the isolated grid.

[0005] Existing technologies for mountainous power grids containing small hydropower stations establish communication between hydropower controllers, grid-connected switches, and dispatching EMS master stations. This allows for the collection of data such as hydropower unit power. Hydropower units can also receive instructions from the dispatching EMS system to regulate hydropower startup and shutdown, as well as output. However, this technology relies heavily on strong communication conditions and requires pre-established communication lines, resulting in high costs.

[0006] There are also technologies for controlling small hydropower stations under weak communication conditions, proposing an emergency control strategy of centralized decision-making + on-site control to achieve the transition from grid connection to isolated grid at the moment of failure. However, it does not consider the stable operation of the microgrid system for a period of time after the isolated grid. Summary of the Invention

[0007] In response to the above problems, the present invention proposes a method for controlling a hydro-solar-storage microgrid in mountainous areas under weak communication conditions, which not only reduces the initial investment cost of the microgrid, but also maintains the normal operation of the microgrid system after being off-grid, thereby ensuring the power supply reliability of local residents.

[0008] The present invention is achieved through at least one of the following technical solutions.

[0009] A method for controlling a hydro-photovoltaic-storage microgrid under weak communication conditions comprises the following steps:

[0010] Step 1: The hydropower unit controller receives historical local load power data sent from the substation; it processes the data to predict the load value for the day;

[0011] Step 2: Install a photovoltaic auxiliary test unit in an area around the hydropower station that is not blocked by sunlight, obtain the maximum power of the auxiliary test unit under the current working conditions, and establish communication between the photovoltaic auxiliary test unit and the small hydropower station to transmit its maximum power to the hydropower unit controller;

[0012] Step 3: The hydropower unit controller estimates the power generation of the photovoltaic power station in the substation based on the power generation data of the photovoltaic auxiliary test unit;

[0013] Step 4: The small hydropower station calculates and updates the current power generation reference value of the small hydropower unit based on the current estimated photovoltaic power generation and the predicted local load data;

[0014] Step 5: The microgrid controller in the substation collects the voltage, current and system frequency data of the current microgrid system. The voltage, current and system frequency data are refreshed and recorded at intervals.

[0015] Step 6: Regulate the power balance of the microgrid system through the centralized energy storage power station and the photovoltaic power station to ensure the stable operation of the microgrid system;

[0016] Step 7: The microgrid controller in the substation collects the load power data of the current microgrid system, refreshes the power data once at intervals and records it, and transmits the recorded local load power data of the day to the hydropower unit controller.

[0017] Furthermore, in step 1, the load value of the day is predicted by processing the transmitted historical local load power data, including the following steps:

[0018] The first step is to fit the load waveform of the day based on the load waveforms of the previous seven days. The waveform of the day is most similar to the waveform of the past seven days, so the waveform of the past seven days accounts for the largest proportion of the predicted waveform of the day. The waveforms of the remaining days are less similar and account for a smaller proportion.

[0019] The second step is to correct the load amplitude of the previous day to predict the load amplitude of the current day because the weather and temperature of the previous day are closest to those of the current day.

[0020] Furthermore, the photovoltaic auxiliary test unit adopts maximum power point tracking control, and obtains the maximum power P of the photovoltaic auxiliary test unit at the current moment every 15 minutes. m (k) and transmit the data to the hydropower unit controller via optical fiber communication;

[0021] The subscript m represents the maximum power point of the photovoltaic auxiliary test unit, k represents the specific time, and the value of k is between [1-96].

[0022] Furthermore, the estimation process of step 3 is as follows: considering that the operating conditions of the photovoltaic arrays in the same area are approximately the same and the maximum power operating points of the single auxiliary test units are approximately the same, the approximate coefficient d(k) is taken, and the power of the photovoltaic power station in the area is estimated based on the number of units N in the photovoltaic power station in the area:

[0023] P pvmax (k)=d(k)*N*P m (k)

[0024] Among them, P pvmax (k) represents the power generation of the photovoltaic power station in the substation, and k represents the specific time; d(k) is taken according to the specific time, and the value range is [0.85-1.15]. m (k) represents the maximum power of the photovoltaic auxiliary test unit at the current moment.

[0025] Furthermore, the current reference value of the generated power of the hydropower unit calculated in step 4 is:

[0026] P hdref (k) = P i (k)-P pvmax (k)

[0027] Among them, P hdref (k) is the reference value of the power generation of the small hydropower station at the kth moment, P i (k) is the load value predicted for the day, i refers to the day, k refers to the specific time, P pvmax (k) represents the power generation capacity of the photovoltaic power station in the substation.

[0028] Furthermore, in step 4, the reference value of the generated power of the small hydropower station at the [1-96]th time point on the day is calculated, and the reference value criterion of the generated power of the small hydropower unit is updated to:

[0029] When |P hdref (k+1)-P hdref (k)|≤5% P hdref (k), P hdref (k) Assign a value to P hdref (k+1), that is, to keep the reference value of the small hydropower unit's power generation consistent with that of the previous moment;

[0030] When |P hdref (k + 1)-P hdref (k)| > 5% P hdref (k), then update the reference value of the power generation power of the small hydropower unit according to the calculation result of P hdref (k + 1);

[0031] Among them, P hdref (k + 1) is the reference value of the power generation power of the small hydropower station at the (k + 1)-th moment.

[0032] Furthermore, in step 5, the microgrid controller in the area collects the voltage, current and system frequency data of the current microgrid system at a sampling frequency of 1200 Hz, and the voltage, current and system frequency data are refreshed and recorded every 1 s.

[0033] Furthermore, in step 6, power balance adjustment is carried out through the centralized energy storage power station and the photovoltaic power station, specifically including:

[0034] When 49.8 < f < 50.2 Hz, the microgrid system maintains the current operating state, where f represents the frequency of the microgrid system;

[0035] When f ≥ 50.2 Hz and df / dt > 0, adjust the operating state of the photovoltaic power station, adjust from the maximum power operation to the reduced power operation, and then the centralized energy storage power station is used as the balance node for power balance adjustment;

[0036] When f ≥ 50.2 Hz and df / dt ≤ 0, the centralized energy storage power station is used as the balance node for power balance adjustment;

[0037] When f ≤ 49.8 Hz and df / dt ≤ 0, first judge the current operating state of the photovoltaic. If it is in the reduced power operation, switch to the maximum power operation, and then the centralized energy storage power station is used as the balance node for power balance adjustment;

[0038] When f ≤ 49.8 Hz and df / dt > 0, the centralized energy storage power station is used as the balance node for power balance adjustment.

[0039] Furthermore, in step 6, the specific steps for power balance adjustment through the photovoltaic power station to adjust the photovoltaic power station from the maximum power operation to the reduced power operation are:

[0040] Since the photovoltaic initially operates at the maximum power point, collect the current maximum power point voltage U m and record it. When it is necessary to adjust from the maximum power operation state to the reduced power operation, set the reference voltage of the photovoltaic controller to U ref as: U ref = U m -ΔU, where ΔU = Um / T, T is the constant voltage reduction coefficient, which is a positive integer.

[0041] Furthermore, in step 7, the microgrid controller in the substation collects power data of the current microgrid system at a sampling frequency of 1200 Hz, refreshes and records the power data every 15 minutes, and transmits the recorded local load power data of the day to the hydropower unit controller.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The present invention can reduce the initial investment cost of microgrid communication in mountainous areas and ensure the stable operation of the microgrid system under weak communication with substation equipment.

[0044] 2. This invention proposes a load forecasting method that uses load data from the past seven days to predict the current day's load value. This historical load data is transmitted via existing communication networks, enabling efficient data delivery even under weak signal conditions. In extreme situations, such as natural disasters or communication system failures, a contingency plan for manual data transmission can be implemented to ensure effective data delivery. This enhances the robustness of data transmission under limited communication conditions, providing a reliable and efficient load forecasting tool for small hydropower units.

[0045] 3. This invention uses power generation data from photovoltaic auxiliary test units to estimate the output power of local photovoltaic power plants and adjust the power generation of local small hydropower stations. This effectively alleviates the coordination issues of hydropower-storage microgrids under weak or no communication conditions. Through reasonable regulation, if the main grid line is disconnected due to a fault, the microgrid system can promptly restore power supply, ensuring the reliability of power supply for local residents. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a structural diagram of the water-photovoltaic-storage microgrid system in an embodiment;

[0047] Figure 2 This is a flow chart of the control of the water-photovoltaic-storage microgrid system in the embodiment;

[0048] Figure 3 Schematic diagram of the photovoltaic power station grid-connected control strategy in an embodiment. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0050] The microgrid system of this embodiment consists of a small hydropower station, a photovoltaic power station, a centralized energy storage power station, a local load, a substation microgrid controller, a dummy load, etc. The structure diagram of the hydro-photovoltaic-storage microgrid system is shown in FIG. Figure 1 As shown. Considering that small hydropower stations are generally located in remote mountainous areas, they experience weak communication conditions with the local microgrid controller, such as no communication, communication delays, and communication failures. However, other devices, due to their proximity to the local microgrid controller, experience strong communication conditions with the load side. This embodiment addresses the issue of weak communication with the local microgrid controller by installing a photovoltaic auxiliary test unit on the roof of the small hydropower station or in an unobstructed area around the small hydropower station to predict the generated power of the local photovoltaic station. Figure 2 Shown is the control flow chart of this embodiment.

[0051] A method for controlling a hydro-photovoltaic-storage microgrid under weak communication conditions in this embodiment includes the following steps:

[0052] Step 1: The hydropower unit controller receives the local load power data for the past seven days from the substation. It processes the data from the previous seven days to predict the current day's load value. Taking into account communication delays and obtaining complete load data for the day, it allows for batch transmission when communication conditions permit, ensuring that data is not lost due to communication interruptions. In extreme cases, such as natural disasters or communication system failures, a contingency plan for manual data transmission is implemented to ensure that data can be delivered safely.

[0053] The hydropower unit controller uses an STM32 as the main controller. It communicates with the substation microgrid controller, regulates hydropower output, and automatically starts and stops the unit based on water level fluctuations. Considering communication latency and obtaining complete load data for a day, data is transferred in batches when communication conditions permit, ensuring data is not lost due to communication interruptions. In extreme cases, such as natural disasters or communication system failures, a contingency plan for manual data transfer ensures safe data delivery.

[0054] The load data received by the hydropower unit controller for the past seven days is shown in Table 1 below. Taking into account the time limit of hydropower regulation and reducing the regulation frequency of small hydropower, one load point is calculated every 15 minutes, which means there are 96 data points in 24 hours.

[0055] Table 1 Local load power data for the past seven days

[0056]

[0057] In the above table, P i-7 (k) represents the load data within the i-7th day, k represents the specific time. Since a load point is collected every 15 minutes, there are 96 data points in 24 hours a day, and the value of k is between [1-96]; Pi-6 (k) represents the load data within the first 6 days; P i-5 (k) represents the load data within the first 5 days; P i-4 (k) represents the load data within the first 4 days; P i-3 (k) represents the load data within the first 1-3 days; P i-2 (k) represents the load data within the first 2 days; P i-1 (k) represents the load data of day i-1.

[0058] The load value for the current day is predicted by processing the load data of the previous seven days. The prediction method consists of two steps:

[0059] The first step is to fit the load waveform of the current day based on the load waveforms of the previous seven days. The waveform of the current day is most similar to the waveform of the previous seventh day, so the waveform of the previous seventh day accounts for the largest proportion of the waveform of the current day, and the waveforms of the remaining days account for a slightly smaller proportion. The fitting method is as follows:

[0060]

[0061] Among them, P i,1 (k) represents the load data of the i-th day, i.e., the load data predicted by the first step on that day. Since the waveform of the seventh day in the past is most similar to the waveform of that day and accounts for the largest proportion of the waveform of that day, as an embodiment, the proportion is taken as 0.7. The waveform similarity of the remaining days is relatively small, and the value is 0.05.

[0062] Step 2: Since the weather and temperature of the previous day are closest to those of the current day, the load amplitude of the previous day is used to correct the load amplitude of the current day. The correction method is as follows:

[0063] when When , keep the prediction result of the first step unchanged, that is:

[0064] P i (k) = P i,1 (k)

[0065] P i (k) represents the final load data predicted on the i-th day;

[0066] when When , the prediction result of the first step is updated, and the final load data after the update is:

[0067] Step 2: Install a PV auxiliary test unit on the roof of the small hydropower station or in an unobstructed area around the station. Set the PV auxiliary test unit to operate in maximum power mode and transmit the output power of the PV auxiliary test unit to the small hydropower unit controller via fiber optic communication every 15 minutes. Since the PV auxiliary test unit operates in maximum power mode, the output power is the maximum power under the current operating conditions.

[0068] As an embodiment, the photovoltaic auxiliary test unit includes multiple photovoltaic cells, obtains the maximum power of the auxiliary test unit under the current working conditions, and transmits the maximum power to the hydropower unit controller by establishing a communication connection between the photovoltaic auxiliary test unit and the small hydropower station.

[0069] Step 3: The hydropower unit controller estimates the power generation of the photovoltaic power station in the substation based on the power data of the auxiliary test unit. The estimation process is as follows: considering that the operating conditions of the photovoltaic arrays in the same substation are approximately the same, and the maximum power operating point of a single auxiliary test unit is approximately the same, the approximate coefficient d(k) is taken, and the power P of the photovoltaic power station in the substation is estimated based on the number of units N in the substation. pvmax (k) is:

[0070] P pvmax (k)=d(k)*N*P m (k)

[0071] Wherein, d(k) can be set according to the specific time. In this embodiment, the value range is [0.85-1.15];

[0072] P m (k) represents the output power of the photovoltaic auxiliary test unit, where m represents the maximum power point, k represents the specific time, and the value of k is between [1-96].

[0073] Step 4: The small hydropower station is based on the current estimated photovoltaic power generation P pvmax (k) and the local load data P predicted in step 1 i (k) Update the current power reference value P of the small hydropower station hdref (k), the update formula is:

[0074] P hdref (k) = P i (k)-P pvmax (k)

[0075] Among them, P hdref (k) is the reference value of the generated power of the small hydropower station at the kth moment, and k refers to the specific moment.

[0076] However, considering the wear of the small hydropower unit caused by frequent regulation, the number of regulations should be reduced, and the reference value criterion for the power generation power of the small hydropower unit is updated to:

[0077] When |P hdref (k + 1)-P hdref (k)| ≤ 5% P hdref (k), assign P hdref (k) to P hdref (k + 1), that is, keep the reference value of the power generation power of the small hydropower unit consistent with the previous moment.

[0078] When |P hdref (k + 1)-P hdref (k)| > 5% P hdref (k), then update the reference value of the power generation power of the small hydropower unit according to the calculation result of P hdref (k + 1).

[0079] Among them, P hdref (k + 1) is the reference value of the power generation power of the small hydropower station at the (k + 1)-th moment.

[0080] Step 5: The microgrid controller in the distribution area collects the voltage, current, and system frequency data of the current microgrid system at a sampling frequency of 1200 Hz, and the voltage, current, and system frequency data are refreshed and recorded every 1 s.

[0081] The microgrid controller in the distribution area has relatively high performance requirements for the microgrid controller. Currently, the all-programmable system-on-chip ZYNQ of Xilinx Corporation is adopted. The microgrid controller is connected to the dispatching master station at the upper end and accesses devices such as the hydropower controller, photovoltaic controller, and energy storage controller at the lower end. By collecting the data (voltage, current, power, status, etc.) of the lower-end devices, the microgrid status perception is realized, and mode management, switching, and other controls are carried out according to the preset operation mode.

[0082] Step 6: Adjust the power balance of the microgrid system through the centralized energy storage power station and the photovoltaic power station to ensure the stable operation of the microgrid system.

[0083] The power balance adjustment is carried out through the centralized energy storage power station and the photovoltaic power station, specifically including:

[0084] When 49.8 < f < 50.2 Hz, the microgrid system maintains the current operating state. f is the system frequency.

[0085] When f ≥ 50.2 Hz and df / dt > 0, adjust the operating state of the photovoltaic power station, adjust from the maximum power operation to the power reduction operation, and then use the centralized energy storage power station as the balancing node to carry out power balance adjustment;

[0086] When f≥50.2Hz and df / dt≤0, the centralized energy storage power station acts as the balancing node to perform power balancing adjustment.

[0087] When f≤49.8Hz and df / dt≤0, the current operating state of the photovoltaic system is first determined. If it is in reduced power operation, it is switched to maximum power operation. Then, the centralized energy storage power station is used as a balancing node to perform power balancing adjustment.

[0088] When f≤49.8Hz and df / dt>0, the centralized energy storage power station acts as the balancing node to perform power balancing adjustment.

[0089] The specific steps for adjusting the power balance of the photovoltaic power station from maximum power operation to reduced power operation are as follows:

[0090] Since the photovoltaic initialization is set to the maximum power operation state, the current working voltage is collected as the maximum power point voltage U m And record, when it is necessary to adjust the maximum power operation state to the reduced power operation state, switch the reference voltage signal of the voltage loop of the photovoltaic controller to U ref =U m -ΔU.

[0091] Where ΔU=U m / T, T is a constant voltage reduction coefficient, which is a positive integer. As an embodiment, T is set to 20.

[0092] Photovoltaic system control block diagram Figure 3 The PV power station operates in two modes: maximum power control and reduced power control. The PV power station's operating mode is switched based on the frequency and frequency variation, and a voltage reference signal is output. This signal is then passed through the voltage loop, current loop, and SPWM to output the grid-connected control signal.

[0093] The weak communication with the microgrid controller mentioned in this embodiment specifically refers to the fact that small hydropower currently uses communication methods with long transmission delays, such as 4G, carrier, and LoRa. Currently, there are few fiber optic channels, and the communication signal is weak, which is prone to communication delays and interruptions. In this embodiment, weak communication can specifically refer to communication methods with long transmission delays, such as 4G, carrier, or LoRa. It can also refer to a contingency plan where communication is blocked and data transmission is completely manual.

[0094] Step 7: The microgrid controller in the substation collects the load power data of the current microgrid system. The power data is refreshed and recorded every 15 minutes, and the recorded local load power data for the day is transmitted to the hydropower unit controller.

[0095] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for controlling a water-solar-storage microgrid under weak communication conditions, characterized in that: It includes the following steps: Step 1: The hydro-generator unit controller receives the local load power data of the past seven days sent by the distribution area; predicts the load value of the current day by processing the data of the previous seven days; considering communication delay and obtaining complete load data within a day, when the communication condition is poor, it allows batch transmission of data when conditions permit to ensure that data will not be lost due to communication interruption; in extreme cases, through an emergency plan of manual data transfer, ensure that the data can be safely delivered; Step 2: Install a photovoltaic auxiliary test unit on the roof of the small hydropower station or in an area without sunlight obstruction around the small hydropower station, set the photovoltaic auxiliary test unit to operate in the maximum power mode, and transmit the maximum power to the hydro-generator unit controller by establishing a communication link between the photovoltaic auxiliary test unit and the small hydropower station; Step 3: The hydropower unit controller estimates the power generation of the photovoltaic power station in the substation based on the power data of the auxiliary test unit. The estimation process is as follows: considering that the working conditions of the photovoltaic arrays in the same substation are approximately the same, the maximum power operating point of a single auxiliary test unit is approximately the same, and the approximate coefficient d(k) is taken. The power P of the photovoltaic power station in the substation is estimated based on the number of units N in the substation. pvmax (k): P pvmax (k)=d(k)*N*P m (k) Among them, P pvmax (k) represents the power generation of the photovoltaic power station in the substation, k represents the specific time, N represents the number of units of the photovoltaic power station in the substation; d(k) is taken according to the specific time, and the value range is [0.85-1.15], P m (k) represents the maximum power of the photovoltaic auxiliary test unit at the current moment; Step 4: The small hydropower station updates the current power generation reference value P of the small hydropower station based on the current estimated photovoltaic power generation and the local load data predicted in step 1. hdref (k): When |P hdref (k+1)-P hdref (k)|≤5%P hdref (k), P hdref (k) Assign a value to P hdref (k+1), that is, to keep the reference value of the small hydropower unit's power generation consistent with that of the previous moment; When |P hdref (k+1)-P hdref (k)|>5%P hdref (k), then according to P hdref The calculation result of (k+1) updates the reference value of small hydropower unit power generation, where P hdref (k+1) is the reference value of the generated power of the small hydropower station at the k+1th moment; Step 5: The microgrid controller in the distribution area collects the voltage, current and system frequency data of the current microgrid system, and refreshes and records the voltage, current and system frequency data once every interval time; Step 6: Adjust the power balance of the microgrid system through the centralized energy storage power station and the photovoltaic power station to ensure the stable operation of the microgrid system; Step 7: The microgrid controller in the distribution area collects the load power data of the current microgrid system, refreshes and records the power data once every interval time, and transmits the recorded local load power data within the current day to the hydro-generator unit controller through a communication link or manually.

2. The method for controlling a water-solar-storage microgrid under weak communication conditions according to claim 1, characterized in that: In Step 1, predicting the load value of the current day by processing the transmitted historical local load power data includes the following steps: The first step: Fit the load waveform of the current day according to the load waveforms within the previous seven days. Among them, the waveform of the current day is most similar to the waveform of the seventh day in the past, so the waveform of the seventh day in the past accounts for the largest proportion in the predicted waveform of the current day, and the waveform similarities of the other days are small and the proportions are small; The second step: Since the weather and temperature of the day adjacent to the current day are closest to those of the current day, the load amplitude of the current day is predicted by correcting with the load amplitude of the previous day.

3. The method for controlling a water-solar-storage microgrid under weak communication conditions according to claim 1, characterized in that: The photovoltaic auxiliary test unit adopts maximum power point tracking control, and obtains the maximum power P of the photovoltaic auxiliary test unit at the current moment every 15 minutes. m (k) and transmit the data to the hydropower unit controller via optical fiber communication; Where the subscript m represents the maximum power point of the photovoltaic auxiliary test unit, k represents a specific moment, and the value of k is between [1 - 96].

4. The method for controlling a water-solar-storage microgrid under weak communication conditions according to claim 1, characterized in that: [[ID=,10]]The calculation of the current power reference value of the hydro-generator unit in Step 4 is: P hdref (k)=P i (k)-P pvmax (k) Among them, P hdref (k) is the reference value of the power generation of the small hydropower station at the kth moment, P i (k) is the load value predicted for the day, i refers to the day, k refers to the specific time, P pvmax (k) represents the power generation capacity of the photovoltaic power station in the substation.

5. The method for controlling a water-solar-storage microgrid under weak communication conditions according to claim 1, characterized in that: In Step 5, the microgrid controller in the distribution area collects the voltage, current and system frequency data of the current microgrid system at a sampling frequency of 1200 Hz, and refreshes and records the voltage, current and system frequency data every 1 s.

6. The method for controlling a water-solar-storage microgrid under weak communication conditions according to claim 1, characterized in that: In Step 6, the power balance adjustment is carried out through the centralized energy storage power station and the photovoltaic power station, specifically including: When 49.8 < f < 50.2 Hz, the microgrid system maintains its current operating state, where f represents the frequency of the microgrid system; When f ≥ 50.2 Hz and df / dt > 0, adjust the operating state of the photovoltaic power station from maximum power operation to reduced power operation, and then the centralized energy storage power station serves as a balancing node for power balance adjustment; When f ≥ 50.2 Hz and df / dt ≤ 0, the centralized energy storage power station serves as a balancing node for power balance adjustment; When f≤49.8Hz and df / dt≤0, the current operating state of the photovoltaic system is first determined. If it is in reduced power operation, it is switched to maximum power operation. Then, the centralized energy storage power station acts as a balancing node to perform power balancing adjustment. When f≤49.8Hz and df / dt>0, the centralized energy storage power station acts as the balancing node to perform power balancing adjustment.

7. The method for controlling a water-solar-storage microgrid under weak communication conditions according to claim 1, characterized in that: In step 6, the specific steps for adjusting the power balance of the photovoltaic power station from maximum power operation to reduced power operation are as follows: Since the photovoltaic system initially operates at the maximum power point, the current maximum power point voltage U is collected. m And record, when it is necessary to adjust the operation state from the maximum power to the reduced power operation, set the reference voltage of the photovoltaic controller to U ref For: U ref =U m -ΔU, where ΔU = U m / T, T is the constant voltage reduction coefficient, which is a positive integer.

8. The method for controlling a water-solar-storage microgrid under weak communication conditions according to claim 1, characterized in that: In step 7, the microgrid controller in the substation collects the power data of the current microgrid system at a sampling frequency of 1200 Hz, refreshes the power data every 15 minutes and records it, and transmits the recorded local load power data of the day to the hydropower unit controller using a communication link or manual method.

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